Title of Invention	"AN IMPROVED PROCESS FOR THE PREPARATION OF BOEHMITE/α-ALUMINA OR MIXTURE THEREOF"
Abstract	This invention relates to an improved process for the preparation of BNoehmite / a-alumina or mixture thereof. Boehmite and a-alumina are two ceramic materials widely used e.g. in making refractories, as technical ceramics, as electronic ceramics (substrates, picture tubes etc.) as abrasives, as alumina cutting tools with SiC whisker reinforcement and as fillers (pigments). The process steps are: subjecting hydrous aluminum compounds selected from alumina trihydrate, Boehmite, Gibbsite, bayerite, diaspore to a hydrothermal reaction at a temperature in the range of 300° - 550°C for a period in the range of 1-4 hrs. at an autogenous pressure in the range of 500 - 5000 Psi to obtain the desired product.

Title of Invention

"AN IMPROVED PROCESS FOR THE PREPARATION OF BOEHMITE/α-ALUMINA OR MIXTURE THEREOF"

Abstract

This invention relates to an improved process for the preparation of BNoehmite / a-alumina or mixture thereof. Boehmite and a-alumina are two ceramic materials widely used e.g. in making refractories, as technical ceramics, as electronic ceramics (substrates, picture tubes etc.) as abrasives, as alumina cutting tools with SiC whisker reinforcement and as fillers (pigments). The process steps are: subjecting hydrous aluminum compounds selected from alumina trihydrate, Boehmite, Gibbsite, bayerite, diaspore to a hydrothermal reaction at a temperature in the range of 300° - 550°C for a period in the range of 1-4 hrs. at an autogenous pressure in the range of 500 - 5000 Psi to obtain the desired product.

