study of pva binder removal by using tg-dta

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Thermo Gravimetric-Differential Thermal Analysis (TG-DTA) experiments of Pure ... Fig-1 shows TG-DTA analysis Pure PVA, mixture of lithium hydroxide and ...

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

Mandal et al. [3, 4] have developed the solid state reaction process for the synthesis and fabrication of pebbles of ceramic solid breeder materials viz., lithium titanate and lithium orthosilicate. The process consists of unit operations: grinding, mixing, classification, calcinations, kneading, extrusion, spherodization and sintering. The lithium titanate pebble required specific density and porosity for high tritium release rate and to maintain density. The kneading operation involves mixing of aqueous solution of Poly Vinyl Alcohol (PVA) and lithium titanate powder. Aqueous PVA solution is used in extrusion process to achieve mechanical strength, porosity and density in the pebble. Thermo Gravimetric-Differential Thermal Analysis (TG-DTA) experiments of Pure PVA, mixture of lithium hydroxide and titanium dioxide with PVA binder and powder mixture of lithium hydroxide with titanium dioxide were carried out at 40ml Nitrogen flow rate. Fig-1 shows TG-DTA analysis Pure PVA, mixture of lithium hydroxide and titanium dioxide with PVA binder and powder mixture of lithium hydroxide with titanium dioxide. TG-DTA pure PVA shows four endothermic DTA 0 0 0 peaks. First DTA two peaks at 140 C and 200 C are due to dehydration and melting. The DTA peak at 320 C for boiling 0 and at 400 C for decomposition.TG-DTA of mixture of lithium hydroxide with titanium dioxide shows two endothermic 0 0 peaks. First peak at 200 C is due to dehydration of lithium monohydrate and second endothermic 488 C due to the reaction lithium hydroxide and titanium dioxide. TG-DTA of mixture of lithium hydroxide and titanium dioxide with PVA 0 0 binder shows two endothermic peaks. First peak at 400 C is due to PVA removal and second endothermic 488 C due to the reaction lithium hydroxide and titanium dioxide.

th

68 Annual Session of Indian Institute of Chemical Engineers, 27-30 December | Guwahati, India

Lithium titanate (Li2TiO3) is considered as one of the promising ceramic breeding material for the Test Blanket Module (TBM) of ITER type reactor and for the future fusion reactors. This is due its high lithium content; which gives higher tritium production rate, high tritium release rate (i.e., low retention time), high thermal and chemical stability, high mechanical stability under irradiation, high thermal conductivity etc.

Fig-1 shows TG-DTA analysis Pure PVA, mixture of lithium hydroxide and titanium dioxide with PVA binder and powder mixture of lithium hydroxide with titanium dioxide

From all TG-DTA experiments it is observed that the optimum temperature for PVA removal from mixing of Poly Vinyl 0 Alcohol (PVA) solution and lithium titanate powder of is about 400 C.

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

References [1] D. Mandal, M.R.K Shenoi, S.K. Ghosh, Fusion Engineering and Design, 85, 2010, 819-823 [2] D. Mandal, Sathiyamoorthy, V.G. Rao, Fusion Engineering and Design, 87 2012, 7-12

Lithium titanate (Li2TiO3) is considered as one of the promising ceramic breeding material for the Test Blanket Module (TBM) of ITER DEMO and for the future fusion reactors [1]. This is due its high lithium content; which gives higher tritium production rate, high tritium release rate (i.e., low retention time), high thermal and chemical stability, high mechanical stability under irradiation, high thermal conductivity etc. Mandal et al. [2, 3] have developed the solid state reaction process for the synthesis and fabrication of pebbles of ceramic solid breeder materials viz., lithium titanate (

) and lithium orthosilicate (

). The process

consists of unit operations: grinding, mixing, classification, calcinations, kneading, extrusion, spherodization and sintering. The lithium titanate pebble required specific density and porosity for high tritium release rate and to maintain density. The kneading operation involves mixing of aqueous solution of Poly Vinyl Alcohol (PVA) and lithium titanate powder. Aqueous PVA solution is used in extrusion process to act as a binder to achieve adequate mechanical strength of green pebbles and desired porosity and density in the sintered pebbles.

