Title of Invention	" A PROCESS FOR THE PREPARATION OF ALUMINUM NITRIDE-SILICON CARBIDE REINFORCED CERAMIC FIBER USEFUL FOR MAKING METAL OR CERAMIC MATRIX COMPOSITES."
Abstract	This invention relates to a process for the preparation of Aluminium nitride - Silicon carbide reinforced ceramic fiber useful for metal and ceramic matrix composites which comprises: i) treating the raw rice husk with 3 to 6N HCl for a period of 30 to 90 minutes, filtering and washing with distilled water, adding 5 to 10% NaOH solution filtering and washing with distilled water to obtain cleaned raw rice husk, ii) drying the cleaned raw rice husk at a temperature range of 90 to 110°C for a period in the range of 10 to 14 hours, iii) charring the cleaned, and dried raw rice husk at a temperature in the range of 300 to 700°C, for a period of 1 to 5 hrs., iv) placing an aluminium foil over charred rice husk, v) pyrolysing the said aluminium added charred rice husk in an inert atmosphere at the temperature range of 1300 to 1800°C for a period of the range of 15 to 30 minutes, vi) burning the pyrolysed product, containing unreacted carbon in oxidizing atmosphere for removal of carbon at a tempertue in the range of 600 to 800°C for a period in the range of 1 to 2 hrs, to obtain the desired product.

Title of Invention

" A PROCESS FOR THE PREPARATION OF ALUMINUM NITRIDE-SILICON CARBIDE REINFORCED CERAMIC FIBER USEFUL FOR MAKING METAL OR CERAMIC MATRIX COMPOSITES."

Abstract

This invention relates to a process for the preparation of Aluminium nitride - Silicon carbide reinforced ceramic fiber useful for metal and ceramic matrix composites which comprises: i) treating the raw rice husk with 3 to 6N HCl for a period of 30 to 90 minutes, filtering and washing with distilled water, adding 5 to 10% NaOH solution filtering and washing with distilled water to obtain cleaned raw rice husk, ii) drying the cleaned raw rice husk at a temperature range of 90 to 110°C for a period in the range of 10 to 14 hours, iii) charring the cleaned, and dried raw rice husk at a temperature in the range of 300 to 700°C, for a period of 1 to 5 hrs., iv) placing an aluminium foil over charred rice husk, v) pyrolysing the said aluminium added charred rice husk in an inert atmosphere at the temperature range of 1300 to 1800°C for a period of the range of 15 to 30 minutes, vi) burning the pyrolysed product, containing unreacted carbon in oxidizing atmosphere for removal of carbon at a tempertue in the range of 600 to 800°C for a period in the range of 1 to 2 hrs, to obtain the desired product.

