Mechanics, Materials Science & Engineering

Mechanics, Materials Science & Engineering, December 2016 – ISSN 2412-5954

MMSE Journal. Open Access www.mmse.xyz

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Sankt Lorenzen 36, 8715, Sankt Lorenzen, Austria

Mechanics, Materials Science & Engineering Journal

December 2016


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Mechanics, Materials Sciences & Engineering Journal, Austria, Sankt Lorenzen, 2016

Mechanics, Materials Science & Engineering Journal (MMSE Journal) is journal that deals in peerreviewed, open access publishing, focusing on wide range of subject areas, including economics, business, social sciences, engineering etc.

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Editor-in-Chief Mr. Peter Zisser Dr. Zheng Li, University of Bridgeport, USA Prof. Kravets Victor, Ukraine Ph.D., Shuming Chen, College of Automotive Engineering, China Dr. Yang Yu, University of Technology Sydney, Australia Prof. Amelia Carolina Sparavigna, Politecnico di Torino, Italy ISSN 2412-5954

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e-ISSN 2414-6935

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Engineering

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(Magnolithe

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Support: [email protected] ©2016, Magnolithe GmbH © Published by Magnolithe GmbH. This is an open access journal under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/


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CONTENT I. Materials Science MMSE Journal Vol. 7 ..................................................................................... 6 An Effective Way of Obtaining Bainite Structure in Alloyed High-Strength Cast Irons. R.K. Hasanli ........................................................................................................................................ 7 Laser Metal Deposition Repair Applications for Ti-6Al-4V Alloy. L. Jyothish Kumar, C.G. Krishnadas Nair ........................................................................................................................ 13 Statistical Study of Corrosion Types in Constructions in South Region of Rio De Janeiro Brazil. Carolina Lacerda da Cruz, Thalita Gonçalves de Lima, Nilo Antônio S. Sampaio, José Wilson de Jesus Silva ..................................................................................................................................... 23 Influence of the Composition of (TlGaS2)1-х(TlInSe2)x Alloys on Their Physical Properties. Mustafaeva S.N., Jafarova S.G., Kerimova E.M., Gasanov N.Z., Asadov S.M. ................................ 33 Enhancement of Optical and Thermal Properties of γ- Glycine Single Crystal: in the Presence of 2-Aminopyridine Potassium Chloride. R. Srineevasan, D. Sivavishnu, K. Arunadevi, R. Tamilselvi, J. Johnson, S. M. Ravi Kumar .................................................................................... 39 Enhanced Mechanical Performance for Nacre-Inspired Polyimine Composites with Calcium Carbonate Particles. Si Zhang, Yanting Lv, Jiayi Li, Song Liang, Zhenning Liu ........................... 52 Study on Laser Welding Process Monitoring Method. Heeshin Knag ................................... 61 II. MECHANICAL ENGINEERING & PHYSICS MMSE JOURNAL VOL. 7 .......................................... 67 Determining Optimum Location Places for Clutch Couplings in Hydrostatic and Mechanical Transmissions of Wheeled Tractors. Taran I.O., Bondarenko A.I................................................. 68 The Evaluation of Torsional Strength in Reinforced Concrete Beam. Mohammad Rashidi, Hana Takhtfiroozeh............................................................................................................................ 75 Process Modeling for Energy Usage in “Smart House” System with a Help of Markov Discrete Chain. Victor Kravets, Vladimir Kravets, Olexiy Burov ................................................... 84 Statistical Control of the Technological Process Stability to Manufacturing Cylindrical Parts into High Series. Viorel-Mihai Nani ................................................................................................ 96 Analysis of the Time Increment for the Diffusion Equation with Time-Varying Heat Source from the Boundary Element Method. Roberto Pettres ............................................................... 110 Investigation of Energy Absorption in Aluminum Foam Sandwich Panels By Drop Hammer Test: Experimental Results. Mohammad Nouri Damghani, Arash Mohammadzadeh Gonabadi ... 122 Probabilistic Analysis of Wear of Polymer Material used in Medical Implants. T. Goswami, V. Perel ............................................................................................................................................ 141 Mathematical Models of Hybrid Vehicle Powertrain Performance. K.M. Bas, V.V. Kravets, K.A. Ziborov, D.A. Fedoriachenko, V.V. Krivda, S.A. Fedoriachenko ........................................... 153 Optimization of Die-Sinking EDM Process Parameters in Machining OF AMMCDesirability Approach. M. Sangeetha, A. Srinivasulu Reddy, G. Vijaya Kumar ......................... 164 Analytical and Numerical Study of Foam-Filled Corrugated Core Sandwich Panels under Low Velocity Impact. Mohammad Nouri Damghani, Arash Mohammadzadeh Gonabadi .......... 175 Various Comparison of Additional Conditions of Different Designed Thermal Solar Technology Systems with the Same Collector Field. Kenan Karacavuş .................................... 200 III. MACHINE BUILDING MMSE JOURNAL VOL. 7........................................................................ 208 Conceptual Model of “Lapwing” Amphibious Aircraft. Iftikhar B. Abbasov, V’iacheslav V. Orekhov ...................................................................................................................................... 209 MMSE Journal. Open Access www.mmse.xyz

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VIII. ECONOMICS & MANAGEMENT MMSE JOURNAL VOL. 7 .................................................... 222 Cost Reduction of Taxi Enterprises at the Expense of Automobile Fleet Optimization. Novytskyi А.V. 1, Melnikova Yu. I. .................................................................................................. 223 Factor Analysis of Passenger Cars Using as a Taxi. Deriugin O.V.1, Novikova О.О.1, Cheberyachko S.І ............................................................................................................................ 230 Mathematical Models Concerning Location of Vehicular Gas-Filling Stations within Cities. Kuznetsov A.P. ................................................................................................................................. 235 IX. PHILOSOPHY OF RESEARCH AND EDUCATION MMSE JOURNAL VOL. 7 ............................... 244 On Communicative Competences as a Satisfactory Solution for Masters in Engineering. K.A. Ziborov, T.A. Pismenkova, S.A. Fedoriachenko, I.V. Verner ................................................. 245 The Use of Online Quizlet.com Resource Tools to Support Native English Speaking Students of Engineering and Medical Departments in Accelerated RFL Teaching and Learning. Kh.E. Ismailova, K. Gleason, E.A. Provotorova, P.G. Matukhin ................................................... 251


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I . M a t e r i a l s S c i e n c e M M S E J o u r n a l V o l . 7


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An Effective Way of Obtaining Bainite Structure in Alloyed High-Strength Cast Irons1 R.K. Hasanli1,a 1 – Associated professor, Dr., Azerbaijan Technical University, Baku, Azerbaijan a – [email protected] DOI 10.13140/RG.2.2.18415.23200

Keywords: high-strength cast iron, globular graphite, economical alloying, mold, heat treatment, isothermal transformations, the details of locking devices, structure, properties.

ABSTRACT. This paper describes the features of the isothermal transformation in high-strength nodular cast iron. It explores the feasibility and effectiveness of obtaining bainite structure in the cast iron economically -alloyed with Nickel, copper and molybdenum cast in metallic form by continuous cooling air.

Introduction. In the coming years, the engineering industry of Azerbaijan should significantly be improved by the quality of the products. The most effective way to solve this problem is development of advanced structural materials, used for manufacturing various parts used in Oil and Gas industry machinery. The use of high-strength cast iron with nodular graphite (ductile iron) instead of alloy steel for producing machine parts is a promising direction of materials science development in mechanical engineering. In accordance with existing manufacturing technology, critical parts of the locking devices of oilfield equipment are produced from alloyed steels and subjected to bulk quenching or normalizing, followed by nitration to provide high wear resistance and toughness. Analyses of the Bainite Structure of High-Strength Cast Irons. For ductile iron, such processing is unsuitable, as parts made from cast iron with volumetric hardening are prone to cracks. Nitrating ductile iron is also impractical due to the significant duration of the process and the fragility of the resulting surface layer [1]. To ensure high wear resistance of parts made from sparingly-alloyed high-strength cast iron there is a possibility of obtaining bainite structure through isothermal treatment or otherwise [2]. It is known that the material with the bainite structure do not inferior in the wear resistance to the nitride layer. It was indicated that the highest wear resistance, cast irons possess lower bainitic structure [3]. The strength of the isothermal heat-treated cast irons is at a high level [2]. Several works are focused on the study of methods employed for obtaining bainitic cast iron [3 7]. Technique to obtain a matrix of bainite in cast iron in the cast state is complex and requires complex alloying additions. This does not guarantee the homogeneity of the structures and have a risk of developing segregation and micro segregation of elements in the iron composition during solidification. © 2016 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/


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For cast irons, obtained by casting in a metal mold, this method is unacceptable, as they must undergo graphitizing annealing [6]. The experiments showed that the introduction of 1.0% Nickel, 0,5% copper and 0,5% molybdenum in the alloy, obtained by casting in the mold, leads to the formation of bainite areas in their structure even at slow (furnace and air), cooling after graphitizing annealing. This complicates the machining of castings and does not eliminate t he need to additional heat treatment [5]. More appropriate for these conditions is the method of obtaining bainite structure in cast iron via isothermal tempering [3]. It enables the formation of bainitic structure without inclusions of perlite and structurally free ferrite. However, this method requires special equipment and additional production space to accommodate the quenching baths. The complexity of the method is also due to maintaining constant bath temperature and high energy costs. For cast iron, cast in the mold, especially doped, it is possible to obtain the metal substrate bainite during continuous cooling [6]. The dopants should increase the stability of austenite in the pearlite region. It is important to understand whether it is possible at conditions of continuous cooling to obtain the bainite structure in cast iron, alloyed with Nickel, copper and molybdenum, and how homogeneous the resulting structure and properties could be. The presence of structural heterogeneity, as well as difference in proportions of phases in the matrix can significantly affect the mechanical properties of the investigated alloys. It is necessary to evaluate the degree of influence of these factors on the level of guaranteed properties of cast irons. Thus, in this work the main task was to establish the possibility of obtaining of bainite structure in alloyed Nickel, copper and molybdenum irons, featured in the metal mold during continuous cooling in air. This treatment can be carried out with the heating higher A Hc1 and higher A cK1 . Apparently, it makes no sense to carry out heating in the inter-critical region, because this can lead to increase in heterogeneity in the matrix of cast iron. In addition, it is important to ensure th e stability of the super cooled austenite in the pearlite region of decay that would be better achieved after heating above A Kc1 . In this regard, studies were chosen temperature from 870 to 930 0C. Isothermal hardening machined alloy and, for comparison, non-alloyed high-strength cast irons with nodular graphite. Samples of unalloyed iron were studied dependence of bainitic structure from the temperature of isothermal holding. At the same time, the objective was to establish a link between the original structure of the matrix and the speed and completeness of bainite transformation. The latter is important in the development of production technologies for the manufacture of castings of parts of the locking devices from ductile iron in single and metallic forms [6-8]. Temperature of austenitization was 9100C that exceeds 500C for the A cK1 investigated alloy. The exposure was 15 min, isotherm temperatures: 350, 400 and 4500C. During quenching, the samples of ferrite and pearlite cast irons were subjected to the same heating in a furnace and simultaneously transferred into the bath. Exposure in the bath was from 30 to 20 hours. After isothermal holding the samples were cooled in water. It is established that at low shutter speeds in the bath, the iron acquires high hardness, due to presence of a significant amount of martensitic, formed during cooling of the samples to the temperature isotherms in the water. The transformation of bainite in ferrite iron initially develops slower than in pearlite, as evidenced by their high hardness (see table 1). It is discovered, that the bainite transformation starts to develop intensively in the cast irons with ferrite initial structure after more than a 10-minute exposure. At temperatures of 3500C and 4000C it almost ends at 15-16 minutes (Fig.1). Cooling bath with a temperature of 3500C leads to the formation MMSE Journal. Open Access www.mmse.xyz

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of lower bainitic (Fig. 1, 2), and a temperature of 400 and 450 0C - top. Fine precipitation of carbides in the structure of samples treated at 450 0C, with the extracts of more than 16 min are clearly visible (Fig. 3-5). Table 1. Hardness (HB) high-strength cast iron, casted in a mold, after isothermal hardening. The temperature of the isothermal quenching, oC

450

400

350

isoth. holding the cast iron

30s

50s

100 s

16m

2h

60s

90s

10m

16m

2h

90s

120s

10m

-

16m

2h

Source structure of cast iron: Pearlite

512 444

340

321

Ferritic

512 512

512

-

-

-

387

375

321

425

402

364

351

351

248 496 496

283

241 187 532

512

340

283

-

a)

b)

c) Fig. 1. The effect of time aging at 350 C for isotherm the structure of ferritic ductile cast iron: а)  isoth=2 min.; b)  isoth=10 min.; c)  isoth=16 min. х800. 0


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a)

b)

c)

d)

Fig. 2. The effect of time aging at 3500C for isotherm the structure of pearlitic ductile cast iron: А)  =2 min.; b)  =10 min.; c)  =16 min.; d)  =2 hours.

a)

b)

c)

d)

Fig. 3. The effect of exposure time with isotherm 4000C on the structure of ferritic ductile cast iron: а)  =1,5 min; b)  =10 min; c -  =16 min.; d)  =2 hours. MMSE Journal. Open Access www.mmse.xyz

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a)

b)

Fig. 4. The effect of exposure time with isotherm 4000C on the structure of pearlite ductile cast iron: а)  =10 min; b)  =10 min.

a)

b)

c) Fig. 5. The influence of exposure time on the isotherm at 4500C the structure of pearlite ductile cast iron: а -  =100 sec.; b -  =16 min.; c -  =2 hours. Studies found that the initial structure of the metallic base of cast iron, cast in the mold, has a significant influence on kinetic parameters of bainite transformation. In the original ferrite matrix, the transformation is quicker and more complete than in pearlite. However, the incubation period in ferrite is more. Summary. Thus, an efficient way of obtaining Manitou patterns in the economically-alloyed iron cast in metal mold by continuously cooled air. The proposed technique provides heat treatment resulting in a rational structure and properties of ductile iron castings for the parts of the locking devices of oilfield equipment.


