Chap.4-1材料概论第四章.ppt

4.3.6 Physical Properties 4.3.6.1 Density Thermal history of a glass?properties density of glasses: - is dependent upon thermal history - decreases with temperature The density range: 2.2 ~ 8.0 g/cm3 A lower density: obtained by the more rapidly cooled glasses 4.3.6.2 Hardness MOHS hardness: between apatite 磷灰石 and quartz, 6.5. Glasses: brittle in a macroscopic scale, but they can flow under shear stresses in a microscopic scale. Hardness: is a property closely related to the mechanical strength of a glass and to its low temperature viscosity. * Chapter 4 The Glass Science 玻璃科学 4.1 the World of Glasses 4.1.1 Natural Glasses天然玻璃 The volcanic outflow of the molten magma from the earth: get cooled and form glasses.在从地球的熔融岩浆火山流出：冷却和形成得到玻璃。 Impactites 冲击岩: formed from crystalline结晶materials rendered 致使 amorphous无定形by the shock休克of meteoric流星impact. Glasses: formed from impacted melts are known as tektites 玻殒石. Tektites: over the world – Australia, Indian Ocean, Europe, Libyan desert Composition: alumino-silicate glasses At least 700,000 years old Micro-tektites: diameter 1 millimeter, are light yellow-brown in colour. 4.1.2 Glass in Modern Times 现代玻璃时代 Sheet glass平板玻璃: a few mm in thickness在几个毫米厚度 Glass fibers: by extruding 挤压melts through metal orifices 孔 and rolled冷轧on to large diameter spindles 纺锤 or are gathered as (fibrous) glass-wool. Use of glass fibers: As insulating 绝缘materials for information transmission信息传输 Plate glass: by a float process where melts are made to settle and freeze on molten tin pools, which provide optically smooth and parallel surfaces. Colour glasses: by adding oxides or halides and made to change their colours 卤化物 to change their colours. 4.1.3 Different Types of Glasses Oxide glasses: silicate or alumino-borosilicate glasses containing a variety of monovalent and divalent oxides. Silica and silicate glasses: building materials 90%: is based on oxides and in pa