Full Text	This invention relates to a process for the preparation of Aluminum nitride - Silicon carbide reinforced ceramic fiber useful for making metal or ceramic matrix composites either in situ or otherwise. It is a fact that the second phase, whether in polymer, metal or ceramic matrix, improves substantially the mechanical performance of the composite. It fact, many metal matrix composites, e.g., Al-SiC, Al-Si3N4, Al-Al2O3, etc. are already being commercialized; some small parts of ceramic matrix composite, e.g., Al2O3 B-SiC, SiC-Si3N4, Al2O3-ZrO2, etc. also find applications in high- temperature structural components. The reinforcing materials are basically ceramic particulates, fibers or whiskers. They usually improve the matrix properties either by arresting or branching the micro cracks of the matrix; they also decrease the overall density. In short the advantages of two or multiple phase's materials (composite) are: a) High strength and strength-to-density ratio b) High strength at elevated temperature c) High stiffness-to-density ratio d) Improved fatigue strength e) High toughness (Impact and Thermal) f) Improved creep strength g) Improved stress rupture life h) Improved oxidation and corrosion resistance i) Controlled thermal expansion and thermal conductivity j) Improved hardness and erosion resistance. It is well known that ceramic fibers or whiskers are better reinforcing materials than particulates. Therefore, if a reinforcing ceramic fiber itself (ofthe order of sub micron level diameter) is being reinforced by a second phase material, it would be an ideal reinforcing material. So far, only two of this type of reinforced or dual phase fiber have been developed; those are SiC-Si02-C fiber reference may be made to Am. Ceramic Bulletin, 66(2), 304-308 (1987> and Al2O3-B-SiC fiber refer Ind, Patent No. 486/DEL/88. SiC-SiO2-C fiber is commercially available having the composition of 59% Si, 31* C and 10% oxygen ([equivalent to 72% SiC, 19% Si02 and 9% C). In some respects SiC-SiQ2-C fiber is better than single phase SiC fibers, but it can not be an ideal one since silicon oxycarbide or free carbon are not good ceramics for improving mechanical properties of the matrix in the case of SiC. Again presence of free carbon restricts its use in reactive metals such as aluminum or in oxidizing atmosphere. In an another type of known reinforcing fiber having two distinct phases, i.e., coated fiber, e.g. Mo and W-oxicarbide reference may be made to J. Mater. Sci. , 26(8), 2107-2110 (1992). Ni or Cu coated SiC or SiC coated C, W-filament or Ni, TiN is covered by U.S. Patent 5,141,613, 25 August 1992. Ni/Cu coating on SiC fiber developed to improve the wetability or better bonding of SiC in metal matrices. Some times it is difficult to draw continuous SiC fiber, then C or W filaments are used as a precursor for continuous SiC fiber production. But the coated fiber can not be in true sense a composite fiber. In a yet another known type, in a-A1203-B-SiC fiber either A1203 or sic is reinforcing the other phase. Both A1203 and SiC are good ceramic materials. Similarly AIN-SiC fiber would be a better reinforcing material than only AIN or SiC fiber. So far no such AIN-SiC fiber have been reported anywhere. The thermal conductivity of AIN Is such higher than that of A1203 and it is comparable to SiC. Hence at high temperature or in thermal cyclic System SiC and A1N will be a better combination. The main object of the present invention is to provide a process for the preparation of Aluminum nitride - silicon carbide reinforced ceramic fiber useful for making metal and ceramic matrix composites. Another object of the present invention is to produce directly in situ reinforced ceramic fibers consisting of A1N and SiC. Yet another object of the present invention to utilize rice husk a waste material in production of reinforcing ceramic fibers. In the process of present invention both amorphous silica and carbon is obtained from rice husk. In general, after charring in the temperature range of 300°C to 600°C, rice husk contains approximately 40% silica and the rest carbon. These silica and carbon react