High-pressure Inclusion

An important application of the HMT is the test for ferrous inclusions in high pressure turbine disks made from a non-magnetic metal alloy. On principle, such ferrous inclusions can be introduced during the manufacturing process and, if present, they can be the origin of cracks in these most critical parts. Therefore such tests are stringent necessary. 

Since the demonstration by Schumacher et al ) of the use of alkali metal vapor inclusion into a supersonic beam to produce clusters, there have been a number of attempts to generalize the approach. It has recently been recognized that instead of high temperature ovens, with their concommitant set of complex experimental problems, an intense pulsed laser beam focused on a target could be effectively used to produce metal atoms in the throat of a supersonic expansion valve. ) If these atoms are injected into a high pressure inert gas, such as helium, nucleation to produce clusters occurs. This development has as its most important result that clusters of virtually any material now can be produced and studied with relative ease. 

Ammonium nitrate (AN) was considered early as an environment-friendly alternative to AP but its multiple crystal phase-transitions at low temperatures and its poor performance precluded its use. The nitramine-based propellants are also likely to emerge as potential eco-friendly propellants as the combustion products are non-toxic and non-smoky, although the present day nitramine propellants do not match the high performance and high burn rates of AP-based composite propellants [62, 63]. At the same time, high pressure exponent and unstable combustion prevent their application in large rockets due to safety considerations [20]. The inclusion of Al powder and other additives increases the burn rate and also eliminates the combustion instability. 

Irradiation of powdered 1 2 inclusion complex of 1 and chalcone 2 by a high-pressure Hg-lamp at room temperature for 1 h gave a single photoaddition product syn-head-to-tail dimer 3a in 82% yield. 

A powdered 1 2 inclusion complex of 1 and 2 was irradiated by 400-W high-pressure Hg-lamp for 6 h at room temperature. The reaction mixture was recrystallized from MeOH to give [4+4] dimer 3. 

A powdered 1 1 inclusion complex of (-)-l and 4-methoxy-l-methylpyridone 2c was irradiated by 100-W high-pressure Hg-lamp at room temperature in the solid state. The crude reaction product was chromatographed on silica gel using CHCI3 as a solvent to give a mixture of host compound and 3, from which 3 was isolated by distillation as an oil ([a]D-123° (c 0.026, CHC13), 100% ee). 

A suspension of powdered 1 1 inclusion complex of (-)-la and 2a (3.07 g, 4.41 mmol) in water (120 mL) containing hexadecyltrimethylammonium bromide (0.1 g) as a surfactant was irradiated under stilling for 16 h with 100-W high-pressure Hg-lamp. The reaction mixture was filtered, dried and chromatographed on silica gel using AcOEt-toluene (1 9) as an eluent to give (+)-3a of 97% ee after distillation at 180°C/2mmHg as colorless oil. 

The enantioselective photodimerization of thiocoumarin (102) to optically pure (+)-a ft -head-to-head dimer (103) in the 1 1 inclusion complex of 102 with 12b was also found to proceed in a single-crystal to single-crystal manner. For example, when a mixture of thiocoumarin (102) and optically active host compound 12b in butyl ether was kept at room temperature for 12 hr, a 1 1 inclusion complex of 103 with 12b was obtained as colorless needles. Photoirradiation of a 1 1 inclusion complex in the solid state (400-W high-pressure Hg lamp, Pyrex filter, room temperature, 2 hr) gave a 2 1 complex of 12b with 103,... 

The robust, well-shielded cavity found in hemicarcerands offers tremendous scope for the use of these hosts as micro-reaction vessels in order to protect reactive species from bimolecular decomposition by isolating them from the outside medium. Furthermore, the unique intracavity environment with its fluid-like properties in which guest species are, formally, in a very condensed state at very high pressures, may well result in unique inclusion reactivity. Indeed, the inner volume of carcerands and hemicarcerands has been described as a new phase of matter distinct from solid, liquid and gas. A number of elegant demonstrations have been made of the potential of inclusion reactions, and there is clearly a great deal of scope for their use as molecular reaction vessels. 

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. 

Abou-Hamdan, A. Bugnon, P. Saudan, Ch. Lye, P.G. and Merbach, A.E. (2000) High-Pressure Studies as a Novel Approach in Determining Inclusion Mechanisms Thermodynamics and Kinetics of the Host-Guest Interactions for a-Cyclodextrin Complexes, J. Am. Chem. Soc. 122, 592-602. 

Clifford 2000). Many metallic ore and evaporite minerals contain methane, though not in hydrate form. For instance, the Red Dog zinc ores mentioned above contain methane inclusions in association with saline inclusions. In many instances, microscopic methane and carbon-dioxide-rich fluid inclusions form clathrates within their tiny hydrous envelopes. Some salt deposits are so enriched in high-pressure free gas inclusions and/or gas hydrates that mining, crushing under boot, or other means of physical disturbance causes popping or even explosive decrepitation. 

The second provenance criterion is based on the identification of inclusions in gemstones. Micro-Raman spectrometry was used for this task in almandine garnets. Various inclusions were observed like apatite, zircon, monazite, calcite, and quartz and two of them, curved needles of sillimanite (Al2Si05) and 10-pm metamict radioactive crystals, were specifically found in archaeological garnets. Fig. 6 shows the Raman spectra of a sillimanite needle, which is a mineral formed under a high temperature and high pressure metamorphism. 

Figure 6. Raman spectrum of a sillimanite elongated and curved inclusion indicating a high Pressure-Temperature metamorphism of the crystal...

---