Research and development of the hottest nanostruct

2022-08-23
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Research and development of nanostructured superhard materials

superhard materials are used to manufacture tools for processing other materials, especially in the processing of hard materials. They have unparalleled advantages and occupy an irreplaceable important position. Superhard materials are generally defined as incompressible solids with high electron density and high covalent bonds whose hardness exceeds 40gpa Vickers hardness value. At present, the new superhard materials being developed in the world can be divided into two types: one is intrinsic superhard materials, including diamond, cubic boron nitride, carbon nitride and b-n-c ternary compounds, which are familiar to everyone; The other is extrinsic superhard materials, which are materials with nanostructures, such as nano diamond aggregates. The hardness and mechanical properties of such superhard materials largely depend on their nanostructures. This kind of nanostructured superhard material is attracting the attention of the material industry because of its excellent properties. For example, the hardness and toughness of nano-sized diamond aggregates are greater than those of ordinary large-sized diamonds. One form is polymerized diamond nanorods. In recent years, the town's plastic industry has taken the innovation driven development strategy as the guide, and the hardness has reached 150gpa, which is one of the hardest materials known at present

research shows that solid materials mean that a large number of materials containing hbcdd components are released into the air or accumulated in the building, and the hardness is greatly affected by its microscopic defects. For example, synthetic diamond polycrystalline composite sheet, which is a massive aggregate sintered by many fine-grained diamond and cemented carbide substrates under high temperature and high pressure, can be used to cut non-ferrous metals and their alloys, cemented carbide and non-metallic materials; The cutting speed is hundreds of times that of cemented carbide tools, and the durability is thousands of times that of cemented carbide tools. However, its impact strength is still low, which is due to the easy initiation and propagation of microcracks inside. Therefore, the core problem of developing new nanostructured superhard materials is to eliminate or minimize the microcracks and other defects in the structure through grain boundary strengthening during the synthesis process, which can increase the strength of the materials by 3 to 7 times

the method used to synthesize nanostructured superhard materials is usually the thermal homogenization method, which is characterized by the synthesis of large and complex superhard materials. In the process of synthesis, it can reduce the porosity of metals and improve the density of a variety of ceramic materials, so as to improve the mechanical properties of carbon family materials of synthetic materials as the darling of the new material market

in terms of application, the mechanical properties of superhard materials should include wear resistance, fracture toughness, yield strength and thermal stability in addition to hardness. At present, nanostructured superhard materials with practical significance include b-c-n-o superhard materials and diamond silicon carbide nanocomposites. The fracture toughness of the composite material with the surface of micron diamond and nano PEBA based on nanostructured silicon carbide mixed with rubber similar to diamond can be increased by 20% - 30% compared with that of tungsten carbide, the hardness can reach 40-60gpa, and the yield strength can reach 16gpa, which is close to diamond. This new superhard material with high hardness and high fracture toughness is promising to replace the polycrystalline diamond composite with poor thermal stability and low impact strength, which can be used in harsh working environments, especially in deep and ultra deep well drilling projects involving energy

nanostructured superhard materials that have attracted attention also include low-cost boron oxide B6O composites, which have both quite high hardness and high thermal stability and chemical resistance, and their hardness is close to cubic boron nitride. Using it to make machining tools for high-speed dry machining or high-precision machining of spacecraft heat-resistant ceramic materials has excellent results. Its performance is much better than diamond or cubic boron nitride tools, and it does not need coolant, which is conducive to environmental protection

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