together at elevated temperature to form B-SiC. A1N forms from elemental aluminum and nitrogen gas. Formation of AIN from Al and nitrogen gas starts approximately from 700°C, but below 1100°C the reaction is very sluggish. Again SiC starts forming at about 1400°C. Therefore, formation of both AIN and SiC takes place more or less in the same range of temperature; that is if all the raw materials, Al, SiO2, C and nitrogen are kept in the range of 1450° to 1700°C both AIN and SiC form simultaneously. The present invention makes use of aluminum foils of different thickness and the reaction temperature and atmosphere so maintained the both B-SiC and AIN form simultaneously. Accordingly, the present invention provides, a process for the preparation of Aluminum nitride - Silicon carbide reinforced ceramic fiber useful for metal and ceramic matrix composites, which comprises: i) treating the raw rice husk with 3 to 6N HC1 for a period of 30 to 90 minutes, filtering and washing with distilled water, adding 5 to 10% NaOH solution filtering and washing with distilled water to obtain cleaned raw rice husk, ii) drying the cleaned raw rice husk at a temperature range of 90 to 110° C for a period in the range of 10 to 14 hours, iii) charring the cleaned and dried raw rice husk at a temperature in the range of 300 to 700°C, for a period of 1 to 5 hrs., iv) placing an aluminium foil over charred rice husk, v) pyrolysing the said aluminium added charred rice husk in an inert atmosphere at the temperature range of 1300 to 1800°C for a period of the range of 15 to 30 minutes, vi) burning the pyrolysed product, containing unreacted carbon in oxidizing atmosphere for removal of carbon at a temperature in the range of 600 to 800°C for a period in the range of 1 to 2 hrs, to obtain the desired product. According to a feature of the invention, cleaning of raw rice husk may be done with water, 3 to 6N HC1 and 2 to 5% NaOH solution, the cleaned raw rice husk may be dried at a temperature the range of 90°C to 110°C, for a period in the range of 10 to 14 hrs. The cleaned and dried raw rice husk charred at a temperature in the range of 300°C to 700°C, for a period in the range of 1 to 5 hrs. Aluminum may be incorporated in the form of foil thickness in the range of 1.5 to 0.017 mm and purity above 99.5.5%, inert atmosphere may be maintained by N2 gas during pyrolysis. By the process of the present invention, pyrolysed product, novel reinforcing ceramic fiber, containing AlN-SiC fibers have 0.5 to 1 um diameter and 20 to lOOum length is produced which m also contain AlN-SiC particulates of size range from 0.2 to 4 um. The following examples are given by way of illustration and should not be construed to limit the scope of the present inven-t ion. EXAMPLE i lOOgm raw rice husk was taken i n a. litre beaker. It was treated with 3N HC1 for 1 hour, filtered and washed thoroughly with distilled water; then 5% NaOH solution was added and kept for 2 hours. Finally the alkali solution was filtered off and washed with distilled water till the residue was alkali free. The cleaned rice husk was dried at 110°C for 6 hours in an oven. The cleaned and dried raw rice husk was then charred at 500°C in nitrogen atmosphere for 2 hours to remove all moisture and volatile organic matters. 50 gm charred rice husk was kept in a. graphite crucible. A 40 x 40 x 1.5 ram 99.99% pur© aluminum foi,l was kept over charred husk. The crucible was covered with a graphite lead and placed in furnace. Pyrolysis was done at 1500° C in N2 atmosphere for a period of 1 hour. After the pyrolysis a brittle white sheet like material was carefully removed from the top of rest of the pyrolysed product. The white material was examined by XRD, SEM and EDX analysis. It has been observed that the face at the contact with husk contained only fiber and other side contained mostly particulates; but in between these two layers a thin layer of metallic aluminum remained unreacted, because two passive layers of AIN-SiC protected- the molten aluminum neither to react with N2 nor to flow down. Both sides have been examined by EDX and XRD analysis separately. The analysis showed the presence of A1N and ß-SiC. Individual fibers are also analyzed by EDX, which revealed that each fiber contains Al and Si. EXAMPLE 2 100 gm raw rice husk was thoroughly cleaned with 3N HCU 3* NaOH solution and water, then dried at 110°C for Ghrs.in an oven. The cleaned and dried husk was heated at 400°C in nitrogen atmosphere to remove moisture and volatile organic matters. 