| 摘要 |
A polymeric processing aid is disclosed for compaction of ceramic or ceramic-forming powders at ambient temperalures and at pressures in excess of 15,000 psi and at impact rates of 12-44 strokes/minute without altering the chemical/physical properties of the resulting ceramic. The processing aid comprises a polymerized acrylate or mixed acrylate/methacrylate monomer which has been polymerized; the polymer is selected to have a Tg of at least 50 DEG C below room temperature, a molar cohesive energy of 7000-20,000 cal/mole. a number average molecular weight of 4000-20,000, a surface tension less than 35 dyne/cm, and a viscous liquid physical form at room temperature. A method of using much processing aid is also disclosed. The method comprises mixing silicon powder with oxygen-carrying agents (Y203, A1203Si02) in the amount of 4-19% by weight of the mixture along with 2-3.5% by weight of the processing aid. The mixture is subjected to high speed cold-compaction at pressures in excess of 15,000 psi with an impact rate of 12-44 strokes/minute. The compacted and ejected cold-pressed body is heat treated to form a dense Si3N4 object. |
