Development of anvil with sintered diamond core for high pressure high temperature experiments

本研究项目的目的是开发金刚石烧结核砧，并利用这种新砧产生高压和高温。我们研制了两种由碳化钨和烧结金刚石芯组成的Bridgman铁砧。铁砧直径为26毫米和20毫米。我们还建造了一台600吨的压力机，用于压缩布里奇曼铁砧以产生高压。使用这些仪器，在本项目期间获得了以下结果：我们已经成功地使用新砧产生了高达20.5 GPa的压力。这种产生的压力远远高于由碳化钨制成的Bridgman铁砧所达到的压力。新砧也被用于高达17 GPa和1400 tc2的高压高温实验。进行了以下相变实验。确定了KAlSi_3O_8长石到K_2Si_4O_9宽晶石+ Al_2SiO_5蓝晶石+ SiO_2硅辉石（或硅辉石）以及到KAlSi_3O_8荷兰石的相界。研究了CaAl_2O_4铁氧体钙的稳定场。确定了CaFeSi_2O_6斜辉石分解为CaSiO_3钙钛矿+ Fe_2SiO_4尖晶石+SiO_2辉石的边界。这些相界在下地幔中具有重要的地球物理和地球化学意义。利用原位x射线衍射技术，在高压高温条件下精确测定了TiO_2中金红石- α - pbo_2的过渡边界。这个边界对于高温下的压力校准很重要。

The purpose of this research project is to develop anvils with sintered diamond cores and to generate high pressures and high temperatures using the new anvils. We have developed two kinds of Bridgman anvils which consist of tungsten carbide with sintered diamond core. The diameters of tlie anvils are 26 and 20 mm. We have also constructed a 600-ton press, which is used to compress the Bridgman anvils to generate high pressures. Using these apparatus, the following results have been obtained during this project term.1. We have successfully generated pressure up to about 20.5 GPa using the new anvils. This generated pressure is much higher than those attained by Bridgman anvils made of tungsten carbide. The new anvils have also been used for high pressure high temperature experiments up to 17 GPa and 1400 ﾟC.2. The following phase transition experiments have been caried out. Phase boundaries in KAlSi_3O_8 feldspar to K_2Si_4O_9 wadeite + Al_2SiO_5 kyanite + SiO_2 coesite (or stishovite) and further to KAlSi_3O_8 hollandite have been determined. Stability field of CaAl_2O_4 calcium ferrite has been examined. The decomposition boundary of CaFeSi_2O_6 clinopyroxene to CaSiO_3 perovskite + Fe_2SiO_4 spinel +SiO_2 stishovite has also been determined. These phase boundaries are of geophysical and geochemical importance in the lower mantle.3. As a related topic, the rutile-alphaPbO_2 transition boundary in TiO_2 has accurately been determined by in situ x-ray diffraction techniques at high pressure and high temperature. This boundary is important for pressure calibration at high temperatures.