March 16, 2016
Diamond powder refers to diamond particles finer than 60 microns. There are two types of single crystal diamond powder and polycrystalline diamond powder. Single crystal diamond powder is produced from synthetic diamond single crystal abrasive grains, which are crushed and shaped, and produced by a special process. Polycrystalline diamond powder is made of graphite using a unique directional blasting method. The shock wave of the directional blasting of high-speed explosives accelerates the flight of metal flying pieces and hits the graphite pieces to cause the graphite to be converted into polycrystalline diamond. Diamond powder has high hardness and good wear resistance, and can be widely used in cutting, grinding, drilling, etc. It is an ideal raw material for grinding and polishing hard alloys, ceramics, gems, optical glass and other high-hardness materials. Diamond powder products are tools and components made by processing diamond powder.
Diamond powder belongs to micron, sub-micron and nano-powder in terms of its particle size. Compared with coarse-grained powder, its specific surface area and specific surface functional groups are significantly increased, so in the production process, the force between the particles is greatly increased. In addition, with the refinement of the particle size, the defects of the particles themselves are reduced, and the strength is bound to increase. It can be seen that the production process of diamond micropowder is quite difficult. It is not only a process of particle refinement, but also changes in crystal structure and surface physical and chemical properties. Therefore, the production process of diamond micropowder is a multi-disciplinary engineering technology issue involving machinery, powder engineering, mechanics, physical chemistry, modern instrumentation and testing technology.
Diamond powder production equipment
Diamond powder is obtained by crushing and grading coarse-grained single crystal diamond. It is the most commonly used method to produce diamond powder by using a ball mill to crush the diamond. The ball mill crushing method has been used in the production of diamond powder in my country for many years and has achieved satisfactory results. However, due to the shortcomings of low production efficiency, it has been replaced by jet mills. Jet mills use compressed air as the working medium. The compressed air is sprayed into the crushing chamber at high speed through special supersonic nozzles. The airflow carries materials at high speeds. Make strong collision, friction and shear between the material and the material to achieve the purpose of crushing. The biggest advantage of the jet mill is that it is not limited by the mechanical linear velocity and can produce high air velocity, especially the supersonic jet mill can produce a flow velocity several times the speed of sound, so it can generate huge kinetic energy, and it is easier to obtain micron level And sub-micron ultrafine powder. In terms of crushing principle, this type of machine is more promising for the production of fine diamond powder.
Strength classification process of diamond powder
Grading is a very important process in the production process of diamond micropowder. It involves the production efficiency and quality of diamond micropowder. At present, the most widely used diamond micropowder particle size classification method in China is the combination of natural sedimentation and centrifugal methods to produce micropowder. The natural sedimentation method is a sorting method that directly applies Stokes's law. According to the principle that particles of the same specific gravity have different sedimentation speeds in water due to different particle sizes, the particle size can be classified by controlling the sedimentation height and sedimentation time. It is simple, easy to operate, and stable in quality, but has 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 frequency conversion control technology, equipped with four systems of automatic mixing, automatic pumping, automatic water circulation and computer control. All-digital design, precise control, and energy-saving Electricity, with high efficiency, high reliability and good maneuverability unmatched by humans. Compared with manual sorting efficiency, it can be increased by 10-20 times. It has high degree of automation, fast sorting speed, accurate sorting accuracy, no impurity pollution, unmanned factor interference, strong product quality stability, good reproducibility, and labor intensity. Ten significant advantages of small size, low labor cost of enterprises, and large amount of one-time feeding. It is in line with the future development direction of the micro powder industry.
Brief introduction of several types of diamond powder
Traditional diamond powder can be divided into two categories, polycrystalline diamond powder and single crystal diamond powder. With the rapid development of nanotechnology, a new type has been independently developed among the original two major diamond-like powders: nano-diamond powder. Please refer to the following for their respective main purposes.
Polycrystalline diamond powder：
Polycrystalline diamond is synthesized under the action of a transient strong shock wave formed by an explosion. It is a micron and sub-micron polycrystalline composed of nanocrystals. Polycrystalline is isotropic, has no cleavage surface, impact resistance, and high bending strength. Therefore, it not only has the hardness of superhard materials, but also has nanometers. The material has exceptional high strength and high toughness. Its dual advantages constitute its unique physical properties, and it has important applications in high-tech industries and traditional pillar industries.
Uses: Mainly used in the fields of chip optical crystal ultra-fine processing, large-scale silicon wafer ultra-precision polishing, surface modification, etc. The spherical polycrystalline diamond powder has a gray-black appearance with a slight metallic luster.
Single crystal diamond powder：
The crystal shape of single crystal diamond powder is regular and complete hexa-octahedron, with high strength, toughness and good thermal stability, and strong impact resistance. The main uses are: suitable for the manufacture of electroplated products, grinding wheels, and grinding wheels, and for the polishing and engraving of high-end stone, the processing of automotive glass, high-end furniture, ceramics, hard alloys, and magnetic materials.
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, etc., thus exhibiting the characteristics of nanomaterials. The diamond synthesized in the detonation wave has a cubic structure with a lattice constant of (0.3562+0.0003) nm, a crystal density of 3.1 g/cm3, and a specific surface area of 300 m2/g～390 m2/g. After different chemical treatments, a variety of different functional groups can be formed on the diamond surface. This diamond crystal has a high adsorption capacity.
Other uses of nano-diamond：
A. Preparing advanced grinding paste and polishing liquid for ultra-fine processing of quartz, optical glass, semiconductor, alloy and metal surfaces.
B. Preparation of catalyst: Nano-diamond and amorphous carbon have a large specific surface area, contain a variety of surface functional groups, and are very active. The preparation of a catalyst can improve the activity data and promote the interaction of organic compounds.
C. Preparation of nano-composite structural materials: composite nano-diamonds with nano-silicon powder, nano-ceramics and various nano-metals can produce new nano-structure materials. Because of their unique properties, they can be used to manufacture semiconductor devices, integrated circuit components and Computer parts.
With the growing maturity of the diamond tool manufacturing industry and the rapid growth of China's economy, my country's market demand for diamond micropowder is also growing rapidly. The advancement of tool manufacturing technology has also put forward higher requirements for the upstream diamond powder industry. Because diamond powders of different crystalline states and different particle types have their own characteristics, a few domestic manufacturers have been able to produce different types of diamond powder according to the different uses of diamond powder. For example: cutting tools (PCD), resin bond abrasive tools, metal bond products, special diamond powder for grinding paste, etc. This is an important step for my country's diamond micropowder industry to upgrade and adjust its product structure, develop towards high-end specialization, and catch up with the world's advanced level.