Densification of nano-size powders. 1994 report
- National Inst. of Standards and Technology, Gaithersburg, MD (United States)
- Air Force Office of Scientific Research, Washington, DC (United States)
- Rutgers Univ., Piscataway, NJ (United States)
Green compacts from a nano-size silicon nitride powder were fabricated having density up to 67% of theoretical at 2.8 GPa pressure using liquid nitrogen and pentane as compaction lubricant media. Pressureless sintering of these transparent samples did not promote further densification beyond that obtained for the green state. To further increase the density of these samples, a hot-pressing device was designed. In a series of experiments, hot-pressing of these samples at.0.5 to 1.0 GPa and 800 C, followed by pressureless sintering at 1400 C was studied. The resulting silicon nitride ceramic had a Vickers hardness of 9.0 GPa while transparency under visible light was maintained. Without the use of hot pressing, the hardness obtained was 5.8 GPa. In addition, the effect of compaction pressure on densification was studied for nano-size Al{sub 2}O{sub 3} to further understand factors contributing to achieving high green densities. The dense Al{sub 2}O{sub 3} green samples were pressureless sintered to near full density at temperatures several hundred degrees lower than those needed for sintering low density green material.
- Research Organization:
- National Inst. of Standards and Technology, Gaithersburg, MD (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AI05-92OR22041
- OSTI ID:
- 10159459
- Report Number(s):
- DOE/OR/22041--2; ON: DE94013486; BR: 820201000
- Country of Publication:
- United States
- Language:
- English
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