Full Text	This invention relates to an improved process for the preparation of Boehmite /a-alumina or mixture thereof. Boehmite and a-alumina are two ceramic materials widely used e.g. in making refractories, as technical ceramics, as electronic ceramics (substrates, picture tubes etc), as abrasives, as alumina cutting tools with SiC whisker reinforcement and as fillers(pigments). Due to its varied applications, alumina is used in a wide range of sizes and also in both fairly impure and high purity forms. There are presently about 30 varieties of alumina of size greater than 3µm marketed by the leading companies which process and market alumina as a product for various applications. Majority of alumina is produced commercially by the well-known Bayer's process which consists of crushing of Bauxite ore and its digestion with caustic soda in an autoclave to form sodium aluminate. Alumina trihydrate formed by hydrolysing the aluminate solution is finally converted to α-alumina by calcining it in a rotrary kiln above 1200°C. The temperature and time of calcination are selected to remove 'transition aluminas'. This method however yields coarse particles due to its high calcination temperature leading to coarsening (grain growth). The product also contains alkali impurities eg: Na2O,K2O which are harmful for its electronic and structural applications. The present invention is proposed as an improvement over the method mentioned in the earlier inventions of Newsome et al.(U.S. patent No.2,642,337 dated June 16 ,1953) and Misra (U.S. patent No.4,822,592 dated April 18 ,1989). In the Newsome's method alumina trihydrate is heated in contact with steam in the pressure range of about 350 -2500 Psi and at a temperature in the range of 400°-550°C, thereby converting the trihydrate to alumina. Misra's method was an improvement over Newsome's method by reducing the particle size of α-alumina by heating alumina trihydrate particles under pressure in fluidised bed in acidic steam media, thereby significantly reducing average crystallite size of a-alumina product to lie in the range of 1 - lOµm. The major drawbacks of the hitherto known processes are : 1. Use of external source of high pressure generation. 2. Use of catalysts, acidic steam etc. in the process decrease the life of the autoclave and increase the impurity level of the final product. 3. The high temperature calcination as mentioned in Bayer's process leads to coarsening of the final product. The main object of the present invention is to provide an improved process for the preparation of Boehmite/a-alumina or mixture thereof, which obviates the drawbacks of the hitherto known processes. Another object of the present invention is to provide an improved process wherein the reaction is carried out under autogenous hydrothermal conditions. Accordingly, the present invention provides an improved process for the preparation of Boehmite / a-alumina or mixture thereof which comprises : subjecting hydrous aluminum compounds selected from alumina trihydrate, Boehmite, Gibbsite, bayerite, diaspore to a hydrothermal reaction at a temperature in the range of 300° - 550°C for a period in the range of 1-4 hrs. at an autogenous pressure in the range of 500 - 5000 Psi to obtain the desired product. In an embodiment of the present invention the hydrous aluminum compounds used may be such as soluble hydrous aluminum compounds, hydrated aluminas. In another embodiment of the present invention the hydrated aluminas used may be such as alumina trihydrate, Boehmite, Gibbsite, Bayrite, Diaspore. In yet another embodiment of the present invention the hydro thermal reaction may be effected at a temperature in the range of 300° - 400°C for a period in the range of 1 - 4 hrs at an autogenous pressure in the range of 500 - 4000Psi to obtain Boehmite. In still another embodiment of the present invention the hydrothermal reaction may be effected at a temperature in the range of 450° - 550°C for a period in the range of 1 - 4 hrs at an autogenous pressure in the range of 500 - 5000 Psi to obtain a-alumina. In an embodiment of the improved process of the present invention the starting material used is Bayer's alumina trihydrate. The reduction of both particle size and alkali content of the starting Bayer's hydrate may be effected by known means such as attrition milling in aqueous medium. The hydrothermal reaction of the present invention is carried out by the self-generated pressure from the dehydrated water of the alumina trihydrate makes the process very simple by avoiding the requirement of external source for high pressure generation. Typical Bayer's Alumina trihydrate with an average particle size distribution (d50 = 80-100 µm) were used as the starting raw material for the preparation of α-alumina. An aqueous slurry of trihydrate was mechanically agitated in a blender for 10-20 minutes. During the agitation process, the superficially adsorbed alkali contents were leached out into the aqueous medium resulting in the increase of its pH. By repeated washing of the trihydrate, alkalis were removed till a neutral pH was obtained in the final washing. The washed trihydrate was further attrition milled for a period of 12hrs. in aqueous medium. The average particle size of the milled product as measured by a sedigraph (Micromeritics Inc. USA, Model 5100) was found in the range of 0.5-3.5µm. In the following examples the process of the present invention has been illustrated, however, these should not be construed to limit the scope of the present invention. Example 1. 42 grams of the attrited dry trihydrate ( average particle size d50 = 3.2µm- 3.5µm) was taken in an alumina container and charged into the autoclave. The above quantity of the trihydrate constitutes to about 90% volume of fill of the autoclave. It is sealed with a stainless steel gasket with a hole at the centre for communication of the reaction pressure to the Bourdon gauge. The autoclave is heated uniformly at the rate of 90° C using resistance heating. When the maximum set temperature of 550° C is reached it is controlled and maintained at 550° C ± 5° C for a soaking period of 4 hours after which the system is put off. At the end of the soaking period the pressure valve was opened and the pressure on the gauge is noted at this temperature and was found to be 1800 Psi. The autoclave was opened and the product is taken out along with the container. The pH of the residual water (13-15 cc) generated during hydrothermal dehydration was >10.5. The product was washed with hot dilute Hydrocholoric Acid and then repeatedly washed with deionised water till the final suspension was neutraL.lt was filtered and dried at 110°C for 24 hours. The weight of the final dried product was 27 grams and the product phase was found to be α-Alumina by XRD analysis. The average particle size (d50) of the product without gradation was found to be in the range of 5.0 µm. Example 2. 