Types, uses, and process methods of quartz glass


There are two types of quartz glass: transparent and opaque. Transparent and opaque quartz glass are the most economically valuable materials used in industry and scientific research. The raw materials used in its manufacture (by smelting method) are crystal or high-purity, ultra high-purity quartz sand (transparent quartz glass) and white quartz sand (opaque quartz glass). Both of these raw materials exist in nature and are composed of the purest SiO2.

 

Quartz glass and crystal have the same chemical composition, but differ greatly in structure. One is in a glass state, and the other is in a crystalline state. Crystals cannot withstand high temperature thermal shock. When it encounters high temperature, it will break and transform into other crystals. Quartz glass can withstand extremely high temperature shock. The production of transparent and opaque quartz glass requires high temperatures, as crystalline SiO2 can only melt at temperatures above 1713 ℃.

 

Overview of quartz glass

Quartz glass has a history of over 160 years abroad. In 1839, the French first melted quartz using a hydrogen oxygen combustion flame to produce quartz glass. In 1902, the British used graphite rods to obtain high temperature (known as single rod electric furnaces) to produce quartz glass. In the 1940s, electric melting furnaces were invented. In the 1950s, with the development of semiconductor technology and new electric light sources (in urgent need of a large amount of quartz glass), quartz glass quickly developed. Because the production technology of quartz glass is difficult, until now, only a few countries such as the United States, Germany, France, Japan, the United Kingdom, and China are able to produce quartz glass in large quantities. The research on quartz glass in China began in 1957 and was blank before the establishment of the People's Republic of China. In 1956, the country formulated a 12 year science and technology development plan, which required the development of 57 key research tasks urgently needed for national defense, the solution of new high-performance materials for two bombs and one satellite, and the material preparation for the research of atomic bombs, missiles, and artificial satellites. Quartz glass is the designated research content in the 26th and 40th task books, and the task was assigned to the National Institute of Building Materials at that time. The development of quartz glass in China can be roughly divided into five stages: from 1957 to 1961, it was the pioneering stage, mainly focused on researching process manufacturing methods; From 1962 to 1966, it was the stage of industrial formation, during which many military tasks were completed, and the production and quality of civilian products also greatly improved, forming an initial industry; During the period of reform and innovation from 1978 to 1988, quartz glass for high-tech applications, such as high-purity high-temperature resistant quartz glass tubes for large-scale integrated circuits, high-purity coated crucibles, arc method crucibles, quartz glass for optical communication and credit, and quartz glass for lasers, were studied and produced in large quantities during this period; From 1989 to 2000, it was a period of significant development, including the introduction of advanced foreign technology, technological innovation, and the increase in variety and production. The most prominent was the development of Donghai County into a quartz glass production base for electric light sources, with an annual output of 6000 tons of quartz glass (including over 2000 tons of high-quality products), greatly improving quality, reducing costs several times, and significantly improving technical equipment.

 

Over the past 40 years, the development speed of quartz glass has been relatively fast. Taking the production of transparent quartz glass tubes as an example, in 1975, the output was 172 tons. 31 factories needed to use more than 60 resistance furnaces to produce the tubes, which were of poor quality (equivalent to current waste tubes). Now, two continuous melting furnaces can produce nearly 200 tons per year. By 2000, the annual output of transparent quartz glass tubes reached 7000 tons (including 3500 tons of high-quality products), an increase of nearly 40 times in 25 years.

 

Performance of quartz glass

Quartz glass is known as the "glass king" because it has a series of special physical and chemical properties.

 

Chemical composition of quartz glass

The chemical composition of quartz glass is a single component of SiO2, commonly referred to as purity.

 

Illuminated quartz glass

Quartz glass for semiconductor industry

Thermal properties of quartz glass

Temperature resistance

thermal stability

Volatility of quartz glass at high temperatures

Specific heat and thermal conductivity

Crystallization performance (also known as crystallization performance or devitrification performance) of quartz glass

High temperature discoloration of quartz glass

The performance of quartz glass mentioned above is transparent quartz glass, while other types of quartz glass (milky white quartz glass, quartz ceramic, opaque quartz glass, quartz cotton, quartz fiber, etc.) have their own special properties.

 

The main varieties and uses of quartz glass

The variety and use of quartz glass are closely related. Users require the production of the quartz glass they need based on the characteristics of quartz glass, resulting in the variety of quartz glass. The new variety has improved the performance and quality of quartz glass, promoting the development of the quartz glass industry. Almost all industries use quartz glass, but due to the complex process of quartz glass products and the high cost of raw materials, the price of quartz glass is also high, which limits its widespread use. Here is a brief introduction to the main varieties and uses of quartz glass.

