Cryogenic compaction of nanosize silicon nitride powders
- National Institute of Standards and Technology, Gaithersburg, MD (United States)
- Air Force Office of Scientific Research, Washington, DC (United States)
- Rutgers Univ., Newark, NJ (United States)
This paper describes a highly-specialized system for studies of time-dependent compaction of nanosize silicon nitride powders under a variety of atmospheres and at temperatures ranging from 77 to 1,000 K. The system incorporates a screw-driven press (10 ton capacity) with a piston-cylinder type die and can produce cylindrical powder compacts, 3 mm in diameter and approximately 1 mm in thickness, using pressures measurements of the sample volume, and, after appropriate calibration, can determine the rate and degree of densification of the compacting powder as pressure is applied. Frictional forces between the piston and the die are measured during the compaction process. For calibration of the system, powders with known volume-change accompanied by phase transition under pressure were studied, and good agreement with published results was demonstrated. Several Si{sub 3}N{sub 4} samples have been compacted and sintered at 1,300 to 1,600{degrees}C. A maximum random packing density of 64% has been obtained using liquid nitrogen as a lubricant medium at pressures lower than 2.5 GPa. Both green samples and samples sintered at temperatures to 1,500{degrees}C exhibited visual transparency under visible light.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- OSTI ID:
- 140118
- Report Number(s):
- ORNL/FMP--93/1; CONF-9305135--; ON: DE94001091
- Country of Publication:
- United States
- Language:
- English
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