Thermo Gravimetric-Differential Thermal Analysis (TG-DTA) experiments of pure PVA, mixture of lithium hydroxide and titanium dioxide with PVA solution and powder mixture of lithium hydroxide with titanium dioxide were carried out at 40 ml/min nitrogen gas flow rate. The lithium titanate pebbles were fabricated and sintered by using lithium hydroxide and titanium dioxide through direct process route. The achieved true density and porosity of pebbles after 5 h at temperature of

was 3.23

/

and 33 % respectively. The results of

TG-DTA experiments and sintering behavior are discussed in this paper.

Keywords: Fusion Reactor, lithium titanate, solid state reaction, Thermo Gravimetric and Differential Thermal Analysis (TG-DTA), Powder X-Ray Diffraction (PXRD). ___________________________________________________________________________

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

1.0 Introduction Lithium titanate

is considered as one of the promising ceramic solid breeding material for the Test

Blanket Module (TBM) of Indian TBM programme, ITER demo reactor and for the future fusion reactors. This is due its high lithium content; which gives higher tritium production rate, high tritium release rate (i.e., low retention time), high thermal and chemical stability, high mechanical stability under irradiation, high thermal conductivity etc. [1-3]. Mandal et al. [2, 3] have developed a solid state reaction process for the synthesis and fabrication of pebbles of ceramic solid breeder materials viz., lithium titanate by using lithium carbonate ( dioxide

) and titanium

) as raw materials. The process consists of seven unit operations; viz., (i) grinding, (ii) mixing, (iii)

classification, (iv) calcination, (v) kneading with PVA binder (vi) extrusion, (vii) spherodization and (vii) sintering. Mandal et al. has studied feasibility direct process route for synthesis lithium titanate pebble through sequential unit operations: grinding, classification, mixing, extrusion, spherodization, calcinations and sintering. It is observed that density of pebble decrease with increase sintering temperature and time. This is due to the release of carbon dioxide gas from the pebbles, during the reaction of lithium carbonate and titanium dioxide.

It was found that lithium hydroxide can be used as a raw material instead of lithium carbonate for the synthesis

Li2TiO3. The advantage of the use of lithium hydroxide instead of lithium carbonate is that, it can eliminate the

decomposition of lithium carbonate which produces carbon-dioxide, the greenhouse gas. The lithium titanate pebble

can be synthesized using lithium hydroxide and titanium dioxide through direct process route through sequential uni

operations: mixing, grinding, extrusion, spherodization, calcinations and sintering. Thermo Gravimetric-Differentia

Thermal Analysis (TG-DTA) experiments of Pure PVA, mixture of lithium hydroxide and titanium dioxide with

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

PVA binder and powder mixture of lithium hydroxide with titanium dioxide were carried out at 40ml Nitrogen flow

rate. The lithium titanate pebble synthesized using lithium hydroxide and titanium dioxide through direct process

route through sequential unit operations: mixing, grinding, extrusion, spherodization, calcinations and sintering. The densification behavior studied was at temperature of

.

2.0 Materials, Methods of Experiments, Results & Discussion : 2.1 Materials 99.9 % pure

(SD Fine Chem. make), 99.9 % pure

(SD Fine Chem. make), 99.9 %

(Loba

Chem. make) and PVA powder were used. 2.2 TG-DTA Experiments of Raw Material Mixture 99.9 % pure

with 99.9 %

and 99.9 % pure

with 99.9 %

sample mixture are

prepared for experiments. TG-DTA of both the mixtures were carried out in TG-DTA instruments (Make: Netzsch, Model: STA 449 Jupiter F3) at 40 ml/min nitrogen flow rate. Fig.1 shows TG-DTA of mixture of lithium carbonate with titanium dioxide and Fig. 2 shows TG-DTA of mixture of lithium hydroxide with titanium dioxide. The DTA peak for mixture lithium carbonate with titanium dioxide was found at was found at complete at

