5B

5B

1. Polystyrene + PMMA=strong dipole, large side groups, brittle, amorphous

2. ceramic

   • inorganic, non-metallic material- compound= metallic+non-metalic
   • glass-non-crystalline silicate, contain other oxides=affect properties
   • Glass ceramic-fine grain polycrystalline, formed by HT, better strength+thermal shock resistance
   • deformation
     • RT=brittle failure
     • high temps=plastic but difficult= ceramics are:
       • ionic crystals, dislocations=not move easily
       • covalent crystals-silicates, Vstrong bonds between atoms,
       • non-crystalline- no dislocations- plastic def=viscous flow of atoms

3. refractory

   • withstand high T with out decomposing/melting. Furnace linings- alumina+silica+(Al2O3+SiO2+MgO)

4. abrasives

   • wear/cut away/grind material
     • high hardness+some "refractoriness"
       • silicon carbide, SiC, tungsten carbide, WC

5. clay

   • "plastic" natural mineral-alumina+silica=dissolved rocks=supersaturated=crystals grow.
   • structural clay=bricks, tiles
   • whiteware-tableware

6. cement

   • clay+lime mix=calcination
     • calcium silicates, harden=hydration reactions=calcium silicates+water
       • micro-structure, voids=black, hydrated cement-grey, un-hydrated cement=white
   • concrete constituents=added=composite material
     • compression stress=15-40MPa, tensile-1-4MPa

7. ceramics=bend test=stronger in compression=many little cracks

   • 3 point bend test= YM+rupture strength

8. composite

   • two or more materials combined
     • disperse one in matrix of other
       • fibres strengthen , matrix polymer=protects brittle failure
     • composite=exhibit properties of both, i.e. polymer= ductile, weak+flexibly, ceramic=strong, stiff, brittle, composite=strong, stiff, tought
   • anisotropy of stiffness
     • longitudinal/transverse stiffness=different
       • get rid of low traverse=ply

9. concrete

   • aggregate=60-80%=reduce cement needed, sand=fill spaces, sufficient cement=coat aggregate+bond
     • too little water=incomplete bonding, too much-excessive porosity, both reduce strength
     • weak in tension=pre stressed=tension steel=same thermal expansion+good bond, set concrete tension=released=compression

10. wood= heterogeneous, hygroscopic, cellular, anisotropic material-cellulose=40-50%, hemicellulose-15-25%, linging-15-30%

    • tests= done at 12% moisture+20 degrees