The glass was originally solidified by acidic rocks ejected from volcanoes. About 3700 BC, the ancient Egyptians had made glass ornaments and simple glassware. At that time, there was only colored glass. About 1000 BC, colorless glass was made. In the 12th century AD, commercial glass appeared and began to become an industrial material. In the 18th century, in order to meet the needs of developing telescopes, optical glass was produced. In 1873, Belgium produced flat glass first. In 1906, the United States produced flat glass leading to the machine. Since then, with the industrialization and large-scale production of glass, glass of various uses and various properties has come out one after another. In modern times, glass has become an important material in daily life, production, and science and technology.
Type of glass is usually divided into oxide glass and non-oxide glass according to the main components. There are few types and quantities of non-oxide glass, mainly chalcogenide glass and halide glass. The anions of chalcogenide glass are mostly sulfur, selenium, tellurium, etc., which can cut off short-wavelength light and pass yellow, red light, and near and far infrared light. It has low resistance and has switching and memory properties. Halide glass has low refractive index and low dispersion, and is mostly used as optical glass.
Oxide glass is divided into silicate glass, borate glass, phosphate glass and so on. Silicate glass refers to the glass whose basic component is SiO 2, which has many varieties and wide applications. Usually according to the different content of SiO 2 and alkali metal and alkaline earth metal oxides in the glass, it is divided into: ① Quartz glass. SiO 2 content is greater than 99.5%, low thermal expansion coefficient, high temperature resistance, good chemical stability, ultraviolet light and infrared light transmission, high melting temperature, high viscosity, and difficult molding. It is mostly used in semiconductors, electric light sources, optical communication, lasers and other technologies and optical instruments. ②High silica glass. The content of SiO 2 is about 96%, and its properties are similar to those of quartz glass. ③ Soda lime glass. It mainly contains SiO 2 and also contains 15% Na 2 O and 16% CaO. It is low in cost, easy to shape, suitable for large-scale production, and its output accounts for 90% of practical glass. It can produce glass jars, flat glass, utensils, light bulbs, etc. ④ Lead silicate glass. The main components are SiO 2 and PbO, which have high refractive index and high volume resistance, and have good wettability with metals. They can be used to make bulbs, vacuum tube stems, crystalline glassware, flint optical glass, etc. Lead glass containing a large amount of PbO can block X-rays and γ-rays. ⑤ Aluminosilicate glass. With SiO 2 and Al 2 O 3 as the main components, it has a high softening temperature and is used to make discharge bulbs, high-temperature glass thermometers, chemical combustion tubes and glass fibers. ⑥Borosilicate glass. With SiO 2 and B 2 O 3 as the main components, it has good heat resistance and chemical stability. It is used to make cooking utensils, laboratory instruments, metal welding glass, etc. Borate glass is mainly composed of B 2 O 3, has a low melting temperature, and can resist corrosion by sodium vapor. The borate glass containing rare earth elements has high refractive index and low dispersion. It is a new type of optical glass. Phosphate glass uses P 2 O 5 as the main component, has low refractive index and low dispersion, and is used in optical instruments.
In addition, glass is divided into toughened glass, porous glass (ie, foam glass, with a pore size of about 40, used for seawater desalination, virus filtration, etc.) according to performance characteristics, conductive glass (used as electrodes and aircraft windshields), glass-ceramics , Opal glass (used for lighting devices and decorative items, etc.) and hollow glass (used as door and window glass), etc.
Production process The main raw materials for glass production are glass forming bodies, glass adjustments and glass intermediates, and the rest are auxiliary raw materials. The main raw materials refer to the oxides introduced into the glass to form the network, intermediate oxides and off-network oxides; auxiliary raw materials include clarifiers, fluxes, opacifiers, colorants, decolorants, oxidants and reducing agents.
The glass production process mainly includes: ①Pre-processing of raw materials. The lumpy raw materials are crushed, the wet raw materials are dried, and the iron-containing raw materials are processed for iron removal to ensure the quality of the glass. ② Preparation of batch materials. ③Melting. The glass batch material is heated at a high temperature in a tank kiln or a crucible kiln to form a uniform, bubble-free liquid glass that meets the molding requirements. ④Forming. Process liquid glass into products of required shapes, such as flat plates, various utensils, etc. ⑤ Heat treatment. Through annealing, quenching and other processes, the internal stress, phase separation or crystallization of the glass can be eliminated or generated, and the structural state of the glass can be changed.
