High-purity quartz sand generally refers to quartz powder with a SiO2 content higher than 99.99%, and is a main raw material for quartz glass and quartz crucible. Its high-end products are widely used in large-scale and ultra-large-scale integrated circuits, optical fiber, solar cells, laser, aerospace, military and other industries.
Since these industries are related to the long-term development of the country and are a necessary condition for the sustainable development of high-tech in the country, the strategic position of high-purity quartz sand is very important. The preparation technology of high-end products is monopolized by the United States, Germany and other countries, and the technology is limited. And export.
At present, the purification and large-scale exploitation of quartz sand in China is still in a difficult exploration stage. High-purity quartz sand has unique physical and chemical properties, especially its intrinsic crystal structure, crystal shape and lattice change law, which makes it have high temperature resistance, small thermal expansion coefficient, high insulation, corrosion resistance, piezoelectric effect, resonance effect and Unique optical properties.
The quality requirements for quartz sand products are generally directly related to their actual industrial use. If it is used in fine materials and high-performance materials such as electronic materials and quartz crucibles, the quality of raw materials is strict, and high-purity and ultra-pure quartz sand are required, and the total content of impurities is low. Specifically, the quality requirements of quartz sand are mainly reflected in the chemical composition and particle size composition: 1 appearance is white, no visible mechanical impurities; 2 purity requirements: silica content is greater than 99.99%; 3 according to the requirements of different industries, It can be processed into series products of different specifications and models to meet user requirements.
Application of high purity quartz sand
High-purity quartz sand is also the main raw material for quartz glass. Quartz glass is known as "glass net" because it has a series of excellent physical and chemical properties, such as temperature resistance up to 1100 ~ 1200 ℃, 800 ℃ higher than ordinary glass; is a transparent refractory material; thermal expansion coefficient is small, only It is 5.5X10 -7/℃, which is equivalent to 1/20 of ordinary glass. It can theoretically reach zero expansion. It has excellent light transmission performance, and ultraviolet light, visible light, infrared light, etc. can pass well. It has good electricity. Insulation, 2018 ℃ resistivity is 1018 Ω / cm, insulation strength is 250kV / cm, vacuum degree can reach 10-6Pa; chemical stability is good, in addition to hydrofluoric acid, insoluble in any other acid. Quartz glass is a brittle material with good compressive strength, but the tensile strength is smaller. Quartz glass is not resistant to hydrofluoric acid. Under high temperature conditions (above 1000 ℃), it will be converted into cristobalite, which is its two shortcomings.
The main products of quartz glass include high-purity high-temperature resistant quartz glass tubes for large-scale integrated circuits, arc-based quartz crucibles (solar and semiconductor grades), quartz glass for optical communication, and quartz glass for electric light sources. The variety and use of quartz glass are closely related, and users can manufacture different quartz glass according to the characteristics and requirements of quartz glass.
China has made progress in researching ordinary quartz raw materials for quartz glass since the late 1980s. The products studied can reach the level of second, third and fourth grade crystals, but only suitable for medium and low grade quartz glass, high purity and low. The technical difficulties of hydroxy quartz raw materials have not yet been fully overcome. The purity of industrially produced quartz glass raw materials cannot meet the requirements of high-purity quartz sand glass raw materials. The high-quality quartz glass raw materials are mainly imported, which restricts the development of China's quartz sand glass industry, which has caused domestic quartz glass and raw material production enterprises and Concerns from relevant research institutes.
Development status of domestic high-purity quartz sand
China is one of the countries with the most abundant quartz reserves. Currently, there are relatively good areas for mining and utilization of quartz mines, such as Jiangsu Donghai, Anhui Fengyang, Hubei Hong'an, Jiangxi Xiushui, Inner Mongolia Wuhai, etc. The reserves of quartz ore in these areas are large and grade. High and easy to mine, but due to the backward processing and utilization technology of domestic quartz sand, most of the quartz mines mined are only used as low-end quartz products with low economic value, such as silicon micropowder, glass, refractory, ferrosilicon, silicon carbide, Fused silica, etc.
In fact, there are many mineral resources that can be used to produce high-purity quartz sand in China. However, due to the backward processing methods and the lack of basic research in the earth sciences such as mineralogy and geological genesis related to quartz glass raw materials, the products cannot meet the requirements of high-purity quartz raw materials. . At present, most of the medium and low-grade high-purity quartz sand used in quartz glass in China is made from crystal. The reserves of crystal in China are limited, the price is expensive, the texture is uneven, some mineral impurities and the mixed substances in the process cannot be removed, resulting in the small batch size and unstable quality of the ultra-pure quartz sand produced by the crystal.
Development trend of high purity quartz sand
With the depletion of high-quality crystal resources, the problem of solving the problem of insufficient self-sufficiency of high-grade quartz sand in China is mainly concentrated on the improvement of professional techniques such as geological prospecting, process mineralogy and mineral processing. Firstly, we should look for ores with relatively pure crystals, homogeneous phase replacement and less gas-liquid inclusions. Secondly, we use modern advanced physical and chemical beneficiation technology and equipment to develop high-efficiency and stable high-purity quartz ore dressing purification technology. High-purity quartz raw sand has become a strategic product of the national economy.
Efforts to seek the advancement of China's high-purity quartz sand ore purification technology and industrial development, to achieve high-grade (high-purity and ultra-high purity) quartz sand self-sufficiency is urgently needed for the development of China's quartz glass industry, for China's relevant high-tech industries Development is important.
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