APPLICATIONS

　　1 Introduction

　　Starting with the synthesis of cubic boron nitride (CBN) by RH Wentorf of GE in the United States in 1957 using ultra-high pressure technology, CBN was also successfully synthesized in the former Soviet Union, Germany, Japan and the United Kingdom in the 1960s and early 1970s. Zhengzhou Institute of Abrasive Grinding synthesized the first CBN in China in 1966, which opened the prelude to China's CBN research and industrial production.

　　In addition to its hardness second only to diamond, CBN also has different electrical, optical, acoustic, thermal and chemical properties from diamond. It is these different properties that lay the technical foundation for its development of new application fields. . Unlike abrasive-grade CBN, nano-CBN, wBN and CBN film not only have common basic characteristics, but also have their own individuality, which makes it possible for CBN to open up newer and broader application fields. It can be seen that the research on the preparation technology and application technology of CBN materials is promising.

　　From the perspective of the development of the world CBN market, the demand for CBN is growing at a rate of more than 18% every year. At present, the world's annual output of CBN is about 500 million carats, of which China accounts for half of the total. It has strong competitiveness not only in quantity but also in quality. It is gratifying that my country's CBN products have been recognized by major foreign manufacturers and well-known CBN tool manufacturers, and their performance has reached international standards, forming a batch export.

　　2. Cubic boron nitride research and development process and its significance

　　In the study of boron nitride, it was found that its structure is very similar to graphite, and natural diamond exists as a dense phase of carbon, and the soft carbon is successfully transformed into the hardest diamond by artificial methods. Is it possible to convert boron nitride into a dense phase like graphite into diamond - sphalerite boron nitride, cubic boron nitride or other dense boron nitride? In 1952, Pease was studying boron nitride It was pointed out at the time that the structure of boron nitride is similar to that of graphite, but slightly different. In a hexagonal phase structure of boron nitride, when the hexagonal grid is arranged into a crystal, every other layer produces half a hexagonal network displacement, which is actually more conducive to the zinc blende boron nitride-cubic boron nitride Formation. In 1953, Gardini summarized the literature on boron nitride and tried to prepare cubic boron nitride, but failed.

　　In the mid-1950s, due to the development of high-pressure science, the basic conditions for the synthesis of materials under extreme high-temperature and high-pressure conditions - high-temperature and high-pressure devices have become mature. In 1955, Hall of the artificial diamond research group of GE Corporation of the United States successfully synthesized artificial diamond for the first time with an improved high-temperature and high-pressure device, creating a new field of synthesizing new materials under high temperature and high pressure. The synthesis of artificial diamond has played a huge role in promoting the advent of high-pressure dense phase boron nitride.

　　Due to the influence of the similar structure of non-dense phase boron nitride and graphite, at the beginning, it was always attempted to synthesize cubic boron nitride using catalysts such as nickel, iron, cobalt, etc. for synthetic diamonds, but none of them succeeded. Until 1957, Wentorf used metal magnesium as a catalyst to easily synthesize boron nitride (CBN) with a cubic structure and named it Borazon. In 1963, Bundy and Wentorf studied the direct conversion of hexagonal boron nitride (hBN) to cubic boron nitride, and pointed out that the direct conversion pressure was 115×105kPa at 2000K without the participation of a catalyst. Cubic boron nitride dominates in the high temperature region, and another dense phase of boron nitride—wurtzite boron nitride (wBN) can be formed in the low temperature region. In 1972, Devries and Fleicher studied the equilibrium problem of the Li-BN system, which laid the experimental foundation for the phase diagram of boron nitride.

　　At the same time as the synthesis of cubic boron nitride by the static high-pressure method, the research on the synthesis of wurtzite-type boron nitride and cubic boron nitride by the dynamic high-pressure method was also carried out and turned into commercial production. Since Sawaoka et al. transformed hexagonal boron nitride into wurtzite-type boron nitride by explosive method in 1974, not only wBN but also CBN can be synthesized by dynamic high-pressure method, and the conversion rate has reached 90%.

　　The research on the growth of cubic boron nitride film is an important branch of the development of cubic boron nitride. In 1978, after Tadamasa reported the "polycrystalline CBN film", in the 1980s, various methods for preparing CBN films such as plasma, molecular flow, double electron beam, and high-frequency discharge appeared soon [1~3].

