Development and Applications of Silicon Carbide Ceramics

　　The industrial method for producing silicon carbide involves mixing quartz, carbon (coke), wood chips, and common salt, then heating the mixture in an electric furnace to a temperature between 2,200 and 2,500°C. What distinguishes silicon carbide ceramics from many other ceramics is that, at room temperature, silicon carbide is both electrically conductive and highly resistant to high temperatures, making it an excellent heating element. Electric heating rods made from silicon carbide are called silicon-carbide rods; in air, they can withstand temperatures as high as 1,450°C. High-quality silicon-carbide rods produced by the recrystallization method can even endure temperatures up to 1,600°C—far exceeding the maximum operating temperatures of metallic heating elements (with the exception of precious metals such as platinum and rhodium). This exceptional resistance stems from the fact that, at high temperatures in air, silicon carbide oxidizes to form a dense layer of silicon dioxide, which effectively isolates the material from further oxidation. As a result, the underlying silicon carbide is significantly slowed down in its oxidation process, enabling it to maintain its performance under extreme heat conditions. Using hot-pressing techniques, it’s possible to produce silicon-carbide ceramics with densities approaching their theoretical maximum. Even at high temperatures around 1,400°C, the flexural strength of these highly dense ceramics can still reach 500–600 MPa, whereas the strength of most other ceramic materials drops dramatically once the temperature exceeds 1,200°C. Thus, silicon carbide stands out as the material with the highest strength in high-temperature, air-exposed environments.

　　To improve the efficiency of high-temperature gas turbine engines, it is essential to raise the operating temperature. The key to solving this challenge lies in identifying structural materials that can withstand high temperatures—particularly the blade materials used inside the engine. Silicon carbide ceramics possess sufficient strength at high temperatures and exhibit excellent oxidation resistance and thermal shock resistance. These outstanding properties make them exceptionally well-suited for use as high-temperature structural materials. As for materials used in high-temperature gas turbine blades operating at 1200–1400°C, many scientists consider silicon carbide ceramics and silicon nitride ceramics to be the most promising candidates. Fountyl Fangtai New Materials produces high-end porous ceramic suction cups.

　　Silicon carbide ceramics have thermal conductivity second only to beryllium oxide ceramics. Leveraging this property, silicon carbide ceramics can serve as an excellent material for heat exchangers. In solar power generation systems, heat exchangers that concentrate sunlight for heating operate at temperatures as high as 1,000 to 1,100°C. Given their high thermal conductivity, silicon carbide ceramics are particularly well-suited for use in such heat exchangers. According to experimental results, silicon carbide ceramic heat exchangers exhibit excellent operational performance. Moreover, in nuclear reactors, silicon carbide ceramics can be used as cladding materials for nuclear fuel; they can also serve as nozzles for rocket exhaust pipes and as bulletproof equipment for aircraft pilots.

　　Moreover, to enhance the cutting performance of cutting tools, tool materials have undergone two major developmental stages since the 20th century: first, high-speed steel, and then cemented carbide. Currently, we are entering a phase of rapid development for ceramic cutting tools. Thanks to their exceptional resistance to high temperatures and excellent wear resistance, new-generation ceramics first attracted attention from the high-speed cutting-tool industry in the early 20th century. Ceramic cutting tools boast high hardness and outstanding wear resistance, making them an ideal material for manufacturing cutting tools. At present, the primary materials used for producing ceramic cutting tools include alumina, alumina-titanium carbide, alumina-titanium nitride-titanium carbide-tungsten carbide, alumina-tungsten carbide-chromium, boron nitride, and silicon nitride. Tools made from these materials can operate without coolant and offer advantages over cemented carbides, such as higher cutting speeds and longer tool life. Today, countries in Europe and the United States have widely adopted ceramic materials for drills, taps, and hobbing tools. In the former Soviet Union, more than 7,000 varieties of alloy cutting tools were developed, with surface ceramic coatings applied via spraying techniques to significantly improve the working speed and service life of turning tools.

　　In addition to being used as cutting tools, ceramics—thanks to their wear-resistant and corrosion-resistant properties—can also serve as wear-resistant components in a wide variety of mechanical applications. For instance, special ceramics have been successfully employed to manufacture wear- and corrosion-resistant parts or sealing rings for agricultural water pumps, mortar pumps, chemical pumps handling corrosive liquids, and dust-laden fans, all achieving excellent practical results. Moreover, high-purity alumina (corundum) can be used to produce wire-drawing dies for metals; particularly in hot-drawing processes at elevated temperatures, the superior performance of ceramics becomes even more evident. Other examples include grinding cylinders and grinding balls made from industrial ceramics, sandblasting nozzles for removing rust from metal surfaces, and spray nozzles for applying pesticides. In short, wherever wear resistance and corrosion resistance are required, special ceramics can almost always be found.