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References [1] V.V. Dubrov and others, The use of high-strength cast iron in valve. In proc. High-strength cast iron with nodular graphite. Kiyev, Naukova Dumka, 1998, pp. 78-81. [2] A.I. Belyakov, A.A. Belyakov, A.A. Zhukov Isothermal quenching of cast iron with nodular graphite // Blank production in mechanical engineering, 2008, No. 1, pp. 44-48. [3] A.I. Belyakov and others. Production of castings from high-strength nodular cast iron. M., Mechanical engineering, 2010, p. 712. [4] I.N. Bogachev, R.I. Mints Cavitation-erosion fracture of cast iron. Sat. Theory and practice of foundry production, Ural Polytechnic Institute, vol. 89, 1999, pp. 71-78. [5] L.P. Ushakov Wear-resistant cast iron with spheroidal graphite. M., Mechanical engineering, 2005, 153 p. [6] R.K. Hasanli, Structure and properties of ductile iron. Baku, Science, 2013, 250 p. [7] R.K. Hasanli, Peculiarities of structure and phase composition of heat-treated high-strength cast irons with nodular graphite // Journal of mechanical engineering, 2013, No. 10, pp. 31-33. [8] N.W. Ismailov, Features of producing engineering castings, using silica sand and bentonite clay in Azerbaijan // Journal of mechanical engineering 2012, No. 6, pp. 11-14. [9] E.A. Silva, L.F.V.M. Fernandes, N.A.S. Sampaio, R.B. Ribeiro, J.W.J. Silva, M.S.Pereira (2016), A Comparison between Dual Phase Steel and Interstitial Free Steel Due To the Springback Effect. Mechanics, Materials Science & Engineering Journal Vol.4, Magnolithe GmbH, doi: 10.13140/RG.2.1.3749.7205 [10] L. I. Éfron, D. A. Litvinenko (1994), Obtaining high-strength weldable steels with bainite structure using thermomechanical treatment, Metal Science and Heat Treatment, Vol. 36, Is. 10, Springer, doi: 10.1007/BF01398082 Cite the paper R.K. Hasanli (2016). An Effective Way of Obtaining Bainite Structure in Alloyed High-Strength Cast Irons. Mechanics, Materials Science & Engineering, Vol 7. doi:10.13140/RG.2.2.18415.23200


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Laser Metal Deposition Repair Applications for Ti-6Al-4V Alloy2 L. Jyothish Kumar 1, a & C.G. Krishnadas Nair 2 1 – doctoral scholar, Jain University, Bangalore – 560078 2 – professor, research superviser, Chancellor, Jain University, Bangalore – 560078 a – [email protected] DOI 10.13140/RG.2.2.35949.38889

Keywords: Laser Metal Deposition, Ti-6Al-4V powder and substrate, Taguchi L9 Orthogonal array method, Process parameters.

ABSTRACT. Laser metal deposition is an additive manufacturing process, which is used to produce functional metal parts or repair existing parts. This paper focuses on deposition of Ti-6Al-4V material for remanufacturing of existing Ti6Al-4V components. Optimization of laser metal deposition process parameters is significant in achieving good metallurgical and mechanical properties such as fine grain structure and bonding strength for aerospace applications. Taguchi’s L9 orthogonal array method has been adopted to optimize the laser power, powder feed rate and scan speed. Analysis of variance (ANOVA) is used to study the effect of process parameters on the deposit and verification trial experiments were conducted to ascertain the optimum process parameters performance. Residual stress measurement results revealed that the residual stress is compressive and significantly higher in optimized test specimen with good bonding strength. The optimized results shown that enhanced properties in refurbishment of aero engine parts using Ti6Al-4V powder material.

Introduction. Laser Metal Deposition (LMD) is an additive manufacturing process, which builds 3 dimensional parts directly from CAD data. A high power laser heat source is used to create a melt pool in the substrate and powder material is fed co-axially in to the melt pool. Due to rapid cooling the molten pool solidification takes place to produce highly dense metal parts with reduced waste of material compared to conventional manufacturing process. [1] LMD is a latest technology, which is used for freeform fabrication and repair of engineering and aerospace components [2]. Kamran shah et.al [3] have studied the effects of process parameters on direct laser metal deposition of IN 718 on Ti-6Al-4V substrate by using pulsed laser heat source parameters. It was found that optimized process parameters like laser power, scanning speed and powder feed rate resulted in crack free deposition with improved mechanical and metallurgical properties. Dinda et al. [4] have investigated microstructure analysis and thermal properties of Inconel 625 process with direct metal deposition. In this study Taguchi L9 orthogonal array method was applied to evaluate the effect of process parameters on the microstructure and mechanical properties of Inconel 625 material. Ryan Cottam et al. [5] studied the laser cladding of Ti-6Al-4V powder to understand the effect of laser cladding parameters on the metallurgical properties of the material. It was observed that microstructure of Ti-6Al-4V deposit in the clad zone with optimized process parameters was refined and contributed to the good deposition strength. Qun-li et al. [6] have studied direct laser metal deposition of Inconel-718 and the effects of process parameters on rate of deposition and layer thickness. It was found that the optimized process parameters lead to directional solidification with fine martensite microstructure and increased microhardness. R. Keshavamurthy et al. [2] have carried out process parameters optimization for direct metal deposition of H13 tool steel by using Taguchi orthogonal array method of design of experiments. The effect of powder feed rate, © 2016 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/


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laser scan speed and laser power on the hardness of the deposit have been studied. It was found that optimum process parameters have contributed to the increased hardness of the deposit and the optimised process parameters were verified from the analysis of variance (ANOVA). Laser Metal Deposition process includes several process parameters such as laser power, scan speed, beam diameter, powder feed rate, hatch spacing, layer thickness and scanning orientation. From the above literature review, it is crucial to optimize these process parameters to achieve the desired quality characteristics of the deposited materials. In view of above, the objective of the current study is to optimize the process parameters of laser metal deposition of Ti-6Al-4V powder on Ti-6Al4V substrate using Taguchi L9 orthogonal array method to achieve maximum hardness and bonding strength. Ti-6Al-4V is having high strength to weight ratio widely used in aerospace applications such as airframe, compressor blades, vanes and discs at elevated temperature. Details of Experiments. Deposition material: Fig.1 shows the scanning electron microscope (SEM) of Ti-6Al-4V powder particles used in the current study. As shown in the Fig.1 the powder particles are spherical in shape and size distribution varies between 44-106 µm and the powders produced by gas atomization process. Fig.2 shows the EDS analysis of elemental composition of Ti-6Al-4V material. Table-1 shows the chemical composition of Ti-6Al-4V powder material used in the present study.

Fig. 1. Scanning electron micrograph of Ti-6Al-4V powder at 2000 X Magnification.

Fig. 2. SEM image and EDAX pattern of elemental composition.


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Table 1. Chemical composition of Ti-6Al-4V powder. Element

C

O

N

H

Fe

Al

V

Ti

Percentage

0.01

0.063

0.02

0.0045

0.21

6.4

4.0

Balance

Substrate material: The substrate material used in the present study is Ti-6Al-4V plate to deposit Ti6Al-4V powder. The chemical composition of Ti-6Al-4V substrate is given in the Table. 2. Table 2. Chemical composition of Ti-6Al-4V substrate. Element

C

Al

Ti

V

Fe

Percentage

0.0590

5.6600

90.2100

3.7200

0.1400

Planning of experiments: Using Taguchi method experiments are planned since it is a robust design method when the process is affected by several process parameters. When compared with traditional methods of experimental planning, Taguchi method helps in reducing number of experiments, cost and time. Taguchi suggested orthogonal array method, which gives different combinations of parameters and their levels for each set of experiment [7, 8]. As per Taguchi orthogonal array method complete process parameter area is investigated with least number of experiments. Design of experiments using Taguchi L9 Orthogonal array method. In the present study the best potential combination of process parameters have been determined by using Taguchi L9 orthogonal array method. Laser power, scan speed and powder feed rate have been selected as variable input process parameters and higher hardness as the desired output and quality characteristic. L9 orthogonal arrays and signal to noise (S/N) ratio are the two important tools used in Taguchi design of experiments method. The column of L9 orthogonal array represents the process parameters to optimize and the rows represents the levels of each process parameter. The mean and the variance of the output response at every parameter setting in L9 orthogonal array are later combined in to a single performance measure known as S/N ratio and the S/N ratio helps to measure quality characteristics with importance on variation [9, 10]. Minitab software (Version: 17) was used to calculate the S/N ratio using Taguchi method. Input process parameters for laser metal deposition of and their levels are shown in table. 3 and experimental plan based on Taguchi L9 orthogonal array method is shown in table. 4. In the present research work the maximum power efficiency of the Laser Metal Deposition Machine –TRUMPF LASER CELL 1005 is 4000W. We have selected the intermediate Laser Power 2500 W, Scanning Speed 600mm/min and beam dia of 3 mm. From these parameters we have found the energy density energy Ɛd = 83.33 J/mm2 using equation (1) for good quality of deposition, which is in the workable range based on review of literature. 60 × 𝑃

Ɛd = 𝑑 × 𝑉 J/mm2 where P – is the laser power; V – is the scanning speed or velocity; D – is the laser beam diameter [11].


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(1)


Using the energy density Ɛd = 83.33 J/mm2 we have designed the experiment using Taguchi’s L9 Orthogonal Array with 3 factors and 3 levels. From the design of experiments result we have selected the optimum parameters to build the test specimens. Table 3. Input process parameters and levels. Level Sl No.

Parameters

1

Level 1

Level 2

Level 3

Laser power (W)

2350

2500

2650

2

Laser scan speed (mm/min)

500

600

700

3

Powder feed rate (g/min)

3

4

5

Table 4. Experimental plan based on Taguchi L9 orthogonal array. Expt. No.

Powder Feed Rate (g/min)

Laser Power (W)

Scan Speed (mm/min)

1

4

2350

600

2

4

2500

700

3

4

2650

500

4

3

2350

500

5

3

2500

600

6

3

2650

700

7

5

2350

700

8

5

2500

500

9

5

2650

600

Laser Metal Deposition. Laser Metal Deposition of Ti-6Al-4V on Ti-6Al-4V substrate was carried out using TRUMPF LASER CELL LMD system with 4000W CO2 laser with laser beam diameter of 3mm. The deposition was carried out in argon-controlled atmosphere to avoid oxidation. Test specimens were prepared with two layer depositions with 1.2 mm layer thickness and 10 x 30 mm size as shown in Fig.3.


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Fig. 3. Ti-6Al-4V deposition on Ti-6Al-4V substrate as per L9 orthogonal array. After deposition the samples were held in a fixture on SODICK A350 Mark 21 submerge type wire electric discharge machine (EDM) and cut in transverse direction using brass wire (dia 25µm) as a tool electrode. The sectioned samples were polished with three coarse grits (600, 800 and 1200) and final polishing media with 0.05 microns alumina powder. The polished Ti-6Al-4V samples were etched using a mixture of 8 gms KoH (Potassium Hydroxide), 10 ml H2O2 (Hydrogen Peroxide), 60 ml distilled water and it is immersed for about 20 seconds to reveal the microstructure details. Microstructure studies were carried out on metallographically polished surfaces using optical microscope of make: Nikon, Japan and model: Eclipse LV 150. Microhardness tests were conducted using Vickers microhardness tester of make: CLEMEX, Canada and the indentation was measured using CLEMEX vision PE image analyzer software. Indentations were made at 5 locations on the substrate and deposit from the interface, using a load of 100 gms for duration of 10 seconds. Hardness value of each sample is a result of the average of all five measured readings. Results and discussions. Microstructure: Fig.4 shows the microstructure of Ti-6Al-4V deposit on Ti-6Al-4V substrate. The microstructural analysis is the function of combined effect of laser power, scan speed and powder feed rate, which is depicted by using the series of optical microscope images as shown in the Fig. 4. All the images are viewed at 200X magnification. It is observed that the microstructure comprises of combination of acicular α phase (martensite) and Widmanstatten structure. Sample 7 shows that the amount of acicular α phase is more when compared to other images, which have resulted from higher, scan speed; powder feed rate and less laser power. Further, the sample 7 exhibited more hardness as reported in table. 6 due to rapid cooling of the melt pool, which resulted in formation of acicular α, phase and in general produces the α martensite microstructure [12]. This combination is imparting the better cooling effect to have acicular α phase (martensite phase). Further, all the sample reveals least porosities and no evident cracks or incoherence exists. Hardness. Table. 5 shows the hardness values of Ti-6Al-4V deposit. The minimum and maximum hardness of the samples obtained are 407.12 and 459.54 HV for the experimental samples 7 & 3 correspondingly. The fine grain size and minimum porosity attributes to the higher hardness and strength of the material. The presence of interstitial atoms and the density dislocations decides the free plastic deformation of the material, thereby improving the resistance to plastic deformation, which leads to higher hardness. [2, 13]. Analysis of S/N ratio. In the current study, hardness was considered as the quality characteristic for laser metal deposition technology. Higher value of hardness is suitable for deposition of Ti-6Al-4V; therefore, the concept of “larger-the-better” is adopted for optimization of process parameters by Taguchi L9 orthogonal array method.


