The Development of Microwave Thermal Analysis (MWTA)and its application to the study of Carbons and other materials

Abstract

This research involves the development of a totally new approach to thermal analysis in which microwave energy is used not only to heat the sample but also to detect thermally induced transformations via the effects of changes in its dielectric properties. Use of these properties, rather than the more usual mass or enthalpy changes of conventional thermal analysis, provide a unique insight into thermal processes. Microwave thermal analysis (MWTA) is a technique for studying the efficiency of the conversion of microwave to thermal energy by measuring the microwave power-temperature relationship for different materials. Power/temperature verses time profiles in some cases give an indication of physical and chemical changes occurring in the sample, via changes in the dielectric constant. An instrument for performing microwave thermal analysis (MWTA) has been designed, constructed and applied to an extensive range of chemical systems exhibiting a variety of physicochemical transformations, including melting, decomposition and solid-solid phase changes. MWTA has been shown to provide both qualitative and quantitative information with sample masses ranging from the analytical (1 to 20 mg) to semi-preparative (0.5 to 5.0 g) scales. It has been demonstrated that MWTA can be used in conjunction with complementary techniques such as differential thermal analysis (DTA) and X-ray powder diffraction (XRD) to provide additional data. MWTA has the potential to be extended to incorporate some of the latest developments in thermal analysis, including methods involving temperature modulation and evolved gas analysis. MWTA has the potential to have applications in the design of industrial processes by providing detailed information on the effect of microwave radiation on both physical (e.g. phase changes) and chemical processes