基于PE型压机中子衍射高温高压组装的优化设计与实验验证

Optimal design and experimental verification of hightemperature and high-pressure assembly of neutron diffraction based on PE-type press

高温高压原位中子衍射探测手段对凝聚态物理、晶体化学、地球物理以及材料科学与工程等领域的研究均有重要的意义.本文基于中国绵阳研究堆(China Mianyang Research Reactor, CMRR)的高压中子衍射谱仪(凤凰)和1500 kN的PE型两面顶压机,设计了一套应用于高温高压原位中子衍射实验的组装,并利用中子衍射技术进行了实验验证及温度、压力标定.通过对组装在高温高压下的流变控制、绝热绝缘性能提高、有效样品体积最大化等方面的优化,获得了11.4 GPa, 1773 K高温高压条件下的中子衍射谱.该组装的成功研制使CMRR高温高压中子衍射平台的指标得到明显提升.同时,对进一步提高PE型两面顶压机高温高压加载条件、扩展PE型压机在高温高压原位中子衍射领域的的应用范围,具有重要的意义.

High-pressure and high-temperature(high-P-T)in-situ neutron diffraction detection method is a field of growing interest,in particular,for its numerous applications in the field of condensed matter physics,crystal chemistry,geophysics,materials science and engineering.In this work,we design and optimize a set of assembly for high-P-T in-situ neutron diffraction experiment in neutron source of China by using Paris-Edinburgh(PE)-type press.The high-P-T experiment is carried out with a high-pressure neutron diffraction spectrometer(Phoenix)of China Mianyang Research Reactor(CMRR).A 1500 KN uniaxial loading system and a 1500 W constant current source provides extreme conditions of high-P-T for PE press.The toroidal anvil we use is made of tungsten carbide.We use two types of gaskets:one is machined from the null-scattering TiZr alloy and the other is made from the thermal insulation ceramic material of ZrO2.High-temperature furnace is formed by graphite.First,a simplified simulation analyses of the pressure change rates in different areas of the entire assembly are carried out,and it is concluded that the gasket I,II,III areas are designed with a gradient decreasing method.The compression ratio of the sample chamber is significantly improved.Then when the gasket reaches the same compression ratio,the cell pressure will be higher than the pressure before optimization.After that,we conduct experimental verification on the optimized design.Through a series of optimization experiments for assembly on the rheological control of gasket,the improvement of thermal insulation performance and the maximization of effective sample volume under high-P-T,the key technical indicators and design scheme of the high-P-T in-situ neutron diffraction platform are verified.The temperature and pressure in the sample cavity are calibrated by using the MgO's high-P-T in-situ neutron diffraction spectrum and equation of state.The in-situ neutron diffraction sample cavity environment of the designed platform can reach the conditions of 11.4 GPa and 1773 K.The successful development of this assembly greatly improves the experimental conditions of CMRR high-P-T neutron diffraction platform.At the same time,it has important reference significance for further improving the high-P-T loading conditions of the PE-type press and expanding the application scope of the PE-type press.