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Table 5. Hardness and S/N values for Taguchi L9 experiments. Expt. No.

Microhardness (HV)

S/N ratio

1

407.12

52.1944

2

436.27

52.7951

3

413.47

52.3289

4

420.80

52.4815

5

410.39

52.2639

6

442.11

52.9106

7

459.54

53.2465

8

436.04

52.7905

9

434.22

52.7542

As shown in the above table the best performance of the process is indicated by a higher value of S/N (Larger is better). Hence, the optimum level of the process parameters is the level of the highest S/N value.


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Fig. 4. Optical micrographs of Ti-6Al-4V deposits as per Taguchi’s L9 orthogonal array. (1) 2350 W, 600 mm/min, 4 g/min; (2) 2500 W, 700 mm/min, 4 g/min; (3) 2650 W, 500 mm/min, 4 g/min; (4) 2350 W, 500 mm/min, 3 g/min; (5) 2500 W, 600 mm/min, 3 g/min; (6) 2650 W, 700 mm/min, 3 g/min; (7) 2350 W, 700 mm/min, 5 g/min; (8) 2350 W, 500 mm/min, 5 g/min; (9) 2650 W, 600mm/min, 5 g/min. Powder feed rate. The effect of powder feed rate on hardness is attributed from the Fig.5 that the S/N ratio is decreasing with increase in powder feed rate up to 4 g/min and then S/N ratio is increasing with the further increase in powder feed rate at 5 g/min. Hence the optimum powder feed rate is 5 g/min. Laser power. The effect of laser power on hardness is as shown in the Fig5. It is observed that the S/N ratio is increasing with increase in laser power. This shows that the optimum laser power is 2650 W. Scanning speed. The effect of laser scanning speed on hardness is shown in the Fig.5. It is observed that S/N ratio is increasing with increase in scanning speed. This shows that the optimum scan speed is 700 mm/min. Based on the analysis of the S/N ratio, the optimized process parameters for achieving maximum hardness are powder feed rate: 5 g/min, laser power: 2650 W, Laser scanning speed: 700 mm/min.

Main Effects Plot (data means) for SN ratios Powder feed rate (g/min)

53.0

Laser power (W)

Mean of SN ratios

52.8 52.6 52.4 3 53.0

4

5

2350

2500

Scanning speed (mm/min)

52.8 52.6 52.4 500

600

700

Signal-to-noise: Larger is better

Fig. 5. Main Effects Plot for SN ratios. MMSE Journal. Open Access www.mmse.xyz

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2650


Analysis of Variance (ANOVA). The process parameters importance has been studied by analysis of variance for S/N ratio. Based on analysis of variance, each parameter contribution has been quantified under column F of Table. 6. From table 6 it clearly reveals that the F value for scan speed is very high when compared to laser power and powder feed rate. This is a clear indication that the influence of scan speed is significantly larger than the influence of laser power and powder feed rate for achieving higher hardness. Table 6. Analysis of variance for S/N ratio. Source

Degrees of freedom (DOF)

Sum of squares

Mean square

F – ratio (F)

P – ratio (P)

Powder feed rate

2

0.36984

0.19842

61.42

0.016

Laser power

2

0.00346

0.00173

0.54

0.651

Scan speed

2

0.55588

0.27794

86.04

0.011

Error

2

0.00646

0.00323

Total

8

0.96264

Optimized process parameter verification test. A design of experiments verification test has been carried out for laser metal deposition of two layers of Ti6Al4V on Ti6Al4V substrate under optimized process parameters to study the hardness. The obtained deposition hardness under optimized condition is 461.22 HV as shown in table. 7. It is noticed that the hardness value of the optimized condition is considerably higher than that of the deposition experiments carried out corresponding to L9 orthogonal array. The optimized sample was deposited using 2650 W laser power, 700 mm/min scan speed and 5 g/min powder feed rate. It clearly reveals that fine and consistent ‘α martensite’ microstructure may attributes to the higher hardness as shown in Fig. 6. Table 7. Optimized process parameters and Hardness. Expt. No.

Laser Power (W)

Powder flow rate (g/min)

Laser scan speed (mm/min)

Hardness (HV)

1

2650

5

700

461.22

Fig. 6. Optical micrograph of Ti-6Al-4V deposit under optimum process parameter. MMSE Journal. Open Access www.mmse.xyz

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Residual Stresses. Residual stress was measured using X-ray diffraction method. The X-ray diffraction pattern shown in Fig. 7 (a) & (b) reveals the residual stress result of Ti-6Al-4V deposits. Residual stress measurement has carried out on L9 test specimen and optimized test specimen of Ti6Al-4V deposit. It is observed that the residual stress is compressive in both L9 and optimized Ti6Al-4V specimens. The measured residual stress in L9 test specimen is -153.3 ± 21.3 MPa and -277.8 ± 20.2 MPa in optimized test specimen. This shows that the residual stress in optimized Ti-6Al-4V test specimen is significantly higher with good bonding strength.

(a)

(b) Fig. 7. Ti-6Al-4V diffraction pattern (a) L9 test specimen 1 (b) optimized test specimen. Summary. Process parameters for laser metal deposition of Ti-6Al-4V were optimized using Taguchi L9 orthogonal array method. The optimum process parameters are found to be laser power: 2650 W, powder feed rate: 5 g/min and scan speed: 700 mm/min. The optimum process parameters have been confirmed by the verification experiment conducted. X-ray Diffraction residual stress studies clearly reveal that the residual stress is compressive and significantly higher in parts deposited under optimum laser power, laser scan speed and powder feed rate. The obtained results from the optimization of process parameters could be directly used to repair complex aero engine Ti-6Al-4V parts. References [1] Imran M.K., Masood S., Brandt M., Bhattacharya S., Mazumder J., Parametric investigation of diode and CO2 laser in direct metal deposition of H13 tool steel on copper substrate. World Academy of Science and Technology 2011, 79, 437- 442


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[2] R. Keshavamurthy, Padmanav Rashmirathi, A.R. Vinod, C.K. Srinivasa, P.V. Shashikumar, Optimisation of process parameters for direct metal deposition of H13 tool steel. Advanced Materials Manufacturing & Characterisation 2013, Volume 3 Issue 2 (2013), doi: 10.11127/ijammc.2013.07. [3] Kamran Shah, Izhar Ul Haq, Shaukat Ali Shah, Farid Ullah Khan, Muhammad Tahir Khan, Sikander Khan, “Experimental study of direct metal deposition of Ti-6Al-4V and Inconel 718 by using pulsed parameters”, The Scientific World Journal, Volume 2014, doi: 10.1155/2014/841549 [4] Dinda G P, Dasgupta A K, Mazumder J, Laser aided deposition of Inconel-625 super alloy: microstructural evolution and thermal stability, Material science and Engineering, A 2009 509, 98104 [5] Ryan Cottam, Milan Brandt, Laser cladding of Ti-6Al-4V powder on Ti-6Al-4V substrate: Effect of laser cladding parameters on microstructure, Physics Proceedia 12 (2011) [323-329] W.H.Yang, Y.S.Tarng, Design optimization of cutting parameters for turning operations based on the Taguchi method, Journal of Materials Processing Technology 84 91998) 12-129 [6] Qun-li Z, Jian-Hua Y, Mazumder J, Laser direct metal deposition technology and microstructure and composition segregation of Inconel 718 super alloy, 2011, Journal of Iron an Steel Research, 18 (4),73-78 [7] W.H.Yang, Y.S.Tarng, Design optimization of cutting parameters for turning operations based on the Taguchi method, Journal of Materials Processing Technologies 84 (1980) 122-129. [8] T.P Bagchi, Taguchi Methods Explained, Printice-Hall of India, 1993 [9] Phadke, M.S. Quality Engineering Using Design of Experiment, Quality Control, Robust Design and Taguchi Method, 1998 California, Warsworth & Books. [10] Rama Rao, S. Padmanabhan.G, Application of Taguchi methods and ANOVA in ootimisation of process parameters for metal removal rate in electrochemical machining of Al/5%SiC composites, International Journal of Engineering Research and Applications (IJERA), Vol 2, Issue 3, May-Jun 2012, pp. 192-197. [11] J Jayakumar, Dr. T.Senthil Kumar, Review study of laser cladding processes on ferrous substrates, 2015, International Journal of Advanced Multidisciplinary Research, 2(6): (2015), Pages 72–87. [12] Jun Yu, Marleen Robouts, Gert Maes, Filip Motmans, Material properties of Ti-6Al-4V parts produced by laser metal deposition, Journal of physics proceedia, 39 (2012) 416-424 [13] J. Michael Wilson, Yung C.Shin, Microstructure and wear properties of laser-deposited functionally graded Inconel 690 reinforced with TiC, Journal of Surface and Coatings Technology, 207 (2012) 517-522 Cite the paper Jyothish Kumar & C.G. Krishnadas Nair, (2016). Laser Metal Deposition Repair Applications for Ti-6Al-4V Alloy. Mechanics, Materials Science & Engineering, Vol 7. doi:10.13140/RG.2.2.35949.38889


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Statistical Study of Corrosion Types in Constructions in South Region of Rio De Janeiro - Brazil3 Carolina Lacerda da Cruz1, Thalita Gonçalves de Lima1, Nilo Antônio S. Sampaio1,2, José Wilson de Jesus Silva1,3 1 – Asociação Educacional Dom Bosco, AEDB, Resende, RJ, Brazil 2 – Universidade do Estado do Rio de Janeiro, UERJ, Resende, RJ, Brazil 3 – Centro Universitário Teresa D’Ávila, UNIFATEA, Lorena, SP, Brazil DOI 10.13140/RG.2.2.29609.60004 Keywords: corrosion, construction, corrosion inhibitors, corrosion protection, corrosion in south region. ABSTRACT. Some of the most difficult and troubling problems encountered in construction are those caused by corrosive processes. The corrosion processes are constituted by some material degradation, generally metallic material, by means of chemical or electrochemical actions of environment in which the material are and can or cannot be combined with mechanical stress. Corrosion is present in the materials in general. Their deterioration is caused by such physicalchemical interaction between the material and the corrosive environment where it causes major problems in several activities. In order to prevent material losses, anticorrosive techniques are used which include coatings, medium modification techniques, anodic and cathodic protection, and corrosion inhibitors such as the organic compounds use. This article analyses the statistical study of corrosion types in construction in south region of Rio de Janeiro, Brazil.

Introduction. The financial losses by processes of degradation and structures corrosion of metal and concrete in an engineering work are generally very high. Surveys have found that the annual corrosion cost in the United States is about 3.1% of GDP, amounting to about 276 billion [1]. While in Brazil, this cost is about 3.5% of GDP. Corrosion may be defined as a deterioration process of the material that produces harmful and undesirable changes in the structural elements, since the corrosion product is an element different of the original material, making the alloy loses its essential qualities, (such as mechanical strength, elasticity, ductility, aesthetics) [2]. Corrosion can focus on several materials types, whether metallic or non-metallic and root causes of this deterioration are different taking into account the material and the medium. All these processes are of spontaneous nature, which occur with greater or lesser speed and intensity. The speed at which corrosion proceeds is given by the total mass of material removed in a given area during a given time. Some factors help to influence this speed, such as corrosive medium, temperature and speed effect [3]. There are some protection mechanisms whose purpose is to increase the structure life. Corrosion resistance increase by means of anticorrosive protection practices adopted in the design phase is one of the most important control forms. This resistance increase can be achieved by adopting practices that minimize the corrosion problems or using anticorrosive protection techniques [4]. For metal structures protection it is traditional to use organic paints, metallic and non-metallic coatings, which are usually effective against the corrosion process however this effectiveness will depend on some factors such as application method, environment, exposure time to weather and more. © 2016 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/


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For reinforced concrete structures in which their physical properties are result from combination of resistance to compression of concrete itself and high tensile strength which is given to the steel. Concrete consists of cement, aggregates, water and additives, therefore the defects of each of these materials may influence unfavorably on the most important characteristics of the concrete: mechanical strength, stability and durability. These three characteristics are related to a number of factors among which we highlight the homogeneity and compactness [5]. In addition to structural advantages that result from combination of both materials, the concrete acts as a physical barrier of reinforcement in relation to environment and have chemical characteristics that provide the steel excellent corrosion protection. However, in the course of time it was proved that reinforced concrete also deteriorated by both degradation process of concrete itself and by corrosion of its armor. If the concrete coating on the armor is not maintained in good condition one cannot expect a good performance of reinforced concrete, Fig. 1. Its deterioration may be caused by cracks, mechanical erosion, freezing, acid attack, attack by sulfates, alkali-aggregate reaction, biological attack, desalination [6]. Due to the environment in which it will exercise its activity, a structure can require chemical and physical protection, produced by a good compact and waterproof coating. Furthermore, a structure may require additional protections, which can act directly on steel, as in the case of cathodic protection, electroplating and coating with synthetic resins or on the concrete, as with the corrosion inhibitors and the resin or asphaltic paints [7].

