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Diamond Micropowder Knowledge

May 12,2023

1.Definition and classification of diamond powder
Generally speaking, powdered materials used for grinding and polishing with abrasive particle sizes less than 54 microns are referred to as micropowders. The micro powder processed using diamond as raw material is called diamond micro powder. In recent years, with the continuous expansion of new application fields, the particle size of many diamond micropowders has been far greater than 54 microns.
There are many types of diamond micropowders, and diamond micropowders produced from low strength synthetic diamonds through crushing, purification, grading, and other processes are the most common varieties. This type of product covers a particle size range of tens of nanometers to tens of micrometers, with high cost-effectiveness, and currently occupies the majority of the market share of diamond micro powder. With the continuous expansion of application fields, various types of diamond micropowders have emerged in the market according to their 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 for jewelry processing can be ground and crushed by ball milling to produce diamond powder, which can be used for industrial grinding and polishing, such as post processing of gemstones, precision parts, etc. With the rapid development of industry. The demand for diamond powder in the field of grinding and polishing has sharply increased, and the production of natural diamond powder is far from meeting market demand. The emergence of artificial diamonds has solved this problem, providing sufficient raw materials for diamond powder. Artificial diamond powder has a wide range of applications in the grinding of hard and brittle materials. As a powder material, it can be used for grinding and polishing various natural gemstones, artificial gemstones, glass, ceramics and other materials. Made into grinding fluid and paste, it can be used for cutting and polishing semiconductor materials such as silicon wafers, sapphire chips, and other components. It can also be made into various products, such as precision grinding wheels, diamond composite discs, precision grinding discs, wire drawing dies, etc. It can be used in geological drilling, optical glass processing, metal wire production and many other leading cities.

(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 micro powder produced using high-strength diamond as the raw material. Micro powder has high single particle strength, low internal impurity content, and low magnetism. The latter uses low strength diamond as the raw material. The product has good self sharpening performance.

(3) According to the different crystal structures of diamonds, they can be divided into single crystal diamond micropowders and polycrystalline diamond micropowders (as shown in the following figure). Due to the large production 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 powder


▲ Polycrystalline diamond powder

Single crystal diamond micropowder is made of synthetic diamond single crystal abrasive particles by static pressure method, which is crushed and shaped, and is produced by a special process of superhard material. Its particles retain the single crystal characteristics of single crystal diamond. Having a cleavage surface, it preferentially fractures along the cleavage surface when impacted by external forces, revealing new “cutting edges”.

Polycrystalline diamond micropowder is a micro and submicron polycrystalline particle formed by unsaturated bonding of diamond grains with a diameter of 5-10nm, which is isotropic and has no cleavage surface inside. Has high toughness. Due to its unique structural properties, it is commonly used for grinding and polishing semiconductor materials, precision ceramics, etc.

In addition, there is nanodiamonds produced by detonation method (as shown in the figure below). This kind of diamond is composed of redundant carbon atoms in negative oxygen balance explosives under appropriate detonation conditions. It is a secondary aggregate composed of diamond grains with the size of 5-20 nanoparticle. The powder appearance is generally gray black. nanodiamonds has good wear resistance, corrosion resistance and thermal conductivity, and can be used for precision polishing of hard disks, semiconductors, etc, It can be used as a lubricant additive to significantly improve the lubrication performance of lubricants, reduce wear, and strengthen product performance by adding it to rubber and plastic. It can also be used as an excellent functional material to coat metal molds, tools, components, and other surfaces, enhancing surface hardness, wear resistance, and thermal conductivity, and extending service life.


▲ Nano-diamond

2. Use of diamond powder
Diamond micropowder is widely used in machinery, aerospace, optical instrument, glass, ceramics, electronics, petroleum, geology, and military industries. It is an ideal material for grinding and polishing hard alloy ceramics, gemstones, optical glass and other hard materials.
Polycrystalline diamond powder utilizes good toughness to maintain high grinding force while avoiding scratches during the grinding and polishing process. It is widely used for grinding and polishing various hard materials such as optical crystals, ceramics, and superhard alloys.
Generally, diamond micropowders ranging from 0-0.5 microns to 6-12 microns are used for polishing; 10-15 microns to 22-36 microns for grinding; 12-22 microns or coarser are used for precision grinding.

3. Production process of diamond powder
Diamond raw materials → crushing and shaping → acid treatment → water washing → ultrasonic dispersion treatment → particle size grading → single particle acid treatment → drying → particle size inspection → weighing, packaging and warehousing.
Diamond micropowder is generally produced using low-tech materials, which is commonly referred to as the production of Class 1 materials. There are also some customized requirements and special applications that use three types of materials, such as diamond wire saws, glass drills, and other electroplating products.
Crushing and Forming of 4 Diamond Micropowders
Crushing and forming are key links in the production of diamond powder. The previous production process was dominated by ball milling, which was dominated by crushing, with moderate low-speed mechanical shock. Currently, it has been replaced by an air mill.
The working principle of airflow grinding: Compressed air is injected into the grinding chamber at high speed through a nozzle, and the diamond raw material repeatedly collides, rubs, and shears at the intersection of multiple high-pressure airflow, before being crushed. The particles are crushed by high-speed collision, and the surface of the particles is rubbed, sheared, and shaped.

Diamond micropowder is a superhard fine grinding and polishing material internationally today. In terms of particle size, it belongs to micron, submicron and nanometer powders. Compared with coarse powder, its specific surface area and specific surface functional groups significantly increase, resulting in a significant increase in the interaction force between particles during production. In addition, as the particle size is refined, the defects of the particles themselves decrease, and the strength inevitably increases. From this, it can be seen that the production process of diamond powder is quite difficult. It is not only a process of particle refinement, but also accompanied by changes in crystal structure and surface physicochemical properties. So the production process of diamond micro powder is an engineering and technical problem involving multiple disciplines such as 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 finish, such as computer disk heads, optical communication devices, optical crystals, semiconductor substrates, and other devices, which require precision polishing processing. If there are any protrusions, scratches, or attached foreign objects on the surface that exceed the allowable range, the designed accuracy and performance will not be guaranteed. In short, with the efforts of industry personnel in our country, the manufacturing level of diamond micropowder is improving year by year. With the same materials and equipment conditions, it has the highest cost-effectiveness in the world, but there is still a certain gap between it and international high-end micropowder. There are still many new problems in the production of diamond micropowder that need to be solved by peers, which is also our future development goal and task.

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