24 grams of the attrited dry trihydrate (d50= 3.2-3.5µm) was taken in an alumina container and the volume of fill of the autoclave for the above quantity was about 45%. After sealing the autoclave with a single hole stainless steel gasket, the autoclave was well insulated to prevent radial heat loss. The autoclave was heated to a maximum temperature of 550° C at the rate of 90° C per hour and soaked for 4hrs. The pressure was noted to be lOOOPsi. After maintaining at the maximum temperature for 4 hours, the autoclave was allowed to cool down and then opened to recover the product. White fluffy product was found in the container and the condensed water collected at the bottom of the autoclave with a pH>10.5 was separately collected(~ 7.5 ml) . The product was repeatedly washed with continous stirring till the final suspension displayed almost neutral pH. The product was dried at 110° C for 24 hours. The product was 100% a- alumina as per the XRD analysis. The average particle size (d50) without gradation was 1.5 µm . Example 3. 40 grams of attrited dry trihydrate is thoroughly mixed with water amounting to 50% of its weight and the pasty mass so obtained was taken as the reactant in the alumina container and charged into the autoclave. The autoclave was sealed in the same manner and well insulated as in previous examples. The maximum temperature of heating was set to 400°C with a soaking period of 4 hours at the maximum temperature. This temperature and soaking period was chosen to ensure complete conversion to Boehmite as well as to provide maximum time for diffusion of impurities from the lattice. The rate of heating upto the maximum temperature was maintained at 120° C per hour. The pressure at the maximum temperature was observed to be 2500 Psi. After soaking for 4 hours at the maximum temperature the autoclave was allowed to cool down and the product was recovered after opening the autoclave. White moist spongy product was found in the container with the residual water indicating a pH >10.5. The product was washed and dried as in Example 2 . The product phase in this case was found to be 100% Boehmite. The average particle size (d50) was found to be 1.32µm. The alkali content was found to be reduced considerably. Example 4 In another experiment 80 grams of the attrited dry trihydrate was used with 40 grams of water and the pasty mass so obtained was subjected to hydrothermal treatment with the same rate of heating of 120° C per hour to a maximum temperature of 400° C and a soaking period of 4 hours. The pressure at the maximum temperature was in the range of 5000 Psi The product obtained was treated well and dried as before. The product phase was 100% Boehmite and the average particle size (d50) was found to be 1.53 µm. Examples The Boehmite obtained in example 3 with particle size 1.32µm was used as a starting material for the second hydrothermal treatment. 30 grams of the Boehmite with 25 grams of deionised water and the pasty mass so obtained , is taken in an alumina container and subjected to hydrothermal treatment with a maximum temperature of 550° C and a soaking period of 4 hours as described in Example 1. Since additional water was used alongwith Boehmite the hydrothermal pressure generated was in the range of 2700 Psi. After the completion of soaking period the autoclave was cooled down and the product recovered. The pH of the residual water left was about 9. The product suspension was also slightly basic . The product was thoroughly washed with acidified deionised water and then with only deionised water repeatedly till the suspension had a neutral pH. It was filtered and dried at 110° C for 24 hours. Again the product was identified to be 100% α-alumina with an average particle size of (d50) of 3.44 µm. Example 6 The hydrothermal reaction s were repeated by taking 71 grams, of the pasty mass containing Boehmite and water in the ratio of 2:1, hydrothermal runs at the maximum temperature 550° C with a soaking period of 4 hours at the rate of 90° C per hour in all the cases .The final processed product was found to be 100% a-alumina in all the cases. While d50 for product , where 71 grams of the reactant was used was 3.4 µm it was 3.5 µm for 75 grams and 3.8µm for 91 grams of the reactant. The alkali content of the precursor ( alumina trihydrate ) and the final product a- alumina where analysed by an inductively coupled plasma analysis tecchnique. The results are tabulated as follows. Example7 In another experiment 86 grams of the attrited dry trihydrate was mixwd with 38 grams of water and the pasty mass so obtained was subjected to hydrothermal treatment with the same rate of heating of 120° C per hour to a maximum temperature of 450°C and soaked for 75 minutes. The pressure at the maximum temperature was found to be 5000 Psi.The product obtained was treated well and dried as before. The product was analysed by XRD and was found to be a mixture of α-alumina and boehmite. (Table Removed) It can be observed that alkali content specifically Na2O content has decreased appreciably from 0.34% in alumina trihydrate to 0.015% in the final product. We Claim: 1. An improved process for the preparation of Boehmite / α-alumina or mixture thereof which comprises; subjecting hydrous aluminum compounds selected from alumina trihydrate, Boehmite, Gibbsite, bayerite, diaspore to a hydrothermal reaction at a temperature in the range of 300° - 550°C for a period in the range of 1-4 hrs. at an autogenous pressure in the range of 500 - 5000 Psi to obtain the desired product. 2. An improved process as claimed in claim 1. wherein the hydrothermal reaction is effected at a temperature in the range of 300° - 400°C for a period in the range of 1 - 4 hrs at an autogeneous pressure in the range of 500 - 4000Psi to obtain Boehmite. 3. An improved process as claimed in claim 1 wherein the hydrothermal reaction is effected at temperature in the range of 450° - 550°C for a period in range of 1-4 hrs at autogeneous pressure in the range of 500 - 5OOOPsi to obtain a-alumina. 4. An improved process for the preparation of Boehmite/α-alumina or mixture thereof substantially as herein described with reference to the example.

