Specific heat laser flash technique

A laser flash technique can be used for determining the thermal conductivity of fibers (Whittaker et al., 1990). The laser flash technique provides us the dilfusivity, a, which, in turn, is a function of the thermal conductivity, specific heat, and density of the material. Thus,... 

The laser flash technique has been used to measure the specific heat of fibre-reinforced phenol-formaldehyde resins [31]. This technique has also been used to determine the specific heat of PVDF [45, 52]. 

The thermal properties of ZnO doped with A1 and Mg were also studied by a number of groups [149-153] for the evaluation of the thermoelectric performance. Tsubota et al. [152] investigated the thermal conductivity of sintered (Zni yMgy)i xAlj 0 (x O-Q. , y = 0-0.1) samples determined from thermal diffusivity and specific heat capacity measured by the laser flash technique and differential scanning calorimetry (DSC), respectively. The temperature dependences of the thermal conductivities of (Zni yMgy)o.9gAlo.o20 (y = 0.0-02,0.1) are shown in Figure 1.29 in comparison with that of ZnO. The reduction of k from... 

In the laser flash method, a melt of interest is placed between two parallel plates. The upper plate is heated stepwise and the thermal diffusiv-ity is measured from the rise in temperature. The specific design for molten materials and especially slags employed by Ohta et al. is based on the differential three-layer technique utihzing a special cell that can be accommodated in the system. A schematic diagram of the principle of the measurement section is shown in Fig. 31. A laser pulse irradiates the upper (platinum) crucible and the temperature response of the surface of the lower platinum crucible is observed, a liquid specimen being sandwiched between the two. 

In this chapter, five methods of determining the thermal conductivity of solids are described. The final technique, laser flash, is a method of measuring the thermal diffusivity, from which the thermal conductivity may be obtained if the specific heat and density are known. In the following sections, the operating principles of each technique are described. Novel techniques for measurements of this form appear every year— reference [l] is suggested for a start on contemporary literature. 

Transient methods such as the flash laser technique (FLT) enable fast, accurate, and localized measurements, and they eliminate the contact-resistance effects. However, these measurements are difficult or impossible on semitransparent samples such as the porous GDL materials. Special sample preparation such as thin surface coatings with well-characterized materials can be used (Kehoe et al., 1998). If such approaches prove successful, they will enable thermal diffusivity o(T) and specific heat Cp(T)... 

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