Glass was first formed by the solidification of acidic rock ejected by volcanoes. About 3700 BC, the ancient Egyptians had made glass ornaments and simple glassware, then only colored glass, 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 made the plate glass lead machine. Since then, with the industrialization and scale of glass production, various uses and various properties of glass have come out one after another. In modern times, 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 composition. Non-oxide glass varieties and the number of few, mainly sulfur glass and halide glass. The anions of chalcogenide glass are mostly sulfur, selenium, tellurium, etc., which can pass through yellow, red, near and far infrared light by cutting off short wavelength light. Its resistance is low, and it has switching and memory characteristics. Halide glass has low refractive index and low dispersion, so it is mostly used as optical glass.
Oxide glass is divided into silicate glass, borate glass, * acid glass and so on. Silicate glass refers to the basic composition of SiO 2 glass, its variety, wide use. Usually according to the glass SiO 2 and the different content of alkali metal, alkali earth metal oxide, and divided into: ① quartz glass. SiO 2 content is more than 99.5%, low thermal expansion coefficient, high temperature resistance, good chemical stability, ultraviolet light and infrared light, high melting temperature, high viscosity, molding is difficult. It is widely used in semiconductor, electric light source, optical communication, laser and other technology and optical instruments. ② high silica glass. The SiO 2 content is about 96% and its properties are similar to those of quartz glass. ③ Sodium calcium glass. It is mainly composed of SiO 2, 15% Na 2 O and 16% CaO. It has low cost, easy molding and is suitable for mass production. Its output accounts for 90% of the practical glass. Can produce glass bottles, plate glass, utensils, bulbs and so on. ④ lead silicate glass. The main components are SiO 2 and PBO, with ****** high refractive index and high volume resistance, and metal has a good wettability, can be used in the manufacture of light bulbs, vacuum tube core column, crystal glassware, flint optical glass and so on. Lead glass containing large amounts of PBO can block X-rays and γ-rays. ⑤ Aluminum silicate glass. With SiO 2 and Al 2O 3 as the main components, soft deformation temperature is high, used in the production of discharge bulbs, high temperature glass thermometers, chemical combustion tubes and glass fiber, etc.. ⑥ Borosilicate glass. With SiO 2 and B 2O 3 as the main components, has good heat resistance and chemical stability, used in the manufacture of cooking utensils, laboratory instruments, metal sealing glass and so on. Borate glass with B 2O 3 as the main composition, melting temperature is low, can resist the corrosion of sodium vapor. Borate glass containing soil element is a new type of optical glass with high refractive index and low dispersion. * Sate glass with P 2O 5 as the main component, low refractive index, 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, * *, the disease filter used in seawater, etc), conductive glass (used as electrical * and aircraft windshield), microcrystalline glass, * turbidity glass (used for lighting devices and decoration items, etc.) and hollow glass (used for door and window glass), etc.
Production process The main raw materials of glass production are glass formators, glass adjusters and glass intermediates, and the rest are auxiliary raw materials. The main raw materials guide into the glass to form oxides, intermediate oxides and oxides outside the network; Auxiliary raw materials include clarifiers, fluxes, turbidity agents, colorants, decolorizing agents, oxidants and reducing agents, etc.
Glass production process mainly includes: ① raw material pre-processing. The block material is crushed to dry the wet material, and the iron containing material is removed to ensure the quality of the glass. ② preparation of complex materials. (3) melted. The glass mixture is heated at high temperature in the pool kiln or the crucible kiln to form the liquid glass with uniform, no bubble and in line with the molding requirements. (4) shape. The liquid glass is processed into the desired shape of products, such as plates, utensils, etc. ⑤ Heat treatment. By annealing, quenching and other processes, eliminate or produce the stress, phase separation or crystallization inside the glass, and change the structural state of the glass.
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