Polymer precursor derived ceramics resistive heater for multi-anvil and toroidal HP/HT experiments
Recently, numerous efforts have been made to significantly extend the pressure and temperature range as well as sample volume in high pressure high temperature (HP/HT) experiments, especially with the aim of opening up the research areas of geoscience and materials science. HP/HT apparatus thus becomes an important experimental tool of all above researches. There are various HP/HT apparatus which could achieve a range of pressures and temperatures with different sample sizes. Normally, relative large volume sample could be obtained by multi-anvil type and toroidal type HP/HT apparatus.
During the HP/HT experiments, the setup of the assembly will affect the results strongly. The assembly usually contains furnace (resistive heater and insulator), pressure medium and thermocouple etc. Among all the parts, furnace may be the most important part. Temperature increases when the electric current flows through the resistive heater. Hence the properties of the resistive heater are the concern of researchers.
The widely used materials for the resistive heater are graphite, high melting point metals, LaCrO3 and some composites. However, graphite is limited to 10 GPa due to the transformation to diamond; doped diamond need more fabrication work; metals are usually expensive; LaCrO3 has a high activation energy, which leads to difficult to “start” at room temperature; composites showed some good results, while the fabrication usually requires high temperature sintering in advance. Besides the materials selection, machinability is another consideration ingredient. The widely employed shape of the furnace in large volume HP/HT apparatus is tube like. Thus the tubular form of the resistive heater should be possible/easily to be machined.
To overcome the drawback of above, a new polymer-precursor-derived composite (PPDC) for resistive heater in HP/HT apparatus will be investigated, polymer-derived ceramics (PDCs) processing was used for the possibility of low fabrication temperature and easily manufacture. The processes and properties related to the preparation and HP/HT runs will be studied.
Contact: Dr. Marcus Schwarz