In recent years, China's defense industry has undergone earth-shaking changes, rapid development in technology and technology, and has also been freed from financial constraints. Not only that, but also achieved remarkable achievements - China has established a defense industry system that can independently develop high-tech weapons platforms, and has basically achieved self-sufficiency. Among them, advanced stealth fighters (歼-20, 歼-31), aircraft carriers (002 domestic aircraft carriers under construction, third, fourth...), stealth drones (Pterosaur-2, etc.) and new Cutting-edge weapons such as a generation of intercontinental ballistic missiles (Dongfeng-41 intercontinental ballistic missiles) have attracted the attention of many countries in the world. In this regard, Australia's "East Asia Forum" website said that the development of China's defense industry is unstoppable.
Wing Loong ⅡUAV picture
Recently, the R&D team of the School of Materials Science and Engineering of Shanghai Jiaotong University used its first ultra-high-purity aluminum purification process and equipment with complete independent intellectual property rights in China, and combined with new technology to purify high-purity alumina and new rare earth materials. The preparation technology is perfectly integrated to produce 5N (purity greater than 99.999%) high purity alumina products. Moreover, at present, the self-developed pilot project for rare earth modified high purity sapphire raw materials has been officially put into production. The project also has a very important significance, which is to make up for the gap in the international rare earth high-purity aluminum preparation technology.
Seeing this, you may remember: high purity alumina is the main raw material for artificial sapphire. Then you know that a large number of sapphire materials are used in the optoelectronic devices on the UAVs, high-speed fighters and supersonic missiles in China's cutting-edge weapons. Of course, sapphire materials are also widely used in other military optoelectronic devices.
China 002 type aircraft carrier picture
Why is sapphire single crystal applied to the defense industry in large quantities? This is because, as an excellent wave-transparent material, sapphire single crystal has high transmittance and good wave-transmission rate in microwave, visible, ultraviolet and infrared bands, and can satisfy multi-mode composite guidance (infrared imaging, radar). Etc.) requirements. In addition, sapphire single crystal has excellent mechanical properties and chemical stability, high temperature resistance, high strength, high hardness, wear resistance, corrosion resistance, and can meet the demanding requirements of supersonic missiles for wave-transparent materials. An excellent choice for medium-wavelength infrared window materials such as advanced missiles and high-speed fighters.
DF 41 picture
So, how did the sapphire single crystal with such an important application grow? Currently, artificial sapphire crystals are mainly grown in sapphire single crystal furnaces. The growth methods mainly include a guided mode method, a bubble generation method, a heat exchange method, a helium moving method, and a temperature gradient method. However, no matter which method is used, it is inseparable from the equipment! The important performance parameters of sapphire crystals - melting point is 2050 ° C, boiling point is 3500 ° C, the maximum working temperature can reach 1900 ° C - indicating that the equipment for manufacturing sapphire single crystal must meet certain requirements, that is, The material for preparing the sapphire single crystal furnace presents high requirements. The refractory metal tungsten-molybdenum material has become a key material for the preparation of sapphire single crystal furnace because of its high melting point and low saturated vapor pressure at high temperature.
tungsten crucible picture
Moreover, tungsten-molybdenum material plays an extremely important role as a main component of the sapphire single crystal furnace temperature field material. Then, what are the sapphire single crystal furnace temperature field materials? Tungsten-rhenium, molybdenum-niobium, tungsten heat shield, birdcage type tungsten rod heating element, molybdenum heat shield and so on. Among them, most of the niobium used is tungsten tantalum and molybdenum tantalum produced by the powder metallurgy press sintering method, and a small number of thin wall niobs produced by the spinning method.
Finally, it must be considered that both tungsten and molybdenum are rare strategic metals. Although China's tungsten reserves rank first in the world and there are many molybdenum reserves, the rational utilization of resources cannot be ignored. Moreover, as a long crystal enterprise, the cost of long crystals will inevitably be considered. After all, the cost of the temperature field material accounts for more than one third of the total crystal growth cost. So in any case, the author believes that China's long crystal enterprises should also continue to study new production processes and technologies, improve the yield of tungsten and molybdenum metals, extend the life of tungsten and molybdenum materials and reduce manufacturing costs. Of course, the ultimate goal of all of this is to let our national defense military stand in the forefront of the world. Therefore, tungsten and molybdenum are really well-deserved strategic metals.