　　Cubic boron nitride (CBN for short) is an inorganic crystal material that does not exist in nature and can only be synthesized artificially. Cubic boron nitride crystal has a high hardness second only to diamond, and is a typical superhard material that has been widely used in the field of machining. Moreover, CBN crystal is a typical III-V compound, its resistivity is 1010Ω.cm, thermal conductivity is 13W/(cm.K), it can withstand high temperature of 1200℃, and it has the widest direct bandgap of 6.4eV, which is Very excellent thermal conductivity, optoelectronic and semiconductor materials [1], have broad application prospects in the field of high temperature and high power broadband device microelectronics. Cubic boron nitride sphalerite structure, macroscopic symmetry belongs to the F43m-Td group, can also produce second-order linear optical effects, can be used as high-order harmonic generators of light, electro-optic modulators, visible-ultraviolet light converters, Optical rectifiers, optical parametric amplifiers, etc. Cubic boron nitride has the same strong anti-radiation ability as diamond, and can be used to prepare anti-radiation devices. Therefore, the preparation and performance research of cubic boron nitride materials have important practical significance for breakthroughs in various fields of the national economy, especially in the application of devices under severe environmental conditions such as aerospace and war.

　　3. Current status of foreign cubic boron nitride products

　　Foreign CBN abrasives were developed earlier, with complete varieties and high quality, among which GE Company in the United States and De Beers Company in the United Kingdom are the most representative. GE Company [4] CBNI type, CBN400, CBN500, CBN510, CBN550, TYPEI are very representative abrasives. CBNI type is widely used in vitrified bonded abrasive tools. Its particle shape is irregular block, with good dressing performance and long service life of grinding wheel; CBN400 type has high strength, smooth crystal surface and sharp and wear-resistant cutting edge. Micro-controllable cleavage on the longer high-strength fracture surface helps the abrasive maintain a sharp cutting edge for a long time; CBN500 type is high-strength single crystal, widely used in heavy-duty grinding; CBN510 type It is a strong block abrasive with titanium coating on the surface; CBN550 is a microcrystalline abrasive.

　　Yokogawa.M et al [5] found that when studying single crystal CBN abrasive (CBNI) and microcrystalline CBN abrasive (CBN550), the strength of microcrystalline CBN550 is higher than that of single crystal, and the cutting edge should not be damaged in a large area. Microcrystalline CBN grinding wheel The grinding performance of single crystal is 2~3 times better than that of single crystal. TYPEI is its latest product, known as the universal abrasive. De Beers' ABN200, ABN615, and ABN800 are its main products. ABN615 is a titanium-plated abrasive grain specially developed for vitrified bonded abrasive tools. It has high thermal stability and can be made into a high concentration of 272%, which opens up a new application path for CBN grinding iron group materials. Bailey MW and others believe that [6], ABN800 abrasive has high compressive strength and thermal stability, it is easy to cleavage during grinding, and maintains a sharp polygonal cutting edge after breaking, so it has excellent grinding performance, and Its strength can still be well maintained under high temperature of 1100 ℃. Due to its high thermal stability, it still has excellent grinding performance under harsh conditions.

　　4. Current status of domestic CBN products

　　In the 20 years since China successfully synthesized CBN in 1966, the progress of synthesis technology has been very slow. The real reason is that the industrial demand is not as urgent as that of diamond. The reform and opening up in the late 1980s and early 1990s, and the acceleration of the development of industries such as automobiles, aerospace, mechatronics, and microelectronics, have brought great impetus to the research and industrialization of CBN.

　　In the late 1990s, the systematic research and development of CBN catalysts began in China. Catalyst series with different characteristics can be synthesized into CBN products with different characteristics. After mastering some of the core technologies, they have successively developed products suitable for the synthesis of light yellow, yellow, orange, and brown. Catalyst system with black CBN crystal. At the same time, through the research of various additives, the toughness of CBN can be adjusted, and a series of CBN products ranging from brittle, medium toughness to high toughness have been formed. Many products are at a similar level to foreign products (see Table 1). The commonly used CBN varieties and particle sizes in the world can be supplied in batches, and we can supply batches of products that cannot be normally supplied abroad. Many varieties are available with a particle size of 30/40, such as CBN120, CBN210, CBN230, CBN280, etc. [7].

　　Table 1 Typical domestic CBN products and their descriptions[8]

　　In recent years, the rapid development of CBN synthesis technology in my country, the continuous expansion of CBN product varieties, and the continuous reduction of production costs have promoted the industrialization process of CBN products and increased the popularity and share of Chinese products in the international market. Now all the raw materials and equipment we use have been localized, the synthesis technology has its own system, and the industrial chain has been completed. It can be said that we have not only become a big CBN production country, but also a strong CBN production country.

　　Why after entering the new century, my country's CBN single crystal products have developed rapidly, which is mainly due to the successful development of a series of catalysts for different CBN products, thanks to the large-scale ultra-high pressure and high temperature presses and their control technology The increase is due to the need to double the output of automobiles, engines, bearings, refrigerator compressors and air-conditioning compressors, coupled with the rapid transfer of the world's manufacturing center to China, the international market space for such products will also become larger and larger. This will directly lead to an increasing market space for grinding tool products [9].

