American Journal of Scientific Research ISSN 2301-2005 Issue 68 (2012), pp. 56-61 © EuroJournals Publishing, Inc. 2012 http://www.eurojournals.com/ajsr.htm
Experimental Study of Electrical Properties of (PVA- CoNO3, AgCO3) Composites Ahmed Hashim Babylon University, College of Education, Department of physics, Iraq E-mail:
[email protected] Abstract In present work, Composites of polyvinyl alcohol and silver carbonate, cobalt nitrite has been prepare by casting technique. The cobalt nitrite and silver carbonate were added to polyvinyl alcohol with different concentrations (0,2,4 and 6) wt.%. The electrical properties of composites were studied. The experimental results showed that the electrical conductivity increases with increase the cobalt nitrite and silver carbonate concentrations and temperature. Also the activation energy changes with increase of cobalt nitrite and silver carbonate concentrations.
Keywords: Polyvinyl alcohol, cobalt nitrite, Silver Carbonate, Electrical Conductivity.
Introduction Composites are made from two or more chemically distinct and insoluble phases materials that when combined are better (stronger, tougher, and/or more durable) than each would be separately. Polymeric composite materials are widely used in weight sensitive applications due to their high strength-to weight and stiffness-to-weight ratios compared with metallic materials. The weight and fuel savings offered by composite materials makes them attractive not only to the military, but also to the civilian aircraft, space, solar vehicles, and automobile industries[1]. Composites have good potential for various industrial fields because of their excellent properties such as high hardness, high melting point, low density, low coefficient of thermal expansion, high thermal conductivity, good chemical stability and improved mechanical properties such as higher specific strength, better wear resistance and specific modulus. Composites are used in making solar cells, optoelectronic device elements, laser diodes and light emitting diodes (LED), industrial applications in aircraft, military and car industry[2]. Plastics have been used in great demand nowadays. One of them, for example, is polystyrene which has been widely used for plastic packaging, electronic parts, furniture and expanded polystyrene foam (EPSF). Because of its unique properties such as insulation, low weight and sound absorber, it is then useful for interior decoration and exhibition as well as entertainment venues. In order to obtain good properties of the polymer composites, a number of considerations should be taken into account such as proper quantities, quality of dispersiveness[3] . Ibrahim in 2011[4] studied the electrical properties of (PS-CNPs ) composites. Results showed that the D.C electrical properties of composites increases suddenly by several order of magnitude at a critical concentration. The present work deals with the effect of cobalt nitrite and silver carbonate on the D.C electrical properties of polyvinyl alcohol.
Experimental Study of Electrical Properties of (PVA- CoNO3, AgCO3) Composites
57
Materials and Methods The materials used in this paper are polyvinyl alcohol and cobalt nitrite, silver carbonate. The weight percentages of cobalt nitrite and silver carbonate are (0,2,4 and 6)wt.%. The specimens were prepared using casting technique thickness ranged between (213-665)µm. The resistivity was measured over range of temperature from (30 to 80)oC using Keithly electrometer .The electrical conductivity ν was calculate by : 1 L (1) σ ν = ρ = RA
σ
v
Where : A = guard electrode effective area. R = volume resistance (Ohm) . L = average thickness of sample (cm) . The activation energy was calculated using equation : σ = σo exp(-Ea/kBT) σ = electrical conductivity at T temperature σ0 = electrical conductivity at absolute zero of temperature KB = Boltzmann constant Eact = Activation Energy
(2)
Results and Discussion Figure (1-a-b) shows the variation of electrical conductivity of PVA-CoNO3 and PVA-AgCO3 composites with cobalt nitrite and silver carbonate concentrations, respectively, at 30oC. The D.C conductivity is increasing with increase concentrations of the cobalt nitrite and silver carbonate. Figure 1-a: Variation of D.C electrical conductivity with CoNO3 wt.% concentration for (PVA-CoNO3) composite.