Full Text

This invention relates to an improved process for the preparation of Boehmite /a-alumina or mixture thereof.
Boehmite and a-alumina are two ceramic materials widely used e.g. in making refractories, as technical ceramics, as electronic ceramics (substrates, picture tubes etc), as abrasives, as alumina cutting tools with SiC whisker reinforcement and as fillers(pigments). Due to its varied applications, alumina is used in a wide range of sizes and also in both fairly impure and high purity forms. There are presently about 30 varieties of alumina of size greater than 3µm marketed by the leading companies which process and market alumina as a product for various applications.
Majority of alumina is produced commercially by the well-known Bayer's process which consists of crushing of Bauxite ore and its digestion with caustic soda in an autoclave to form sodium aluminate. Alumina trihydrate formed by hydrolysing the aluminate solution is finally converted to α-alumina by calcining it in a rotrary kiln above 1200°C. The temperature and time of calcination are selected to remove 'transition aluminas'. This method however yields coarse particles due to its high calcination temperature leading to coarsening (grain growth). The product also contains alkali impurities eg: Na2O,K2O which are harmful for its electronic and structural applications.
The present invention is proposed as an improvement over the method mentioned in the earlier inventions of Newsome et al.(U.S. patent No.2,642,337 dated June 16 ,1953) and Misra (U.S. patent No.4,822,592 dated April 18 ,1989). In the Newsome's method alumina trihydrate is heated in contact with steam in the pressure range of about 350 -2500 Psi and at a temperature in the range of 400°-550°C, thereby converting the trihydrate to alumina. Misra's method was an improvement over Newsome's method by reducing the particle size of α-alumina by heating alumina trihydrate particles under pressure in fluidised bed in acidic steam media, thereby significantly reducing average crystallite size of a-alumina product to lie in the range of 1 - lOµm.
The major drawbacks of the hitherto known processes are :
1. Use of external source of high pressure generation.
2. Use of catalysts, acidic steam etc. in the process decrease the life of the autoclave and
increase the impurity level of the final product.
3. The high temperature calcination as mentioned in Bayer's process leads to coarsening
of the final product.
The main object of the present invention is to provide an improved process for the preparation of Boehmite/a-alumina or mixture thereof, which obviates the drawbacks of the hitherto known processes.

Another object of the present invention is to provide an improved process wherein the reaction is carried out under autogenous hydrothermal conditions.
Accordingly, the present invention provides an improved process for the preparation of Boehmite / a-alumina or mixture thereof which comprises : subjecting hydrous aluminum compounds selected from alumina trihydrate, Boehmite, Gibbsite, bayerite, diaspore to a hydrothermal reaction at a temperature in the range of 300° - 550°C for a period in the range of 1-4 hrs. at an autogenous pressure in the range of 500 - 5000 Psi to obtain the desired product.
In an embodiment of the present invention the hydrous aluminum compounds used may be such as soluble hydrous aluminum compounds, hydrated aluminas.
In another embodiment of the present invention the hydrated aluminas used may be such as alumina trihydrate, Boehmite, Gibbsite, Bayrite, Diaspore.
In yet another embodiment of the present invention the hydro thermal reaction may be effected at a temperature in the range of 300° - 400°C for a period in the range of 1 - 4 hrs at an autogenous pressure in the range of 500 - 4000Psi to obtain Boehmite.
In still another embodiment of the present invention the hydrothermal reaction may be effected at a temperature in the range of 450° - 550°C for a period in the range of 1 - 4 hrs at an autogenous pressure in the range of 500 - 5000 Psi to obtain a-alumina.

