一种以压力一维均匀分布为特征的长条形对顶压砧

A strip anvil apparatus with linear uniform pressure distribution

针对圆形端面平面对顶压砧装置中压力梯度大的问题,本文设计了一种长条形端面的平面对顶压砧,相应的封垫也改为长条形.原理分析表明:这种压砧可在沿长条形中心线的狭长区域内产生均匀分布的高压力.本文采用长20 mm宽5 mm长条形端面的硬质合金压砧配合叶腊石封垫进行压力标定,实验结果显示:这种装置可产生10 GPa以上的高压,在长条形中心线上至少12 mm长度范围内的不同位置上产生的压力基本一致,在2.55 GPa压力时测量偏差小于2.0%,在7.7 GPa时测量偏差小于3.6%.这种特点很有利于对细长样品进行精确的高压物性测量.

Bridgman anvil is a useful and effective tool in high-pressure research.However,in this apparatus,the pressure distribution is essentially centrosymmetric.Thus,considerable pressure gradients exist in the gasket and in the sample chamber respectively,and the uniform pressure area is limited.To improve the pressure uniformity in flat face supported anvils,we design a strip face anvil instead of conventional round face anvil and adopt an assortive strip gasket.Principle analysis and a series of pressure calibration experiments are also presented in this paper.The construction of the strip anvil and relevant parts of the apparatus are shown in the diagrams and photos.The relationship between pressure and shearing stress in the strip gasket is investigated by using the model of M.Wakatsuki,which indicates that the pressure distribution should be uniform along the central line of the strip gasket.Pressure calibration experiments are conducted by using strip anvils made of tungsten carbide with a length of 20 mm and width of 5 mm and by using the assortive strip gasket of pyrophyllite.Pressures at different places of the central line are calibrated according to the known phase transitions of bismuth in the same loading process,and the samples are assembled with symmetrical,unsymmerical,and separated local collocations,respectively.Experimental results exhibit that the pressure reaches up to 10 GPa in the central line of the strip gasket,and the pressures are almost equal at least within the range of 12 mm on the central line.The bias errores of oil pressures measured at different places of the central line are all less than 2.0% at 2.55 GPa and 3.6% at 7.7 GPa,indicating only a small pressure gradient along the central line.The main reason for the measuring bias errors lies in the difficulty of the assembly technique.Specifically,the bismuth wire is difficult to adhere to the central line of the anvil during compression.Hence,further improvement of the process is expected in the future.In conclusion,the strip anvil is a unique high-pressure apparatus.The principle analysis and pressure calibration experiments confirm that the pressure is uniform in one-dimensional direction along the central line of the strip anvil.This feature is propitious to the accurate investigation of linear samples under high pressure.