Fig. 1. Steel structure. Materials and methods. For metallographic analysis, cylindrical samples of CA 50 rebar were used. The sample was mechanically polished using SiC paper (80-1200). The electrochemical study was initiated by analyzing potential measurements on open circuit. For this purpose, it was used a conventional thermostated glass cell, Fig. 2, and a reference electrode of Ag/AgCl KCl sat. As electrolyte, it was prepared an aqueous solution from sodium chloride (NaCl) 2.0 and 4.0 g/L. The equipment used was an AUTOLAB coupled with a computer for control and data processing, Fig. 3. Prior to each measurement the alloy surface had to be finely polished, free of scratches when viewed under a microscope. MMSE Journal. Open Access www.mmse.xyz

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The electrochemical cell used in the test is composed of three electrodes: the polished steel surface was the working electrode; as an auxiliary electrode it was used a Pt mesh; as a reference electrode the Ag|AgCl|KClsat. and a beaker where sodium chloride is placed [8]. The equipment used in the experiment was a potentiostat/galvanostat AUTOLAB (brand: Eco Chemie B.V., Utrecht, Netherlands, model PGSTAT302). The samples were previously sanded with sandpaper SiC immediately before the test then being washed with distilled water and then were immersed in the test solution, thereby initiating polarization [9]. The tests were repeated twice per solution.

Fig. 2. Conventional electrochemical thermostatically cell of borosilicate glass.

Fig. 3. AUTOLAB coupled to a computer. Results and discussion. In this topic it is presented and discussed the experimental results of corrosion tests of the materials described in this work. In the figure below (Fig. 4), the curve representing the open circuit potential [10] is presented as a function of time for the steel samples studied and tested in a NaCl solution, 2.0 and 4.0 g/L at room temperature. The open circuit potential evaluation provides a comparison of corrosive material in MMSE Journal. Open Access www.mmse.xyz

25


different media, so that the higher the value of this potential, the greater its corrosion resistance in the medium considered. It is emphasized that this potential is a thermodynamic factor and is related to the tendency for corrosion to occur, i.e. with the Gibbs free energy. According to figures (Fig. 5 and 6), a typical active state behavior was observed by the potential descending with time. Variation in solution concentration produced a significant difference (~ 0.08 V) between the two measurements when the OCP value approaches the steady state, indicating that the change in chloride ions concentration turns the medium more oxidizing.

E (v) vs. Ag|AgCl|KClsat.

Fig. 4. OCP curves for CA-50 steel in two concentrations of chloride ions.

-0,3 -0,4

NaCl 2,0 g/L NaCl 4,0 g/L

-0,5 -0,6 -0,7 -0,8 -0,9 -8

-7

-6

-5

-4

-3

-2

-2

Log (I / A cm )

Fig. 5. Tafel curves obtained after 3 immersion hours of steel in chloride medium.

E (v) vs. Ag|AgCl|KClsat.

1,2 Tafel Curva CP

0,9

NaCl 2,0 g/L

0,6 0,3 0,0 -0,3 -0,6 -0,9 -8

-7

-6

-5

-4

-3

-2

-2

Log (I / A cm )

Fig. 6. Comparison between potentiodynamic profiles of a Tafel curve and a CP curve obtained in NaCl 2.0 g/L medium. MMSE Journal. Open Access www.mmse.xyz

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For this type of steel, the electrochemical mechanism of corrosion process originates in the form of localized corrosion (crevice) usually associated with electrolyte stagnation conditions in microenvironments where there is hindrance or difficulty to the spread of chemical species. The solution within the crack is deoxygenated due to initial corrosion that consumes, through cathodic process, the oxygen in solution: O2 + 2H2O + 4e 4OH-. The oxygen diffusion rate into the crack is not fast enough to replenish the oxygen consumed in the cathodic process. The cathodic process moves out of the crack where oxygen is plentiful. There is separation of anodic and cathodic regions. The ferrous ions are formed within the crack (Fe Fe ++ + 2e-) and hydroxyls in oxygenated regions. The ferrous ions undergo hydrolysis (Fe ++ + H2O Fe (OH) + + H+) and decrease the pH within the crack. Due to the current flow and mass transport phenomena, aggressive ions migrate under the influence of electrostatic field into the crack, and are concentrated there, causing great changes in chemical conditions. As a result there is the iron hydroxide (II), white color, which due to the oxidation process is turned slowly into iron hydroxide (III), which has a brown-orange coloration according to the iron content (III) .When this type of coloring appears in structures (concrete and steel), it indicates that they are suffering corrosion. The oxidized iron assumes that color and begins to crumble. In the affected areas, the metal will lose density and, if the process is not contained, it can reach the full degradation. The curve corresponding to the steel in NaCl 2.0 g/L, Fig. 5, was overlapped with the anode region of a CP curve obtained under the same experimental conditions as Fig. 6, to verify the repeatability in the current response during the scan of potentials of electroactive area and also to illustrate the active steel behavior in chloride medium within a wide potentials range, shown by the presence of positive hysteresis and the absence of a passivation region in the reverse scan, showing a generalized corrosion process. In the investigated pH range (between 5.0 and 6.0 before and after corrosion tests) the anodic reactions involve the formation of complex ions of Fe (II) and Fe (III) and possible precipitation Fe(III) hydroxide. Statistical study. Corrosion in civil construction is directly linked to its increase. The civil construction industry in Brazil grew above GDP in the period 2010-2013, Fig. 7. The civil construction is a featured segment in south economy in Rio de Janeiro, being responsible for almost 25% of new jobs in recent years [11].

Fig. 7. Civil Construction in Brazil grew above the GDP in the period 2010 to 2013.


27


This growth was due to the need for improvements in the country boosted, for example, by the World Cup, 2016 Olympics in Rio de Janeiro with the need for Brazil in infrastructure, the Accelerated Program for Growth (PAC, in Portuguese) and the program called "My house, my Life" (Minha Casa, Minha vida - in Portuguese) sponsored by a federal bank. The State Government, by means of the Department of Highways and Roads (DER, in Portuguese), made in the last two years important interventions on state roads which have improved the population routine. Counties of state south were Rio Claro, Miguel Pereira and Barra do Pirai that have received improvements to their roads (paving, drainage and coasting building and extending bridges). This year, it was given to paving the RJ-151, between Visconde de Mauá and Campo Alegre. With investments of US$ 2.25 million, the work included paving, drainage, earthworks, rock blasting and track enlargement of the RJ-151, and an extension of 8.4 km. Even with Brazilian economy slowdown, the companies located in the South of Rio de Janeiro - region integrated by counties like Resende, Itatiaia, Porto Real and Volta Redonda - proceeding with their investment plans of more than US$ 3.75 billion for the period 2010-2016. It is projects like the new Nissan plant in Resende, of US$ 0.8 billion, and the expansion of the plant of PSA Peugeot Citroën, in Porto Real, US$ 1.16 billion. The number does not consider the works of Angra 3, which has received US$ 0.88 billion this year. The construction industry is one of the sectors of the economy of most impact on employment and population welfare. Investments in infrastructure and housing demand large volumes of steel (rebar for reinforced concrete CA60, CA50 and CA25, latticework frames, brackets, etc.) The civil construction shows its importance also in the economic and social aspect. Thus, the amounts of activities are part of the construction production cycle that serves the consumer goods and services for other sectors. In addition, the civil construction, from the social point of view, is a great capacity to generate jobs and labor, direct labor and indirect absorption mainly little and unskilled. The performance of construction is influenced directly and strongly by the performance of the economy, Figs. 8 to 15 [12-15].

Fig. 8. Growth (%) of establishments number by sectors of IBGE (Brazilian Institute of Geography and Statistics, in Portuguese) in the Mid-Paraíba region of Rio de Janeiro (2011).


28


Fig. 9. Growth of Establishments number by IBGE Sectors in the South Central Region of the State of Rio de Janeiro (2011).

Fig. 10. Growth (%) of Establishments Number by IBGE sectors in the Costa Verde region of Rio de Janeiro State (2011).

300% 250% 200%

150% 100% 50%

-50% -100%

Porto Real Itatiaia Pinheiral Resende Quatis Volta Redonda Barra Mansa Barra do Piraí Rio Claro Piraí Valença Rio das Flores Três Rios Sapucaia Paty do Alferes Paraíba do Sul Engenheiro Paulo de Frontin Mendes Vassouras Miguel Pereira Areal Comendador Levy Gasparian Paraty Angra dos Reis Mangaratiba

00%

Fig. 11. Establishment numbers in some cities in the southern state.


29


Fig. 12. Distribution (%) of Employees Number by Counties of Fluminense South Central Region of Rio de Janeiro State / IBGE Sectors (2011).

Fig. 13. Distribution (%) of Employees Number by Counties of Middle Paraiba Region of Rio de Janeiro State / IBGE Sectors (2011).

Fig. 14. Distribution (%) of Employees Number by Counties in Costa Verde region in Rio de Janeiro State / IBGE Sectors (2011).


30


0.25 0.2 0.15 0.1 0.05 0

Fig. 15. Numbers of employees in some cities in the southern state. Summary. With the end of the work, it is presented by means of researches and tests, the causes of corrosion of the studied area, which are directly influenced by the location in which the buildings are, influenced by salt spray and different climates present throughout southern Rio de Janeiro. With the construction boom, it tends to be more careful with concrete for durability achieve as much as possible. References [1] Koch, G. H., Brongers, M. P., Thomson, N. G., Virmanio, Y. P., & Payer, J. H. (2005). Cost of corrosion in the United States. Handbook of environmental degradation of materials, 3-24. [2] OLIVARI, G. (2003). Patologia em edificações. São Paulo: Universidade Anhembi Morumbi. [3] V. GENTIL - Corrosão. Rio de Janeiro: LTC – Livros Técnicos e Científicos Editora, 1994. [4] Portella, K. F., Garcia, C. M., Vergés, G. R., Joukoski, A., Freire, K. R. R., & de PCorrea, A. (2006). Desempenho físico-químico de metais e estruturas de concreto de redes de distribuição de energia: Estudo de caso na região de Manaus. Química Nova, 29(4), 724. [5] Cánovas, M. F. (1988). Patologia e terapia do concreto armado. Pini. [6] Hoar, T. P., & Mears, D. C. (1966, October). Corrosion-resistant alloys in chloride solutions: materials for surgical implants. In Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences (Vol. 294, No. 1439, pp. 486-510). The Royal Society. [7] Marino, C., & de Titânio, Ó. A. (1997). um estudo do crescimento e estabilidade em meio ácido. 1997. 135f (Doctoral dissertation, Dissertação (Mestrado em Físico-Química)–Universidade Federal de São Carlos, São Carlos). [8] Silva, L. L. G. (2001). Eletrodos em diamante CVD para estudos eletroquímicos. Eletrodos em diamante CVD para estudos eletroquímicos. [9] de Macena Rezende, D. (2014). ESTUDO DA FRAGILIZAÇÃO PELO HIDROGÊNIO NO AÇO SUPER 13Cr MODIFICADO (Doctoral dissertation, Departamento de Engenharia Metalúrgica e de Materiais da Escola Politécnica, Universidade Federal do Rio de Janeiro). [10] Greaney, M. J., Das, S., Webber, D. H., Bradforth, S. E., & Brutchey, R. L. (2012). Improving open circuit potential in hybrid P3HT: CdSe bulk heterojunction solar cells via colloidal tertbutylthiol ligand exchange. Acs Nano, 6(5), 4222-4230. MMSE Journal. Open Access www.mmse.xyz

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[11] Lins, L. M., Salerno, M. S., Araújo, B. C., Gomes, L. A. V., Nascimento, P. A. M. M., & Toledo, D. (2014). Escassez de engenheiros no Brasil? Uma proposta de sistematização do debate. Novos Estudos-CEBRAP, (98), 43-67. [12] Sociais, R. A. D. I. Ministério Do Trabalho E Emprego (RAIS/MET). 2006-2011. Base de Dados. [13] Sawacha, E., Naoum, S., & Fong, D. (1999). Factors affecting safety performance on construction sites. International journal of project management, 17(5), 309-315. [14] Porter, M. (2003). The economic performance of regions. Regional studies, 37(6-7), 549-578. [15] Leiblein, M. J., Reuer, J. J., & Dalsace, F. (2002). Do make or buy decisions matter? The influence of organizational governance on technological performance. Strategic management journal, 23(9), 817-833. Cite the paper Carolina Lacerda da Cruz, Thalita Gonçalves de Lima, Nilo Antônio S. Sampaio, José Wilson de Jesus Silva (2016). Statistical Study of Corrosion Types in Constructions in South Region of Rio De Janeiro – Brazil. Mechanics, Materials Science & Engineering, Vol 7. doi: 10.13140/RG.2.2.29609.60004


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Influence of the Composition of (TlGaS2)1-х(TlInSe2)x Alloys on Their Physical Properties4 Mustafaeva S.N.1,a, Jafarova S.G. 1, Kerimova E.M. 1, Gasanov N.Z. 1, Asadov S.M.2 1 – Institute of Physics, National Academy of Sciences of Azerbaijan, AZ–1143, G. Javid Pr., 131, Baku, Azerbaijan 2 – Institute of Catalysis and Inorganic Chemistry, National Academy of Sciences of Azerbaijan, AZ–1143, G. Javid Pr., 113, Baku, Azerbaijan a – [email protected] DOI 10.13140/RG.2.2.29609.600

Keywords: TlGaS2, TlInSe2, alloys physical properties, roentgensensitivity, photoresistors.

