What are the raw materials of glass?
The glass raw materials are relatively complicated, and can be divided into main raw materials and auxiliary raw materials according to their functions. The main raw materials constitute the main body of the glass and determine the main physical and chemical properties of the glass. The auxiliary materials impart special properties to the glass and bring convenience to the production process.
The main raw material of glass
Silica sand or borax: The main component of silica sand or borax introduced into glass is silica or boron oxide, which can be separately melted into a glass body during combustion, which determines the main properties of the glass, correspondingly called silicate glass or borate glass. .
Soda ash or Glauber's salt: The main component of soda ash and thenardite introduced into glass is sodium oxide. They can form a fusible double salt with acid oxide such as silica sand during calcination, which acts as a flux and makes the glass easy to form. However, if the content is too much, the thermal expansion rate of the glass will increase and the tensile strength will decrease.
Limestone, dolomite, feldspar, etc.: The main component of limestone introduced into glass is calcium oxide, which enhances the chemical stability and mechanical strength of the glass, but the excessive content causes the glass to crystallize and reduce the heat resistance. As a raw material for introducing magnesium oxide, dolomite can increase the transparency of the glass, reduce thermal expansion, and improve water resistance. Feldspar is used as a raw material for the introduction of alumina, which controls the melting temperature and also improves durability. In addition, feldspar can also provide potassium oxide components to improve the thermal expansion properties of the glass.
Broken glass: Generally speaking, not all new materials are used in the manufacture of glass, but 15%-30% broken glass is blended.
Glass auxiliary material
Decolorizing agent: impurities in the raw material, such as iron oxide, will bring color to the glass. Commonly used soda ash, sodium carbonate, cobalt oxide, nickel oxide, etc. are used as decolorizing agents, which present a complementary color to the original color in the glass, so that the glass becomes colorless. In addition, there is a color reducing agent capable of forming a light color compound with colored impurities, such as sodium carbonate which can be oxidized with iron oxide to form ferric oxide, so that the glass changes from green to yellow.
Colorants: Certain metal oxides can be directly dissolved in a glass solution to color the glass. If the iron oxide makes the glass yellow or green, the manganese oxide can appear purple, the cobalt oxide can appear blue, the nickel oxide can appear brown, and the copper oxide and chromium oxide can appear green.
Clarifying agent: The clarifying agent can reduce the viscosity of the glass melt, so that the bubbles generated by the chemical reaction are easy to escape and clarify. Commonly used clarifying agents are chalk, sodium sulfate, sodium nitrate, ammonium salts, manganese dioxide and the like.
Opacifier: An opacifier can turn a glass into a milky white translucent body. Commonly used opacifiers are cryolite, sodium fluorosilicate, tin phosphide, and the like. They are capable of forming particles of 0.1 - 1.0 μm suspended in glass to make the glass opacified.
The raw materials of various glasses are slightly different
Ordinary glass (Na2SiO3, CaSiO3, SiO2 or Na22O·CaO·6SiO2)
Quartz glass (glass made of pure quartz as the main raw material, the composition is only SiO2)
Tempered glass (same composition as ordinary glass)
Potassium glass (K2O, CaO, SiO2)
Borate glass (SiO2, B2O3)
Colored glass (add some metal oxides in the ordinary glass manufacturing process. Cu2O - red; CuO - blue green; CdO - light yellow; CO2O3 - blue; Ni2O3 - dark green; MnO2 - purple; colloid Au - red; colloidal Ag - yellow)
Color-changing glass (advanced colored glass using an oxide of a rare earth element as a colorant)
Optical glass (add a small amount of light-sensitive substances such as AgCl, AgBr, etc. to ordinary borosilicate glass raw materials, and then add a very small amount of sensitizer such as CuO to make the glass more sensitive to light)
Rainbow glass (made of a large amount of fluoride, a small amount of sensitizer and bromide added to ordinary glass materials)
Protective glass (adds appropriate auxiliary materials during ordinary glass manufacturing process to protect people from strong light, strong heat or radiation. For example, gray - dichromate, iron oxide absorbs ultraviolet light and part of visible light Blue-green - nickel oxide, ferrous oxide absorb infrared and part of visible light; lead glass - lead oxide absorbs X-rays and r-rays; dark blue - dichromate, ferrous oxide, iron oxide absorbs ultraviolet light, infrared And most of the visible light; adding cadmium oxide and boron oxide to absorb the neutron flux.)
Glass-ceramic (also known as crystal glass or glass-ceramic) is made by adding crystal nucleus such as gold, silver or copper to ordinary glass, instead of stainless steel and gemstones, as radome and missile head.
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