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中国物理学会期刊

基于巴黎-爱丁堡压机的高压中子衍射技术

High-pressure neutron diffraction techniques based on Paris-Edingburgh press

CSTR: 32037.14.aps.68.20190179
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  • 巴黎-爱丁堡压机(Paris-Edinburgh press)可配合中子衍射对物质在高压下的结构变化进行研究. 自20世纪90年代开始, 已在材料学、地学、化学等众多领域得到了广泛应用. 本研究利用巴黎-爱丁堡压机在中国绵阳研究堆(CMRR)的高压中子衍射谱仪(凤凰)上成功开展了高压中子衍射实验. 实验由一台载荷为200 MPa的单缸柱塞泵为巴黎-爱丁堡压机提供加载压力, 并发展了一套与谱仪集成的自动定位系统对样品进行定位. 利用铁作为样品, 分别使用单凹曲面和双凹曲面两种碳化钨(WC)压砧, 成功获得了约10 GPa压力范围内的高压原位中子衍射谱. 实验结果显示, 双凹曲面组装可以稳定地承受100 MPa的负载压力, 而单凹曲面封垫在80 MPa左右的负载压力下就开始不稳定而发生放炮. 研究结果表明, 双凹曲面压砧的凹槽增强了封垫的侧向支撑能力, 使双凹曲面组装比单凹曲面组装具有更好的稳定性. 研究结果对进一步优化巴黎-爱丁堡压机的压砧及封垫具有重要的指导意义.

     

    Since the 1990s, with the benefit of available large-volumed samples, wide detector windows, and portability, Paris-Edinburgh press has been widely used in neutron facilities to study the structures and physical properties of condensed matter under high-pressure extreme conditions. In the present study, We perform high-pressure neutron diffraction experiments in neutron source of China using the Paris-Edinburgh press. The experiments are carried out on a high-pressure neutron diffraction spectrometer (Fenghuang) at China Mianyang Research Reactor (CMRR). Fenghuang is a high-intensity and moderate-resolution diffractometer which has been upgraded from a neutron powder diffractometer and can be used under ambient and extreme conditions. A single cylinder pump with a max load of 200 MPa provides a loading pressure for Paris-Edinburgh press, and a precise mobile platform is used to hang and to locate the Paris-Edinburgh press. Using the tungsten-carbide (WC) toroidal anvils with TiZr gasket, we obtain the neutron diffraction spectra of Fe samples at different pressures successfully. We also obtain the neutron diffraction spectra respectively at pressures of 9.7 GPa and 10.7 GPa by using a WC single-toroidal anvil and a WC double-toroidal anvil under load 100 MPa. The TiZr gasket blows out before the load reaches 100 MPa in the WC single-toroidal anvil assembly, while it remains good in the WC double-toroidal anvil assembly under the same load. The WC single-toroidal anvil assembly becomes unstable under load about 80 MPa, and the WC double-toroidal anvil assembly is still stable under load 100 MPa. Thus, the stability of the double-toroidal anvil assembly is much higher than that of the single-toroidal anvil assembly. It is found that the thickness of the gasket edge is very important for the stability of the assembly during loading. The thicker the edge of the gasket, the more stable the assembly is. The main reason is that the groove of the double concave anvil can enhance the lateral support ability of the gasket, thereby making the double concave surface assembly more stable than the single concave surface assembly.

     

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