ABSTRACT. The single crystals of (TlGaS2)1-х(TlInSe2)х (х = 0–0,5) solid solutions have been grown up. The photoelectric, roentgendosimetric, dielectric and optical characteristics of the (TlGaS 2)1-х(TlInSe2)х solid solutions with various compositions have been determined. The maximum and spectral range of photosensitivity were found to redshift as x increases from 0 to 0.5. Both the photo- and roentgensensitivity of the solid solutions are higher than those of pure TlGaS2. The nature of dielectric losses and the hopping mechanism of charge transport in the (TlGaS 2)1-х(TlInSe2)х solid solutions were established from the experimental results on high-frequency dielectric measurements. The temperature dependences of exciton peak position for various compositions (x = 0-0.3) are investigated in 77-180 K temperature interval. It was established that with increasing x in (TlGaS2)1-х(TlInSe2)х solid solutions the width of their forbidden gap decreases.

PACS: 71.20.Nr; 71.35.Cc; 72.15.Rn; 72.20.Ee; 72.20.Jv; 72.30.+q; 72.40.+w; 73.20.At Introduction. Ternary layer-chain TlGaS2 and TlInSe2 single crystals exhibit high photo- and roentgensensitivity making them well-suited for photoresistors and roentgendetectors [1-4]. The study of physical properties of the TlGaS2, TlInSe2 compounds and solid solutions on their base are very important for establishing the relations between their compositions and properties. This offers the possibility of controlling the band gap, energy position of emission bands and electrical conductivity of such semiconductors. In [5-7] the results of investigation of ac – electric and dielectric properties of TlGaS2, TlInSe2 and diluted (TlGaS2)1-х(TlInSe2)х solid solutions (x = 0.005 and 0.02) are given. The purpose of present work was to investigate the influence of (TlGaS2)1-х(TlInSe2)х solid solutions compositions (x = 0-0.5) on their photo- and roentgensensitivity, ac – electric, dielectric and optical properties. Experiment. The synthesis of (TlGaS2)1-х(TlInSe2)х solid solutions was carried out in an ampule evacuated to pressure 10-3 Pa. The ampule was fabricated from a fused silica tube. In this case, (TlGaS2)1-х(TlInSe2)х samples were prepared through the interaction of initial components (TlGaS2 and TlInSe2). In order to prevent the ampule filled with reactants from explosion, the furnace temperature was raised to the melting temperature of selenium (T = 493 K) and the ampule was held at this temperature for 3h. Then, the furnace temperature was raised to T = 1080 K at a rate of 50 K/h and the ampule was held at this temperature for 4 h, after which it was cooled to 300 K at a rate of 20 © 2016 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/


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K/h. Phase purity of (TlGaS2)1-х(TlInSe2)х was established by differential thermal analysis and powder X-ray diffraction. Each sample was used as the charge for Bridgman crystal growth. The crystal data for (TlGaS2)1-х(TlInSe2)х are presented in the Table 1. Table 1. Crystal data for TlGaS2 and (TlGaS2)1-х(TlInSe2)х. Solid solution composition

а(Å)

b(Å)

c(Å)

, deg

Z

Sp.gr.

TlGaS2

10.40

10.40

15.17

100.06

16

P21/n

(TlGaS2)0.9(TlInSe2)0.1

10.40

10.40

15.18

100.06

16

P21/n


10.41

10.41

15.18

100.06

16

P21/n


10.43

10.43

15.181

100.06

16

P21/n


10.435

10.435

15.20

100.06

16

P21/n


10.452

10.452

15.245

100.06

16

P21/n

The spectral characteristics were recorded with a GIBI-TIBI potentiometer; the samples were illuminated with a 400-W incandescent lamp through a DMR-4 monochromator. In roentgendosimetry measurements, we used a URS-55 X-ray generator. The variation in sample resistance under X-ray irradiation was followed with an R-4053 bridge. X-ray dose rates were measured with a DRGZ-02 dosimeter. Measurements of the dielectric properties of (TlGaS2)1-х(TlInSe2)х (x = 0.1; 0.2) single crystals were performed at fixed frequencies in the range 5×104–3.4×107 Hz by the resonant method using a TESLA BM560 Qmeter. The single-crystal samples for dielectric measurements had the form of planar capacitors normal to the C- axis of the crystals, with silver-paster electrodes. The thickness of the crystal samples was 90–120 µm, and the area of the capacitor plates was 8×10-2–2×10-1 cm2. All dielectric measurements were performed at T = 300 K. The accuracy in determining the resonance capacitance and the quality factor Q=1/tanδ of the measuring circuit was limited by errors related to the resolution of the device readings. The accuracy of the capacitor graduation was ±0.1 pF. The reproducibility of the resonance position was ±0.2 pF in capacitance and ±(1.0–1.5) scale divisions in quality factor. The largest deviations were 3–4% in ε and 7% in tan δ. Optical absorption spectra were measured using samples in the form of platelets 10–100 µm thick, cleaved from the single-crystal ingots. Light was incident along the normal to the layers of the samples, that is, along the crystallographic axis C of the crystals. Optical transmission spectra were measured as functions of temperature using an experimental setup built around a KSVU-6M system and UTREKS helium cryostat, which ensured temperature stabilization with an accuracy of ± 0.01 K. The setup included an MDR-6 double monochromator and FEU-100 photomultiplier tube. The spectral resolution of the experimental configuration was = 2 Å. Results and discussion. We measured the spectral dependences of photoconductivity and photosensitivity Rd/Rph (Rd is the dark resistance, and Rph is the resistance of the sample under abovegap illumination) at a steady illumination, as well as the roentgensensitivity and other photoelectric parameters. Table 2 and fig.1 give the photoelectric properties of the (TlGaS 2)1-х(TlInSe2)х solid solutions.


34


Table 2. Photoelectric and roentgendosimetric characteristics of the (TlGaS2)1-х(TlInSe2)х solid solutions. Solid solution composition TlGaS2 (TlGaS2)0.9(TlInSe2)0.1 (TlGaS2)0.8(TlInSe2)0.2 (TlGaS2)0.7(TlInSe2)0.3 (TlGaS2)0.6(TlInSe2)0.4 (TlGaS2)0.5(TlInSe2)0.5

∆λmax, µm 0.46-0.57 0.50-0.62 0.55-0.66 0.59-0.71 0.64-0.76 0.69-0.81

Rd, Ohm (3-5)×1010 (1-2)×1010 (3-4)×109 (2-3)×108 (1-2)×107 (3-5)×106

Rd/Rph at 200 lx 5-8 10-25 15-30 21-37 23-42 25-46

K, min/R 0.063-0.159 0.075-0.178 0.089-0.198 0.098-0.213 0.107-0.219 0.142-0.252

From fig. 1 one can see, that the photosensitivity maximum (λmax) linearly shifts from 0.50 to 0.73 µm as x increases from 0 to 0.5. This shift is associated with a decrease in the band gap with increasing x. Increasing x leads to a redshift of the sensitivity range ∆λ and a considerable rise in Rd/Rph at 200 lx. For example, the Rd/Rph of (TlGaS2)0.5(TlInSe2)0.5 is 5 to 6 times greater than that of pure TlGaS2 (table 2). The rise in Rd/Rph with increasing x is apparently related to an increase in both the lifetime and mobility of the photogenerated carriers.

Fig. 1. Composition dependence of the photosensitivity maximum in (TlGaS2)1-х(TlInSe2)х solid solutions. Roengenosensitivity K of (TlGaS2)1-х(TlInSe2)х was characterized by relative change in conductivity per unit dose rate,

K 

 E ,0

0  E

(1)

where 0 – is the conductivity of the unirradiated crystal; ∆E,0 = E – 0 is the change in the conductivity under X-ray irradiation with dose rate E (R/min). Table 2 lists K values at accelerating voltages from 25 to 30 keV and dose rates from 0.75 to 10 R/min. One can see that the K of (TlGaS2)1-х(TlInSe2)х solid solutions exceeds that of pure TlGaS2. As the TlInSe2 content increases, K rises to 0.142–0.252 min/R at x = 0.5. MMSE Journal. Open Access www.mmse.xyz

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We measured also the electric capacitance of (TlGaS2)0.9(TlInSe2)0.1 and (TlGaS2)0.8(TlInSe2)0.2 samples in the frequency range 5×104–3.4×107 Hz. Using the measured capacities of these samples, we calculate the permittivity ε at different frequencies. The ε values of (TlGaS2)1-х(TlInSe2)х single crystals vary from 9.5 to 12.7 for x = 0.1 and from 9.8 to 11.6 for x = 0.2 over the entire frequency range studied, with no significant dispersion (the ε of TlGaS2 single crystal, as it was shown in [5], varies from 26 to 30 at f = 5×104–3×107 Hz). In contrast to what was reported for TlGaS2 [5], the frequency dependences of the loss tangent for the (TlGaS2)1-х(TlInSe2)х (x = 0.1; 0.2) single crystals have maxima, which points to relaxation losses [8]. The ac-conductivity of investigated samples varies as f 0.8 at f = 5×104–2×106 Hz for x = 0.1 and at f = 5×104–6×106 Hz for x = 0.2. At more high frequencies ac(f) – dependence of these crystals was superlinear (~f 1.4). The ac~ f 0.8-dependence indicates that the mechanism of charge transport is hopping over localized states near the Fermi level [9].

   3  ac ( f )   e 2 kTNF2 a 5 f ln ph  96  f 

4

(2)

where e – is the elementary charge; k – is the Boltzmann constant; NF – is the density of localized states near the Fermi level; a = 1/α – is the localization length, α is the decay parameter of the wave function of a localized charge carrier, ψ ~ e-αr; νph – is the phonon frequency. Using expression (2), we can calculate the density of states at the Fermi level from the measured values of the conductivity σac(f). Calculated values of NF for (TlGaS2)1-х(TlInSe2)х solid solutions (x = 0.1; 0.2) single crystals were given in Table 3 (localization radius is chosen as 14 Å, in analogy with the TlGaS2 single crystal [5]). Table 3. Parameters of (TlGaS2)1-х(TlInSe2)х single crystals obtained from high- frequency dielectric measurements. Crystal composition TlGaS2 (TlGaS2)0.9(TlInSe2)0.1 (TlGaS2)0.8(TlInSe2)0.2

NF, eV-1cm-3 2.1×1018 6.8×1018 7.7×1018

τ, s 2×10-6 9.8×10-7 3.3×10-7

R, Å 103 98 90

Nt, cm-3 4.2×1017 5.1×1017 6.5×1017

According to the theory of hopping conduction we calculate the mean hop distance (R) and mean hop time (τ) in an applied ac-electric field using the formula [9]:

 1   ph exp  2R 

(3)

where R – is the average hopping distance.

R

1  ph ln 2 f


36

(4)


These values also are presented in the table 3. Knowing NF and R from [9]:

4 3 E R NF  1 3 2

(5)

We estimate energetic scattering of trap states near the Fermi level (E): E = 0.075 eV for x = 0.1 and 0.085 eV for x = 0.2. Evaluated concentrations of deep traps determining the ac-conductivity of (TlGaS2)1-х(TlInSe2)х single crystals ( Nt  N F  E ) are given in last column of the table 3. It is seen from the table 3 that with increasing of x from 0 to 0.2 in (TlGaS2)1-х(TlInSe2)х single crystals the values of NF and Nt increased, but R decreased. Optical properties of (TlGaS2)1-х(TlInSe2)х (x = 0–0.3) single crystals have been studied in 77–180 K temperature interval. The thicknesses of crystals under study were 20–50 µm. Light was incident on the crystals in direction parallel to their crystallographic axis C. The present data on the optical properties of the (TlGaS2)1-х(TlInSe2)х demonstrate that, at temperatures from 77 to 180 K crystals have an absorption band near fundamental absorption edge, which is due to transitions to a direct exciton state. We examined the temperature dependence of the energy position of the exciton peak for (TlGaS2)1-х(TlInSe2)х crystals in the temperature range 77– 180 K (fig. 2). It is seen that the peak position of the exciton band of (TlGaS 2)1-х(TlInSe2)х solid solutions has a positive temperature coefficient. Given that the exciton energy is a weak function of temperature, this indicates that the band gap of (TlGaS2)1-х(TlInSe2)х crystals increases with temperature.