In an embodiment of the improved process of the present invention the starting material used is Bayer's alumina trihydrate. The reduction of both particle size and alkali content of the starting Bayer's hydrate may be effected by known means such as attrition milling in aqueous medium. The hydrothermal reaction of the present invention is carried out by the self-generated pressure from the dehydrated water of the alumina trihydrate makes the process very simple by avoiding the requirement of external source for high pressure generation.
Typical Bayer's Alumina trihydrate with an average particle size distribution (d50 = 80-100 µm) were used as the starting raw material for the preparation of α-alumina. An aqueous slurry of trihydrate was mechanically agitated in a blender for 10-20 minutes. During the agitation process, the superficially adsorbed alkali contents were leached out into the aqueous medium resulting in the increase of its pH. By repeated washing of the trihydrate, alkalis were removed till a neutral pH was obtained in the final washing. The washed trihydrate was further attrition milled for a period of 12hrs. in aqueous medium. The average particle size of the milled product as measured by a sedigraph (Micromeritics Inc. USA, Model 5100) was found in the range of 0.5-3.5µm.
In the following examples the process of the present invention has been illustrated, however, these should not be construed to limit the scope of the present invention.

Example 1.
42 grams of the attrited dry trihydrate ( average particle size d50 = 3.2µm- 3.5µm) was taken in an alumina container and charged into the autoclave. The above quantity of the trihydrate constitutes to about 90% volume of fill of the autoclave. It is sealed with a stainless steel gasket with a hole at the centre for communication of the reaction pressure to the Bourdon gauge. The autoclave is heated uniformly at the rate of 90° C using resistance heating. When the maximum set temperature of 550° C is reached it is controlled and maintained at 550° C ± 5° C for a soaking period of 4 hours after which the system is put off. At the end of the soaking period the pressure valve was opened and the pressure on the gauge is noted at this temperature and was found to be 1800 Psi. The autoclave was opened and the product is taken out along with the container.
The pH of the residual water (13-15 cc) generated during hydrothermal dehydration was >10.5. The product was washed with hot dilute Hydrocholoric Acid and then repeatedly washed with deionised water till the final suspension was neutraL.lt was filtered and dried at 110°C for 24 hours. The weight of the final dried product was 27 grams and the product phase was found to be α-Alumina by XRD analysis. The average particle size (d50) of the product without gradation was found to be in the range of 5.0 µm.

Example 2.
24 grams of the attrited dry trihydrate (d50= 3.2-3.5µm) was taken in an alumina container and the volume of fill of the autoclave for the above quantity was about 45%. After sealing the autoclave with a single hole stainless steel gasket, the autoclave was well insulated to prevent radial heat loss. The autoclave was heated to a maximum temperature of 550° C at the rate of 90° C per hour and soaked for 4hrs. The pressure was noted to be lOOOPsi.
After maintaining at the maximum temperature for 4 hours, the autoclave was allowed to cool down and then opened to recover the product. White fluffy product was found in the container and the condensed water collected at the bottom of the autoclave with a pH>10.5 was separately collected(~ 7.5 ml) . The product was repeatedly washed with continous stirring till the final suspension displayed almost neutral pH. The product was dried at 110° C for 24 hours. The product was 100% a- alumina as per the XRD analysis. The average particle size (d50) without gradation was 1.5 µm .
Example 3.
40 grams of attrited dry trihydrate is thoroughly mixed with water amounting to 50% of its weight and the pasty mass so obtained was taken as the reactant in the alumina container and charged into the autoclave. The autoclave was sealed in the same manner and well insulated as in previous examples. The maximum temperature of heating was set

to 400°C with a soaking period of 4 hours at the maximum temperature. This temperature and soaking period was chosen to ensure complete conversion to Boehmite as well as to provide maximum time for diffusion of impurities from the lattice. The rate of heating upto the maximum temperature was maintained at 120° C per hour. The pressure at the maximum temperature was observed to be 2500 Psi. After soaking for 4 hours at the maximum temperature the autoclave was allowed to cool down and the product was recovered after opening the autoclave. White moist spongy product was found in the container with the residual water indicating a pH >10.5. The product was washed and dried as in Example 2 . The product phase in this case was found to be 100% Boehmite. The average particle size (d50) was found to be 1.32µm. The alkali content was found to be reduced considerably.
Example 4
In another experiment 80 grams of the attrited dry trihydrate was used with 40 grams of water and the pasty mass so obtained was subjected to hydrothermal treatment with the same rate of heating of 120° C per hour to a maximum temperature of 400° C and a soaking period of 4 hours. The pressure at the maximum temperature was in the range of 5000 Psi The product obtained was treated well and dried as before. The product phase was 100% Boehmite and the average particle size (d50) was found to be 1.53 µm.

