Made in China! China's artificial diamond industry with great potential

1. Overview of artificial diamond industry development

The chemical composition of diamond is carbon (C), which is a kind of allotrope of carbon. With a density of 3.52g/cm³ and a hardness of 10 Moes, diamond is the hardest substance known to mankind in nature. According to the origin of diamond can be divided into natural diamond and artificial diamond.

Natural diamond is a kind of rare and valuable non-metallic mineral, among which gem-grade diamond with high quality and large grain, which can be used to make jewelry is called natural diamond. Natural diamond primary mines are mainly distributed in South Africa, Zaire, Botswana, Russia, Australia and other countries, and the mineral reserves are not high and the mining is difficult. Natural diamond ore is a non-renewable resource with rare mineral reserves, high mining cost and high damage to the ecological environment in the mining process, so it cannot be widely applied in the industrial field. Therefore, man-made diamond is the main industrial diamond used in the world.

As an advanced carbon material, artificial diamond not only has excellent mechanical properties such as super hard, wear resistance and corrosion resistance, but also has unparalleled thermal, optical, acoustic, electrical and chemical properties of other materials. It is a material of high efficiency, high precision, semi-permanent, energy saving and green environmental protection. It plays a great role in supporting other high-tech industries. Enjoy the reputation of "the king of materials".

With the continuous improvement of synthetic diamond technology, the single crystals with larger particles and higher quality are used in the field of consumption as cultivated diamonds for diamond inlaid jewelry or other fashion consumer goods. Both cultivated diamond and natural diamond are crystals formed by carbon elements, which have the same chemical and physical properties. Cultivated diamond can be comparable to natural diamond in the integrity of crystal structure, transparency, refractive index, dispersion and other aspects. Cultivating diamonds as a new force in the diamond industry provides a new option for diamond-loving consumers. With the continuous improvement of cultivated diamond synthesis technology, cultivated diamond has more and more prominent advantages in product quality, production cost and controllability of grade, size, color and customization, and has great development potential.

2. synthetic diamond method

Synthetic diamond is a kind of diamond crystal synthesized by scientific method through artificial simulation of natural diamond crystallization conditions and growth environment. The synthetic methods mainly include high temperature and high pressure method (HTHP) and chemical vapor deposition method (CVD).

The development of chemical vapor deposition (CVD) is not a replacement for high temperature and high pressure (HTHP), because they use completely different synthesis principles and techniques, produce different types of products and product characteristics, and the main industrial applications focus on different end areas. At present, the actual development of synthetic diamond industry in our country, the main method is high temperature and high pressure (HTHP). In the future in a long time, the method of high temperature and high pressure (HTHP) and chemical vapor deposition (CVD) will maintain common development trend, which is a basic feature of synthetic diamond industry.

The high temperature and high pressure method (HTHP) has been applied in industrialization since the 1950s. Its synthesis principle is that graphite powder transforms into diamond crystal under the condition of ultra-high temperature and high pressure and catalyzed by metal catalyst powder. The synthetic diamond synthesized by this method is mainly granular single crystal, which has fast synthesis speed, high single yield and good economy. Its industrial application is mainly to use the mechanical characteristics of diamond, such as super hard, wear resistance, corrosion resistance and so on to make grinding saw drill and other processing tools. In 1965, diamond six-sided jacking press independently developed in our country came out and rapidly popularized and used in China. With rapid improvement in the production efficiency and production capacity of synthetic diamond products, our country has become the largest country in the production of single diamond crystal. In recent years, the large-sized synthetic press, powder catalyst technology and high temperature and high pressure synthesis technology have further established the leading advantages in the synthesis of single diamond crystal under high temperature and high pressure. The major producers of single diamond crystal in the industry, such as Zhongnan Diamond, Huanghe Cyclone, Yu Diamond and Strength Diamond, all adopt the high temperature and high pressure method (HTHP). After more than half a century of development, the technology of high temperature and high pressure method has been relatively mature. With the upsizing of synthesis equipment and continuous improvement of synthesis technology, the single diamond crystal synthesized by this method has made great progress in particle size, crystal integrity, purity, strength and other aspects. However, due to the structural design of high-pressure equipment, the size of synthesized diamond single crystal is relatively small, which limits its wide application in functional materials to a certain extent. With the continuous progress of large-particle single crystal synthesis technology, there have been research achievements on the synthesis of single diamond crystal over 100 carats by high temperature and high pressure method in the world. It is expected to make some breakthroughs in the application of functional materials in the future.

Chemical vapor deposition (CVD) has been studied and applied in industrialization since the 1980s. Its synthesis principle is that the mixture of carbon gas (CH4) and hydrogen are excited to decompose active carbon atoms under ultra-high temperature and low pressure conditions. By controlling deposition growth conditions, active carbon atoms are deposited on the matrix to intergrow into diamond crystals. The diamond synthesized by this method is mainly flake diamond, and its industrial application is mainly to use diamond's performance advantages in light, electricity, magnetic, acoustic and thermal aspects as functional materials in emerging industries.

