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Calcined Kaolin

Formula: Al₂O₃.2SiO₂

Clean kaolins are calcined by firing the powder in a rotary calcining kiln to a temperature high enough to effect loss of crystal water (and accompanying mineral change). Calcined kaolin normally converts to mullite during this process.

Calcined kaolins soften at about cone 35 and are used in refractory castables and furniture, thermal insulation bodies, low expansion bodies, permeable ceramic compositions, and investment casting (see molochite).

Calcined kaolin is also valuable in glaze formulations that contain high amounts of kaolin to source alumina and which are thus subject to shrinkage and cracking-during-drying problems. By substituting some of the raw kaolin for calcined the physical properties of the glaze slurry can be controlled without impacting the chemistry of the fired melt. Mixing the two materials must of course take into account that raw kaolin has a 14-15% LOI that the calcined material does not.

Calcined kaolins are also useful in tuning the shrinkage and plasticity of slips which are applied to wet, leather hard or dry ware. Because their shrinkage is very low, they can be substituted for part of the regular kaolin and there will likewise be minimal impact on the fired properties.

Mechanisms

• Body Thermal Expansion - Low

  A useful material for refractories and low expansion applications.

Out Bound Links

• (Typecodes) 1: REF - Refractory
• (Materials - Parent) Kaolin - Al2O3.2SiO2 or Al2Si2O5(OH)4 - Hydrated alumina silicate, Pure clay mineral

  China Clay

• (Hazards - General) Kaolin
  The hazards of using this material in the ceramic ...
• (Typecodes) 1: GNM - Generic Material
• (Typecodes - Type) 1: KAO - Kaolin
• (MDT - Member) Glass Industry

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• (Typecodes) 1: LEM - Low Expansion Material
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In Bound Links

• (Materials - Parent) Glomax LL Calcined Kaolin - Calcined Kaolin

  Glomax Kaolin, Ajax Glomax Kaolin

• (Materials - Parent) Burgess Iceberg Calcined Kaolin

  Icecap K

XML for Import into INSIGHT

<?xml version="1.0" encoding="UTF-8"?>
<material name="Calcined Kaolin" descrip="" searchkey="Cal Kaolin" loi="0.00" casnumber="94552-04-2">
<oxides>
<oxide symbol="Al2O3" name="Aluminum Oxide, Alumina" status="" percent="45.900" tolerance=""/>
<oxide symbol="SiO2" name="Silicon Dioxide, Silica" status="" percent="54.100" tolerance=""/>
</oxides>
</material>

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