Determination of Thermal Conductivity
The thermal conductivity, also thermal conductivity of a solid or a liquid, is its ability to transport thermal energy in the form of heat. The (specific) thermal conductivity is given in watts per Kelvin and meter and is a temperature-dependent material constant.
The thermal conductivity is to be distinguished from the thermal diffusivity, which indicates the rate at which a temperature change propagates through a substance. Knowledge of the thermal properties of solids and liquids is becoming increasingly important today.
In many applications, such as automotive, aerospace, energy, ceramics, glass, and building materials, very precise information about the thermal behavior of the materials used is of utmost importance.
Thermal management of buildings, for example, is becoming an increasingly important topic due to the skyrocketing energy costs. Heat flows also play a major role in the semiconductor industry, for example when thinking of modern integrated systems such as computer processors.
Applications for thermal conductivity
Application: Measurement of copper-fiber
Introduction and Application: Fiber-reinforced polymers are composite materials made of a polymer matrix reinforced with fibres. The useful attributes (low specific weight, high E-modulus) are being increasingly applied in industrial practices. Through the reinforced fibers its possible to well-directed modifies the properties. Therefore it is important to know the properties especially for high-end applications.
Analysis using LFA: The picture shows the thermal diffusivity and the thermal conductivity in plane are higher than the results normal to the fiber orientation. Consequently this measuring method is a good tool for analysing the material properties and checks the agreement with the favoured application.
Application: Analysis of PEEK
Introduction and application: Polyetherketone (PEK) are high temperature resistant and belongs to the group of thermoplastics. The most important exponent of the polyetherketone is the Polyetheretherketon (PEEK). The melting point of PEEK is 335°C. Polyetherketone are resistant to organic and inorganic chemicals, to hydrolysis until 280°C. Because of its robustness, PEEK is used to fabricate items used in demanding applications, including bearings, piston parts, pumps, compressor plate valves, cable insulation and medical implants.
Analysis using LFA: The thermal conductivity increases linearly. The thermal diffusivity decreases with an increasing temperature. And the specific heat increases with an increasing temperature. Between 150°C and 170°C are steps in both thermophysical properties (thermal diffusivity and specific heat) due to the glass transition.
Application: Thermal conductivity measurement (DC) using Thin Film Analyser
Thermal conductivity of a Bi0.9Sb0.1 film with a thickness of 100nm as function of temperature.
Application: Thermal conductivity measurement (DC & AC) using Thin Film Analyser
Thermal conductivity of an 800nm thin SiO2 / Si3N4 sandwich, measured with the steady state (red) and the transient (blue) technique in the temperature range 80-300K.