50 gm charred husk was kept in a graphite crucible; over the husk a 40 x 40 x 0.025 mm aluminum foil kept. The crucible was covered and placed in a furnace. Pyrolysis was carried out at 1600°C in N2 atmosphere for a period of 1 hour. After the pyrolysis a white and very brittle sheet was carefully collected from top of the pyrolysed husk. The white material was examined by XRD, SEM and EDX analysis. In this case unreacted metallic aluminum was not observed but only the portion in contact with rice husk had fibrous materials, other portion contained mostly particulates. SEM-EDX as well as XRD analysis reveals that both fibers and particulates contain Al and Si in the form of A1N and P-SiC respectively. EXAMPLE 3 100 gm raw rice husk was thoroughly cleaned with 3N HCl, 3% NaOH solution and water, then dried at 110°C for 6hrs. in an oven. The cleaned and dried husk was heated at 400°C in inert atmosphere to remove moisture and volatile organic matters. 50 gra charred husk was kept in a graphite crucible of inner diameter 75 mm. 4-6 numbers of 10 x 5 x 0.017 mm 99.99* pure aluminum foils were placed over the husk. The graphite crucible was then kept in a furnace. Pyrolysis was carried out at 1650°C in N2 atmosphere for a period of 1 hour and 30 minutes. After the pyrolysis white and very brittle sheets were carefully collected from top of the pyrolysed husk. Both the sides of the white sheets were examined by XRD, SEH and EDX analysis. It has been observed that greater amount of fibers grown both side of the sheets. XRD analysis showed that the materials contained A1N and ß-SiC phases. SEM-EDX analysis reveals that each fiber contains approximately 35-45% Al and 55-65% Si. The diameter of the fibers varies from 0.3 - 1 µm and the length varies from 20 to 100 µm. The main advantages of the present invention are: i) The present invention utilizes rice husk, a waste material and a. low cost material like aluminum; ii) The present invention is a simultaneous formation of AIN ans ß-SiC; iii) The present invention does not need any coating or spinning equipment. A high temperature (1800°C furnace is the main equipment for this purpose; iv) The present invention produces a unique reinforcing material, i.e., AtN-'£-s>iC ilbar. We Claim: 1. A process for the preparation of Aluminium nitride - Silicon carbide reinforced ceramic fiber useful for metal and ceramic matrix composites which comprises: i) treating the raw rice husk with 3 to 6N HC1 for a period of 30 to 90 minutes, filtering and washing with distilled water, adding 5 to 10% NaOH solution filtering and washing with distilled water to obtain cleaned raw rice husk, ii) drying the cleaned raw rice husk at a temperature range of 90 to 110° C for a period in the range of 10 to 14 hours, iii) charring the cleaned and dried raw rice husk at a temperature in the range of 300 to 700°C, for a period of 1 to 5 hrs., iv) placing an aluminium foil over charred rice husk, v) pyrolysing the said aluminium added charred rice husk in an inert atmosphere at the temperature range of 1300 to 1800°C for a period of the range of 15 to 30 minutes, vi) burning the pyrolysed product, containing unreacted carbon in oxidizing atmosphere for removal of carbon at a temperature in the range of 600 to 800°C for a period in the range of 1 to 2 hrs, to obtain the desired product. 2. A process as claimed in claim 1 wherein the aluminum foil used is of thickness in the range of 1.5 to 0.017mm. And purity above 99.5%. 3. A process as claimed in claims 1 and 2 wherein the inert atmosphere is maintained by the use of Nitrogen gas. 4. A process for the preparation of Aluminum nitride - Silicon carbide reinforced ceramic fibers useful for making metal and ceramic matrix composites substantially as herein described withn

