Title of Invention	A PROCESS OF PREPARING MOLYBDENUM DISILICIDE (MOSI2)"
Abstract	The present invention relates to a process of preparing molybdenum disilicide (MoSi2) comprising: taking powder of Mo & Si of high purity preferably 99.99%, preparing pellets from stoichiometric mixture of Mo & Si by using a steel dye and pressure, as herein defined, V - placing the said pellets completely surrounded by microwave absorbing high purity carbon in a silica crucible, heating the said pellets surrounded by the said microwave oven for 5 to 20 minutes and thereafter allowing them to cool to obtain homogenous molybdenum disilicide (MoSi2) with good crystallinity.

Title of Invention

A PROCESS OF PREPARING MOLYBDENUM DISILICIDE (MOSI2)"

Abstract

The present invention relates to a process of preparing molybdenum disilicide (MoSi2) comprising: taking powder of Mo & Si of high purity preferably 99.99%, preparing pellets from stoichiometric mixture of Mo & Si by using a steel dye and pressure, as herein defined, V - placing the said pellets completely surrounded by microwave absorbing high purity carbon in a silica crucible, heating the said pellets surrounded by the said microwave oven for 5 to 20 minutes and thereafter allowing them to cool to obtain homogenous molybdenum disilicide (MoSi2) with good crystallinity.

