Sample Preparation and Testing

Samples are normally coated with a graphite film before testing.  The graphite serves several purposes.  When testing samples that do not naturally have a high value of emissivity or absorptivity, the graphite increases the energy absorbed on the laser side (bottom) and increases the temperature signal on the detector side (top) of the sample.  Also, a uniform graphite coating applied to both sample and reference material helps maintain similar absorptive and emissive efficiencies among samples, which is needed for accurate specific heat measurements.

Some materials are transparent to infrared radiation and must be coated with a metal film on both sides.  this prevents penetration of the laser beam into the sample.  Typically, a 1000 Å gold or gold alloy film is sputter coated onto the sample.  To assure proper test results, a film is applied to all low density samples which includes most unfilled polymers, as well as many ceramics and glasses.