National Physical Laboratory

Thermal Conductivity by Thermal Diffusivity

Laser Flash Apparatus

The laser flash apparatus (LFA) is an instrument used to measure the thermal diffusivity (a) of materials with respect to temperature. This can then be used to calculate thermal conductivity (λ) if the density (ρ) and specific heat (Cp) of the sample as a function of temperature are already known. The Netzsch LFA427 has a temperature range from 25 °C to 1600 °C (or 2000 °C with modifications).

Laser Flash Apparatus equation

The LFA may be used to assess thermal diffusivity of a wide range of materials including metals and alloys (in solid and liquid phases), ceramics, hard metals, coated materials and MMCs.

Laser Flash Detector Signal graph
  • Thermal diffusivity range: 0.01 mm2/s to 1000 mm2/s

  • Temperature range: 25 °C to 2000 °C

  • Sample dimensions: 6 mm, 10 mm or 12.7 mm diameter

  • Inert, static and dynamic atmosphere conditions

The specimen is mounted in a furnace, and at the required measurement temperature, a short pulse of laser energy is allowed to fall upon one side of the specimen. The diffusivity is calculated from an analysis of the transient temperature rise at the opposite side, measured with an infrared detector. The 5t0.5 or 10t0.5 radiant heat loss correction is applied, as well as another correction for the finite duration of the laser pulse.

Last Updated: 22 Feb 2017
Created: 25 May 2011


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