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Reaction-sintered silicon carbide, silicon carbide nozzles, radiation tubes, burners, heat-exchange tubes, silicon carbide furnace tubes, burners, silicon carbide plates
Let’s talk about the reaction-sintered silicon carbide processing technology.
Release time:
2022-10-19
Reaction-sintered silicon carbide Porcelain boasts excellent properties such as high resistance to ambient temperature, resistance to thermal oxidation, good wear resistance, superior thermal stability, a low coefficient of linear thermal expansion, high thermal conductivity, high hardness, resistance to thermal shock, and fire resistance. It is widely used in fields including vehicles, mechanical automation, environmental protection, aerospace engineering, information electronics, and power energy, making it an indispensable, cost-effective structural ceramic for numerous industrial sectors.
Pressureless sintering is regarded as a promising method for the production of SiC ceramics. Depending on the specific continuous casting equipment used, pressureless sintering can be categorized into solid-phase sintering and high-efficiency liquid-phase sintering. By adding appropriate amounts of B and C (with an oxygen content below 2%) to ultrafine beta-SiC powder, S. Proehazka achieved sintered SiC compacts with a relative density exceeding 98% at temperatures below 2020°C. When using Al2O3 and Y2O3 as additives and sintering 0.5-micron SiC particles (whose surface contains a small amount of SiO2) at temperatures ranging from 1850°C to 1950°C, the resulting SiC ceramics exhibited a density exceeding 95% of the theoretical density, with fine grain sizes averaging 1.5 μm.
Reaction-sintered silicon carbide refers to the process in which porous green bodies undergo reactions with a liquid phase or a highly efficient liquid phase, thereby improving the quality of the green bodies, reducing porosity, and achieving the final product with specified strength and dimensional accuracy. A mixture of Pu-SiC powder and high-purity graphite, blended according to a certain ratio, is heated to around 1650°C to form a green body. During this process, liquid-phase Si infiltrates or permeates into the ceramic matrix, reacting with silicon carbide to form Pu-SiC and also bonding with pre-existing Pu-SiC particles. Once Si has fully infiltrated, a densely packed reaction-sintered body with no shrinkage in dimensions can be obtained. Compared with other sintering methods, reaction sintering exhibits relatively small dimensional changes during densification, enabling the production of dimensionally accurate parts. However, since a large amount of SiC remains in the sintered body, the high-temperature performance of reaction-sintered SiC ceramics tends to be inferior. Sintered SiC ceramics produced by pressureless sintering, hot isostatic pressing, and reaction sintering each exhibit distinct characteristics.
Reaction-sintered silicon carbide Manufacturing processes: For example, in terms of relative density and flexural strength, SiC ceramics produced via hot-press sintering and hot isostatic pressing generally exhibit higher performance compared to those obtained through reaction-sintered SiC. Meanwhile, the physical properties of SiC ceramics can vary depending on the type of sintering modifier used. Uniaxial pressure sintering, hot-press sintering, and reaction-sintered SiC ceramics all demonstrate good resistance to alkalis and acids; however, reaction-sintered SiC ceramics tend to have weaker resistance to highly corrosive acids such as hydrofluoric acid (HF). At ambient temperatures below 900°C, the flexural strength of most SiC ceramics is significantly higher than that of ceramics sintered at higher temperatures. Notably, the flexural strength of reaction-sintered SiC ceramics drops sharply when the temperature exceeds 1400°C. This phenomenon is attributed to a sudden decrease in flexural strength caused by the formation of a certain amount of glassy Si phase within the sintered body above a specific temperature. For SiC ceramics sintered without pressure or via hot isostatic pressing, their high-temperature performance is primarily influenced by the type of additive used.
I won’t go into further details—let’s meet again next time.
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