FRSC 302 Lecture Notes - Lecture 3: Atomic Number, Refractive Index, Scanning Electron Microscope
7 Feb 2017
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Document Summary
Common types of physical evidence: glass, paint chip, documents. Structure: glass is a rigid liquid. At high temperatures glass is in a molten liquid state. When cooled the glass stops flowing and takes the appearance of a solid but still amorphous: the internal structure is not regularly crystalline but randomly disordered as a liquid even though it appears as a solid. Mechanical properties: glass behaves like an elastic solid. In thin sheets or fibers it is malleable elastic. When glass is cracked, the side where the force is applied is strengthened, but the opposite side is weakened. Process for producing safety glass by controlled thermal or chemical treatments to increase strength compared to normal glass. Thermal toughening heat glass above transformation temperature and then the surface is cooled rapidly. Chemical toughening white hot glass is placed in contact with salt, ion exchange with smaller ions from glass.