Full Text

This invention relates to a process for the preparation of Aluminum nitride - Silicon carbide reinforced ceramic fiber useful for making metal or ceramic matrix composites either in situ or otherwise.
It is a fact that the second phase, whether in polymer, metal or ceramic matrix, improves substantially the mechanical performance of the composite. It fact, many metal matrix composites, e.g., Al-SiC, Al-Si3N4, Al-Al2O3, etc. are already being commercialized; some small parts of ceramic matrix composite, e.g., Al2O3 B-SiC, SiC-Si3N4, Al2O3-ZrO2, etc. also find applications in high- temperature structural components.
The reinforcing materials are basically ceramic particulates, fibers or whiskers. They usually improve the matrix properties either by arresting or branching the micro cracks of the matrix; they also decrease the overall density. In short the advantages of two or multiple phase's materials (composite) are:
a) High strength and strength-to-density ratio
b) High strength at elevated temperature
c) High stiffness-to-density ratio
d) Improved fatigue strength
e) High toughness (Impact and Thermal)
f) Improved creep strength
g) Improved stress rupture life
h) Improved oxidation and corrosion resistance
i) Controlled thermal expansion and thermal conductivity
j) Improved hardness and erosion resistance.
It is well known that ceramic fibers or whiskers are better reinforcing materials than particulates. Therefore, if a reinforcing ceramic fiber itself (ofthe order of sub micron level diameter) is being reinforced by a second phase material, it would be an ideal reinforcing material. So far, only two of this type of reinforced or dual phase fiber have been developed; those are
SiC-Si02-C fiber reference may be made to Am. Ceramic Bulletin, 66(2), 304-308 (1987> and Al2O3-B-SiC fiber refer Ind, Patent No. 486/DEL/88. SiC-SiO2-C fiber is commercially available having the composition of 59% Si, 31* C and 10% oxygen ([equivalent to 72% SiC, 19% Si02 and 9% C). In some respects SiC-SiQ2-C fiber is better than single phase SiC fibers, but it can not be an ideal one since silicon oxycarbide or free carbon are not good ceramics for improving mechanical properties of the matrix in the case of SiC. Again presence of free carbon restricts its use in reactive metals such as aluminum or in oxidizing atmosphere.
In an another type of known reinforcing fiber having two distinct phases, i.e., coated fiber, e.g. Mo and W-oxicarbide reference may be made to J. Mater. Sci. , 26(8), 2107-2110 (1992). Ni or Cu coated SiC or SiC coated C, W-filament or Ni, TiN is covered by U.S. Patent 5,141,613, 25 August 1992. Ni/Cu coating on SiC fiber developed to improve the wetability or better bonding of SiC in metal matrices. Some times it is difficult to draw continuous SiC fiber, then C or W filaments are used as a precursor for continuous SiC fiber production. But the coated fiber can not be in true sense a composite fiber.
In a yet another known type, in a-A1203-B-SiC fiber either A1203 or sic is reinforcing the other phase. Both A1203 and SiC are good ceramic materials. Similarly AIN-SiC fiber would be a better reinforcing material than only AIN or SiC fiber. So far no such AIN-SiC fiber have been reported anywhere. The thermal conductivity of AIN Is such higher than that of A1203 and it is comparable to SiC. Hence at high temperature or in thermal cyclic
System SiC and A1N will be a better combination.
The main object of the present invention is to provide a process for the preparation of Aluminum nitride - silicon carbide reinforced ceramic fiber useful for making metal and ceramic matrix composites.
Another object of the present invention is to produce directly in situ reinforced ceramic fibers consisting of A1N and SiC.
Yet another object of the present invention to utilize rice husk a waste material in production of reinforcing ceramic fibers.
In the process of present invention both amorphous silica and carbon is obtained from rice husk. In general, after charring in the temperature range of 300°C to 600°C, rice husk contains approximately 40% silica and the rest carbon. These silica and carbon react together at elevated temperature to form B-SiC. A1N forms from elemental aluminum and nitrogen gas. Formation of AIN from Al and nitrogen gas starts approximately from 700°C, but below 1100°C the reaction is very sluggish. Again SiC starts forming at about 1400°C. Therefore, formation of both AIN and SiC takes place more or less in the same range of temperature; that is if all the raw materials, Al, SiO2, C and nitrogen are kept in the range of 1450° to 1700°C both AIN and SiC form simultaneously.
The present invention makes use of aluminum foils of different thickness and the reaction temperature and atmosphere so maintained the both B-SiC and AIN form simultaneously.
Accordingly, the present invention provides, a process for the preparation of Aluminum nitride - Silicon carbide reinforced ceramic fiber useful for metal and ceramic matrix composites, which comprises:
i) treating the raw rice husk with 3 to 6N HC1 for a period of 30 to 90 minutes,
filtering and washing with distilled water, adding 5 to 10% NaOH solution filtering and washing with distilled water to obtain cleaned raw rice husk,
ii) drying the cleaned raw rice husk at a temperature range of 90 to 110° C for a period in the range of 10 to 14 hours,
iii) charring the cleaned and dried raw rice husk at a temperature in the range of 300 to 700°C, for a period of 1 to 5 hrs.,
