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The compression behaviors of [delta]-AlOOH and [delta]-AlOOD were investigated under quasi-hydrostatic conditions at pressures up to 63.5 and 34.9 GPa, respectively, using results from synchrotron X-ray diffraction experiments conducted at ambient temperature. Because of the geometric isotope effect, at ambient pressure, the a and b axes of [delta]-AlOOD, which define the plane in which the hydrogen bond lies, are longer than those of [delta]-AOOH. Under increasing pressure, the a and b axes of [delta]-AlOOH stiffen at 10 GPa, although the c axis shows no marked change. Identical behavior was found in [delta]-AlOOD, but the change in compressibility was observed at a slightly higher pressure of 12 GPa. Axial ratios a/c and b/c first decrease rapidly with increasing pressure, then begin to increase at pressures > 10 GPa in [delta]-AlOOH and > 12 GPa in [delta]-AlOOD. At these pressures, the pressure dependence of a/b also changes from increasing to decreasing. The unit-cell volumes of [delta]-AlOOH and [delta]-AlOOD become slightly less compressible at high pressures. Assuming [K'.sub.0] = 4, the calculated bulk moduli of [delta]-AlOOH below and above 10 GPa are 152(2) and 219(3) GPa, respectively. Those of [delta]-AlOOD below and above 12 GPa are 151 (1) and 207(2) GPa, respectively. Keywords: [delta]-AlOOH, [delta]-AlOOD, hydrogen bond, symmetrization, high pressure, isotope effect

Ultrafine-grained (0.2–0.3 µm) WC–Ni hardmetals with a low Ni content (3–5 wt%) were developed using new production techniques based on adding an appropriate amount of VC and Cr3C2,combined with the strong mixing of raw materials. Their uniaxial compressibility was subsequently compared with that of existing WC–Ni and WC–Co hardmetals to assess their suitability for use as anvils in various high pressure experiments, particularly those associated with neutron or magnetic studies. The ultimate compressive strength of the newly developed hardmetals was over 7.7 GPa, which was higher by 1.2 GPa than that of the existing WC–Ni hardmetal ‘MF10’. When these hardmetals were used as anvils, a pressure of approximately 16 GPa was generated using a Paris-Edinburgh-type apparatus with φ8 mm culet, thereby proving that they can allow the physical properties of various materials to be measured at higher pressures than is possible with existing hardmetals. [ABSTRACT FROM AUTHOR]

X-ray radiography was applied to observe the segregation process of iron from silicate at high pressure and high temperature in mixtures containing light elements. As the temperature of the hydrogen-containing sample increases, the molten iron becomes coherent. Small droplets of iron sink to the bottom of the chamber, where they merge into a single, large droplet. The small iron droplets exhibit complex motion, moving in random directions. Markedly different behavior is found in the sulfur-containing sample, where no clear motion of the molten iron is observed. Instead, as the sample temperature is increased, the concentration of iron near the wall of the sample chamber gradually increases. These observations demonstrate that the behavior of molten iron changes according to the dissolved elements. This X-ray radiography experiment represents a powerful technique to study the segregation process of molten iron from solid or partially molten silicate, particularly when combined with high-resolution tomography techniques. [ABSTRACT FROM AUTHOR]

Three kinds of ceramics, zirconia-toughened alumina (ZTA), alumina-toughened zirconia (ATZ) and yttria-stabilized zirconia (YSZ), were tested as anvil materials, mainly for the purpose of neutron scattering study under high pressure. ZTA with non-toroidal anvil profile, having the same sample volume as conventionally used double toroidal anvils, sustained pressures up to 11.9 GPa. This is comparable to anvils made of tungsten carbide (TC) with Ni binder with the same dimensions. ATZ would also be an alternative material to TC with pressure performance comparable to ZTA, whereas YSZ is much weaker than the other two ceramics. The attenuation coefficient for YSZ is significantly smaller than that of TC and similar to ZTA and ATZ, the latter being estimated by attenuation calculations. Neutron diffraction on a sample of lead in YSZ anvils as well as quasi-elastic neutron scattering on liquid water in ZTA also demonstrate the outstanding neutron transparency of these ceramics. The gain factor in count rate is up to one order of magnitude. [ABSTRACT FROM AUTHOR]

We designed new anvil assemblies for acquiring high-quality neutron diffraction data and ruby fluorescence spectra inside a sample chamber. The conical aperture of Ni-binded WC anvils was expanded by a factor of two. A hybrid gasket made of TiZr- and Al-alloy was developed to prevent outward extrusion. A small and optically transparent window of moissanite was introduced to allow for the determination of pressure and hydrostaticity by measurement of ruby fluorescence spectra. High pressure-generation tests that make use of Bi electrical conductivity and ruby pressure markers revealed that pressure could be determined over 10 GPa. In situ synchrotron X-ray diffraction experiments were also carried out using NaCl as the pressure calibrants. The maximum pressure achieved was approximately 13 GPa. The neutron diffraction intensity from the newly generated anvil assemblies was 2.5–3.0 times greater than that using the standard toroidal anvil assemblies used previously. [ABSTRACT FROM PUBLISHER]

A new opposed-anvil high pressure and temperature apparatus was developed based on the Drickamer-type apparatus. Various improvements were made to increase the sample volume and to generate high pressure and temperature stably and easily. By optimizing components such as the anvil, heater, and gasket, large sample volumes of about 4?mm3 (?103 times more than that previously obtained with our previous apparatus) were achieved, with compact and light apparatus (outer diameter ? 40?mm; height 31?mm; weight 300?g). Pressures and temperatures up to about 15?GPa and 1700?K can routinely and stably be achieved by using this assembly. In order to extend the pressure range further, sintered diamond was used as an anvil material. As a result, pressures and temperatures of around 38?GPa and 1400?K were achieved, although the sample volume was decreased to about 1.3×10?1?mm3. [ABSTRACT FROM PUBLISHER]

A method was proposed for measuring infrared absorption spectra at high pressure under quasi-hydrostatic pressure conditions. Two KBr micro-pellets were prepared as samples, and reference materials were charged in a diamond anvil cell, applying helium as the pressure-transmitting medium. Using this method, the quasi-hydrostatic pressure condition was retained up to approximately 20 GPa. Furthermore, hydrostaticity was much better than conventional pressure-transmitting media used for infrared spectroscopy. Infrared absorption spectra of α -FeOOH at high pressure were measured using the KBr micro-pellet method with a helium pressure-transmitting medium. Downshift of the OH stretching vibration was observed with increasing pressure. Use of the KBr micro-pellet method for infrared absorption spectroscopy at high pressure is a complementary experimental technique to neutron diffraction at high pressure for studying the pressure response of hydrogen bonds. [ABSTRACT FROM AUTHOR]