Two molecular aggregates, an enzyme and micelle, in supercritical fluids have been studied with respect to their microstructures and activity for chemical reactions. Ester syntheses catalyzed by a lipase have been carried out in supercritical carbon dioxide. In the near-critical region, the rate showed a sharp maximum and (S) - (-) -terpene esters were stereoselectively synthesized from acyl donors and a primary alcohol. The structure of an enzyme and interactions between carbon dioxide and enzyme molecules have been examined by using in situ FTIR and gravimetry. The alkaline fading of crystal violet (CV) is accelerated by using a W/O microemulsion of H2O/AOT/ethane under supercritical conditions. The structure of AOT molecules and the type of interior water molecules may account for the rate enhancement.
Recent advances in the synthesis of inorganic materials by the solvothermal reactions using high temperature and high pressure aqueous and/or nonaqueous solvents were reviewed. Especially, the formation of monodispersed particles, single crystals and thin films by the solvothermal reactions using metal chelate precursors and/or concentrated gel precursors were introduced. The control of the powder agglomeration using nonaqueous solvents followed by supercritical drying was also introduced.
New intermetallic compounds synthesized under high pressure condition are reviewed. These include borides, silicides, phosphides, chalcogenides, germanides, and antimonides in various transition metal-metalloid systems. The characteristics of high-pressure synthesis are summarized and classified into three typical groups: 1. Pressure-induced phase transitions of ambient pressure phases, 2. Compound formations with new chemical compositions, and 3. Control of decomposition and/or sublimation of reactants. The various examples demonstrate that high-pressure synthesis is a powerful tool for developing new functional materials.
Using a wedge-type cubic anvil high pressure apparatus, metal-IVA and -VA group compounds have systematically been prepared at high temperatures and high pressures. In this paper we mainly report the electrical properties of the compounds with skutterudite (CoAs3-type) structure prepared at high pressure. CoP3 and CeRu4P12 behave as a semiconductor. NiP3 is a metal. LaRu4P12 is a superconductor with Tc of 7 K. The electrical resistivity of alloys La1-xCexRu4P12 rapidly increases with increasing x. The metal to semiconductor transition is observed at around X=0. 6. PrRu4P12 shows the electrical anomaly due to the metal-insulator transition at around 60 K. The Tc's of new superconductors LaRu4As12 and LaRu4Sb12 are 10. 3 K and 2. 8 K, respectively. LaRu4As12 has the highest Tc in the skutterudite compounds. PrRu4As12 is an interesting superconductor containing the magnetic rare earth with Tc of 2. 5 K though PrRu4P12 behaves as the semiconductor below 60 K. We have found the new compound superconductors, ZrRuSi, ZrRuGe, ZrRu4P12, LaRu4As12 and ZrRhSi, with Tc of above 10 K in metal-IVA and -VA group compounds prepared at high pressure.
A new formation control technique of percolated structure of polystyrene-polybutadiene polymer blend was developed by using supercritical (SC) carbon dioxide solution containing organic solvent, such as benzene, toluene, or p-xylene. During the solvent casting process, the SC fluid mixtures which have large diffusivity were used as a solvent for the polymer blend under the conditions of 20 MPa and 308. 15 K. The periodic distance of the percolated structure was measured during the casting process by the laser-light scattering method. And the produced structure of polymer blend was observed by an optical microscope. A closed percolated structure of polymer blend was formed in the SC fluid process.
In this paper we have summarized some of the main research programs carried out on high pressure in France. If more details are required on a specific subject, they can be obtained by writing to the experts working in the concerned field.
Recently, research interest is concentrated on the use of high pressure for food processing and a successful story example is reviewed here. This report introduces various types of high-pressure processed food products, and gives the inside story of the course of this development and processing in our factory. The applicability of high pressure for the development of new foods for the future is also suggested.