Examples
The Boehmite obtained in example 3 with particle size 1.32µm was used as a starting material for the second hydrothermal treatment. 30 grams of the Boehmite with 25 grams of deionised water and the pasty mass so obtained , is taken in an alumina container and subjected to hydrothermal treatment with a maximum temperature of 550° C and a soaking period of 4 hours as described in Example 1. Since additional water was used alongwith Boehmite the hydrothermal pressure generated was in the range of 2700 Psi. After the completion of soaking period the autoclave was cooled down and the product recovered. The pH of the residual water left was about 9. The product suspension was also slightly basic . The product was thoroughly washed with acidified deionised water and then with only deionised water repeatedly till the suspension had a neutral pH. It was filtered and dried at 110° C for 24 hours. Again the product was identified to be 100% α-alumina with an average particle size of (d50) of 3.44 µm.
Example 6
The hydrothermal reaction s were repeated by taking 71 grams, of the pasty mass containing Boehmite and water in the ratio of 2:1, hydrothermal runs at the maximum temperature 550° C with a soaking period of 4 hours at the rate of 90° C per hour in all the cases .The final processed product was found to be 100% a-alumina in all the cases. While d50 for product , where 71 grams of the reactant was used was 3.4 µm it was 3.5 µm for 75 grams and 3.8µm for 91 grams of the reactant.

The alkali content of the precursor ( alumina trihydrate ) and the final product
a- alumina where analysed by an inductively coupled plasma analysis tecchnique. The
results are tabulated as follows.
Example7
In another experiment 86 grams of the attrited dry trihydrate was mixwd with 38 grams of water and the pasty mass so obtained was subjected to hydrothermal treatment with the same rate of heating of 120° C per hour to a maximum temperature of 450°C and soaked for 75 minutes. The pressure at the maximum temperature was found to be 5000 Psi.The product obtained was treated well and dried as before. The product was analysed by XRD and was found to be a mixture of α-alumina and boehmite.
(Table Removed)
It can be observed that alkali content specifically Na2O content has decreased appreciably from 0.34% in alumina trihydrate to 0.015% in the final product.

We Claim:
1. An improved process for the preparation of Boehmite / α-alumina or mixture thereof
which comprises; subjecting hydrous aluminum compounds selected from alumina
trihydrate, Boehmite, Gibbsite, bayerite, diaspore to a hydrothermal reaction at a
temperature in the range of 300° - 550°C for a period in the range of 1-4 hrs. at an
autogenous pressure in the range of 500 - 5000 Psi to obtain the desired product.
2. An improved process as claimed in claim 1. wherein the hydrothermal reaction is
effected at a temperature in the range of 300° - 400°C for a period in the range of 1 - 4

hrs at an autogeneous pressure in the range of 500 - 4000Psi to obtain Boehmite.
3. An improved process as claimed in claim 1 wherein the hydrothermal reaction is effected
at temperature in the range of 450° - 550°C for a period in range of 1-4 hrs at
autogeneous pressure in the range of 500 - 5OOOPsi to obtain a-alumina.
4. An improved process for the preparation of Boehmite/α-alumina or mixture thereof
substantially as herein described with reference to the example.

Documents:

1969-del-1998-abstract.pdf

1969-del-1998-claims.pdf

1969-del-1998-correspondence-others.pdf

1969-del-1998-correspondence-po.pdf

1969-del-1998-description (complete).pdf

1969-del-1998-form-1.pdf

1969-del-1998-form-19.pdf

1969-del-1998-form-2.pdf

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Patent Number

215684

Indian Patent Application Number

1969/DEL/1998

PG Journal Number

12/2008

Publication Date

21-Mar-2008

Grant Date

29-Feb-2008

Date of Filing

10-Jul-1998

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI -100 001, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	MR. PRASANTA KUMAR PANDA	SCIENTISTS IN MATERIALS SCIENCE DIVISION, NATIONAL AEROSPACE LABORATORIES, BANGALORE - 560 017, INDIA
2	MR. VELLORE ABDUL JALEEL	SCIENTISTS IN MATERIALS DIVISION, NATIONAL AEROSPACE LABORATORIES, BANGALORE - 560 017, INDIA.
3	DR. THANDALI SRINIVASAN KANNAN	SCIENTISTS IN MATERIALS DIVISION, NATIONAL AEROSPACE LABORATORIES, BANGALORE - 560 017, INDIA

PCT International Classification Number

B01J 13/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA