Silicon Carbide (SiC), a man-made strong covalent compound material, was first discovered in 1891 by E.G. Acheson during his experiments with electro-fused diamonds. Since then, SiC has gained prominence due to its exceptional properties, including high-temperature strength, superior thermal conductivity, high wear resistance, and excellent corrosion resistance. These attributes make SiC indispensable in industries such as aerospace, automotive, machinery, electronics, and chemicals. As a leading material in foreign trade, SiC is primarily produced using the Acheson method, with global annual production exceeding one million tons. In China, regions like Qinghai, Gansu, Ningxia, and Inner Mongolia benefit from abundant hydroelectric resources and quality raw materials, hosting numerous SiC manufacturers. China produces about 380,000 tons annually, accounting for 40% of the world's output, positioning it as a major exporter and innovator in SiC micro powder, whiskers, and composite materials.
Over the past century, the Acheson method remains the cornerstone of SiC industrial production, utilizing an intermittent process. Modern advancements include larger furnace sizes, with lengths extending up to 25 meters and capacities reaching thousands of tons per batch. Power inputs have also increased, ranging from 3,000 to 7,000 kW, with some facilities in China, like the Northern Silicon Carbide Company in Ningxia, operating ultra-large furnaces up to 12,000 kW. The shift from alternating current to direct current has enhanced grid stability and operational ease. Structural improvements focus on end walls, side walls, and waste material utilization, leading to longer furnace lifespans and easier loading/unloading. However, challenges persist, such as thermal overload on electrodes and uneven core surfaces, which can cause frequent eruptions and damage to furnace components. Most manufacturers prefer fixed-style furnaces with or without bottom exhausts, despite the advantages of mobile alternatives.
Despite its efficiency, the Acheson method is energy-intensive and contributes to environmental pollution through emissions like CO2, SO2, and SiC dust. Developed countries in Europe and the US have reduced domestic production, opting to import from nations like China, Brazil, and Venezuela, where over 65% of global primary SiC is produced. Traditional furnaces struggle with issues such as raw material odors, sulfur compounds, and uncollected gases. Innovations by Germany's ESK Company in the 1970s addressed these by designing outdoor furnaces without end or side walls, using linear or U-shaped electrodes and sealed covers to capture gases for energy recovery. This approach reduces pollution by 20% and allows the use of high-sulfur raw materials, improving cost-effectiveness. While the method offers cheap raw materials and easy industrialization, it produces SiC powder with moderate quality, including surface areas of 1-15 m²/g and impurities that require post-processing like acid washing.
Acheson-method SiC finds extensive use as an abrasive, refractory material, structural ceramic, and steel deoxidizer. In abrasives, it excels in cutting and grinding applications for glass, ceramics, stone, cast iron, non-ferrous metals, hard alloys, titanium alloys, and high-speed steel tools. Refractory SiC materials are vital in steel production for lining ladles, troughs, blast furnace bottoms, and heating furnace rails. In non-ferrous metal smelting, it's used for distillation equipment, electrolytic cell walls, pipes, and crucibles. The chemical and ceramic industries employ SiC in desulfurization furnaces, oil-gas generators, kiln shelves, and flame barriers. High-purity SiC (over 90%) suits medium-high temperature furnace components, while lower-grade versions (above 83%) line iron channels and ladles.
As a deoxidizer in steelmaking, SiC offers benefits like fine particle size, rapid reaction, short deoxidation time, energy savings, high production rates, effective desulfurization, and low costs. Internationally adopted in the 1980s, China began using it in 1985, and it's now widespread, with annual demand exceeding millions of tons given steel production over 100 million tons. SiC also serves as a sealing ring alternative to alumina or graphite, with annual usage in Europe, the US, and Japan reaching millions of units and growing. These applications underscore SiC's role in enhancing industrial efficiency and durability, making it a key export from China.
β-SiC micro powder production has advanced since the late 1980s through methods like sol-gel, polymer pyrolysis, and various vapor-phase techniques. Vapor-phase and polymer thermal decomposition methods produce high-yield amorphous SiC powder at 600-1,800°C, with surface areas up to 25 m²/g and impurities below 60 ppm. This powder pressure-sinters to high densities, ideal for high-temperature structural ceramics used in gas turbine rotors, nozzles, burners, heat exchangers, engine cylinders, pistons, nuclear reactor components, and radar antenna covers for rockets. Ceramic gas turbines achieve 20% higher efficiency than conventional ones. Germany's ESK Company tested SiC turbocharger rotors in gasoline engines, reaching 96,000 rpm and 1,030°C exhaust temperatures over 1,000 km, showing excellent performance. In diesel engines, SiC is used for valve lifters, turbo rotors, and swirl chambers, with market projections indicating dominance in automotive ceramics by 2000-2010, valued at over $36 billion.