iv) placing an aluminium foil over charred rice husk,
v) pyrolysing the said aluminium added charred rice husk in an inert atmosphere at the temperature range of 1300 to 1800°C for a period of the range of 15 to 30 minutes,
vi) burning the pyrolysed product, containing unreacted carbon in oxidizing atmosphere for removal of carbon at a temperature in the range of 600 to 800°C for a period in the range of 1 to 2 hrs, to obtain the desired product.
According to a feature of the invention, cleaning of raw rice husk may be done with water, 3 to 6N HC1 and 2 to 5% NaOH solution, the cleaned raw rice husk may be dried at a temperature the range of 90°C to 110°C, for a period in the range of 10 to 14 hrs. The cleaned and dried raw rice husk charred at a temperature in the range of 300°C to 700°C, for a period in the range of 1 to 5 hrs. Aluminum may be incorporated in the form of foil thickness in the range of 1.5 to 0.017 mm and purity above 99.5.5%, inert atmosphere may be maintained by N2 gas during pyrolysis.
By the process of the present invention, pyrolysed product, novel reinforcing ceramic fiber, containing AlN-SiC fibers have 0.5 to 1 um diameter and 20 to lOOum length is produced which m also contain AlN-SiC particulates of size range from 0.2 to 4 um.
The following examples are given by way of illustration and should not be construed to limit the scope of the present inven-t ion.
EXAMPLE i
lOOgm raw rice husk was taken i n a. litre beaker. It was treated with 3N HC1 for 1 hour, filtered and washed thoroughly with distilled water; then 5% NaOH solution was added and kept for 2 hours. Finally the alkali solution was filtered off and washed with distilled water till the residue was alkali free. The cleaned rice husk was dried at 110°C for 6 hours in an oven.
The cleaned and dried raw rice husk was then charred at 500°C in nitrogen atmosphere for 2 hours to remove all moisture and volatile organic matters.
50 gm charred rice husk was kept in a. graphite crucible. A 40 x 40 x 1.5 ram 99.99% pur© aluminum foi,l was kept over charred husk. The crucible was covered with a graphite lead and placed in furnace. Pyrolysis was done at 1500° C in N2 atmosphere for a period of 1 hour.
After the pyrolysis a brittle white sheet like material was carefully removed from the top of rest of the pyrolysed product.
The white material was examined by XRD, SEM and EDX analysis. It has been observed that the face at the contact with husk contained only fiber and other side contained mostly particulates; but in between these two layers a thin layer of metallic aluminum remained unreacted, because two passive layers of AIN-SiC protected- the molten aluminum neither to react with N2 nor to flow
down. Both sides have been examined by EDX and XRD analysis separately. The analysis showed the presence of A1N and ß-SiC. Individual fibers are also analyzed by EDX, which revealed that each fiber contains Al and Si.
EXAMPLE 2
100 gm raw rice husk was thoroughly cleaned with 3N HCU 3* NaOH solution and water, then dried at 110°C for Ghrs.in an oven.
The cleaned and dried husk was heated at 400°C in nitrogen atmosphere to remove moisture and volatile organic matters.
50 gm charred husk was kept in a graphite crucible; over the husk a 40 x 40 x 0.025 mm aluminum foil kept. The crucible was covered and placed in a furnace. Pyrolysis was carried out at 1600°C in N2 atmosphere for a period of 1 hour.
After the pyrolysis a white and very brittle sheet was carefully collected from top of the pyrolysed husk.
The white material was examined by XRD, SEM and EDX analysis. In this case unreacted metallic aluminum was not observed but only the portion in contact with rice husk had fibrous materials, other portion contained mostly particulates. SEM-EDX as well as XRD analysis reveals that both fibers and particulates contain Al and Si in the form of A1N and P-SiC respectively.
EXAMPLE 3 100 gm raw rice husk was thoroughly cleaned with 3N HCl, 3% NaOH solution and water, then dried at 110°C for 6hrs. in an oven.
The cleaned and dried husk was heated at 400°C in inert atmosphere to remove moisture and volatile organic matters. 50 gra charred husk was kept in a graphite crucible of inner diameter 75 mm. 4-6 numbers of 10 x 5 x 0.017 mm 99.99* pure aluminum foils were placed over the husk. The graphite crucible was then kept in a furnace. Pyrolysis was carried out at 1650°C in N2 atmosphere for a period of 1 hour and 30 minutes.
After the pyrolysis white and very brittle sheets were carefully collected from top of the pyrolysed husk.
Both the sides of the white sheets were examined by XRD, SEH and EDX analysis. It has been observed that greater amount of fibers grown both side of the sheets. XRD analysis showed that the materials contained A1N and ß-SiC phases. SEM-EDX analysis reveals that each fiber contains approximately 35-45% Al and 55-65% Si. The diameter of the fibers varies from 0.3 - 1 µm and the length varies from 20 to 100 µm.
The main advantages of the present invention are:
i) The present invention utilizes rice husk, a waste
material and a. low cost material like aluminum; ii) The present invention is a simultaneous formation
of AIN ans ß-SiC; iii) The present invention does not need any coating or
spinning equipment. A high temperature (1800°C
furnace is the main equipment for this purpose; iv) The present invention produces a unique reinforcing
material, i.e., AtN-'£-s>iC ilbar.