C temperature. The DTA peak for mixture lithium hydroxide with titanium dioxide

C temperature. TG curve of Fig.1 shows that the major mass loss starts at C, while TG curve of Fig.2 shows that the major mass loss starts at

C and

C and complete at

C.Hence, it may be concluded that the reaction temperature for mixture lithium hydroxide and titanium dioxide was found to be dioxide which is

.

which is lower than that of the mixture of lithium carbonate with titanium

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

Fig.1: TG-DTA analysis of mixture of lithium carbonate with titanium dioxide from sample set-1 at 5 0C/min heating rate form 30-1000 0C temperature

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

Fig.2: TG-DTA analysis of mixture of lithium hydroxide with titanium dioxide at 20 0C/min heating rate form 30-1000 0C temperature

2.3 Mixing Experiment for synthesis of single phase lithium titanate From TG-DTA study it was observed that the reaction temperature of synthesis of lithium titanate using lithium hydroxide lower, but the single phase formation of lithium titanate must be confirmed. Hence,

and

were mixed with helical turbo mixer for 2.5 h and sample from mixture heated at 500 0C in tubular furnace for time duration 8 h. The sample was analyzed for PXRD analysis. Fig.3 shows PXRD analysis of sample and it shows un-reacted titanium dioxide observed. The mixing was inadequate due to hygroscopic nature of lithium hydroxide. The run for mixing with ball mill has been carried out, but very hard lump observed in ball mil.

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

Hence, several trials were carried out with helical turbo mixer followed ball mill and the lumps were not observed after ball mill at low speed. The mixing parameter was optimized i.e., both the reactant were mixed in helical turbo mixer for 2.5 h followed by ball mill mixing at low RPM i.e. 50 RPM for 10 minute. The PXRD analyses shown in Fig. 4 confirm that single phase of lithium titanate.

Fig.3: Powder X-Ray diffraction pattern of sample from mixture (mixed with helical turbo mixer for 2.5 h) sample of lithium hydroxide and titanium dioxide heated at temperature of 5000C for 8 h time duration

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

Fig.4: Powder XRay diffraction pattern of sample from mixture (mixed in helical turbo mixer for 2.5 h followed by ball mill mixing at low RPM i.e. 50 RPM for 10 minute) sample of lithium hydroxide and titanium dioxide heated at temperature 500 0C for 8h

2.4 TG-DTA study for PVA Removal Thermo Gravimetric-Differential Thermal Analysis (TG-DTA) experiments of Pure PVA, mixture of lithium hydroxide and titanium dioxide with PVA binder and powder mixture of lithium hydroxide with titanium dioxide were carried out at 40ml Nitrogen flow rate. Fig.5 shows TG-DTA

analysis Pure PVA, mixture of lithium

hydroxide and titanium dioxide with PVA binder and powder mixture of lithium hydroxide with titanium dioxide. TG-DTA pure PVA shows four endothermic DTA peaks. First DTA two peaks at 140 0C and 200 0C are due to dehydration and melting. The DTA peak at 320 0C for boiling and at 400 0C for decomposition.TG-DTA of mixture of lithium hydroxide with titanium dioxide shows two endothermic peaks. First peak at 200 0C is due

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

to dehydration of lithium monohydrate and second endothermic 488 0C due to the reaction lithium hydroxide and titanium dioxide. TG-DTA of mixture of lithium hydroxide and titanium dioxide with PVA binder shows three endothermic peaks. First peak at 200 0C is due to dehydration, 400 0C is due to PVA removal and second endothermic 488 0C due to the reaction lithium hydroxide and titanium dioxide. From TG-DTA experiments it is observed that the optimum temperature for PVA removal from mixing of Poly Vinyl Alcohol (PVA) solution and lithium titanate powder of is about 400 0C.

