Recrystallized Silicon Carbide (RXSIC, ReSIC, RSIC, R-SIC). The starting raw material is silicon carbide. No densification aids are used. The green compacts are heated to over 2200ºC for final consolidation. The resulting material has about 25% porosity, which limits its mechanical properties; however, the material can be very pure. The process is very economical.
Reaction Bonded Silicon Carbide (RBSIC). The starting raw materials are silicon carbide plus carbon. The green component is then infiltrated with molten silicon above 1450ºC with the reaction: SiC + C + Si -> SiC. The microstructure generally has some amount of excess silicon, which limits its high-temperature properties and corrosion resistance. Little dimensional change occurs during the process; however, a layer of silicon is often present on the surface of the final part. ZPC RBSiC are adopted the advanced technology, producing the wear resistance lining, plates, tiles, cyclone lining, blocks, irregular parts, and wear & corrosion resistance FGD nozzles, heat exchanger, pipes, tubes, and so on.
Nitride Bonded Silicon Carbide (NBSIC, NSIC). The starting raw materials are silicon carbide plus silicon powder. The green compact is fired in a nitrogen atmosphere where the reaction SiC + 3Si + 2N2 -> SiC + Si3N4 occurs. The final material exhibits little dimensional change during processing. The material exhibits some level of porosity (typically about 20%).
Direct Sintered Silicon Carbide (SSIC). Silicon carbide is the starting raw material. Densification aids are boron plus carbon, and densification occurs by a solid-state reaction process above 2200ºC. Its hightemperature properties and corrosion resistance are superior because of the lack of a glassy second phase at the grain boundaries.
Liquid Phase Sintered Silicon Carbide (LSSIC). Silicon carbide is the starting raw material. Densification aids are yttrium oxide plus aluminum oxide. Densification occurs above 2100ºC by a liquid-phase reaction and results in a glassy second phase. The mechanical properties are generally superior to SSIC, but the high-temperature properties and the corrosion resistance are not as good.
Hot Pressed Silicon Carbide (HPSIC). Silicon carbide powder is used as the starting raw material. Densification aids are generally boron plus carbon or yttrium oxide plus aluminum oxide. Densification occurs by a simultaneous application of mechanical pressure and temperature inside a graphite die cavity. The shapes are simple plates. Low amounts of sintering aids can be used. Mechanical properties of hot pressed materials are used as the baseline against which other processes are compared. Electrical properties can be altered by changes in the densification aids.
CVD Silicon Carbide (CVDSIC). This material is formed by a chemical vapor deposition (CVD) process involving the reaction: CH3SiCl3 -> SiC + 3HCl. The reaction is carried out under a H2 atmosphere with the SiC being deposited onto a graphite substrate. The process results in a very high-purity material; however, only simple plates can be made. The process is very expensive because of the slow reaction times.
Chemical Vapor Composite Silicon Carbide (CVCSiC). This process starts with a proprietary graphite precursor that is machined into near-net shapes in the graphite state. The conversion process subjects the graphite part to an in situ vapor solid-state reaction to produce a polycrystalline, stoichiometrically correct SiC. This tightly controlled process allows complicated designs to be produced in a completely converted SiC part that has tight tolerance features and high purity. The conversion process shortens the normal production time and reduces costs over other methods.* Source (except where noted): Ceradyne Inc., Costa Mesa, Calif.
Post time: Jun-16-2018