 

Quartz glass for discharge tubes

Transparent quartz glass, due to its excellent light transmittance and heat resistance from the ultraviolet to infrared region, is widely used in electric light sources such as mercury lamps, ultra-high pressure mercury lamps, xenon lamps, ultraviolet lamps, iodine tungsten lamps, halogen lamps, gas laser lamps, metal halide lamps, etc. It is the largest user of quartz glass in China and the second largest user in foreign countries (the first largest user is semiconductor technology), with the primary task being to improve quality, Strive for more exports.

 

Quartz glass for semiconductor industry (electronic industry)

Quartz glass for infrared heaters

Using opaque quartz glass (milky white quartz glass) to manufacture infrared heaters, heaters, crystal heaters, etc., consumes nearly a thousand tons of milky white quartz glass tubes annually. Mainly used for heating electroplating solutions, acid heating, household heating, tempered glass heating, industrial paint baking (bicycles, cars, etc.), and food, paper, textile industries.

 

Various acid resistant containers of quartz glass

Due to its superior acid and heat resistance, it has been widely used in the chemical industry. For example, a synthetic hydrochloric acid device; Combustion, cooling, and guiding devices for high-temperature acidic gases; Evaporation, cooling, absorption, and storage devices for acidic solutions, as well as manufacturing devices for distilled water, hydrochloric acid, sulfuric acid, and nitric acid; Chlorination reaction vessel; Distillation tower filling, steam heating and stirring device; Acid resistant valve; Filter plates, etc.

 

Quartz glass for electrical insulation

Quartz glass, due to its excellent electrical insulation and heat resistance, is used as insulation material for Kochuer electrostatic integrators, high-frequency and various electrical meters, as well as for boiler liquid level pipes in power plants and high-voltage insulation pipes.

 

Various quartz glass containers for firing

Due to its pollution-free nature, quartz glass can be used as a firing container for fluorescent materials and various cups and plates.

 

Protective tube type quartz glass

Quartz glass is widely used as a protective tube for general thermometers; In addition, it can also be used as an indispensable material for temperature measurement of immersion pyrometer protection tubes and steel making.

 

Quartz glass for metallurgical industry

Due to its excellent heat resistance, quartz glass can be used as a tube type sample for oxygen, carbon, and other analysis in open hearth and blast furnaces; Quartz glass for steel making, continuous injection, and rolling outlet; Quartz glass for smelting precious metals, gold, and platinum; Quartz glass is used for non-ferrous metal smelting (aluminum and alloys, melting metal evaporation tanks), etc.

 

Furnace core tube type quartz glass

Due to its excellent electrical properties, heat resistance and air tightness, quartz glass can be used as the core tube and outer tube of electric furnace, gas furnace, high-frequency furnace, etc., as well as air, various gases and Vacuum furnace.

 

Quartz glass for various physical and chemical instruments

Due to its many excellent characteristics, quartz glass can be used as components for dilatometers, thermal balances, electrical measuring instruments, spring balances, seismometers, etc., analytical tools for flasks, beakers, evaporating vessels, crucibles, boats, sulfur quantification devices, condensers, etc., and various physical and chemical experimental equipment for spectrophotometers, such as absorption capacity running sleeves.

 

Optical quartz glass

Because quartz glass has high ultraviolet transmittance, heat resistance and low expansion, it can be used as window glass for schlieren photography, heat resistant lens and window glass, reflector and prism for reflecting telescope, window glass for gas laser, optical standard, etc. In addition, because quartz glass does not contain any components other than SiO2, it can be used as a crucible and tube for melting optical glass.

 

Quartz glass for optical communication and high-tech

80% of the world's information business is transmitted through optical fiber, and the development of the optical fiber industry is more strategic. The development of optical fiber cannot be separated from quartz glass, because optical fiber is quartz glass fiber, and the production of quartz glass fiber requires quartz glass preforms and quartz glass sheathed tubes. Due to the particularly high purity requirements of such quartz glass, German company Hercules produces a specialized product Heralux WG grade quartz glass tube, which reaches 3500 RMB per kilogram. China produces a large number of optical fibers using imported pipes from foreign countries. In addition, quartz glass is required in high-tech fields such as bioengineering, optical communication technology, atomic energy technology, laser technology, aerospace technology, and space technology technology. Quartz glass is like the monosodium glutamate used in cooking. Although it is not widely used, it is indispensable in various industries. Quartz glass is an important new material with significant social and economic benefits.

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