Determination of thermal diffusivities, thermal conductivities, and sound speeds of room-temperature ionic liquids by the transient grating technique
Determination of thermal diffusivities, thermal conductivities, and sound speeds of room-temperature ionic liquids by the transient grating technique
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DOI：
10.1021/je0600092
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发表时间：
2006-07-13
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影响因子：
--
通讯作者：
Yu, Shaofang
中科院分区：
文献类型：
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作者：
Frez, Clifford;Diebold, Gerald J.;Yu, Shaofang
本文报道了用瞬态光栅法测量几种室温离子液体的热扩散率。使用离子液体与小浓度的惰性染料进行测量，所述惰性染料由Nd：YAG激光器的532 nm输出在具有（92和104）Am的条纹间距的光栅中激发。实验给出了热扩散系数，从中可以确定热导率，声速，和七种离子液体的声阻尼参数。在这项研究中，我们使用了阳离子1-丁基-3-甲基咪唑的组合（[BMIm]（+））与四氟硼酸根（[BF 4]（-））、六氟磷酸根（[PF 6]（-））和双（三氟甲基磺酰基）酰亚胺（[Tf 2N]-）和阴离子[Tf 2N]（-）与阳离子1-乙基-3-甲基咪唑鎓的组合（[EMIm]（+））、1-戊基-3-甲基咪唑鎓（[PMIm]（+））、1-己基-3-甲基咪唑鎓（[HMIm]（+））和1-辛基-3-甲基咪唑鎓（[OMIm]（+））以确定阴离子和阳离子对RTIL的热物理性质的影响。结果表明，负离子不仅对声速，而且对热扩散率和声阻尼的RTIL施加强烈的影响。对于具有相同阳离子[BMIm]（+）的RTIL，将阴离子从[BF 4]（-）改变为[PF 6]（-）或[Tf 2N]（-）导致声速、热扩散率和热导率的降低。然而，阳离子的大小并不显著影响声速或RTIL的热扩散率。
We report measurements of thermal diffusivity of several room-temperature ionic liquids (RTILs) using the transient grating method. Measurements are carried out using ionic liquids with small concentrations of an inert dye that is excited by the 532 nm output of a Nd:YAG laser in a grating with a fringe spacings of (92 and 104) Am. The experiments give thermal diffusivities from which thermal conductivities can be determined, sound speeds, and acoustic damping parameters for seven ionic liquids. In this study, we have used combinations of the cation 1-butyl-3-methylimidazolium ([BMIm](+)) with the anions tetrafluoroborate ([BF4](-)), hexafluorophosphate ([PF6](-)), and bis(trifluoromethylsulfonyl) imide ([Tf2N]-) and combinations of the anion [Tf2N](-) with the cations 1-ethyl-3- methylimidazolium ([EMIm](+)), 1-pentyl-3-methylimidazolium ([PMIm](+)), 1-hexyl-3-methylimidazolium ([HMIm](+)), and 1-octyl-3-methylimidazolium ([OMIm](+)) to determine the effect of anion and cation on the thermophysical properties of the RTILs. Results obtained indicate that the anion exerts a strong influence not only on the sound speed but also on the thermal diffusivity and acoustic damping of the RTILs. For RTILs with the same cation [BMIm](+), changing the anion from [BF4](-) to either [PF6](-) or [Tf2N](-) leads to decreases in the sound speed, thermal diffusivity, and thermal conductivity. The size of the cation, however, does not significantly influence the sound speed or the thermal diffusivity of the RTILs.