Conductivity(S/cm)
1.0E-10
1.0E-11
1.0E-12
1.0E-13 0
1
2
3
Con. of CoNOl3 wt.%
4
5
6
58
Ahmed Hashim
Figure 1-b: Variation of D.C electrical conductivity with AgCO3 wt.% concentration for (PVA-AgCO3) composite 5.1E-12
Conductivity(S/cm)
4.6E-12 4.1E-12 3.6E-12 3.1E-12 2.6E-12 2.1E-12 1.6E-12 1.1E-12 6.0E-13 0
1
2
3
4
5
6
Con. of AgCO3 wt.%
This increase is due to the effect of the space charge. The ions of cobalt nitrite and silver carbonate take the form of clusters or separated groups. The conductivity is increasing with the increase of the concentration of cobalt nitrite and silver carbonate as a result of the increase of the ionic charge carriers and the formation of a continuous network of cobalt nitrite and silver carbonate ions inside the composite. Consequently, the conductivity is increasing with the increase of cobalt nitrite and silver carbonate concentrations for PVA-CoNO3 and PVA-AgCO3. [5]. The variation of electrical conductivity of PVA-CoNO3 and PVA-AgCO3 composites at different temperature is shown in figure(1-a-b), respectively. The D.C conductivity increases with increase of the temperature, the increment in temperature provides an increase in free volume and segmental mobility. These two entities then permits free charges to top from one site to another thus increase conductivity. The conductivity increases so as temperature indicates more ions and electrons gained kinetic energy via., thermally activated hopping of charge carriers between trapped sites, which is temperature dependence. The sharp increase of D.C conductivity can be attributed to large heat energy absorbed by the samples and thus induce mobility of electrons. It is suggested that in this region, the hand gap between valence band and conduction band is reduce significantly and provide easiness for electrons to hopping from valence band to conduction band [6]. Figure 2-a: Variation of D.C electrical conductivity with temperature for(PVA-CoNO3) composite pure
Conductivity(S/cm)
1.0E-10
2 w t.% 4 w t.% 6 w t.%
1.0E-11
1.0E-12
1.0E-13 30
40
50
60
T(c)
70
80
Experimental Study of Electrical Properties of (PVA- CoNO3, AgCO3) Composites
59
Figure 2-b: Variation of D.C electrical conductivity with temperature for(PVA-AgCO3) composite
Figure(3) shows the variation of ln(conductivity) of PVA-CoNO3 and PVA-AgCO3 composites with inverted absolute temperature, respectively, using equation(2) was calculate activation energy, The high values of activation energy are attributed to the existence of free ions in the commercial polymers. By adding low concentrations of cobalt nitrite and silver carbonate, the values of the activation energy are decreasing for all samples as a result of the impact of space charge as shown in figure(4-a-b). The addition of low concentrations of cobalt nitrite and silver carbonate creates local energy levels in the forbidden energy gap which act as traps for charge carriers, which move by hopping among these levels[7]. Figure 3-a: Variation of D.C electrical conductivity with resprocal absoute temperature for( PVA-CoNO3) composite -23
ln(conductivity)
pure
-24
2 wt .% 4 wt .%
-25
6 wt .%
-26 -27 -28 -29 2.8
2.9
3
3.1
1000/T(K)
3.2
3.3
3.4
-1
ln(conductivity)
Figure3-b: Variation of D.C electrical conductivity with resprocal absoute temperature for (PVA-AgCO3) composite pure
-24 -24.5 -25 -25.5 -26 -26.5 -27 -27.5 -28 -28.5 -29
2 wt .% 4 wt .% 6 wt .%
2.8
2.9
3
3.1
1000/T(k)-1
3.2
3.3
3.4
60
Ahmed Hashim
By increasing the cobalt nitrite and silver carbonate concentrations, the activation energy decreases as a result of the increase of local centers [7]. Figur 4-a: Variation activation energy for D.C electrical conductivity with CoNO3 wt.% concentration for (PVA-CoNO3) composite 0.7 0.6
Ea(eV)
0.5 0.4 0.3 0.2 0.1 0 0
1
2
3
4
5
6
Con. of CoNO 3
Figure 4-b: Variation activation energy for D.C electrical conductivity with AgCO3 wt.% concentration for (PVA-AgCO3)composite 0.6 0.55
Ea(eV)
0.5 0.45 0.4 0.35 0.3 0
1
2
3
4
5
6
Con. Of AgCO3 wt.%
Conclusions 1. The D.C electrical conductivity of the polyvinyl alcohol increases by increasing cobalt nitrite and silver carbonate concentrations and temperature. 2. The activation energy of D.C electrical conductivity decreases by increasing cobalt nitrite and silver carbonate concentrations.
References [1]
[2]
Fahad A. Al-Zahrani, Ali A. Al-Masmoom, and U.A.Khashaba, 2009, " Impact of Polymers and Polymeric Composites on the Development of New Designs in Mechanical, Electrical, and Civil Engineering: A Review", MASAUM Journal Of Reviews and Surveys, Vol. 1, No.2, 184195 Canan AKSU CANBAY and Ayşe AYDOGDU, 2009, "Microstructure, Electrical and Optical Characterization of Zn0-NiO-SiO2 Nanocomposite Synthesized by Sol- Gel Technique", Turkish Journal of Science & Technology, Vol. 4, No 2, 121- 126.
Experimental Study of Electrical Properties of (PVA- CoNO3, AgCO3) Composites [3]
[4] [5] [6]
[7]
61
Chanin Kulsetthanchalee, Chanchai Thongpin, Supanat Phattarateera, and Poonsub Threepopnatkul, 2011, " THERMAL STABILITY AND FLAMMABILITY OF EXPANDED POLYSTYRENE FOAM USING MODIFIED NANOCLAY", Proceedings of the Conference of Multiphase Polymers and Polymer Composites: From Nanoscale to Macro Composites", Paris-Est, Creteil Uniersity, June, France. S.S. Ibrahim, 2011, "Low Percolation Behaviour of Polystyrene Carbon Nanoparticles PS/CNPs Composite", J. Mater. Environ. Sci. Vol.2 , No.2 , 118-127. Srivastava N. K. and Mehra R. M. , 2009," Study of electrical properties of polystyrene / foliated graphite composite", J.Materials Science- Poland, 27(1), Uni. Of Delhi South Campus. Ahmed M. S. and Zihilif A. M. , 1992, " The electrical conductivity of polypropylene and Nickel- Coated carbon Fiber composite ",J. Mater. Sc. 25(706), Uni of Jordan , Amman , Jordan. Hamzah M. , Saion E., Kassim A. and Yousuf M. , 2008, "Temperature dependence of AC Electrical conductivity of PVA-PPy-FeCl3 compositespolymer Films", MPJ., 3(2) : 24-31 , Malaysia.
