Comparison of high temperature and high pressure synthetic diamond with low temperature and low pressure synthetic diamond

Since the success of artificially grown diamonds, on the one hand, large quantities of industrial diamonds have been synthesized on the scale of production, and on the other hand, high-quality diamond large single crystals have been tried to meet its potential applications in electronic technology. I. High-temperature and high-pressure synthetic diamonds In 1954, Bundy et al. used metal catalysts to synthesize synthetic diamond single crystals for the first time under high temperature and high pressure conditions. Fig.1 Principle of conversion of rhombohedral graphite to cubic diamond: Using static ultrahigh pressure (50-100 kb, ie 5-10 GPa) and high temperature (1100-3000 °C) technology to react with carbonaceous materials such as graphite and certain metals (alloys) Diamonds are produced, which are typically cubic (hexahedral), octahedral and hexahedral and their transitional forms. With the development of high temperature and high pressure technology, the size of artificial single crystal diamond is getting larger and larger. Figure 2 Artificial diamond developed by Chinese researchers Figure 3. Various diamond products. Metal sintered polycrystalline diamond (PCD) developed in the 1970s, synthetic diamond material has become the only substitute for natural single crystal diamond. Fig. 4 Diamond polycrystalline diamond polycrystal is sintered by high-pressure and high-pressure diamond powder and a small amount of binder. It has high wear resistance, strong impact toughness, good thermal stability and uniform structure. It is widely used in manufacturing. Oil, geological drills and machining tools and gemstone processing. Second, low temperature low pressure synthetic diamond Figure 5 Schematic diagram of low temperature and low pressure synthetic diamond process Low temperature and low pressure preparation of diamonds began in 1970, before the Soviet Union Deryagin, Spitsyn and Fedoseev et al. Successful experiments. Before and after 1980, Japan Setaka et al. verified the gas phase on non-diamond substrates under low pressure conditions. Growing diamond crystals is feasible. Fig. 6 Schematic diagram of deposition of diamond film by ordinary CVD method Chemical phase deposition (CVD) diamond film under low temperature and low pressure is a hot research topic. Figure 7 CVD Diamond Film The advantage of CVD diamond film as a cutting tool material is its excellent combination of properties due to its unmatched hardness: 1. Good wear resistance and dimensional stability. 2. Has a small coefficient of friction. 3. Allow the tool to withstand aggressive machining temperatures up to 800 °C. 4. The chemical properties are more stable and resist the corrosion of the cutting fluid. Figure 8 Diamond Wheel Dressing Tool Today's CVD deposited diamond films are available in a variety of substrates, including silicon, stainless steel, titanium substrates, titanium alloys, tantalum, chromium, aluminum, copper, molybdenum, nickel, platinum, and others. Figure 9 CVD diamond coated tool However, the current production of CVD diamond film, as a cutting tool, needs further research and development. In summary, high-temperature and high-pressure synthetic diamonds have the following differences compared with low-temperature and low-pressure synthetic diamonds: 1. The carbon source for conversion to diamond is different. At high temperature and high pressure, graphite and other raw materials are used, while low temperature and low pressure are selected methane and carbon monoxide. 2. The carbon source generated by the high temperature and high pressure is a stable phase, and the diamond formed by the low temperature and low pressure is an unstable phase. 3. The diamond particles synthesized under high temperature and high pressure are large, and the large single crystal can be synthesized at a high temperature and high temperature. However, it has not been realized under low temperature and low pressure, and the polycrystalline diamond film is synthesized under low temperature and low pressure. 4. The high temperature and high pressure process is relatively mature, and there are some industrial applications, and the low temperature and low pressure are still in the exploration stage, but the prospect is broad.