L32 - SUMMARY FROM LAST CLASS Glasses The main families of...

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Dr. P. Lucas U of A MSE 110 Glasses The main families of glasses are oxides, halides, chalcogenides and metallic glasses. Common industrial glasses are based on silica (SiO 2 ). The structure of silicate glasses is based on a network of corner sharing SiO 4 tetrahedra. Oxygen atoms shared by two tetrahedra are bridging oxygens while charged terminal oxygen atoms are non-bridging oxygens . Non-bridging oxygens are generated by additives such as Na 2 O and CaO and interrupt the silicate network thus changing the properties of the glass such as the viscosity. Pyrex is resistant to thermal shock due to its low thermal expansion coefficient. Tempered glass resists fracture because its surface is under a compressive stress introduced by surface quenching. Cooling rates of 10 6 ºC/s are required to form metallic glasses and limits the process to thin strips formed by compression of the molten metal on a cold rotating wheel. SUMMARY FROM LAST CLASS
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Dr. P. Lucas U of A MSE 110 Light OPTICAL PROPERTIES OF MATERIALS Light is an electromagnetic wave. An electric and magnetic field oscillating perpendicular to the direction of propagation. In vacuum, the wave propagates at the speed of light c = 3×10 8 m/s . In air, the density of atoms is so low that the speed of light is approximately c = 3×10 8 m/s. When light penetrates a transparent solid, the oscillating electric field feels the charged particles (nucleus, electrons) composing the solid and the light is slowed down to a velocity v lower than c.
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Dr. P. Lucas
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L32 - SUMMARY FROM LAST CLASS Glasses The main families of...

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