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Henan Huifeng Diamond Co., Ltd. Zhu Shilian Abstract Diamond micropowder belongs to micron, submicron and nano powder, and the production process is very difficult. It is a multi-disciplinary engineering and technical issue. With the development of science and technology, there are some notable development trends in the production of diamond micropowder. Key words diamond micropowder; particle size classification; development trend Preface Diamond micropowder is a superhard fine grinding and polishing material in the world. It is micron, submicron and nano powder in terms of its particle size. Compared with the coarse-grained powder, its specific surface area and specific surface functional groups are significantly increased, so that the forces between the particles greatly increase during the production process. In addition, as the particle size is refined, the defects of the particles themselves are reduced, and the strength is inevitably increased. It can be seen that the production process of diamond micropowder is quite difficult. It is not only the process of grain refinement, but also accompanied by changes in crystal structure and surface physicochemical properties. Therefore, the production process of diamond micropowder is a multi-disciplinary engineering and technical issue involving machinery, powder engineering, mechanics, physical chemistry, modern instruments and testing technology. With the development of cutting-edge technology and high-end manufacturing, many precision devices require high surface finishes, such as computer disks, magnetic heads, optical communication devices, optical crystals, semiconductor substrates, etc., which require precise polishing. Any unevenness, scratches or foreign matter on the surface beyond the permitted range will not be guaranteed. Therefore, the production of diamond micropowder has the following development trends: First, the automated diamond micropowder of diamond micropowder production equipment is obtained by crushing and classifying coarse-grained single crystal diamond. In general, there are three basic mechanisms for crushing moderately coarse material into micron or submicron particle size, namely crushing, mechanical impact {direct collision and grinding between moving particles at high speed (above 9 m/see), and the drum ball mill is A crushing device that is mainly composed of crushing action and has a moderate amount of low-speed mechanical impact. As far as the method is concerned, the use of a ball mill to crush diamond to produce diamond micropowder is the most commonly used method. The ball mill crushing method has been used in the production of diamond micropowder in China for many years and has achieved satisfactory results. However, due to the shortcomings of low production efficiency, it has been replaced by a jet mill, which uses compressed air as a working medium, and compressed air is sprayed at a high speed through a special supersonic nozzle to the crushing chamber. Movement, so that the material and the material between the strong collision, friction and shear to achieve the purpose of crushing. According to the kinetic energy formula, the magnitude of kinetic energy is proportional to the square of mass and velocity. Breakage occurs when the force acting on the particle is greater than its breaking stress. High-speed impact collisions cause the particles to be broken in volume, while shearing and grinding cause surface breakage of the particles. This method of crushing is advantageous for the production of diamond micropowder because it can produce a desired particle shape. The biggest advantage of the jet mill is that it is not limited by the mechanical linear velocity and can generate high airflow speed. Especially, the supersonic jet mill can generate several times the speed of sound velocity, which can generate huge kinetic energy and is easy to obtain micron level. And submicron ultrafine powder. From the principle of pulverization, this type of machine is more promising for the production of diamond micropowder. Particle size classification is an important process in the production of diamond micropowder. It involves the production efficiency and quality of diamond micropowder. At present, one of the most widely used diamond micropowder size fractionation methods in China is the combination of natural sedimentation method and centrifugal method to produce micropowder. The natural sedimentation method is a sorting method that directly applies Stokes's law. According to the principle that the same specific gravity of the particles in the water has different sedimentation speeds in water, the sedimentation height and settling time are controlled to classify the particle size, although the equipment Simple, easy to operate, and stable in quality, but with a long production cycle and low labor efficiency. To this end, many domestic and foreign manufacturers have developed automated grading equipment, using computer technology and variable frequency control technology, set up four systems of automatic mixing, automatic pumping, automatic water circulation and computer control, all digital design, precise control, energy