Generation of negative pressure through Berthelot method and measurements of properties of super-expanded liquid states under negative pressure

金属管Berthelot法是一种热力学方法，通过温度循环对密封在金属管中的液体产生负压，在适当的温度范围内对系统进行第一次加热和随后的冷却。我们过去的工作集中在一种调节方法上，即在单晶钼管中将水和有机物的负压提高到-150bar。在本工作中，我们研究了1)CMSX-4镍基高温合金单晶管通过预脱气获得了-120bar量级的负压，并在经过9次除气水刷新的温度循环之后。2)在管内密封了液晶PMPEB，并测量了在不同样品密度密封条件下的压力-温度关系。结果是：2)绘制了该向列型液晶的P-T相图，2-2)在…下观察到了其各向同性液晶-向列型相变较大的负压，2-3)多晶性，即熔点分别为37.41和46℃的三种晶型，以及2-4)两种晶体之间的一级相变。Berthelot方法的大部分数据与我们在1bar下的DSC数据一致，这些结果表明，Bethelot方法适用于研究从正压到负压范围内有机物热力学性质的压力依赖关系。特别是结果2-2)对有机超膨胀凝聚相热力学的发展具有重要意义。我们还表明，3)Berthelot方法可以检测金属管内与液体一起密封的固体的10^&lt；-7&gt；cc量级的小体积变化。介孔中的硅、介孔硅酸盐和吸附气体分子在水中的溶解被检测为填充温度的降低，其中填充温度是Berthelot系统的特征温度，在该温度下，管子的整个体积在加热过程中被凝聚相完全占据。较少

Metal tube Berthelot method is a thermodynamic means for generating negative pressure for a liquid sealed in a metal tube by a temperature cycle, first heating and subsequent cooling of the system over an appropriate temperature range. Our past work has been concentrated on a conditioning approach by which negative pressure is raised to-150 bar for water and organics in a single-crystalline Mo tube. Unfortunately, the tube was corroded slowly.In the present work we investigate 1)CMSX-4,Ni-based super-alloy single crystalline tube has achieved negative pressure of the order of-120 bar by pre-degassing the tube, and after runs of temperature cycles with 9 times refreshing of de-aerated water.2)A liquid crystal, PMPEB, is sealed in the tube and its pressure versus temperature relations are measured at various sample-density sealing conditions. The results are 2-1)P-T phase diagram of this nematic liquid crystal is drawn, 2-2)its isotropic liquid-nematic phase transition is observed under … More negative pressure, 2-3)poly-morphism, that is, three crystalline forms having melting points of 37.41, and 46℃, respectively, are found and 2-4)a first-order phase transition between two of the crystals. Most of the Berthelot method data are consistent with our DSC data done at 1 bar.These results demonstrate that Bethelot method is applicable to investigate pressure dependence of thermodynamic properties of organics from positive to negative pressure ranges. In particular, the result 2-2)is of importance in development of thermodynamics of super-expanded condensed phases of organics.We also show that 3)Berthelot method can detect small volume changes of the order of 10^<-7> cc of solids that are sealed together with a liquid in the metal tube. Dissolutions of Si, mesoporous silicate, and adsorbed gas molecules in the mesopores into water are detected as lowerings of temperature of filling, where the temperature of filling is a characteristic temperature of a Berthelot system at which the whole volume of the tube is completely occupied by the condensed phases alone during its heating. Less