Chemical Vapor Deposition (CVD) SiC materials boast near-theoretical density and ultra-high purity (99.999%), delivering outstanding physical and chemical properties. Applications include diffusion barriers in atomic energy and molds for thermal optical lenses. Recent innovations involve depositing SiC on carbon or tungsten fibers to create fibers up to 120 μm in diameter. Companies like Morton International have mass-produced large CVD-SiC sheets, 1,500 mm wide and 25 mm thick, with thermal conductivity of 250 W/m·K, flexural strength of 466 MPa, and surfaces polished to sub-nanometer optical precision. Emerging uses encompass high-temperature laser optics, seals, wear components, computer storage substrates, and electronic encapsulation, highlighting CVD-SiC's versatility in advanced technologies.
SiC whiskers are cubic SiC crystals with extreme anisotropy, featuring aspect ratios over 10, diameters from sub-microns to a few microns, and lengths up to hundreds of microns or even 100 mm via specialized processes. Research began in the 1960s, with companies like Carborundum and ESK developing semi-commercial methods. Growth mechanisms include vapor-solid (VS) and vapor-liquid-solid (VLS) reactions, producing whiskers with tensile strengths up to 16 GPa and elastic moduli of 580 GPa. VLS whiskers, grown with catalysts like iron or cobalt, reach diameters of 3-5 μm and exceptional lengths, making them ideal reinforcements in composites for enhanced mechanical performance.
SiC platelets, valued for their mechanical properties and cost-effectiveness, serve as reinforcements in composites. Naturally formed in Acheson furnaces, they are refined for industrial use through processes adding boron or aluminum promoters at high temperatures, yielding platelets of 10-100 μm. These can be mixed with β-SiC powder and processed at 1,900-2,100°C in inert atmospheres to produce over 90% α-SiC platelets. With properties like high strength and thermal stability, as detailed in industry tables, SiC platelets significantly improve the toughness of metal and ceramic matrix composites.
Continuous SiC fibers are widely adopted as reinforcements in metal and ceramic matrix composites, with commercial products like Nicalon and Tyranno. Advances by companies such as Carborundum and Dow Corning have enabled large-scale production. New fibers, like Bayer's Si-B-C-N, maintain amorphous structures up to 1,800°C with tensile strengths over 3 GPa. Standard sintering at 2,130°C in argon produces α-SiC fibers from sub-2 μm powders, offering diameters around 20 μm and superior mechanical parameters, enhancing applications in high-performance composites.
SiC's electrical properties, including a wide bandgap (3.26 eV for 4H-SiC), high breakdown field, thermal conductivity (490 W/m·K), and electron drift velocity, make it ideal for high-temperature, high-frequency, high-radiation, and high-power devices like UV detectors and short-wavelength LEDs. Wafer growth involves subliming Acheson-produced SiC at 2,200-2,500°C, with methods like Lely and modified sublimation enabling single-crystal production. Recent breakthroughs include epitaxial growth on SiC substrates, reducing defects for devices such as JFETs and MOSFETs. Despite challenges like screw dislocations, ongoing R&D by firms like Cree has led to 75 mm wafers, with commercial sizes at 35 mm, promising applications in aerospace, automotive electronics, and radar systems.
SiC continues to permeate various industries, driven by ongoing research into preparation technologies. The Acheson method will maintain dominance in volume production, supporting applications in steelmaking and abrasives. Simultaneously, advanced techniques for high-density, high-strength ceramics will expand into high-tech sectors. Future efforts will focus on cost reduction, process optimization, and integration with sintering for optimal economic and performance outcomes. In electronics, SiC devices are poised for significant growth, revolutionizing fields like automation and communications.
What is Silicon Carbide (SiC)? SiC is a synthetic compound known for its hardness and heat resistance, widely used in industrial applications.
How is SiC primarily produced? The Acheson method is the main production technique, involving high-temperature reactions in electric furnaces.
What are the key applications of SiC? SiC is used in abrasives, refractories, electronics, and as a deoxidizer in steel production.
Why is China a leader in SiC production? Abundant resources and advanced facilities allow China to produce 40% of the global supply.
What are the environmental challenges with SiC production? Emissions like CO2 and SO2 pose issues, but innovations like gas capture systems are mitigating them.
How does SiC benefit the automotive industry? It enhances engine components for better efficiency and durability in high-temperature environments.
In summary, Silicon Carbide (SiC) stands as a pivotal material in modern industry, blending historical production methods with cutting-edge innovations to drive efficiency, sustainability, and technological advancement. Its widespread applications and ongoing developments ensure SiC remains essential for global trade and industrial growth, offering substantial value to manufacturers and engineers alike.
Tags: Black Silicon Carbide, White Fused Alumina, Brown Fused Alumina, Pink Fused Alumina, Black Fused Alumina
