High-purity quartz sand generally refers to quartz powder with SiO2 content higher than 99.99%. It is the main raw material for quartz glass and quartz crucible. Its high-grade products are widely used in large-scale and ultra-large scale integrated circuits, optical fibers, solar cells, lasers, In the aerospace, military and other industries.
High-purity quartz sand has an important strategic position, and its high-end product preparation technology is monopolized by the United States, Germany and other countries, and limits technology and exports. At present, the purification and large-scale exploitation of quartz sand in China is still in a difficult exploration stage.
First, the main technical indicators of high-purity quartz sand
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: the content of silica 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. Impurity
See Table 1, and the particle size distribution requirements are shown in Table 2.
Second, the development of high-purity quartz sand at home and abroad
foreign
Initially high purity quartz sand is formed by a secondary crystal processing, with the gradual depletion of a secondary crystal resources. Since the 1970s, developed countries have begun to explore the use of ordinary quartz instead of crystal to prepare quartz sand.
United States
In the 1980s, American PPCC Company purified quartz in granite in the Foxdale area on the northwest coast of the United Kingdom. The content of SiO2 was 99.99%, the impurity content of Fe was less than 1×10-6, and the content of other transition elements was less than 5×10-6. Quartz glass raw material.
Japan
Since the 1990s, transparent high-purity quartz has been separated from fine-grained pegmatite.
Germany and Russia
Look for high-purity quartz in vein quartz and metamorphic quartzite .
domestic
China has made some 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 been fully overcome.
China is one of the countries with the most abundant quartz reserves. However, due to the backward processing methods and the lack of basic research in 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.
The production of high-purity quartz sand in China began in the late 1990s, and the raw materials used were mainly crystal. At present, most of the medium and low-grade high-purity quartz sand used in quartz glass in China is still 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. As far as the purity of crystal minerals is concerned, a large amount of industrial production is difficult to ensure the uniformity of the crystal structure of the minerals and the consistency of the inherent chemical quality.
In recent years, China has attached great importance to the research and development of quartz purification technology, especially the development and utilization of ordinary quartz. The production and quality of high-purity quartz sand in China have been greatly improved, and the quality can basically meet the requirements of medium and low-grade quartz products.
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