Brief analysis on the production and application of diamond powder
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Diamond micropowder refers to the diamond particles with particle size smaller than 60 microns, and there are two types of single-crystal diamond micropowder and polycrystalline diamond micropowder.
1. Monocrystalline diamond powder is made up of synthetic diamond monocrystalline abrasive particles, which are processed by grinding, shaping and special processing methods.
2. Polycrystalline diamond micropowder is made from graphite by using a unique directional blasting method. The shock wave of directional blasting of high explosive speed accelerates the flight of the metal flying sheet and impacts the graphite sheet, thus resulting in the transformation of graphite into polycrystalline diamond.
Diamond powder has high hardness and good wear resistance, and can be widely used in cutting, grinding, drilling and so on. It is an ideal raw material for grinding and polishing hard alloy, ceramics, gemstones, optical glass and other high hardness materials. Diamond powder products are tools and components made of diamond powder.
Diamond powder belongs to micron, submicron and nanometer powder in terms of its particle size. Compared with coarse powder, the specific surface area and specific surface functional groups increase obviously, so the force between particles increases greatly in the production process. In addition, with the refinement of particle size, the defect of the particle itself will decrease, and the strength will inevitably increase. It can be seen that the production process of diamond powder is quite difficult, which is not only a process of particle refinement, but also accompanied by changes in crystal structure and surface physical and chemical properties. Therefore, the production process of diamond powder is a multidisciplinary engineering and technical problem involving machinery, powder engineering, mechanics, physical chemistry, modern instruments and testing technology.
Diamond powder production equipment
Diamond powder is obtained by crushing and classifying coarse grain single crystal diamond. The ball mill is the most commonly used method to produce the diamond powder by crushing the diamond. The ball mill crushing method has been used for many years in the production of diamond powder in China, and has achieved satisfactory results. But because of the disadvantage of low efficiency, has now been replaced by jet mill, jet mill is compressed air as working medium, the compressed air through the special supersonic nozzle high-speed jet into the crushing chamber, the high speed air flow to carry material movement, the intense collision between the material and the material, friction and shear so as to achieve the aim of crushing. The biggest advantage of the airflow crusher is not limited by the mechanical linear speed, can produce a high airflow speed, especially the supersonic airflow crushing function produces several times the speed of sound velocity, thus can produce huge kinetic energy, it is easier to obtain micron and submicron ultrafine powder. In terms of grinding principle, this kind of machine is more promising for the production of diamond powder.
Strength grading technology of diamond powder
Particle size classification is an important process in the production of diamond powder. It relates to the production efficiency and quality of diamond powder. At present, the most widely used particle size grading method for diamond powder is the technology of natural sedimentation and centrifugal method.
Natural sedimentation method is a direct application of the stokes law separation method, according to the same proportion of particle settling velocity is also different because of different particle size in water, the principle of the grading by controlling its height and subsidence time granularity, although simple equipment, easy operation, stable quality, but a longer production cycle, low labor efficiency. For this reason, many manufacturers at home and abroad developed automated grading equipment, USES the computer technology and frequency conversion control technology, set up automatic stirring, automatic extraction material, automatic water cycle and four systems, computer control the whole digital design, control precision, saving energy save electricity, has manual incomparable high efficiency, high reliability and good handling. Compared with manual separation efficiency can be improved 10 to 20 times, with a high degree of automation, separation speed, separation accuracy, no impurity pollution, no human factors interference, product quality stability, good reproducibility, low labor intensity of workers, enterprise labor cost, one-time investment of the ten significant advantages. In line with the future development direction of micro powder industry.
Brief introduction of application of several types of diamond powder
Traditional diamond powders can be divided into two categories polycrystalline diamond powders and monocrystalline diamond powders. With the rapid development of nano-technology, a new type of nano-diamond powder, nano-diamond powder, has emerged independently from the original two kinds of diamond powder. See below for their main USES.
1. Polycrystalline diamond powder
Polycrystalline diamond is synthesized under the action of transient strong shock wave formed by explosion. It is composed of nanocrystals of micron and submicron grade polycrystalline, polycrystalline due to isotropy, no cleavage surface, impact resistance, bending strength is high, so it has both the hardness of superhard material, but also nanocrystals extraordinary high strength and high toughness. Its dual advantages constitute its unique physical properties, which have important applications in high-tech industries and traditional pillar industries.
Application: it is mainly used in the fields of chip optical crystal \ ultra-fine processing, large-scale silicon wafer ultra-fine polishing, surface modification, etc. The spherical polycrystalline diamond powder has a grey-black appearance and slightly metallic luster.
2. Single crystal diamond powder
The crystal shape of single crystal diamond powder is regular and complete hexahedral, with high strength, toughness, good thermal stability and strong impact resistance. The main USES are: suitable for electroplating products, grinding wheel, grinding wheel manufacturing, for high-grade stone polishing, carving, automotive glass, high-grade furniture, ceramics, cemented carbide, magnetic materials processing.
3. Nano diamond powder
Nano-diamond powder not only has the inherent characteristics of diamond, but also has small size effect, large specific surface area effect, quantum size effect and so on, thus showing the characteristics of nano-materials. The diamond synthesized in detonation wave has cubic structure, lattice constant of (0.3562+0.0003)nm, crystal density of 3.1g/cm3, specific surface area of 300m2/g ~ 390m2/g. After different chemical treatments, various functional groups can be formed on the surface of diamond, which has a high adsorption capacity.
Other USES of nano-diamond:
A. prepare advanced grinding paste and polishing fluid for ultra-fine machining of quartz, optical glass, semiconductor, alloy and metal surface.
B. Preparation of catalysts: nano-level diamond and amorphous carbon have a large specific surface area, contain a variety of surface functional groups, and are highly active. Preparation of catalysts with them can improve the activity data and promote the interaction of organic compounds.
C. Preparation of nano-composite structural materials: by combining nano-diamond with nano-silicon powder, nano-ceramics and various nano-metals, new nano-structural materials can be produced. Due to its unique properties, semiconductor devices, integrated circuit components and microcomputer parts can be manufactured.
With the increasing maturity of the diamond tool manufacturing industry and the rapid growth of China's economy, the market demand for diamond powder in China is also growing rapidly. The progress of tool manufacturing technology also puts forward higher requirements for the upstream diamond powder industry. Due to the characteristics of different crystalline diamond powders with different grain sizes, a few domestic manufacturers have been able to produce different types of diamond powders according to their different USES. For example: tool pieces (PCD), resin bonded abrasive tools, metal bonded products, grinding paste special diamond powder and so on. This is an important step for China's diamond powder industry to upgrade and adjust the product structure, develop towards high-end specialization, and catch up with the advanced level of the world.
As a kind of super hard abrasive, diamond powder has an extremely superior grinding ability, which has been paid more and more attention by industrial developed countries. The grinding ability of diamond powder includes the grinding ability of workpiece and its own abrasion resistance and crushing resistance, which depends on its microhardness, particle size, strength, particle shape, thermal stability and chemical stability. fgfwefwefcs