Fig.5: TG-DTA analysis Pure PVA, mixture of lithium hydroxide and titanium dioxide with PVA binder and powder mixture of lithium hydroxide with titanium dioxide

2.5 Direct Synthesis of Lithium Titanate Pebbles

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

The lithium titanate pebbles were synthesized using lithium hydroxide and titanium dioxide through direct process route. The pebble synthesized through mixing, kneading, extrusion, spherodization process route and dried in fluid bed dryer. The pebbles were kept for 1 h at hydroxide. The temperature further increased up to 400

for removal binded moisture of lithium

for PVA removal. The pebbles were calcined at 500

reaction temperature for 5 h. The all above operating parameter were decided by using the above results. The calcined pebbles were sintered at temperature

for different time. Density of the sintered pebbles was

analyzed by using He-Pycnometer and porosity of sintered pebbles, after 5 h were analyzed using Hg-Porosity meter. Fig 6 shows that the density of pebble decreases with sintering time become steady state after 5hr. This decrease in density pebble is due to loss of trapped PVA taped in the pores of pebble. The achieved true density pebble after 5 h at temperature temperature

is about 3.23 gm/cc. The open and close porosity of pebble after 5 h at

is about 23 % and 9.5 % respectively. Fig.7 shows TG-DTA analysis of sintered pebble up to

1400 0C temperature. The mass loss is not observed in sintered pebble after

5 h at temperature of

.

Fig.8 shows XRD analysis of lithium titanate powder prepared from sintered pebble after 5 h at temperature The direct synthesis of lithium titanate pebble by using lithium hydroxide and titanium dioxide is feasible process. The PVA removal steps control the density and porosity of pebble.

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

3.55 0

900 C

-1

True Density [gm cc ]

3.50 3.45 3.40 3.35 3.30 3.25 3.20 0

1

2

3

4

5

6

7

8

9

Time (hr)

Fig.6: Variation of True density of lithium titanate pebble with time sintered at temperature

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

Fig.7:TG-DTA analysis of sintered pebble up to 1400 0C temperature.

Fig.8 :XRD analysis of lithium titanate powder prepared from sintered pebble after 5h at temperature 3.0 Conclusions

The reaction temperature for mixture lithium hydroxide and titanium dioxide was found to be lower than that of the mixture of lithium carbonate with titanium dioxide which is

which is

. Gibbs. It confirms that

the reaction of lithium hydroxide with titanium dioxide is more feasible than the reaction of lithium carbonate with titanium dioxide. From TG-DTA experiments it is observed that the optimum temperature for PVA removal from mixing of Poly Vinyl Alcohol (PVA) solution and lithium titanate powder of is about 400 0C.

AM 007

STUDY OF PVA BINDER REMOVAL BY USING TG-DTA *

N. S. Ghuge , D. Mandal 1

Chemical Engineering Division, Bhabha Atomic Research Centre, Tomboy, Mumbai-85, India

*

[ Corresponding author: Tel.: +91 22 25594929; FAX: +91 2225505151.E-mail: [email protected]]

The lithium titanate pebbles were synthesized using lithium hydroxide and titanium dioxide through direct process route. The achieved true density and porosity of pebble after 5 h at temperature

is about 3.23

gm/cc and 33 % respectively. The PVA removal steps control the density and porosity of pebble.

In future, synthesis of pebble though direct process route and effect of PVA concentration in solution, effect of % PVA solution as binder during extrusion on density, open & close porosity, grain size etc. will be studied.

Acknowledgments The authors are thankful to Shri K T Shenoy, Head, Chemical Engineering Division, BARC for his suggestion and help in this work. The authors are thankful to Shri M.C. Jadeja, Shri B.K. Chougule, Shri Deepak Avhad, Shri C. A. Shinde, Shri Ravi Rathore and Shri Santosh Sarang of the Materials Section of Chemical Engineering Division, BARC for their constant assistance in this work.

References [1]

Gierszewski P., Fusion Eng. Design. 39–40, (1998), 739–743

[2]

Mandal D., Shenoi M.R.K., Ghosh S.K., Fusion Eng. Design, 85 (2010), 819-823.

[3]

Mandal D., Sathiyamoorthy D., Rao V.G., Fusion Eng. Design, 87 (2012), 7-12.

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