With the development of cutting-edge technology and high-end manufacturing, many precision devices require high surface finishes. For example, computer disks, magnetic heads, optical communication devices, optical crystals, and semiconductor substrates all require precision polishing. Any irregularities, scratches, or adhesions of foreign objects beyond the allowable limits on the surface will not guarantee the accuracy and performance of the design. Therefore, the production of diamond micropowder shows the following trends:
First, the diamond powder production equipment automation
Diamond powder 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 of high-speed (above 9m/see) moving particles, roller type ball mill is The crushing function is mainly based on the crushing equipment with a suitable amount of low-speed mechanical impact. In terms of methods, the use of ball mills for diamond crushing to produce diamond micropowder is the most common method. Ball mill crushing method has been used in diamond micropowder production in China for many years, and has achieved satisfactory results. However, due to the disadvantage of low production efficiency, it has been replaced by a jet mill. The jet mill uses compressed air as the working medium. Compressed air is jetted at high speed through a special supersonic nozzle to the crushing chamber. The air stream carries material at high speed. Movement, so that the materials and materials have a 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 the mass and velocity. Fragmentation occurs when the force acting on a particle is greater than its breaking stress. High-velocity impact collisions cause the particles to undergo volumetric breakdown, while shearing and grinding results in surface disruption of the particles. This kind of crushing method is very advantageous for the production of diamond fine powder, because it can produce a more ideal particle shape. The greatest advantage of the jet mill is that it is not limited by the speed of the mechanical line, and it can generate very high airflow speeds. In particular, the supersonic jet mill can generate flow speeds that are several times the speed of sound, and thus it can generate huge kinetic energy and is relatively easy to obtain in the micron range. And submicron ultrafine powders. From the crushing principle, this model is more promising for diamond powder production.
Granularity classification is a very important process in the diamond micron production process. It involves the production efficiency and quality of diamond fine powder. At present, the most widely used diamond powder particle size classification method in China is the combination of natural sedimentation and centrifugal methods to produce fine powder. The natural settlement method is a sorting method that directly applies Stokes' law. According to the principle that particles of the same specific gravity have different sedimentation speeds in the water due to different particle sizes, the particle size can be classified by controlling its settling height and settling time. Simple, easy to operate, 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 material withdrawal, automatic water circulation and computer control, all-digital design, precise control, energy saving province Electricity has high efficiency, high reliability and good maneuverability that cannot be matched by humans. Than the manual separation efficiency can be increased by 10 to 20 times, with a high degree of automation, sorting speed, accurate sorting accuracy, no impurity contamination, no human factors interference, product quality, stability, good reproducibility, workers labor intensity The ten significant advantages of small, low-cost enterprise labor, and large quantities of disposable materials. In line with the direction of the future development of the powder industry.
Second, the classification of granularity, particle size range of centralized
With the advancement of science and technology, various processing accuracy requirements are getting higher and higher, and the particle size of the used powders is developing in a more subtle way. For example, the texture processing of computer hard disks has been rapidly changing since the start of the use of diamond powder 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) or even Finer level. As for the fine diamond powder of 2 micrometers, the national standard GB6966.1-1986 formulated in 1986 stipulates that there are 4 levels of 2 um diamond powder: 0-0.5, 0.5-1, 0.5-1.5, 0-2; The industry standard JB/T7990-1998 stipulates 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 powder has a finer particle size and narrower particle size range. Huifeng company is the largest manufacturer of diamond powder in China. In the diamond micropowder standard it formulates, 2 micrometers are finely 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 narrow scope of grain size can be regarded as the current international advanced level.
Third, high wear resistance of diamond powder
Domestic synthetic diamond micro-powders are mostly single-crystal diamonds based on type I materials. Due to the inherent characteristics of type I materials: high impurity content and low strength, they cannot meet the high-end market requirements for diamond micropowders. A few diamond micropowder manufacturers in China use type II or type III single crystal diamond as raw material to produce diamond micropowder. According to market feedback, the micropowder is much more efficient than ordinary diamond micropowder, and the wear resistance is improved by more than 30%. It is very effective for processing polygonal diamonds; processing silicon diodes and germanium diodes can achieve the highest level of mirror finish.
Fourth, special-purpose diamond powder
Different diamond powders have their own characteristics. According to different applications of diamond powder, a few domestic manufacturers are divided into: diamond cutters (PCD), petroleum composites (PDC), diamond wire saws, resin binder abrasives, metal binder products, abrasive pastes, grinding fluids and other special diamond powders. Meet different needs. This is China's diamond powder adjustment product structure, the development of the right direction to the specialization, but also an important step for China's diamond powder to catch up with the world advanced level.
Polycrystalline diamond micropowder is characterized by its brittleness, its particle shape is irregular, quasi-circular block, and the surface is rough and uneven. When the particles are subjected to stress, the brittleness causes the particles to crack, resulting in new sharp cutting points. Self-sharpening is better. This kind of diamond powder is more ideal for the production of resin bond grinding wheels, etc., and has a gentle refining and polishing effect.
Undoubtedly, diamond powder is an indispensable abrasive for the development of high, refined and sharp products. Its application has a very broad prospect and its application is expanding.