saving Electricity, with unmatched efficiency, high reliability and good handling. It can increase the efficiency by 10 to 20 times than manual sorting. It has high automation, fast sorting speed, accurate sorting accuracy, no impurity pollution, no interference from people, strong product quality stability, good reproducibility, and labor intensity. The ten major advantages of small, low labor costs and large one-time feeds are significant. In line with the future development of the micronized industry. Second, the granularity of the subdivision, the concentration of the particle size range With the advancement of science and technology, the processing precision requirements are getting higher and higher, the fine particle size used in the direction of more subtle. For example, the texture processing of computer hard disks has been changing rapidly since the use of diamond micropowder in the 1990s. From the beginning of about 1 micron to the current 0.1 micron, it will soon transition to 0.05 micron (50 nm) and even soon. A finer level. In the case of 2 micron fine diamond powder, the national standard GB6966.1-1986, which was established in 1986, stipulates that 2um diamond micropowder has four grades: 0-0.5, 0.5-1, 0.5-1.5, 0-2; The industry standard JB/T7990-1998 specifies that 2 micron fine diamond powder has 6 grades: 0-0.5, 0-1, 0.5-1, 0.5-1.5, 0-2, 1-2; from the manufacturer's standard The diamond micropowder has a finer particle size and a narrower particle size range. Huifeng is the largest manufacturer of diamond micropowders in China. In the standard of diamond micropowder formulated by it, 2 micron is divided into 12 levels: 0-0.06, 0-0.1, 0-0.125, 0-0.2, 0-0.25, 0.1-0.25, 0.2-0.5, 0.25-1. 0.5-1, 0.5-1.5, 0-2, 1-2. The range of the grain size is very narrow and can be regarded as the current international advanced level. 3. Diamond powder with high wear resistance The domestic diamond powder is mostly made of single crystal diamond of type I. Due to the inherent characteristics of type I material: high impurity content and low strength, it can not meet the high-end market for diamond powder. Claim. A small number of diamond micronized powder manufacturers in China use the single crystal diamond of type II or III as raw material to produce diamond micropowder. According to market feedback, the processing efficiency of the micropowder is much larger than that of ordinary diamond micropowder, and the wear resistance is improved by more than 30%. It is very effective for processing polygonal diamonds; components such as silicon diodes and germanium diodes can achieve the highest level of mirror finish. 4. Special diamond powders Different diamond powders have their own characteristics. A small number of domestic manufacturers are divided into: diamond chip (PCD), petroleum composite sheet (PDC), diamond wire saw, resin bond abrasive, metal bond product, abrasive paste, polishing liquid and other special diamond powder. Meet different needs. This is the correct direction for the adjustment of product structure of diamond micropowder in China, and it is also an important step for China's diamond micropowder to catch up with the world's advanced level. Polycrystalline diamond micropowder is characterized by brittleness, and its particle shape is irregular and quasi-round block. The surface is rough and uneven. When the particles are under stress, the brittleness causes the particles to break, resulting in new sharp cutting points. Self-sharpness is better. Such diamond micropowder is more ideal for the manufacture of resin binder grinding wheels, and has a gentle refining and polishing action. Undoubtedly, diamond micropowder is an indispensable abrasive for the development of high, fine and sharp products. Its application has a very broad prospect and its application field is expanding. V. At the end of the development of diamond micropowder manufacturing technology, there are still many new problems. For example, in the aspect of nano-diamond micro-powder de-agglomeration, some people adopt the surface modification method, some adopt the critical drying method to solve the existence of hard agglomerates in the powder drying process, and the formulation of new standards, etc., in short, Under the unremitting efforts of our country's industrial technicians, China's diamond micropowder manufacturing level is constantly improving. We can proudly believe that under the same materials and equipment conditions, our diamond micropowder has the highest price/performance ratio in the world, but compared with the international market. The diamond micro-powder, our products are still relatively rough, especially the subdivision is not very detailed, this is our goal of future tasks and development. References: 1, Li Fengsheng, etc.: ultra-fine powder technology {M} Beijing, National Defense Industry Press. 2000 2. Tan Yaolin: Definition of Diamond Micropowder, Minerals and Geology, No. 3, 1997 3. Zhu Shilian: A Nanocrystalline Single Crystal Diamond and Manufacturing Method Patent Publication No.: CN1962964A 4. Tan Yaolin: Technical Standard for Diamond Micropowder , Geology and Exploration, No. 1, 1996
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