High pressure investigations

High-Pressure Investigations of Magnetic Properties (Examples Laves Phases and Iron Oxides)... 

Fourier-transform infrared (FT-IR) spectroscopy and small-angle X-ray (SAXS) and neutron (SANS) scattering studies have shown the existence of a further pressure induced gel phase in DPPC bilayers." " Pressure dependent NMR studies yielded complementary information on the pressure-induced gel phases. The gel state of DPPC bilayers shows a variation in lineshapes which depend on the particular pressure and temperature. The types of lineshapes seen in a high pressure investigation of dg2-DPPC by Jonas et al. are... 

High-pressure investigations led to reports of over twelve new phases by Vezzoli (116, 117), Ward (119), Susse (111), and Pankov (78). In evaluating this work it should be known that equilibria are established very slowly, especially at high temperatures where viscous species are produced. Block (9) reported that above 235°C equilibrium is not nearly reached after 3 days. Thus the properties of samples reflect their history. 

The mechanism of guest complexation by a-cyclodextrin was studied by high-pressure investigations. The first volume profiles obtained for azo dyes 1-4 (Figure 4) are presented as a new approach in understanding inclusion phenomena. 

High-Pressure Investigations on the Solubility of Synthetic and Natural Dyestuffs in Supercritical Gases by VIS-Spectroscopy up to 180 MPa... 

Fig. 33. Polarized emission spectra of single-crystal Ba[Pt(CN)4] 4 H20 at different hydrostatic pressures (T = 295 K)133). The emission intensities at different pressures cannot be compared. The excitation wavelength was varied with pressure to fit approximately the maximum of the E c polarized reflectance. For the high pressure investigations a modified sapphire cell of Bridgman s opposed anvil type was used. The pressure was determined by the amount of red-shift of the Rt- and R2-lines167) of ruby crystals placed around the sample...

Infrared and Raman studies at very high pressure (up to several hundred kbar) are carried out fairly routinely with diamond anvil cells (DAC). The DAC, which was first developed for high-pressure infrared absorption measurements by Weir et al. (1959) and for X-ray studies by Jamieson et al. (1959), has become a very powerful tool for a wide variety of ultra-high pressure investigations, with particularly important applications in solid state physics. The potential of the method has increased enormously with the introduction of gaskets into the DAC by Van Valkenburg (see Jayaraman, 1983) and with the possibility of pressure calibration by the ruby fluore.scence method (Forman et al, 1972). 

This section is a summary of recent high-pressure investigations of model catalysts. The focus is on vibrational spectroscopy but, when data are available. 

Figure 8 Illustration of the scanning transitiometry technique for low-temperature, high-pressure investigation of polymers glass transition. The pressure coefficient of the glass transition temperature is given in the inset...

Schneider, G.M. High-pressure investigations on fluid systems — a challenge to experiment, theory, and application. J. Chem. Thermo. 1991, 23, 301-326. 

Tutna, D. Schneider G.M. High Pressure Investigations on the Solubility of Disperse Dyes in Near- and Supercritical Fluids Measurements up to 100 Mpa by a static Method" The 4 International Symposium on Supercritical Fluids 1997. 

Recently, a high-pressure investigation of CaSi2 in a diamond anvil cell has been published. Nitrogen was used as a pressure-transmitting material and the diamond anvil cell was calibrated by the ruby luminescence method. 

High-pressure investigations have yielded important insights into the structural, chemical, and physical properties of clathrate materials, as well as their stability [122-124]. From a synthetic standpoint, high-pressure techniques often allow... 

Schneider, G.M. (1998) High-pressure investigations of fluid mixtures — Review and recent residts, J. Supercrit. Fluids 13, 5-14. 

Haarhaus, U., Swidersky, P., and Schneider, G.M. (1995) High-pressure investigations on the solubility of dispersion dyestuffs in supercritical gases by VIS/NIR-spectroscopy. Part I — l,4-Bis-(octadecylamino)-9,10-anthraquinone and Disperse Orange in CO2 and N2O up to 180 MPa, J. Supercrit. Fluids 8, 100-106. 

Tuma, D. (1999), Spectroscopic high-pressure investigations in near and supercritical fluids up to 180 MPa — Solubility and stability of anthraquinone dyestuff s and /3-Carotene in CO2, N2O, CCIF3, and SFe (in German), Doctoral dissertation, University of Bochum, Germany. 

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