الفهرس | Only 14 pages are availabe for public view |
Abstract Different types of silicon carbide powders, with a few amount of boron and carbon as sintering additives have been investigated. The powder blends were wet mixed with ethanol and ceramic balls in polyethylene, and glass bottles by a rotational mixer for 24 hours. All powders were dried in a furnace at temperatures 80-120 QC and screened through a 60 mesh sieve. Flat pellets were uniaxially pressed in a stainless steel die at pressures 120-190 MPa. Other specimens are cold isostatically pressed under 350 MPa into cylindrical shape with specific dimensions for investigating some mechanical, thermal, and electrical properties. Some specimens are pressureless sintered using 1800-2200 QC, and 10-120 minutes as a holding time in argon atmosphere. Other specimens were sintered using hot isostatic pressure (HIPing) with 1800 QC and 300 MPa argon pressure. Also the specimens are infiltrated with molten silicon under vacuum and 1450 QC for 150-180 minutes. The relationship hetween sintering temperatures and some physical parameters such as; mass losses, relative densities, fracture toughness, and microhardness of different SiC types at different sintering temperatures were investigated. The surface of specimens were polished and chemically etched before the microstructure investigations. Microstructure, x-ray diffractions, thermogravimeteric analysis, and chemical analysis were done for the different types of silicon carbide. A large numbers of the different specimens with different compositions were tested 10 the electron beam facility JUDITH with different pulse durations, and energy densities among 1.15 to 11.3 MJ/m2. The specimens after the testing. |