At present, the United States, Japan, Singapore and other countries have made more achievements in the research and industrial application of chemical vapor deposition (CVD) technology. Although China has introduced relevant industrial policies to support and encourage CVD technology, it is affected by the limited demand for downstream application, slow progress of technology research and development, and the monopoly of advanced technology by a few enterprises. Chemical vapor deposition (CVD) technology research and industrial application development speed is relatively slow, so far in China chemical vapor deposition (CVD) technology research and industrial application has made outstanding achievements in relatively few units.

Since chemical vapor deposition (CVD) can only grow on the substrate with crystal seeds, which belongs to two-dimensional growth and can only grow single layer, it is not suitable for the synthesis of small particle single crystals and cannot meet the demand for single diamond crystals in the industrial field, so it will not replace the high temperature and high pressure method (HTHP) in industrial application.

In the aspect of diamond synthesis cultivation, based on the existing technical conditions, the high temperature and high pressure (HTHP) method of diamond synthesis cultivation is mainly tower shape, fast growth rate, low cost, slightly poor purity, but the comprehensive benefit has advantages, especially in 1-5 CT cultivation diamond synthesis has obvious advantages. The synthetic and cultured diamonds by chemical vapor deposition (CVD) are plate shaped, the color is not easy to control, the cultivation cycle is long, the cost is high, but the purity is high, and it is suitable for the synthesis of diamonds cultivated above 5ct. Therefore, in the field of diamond single crystal synthesis, chemical vapor deposition (CVD) will not replace high temperature and high pressure (HTHP). In the field of cultivating diamond synthesis, the two focus on different types of products and do not constitute a substitute relationship.

3. Industrial application fields of artificial diamond

Artificial diamond has excellent performance in mechanics, heat, optics, acoustics, electricity and chemistry, and has a wide range of terminal applications, including industrial applications and fashion consumer applications.

(1) Industrial applications

The industrial application of artificial diamond mainly includes two aspects. First, it can make grinding, cutting, cutting and other kinds of diamond tools by using the mechanical properties of super hard, wear and corrosion resistance of artificial diamond, which can be used in the processing of metal and alloy materials, high hard and brittle materials (silicon, sapphire, magnetic materials, etc.), soft and tough materials (rubber, resin, etc.) and other difficult materials. Second, artificial diamond is used in electronic appliances, equipment manufacturing, aerospace, national defense, military industry, medical testing and treatment, as an important functional material, using its special properties in light, electricity, sound, magnetic, thermal and other aspects.

Diamond tools can be divided into sawing tools, grinding tools and drilling tools according to the way they are used. Sawing tools mainly include saw blade, saw blade, rope saw, line saw, tool, etc. Grinding tools refer to tools made with diamond as abrasives and made with binder or other auxiliary materials under certain production conditions with certain shape and performance, which can be used for grinding, grinding, polishing and other purposes. The product categories are mainly divided into three categories: consolidated grinding tools, coated grinding tools and paste liquid grinding tools. Specifically including grinding wheel, grinding head, cutting pieces, grinding disc, whetstone, emery cloth, sand belt, polishing film, grinding paste, grinding liquid, etc.; Drilling tools mainly include geological bit, oil (gas) well bit and engineering thin-wall bit, which are respectively used in geological exploration, oil (gas) exploration and mining and drilling of various buildings. The above diamond tools are widely used in stone, glass, ceramics, silicon wafers, hard metals, alloys, gems, agates, jade and other materials cutting, cutting, grinding, drilling, its terminal application has covered building materials stone, equipment manufacturing, automobile manufacturing, household appliances, electronic appliances, clean energy, exploration and mining and many other fields. With the development of science and technology, new applications of artificial diamond as functional materials emerge in an endless stream. As an extreme material with a wide range of uses, artificial diamond can not only process a variety of difficult-to-process materials, but also is developing towards functional components such as high sensitivity, high precision, high power, high light transmittance, high heat conduction, high electron migration, high human affinity, high wear resistance, corrosion resistance and radiation resistance. Diamond has special properties in optics, electricity, acoustics, heat and other aspects. As an important functional material, diamond has attracted increasing attention, and its properties and uses are constantly being researched and developed.

(2) Application in fashion consumption field

Large single crystals of gem-grade diamond with color, weight and purity reaching a certain standard in artificial diamond can be used as cultivated diamond inlaid ornaments in the field of consumption. Cultivated diamonds can be made into a variety of dazzling diamond ornaments through the process of design, cutting, grinding and processing. The chemical composition, color, clarity and other physical properties of cultivated diamond and natural diamond are the same except for the different growth environment, but the sales price of cultivated diamond jewelry is about 30% to 50% of the sales price of natural diamond jewelry of the same grade. In recent years, with the development of cultivated diamond synthesis technology and the improvement of consumer awareness of cultivated diamonds, cultivated diamonds are increasingly used in accessories, craft ornaments and art collections.