Reliable measurement of thermal diffusivity in many cases can be obtained through the laser flash technique. In this method, a short pulse (less than 1 millisecond) of heat is applied to the front face of a specimen using a laser flash, and the temperature change of the rear face is measured with an infrared (IR) detector.

Laser Flash Thermal Diffusivity System

The laser-flash thermal diffusivity (LFTD) system is designed to acquire data automatically, from cryogenic temperatures up to 2500^oC. Data analysis algorithms interpret the rear face temperature response and provide instrumental and specimen dependent corrections.

6 Sample Carousel

LFTD is used in the study of microstructural factors affecting the thermal transport properties of materials. A small planar specimen is placed in an evacuated tube furnace and oriented with its flat surfaces perpendicular to the furnace axis. Users should contact TPUC staff to discuss required specimen size.

A neodymium/glass laser is used to supply a high-intensity, short-duration pulse of thermal energy to one face of the test specimen. The intensity of the beam is controlled by varying the laser power supply and use of attenuating filters. The resulting temperature rise of the other face of the test specimen is monitored as a function of time by an indium antimonide (low temperatures) and a silicon (high temperatures) infrared (IR) detector and stored in computer memory. The thermal diffusivity is determined from a numerical analysis of the IR detector output. Users typically learn the menu-driven computer software in less than one working day.

Features:

• Extended temperature range (-150 to 2500^oC)
• Mounts for solids and molten metals (to 1700^oC)
• Enhanced environmental options (vacuum, inert, oxidizing, or reducing atmospheres)
• Rapid numerical data analysis of temperature rise versus time
  • Finite pulse width and heat-loss corrections
  • Corrections for partially transparant specimens
  • Analysis options for two- and three-layer systems
  • Thermal contact resistance measurement
• Flexibility
• Six-sample carousel
• Unused electrical feed-thrus
• Other thermal property measurements
• Focused quartz lamp furnace to 1000^oC.
• Quench to intermediate temperatures
• Thermal shock studies
• Option for electrical resistivity of metals versus temperature

Applications:

Thermal conductivity is often a property of great interest in the development of high-performance materials. However, thermal conductivity measurements at high temperatures are difficult and time consuming, and they require relatively large specimens. Thermal conductivity may be calculated from measurements of thermal diffusivity, specific heat, and bulk density. The laser flash method for obtaining thermal diffusivity (LFTD) is relatively fast and requires only a small amount of material, an important consideration in research on new, experimental materials. The LFTD technique has been used extensively in the study of factors affecting the properties of materials, such as processing conditions, composition, heat treatments, sintering aids and dopants, composite structure, grain size, and porosity. The technique has been applied to a wide range of materials including glasses, plastics, metals, ceramics, composites, crystals, and foams.