Recent high pressure experiments on the electrical and magnetic properties of Ce-monopnic-tides are reviewed, which illustrates how the high pressure technique can be used to gain information about the electronic and magnetic state of these compounds. Experiments under pressure up to 8GPa and at low temperature down to 4. 2K were undertaken using a new high pressure apparatus developed originally in our laboratory. The high pressure generation under low temperatures is explained for precise electrical measurements.
The properties of aqueous mixtures containing organic liquids vary uniquely with composition in a manner depending on the nature of the solute molecules; the behavior is responsible for producing several kinds of phase separation and has received much attention in solution chemistry. Information on the phase equilibria of the aqueous mixtures is particularly important in development of industrial separation techniques such as distillation, absorption, extraction, crytallization etc. The purpose of this review is to describe briefly the phase equilibria under high pressure for some cases of aqueous binary and ternary mixtures with organic liquids. Comments are given about the effects of temperature and pressure on the critical solution properties, solubilites, and ability of extraction.
Fine silica particles have been produced by the rapid expansion of supercritical water - SiO2 solutions (RESS) at temperatures of 723 and 823 K and pressures from 50 to 100 MPa. New spherical particles sprouting whiskers have also been discovered in the autoclave after the RESS. The solubility of solids in supercritical fluids is a very sensitive function of temperature and pressure. Small changes of pressure result in large changes in density and solvent power, because supercritical fluids are highly compressible. Thus, the rapid expansion of supercritical solutions can give rise to very large supersaturation ratios. Nucleation rates are determined by the competition among solvent expansion, cooling due to depressurization, and high supersaturation. In order to control the product morphology, the effects of experimental parameters, such as preexpansion temperature and pressure, solute concentration, depressurization schemes, nozzle configuration, and sampling method on the product characteristics of materials, have been investigated by means of scanning electron microscopy and X-ray diffraction analysis. It is found that the control of particle size distribution is possible by regulating supersaturation ratio as well as suitable selection of preexpansion temperature and pressure. Unique features of the RESS process are discussed.
The method of high pressure processing have been introduced in processing, preservation, and sterillization of food during these six years in Japan to produce high quality food of natural taste and flavor. This article describes the present status of research and development of this new trend. Especially, the necessity of high pressure bioscience is stressed for further development of this new philosophy to achieve the industrial success.
Recent progress in the theoretical study on the structure of liquid metals under high temperature and high pressure is reviewed. In particular, the density dependence of the static and dynamical structure of expanded liquid alkali metals along the liquid-vapour coexistence curve from the melting point to the critical point is investigated by the recent reliable integral equation theory. The theory can reproduce well the characteristic features of the structure of expanded liquid alkali metals obtained experimentally. The temperature dependence of the structure of liquid alkali metals along the isocore line is also investigated.
The experimental apparatus for measuring the PVT-data, electrical and optical properties of expanded fluid mercury near the liquid-gas critical point are reviewed. By using these apparatus, the equation-of-state, optical absorption spectrum, thermopower data can be obtained accurately over the wide temperature and pressure range. In fluid mercury the metal-non-metal transition occurs near the density of 9 g/cm3 and the thermopower has a considerably large negative value in the vicinity of the critical point. The optical data for fluid iodine and chalcogen mixture are also included.
In this paper we describe the experimental techniques, the method of data analysis and the results of our recent structural studies for expanded fluid Hg. The energy-dispersive x-ray diffraction measurements were carried out for the first time in the density range from 13. 55 to 6. 8 gcm-3 including the metal-nonmetal transition region. For the measurements we have developed a single-crystalline sapphire cell and a high-pressure vessel of our own design and improved the method of the data analysis. It was found that the volume expansion of liquid Hg in the metallic region, to the density of about 10gcm-3, is not accompanied by a uniform increase of interatomic distance r1 but mainly caused by a decrease of the coordination number N1- When the transition region is approached, the decrease of N1 becomes rather small and r1 starts to elongate.
Recent development on the structural study of liquids under high pressure is reviewed. Using x-rays from synchrotron radiation with high energy and high brightness, x-ray diffraction measurements have been successfully performed for various liquids. The pressure-induced structural changes in liquid Cs, liquid Ga, liquid Bi, liquid Se and liquid Te are discussed in relation to the changes in the electronic structures. Pressure-induced phase transitions in liquids are also discussed.
Higher pressure was obtained by hollowing out the anvil top of a cubic anvil under the condition that the distance between the anvil tops is equal to that of the cubic anvil. The total length of the gasket which influences the intensity of the diffracted beam in the X - ray experiment was decreased in the new type of anvil.