Ultra-high pressure investigations

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). 

A/xjkT. In recent investigations on cut stones, an example showing, for the first time, the presence of a seed in the crystal growth of natural diamonds has been discovered [18]. It is also the first example to show the relation between diamonds formed by ultra-high-pressure metamorphic rocks and those formed in ultramafic magma. 

Preparation process and microstructure investigation of the novel C/C-ZrB -ZrC-SiC have been reported in the previous chapter The composite contained a 2D carbon fiber non-woven architecture with fiber volume fraction of 17.6%, with pyrolytic carbon deposited on carbon fiber by CVI as interphase with a volume fraction of 22.3%. The obtained porous C/C composite exhibited a bulk density of 0.68g/cm, 50 vol% ZrB2-ZrC-SiC matrix and 9.6 vol% open porosity. The homogeneous dispersed ZrB2-ZrC-SiC complex ceramic matrix was formed inside this porous C/C composites by PIP technique using a blending ZrB -ZrC-SiC pre-ceramic polymeric precursors solution in xylene. The finial bulk density of the fabricated composite is 2.06 g/cm (details were reported in Part 1) after 16 PIP cycles. Finther densi-fication was difficult because of limitation of low residual porosity and ceramic yields from these precursors. PIP under ultra high pressure may further decrease the residual porosity of the composite but this was not conducted in this study due to the lack of this device. 

However, investigations up to now have mainly concentrated themselves on ambient environments even though it is known that ionic liquids have a very low vapor pressure, making them suitable for vacuum applications such as in space mechanisms, the disk drive industry, and microelec-tromechanical systems (MEMS). Due to the ultra-low vapor pressure of most ionic liquids, they have been expected to be good lubricants in vacuum. Further experimental works are required to evaluate lubrication behavior of ionic liquids under ultra-high vacuum conditions and in inert atmospheres. 

Remane D, Meyer MR, Wissenbach DK, Maurer HH (2010) Ion suppression and enhancement effects of co-eluting analytes in multi-analyte approaches systematic investigation using ultra-high-performance liquid chromatography/mass spectrometry with atmospheric-pressure chemical ionization or electrospray ionization. Rapid Commun Mass Spectrom 24(21) 3103— 3108. doi 10.1002/rcm.4736... 

Self-assembly phenomena on solid substrates are usually studied in ultra-high vacuum (UHV) or at the liquid-solid interface. Surface analytical methods involving electrons require vacuum. But UHV has also the advantage that reactive metal and metal oxide surfaces can be used as substrate since the very low background pressure also guarantees long investigation times on a non-altered sample. 

In principle, two approaches can be adopted for fundamental investigations of the relations between catalytic properties on one hand, and catalyst composition and structure on the other. The first is to model the catalytic surface, for example with that of a single crystal. By using the appropriate combination of surface spectroscopies, the desired characterization on the atomic scale is certainly possible in favourable cases. The disadvantage, however, is that although one may be able to study the catalytic properties of such samples under realistic conditions (pressures of 1 atm or higher), most of the characterization is necessarily carried out in ultra high vacuum, and not under reaction conditions. 

The experimental setups and procedures for using XPS [25] (Fig. lb), TPD [26] and cyclic voltammetry [27] under ultra-high-vacuum (uhv) conditions and work function measurements [7,27], cyclic voltammetry [26,28] and STM [29] under atmospheric pressure conditions to investigate the origin of electrochemical promotion, have been described in detail recently [25-29]. 

The thermal decomposition of single-crystal and powder samples of KN3, in an ultra-high-vacuum environment, has been studied. Mass spectrographic detection was used to monitor the decomposition products, and, from the temperature dependence of the partial pressure of nitrogen, three decomposition regions were found. Azide radicals and potassium atoms were also detected. The application of an electric field across the sample during decomposition was investigated, and models for the decomposition process were discussed. ... 

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