High-pressure chamber

The apparatus used to contact the heavy petroleum liquids with supercritical fluid and for contacting the vaporized materials with molecular sieves is shown in Figure 2. The high pressure chamber is a one-gallon autoclave with a packless magnetically-driven stirrer, manufactured by Autoclave Engineers, Inc. 

In me experiments, a GNF or SWNT sample with a mass of about 60 mg was placed in a high-pressure chamber and saturated with hydrogen obtained by thermal decomposition of A1H3. The sample was held under a hydrogen pressure of 9 GPa first for 18 h at t = 350°C and then for another 6 h at 450°C. At the end of holding, me chamber was cooled to -140°C and unloaded to atmospheric pressure at mis temperature. Then, me hydrogen-saturated material was taken out from the chamber and further held in liquid nitrogen. 

Figure 1. High pressure chamber 1-body, 2-window, 3-shutter, 4- bellows, 5-cap, 6-thermocouple.

The solid material is placed into a small vial that is introduced into a thermostated high-pressure chamber (volume 79 ml). The vial is attached to a suspension device that is magnetically coupled to the balance during measurement. The device is lowered to a neutral position when no recording of a mass point takes place, thus allowing for the balance to be tared before each measurement. This is of particular importance in slow processes in which thermodynamic equilibrium is attained only in the course of several hours or even days. The chamber may be evacuated with a vacuum pump at the beginning and at the end of each experiment. The dense gas is taken from a cylinder and, if necessary, compressed to system pressure with the help of a membrane piston pump. 

The sample is filled into the vial which then is attached to the suspension device. Then the high-pressure chamber is firmly closed and heated or cooled to system temperature. More of the sample material is placed within the view cell. The apparatus then is evacuated to remove air and to obtain a reliable value for initial mass. The thermostated dense gas is charged into the chamber and the view cell until system pressure is attained. Pressure build-up only takes a few seconds because of the small volume of the chamber. The weight of the sample rises as gas dissolves in or is being adsorbed to the sample and assymptotically nears its equilibrium value. At the same time, the dissolution of the gas in the solid leads to volume changes, a process observed with the sample particles enclosed in the view cell. Their size is recorded with the camera and evaluated with the help of a PC. The apparatus is evacuated again at the end of each experiment to remove the entire gas. 

Screw-presses by other manufacturers employ different means to facilitate feeding the high-pressure chamber of the press. Some use two-speed shafts, employing a quill worm driven by separate gearing that allows the feed worm on the inlet end of the shaft to revolve faster than the rest of the worms. Others use larger diameter barrels with a deeper channel (clearance between the barrel and the hub of the shaft) at the feed end. Sometimes star wheels are used to trap the incoming material within the barrel so it cannot back up into the feed hopper. A star wheel is a... 

We have found also fcc-Fe particles inside carbon nanotubes. The existence of these particles which are not stable under normal conditions can be explained by the effect of hard graphite shell, covering these particles. Such a shell can be considered as a nanoscale high pressure chamber. Three orientations of fcc-Fe particles [100], [110] and [111] have been identified in the present study. One more orientation [112] is known for fcc-Fe. Three orientations for fee Co particles [112], [110] and [111] are known as well. For a-Fe particle shown in Fig. 2 the direction [121] is oriented along the fiber growth axis. [100] and [111] directions for bcc iron particles are known as well [3-4]. 

Stearic acid is manufactured by hydrolysis of fat by continuous exposure to a countercurrent stream of high-temperature water and fat in a high-pressure chamber. The resultant mixture is purified by vacuum steam distillation and the distillates are then separated using selective solvents. 

VIO. Vermeulen-Cranch, D. M. E., Anesthesia in a high pressure chamber. In Clinical Application of Hyperbaric Oxygen (I. Boerema, W. H. Brummelkamp, and N. G. Meijne, eds.) pp. 205-208. Elsevier, Amsterdam, 1964. 

Surface species formed on the sample during the CO hydrogenation was observed by the diffuse reflectance FTIR (DRIFT) spectroscopy with a high-pressure chamber equipped with ZnSe window (Spectra-Tech Inc.) (18-23). After the sulfidation of Ae precursor in the same manner as described above, the... 

A Novocontrol Alpha-Analyzer (v=10 -10 Hz) was used for dielectric measurements, both at atmospheric and at high pressure. For atmospheric pressure measurements, a parallel plate capacitor separated by a quartz spacer (empty capacitance 90 pF) and filled by the sample was placed in the nitrogen flow Quattro cryostat (T= 100-3 60 K). For high pressure measurements, a sample-holder multi-layer capacitor (empty capacitance 30pF) was separated from the pressurizing fluid (silicon oil) by a Teflon membrane. The high pressure chamber (Cu-Be alloy), provided by UNIPRESS, was connected to a hydraulic pump able to reach 700 MPa, and controlled in the interval 195-360 K within 0.1 K by means of a thermally conditioned liquid flow. 

An experimental study of jets of boiling-up water has been made on a setup of short-term action, which ensures a stationary regime of an outflow from a high-pressure chamber into the atmosphere for 5-10 s. The initial state p, r ) of water in the chamber varied along the saturation line from T = 200 °C to temperatures close to and isobars. Considerable water superheats in a flow were ensured by the use of short channels J// l d is the diameter of a cylindrical channel, / is its length), in which high rates of pressure decrease are realized (of the order of 10 MPa/s). 

Samples with dimensions t )26 x 10mm were processed with SHS/HIP under gas pressure of 1 IMPa in HIP apparatus R120. The dimensions of the high-pressure chamber is 4) 120 x 350mm. Several large samples can be processed in each batch. 

SERS has been used also under high-pressure conditions by Podini and Schnur" who discuss the reliability of the measured parameters. Sandrof et have used high-pressure chambers, too. 

Immerse the sample cell in a hydrostatic medium in a high-pressure chamber that is compatible with existing spectrometers and that is connected to the pressure-generating unit by semiflexible tubing. Since spectroscopic constraints often require a transparent fluid and preclude the use of oil, incorporate a phase separator in this line. Standardize the dimensions and specifications of the high-pressure chambers where possible, but allow flexibility to accommodate different measurements. 

If they return to atmospheric pressure too rapidly, large bubbles of nitrogen gas will form in their blood and cause a potentially lethal condition known as the bends or decompression sickness. The diver must enter a hyperbaric (high pressure) chambers to redissolve the nitrogen back into the blood. 

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