Full Text	This invention relates to a process of preparing Molybdenum disilicide(MoSi2) using microwaves. BACK GROUND : MoSi2 is a technologically important material. It is used for making heating elements in high temperature furnaces, interconnecting contacts in integrated circuits, as structural material in aircraft engine hot-section components and the like. MoSi2 based materials are also used in high temperature heat exchangers, gas burners, igniters, turbocharger parts and advanced turbinc engine parts and the like. This high temperature engineering material has other important merits such as excellent oxidation resistance, high melting point (2030 C), low density and can be used as a high temperature joining material for sruclural ceramics. MoSi2 is thermodynamically stable with a wide variety of potential ceramic reinforcements available for making composites, including ceramics such as SiC, Si3N4, Zr02, A1203, mullite, YAG, Y203, TiB2 and TiC. MoSi2 can be easily alloyed with other high melting sillicides as another potential avenue to improve its properties. MoSi2 is an abundant, relatively low-cost material which is non-toxic and environmentally benign[l-6]. The conventional methods of preparing this intermetallic compound are tedious and rather involve direct fusion of high purity metallic constituents for several hours in vacuum, arc melting of pure molybdenum and silicon, laser pulse treatment of "(Mo + Si) mixture, argon sputtering of (MoF2 + SiH4) mixture at 12000 C, thermite method of synthesis, rigorous mechanical alloying, plasma heating or self propagating high temperature synthesis [7-10]. It is the object of this invention to develop a Simple and fast process of preparing MoSi2 using microwaves. I' i To achieve the said objective this invention provides a process of preparing molybdenum disilicide (MoSi2) comprising: taking powder of Mo & Si of high purity preferably 99.99%, preparing pellets from stoichiometric mixture of Mo & Si by using a steel dye and pressure, as herein defined, \^ - placing the said pellets completely surrounded by microwave absorbing ^ L high purity carbon in a silica crucible, heating the said pellets surrounded by the said microwave oven for 5 to 20 minutes and thereafter allowing them to cool to obtain homogenous molybdenum disilicide (MoSi2) with good crystallinity. The microwave heating of the pellets is done by a microwave oven preferably operating at 2450 MHz with a tuneable power level of upto 980 W. After heating the said pellets surrounded by high purity carbon by microwaves for about 10 minutes, the said pellets are inverted and 1-1.5 grams of carbon of high purity per pellet is added to avoid the pellets being exposed to atmosphere during the process. The longer lengths of MoSi2 pellets are prepared and high power larger microwave oven is used for microwave heating to bring down the processing time. To form good pellets, preferably EN-24 steel dye and the axial pressure of 5 tonnes for a batch 2-3 grams of MoSi2 are used. This will not require the use of any binder. The invention will now be described with reference to the following example : EXAMPLE : Powders of high purity elemental Mo and Si (99.99%) are used as starting materials. Pellets were made from stochiometric mixtures 33.33 atomic % of Mo and 66.67 atomic % of Si by using EN-24 steel dye and applying axial pressure of 5 tonnes. Pellets were completely surrounded by microwave absorbing high purity carbon in a silica crucible and exposed to microwaves in a microwave oven. After 10 minutes the pellets were inverted and some more carbon say 1.0-1.5 gram of carbon of high purity by per pellet was added to avoid the pellets being exposed to atmosphere during processing. Thereafter the said pcllets were exposed to another 5 minutes to microwaves in a microwave oven. A hard self-sintered pellets were produced by this process. Figure 2 of the accompanying drawings shows the diffrectogram of the initial unrelated mixture and that of the MoSi2. No impurity peaks were seen and the good crystallinity is evident. The exact composition of the product was confirmed by energy dispersive X-ray analysis (EDAX). In Figure 1 of the accompanying drawings microwave oven (1) is shown for heating the mixture of MoSi2 in a silicon crucible (2), Since only the mixture inside the crucible gets heated up by microwave absorption contamination by the crucible (2) materia! is eliminated, Hence the present method is attractive, in terms of its rapidity, energy, and time saving capability. These pellets can be readily .used as heating element and also can be used as sputtering or laser ablation target for thin film preparation. References 1 J.J. Petrovic, MoSi2- Based High Temperature Structural Silicides, MRS Bull. XVIII (1993) 35. 2 A.K. Vasudcvan and J.J. Petrovic, A comparative overview of molybdenum disilicide composites, Mater. Sci. Eng., A155 (1992) 1. (The whole issue is (Icdicateci to high tomperattire structural silicides). ;i J.J. Potrovic and A.K. Vasudcvau, Overview of high temperature structural siUcides, Mater. Res. Soc. Symp. Proc, 322 (1994) 3. 4 J.J. Petrovic, Mechanical behaviour of MoSi2 and its composites, Mater. Sci. Eng., A192/193 (1995) 31. 5 S. Fukada, K. Shioda, H. Onuki and K. Miyazaki, (Hitachi Ltd.,) Jpn. Kokai Tokkyo Koho Japanese patent No. JP 02,119,141 (7th May 1990) ; Also see Kanthal, Swed. Patent lv55, 836, 1953. 6 Tiirc. Thomander, (Bulten Kanthal AB), Ger. Offen 2, 756, 402 (21st June 1979) (German Patent). 7 J.D. Cotton, Y.S. Kim and M.J. Kaufman, Mater. Sci. Eng., A144 (1991) 287. 8 Eiichi. Kanno, (Taiyo Koko K.K.), Japan Kokai 75 57, 100 (19th May 1975) (Japanese Patent). 9 Fujitsu Ltd., Jpn Kokai. Tokkyo Koho Japanese patent No. JP 58 61, 666 (9th October 1981). 10 R.B. Schwartz, S.R. Srinivasan, J.J. Petrovic and C.J. Maggiore, Synthesis of molybclenmn silicide l\y mechanical alloying, Mater. Sci. Eng., A155 (1992) 75. We claim: A process of preparing molybdenum disilicide (MoSi2) comprising: taking powder of Mo & Si of high purity preferably 99.99%, preparing pellets from stoichiometric mixture of Mo & Si by using a steel dye and pressure, as herein defined, placing the said pellets completely surrounded by microwave absorbing high purity carbon in a silica crucible, heating the said pellets surrounded by the said microwave oven for 5 to 20 minutes and thereafter allowing them to cool to obtain homogenous molybdenum disilicide (MoSi2) with good crystallinity. A process of preparing MoSi2 as claimed in claim 1 wherein the microwave heating of the pellets is done by a microwave oven preferably operating at 2450 MHz with a tuneable power level of upto 980 W. A process of preparing MoSi2 as claimed in claim 1 wherein after heating the said pellets surrounded by high purity carbon by microwaves for about 10 minutes, the said pellets are inverted and 1-1.5 grams of carbon of high purity per pellet is added to avoid the pellets being exposed to atmosphere during the process. A process of preparing MoSi2 as claimed in claim 1 wherein the longer lengths of MoSi2 pellets are prepared and high power larger microwave oven is used for microwave heating to bring down the processing time. A process of preparing MoSi2 as claimed in claim 1 wherein preferably EN-24 steel dye and the axial pressure of 5 tonnes for a batch 2-3 grams of MoSi2 to form pellets are used. 6. 'A process of preparing MoSi2 substantially as herein defined with reference to and as illustrated in the accompanying drawings and foregoing example.

