Class17

Class17 - Technologies for Materials Ionic substances...

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Technologies for Materials Ionic substances Ceramics/insulators Glass Metallic substances Structural materials Materials that conduct heat/electricity Molecular covalent substances Polymers/plastics/elastomers Network covalent substances Semiconductors Low temperature superconductors High temperature superconductors Composites
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Technologies for ceramics and glasses Available since 9000 BC Ceramics are ionic substances formed by heating mixtures of ionic substances to high temperatures Ceramics involve repeating structures of ions held together by ionic bonds (crystalline substances) Frequently involves oxides that are able to resist reaction when exposed to air Most common involve clay, Al 2 O 3 .2SiO 2 .2H 2 O
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Ceramics have useful properties Typical ionic: brittle, high MP and BP Not subject to corrosion since they are usually fully oxidized Poor conductors of heat and electricity since ions are not free to move in solid: Used as thermal insulators in construction (bricks and concrete), fire places, furnaces, smoke stacks, etc. Ceramics are used as electrical insulators Glazed ceramics have surfaces that have been converted to glass-like substances and are impervious to water
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Fine/Beal, Chemistry for Engineers and Scientists, Saunders, NY, 1990, 694 Ceramic - crystalline structure Glass - amorphous structure *Si = red, O = gray, Na = yellow Structural difference between a ceramic and a glass * *
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Technologies for Metals Available since 6000 BC Some unique properties of metals that make them useful to society: Luster – surface reflects light Malleability – able to be deformed without breaking Ductile – can be drawn out into a wire Electrical Conductivity Conduct electricity at room temperature Conductivity decreases as temperature increases http://www.hometrainingtools.com/articles/learn-about-metals-science-teaching-tip.html
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Production of most metals requires chemical reduction
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This note was uploaded on 10/19/2011 for the course CHEM 83 taught by Professor Bonk,j during the Fall '08 term at Duke.

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Class17 - Technologies for Materials Ionic substances...

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