Fig. 2. Temperature dependences of the energy position of the exciton peak at the absorption edge of (TlGaS2)1-х(TlInSe2)х solid solutions: (1) x = 0; (2) x = 0.02; (3) x = 0.1; (4) x = 0.2; (5) x = 0.3. The temperature variation of the band gap of semiconductors Eg, is known to be determined by a combined effect of the thermal expansion of their lattice and electron-phonon interaction. Semiconductors rarely have a positive temperature coefficient of their band gap. In particular, such an experimental fact in TlGaS2 and TlGaS2-based single crystals [10, 11] is thought to be caused by the significant contribution of the thermal expansion of their lattice to the temperature variation of Eg. Thus, the TlGaS2 and (TlGaS2)1-х(TlInSe2)х crystals were found to be similar in the structure of their absorption edge, formed by direct interband transitions. MMSE Journal. Open Access www.mmse.xyz

37


Summary. The results of photoelectric, roentgenodosimetric and high-frequency dielectric measurements on obtained (TlGaS2)1-х(TlInSe2)х solid solutions provided an opportunity to increase photo- and roentgenosensitivity, to determine the mechanism of dielectric losses and charge transport, and also to evaluate the density of localized states at the Fermi level, the average time of charge carrier hopping between localized states, average hopping distance, scattering of trap states near the Fermi level and concentration of deep traps responsible for ac-conductivity. The temperature dependences of exciton peak position for (TlGaS 2)1-х(TlInSe2)х solid solutions were investigated in 77–180 K temperature interval. It is established that the edge of optical absorption of these solid solutions is formed by straight line exciton with the positive temperature coefficient. References [1] Mustafaeva, S.N., Kerimova, E.M., Ismailova, P.G., and Asadov, M.M., Roentgendosimetric characteristics of detectors on the base of TlGaS2〈Yb〉 single crystals, Fizika, 2004, no. 4, p. 108. [2] E.M. Kerimova, S.N.Mustafaeva, Yu.G.Asadov, R.N.Kerimov. Synthesis, growth and properties of TlGa1– xYbxS2 crystals, Crystallography Reports, 2005, V.50, Suppl. 1, P.S122–S123. [3] S.N. Mustafaeva, Photoelectric and x-ray dosimetric properties of TlGaS2〈Yb〉 single crystals Physics of the Solid State, 47, 2015 (2005), doi:10.1134/1.2131137 [4] S.N. Mustafaeva, E.M. Kerimova, M.M. Asadov, R.N. Kerimov, Roentgenodetectors on the base of TlInSe , Fizika, Vol. 9, 62 (2003). [5] S.N. Mustafaeva, Frequency dispersion of dielectric coefficients of layered TlGaS single crystals Physics of the Solid State, Vol. 46, 1008 (2004). [6] S.N. Mustafaeva, Frequency dependence of real and imaginary parts of complex dielectric permittivity and conductivity of TlInSe single crystal at relaxation processes, Journal of Radioelectronics, 7, 8 (2013). [7] Mustafaeva, S.N. Frequency effect on the electrical and dielectric properties of (TlGaS2)1- x(TlInSe2)x (x = 0.005, 0.02) single crystals, Inorg Mater (2010) 46: 108. doi:10.1134/S0020168510020032 [8] V.V. Pasynkov, V.S. Sorokin, Materials of electron techniques, Sankt-Petersburg- Moscow, 2004.368 p. [9] N. Mott and E. Davis, Electron processes in noncrystalline materials, Clarendon Press, Oxford, 1971. 472 p. [10] Mustafaeva, S.N., Asadov, M.M., Kyazimov, S.B. et al. T-x phase diagram of the TlGaS2-TlFeS2 system and band gap of TlGa1 − xFexS2 (0 ≤ x ≤ 0.01) single crystals, Inorg Mater (2012) 48: 984. doi:10.1134/S0020168512090117. [11] Mustafaeva, S.N., Asadov, M.M., Kerimova, E.M. et al. Dielectric and optical properties of TlGa1−xErxS2 (x = 0, 0.001, 0.005, 0.01) single crystals, Inorg Mater (2013) 49: 1175. doi:10.1134/S0020168513120121 Cite the paper Mustafaeva S.N., Jafarova S.G., Kerimova E.M., Gasanov N.Z., Asadov S.M. (2016). Influence of the Composition of (TlGaS2)1-х(TlInSe2)x Alloys on Their Physical Properties. Mechanics, Materials Science & Engineering, Vol 7. doi:10.13140/RG.2.2.29609.600


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Enhancement of Optical and Thermal Properties of γ- Glycine Single Crystal: in the Presence of 2-Aminopyridine Potassium Chloride5 R. Srineevasan1,а, D. Sivavishnu1, K. Arunadevi1, R. Tamilselvi1, J. Johnson1, S. M. Ravi Kumar1 1 – P. G & Research Department of Physics, Government Arts College, Tiruvannamalai, 606603, India а – [email protected] DOI 10.13140/RG.2.2.33138.654

Keywords: slow evaporation, single crystal, NMR spectrum, TGA-DTA, SHG efficiency. ABSTRACT. In this research paper, an overview of polymorph γ-form glycine single crystal crystallization in the presence of 2-aminopyridine potassium chloride as an additive at an ambient temperature by slow evaporation solution growth technique (SEST) has been presented. FTIR and NMR studies confirm the presence of functional groups in the grown crystal. In the UV–Visible NIR optical absorption spectral studies from 200 nm to 900 nm, the observed 0% absorption with lower cutoff wave length at 240 nm and high band gap (5. 5eV) enabled enhanced linear optical properties. Powder XRD study confirms crystalline nature of the grown γ-glycine crystal. The single crystal XRD study shows that the grown crystal possesses hexagonal structure and belongs to space group P31 with the cell parameters a=7. 09 Å; b=7. 09; c=5. 52 Å; α = β = 90˚; and γ = 120˚. Thermal studies have been carried out to identify the elevated thermal stability and decomposition temperature of the grown sample. Dielectric studies of as grown γ-glycine crystal exhibit low dielectric constant at higher frequencies, which is most essential parameters for nonlinear optical applications. Enhanced SHG efficiency of the grown crystal was confirmed by the Kurtz powder technique using Nd:YAG laser and found 1. 6 times greater than that of inorganic standard potassium dihydrogen phosphate.

1. Introduction. Highly polarizable conjugated system of organic molecule possesses non-centro symmetry structure and the inorganic molecule (anion), linking through hydrogen bond with organic molecule (cation) yields strong mechanical and high thermal stability [1, 2]. Molecular charge transfer induced in semiorganic complex by delocalized π electron, such that moving between electron donor and electron acceptor which are in opposite sides of the molecules [3, 4]. In the base acid interaction of organic and inorganic molecules, there is a high polarizable cation derived from aromatic nitro systems, linked to the polarizable anion of inorganic molecules through hydrogen bond network yields a noncentrosymmetric structural systems and this hydrogen bonding energy between organic and inorganic molecules made the dipole moment in parallel fashion ensures the increase of second harmonic generation activity [5]. The structures of 2-aminopyridine complexes have already been studied by Chao and his co-workers [6]. In recent years metal organic complexes have been played reasonable attention in advancement of technology [2,7]. Growth of 2-aminopyridine complex crystals is widely used in the rapid advancement in technology, such as ultra-fast phenomena, optical communication and optical storage devices , frequency doublers and optical modulators [8]. Optical properties of 2-aminopyridine complexes and their suitability for optoelectronic devices have been reported [9-14]. Metal organic nonlinear optical crystals possess good second harmonic generation efficiency, hence rich demand in optical storage devices, color display units and optical communication systems [7]. Recent research focus is on designing of new materials capable of attaining SHG processes by strong interaction with an oscillating field of light. Amino acids with ionic salt complex crystals have been investigated and recognized as materials having good nonlinear optical properties [1,3,15-17]. In this present work, synthesis and crystallization of glycine into γ© 2016 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/


39


form glycine in the presence of aqueous solution 2-aminopyridine potassium chloride and their suitability for device fabrication with various enhanced optical and thermal properties are reported. 2. Experimental Procedure 2. 1 Material synthesis The title compound was synthesized by taking analytical grade glycine, 2-aminopyridine and potassium chloride in the stoichiometric ratio (1:1:1) with Millipore water of resistivity 18. 2 megaohm. cm-1 as a solvent. In this synthesis, protonation of nitrogen in pyridine ring facilitates hydrogen bonding interaction between potassium chloride and glycine such that 2-aminopyridine is linked to the metal K+ ion through pyridine ring nitrogen, rather than amino group nitrogen leaving (Cl)- ion [18]. C5 H6 N2 + KCl + NH2 CH2 COOH → [(K+) + C5H6N2 COOCH2 NH2 (Cl)–] [(2-aminopyridine) + (potassium chloride) + (glycine)]→ [(γ-glycine crystal)] Amino group hydrogen in 2-aminopyridine coordinates through hydrogen bond with carboxylic groups of monoprotonated glycinium ion. Stacking of γ- glycine crystal one over the other is shown in figure 1.

Fig. 1. Scheme of as grown γ-glycine crystal. 2. 2 Solubility study of γ-glycine in the presence of 2-aminopyridine potassium chloride Solubility is an important parameter, which dictates the crystal growth process. The solubilities of the title compound in aqueous medium were estimated in the temperature range between 25 and 50˚C. Neither a flat nor a steep solubility curve and less viscous solution enabling the faster transfer of the growth units by diffusion of the title compound, enables the growth of bulk crystals from solution. Variations in solubility at different temperatures is plotted in figure 2. The moderate variations in solubility indicate the reasonable growth rate of title compound along all crystallographic directions. MMSE Journal. Open Access www.mmse.xyz

40


20

2-APKCG

18

Solubility (g/100 ml)

16 14 12 10 8 6 4 2 25

30

35

40

45

50

0

Temperature ( C)

Fig. 2. Solubility curve of title compound at different temperatures. 2. 3 Crystal Growth The prepared mother solution was stirred vigorously for 4h using magnetic stirrer. High degree of purification of synthesized salt was achieved by successive recrystallization process. Synthesized saturated solution was filtered using filter paper of micron pore size. The filtered solution was pored in different petri dishes and covered with porous paper for slow evaporation. After a time span of 15 days, quality crystals of average size 13mm x 12mm x 3mm were harvested. The grown crystal is shown in figure 3.

Fig. 3. Grown γ-glycine crystal. 3. Results and discussion The as grown γ-glycine crystal was subjected to FTIR analysis using PERKIN ELMER SPECTRUM RX1 Fourier Transform infrared spectrometer. 1H NMR and 13C NMR spectroscopic studies were done by a Bruker Advance III 500MHz FTNMR spectrometer using D2O as solvent to identify the functional groups. The transmission behavior was studied by using LAMBDA-35 UV-VIS Spectrophotometer. Single crystal and powder XRD analysis were carried out on a PHILIPS X PERT MPD system. TGA and DTA analysis were carried out using NETZSCA STA 409 instrument at a heating rate of 20°C min-1 from ambient to 500°C. Dielectric studies were carried out by using HIOKI 3532 HiTESTER LCR meter. The NLO efficiency of the grown crystal was tested by KURTZ powder technique using Nd: YAG laser of wavelength 1064 nm. MMSE Journal. Open Access www.mmse.xyz

41


3. 1 Fourier Transform Infrared (FTIR) analysis The as grown γ-glycine crystal was subjected to FTIR analysis by KBr pellet technique in the wavelength between 4000 and 400 cm-1. The recorded absorption spectrum of title compound confirms the presence of various functional groups and their frequency assignments are shown in figure 4. The doublet frequency 928. 06 and 888. 46 cm-1 clearly shows the γ- glycine formation [19]. The vibrational frequencies are assigned with structure as shown in Table 1. Table 1. Frequency of the vibrations and their assignment of as grown γ-glycine crystal. Frequency in wave number (cm-1)

Assignment of vibration NH3+ Stretching

3105. 77 2887, 2604

Aliphatic CH2 Stretching NH3+ Stretching

1586. 84

NH2+ Bending

1492. 95

COO - Symmetric Stretching

1327. 82

CH2 Twisting

1126. 21

NH2+Rocking

1041. 67

C-N Stretching

928. 06

CH2 Rocking

888. 46

C-C-N Symmetric Stretching

683. 10

COO - Bending

502. 87

COO - Rocking

3500

3000

2500 2000 Wavenumber cm-1

1500

Fig. 4. FTIR spectrum of the grown γ-glycine crystal. C:\Documents and Settings\All Users\Desktop\MEAS\.5

srini 7

Instrument type and / or accessory

1000

502.87 452.34 412.37

683.10

928.06 888.46

1041.67

1126.21

1393.84 1327.82

1492.95

1586.84

2171.48

2360.74

2604.48

2887.67

3105.77

20

30

40

Transmittance [%] 50 60 70

80

90

100

2171. 48

500

19/12/2011

Page 1/1

3.2 NMR spectrum H NMR and 13C NMR analysis of the as-grown γ-glycine crystal were shown in figure 5 & 6. 1H NMR spectrum of as-grown γ-glycine crystal showed multiple peak signals at δ 3. 461 to 3. 445 ppm (quartet or triplet) corresponds to protons of methylene group (CH2) and peak at δ 4. 678 ppm due to amino group protons (NH2). 13C NMR spectrum of as-grown γ-glycine crystal showed peaks at δ 41. 1


42


429 ppm and δ 172. 41 ppm corresponding to methylene carbons and carbonyl carbon respectively. All the above results support the true chemical reactions in the formation of the γ-glycine crystal.

Fig. 5. 1H NMR of γ-glycine crystal.

Fig. 6. 13C NMR of γ-glycine crystal. 3.3 UV- Visible spectral analysis The optical properties of the crystals are mainly depending on the interaction between crystal and components of electric and magnetic fields of the electromagnetic wave. UV-Visible absorption spectrum of the grown crystal recorded in the wave length range 200-900 nm was shown in figure 7. The grown crystal has good transmission (100%) in UV, Visible and IR region. This highest transmission percentage (100%) clearly shows the intrinsic property of amino acid and their defect less nature of the grown γ-glycine crystal [20]. The absorption spectrum shows that the grown crystal has lower cut off wavelength at 240 nm and this characteristic is most favorable for nonlinear optical materials. Lower cut off wavelength value of the γ-glycine crystal (240nm) is compared with Glycine potassium chloride (GPC), Serine sodium chloride (SSC), Bis glycine Maleate, Pure Glycine, Glycine potassium sulphate (GPS), and Glycine picrate as shown in Table 2. This observed decreasing lower cutoff wavelength value of the as grown crystal is due to the addition of 2-aminopyridinium potassium


43


chloride. Hence the lower cut off wave length of as grown crystal can be suitably used for optoelectronic application in the UV, Visible and IR range. Table 2. Comparison of cutoff wave length. Crystals Name

Cutoff wave length(nm)

GPC

295

SSC

300

Bis glycine Maleate

330

Pure Glycine

346

GPS

384

Glycine picrate

450

γ- glycine crystal*

240

*present work 3.5

Absorbance (a.u)

3.0 2.5 2.0 1.5 1.0 0.5 0.0 200

300

400

500

600

700

800

900

Wavenumber (nm)

Fig. 7. UV-Visible absorption spectrum of grown crystal of γ-glycine. Since optical properties of the crystals are governed by the interaction between the crystal and the electric and magnetic fields of the electromagnetic wave, transmittance (T) was used to calculate the absorption coefficient (α) using the formula:


44


300

200

2

2

(alpha.hv) .ev .mm

2

250

150

100

50

Eg=5.5 ev

0 1

2

3

4

5

6

7

hv ev

Fig. 8. Plot of hυ versus (αhυ)2 of as grown γ-glycine crystal.

