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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
The secret of BYD's electric car battery life with high energy consumption and low energy consumption

The secret of BYD's electric car battery life with high energy consumption and low energy consumption

BYD IGBT4.0 wafer IGBT (InsulatedGateBipolarTransistor) stands for "Insulated Gate Bipolar Transistor". Its chip and power battery cells are also called "dual-core" for electric vehicles. It is a key technology that affects the performance of electric vehicles. Its cost accounts for 5% of the entire vehicle cost. about. For electric vehicles, the IGBT directly controls the conversion of the drive system's direct and alternating current, which determines the vehicle's torque and maximum output power. Thanks to its strong capabilities in core technology areas such as IGBT, BYD's ultra-high battery life and low energy consumption were realized. As China's first car company to achieve mass production of automotive-grade IGBTs and the only car company with a complete IGBT industrial chain, BYD also released another blockbuster news: BYD has invested heavily in the layout of performance More excellent third-generation semiconductor material SiC (silicon carbide) is expected to launch electric vehicles equipped with SiC electronic control in 2019. By 2023, BYD's electric vehicles will be fully equipped with SiC electronic control. Although IGBTs will still be in short supply for a long time to come. However, BYD has also foreseen that with the continuous improvement of electric vehicle performance, higher requirements are imposed on power semiconductor components, and the current IGBT will also approach the performance limit of silicon materials. The search for new semiconductor materials with lower chip losses, stronger current output capabilities, and higher temperature resistance has become a general consensus among the academic community and the industry. It is reported that BYD has invested heavily in the layout of the third-generation semiconductor material SiC, and will integrate the entire industrial chain of SiC-based semiconductors such as materials (high-purity silicon carbide powder), single crystal, epitaxy, chips, and packaging, and is committed to reducing the manufacturing of SiC devices. Cost to accelerate its application in the field of electric vehicles. At present, the only electric vehicle on the market that uses SiC silicon carbide power semiconductor components is Tesla's Model 3, which uses 650V SiCmosfet from STMicroelectronics. Compared with the traditional IGBT on ModelS / X, SiCmosfet can bring efficiency improvement of 5-8%, which plays a significant role in improving the endurance and reducing energy consumption performance. In addition, SiCmosfet also has a huge advantage in high-temperature performance, which can maintain a normal efficiency performance within 200 ℃, which provides the possibility for the development of high-performance electric vehicles. 意 After ST France, Infineon Germany has also started the supply of SiC power semiconductors, and its partners are also Tesla. In other words, almost all SiC power semiconductors on the global market have been purchased by Tesla. If BYD successfully launches car-grade SiC power semiconductors in 2019 and applies them to its high-performance models, BYD will undoubtedly establish its position as a brother in the domestic new energy market, and it will truly be in terms of performance and endurance. It is close to Tesla and it has opened a gap with other domestic companies. In 2018, the company's product "cubic silicon carbide fine powder" was reviewed by an expert group organized by the Provincial Ministry of Industry and Information Technology in conjunction with the Provincial Department of Finance, and was identified as "the first batch of domestic key new material application products." This is undoubtedly the product, the company Fully sure! After 30 years of research and development, the company's research and development team has been consistent and strives for excellence, and has only today's glory. At the end of 2017, the company passed the identification of "Xi'an High-tech Enterprise" and "National High-Tech Enterprise" respectively. In 2018, the company's chairman and team leader, Professor Wang Xiaogang, was awarded the "Xi'an Entrepreneur Hero" and "Xi'an Top Ten Entrepreneur Outstanding" People ". The produced cubic silicon carbide fine powder has high purity, narrow particle size distribution, large bulk density, high sintering activity, and regular crystal structure. The company has pioneered the mass production of nanometer silicon carbide....
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Time of issue:2019-04-29 00:00:00
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