无机非金属材料专业英语-8解析.ppt

The fact that is not easy to obtain the desired characteristics in a normal furnace inspired the conception of an entirely new glass melting process; refining is carried out under reduced pressure which also removes the traces of sulfide. This technology remains, for now, the exception that proves the rule that progress in glass making has usually been achieved by evolution rather than revolution. Each of these new products has given rise to significant progress in glass quality. The transparent cooker top in particular implies not only absence of visible macroscopic defects but also the absence of even smaller inclusions that might prevent the mechanical shock resistance from reaching the particularly high level required. Glass for Activity-Matrix Liquid-Crystal Display panels For this application, thin sheets of glass are required containing no seed bigger than a few hundreds of a millimeter and with perfectly flat surfaces obtained with as little polishing as possible after forming. These two basic requirements imply unusually high degrees of refining and of homogeneity. Other properties are also essential; a high strain point( to avoid “compact” during the heat treatments associated with the production of the grid transistors) absence of alkali( which might diffuse into the liquid crystal and transistor layers.) low on expansivity (to match the amorphous silica used) and resistance to acids (used during the process). The absence of alkali and relatively low expansion leads to the use of B2O3 which, being somewhat volatile, may eventually complicate the attainment of the required homogeneity. 3. Electric Melting The cold-top electric furnace is essentially non-polluting and is chosen for melting glasses such as fluoride opal or lead crystal. Its greatest handicap is the cost of electric power which in Europe is more expensive than gas by a factor that varies from 3 in Switzerland to 10 in Spain. Electr