A definition and classification of diamond powder
Generally speaking, the powdery material for grinding and polishing with abrasive particle size less than 54 microns is called micropowder. The fine powder processed by using diamond as raw material is called diamond fine powder. In recent years, with the continuous expansion of new application fields, the particle size of many diamond micropowders has been much larger than 54 microns.
There are many types of diamond powder, and the diamond powder produced by crushing, purification, grading and other processes using low-strength artificial diamond as raw material is the most common variety. This type of product covers the particle size range from tens of nanometers to tens of microns, and the products are cost-effective. Currently, they occupy most of the market share of diamond micropowder. With the continuous expansion of application fields, various types of diamond micropowders have appeared on the market according to different uses.
1. According to different sources of raw materials, it can be divided into natural diamond powder and artificial diamond powder.
Low-grade natural diamonds that cannot be used in jewelry processing can be crushed by ball milling to produce diamond powder, which is used for industrial grinding and polishing, such as post-processing of gemstones and precision parts. With the rapid development of industry. The demand for diamond micropowder in the field of grinding and polishing has increased sharply, and the output of natural diamond micropowder is far from meeting the market demand. The emergence of artificial diamond has solved this problem, and it provides sufficient raw materials for diamond powder. Synthetic diamond powder is widely used in the grinding of hard and brittle materials. As a powder material, it can be used for grinding and polishing of various natural gemstones, artificial gemstones, glass, ceramics and other materials. Made into abrasive liquid and abrasive paste, it can be used for cutting, grinding and polishing of semiconductor materials such as silicon wafers, sapphire wafers and other components. It can also be made into a variety of products, such as precision grinding wheels, diamond composite sheets, fine grinding sheets, wire drawing dies, etc. It can be used in many fields such as geological drilling, optical glass processing, and wire production.
2. According to the strength of the raw material diamond, it can be divided into high-strength diamond powder and low-strength diamond powder.
The former is a micropowder produced using high-strength diamond as a raw material. Micropowder has high single-particle strength, low internal impurity content and low magnetic properties. The latter uses low-strength diamond as the raw material. The product has good self-sharpening.
3. According to the diamond crystal structure, it can be divided into single crystal diamond powder and polycrystalline diamond powder (as shown in the figure below). Due to the large output and wide application fields of single crystal diamond powder, diamond powder is generally referred to as single crystal diamond powder in the industry.
1. According to the different diamond crystal structure, it can be divided into single crystal diamond powder and polycrystalline diamond powder (as shown in the figure below). Due to the large output and wide application fields of single crystal diamond powder, diamond powder is generally referred to as single crystal diamond powder in the industry.
Single crystal diamond micropowder is produced by artificial diamond single crystal abrasive grains by static pressure method, after crushing and shaping treatment, it is produced by special process of superhard materials. Its particles retain the single crystal properties of single crystal diamond. It has a cleavage surface, and when it is impacted by an external force, it is preferentially broken along the cleavage surface, exposing a new "cutting edge". Polycrystalline diamond powder is a micron and submicron polycrystalline particle formed by diamond grains with a diameter of 5-10nm through unsaturated bonds, and the interior is isotropic and has no cleavage plane. Has high toughness. Due to its unique structural properties, it is often used in the grinding and polishing of semiconductor materials, precision ceramics, etc.
In addition, there are nano-diamonds produced by the detonation method (as shown in the figure below). This type of diamond is synthesized from the excess carbon atoms inside the negative oxygen balance explosive under appropriate detonation conditions, and consists of diamond grains with a particle size of 5 to 20 nanometers. The secondary agglomerates composed of powders are generally gray-black in appearance. Nano-diamonds have good wear resistance, corrosion resistance and thermal conductivity. They can be used for precision polishing of hard disks and semiconductors, and can be used as lubricating oil additives to significantly improve lubrication. Lubricating properties of oil, reducing wear, can be added to rubber and plastic to enhance product performance, and can also be used as an excellent functional material to coat the surface of metal molds, tools, components, etc., to enhance surface hardness, wear resistance, and thermal conductivity. Extended service life.
Two uses of diamond powder
Diamond micropowder is widely used in machinery, aerospace, optical instruments, glass, ceramics, electronics, petroleum, geology, and military industry. It is an ideal material for grinding and polishing hard alloy ceramics, gemstones, and optical glass. Polycrystalline diamond micropowder utilizes good toughness, can maintain high grinding force and is not easy to scratch during the grinding and polishing process, and is widely used in the grinding and polishing of various hard materials such as optical crystals, ceramics, and superhard alloys.
Generally, 0~0.5 micron diamond powder to 6~12 micron diamond powder is used for polishing; 10~15 micron to 22~36 micron is used for grinding; 12~22 micron is used for fine grinding.
Three production process of diamond powder
Diamond raw material→crushing and shaping→acid treatment→water washing→ultrasonic dispersion treatment→particle size classification→single particle size acid treatment→drying→particle size inspection→weighing, packaging and storage. Diamond micropowder is generally only produced with low-tech materials, which is what everyone calls the production of Class 1 materials. There are also some customized requirements and special applications, which will use three types of materials, such as diamond wire saws, glass drills and other electroplating products.
4. Grinding and Forming of Diamond Micropowder
Crushing and forming are the key links in the production of diamond micropowder. The previous production process was mainly based on ball milling, which was mainly crushed, with moderate low-speed mechanical impact. It has been replaced by jet mill at present.
The working principle of airflow grinding: compressed air is injected into the grinding chamber through the nozzle at high speed, and the diamond raw materials are repeatedly collided, rubbed and sheared at the intersection of multiple high-pressure airflows, and then crushed. The particles are crushed by high-speed collision, and the surface of the particles is crushed and formed by friction and shearing.
Diamond micropowder is a superhard fine grinding and polishing material in the world today. In terms of its particle size, it belongs to micron, submicron and nanometer powders. Compared with coarse-grained powder, its specific surface area and specific surface functional groups are significantly increased, so the interaction force between particles is greatly increased during production. In addition, with the refinement of the particle size, the defects of the particle itself 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 accompanied by changes in crystal structure and surface physical and chemical properties. Therefore, the production process of diamond micropowder is a multidisciplinary engineering technology problem involving machinery, powder engineering, mechanics, physical chemistry, modern instruments and testing technology.
With the development of cutting-edge technology and high-end manufacturing industry, the surface finish of many precision devices is very high, such as computer disk magnetic head optical communication devices, optical crystals, semiconductor substrates and other devices, all require precise polishing. Any bumps, scratches or attached foreign objects beyond the allowable range will not guarantee the accuracy and performance of the design. In short, with the efforts of our industry personnel, the manufacturing level of diamond micropowder in my country is improving year by year. Under the same material and equipment conditions, it has the highest cost performance in the world, but there is still a certain gap between the international high-end micropowder. The production of diamond micropowder is still There are many new problems that need to be overcome by colleagues, and this is also our future development goal and task.