采用光谱技术研究[C_(4)mim][BF_(4)]的传压和测压性能

Study on Performances of Transmitting Pressure and Measuring Pressure of[C_(4)mim][BF_(4)]by Using Spectroscopic Techniques

金刚石压腔是一种在实验室被频繁使用的高压产生装置,它在高压领域占据着重要地位。当金刚石压腔内传压介质只能提供非静水压环境时,利用传统的红宝石荧光光谱测压方法将很难准确测量样品压强,这也是目前超高压实验面临的普遍困难。若有一种兼具“传压”和“测压”双重功能的物质,根据“相邻位置、相近压强”原则,将能够解决在非静水压环境中测不准样品压强问题。显然,探寻兼具“传压”和“测压”双重功能的物质是一项非常重要的工作。本文将红宝石微粒与离子液体[C_(4)mim][BF_(4)]装入金刚石压腔,然后利用金刚石压腔压缩[C_(4)mim][BF_(4)]使其提供高压环境,同时采集红宝石的荧光光谱及其附近[C_(4)mim][BF_(4)]的拉曼光谱。通过分析红宝石特征荧光峰R_(1)的峰位,得到了[C_(4)mim][BF_(4)]在加压过程中提供的一系列高压环境的压强值。通过分析红宝石特征荧光峰R_(1)的峰宽,发现[C_(4)mim][BF_(4)]在0~6.26和6.26~21.43 GPa两个压强范围内可分别提供静水压环境和准静水压环境,表明[C_(4)mim][BF_(4)]在0~21.43 GPa范围内可以作为传压介质使用。此外,还发现[C_(4)mim][BF_(4)]在0~2.28,2.28~6.26,6.26~14.39和14.39~21.43 GPa四个压强范围内分别为“液相Ⅰ”、“液相Ⅱ”、“非晶相Ⅰ”和“非晶相Ⅱ”。通过分析[C_(4)mim][BF_(4)]中特征拉曼峰ν(B-F)和ν(ring)的峰位,发现在[C_(4)mim][BF_(4)]四个相态内ν(B-F)和ν(ring)的峰位随压强增加均满足线性变化关系,并给出了相应的压强与峰位关系函数,这些函数是[C_(4)mim][BF_(4)]用作压标物质的重要依据。综上所述,[C_(4)mim][BF_(4)]不仅具有“传压”功能,同时还具有“测压”功能,可同时用作“传压介质”和“压标物质”。研究结果为在非静水压环境中准确测量样品压强提供了重要依据,也为超高压条件下样品压强测量不准确问题提供了新的解决思路。

Diamond anvil cell(DAC)is a kind of high-pressure generator that is frequently used in the laboratory and plays an important role in the field of high-pressure research.When pressure-transmitting medium(PTM)in DAC can just provide non-hydrostatic pressure,it will be difficult to accurately measure the pressure of the sample by using the ruby fluorescence method.The same cases frequently emerge under ultra-high pressure conditions.If there is a material with dual functions of transmitting pressure and measuring pressure,the pressure values of the sample under non-hydrostatic conditions might be measured accurately according to the principle that the closer the positions are,the more similar the pressures are.Apparently,it is important to search for the material with dual functions of transmitting and measuring pressure.In this paper,a ruby particle and a small drop of ionic liquid[C_(4)mim][BF_(4)]were loaded into a DAC,a series of high-pressure environments were provided by compressing the[C_(4)mim][BF_(4)].Simultaneously,the fluorescence spectrum of ruby and the Raman spectrum of[C_(4)mim][BF_(4)]was obtained under high pressures.By analyzing the positions of the R_(1)line of ruby,the pressure values of[C_(4)mim][BF_(4)]were obtained.By analyzing the widths of the R_(1)line of ruby,it was found that the hydrostaticand quasi-hydrostatic pressures provided by[C_(4)mim][BF_(4)]were in the ranges of 0~6.26 and 6.26~21.43 GPa,respectively.It could be speculated that[C_(4)mim][BF_(4)]can use as PTM in the pressure range of 0~21.43 GPa.In addition,[C_(4)mim][BF_(4)]is a liquid phaseⅠ,liquid phaseⅡ,amorphous phase I,and amorphous phase II in the ranges of 0~2.28,2.28~6.26,6.26~14.39,and 14.39~21.43 GPa,respectively.By analyzing the positions ofν(B-F)andν(ring)as the characteristic Raman peaks from[C_(4)mim][BF_(4)],it was found that they followed linear changes with increasing pressure during the above four phases of[C_(4)mim][BF_(4)].What’s more,the formulas of pressure and position ofν(B-F)andν(ring)were given.The formulas are very important for[C_(4)mim][BF_(4)]to be a pressure gauge.To sum up,[C_(4)mim][BF_(4)]has the dual functions of transmitting pressure and measuring pressure and can use simultaneously as the PTM and the pressure gauge.The research results provided an important basis for accurate measurement of sample pressure in non-hydrostatic environments and provide a new solution to the inaccurate measurement of sample pressure under ultra-high pressure conditions.