　　5. Comparison of CBN products at home and abroad

　　To sum up, domestic and foreign CBN products have their own characteristics, so what about the quality of domestic products? I am afraid this is what everyone wants to know. Here the author quotes two sets of data to illustrate (see Table 2. Normal temperature performance of domestic and foreign CBN abrasives Compare).

　　Table 2 Comparison of normal temperature performance of CBN abrasives at home and abroad

　　The high temperature oxidation resistance of CBN abrasives is one of the important properties of abrasives. Figure 1 shows the results of differential thermal analysis of the oxidation temperature of the above eight CBN abrasives [10].

　　Fig.1 Analysis results of oxidation temperature of 8 kinds of CBN abrasives by differential thermal method

　　From the above comparative data, it can be seen that the domestic 4# CBN abrasive has the best oxidation resistance, and the 3# CBN abrasive has the same oxidation resistance as ABN800. Among the domestic CBN abrasives, except for the 5# abrasive, they can withstand high temperatures above 1000 °C. It shows that the normal temperature and high temperature properties of domestic CBN abrasives have reached the high level of foreign CBN products.

　　The stability of domestic products has been significantly improved, and has been recognized by users at home and abroad. The comparison of impact strength of CBN products at home and abroad is shown in Table 3.

　　Table 3 Comparison of CBN impact strength (TI/TTI) at home and abroad

　　Domestic and foreign CBN tool manufacturers basically use domestic CBN products. The products have been recognized by domestic and foreign customers, and their performance has reached international standards. They have been exported in batches for a long time. The long-term application practice of domestic and foreign tool manufacturers has proved that the quality of CBN products in my country is stable and reliable, and can fully meet the needs of use.

　　6. Conclusion

　　(1) In addition to its hardness second only to diamond, CBN also has different electrical, optical, acoustic, thermal and chemical properties from diamond. It is these different properties that lay the foundation for its development of new application fields. technical basis. Unlike abrasive-grade CBN, nano-CBN, wBN and CBN film not only have common characteristics, but also have their own individuality, which makes it possible for CBN to open up newer and wider applications. It can be seen that the research and development of CBN material preparation and application technology is promising.

　　(2) The cultivation technology of CBN large single crystal, the technology of cultivating functional CBN crystal by CVD method and its research on electricity, light and heat are all behind the international counterparts, as well as the development of cutting-edge technologies such as nano-CBN and its products It is directly related to the development potential of the industry with applied research.

　　(3) After decades of development, CBN has only been effective in the application of engineering materials and has become the mainstream of today's development, but its application as functional materials has potential prospects, waiting for people to explore, develop, and go. application.

　　When we talk about CBN in the future, we should not only pay attention to the current mainstream of CBN as engineering materials, but also increase the development of CBN as a functional material and its application technology. Only in this way can CBN materials and their applications be comprehensively developed. develop.

　　references

　　[1] Zhang Xiangfa, Zhang Kui, Wang Guangzu, Diversity of cubic boron nitride synthesis methods [C] Proceedings of the Cross-Strait Superhard Materials Technology Development Forum, 2010, 10: 79~83

　　[2] Edited by Zhang Tiechen and Zou Guangtian, Cubic Boron Nitride [M] Jilin University Press, 1993

　　[3] Wang Guangzu, Li Gang, Zhang Phase Method, Synthesis and Application of Cubic Boron Nitride [M] Henan Science and Technology Press, 1995

　　[4] Li Zhihong, Research on Vitrified Bond CBN Abrasives [D] Tianjin, Tianjin University, 1996

　　[5] Yokogawa M，Yokogawa K，Grinding properties of monocrystalline and microcrystalline CBN grinding wheels，IntJ.Japan Soc.Prec.Eng.，1992，26(1)：20~26

　　[6] Baailey MW, Juchem HO, Characterization of ABN800, IDR, 1996, 56(568): 6~9

　　[7] Zhang Kui, Zhang Xiangfa, Wang Guangzu, the present and future of cubic boron nitride [J] Industrial Diamond, 2010, 1/2: 9~13

　　[8] Zhang Xiangfa, Zhang Kui, etc. New progress in ultra-high pressure synthesis of CBN [C] Proceedings of the Fifth Zhengzhou International Symposium on Superhard Materials and Products, 2008, 9: 27~33

　　[9] Li Zhihong, Zhao Bo, etc., impressive achievements and brilliant future [C] Proceedings of the Fifth Zhengzhou International Symposium on Superhard Materials and Products, 2008, 9: 1~16

　　[10] Liu Minling, Lu Tao, etc. Performance comparison of commonly used ceramic CBN abrasives at home and abroad [C] Proceedings of the Fourth China Conference on Diamond Related Materials and Applications, 2010, 8: 14~23