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Which Materials would be best for IR Ceramic Coating

  1. Jun 23, 2017 #1
    Which materials would be best for an IR reflective/opaque coating to improve the efficiency of ceramic insulation materials for use in kilns and furnaces, meant for continuous use at up to 2500 deg F?

    I understand that materials might be useful for different wavelengths of IR, so details regarding which wavelengths are reflected would be helpful.
     
  2. jcsd
  3. Jun 29, 2017 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
     
  4. Jun 30, 2017 #3

    Baluncore

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    A kiln at 1370°C radiates broadband IR centred on about 2 um. Any insulation will need to be broadband, which precludes the use of tuned λ/n reflective layers. It is probable that an IR-reflective, electrically conductive metallic mirror would be an advantage as an internal surface as it is broadband in it's reflectivity.

    You have considered radiation, but conduction and convection will also be costing energy.

    To reduce conduction losses requires low thermal conductivity materials be used for wall structure where the inner envelope wall is connected to the external wall. Filling spaces between the walls with material having a low thermal conductivity suggests having many layers of internal IR reflectance = mismatched impedance between the walls. Avoid homogeneous solids. That is usually done in bulk by filling with vermiculite or making the walls from a ceramic foam.

    Convection can be reduced by having a vacuum envelope, or by filling the envelope with vermiculite to reduce convective airflow inside the wall.
     
  5. Jul 4, 2017 #4
    Vermiculite does not handle temperatures that high very well; around 760°C is typical max working temp.
     
  6. Jul 4, 2017 #5
    If you want to improve the efficiency of your 2500 deg F continuous use kiln or furnace, highly reflective material might not necessarily be ideal.
    Continuous use suggests product is regularly being transported and that there are openings continually or regularly. Reflected IR might head out the openings rather than heat the work piece. In those cases, having a high emissivity coating might work better.
    Highly reflective materials are typically low emissivity. If product is often moving through the space, better to have the walls stay at high temperature and provide more uniform emitted IR.
    Here is a table of material emissivity at various temps.
     
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