Full Text

This invention relates to a process of preparing Molybdenum disilicide(MoSi2) using
microwaves.
BACK GROUND :
MoSi2 is a technologically important material. It is used for making heating elements in high temperature furnaces, interconnecting contacts in integrated circuits, as structural material in aircraft engine hot-section components and the like. MoSi2 based materials are also used in high temperature heat exchangers, gas burners, igniters, turbocharger parts and advanced turbinc engine parts and the like. This high temperature engineering material has other important merits such as excellent oxidation resistance, high melting point (2030 C), low density and can be used as a high temperature joining material for sruclural ceramics. MoSi2 is thermodynamically stable with a wide variety of potential ceramic reinforcements available for making composites, including ceramics such as SiC, Si3N4, Zr02, A1203, mullite, YAG, Y203, TiB2 and TiC. MoSi2 can be easily alloyed with other high melting sillicides as another potential avenue to improve its properties. MoSi2 is an abundant, relatively low-cost material which is non-toxic and environmentally benign[l-6].
The conventional methods of preparing this intermetallic compound are tedious and rather involve direct fusion of high purity metallic constituents for several hours in vacuum, arc melting of pure molybdenum and silicon, laser pulse treatment of "(Mo + Si) mixture, argon sputtering of (MoF2 + SiH4) mixture at 12000 C, thermite method of synthesis, rigorous mechanical alloying, plasma heating or self propagating high temperature synthesis [7-10].
It is the object of this invention to develop a Simple and fast process of preparing MoSi2
using microwaves.

I'
i
To achieve the said objective this invention provides a process of preparing molybdenum disilicide (MoSi2) comprising:
taking powder of Mo & Si of high purity preferably 99.99%,
preparing pellets from stoichiometric mixture of Mo & Si by using a
steel dye and pressure, as herein defined,
\^ - placing the said pellets completely surrounded by microwave absorbing
^ L
high purity carbon in a silica crucible,
heating the said pellets surrounded by the said microwave oven for 5 to 20 minutes and thereafter allowing them to cool to obtain homogenous molybdenum disilicide (MoSi2) with good crystallinity.
The microwave heating of the pellets is done by a microwave oven preferably operating at 2450 MHz with a tuneable power level of upto 980 W.
After heating the said pellets surrounded by high purity carbon by microwaves for about 10 minutes, the said pellets are inverted and 1-1.5 grams of carbon of high
purity per pellet is added to avoid the pellets being exposed to atmosphere during the process.
The longer lengths of MoSi2 pellets are prepared and high power larger microwave oven is used for microwave heating to bring down the processing time.
To form good pellets, preferably EN-24 steel dye and the axial pressure of 5 tonnes for a batch 2-3 grams of MoSi2 are used. This will not require the use of any binder.

The invention will now be described with reference to the following example :
EXAMPLE :
Powders of high purity elemental Mo and Si (99.99%) are used as starting materials. Pellets were made from stochiometric mixtures 33.33 atomic % of Mo and 66.67 atomic % of Si by using EN-24 steel dye and applying axial pressure of 5 tonnes. Pellets were completely surrounded by microwave absorbing high purity carbon in a silica crucible and exposed to microwaves in a microwave oven. After 10 minutes the pellets were inverted and some more carbon say 1.0-1.5 gram of carbon of high purity by per pellet was added to avoid the pellets being exposed to atmosphere during processing. Thereafter the said pcllets were exposed to another 5 minutes to microwaves in a microwave oven. A hard self-sintered pellets were produced by this process. Figure 2 of the accompanying drawings shows the diffrectogram of the initial unrelated mixture and that of the MoSi2. No impurity peaks were seen and the good crystallinity is evident. The exact composition of the product was confirmed by energy dispersive X-ray analysis (EDAX). In Figure 1 of the accompanying drawings microwave oven (1) is shown for heating the mixture of MoSi2 in a silicon crucible (2), Since only the mixture inside the crucible gets heated up by microwave absorption contamination by the crucible (2) materia! is eliminated, Hence the present method is attractive, in terms of its rapidity, energy, and time saving capability. These pellets can be readily .used as heating element and also can be used as sputtering or laser ablation target for thin film preparation.