Where t is the thickness of the sample. The optical band gap (Eg) was evaluated from the transmission spectra and the optical absorption coefficient (α) near the absorption edge is given by [21]. αhυ=A(hυ-Eg)1/2 where A – constant; Eg – the optical band gap; h – the Plank’s constant; υ – the frequency of the incident photons. The graph drawn between hυ (E=hυ) and (αhυ)2 is used to estimate the direct band gap value of the grown crystal as shown in figure3. 5. The band gap of γ-glycine single crystal was estimated by extrapolating the linear portion near the onset of absorption edge to the E=hυ axis. From the figure 8, the optical band gap value is calculated to be 5. 5 eV. The wide band gap of the as grown γ-glycine crystal confirms the 100% transmittance in the UV-vis-NIR region and less defect concentration of the grown crystal [22]. The observed lower cutoff wavelength 240 nm of the as grown γ-glycine due to the addition of 2-aminopyridinium potassium chloride leads to an increase in the band gap of the grown γ-glycine crystal 5. 5 eV. Intraction of electromagnetic wave with high band gap materials ( ˃ 1 eV known as Wide-bandgap) create a bound electron–hole pair, which can permit devices to operate at much higher voltage, temperature and frequency applications. Also this high band gap material brings the electronic transition in the range of the energy of visible light as light-emitting diodes even blue LEDs or even produce ultraviolet LEDs with wavelengths down to 200–250 nm and lasers. 3.4 Powder XRD studies The grown γ-glycine crystal crushed to a uniform powder and subjected to powder x-ray diffractrometer with CuKα (λ=1. 540598 Å) radiations for structural analysis study. The powder form sample was scanned over the range 10-45˚ at the rate of 2˚/min. The indexed powder XRD pattern of grown crystal is shown in figure 9. Peaks in the XRD without any broadening confirm that the grown sample is higher order of crystalline nature. MMSE Journal. Open Access www.mmse.xyz

45

(102)


600

(031)

2-APKCG

400

(211)

(300)

(002) (112)

(210)

(002)(201) (201)

(112)

(120)

100

(200) (111)

(110)

(100)

(002)

(012)

200

(101)

300

(010)

(001)

(011)

Intensity (a.u)

500

0 10

15

20

25

30

35

40

45

Diffraction angle,2 (deg)

Fig. 9. Powder XRD pattern of as grown crystal γ-glycine. 3.5 Single crystal XRD analysis Single crystal X-ray diffraction analysis confirms the hexagonal structure of the γ-glycine crystal with space group P31. The unit cell parameters of the grown γ-glycine are a = 7.09Å; b = 7.09Å; c = 5.52Å; α = β = 90˚; γ = 120˚ and volume of the unit cell was found to be 278 Å3. These values are in-line with the literature values [23-25]. Further, it is evident that the presence of 2-aminopyridine potassium chloride in the aqueous solution, without enter into the grown crystal lattice, yields the polymorph form γ-glycine, as a physical change. 3.6 Thermal analysis Thermo gravimetric (TG) and Differential thermal analysis (DTA) gives information regarding phase transition, water of crystallization and different stages of decomposition of the crystal. Samples of γglycine crystals were weighed in an Al2O3 crucible with a microprocessor driven temperature control. TGA and DTA curves of grown crystals were recorded in nitrogen atmosphere between ambient temperature to 500˚C shown in figure 10. There is no weight loss up to 216.6˚C indicating that there is no inclusion of solvent (water) in the crystal lattice. The thermogram reveals that the major weight loss (42. 4%) starts at 216.6˚C and continues up to 484.4˚C with 1.255mg (57. 6%) as residue. The nature of weight loss indicates the decomposition of the material. Below 484.4˚C no weight loss was observed. DTA curve shows that the decomposition point of as grown γ-glycine crystal is 270˚C. This decomposition point was compared with the decomposition point of pure γ-glycine crystal (246˚C) and γ-glycine synthesizes in the presence of different additives are shown in Table 3. 3. 7 Dielectric studies Cut and polished samples were used as a dielectric material, which is placed between two copper electrodes of parallel plate capacitor. To ensure the good electrical conductivity to electrodes graphite was coated on opposite side of the sample.


46

Mechanics, Materials Science & Engineering, December 2016 – ISSN 2412-5954 40.00 100.0

216.6Cel 2.838mg

1.583mg 2.800 55.4%

95.0

484.4Cel 2.600 2.838mg

30.00 90.0

85.0

2.400

20.00 80.0

2.200 10.00

70.0

2.000

TG mg

DTA uV

TG %

75.0

609uV.s/mg 65.0 0.00

1.800

60.0

55.0

1.600 -10.00

50.0

45.0

1.400 -20.00

484.4Cel 1.200 1.255mg 100.0

200.0

300.0

400.0

500.0

Temp Cel

Fig. 10. TGA& DTA graph of as grown γ-glycine crystal. Table 3. comparison of decomposition point. γ-glycine crystal

Decomposition point

In the presence of CoCl

116. 86 ˚C [26]

In the presence of CaCl2

265 ˚C [27]

In the presence of AgNO3

208 ˚C [28]

In the presence of Li NO3

195 ˚C [29]

In the presence of LiBr

200 ˚C [30]

In the presence of NH3

145. 7 ˚C [31]

In the presence of NaNO3

256 ˚C [32]

In the presence of MgCl2

213 ˚C [33]

In the presence of KCl

170 ˚C [34]

In the presence of KF

259 ˚C [25]

In the presence of HF

240 ˚C [35]

In the presence of H3PO3 &

51 ˚C [36]

In the presence of H3PO3 + Urea

155 ˚C [36]

In the presence of C5H6N2+KCl (present work)

270 ˚C

The capacitance of the grown crystal was measured in the frequencies range between 500H Z to 5MHZ for different temperatures. The formula used to calculate dielectric constant is, Ɛr= Ct/ƐOA where C – is the capacitance; t-thickness of the sample; MMSE Journal. Open Access www.mmse.xyz

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Ɛo – the permittivity of the free space and A-the area of cross section. The graph shown in fig 8, shows the variation of Ɛr Vs frequency for the grown γ-glycine crystal at different temperature. The dielectric constant value increases at low frequency region and then dielectric constant value decrease with the increasing frequency. The Ɛr value reached the least value of about 250 at the applied frequency of 2 KHZ and the value remains constant for further frequency. A similar trend was observed for all the recorded temperatures and is compared with previous research report which is shown in table 4. Among the all four polarizations, electronic and space charge polarizations are predominant in the low- frequency region. The characteristic of low dielectric constant at higher frequency evident that the γ-glycine possesses an improved optical quality with lesser defects and this dielectric property is most important for nonlinear optical materials and their applications. 7000 o

40 o 45 o 50 o 55 o 60

6000

Dielectric Constant r

5000

C C C C C

4000 3000 2000 1000 0 2

4

6

8

Log f

Fig. 11. Dielectric behavior of γ-glycine crystal. Table 4. Comparision of dielectric constant. Crystal

Dielectric constant

2APTZS

2.5[37]

2APKSNG

3.5[38]

3.8 NLO studies In order to confirm the NLO property, powdered sample of grown crystal was subjected to KURTZ and PERRY powder technique, which is a powerful tool for initial screening of the materials for second harmonic generation (SHG) [39]. The beam of wave length λ =1064 nm from Q-switched Nd:YAG laser was made to fall normally on the prepared powdered sample of grown γ-glycine crystal, which was packed between two transparent glass slides. Suitable solution (CuSO4) was used to absorb the transmitted beam and the optical second harmonic signal was detected by a photomultiplier and displayed on CRO. Here powder form of KDP crystal of identical size to grown γ-glycine crystal powder particles were used as standard in the SHG measurement. The SHG behavior was confirmed from the emission of bright green radiation (532nm) by the sample. The measured amplitude of second harmonic green light for as grown γ-glycine crystal was 14.9mJ as against 8.8mJ of KDP and 8.9mJ of UREA. MMSE Journal. Open Access www.mmse.xyz

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The enhanced powder SHG efficiency of as grown γ-glycine crystal is about 1.65 times that of KDP and 1.63 times of UREA. This value is relatively high when compared to the SHG values reported for γ-glycine crystals grown with other additives and comparision is given in Table 5. This enhanced lasing performance of as grown γ-glycine crystal is due to the additive influence of 2aminopyridinium potassium chloride. The good second harmonic generation efficiency of as grown γ-glycine crystal in the presence of 2-aminopyridine potassium chloride attests, that the grown crystal is a potential candidate for nonlinear optical applications. Table 5. Comparision of SHG efficiency of γ-glycine crystals. γ-glycine crystal

# SHG efficiency

In the presence of NaF

1.3[40]

In the presence of NaOH

1.4[40]

In the presence of NaCl/KCl

1.5[41]

In the presence of NaCH2COOH

1.2[41]

*In the presence of C5H6N2+KCl

1.65

*Present work, # With reference to KDP Summary. We have successfully grown polymorph γ-form of glycine single crystals by slow evaporation solution growth technique at ambient temperature. FTIR & NMR spectral studies confirm that 2-aminopyridine potassium chloride not entered into the crystal structure, but they inhibit the growth of polymorph form γ-glycine. UV –Visible spectral studies show that it has the wide range of transmission from 240nm to 900nm with cut off wave length 240 nm and the observed high transmittance percentage (100%) from 240 nm clearly indicates that the grown crystal possessing good optical transparency for second harmonic generation of Nd:YAG laser and attests the enhancement of optical prpperties. Powder and single crystal XRD studies reveal that the grown γglycine crystal is having higher order of crystallinity. Thermal studies show the sample is thermally stable up to 270°C (elevated temperature) and this makes the grown crystal’s suitability for possible application in laser, where the material is required to with stand high temperatures. Dielectric studies of grown crystal confirm the improved optical quality. NLO studies of the grown sample show that the enhanced SHG efficiency is greater than KDP (1. 65 times) and Urea (1.63 times) crystals. The grown title compound was possessing various enhanced properties such as wide transparency range with 100% transmission, low dielectric constant value at higher frequency and hence improved optical quality with lesser defects and elevated decomposition temperature (270˚C) with greater SHG efficiency as that of KDP suggest that the grown γ-glycine crystals in the presence of 2-aminopyridine potassium chloride is a promising materials for optoelectronic applications. Acknowledgements The authors would like to thank Professor Dr. R. Jayavel, Director, Academic Research and Professor, Centre for Nanotechnology, Anna University, Chennai, for their providing facilities and the corresponding author thanks the UGC for providing financial support through Minor Project (No: F. MRP-5978/15/(MRP/UGC-SERO). References [1] S. Debrus, H. Ratajczak, J. Venturini, N. Pincon, J. Baran, J. Barycki, T. Glowiak, A. Pietraszko, Novel nonlinear optical crystals of noncentrosymmetric structure based on hydrogen bonds interactions between organic and inorganic, Synthetic Metals 127 (2002) 99 – 104.


