The difference between diamond monocrystalline, polycrystalline, polycrystalline-like, polycrystalline

Diamond is a super-hard material that we are all very familiar with. There are many different types of diamond crystals, each with different characteristics and applications. In this article, we will sort out the different types and applications of diamond crystals.

I. Diamond Single Crystal

Diamond single crystal is a crystal with the same atomic arrangement and the same lattice phase, it is the most common type of diamond crystal, it has very high hardness and excellent thermal conductivity and other properties.

1. Crystal structure: diamond single crystal is a crystal combined by covalent bonds with saturation and directionality, the particles inside the crystal are regularly and contemporaneously arranged in three-dimensional space, or the whole crystal is composed of the same space lattice in the three-dimensional direction, and the arrangement of the plasmodesmata in the space of the whole crystal is long-range and orderly. The crystal structure is uniform and complete, with uniform chemical and thermodynamic properties.

2. Manufacturing method: synthesized under thermodynamically stable high temperature and high pressure and catalyst participation, basically domestic synthesis using six-sided top press.

3. Physical properties: diamond single crystal has high hardness, good anti-wear performance, good thermal conductivity and high temperature resistance, and can maintain stable physical and chemical properties under high temperature and high pressure environment.

4. Cutting performance: diamond single crystal can be used in cutting tools, abrasives, high-voltage electrodes and high-efficiency optical devices and other fields.

Second, diamond polycrystalline

Diamond polycrystalline is composed of many small grains with the same arrangement but inconsistent orientation. Polycrystalline diamond was originally invented by DuPont in the United States.

1. Grain structure: polycrystalline diamond is made up of numerous tiny nano-sized particles aggregated, after purification and grading and other subsequent processing to obtain polycrystalline diamond micropowder of different particle size ranges, the particle size is generally not more than 10 microns. The crystal structure is inhomogeneous, with severe and fragile defects and an irregular shape with sharp edges. The structure is very similar to natural Carbonado. Combined by unsaturated bonds, it has very good toughness.

2. Manufacturing method: diamond polycrystalline (micropowder) is the use of a unique blasting method from graphite, high explosive velocity explosives directional blasting shockwave generated by high temperature and high pressure, the metal flying piece of accelerated flight impact on the graphite flake, which led to the transformation of graphite into polycrystalline diamond. Generally only a few microseconds of the moment, the product is mostly 5-20 nanometer fine polycrystalline.

3. Physical properties: diamond polycrystalline hardness is not as high as single crystal, but still has excellent wear resistance and thermal conductivity, and can maintain a certain degree of stability at high temperature and high pressure environment.

4. Grinding performance: diamond polycrystalline cutting performance is not as good as monocrystalline, but it has unique toughness and self-sharpening, polycrystalline diamond has more crystal prongs and grinding surfaces, in the grinding process, each crystal prong has a grinding force, and the coarse particles will be broken off into smaller particles during the grinding process, so that it can maintain a continuous grinding force, and also to avoid sharp edges and corners on the surface of the workpiece caused by scratches, which can not only ensure the quality of grinding and polishing of the surface, but also improve the quality of the samples. This not only ensures the grinding quality of the sample surface, but also improves the grinding and cutting efficiency. Compared with monocrystalline diamond, it is more suitable for grinding workpieces whose surfaces are composed of different hardness materials.

Therefore, polycrystalline diamonds are mostly used in the following applications:

As a precision abrasive, polycrystalline diamond is used for ultra-precision grinding and polishing of sapphire, magnetic heads, hard disks, hard glass and crystals, ceramics as well as hard alloys, e.g. for thinning of LED sapphire.

As a coating additive, polycrystalline diamond is used for coating metal molds, tools, parts, etc., which can greatly improve surface wear resistance, surface hardness, and prolong service life.

For grinding, polycrystalline diamond can generally be formulated into grinding solution for use.

Polycrystalline diamond can also be used to make knives, which are not prone to chipping when cutting.

Third, diamond-like polycrystalline

Since polycrystalline diamond has a great market demand, it has given rise to polycrystalline diamond-like products. Class polycrystalline, that is, the use of single-crystal diamond as raw materials, after the surface etching treatment to form a honeycomb pore structure, so as to achieve a similar effect of grinding and polishing of polycrystalline diamond, so it is called "class polycrystalline" diamond.

Polycrystalline diamond powder is a new type of abrasive between monocrystalline diamond and polycrystalline diamond. It is made of monocrystalline diamond powder by special process.

Diamond Polycrystalline

Artificial diamond polycrystalline is a kind of diamond and bonding agent in high temperature, high pressure conditions sintered diamond polymer, which has a very high heat resistance and high thermal stability. It is widely used in the manufacture of oil, geological drill bits, diamond processing and machining tools.

V. Summary

These crystals can be simply distinguished from the following aspects:

1. Production method: monocrystalline diamond is synthesized by graphite and catalyst through six-sided top press; polycrystalline diamond is synthesized by explosion method; the preparation of diamond polycrystalline is relatively simple, low cost, and is widely used in the fields of grinding wheels and abrasives. Polycrystalline diamond is a diamond polymer made by sintering monocrystalline diamond and bonding agent under high temperature and high pressure.

2. From the microstructure point of view: in the growth process of diamond there will be many kinds of crystal faces, such as (100), (110), (111) faces, if alone in accordance with the epitaxial growth of a certain crystal face law, the formation of monocrystalline, and if it is a mixture of the growth is polycrystalline.