We Claim:
1. A process for the preparation of Aluminium nitride - Silicon carbide reinforced ceramic fiber useful for metal and ceramic matrix composites which comprises:
i) treating the raw rice husk with 3 to 6N HC1 for a period of 30 to 90
minutes, filtering and washing with distilled water, adding 5 to 10% NaOH solution filtering and washing with distilled water to obtain cleaned raw rice husk,
ii) drying the cleaned raw rice husk at a temperature range of 90 to 110° C for a period in the range of 10 to 14 hours,
iii) charring the cleaned and dried raw rice husk at a temperature in the range of 300 to 700°C, for a period of 1 to 5 hrs.,
iv) placing an aluminium foil over charred rice husk,
v) pyrolysing the said aluminium added charred rice husk in an inert atmosphere at the temperature range of 1300 to 1800°C for a period of the range of 15 to 30 minutes,
vi) burning the pyrolysed product, containing unreacted carbon in oxidizing atmosphere for removal of carbon at a temperature in the range of 600 to 800°C for a period in the range of 1 to 2 hrs, to obtain the desired product.
2. A process as claimed in claim 1 wherein the aluminum foil used is of thickness in the range of 1.5 to 0.017mm. And purity above 99.5%.
3. A process as claimed in claims 1 and 2 wherein the inert atmosphere is maintained by the use of Nitrogen gas.
4. A process for the preparation of Aluminum nitride - Silicon carbide reinforced ceramic
fibers useful for making metal and ceramic matrix composites substantially as herein described withn

Documents:

1533-del-1995-abstract.pdf

1533-del-1995-claims.pdf

1533-del-1995-complete specification (granted).pdf

1533-del-1995-correspondence-others.pdf

1533-del-1995-correspondence-po.pdf

1533-del-1995-description (complete).pdf

1533-del-1995-form-1.pdf

1533-del-1995-form-2.pdf

1533-del-1995-form-4.pdf

1533-del-1995-form-9.pdf

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Patent Number

192384

Indian Patent Application Number

1533/DEL/1995

PG Journal Number

15/2004

Publication Date

10-Apr-2004

Grant Date

08-Feb-2005

Date of Filing

17-Aug-1995

Name of Patentee

COUNCIL OF SCIENTEFIC AND INDUSTRIAL RESEARCH,

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	SWAPAN KUMAR DAS	NATIONAL METAILURGICAL LABORATORY,JAMSHEDPUR,INIDA.
2	SAMAR DAS	NATIONAL METAILURGICAL LABORATORY,JAMSHEDPUR,INIDA.
3	AJOY KUMAR ROY	NATIONAL METAILURGICAL LABORATORY,JAMSHEDPUR,INIDA.

PCT International Classification Number

C04B 35/71

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA