Glass was originally formed by the solidification of acidic rock ejected from volcanoes. About 3700 BC, the ancient Egyptians had made glass ornaments and simple glassware, only colored glass at that time, about 1000 BC, China made colorless glass. In the 12th century, commercial glass appeared and began to be used as an industrial material. In the 18th century, optical glass was made to meet the needs of developing telescopes. The first plate glass was made in Belgium in 1873. In 1906, the United States produced a flat glass guide machine. Since then, with the industrialization and scale of glass production, various uses and various properties of glass have come out. Nowadays, glass has become an important material in daily life, production and science and technology.
Types of glass are usually divided into oxide glass and non-oxide glass according to the main components. There are few varieties and quantities of non-oxide glass, mainly chalcogenide glass and halide glass. The anions of chalcogenide glass are sulfur, selenium, tellurium, etc., which can cut off short wavelength light and pass yellow, red light, as well as near and far infrared light, with low resistance and switching and memory characteristics. Halide glass has low refractive index and low dispersion, so it is used as optical glass.
Oxide glass is divided into silicate glass, borate glass, phosphate glass and so on. Silicate glass refers to the basic composition of SiO 2 glass, its varieties, a wide range of uses. Usually according to the different content of SiO 2 and alkali metal and alkali earth metal oxide in the glass, it is divided into: (1) quartz glass. SiO 2 content is more than 99.5%, low thermal expansion coefficient, high temperature resistance, good chemical stability, uv and infrared light penetration, high melting temperature, high viscosity, difficult to form. It is widely used in semiconductor, electric light source, optical communication, laser and other technologies and optical instruments. ② High silica glass. The content of SiO 2 is about 96%, and its properties are similar to quartz glass. Sodium calcium glass. SiO 2 is the main content, also contains 15% Na 2 O and 16% CaO, its cost is low, easy to shape, suitable for large-scale production, its output accounts for 90% of practical glass. Can produce glass bottles, flat glass, utensils, bulbs and so on. Lead silicate glass. The main components are SiO 2 and PbO, with high refractive index and high volume resistance of ******, good wettability with metal, can be used to manufacture bulb, vacuum tube core column, crystal glassware, firestone optical glass and so on. Lead glass with large amounts of PbO blocks X-rays and gamma rays. ⑤ Aluminum silicate glass. With SiO 2 and Al 2 O 3 as the main components, the softening and deformation temperature is high, used for making discharge bulbs, high temperature glass thermometers, chemical combustion tubes and glass fibers. Borosilicate glass. With SiO 2 and B 2 O 3 as the main components, it has good heat resistance and chemical stability, and can be used to manufacture cooking utensils, laboratory instruments, metal-welded glass and so on. Borate glass with B 2 O 3 as the main component, low melting temperature, can resist sodium vapor corrosion. Borate glass containing rare earth elements is a new kind of optical glass with high refractive index and low dispersion. Phosphate glass with P 2o 5 as the main component, low refractive index and low dispersion, used in optical instruments.
In addition, the glass according to the performance characteristics is divided into: tempered glass, porous glass (namely foam glass, aperture, about 40, used for desalination, virus filtering, etc), conductive glass (used as electrode and aircraft windshield), microcrystalline glass, opacified glass (used for lighting devices and decoration items, etc.) and hollow glass (used for door and window glass), etc.
The main raw materials of glass production are glass forming body, glass adjuster and glass intermediate, and the rest are auxiliary raw materials. The main raw material leads into the glass forming network of oxides, intermediate oxides and oxides outside the network; Auxiliary raw materials include clarifier, flux, opacification agent, colorant, decoloring agent, oxidant and reducing agent, etc.
Glass production technology mainly includes: ① raw material pre-processing. The massive raw materials are crushed, the wet raw materials are dried, and the iron-containing raw materials are treated with iron removal to ensure the quality of glass. ② Preparation of compound. (3) melted. The glass material is heated at high temperature in the pool kiln or crucible kiln to form liquid glass with uniform, no bubbles and in line with the molding requirements. (4) shape. Process liquid glass into the required shape of the product, such as plate, various utensils, etc. ⑤ Heat treatment. Through annealing, quenching and other processes, eliminate or produce the stress inside the glass, phase separation or crystallization, and change the structural state of the glass.
Post time: Dec-06-2021