References
1 J.J. Petrovic, MoSi2- Based High Temperature Structural Silicides, MRS Bull.
XVIII (1993) 35.
2 A.K. Vasudcvan and J.J. Petrovic, A comparative overview of molybdenum
disilicide composites, Mater. Sci. Eng., A155 (1992) 1. (The whole issue is (Icdicateci to high tomperattire structural silicides).
;i J.J. Potrovic and A.K. Vasudcvau, Overview of high temperature structural siUcides, Mater. Res. Soc. Symp. Proc, 322 (1994) 3.
4 J.J. Petrovic, Mechanical behaviour of MoSi2 and its composites, Mater. Sci.
Eng., A192/193 (1995) 31.
5 S. Fukada, K. Shioda, H. Onuki and K. Miyazaki, (Hitachi Ltd.,) Jpn. Kokai
Tokkyo Koho Japanese patent No. JP 02,119,141 (7th May 1990) ; Also see Kanthal, Swed. Patent lv55, 836, 1953.
6 Tiirc. Thomander, (Bulten Kanthal AB), Ger. Offen 2, 756, 402 (21st June
1979) (German Patent).
7 J.D. Cotton, Y.S. Kim and M.J. Kaufman, Mater. Sci. Eng., A144 (1991) 287.
8 Eiichi. Kanno, (Taiyo Koko K.K.), Japan Kokai 75 57, 100 (19th May 1975)
(Japanese Patent).
9 Fujitsu Ltd., Jpn Kokai. Tokkyo Koho Japanese patent No. JP 58 61, 666
(9th October 1981).
10 R.B. Schwartz, S.R. Srinivasan, J.J. Petrovic and C.J. Maggiore, Synthesis of
molybclenmn silicide l\y mechanical alloying, Mater. Sci. Eng., A155 (1992)
75.

We claim:
A process of preparing molybdenum disilicide (MoSi2) comprising: taking powder of Mo & Si of high purity preferably 99.99%, preparing pellets from stoichiometric mixture of Mo & Si by using a steel dye and pressure, as herein defined,
placing the said pellets completely surrounded by microwave absorbing high purity carbon in a silica crucible,
heating the said pellets surrounded by the said microwave oven for 5 to 20 minutes and thereafter allowing them to cool to obtain homogenous molybdenum disilicide (MoSi2) with good crystallinity.
A process of preparing MoSi2 as claimed in claim 1 wherein the microwave heating of the pellets is done by a microwave oven preferably operating at 2450 MHz with a tuneable power level of upto 980 W.
A process of preparing MoSi2 as claimed in claim 1 wherein after heating the said pellets surrounded by high purity carbon by microwaves for about 10 minutes, the said pellets are inverted and 1-1.5 grams of carbon of high purity per pellet is added to avoid the pellets being exposed to atmosphere during the process.
A process of preparing MoSi2 as claimed in claim 1 wherein the longer lengths of MoSi2 pellets are prepared and high power larger microwave oven is used for microwave heating to bring down the processing time.
A process of preparing MoSi2 as claimed in claim 1 wherein preferably EN-24 steel dye and the axial pressure of 5 tonnes for a batch 2-3 grams of MoSi2 to form pellets are used.

6. 'A process of preparing MoSi2 substantially as herein defined with reference to and as illustrated in the accompanying drawings and foregoing example.

Documents:

788-mas-95 abstract.pdf

788-mas-95 assignment.pdf

788-mas-95 claims.pdf

788-mas-95 correspondence-others.pdf

788-mas-95 correspondence-po.pdf

788-mas-95 drawings.pdf

788-mas-95 dscription(complete).pdf

788-mas-95 form-1.pdf

788-mas-95 form-3.pdf

788-mas-95 others.pdf

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Patent Number

192910

Indian Patent Application Number

788/MAS/1995

PG Journal Number

20/2006

Publication Date

19-May-2006

Grant Date

25-Jan-2006

Date of Filing

27-Jun-1995

Name of Patentee

INDIAN INSTITUTE OF SCIENCE

Applicant Address

BANGALORE-560 012

Inventors:

#	Inventor's Name	Inventor's Address
1	PROF. KALYA JAGANNATHA RAO	INDIAN INSTITUTE OF SCIENCE DEPORTMENT OF SOLID STATE AND STRUCTURAL CHERISTRY UNIT BANGALORE-560012
2	BALASUBRAMANIAM VAIDAYANATHAN	INDIAN INSTITUTE OF SCIENCE DEPORTMENT OF SOLID STATE AND STRUCTURAL CHERISTRY UNIT BANGALORE-560012

PCT International Classification Number

C01G39/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA