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Scarce cubic silicon carbide materials from around the world attract customers from the United States and South Korea

Scarce cubic silicon carbide materials from around the world attract customers from the United States and South Korea

Silicon carbide (SiC) and gallium nitride (GaN) have also become widely known as key materials, but what most people don't know is that the most common and widely used in refractory, superhard abrasives, advanced ceramics and other industries is actually the alpha phase. Silicon carbide, which is a far cry from the low temperature stable β-phase silicon carbide that is really used in semiconductors. Β-SiC belongs to the cubic system (diamond crystal), which is cubic silicon carbide. In addition to its use in the third-generation semiconductor industry to prepare silicon carbide wafers, it has high chemical stability, high hardness, high thermal conductivity, low thermal expansion coefficient, wide energy band gap, high electron drift speed, and high electron migration. Rate, special resistance temperature characteristics, etc., are also widely used in precision machining technology, military industry, aerospace, advanced refractory materials, special ceramic materials, advanced grinding materials and and reinforcement materials, so it is also compared with α-SiC. The application scope and application capacity are much larger. For example, in the application of polishing and grinding, the sharp edges of β-SiC can improve the polishing efficiency; in the field of high-end special ceramics, adding β-SiC can improve the sintering activity of ceramics. Left: American customers, Right: South Korean customer cubic silicon carbide new materials, Xi'an Bor New Materials Co., Ltd. (hereinafter referred to as Bor New Materials), Xi'an University of Science and Technology, Shaanxi Provincial Silicon Magnesium Carbon Micro and Nano Materials Engineering Technology Research Center, experienced 26 years, successfully developed and produced. At present, the domestic market share is more than 95%, and the international market share is more than 50%. Only 4 companies in Japan, Germany, and the United States can produce in small batches. Due to the scarcity of products, high-tech barriers, and confidentiality, the market investment is very high. Small, which has attracted customers from the United States and South Korea. More than 10 companies from Japan, Germany, Switzerland, and Taiwan have recently sent letters to purchase these products. As of now, the company has built an industrialized demonstration production line with an annual output of 500T in Xi'an National Aviation High-tech Industrial Base. The production technology is the first in China, the world's leading, mature and reliable. For more than three years, the company has provided about 200 varieties of eight categories of market segment products to advanced manufacturing fields at home and abroad. Especially, the huge application potential of semiconductor chip substrates and ultra-fine abrasive materials has had a great impact on domestic and international markets. .
Silicon Carbide: The “Perfect Point” for Carbon Fiber Brake Pads

Silicon Carbide: The “Perfect Point” for Carbon Fiber Brake Pads

At present, brake pads are one of the most critical safety parts in the braking systems of heavy machinery such as cars, trains, and aircraft and tanks. The quality of the material of the brake pads directly affects the braking performance of the vehicle and is more related to the safety of the driver's life. Silicon carbide's low density, good oxidation resistance, high temperature resistance, and corrosion resistance make it occupy an important position in the field of brake systems. At the National Science and Technology Awards Conference held in January 2017, Academician Zhang Litong of Western Technology University won the second prize of National Technology Invention Award for "Silicon Carbide Ceramic Matrix Composite Aircraft Brake Disc Application Project." Status. Figure 1 Porsche brake pads (Image source: Cheshenbang.com) In order to further understand the application of silicon carbide in the field of brake pads, let's start with the performance that ideal brake pads should have. The ideal brake pad In the car's brake system, the brake pad is the most critical safety part. The vehicle's deceleration and stop all depend on the friction between the brake pad and the brake disc. The ideal brake pads should have the following properties: Table 1 Performance requirements of ideal brake pads and their explanations Silicon Carbide icing on the cake Materials ") to several generations of C / C-SiC composite materials (hereinafter referred to as" carbon ceramic materials "). Among them, powder metallurgy materials have defects such as high density, easy oxidation, and short service life. Carbon-carbon material brake pads have the advantages of smooth braking, low wear loss weight ratio, and large heat capacity on the basis of overcoming the defects of traditional materials. Figure 2 Copper-based powder metallurgy brake pads (Image source: HC Network) Carbon and carbon materials are mainly composed of carbon fibers, graphite and free carbon, while carbon ceramic materials are based on carbon and carbon materials, and silicon carbide ceramics are added, so it is called carbon pottery. The addition of silicon carbide has greatly improved the performance of carbon and carbon materials. Next, compare the specific tables to see how silicon carbide paints the "final touch" for carbon-carbon materials.的 Compete among masters ▶ Carbon materials and carbon ceramic materials are "nobles" in brake pads. They both have low density, large heat capacity, wear resistance, corrosion resistance and other outstanding advantages. The comprehensive performance is the general semi-metal brake pads. Incomparable. A set of Brembo brake systems imported from Italy is tens of thousands of yuan. The master's tricks can be compared in terms of mechanical properties and friction properties. Figure 3 The Brembo brake system is expensive (Image source: China Design Window) Researchers have prepared carbon-carbon composite materials through chemical vapor infiltration (CVI) processes, with a density of 1.7-1.75g ​​/ cm3 and a carbon fiber volume content of about 30. %; The carbon-ceramic composite material is prepared by CVI combined with reactive melt infiltration (RMI) process, with a density of about 2.1 g / cm3 and a carbon fiber volume content of about 30%. The mechanical properties were measured through a series of mechanical experiments, and Table 2 was obtained. Table 2 Comparison of mechanical properties of carbon-carbon materials and carbon-ceramic materials According to Table 2, it can be found that carbon-ceramic composite materials exhibit better static mechanical properties than carbon-carbon materials, such as tensile strength, compressive strength, and interlaminar shear strength. The internal shear strength is 44%, 67%, 100%, and 173% higher than that of carbon-carbon composites, respectively. Carbon ceramic materials also show excellent impact resistance, impact toughness up to 36kJ / m2, which is comparable to metal materials. Researchers tested the friction properties of carbon-carbon and carbon-ceramic brake materials using an electric inertia test bench, and obtained Table 3. Table 3 compares the dynamic friction coefficients of the two materials under different environments. Table 3 Comparison of friction properties between carbon and carbon materials and carbon ceramic materials According to Table 3, it can be found that the number of carbon and carbon materials decreases significantly under the conditions of fresh water and seawater, while the dynamic friction coefficient of carbon ceramic materials has not changed due to the addition of silicon carbide. . In summary, the addition of silicon carbide makes the carbon-carbon material no longer afraid of water, salt and other environments, and its wet and dry friction coefficient is equivalent. At the same time, silicon carbide increases the density of the carbon-carbon material, enhances the overall mechanical properties, and even impact toughness. The metal mater
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Time of issue:2019-04-29 00:00:00
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