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glass manufacturing
Glass ingredients
Quartz sand (silica) as main raw material for commercials for phone free articles blown glass production oldest-mouth glass window in Sweden (Kosta Glasbruk, Småland, 1742). In the middle is the free items guide mark glass blower pipe.
pure silica (SiO2) has a "glass melting point" – at a viscosity of 10 Pa.s s (100 P) – more than 2300 ° C (4200 ° F). While pure silica can be made into glass for special applications (see fused quartz), other substances are added to common glass to simplify processing. One is sodium carbonate (Na2CO3), which reduces the melting point of about 1500 ° C (2700 ° F) in soda-lime glass;
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"Sosa" refers to the original source of sodium carbonate in soda ash obtained from certain plants. However, the soda makes the glass water soluble, which is usually undesirable, as calcium oxide lime ((CaO), generally obtained from limestone), some Magnesium oxide (MgO) and aluminum oxide (Al2O3) are added to provide a better chemical durability. The resulting glass contains about 70-74% silica weight and is called a soda-lime glass. [8] glasses of soda-lime represent about 90% of manufactured glass.
As well as soda and lime, glass more has other ingredients common to change its properties. Lead glass, such as lead crystal or rock crystal, is more 'brilliant' because the index Refraction causes noticeably more "sparkles", while boron may be added to change the thermal and electrical properties, such as Pyrex. Barium addition also increases the refractive index. Thorium oxide has a high refractive index glass and low dispersion, and was used in the production of high quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern glasses. Large amounts of iron are used in glass absorbs infrared energy, such as heat absorbing filters for movie projectors, while cerium (IV) oxide can be used for glass that absorbs UV wavelengths (biologically damaging ionizing radiation).
Two other common ingredients are calumite glass (an iron industry by product) and "cullet (recycled glass). Recycled glass saves raw materials and energy. However, impurities in the cullet may lead the failure of the product and equipment.
Finally, the fining agents such as sodium sulfate, sodium chloride or antimony oxide are added to reduce content of the bubble in the glass. [8] Glass batch calculation is the method by which we determine the right mix of raw materials to make glass composition desired.
[Edit] Contemporary glass production
Following the glass batch preparation and mixing, the raw materials are transported the oven. soda lime glass for mass production is melted in gas units. Small-scale furnaces for specialty glasses include electric melters, pot furnaces and day tanks. [8]
After melting, homogenization and refining (removal of bubbles), glass is formed. Flat glass for windows and similar applications is formed by the float glass process, developed between 1953 and 1957 by Sir Alastair Pilkington of Pilkington and Kenneth Bickerstaff UK brothers, who created a continuous ribbon of glass with a molten tin bath in which molten glass flows unhindered under the influence of gravity. The upper surface of the glass is subjected to nitrogen under pressure to obtain a polished finish. [9] Container glass for common bottles and jars is formed by blowing and pressing methods. Other glass forming techniques are summarized in the table Glass forming techniques.
Once the desired shape, the glass is usually annealed for stress relieving. Surface treatments, coatings or lamination may follow to improve the chemical durability (glass container coatings, treatment of interior glass containers), strength (toughened glass, bulletproof glass, windshields), or optical properties (glazing insulation, anti-reflective coating).
[Edit] Glassmaking in the laboratory
A vitrification experiment for the study of the elimination nuclear waste in the Pacific Northwest National Laboratory. No laboratory glass melting test. The striations must be avoided through good homogenization.
New chemical glass compositions or new treatment techniques can be initially investigated in small scale laboratory experiments. The raw material for the laboratory-scale glass melts are often different from those used in mass production because the cost factor is a low priority. In the laboratory, on all pure chemicals are used. Care should be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as oxides alkali hydroxides, alkaline oxides and hydroxides, or boron oxide), or that impurities are quantified (loss on ignition). [10] Evaporation losses during glass melting should be considered during the selection of raw materials, for example, sodium selenite may be preferable to SeO2 can easily evaporate. In addition, easier to react the raw materials may be preferred over relatively inert, such as Al (OH) 3 on Al2O3. Usually, the melts are carried out in crucibles platinum to reduce the contamination of the crucible. Glass homogeneity is achieved by homogenizing the mixture of raw materials (glass batch), stirring fusion and crush and re-melt the first merger. The glass is usually obtained by annealing to prevent breakage during processing. [10] [11]
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