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[2] Ch. Bosshard, K. Sutter, Ph. Pretre, J. Hulliger, M. Florsheimer, P. Kaatz, P. Gunter, organic Nonlinear optical materials, Gordon and Breach, Basel,1995. [3] M. C. Etter, J. Chem, Phy. 95 (1991) 4601. [4] C. B. Aakeroy, P. B. Hitchcock, B. D. Moyle, K. R. Seddon, J. Chem. Soc., Chem. Commun. (1989)1856. [5] C. B. Aakeroy, P. B. Hitchcock, B. D. Moyle, K. R. Seddon, J. Chem. Soc., Chem. Commun. (1992) 553. [6] M. Chao, E. Schemp and R. D. Rosenstein, Acta cryst. B31, (1975). 2922-2924 [7] D. S. Chemla, J. Zyss(Eds), Nonlinear optical optical properties of organic molecules and crystals, Academic press, New York,1987. [8] Yari S. Kivshar, Optics Express, 16, (2008)22126-22128 [9] B. K. Periyasamy, R. S. Jebas, and B. Thailampillai, Materials Letters, 61 (2007) 1489-1491. [10] K. P. Bhuvana, S. Robinson and T. Balasubramanian, Cryst. Res. Technol,45 (2010) 299-302 [11] Z. kotler, R. Hierle, D. Josse, J. Zyss, R. Masse, J. Opt. Soc. Am. B9(1992) 54 [12] Y. Lefur, M. Bagiue-Beucher, R. Masse, J. F. Nicoud, J. P. Levy, Chem. Mater. 8 (1996) 68. [13] H. Ratajczak, J. Baran, J. Barycki, S. Debrus, M. May, A. Pietraszko, H. M. Ratajczak, A. Tramer, J. Mol. Struct. 555 (2000) 149 [14] H. Ratajczak, , S. Debrus, M. May, J. Barycki, J. Baran, Bull. Pol. Acad. Sci. Chem. 48 (2000) 189. [15] Katsuyuki Auki, Kozo Pagano, Yoichi Iitaka, Acta Crystallogr. B 27 (1971) 11. [16] C. Razzetti, M. Ardoino, L. Zanotti, M. Zha, C. Paorici, Cryst. ResTechnol. 37(2002) 456 [17] R. Bairava Ganesh, V. Kannan, R. Sathyalakshmi, P. Ramasami, Mater. Lett. 61, (2007)706 [18] P. Andreazza, D. Josse, F. Lefaucheux, M. C. Robert, and J. Zyss (1992) Phys. Rev. B 45, 7640. [19] M. Narayan Bhat, S. M. Dharmaprakash, J. Crystal Growth. 236 (2002) 376 [20] R. Shanmugavadivu,G. Ravi, A. Nixon Azariah, j. phys. chem. solids 67 (2006) 1858. [21] N. Ashour, S. A. El-Kadry, Mahmoud, Thin Solid Films 269 (1995) 117–120. [22] K. Gupta Manoj, Sinha Niahi, Kumar Binay, Phys. B Condens. Matter 406 (2011) 63–67 [23] T. P. Srinivasan, R. Indirajith, R. Gopalakrishnan, J. Cryst. Growth 318 (2011)762-767. [24] S. Sankar, M. R. Manikandan, S. D. G. Ram, T. Mahalingam, G. Ravi, J. Cryst. Growth 312 (2010)2729-2733. [25] G. R. Dillip, P. Raghavaiah, C. Madhukar Reddy, G. Bhagavannaraya, V. Ramesh Kumar, B. Deva Prasad Raju, Spectrochimica Acta Part A 79 (2011) 1123-1127. [26] Jain John, P. Christuraj, K. Anitha, T. Balasubramanian "Materials Chemistry and Physics” Volume 118, Issues 2–3, 15 (2009) pp. 284–287. [27] M. Iyanar, J. Thomas Joseph Prakash, C. Muthamizhchelvan, S. Ponnusamy “Journal of Physical Sciences” Vol. 13 (2009) pp. 235-244. [28] C. Sekar, R. Parimaladevi “Journal of Optoelectronics and Biomedical Materials” Vol. 1, Issue 2, (2009), pp. 215–225. [29] R. Ashok Kumar, R. Ezhil Vizhi, N. Vijayan and D. Rajan Babu. , “Physica B” Volume 406, (2011) Pages 2594-2600. MMSE Journal. Open Access www.mmse.xyz

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[30] Balakrishnan, T., Ramesh Babu, R. and Ramamurthi, K. “Spectrochim. Acta Part A”Vol. 79(2008)pp. 1114-1118. [31] S. A. Martin Britto Dhas, S. Natarajan “ Optics Communications” Vol. 278, Issue 2, 15 (2007) pp 434–438. [32] J. Thomas Joseph Prakash, M. Lawrence, J. Felicita Vimala , M. Iyanar “Journal of Physical Sciences”, Vol. 14, 2010, 219-226. [33] G. R. Dillip, G. Bhagavannarayana, P. Raghavaiah, B. Deva Prasad Raju“Materials Chemistry and Physics” Volume 134 Issue 1 (2012)pp 371–376. [34] C. Sekar, R. Parimaladevi Spectrochimica Acta Part A, 74 (2009) 1160–1164. [35] K. Selvaraju, R. Valluvan, S. Kumararaman “Materials Letters” Vol. 70, Issue 23 (2006) pp 2848-2850. [36] S. Kalainathan, M. Beatrice Margaret, “Materials Science and Engineering: B” Vol. 120 (2005) pp. 190-193. [37] R. Srineevasan, R. Rajasekaran, “Journal of Molecular Structure”Vol. 1048 (2013) pp. 238-243. [38] R. Srineevasan, R. Rajasekaran, “JOAM” Vol. 16 (2014) pp. 65-69. [39] S. K. Kurtz and T. T. Perry, J. Appl. Phys. 39, (1968). 3798. [40] M. Narayana Bhat, S. M. Dharmaprakash, J. Cryst. Growth 242 (2002) 245. [41] K. Ambujam, S. Selvakumar, D. Prem Anand, G. Mohamed, P. Sagayaraj, Cryst. Res. Technol. 401 (2006) 671. Cite the paper R. Srineevasan, D. Sivavishnu, K. Arunadevi, R. Tamilselvi, J. Johnson, S. M. Ravi Kumar (2016). Enhancement of Optical and Thermal Properties of γ- Glycine Single Crystal: in the Presence of 2-Aminopyridine Potassium Chloride. Mechanics, Materials Science & Engineering, Vol 7. doi:10.13140/RG.2.2.33138.654


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Enhanced Mechanical Performance for Nacre-Inspired Polyimine Composites with Calcium Carbonate Particles6 Si Zhang1, Yanting Lv1, Jiayi Li1, Song Liang1,a and Zhenning Liu1,b 1 – Key Laboratory of Bionic Engineering (Ministry of Education), College of Biological and Agricultural Engineering, Jilin University, Changchun, Jilin 130022, P. R. China a – [email protected] b – [email protected] DOI 10.2412/mmse.81.85.882

Keywords: mechanical properties, polymer composites, polyimine, calcium carbonate (CaCO3), bio-inspired, reinforcement, nacre.

ABSTRACT. Polyimine is a novel functional thermoset material with several attractive functions. Yet the mechanical properties of polyimine-based composites have been rarely investigated. In this work, calcium carbonate (CaCO3), a cheap and commonly used reinforcing material, has been chosen as the reinforcing filler to form composites with polyimine through heat-pressing under mild conditions to mimic natural nacre. Elemental mapping shows that CaCO 3 particles are evenly distributed in the continuous network of the polyimine matrix. Then thermal analyses and mechanical measurements of hardness, tensile strength, toughness, bending strength, and impact strength have been conducted to characterize the properties of the resultant polyimine composites. The fracture surfaces of the specimens after tensile testing have also been examined by scanning electron microscopy (SEM). The polyimine composites with CaCO 3 particles demonstrate remarkable enhancement on multiple mechanical features, especially on tensile properties. More importantly, the polyimine composites fabricated with 6 wt% of CaCO 3 particles show simultaneous increases of tensile strength and toughness, which are 56% (from 35.75 to 55.79 MPa) and 110% (from 112.82 to 236.54 MJ/m3) respectively in comparison with the polyimine matrix. The work presented herein affords a facile and low-cost approach to enhance the mechanical properties of polyimine material for more practical applications.

Introduction. Reinforced polymer composites have attracted broad interest in recent years owing to their enhanced performance compared to the respective polymer matrix [1-10]. To this end, fillers such as calcium carbonate, zirconia, hydroxyapatite, have been added at low content to various polymers [11], and the resultant composites have demonstrated superior mechanical properties to meet different industrial demands [12]. Polyimine, also called Schiff base polymer, is a novel thermoset material with advantages of self-healing, recyclability and environmental friendliness. Moreover, such a material is often malleable at ambient conditions, holding a good promise for a range of industrial applications including automobile, electronics, medical, etc. [13-19]. However, reinforced polyimine composite has been rarely explored. Nacre, composed of inorganic particles (mainly of calcium carbonate, CaCO3) and biopolymers, is widely considered as a gold standard for the engineering of bionic composite with excellent strength and toughness [20]. It has been proposed that the CaCO3 platelets in natural nacre function to deflect cracks and mitigate localized stress [20]. Hence, a variety of polymer composites reinforced by CaCO3 particles have been prepared, which have exhibited remarkable improvements in mechanical properties such as tensile strength, stiffness, impact strength, bending strength and toughness [11, 12, 21-27].

© 2016 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/


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Inspired by natural nacre, we have envisioned that CaCO3 can be used as the reinforcing phase to enhance the mechanical performance of polyimine. Herein, the polyimine composites with varied contents of CaCO3 have been fabricated by heat-pressing the mixed powder of polyimine and CaCO3 particles. The resultant composites formed by imine metatheses have demonstrated simultaneous enhancements for both tensile strength and toughness, which are 56% and 109% respectively for the composite with 6% of CaCO3. A different optimal level of CaCO3 particles is required to achieve best performance for bending and impact resistance. The possible reinforcing mechanism is also discussed. Materials and Methods Experimental material. All the chemicals including terephthalaldehyde, diethylenetriamine, and triethylene tetramine were purchased from Aladdin Industrial Inc. (China). CaCO3 was purchased from Sinopharm Chemical Reagent Co., Ltd (China). All reagents were used as received without further purification. Preparation. The polyimine (PI) matrix was synthesized with terephthalaldehyde, diethylenetriamine, and triethylene tetramine according to the literature [18]. The obtained PI was milled into powder by pulverizer (QE-1OO, Yili Ltd., China), and then sifted by an 80-mesh sieve. The PI powder and CaCO3 particles were mixed by a ball miller for 1 hour. Then the mixed powders were heat-pressed by a thermocompressor (JYP-20) under 9 MPa at 80 °C to form polyimine composites. Characterization. A Rockwell hardometer (XHQ-150, Shanghai, China) was used to measure the hardness. Tensile tests and bending tests were performed with a Universal Testing Machine (Instron 1121, UK) according to ASTM standard D638 and D5023, respectively. The effective dimension for tensile test sample is 5 x 2 x 2 mm and the effective dimension for bending test sample is 35 x 5 x 4 mm. The crosshead speed for tensile tests and bending tests is 1 mm/min. The toughness was calculated by integrating the area of stress-strain curves. The impact strength was measured on a Charpy impact tester (XJ-40A, Wuzhong, China) with effective sample dimension of 35 x 5 x 4 mm. All the mechanical tests were carried out at room temperature. The average of at least 3 independent measurements was obtained for all mechanical characterization and the P value was calculated by the Student’s t-test. The differential scanning calorimetry (DSC) measurement was performed with a DSC instrument (Q20, TA, USA) in the temperature range of 30-150 °C at a heating rate of 5 °C /min. The thermogravimetric analysis (TGA) was conducted with a thermogravimetric analyzer (Q600, TA, USA) in the temperature range of 23-800 °C at a heating rate of 10 °C /min. Morphology characterization and elemental mapping. The tensile fracture surfaces of PI matrix and composites were observed by a scanning electron microscope (XL-30 ESEM FEG, FEI, USA). The elemental mapping was performed on Genesis 2000 (EDAX Company). Results and Discussion. The polyimine (PI) was synthesized according to the literature [18]. The sizes of PI powder and additive CaCO3 particles were measured as about 122±21 μm and 1.2±0.4 μm in diameter by Scanning Electron Microscopy (SEM) (Figure 1b and 1a). The PI composites with calcium carbonate (CaCO3) particles (PI-CC) were prepared by heat-pressing (80 °C, 9 MPa) the mixed powder of PI and CaCO3 particles (Figure 1e). The weight percentages of CaCO3 particles in the composites were 3%, 6%, 9%, 12% and 15%, which were subsequently denoted as PI-CC-3, PICC-6, PI-CC-9, PI-CC-12, and PI-CC-15 respectively. The original fracture SEM micrograph and elemental mapping micrograph were performed to verify the distribution of CaCO3 particles in the PI matrix (Figure 1c and 1d, the image was obtained with PI-CC-6). The yellow and green dots in the mapping graph (Figure 1d) represent calcium (corresponding to CaCO3) and nitrogen (corresponding to PI), respectively. SEM image of the fracture surface (Figure 1c) shows there are smooth areas with clear boundaries, among which rough areas exist. Comparing the SEM image with the corresponding elemental mapping graph, (Figure 1d) it is found the smooth areas contain only the PI, while the MMSE Journal. Open Access www.mmse.xyz

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rough areas consist of both PI and CaCO3. The existence of pure PI areas suggests that the CaCO3 particles can hardly penetrate into the PI powders during the heat-pressing. The distribution of CaCO3 particles among the pure PI areas proves that these particles work as the fillers in the composite matrix as our expectation.

Fig. 1. SEM micrographs of raw materials powder including CaCO3 particles (a) and PI (b). Fracture SEM micrograph (c) and elemental mapping (d) of Ca and N for the PI composite filled with 6 wt% CaCO3 particles. The yellow and green dots in (d) represent calcium and nitrogen, which indicate distribution of CaCO3 particles in the composite of PI-CC-6. Schematic illustration for preparing PI composite is shown in (e). Next, a range of mechanical measurements including hardness, tensile, bending, and impact strengths have been conducted to characterize the CaCO3-enhanced PI composites together with the control of PI matrix. It has been found that introducing CaCO3 into PI matrix results in little change of the overall hardness as the hardnesses of the composites remain comparable to that of the PI matrix (Table 1). MMSE Journal. Open Access www.mmse.xyz

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The tensile property measurement for the PI composites reveals a similar trend with a maximum value at 6 wt% of CaCO3 particles in terms of tensile strength, toughness, tensile modulus, and elongation at break (Figure 2 and Table 1). Specifically, the tensile strength exhibits a gradual increase from 35.75 MPa for the PI matrix to 55.79 MPa for the PI composite with 6 wt% of CaCO3 particles, which has been enhanced by 56% (Figure 2a and Table 1). Meanwhile, the toughness has also shown an increase of 109% from 112.82 MJ for the PI matrix to 236.54 MJ for the PI composite with 6 wt% of CaCO3 particles (Figure 2b and Table 1). Increasing the CaCO3 content beyond 6% results in a decline of tensile performance. The enhancement of tensile strength and toughness is significant (P