Dense sintered silicon carbide

Properties of Dense Silicon Carbide. Properties of the SiC stmctural ceramics are shown in Table 1. These properties are for representative materials. Variations can exist within a given form depending on the manufacturer. Figure 2 shows the flexure strength of the SiC as a function of temperature. Sintered or sinter/HIP SiC is the preferred material for appHcations at temperatures over 1400°C and the Hquid-phase densified materials show best performance at low temperatures. The reaction-bonded form is utilized primarily for its ease of manufacture and not for superior mechanical properties. 

Silicon carbide, hot pressed Alumina, dense sintered Boron nitride, hot pressed Silicon nitride, hot pressed Boron carbide, hot pressed... 

Only highly dense ceramics with high thermal shock resistance can be utilized for such strongly mechanically and thermally stressed components. These demands are met by hot-pressed silicon carbide produced at pressures of 350 bar and sintering temperatures of 1900 to 2000°C. The necessary, but very expensive, mechanical finishing is disadvantageous for industrial manufacture of hot-pressed silicon carbide. 

Dense SiC platelet reinforced silicon carbide composites were recently fabricated [52]. The highest sintered densities of 97-98% TD were achieved with 20% platelet contents using hot molding as the thermoplastic forming technique [53]. 

This opened up an inexpensive method of producing dense and complex parts consisting of pure silicon carbide (SSiC). The powders (see Fig. 8) can be molded into a green body by any of the methods used in ceramic molding [93,94], depending on the shape required and the number of pieces involved (see Table 5). Sintering is... 

As with silicon nitride, solid forms of silicon carbide are made by one of three processes sintered, hot-pressed, or reaction-sintered. Sintering requires use of an additive such as alumina, carbon, or boron to promote liquid-phase sintering. Hot pressing is done at 2000°C and results in a very hard, dense material. Reaction sintering occurs when a mixture of SiC powder and carbon is heated in contact with molten silicon. The reaction results in a nearly complete conversion to SiC, although according to Schwartz, most materials made by this process contain an excess of carhon or silicon. ... 

Sintering involving a chemical reaction is typical for the manufacture of some carbides and nitrides. For example, dense SiC is obtained by firing carbon compacts in silicon vapours. A similar example is provided by the manufacture of densified Si3N4 w here the nitride is formed in the powdered metal compact by reaction with gaseous nitrogen the product fills up the pores and thus gives low porosity. 

---