Stainless steel vessels with quartz

The reactor has two reaction zones and is made of a stainless steel vessel with five access ports two vertical access ports which are used for the introduction of reactant gases and the collection of powders, one horizontal access port which is composed of GaAs lens and water-cooled copper block, items 4 and 16 of Figure 3.28, allowing passage of the laser beam, and the remaining two accesses with quartz glass windows to monitor the reaction zones. A stainless steel plate with a suitable hole is placed between two reaction zones to minimise their interaction. 

The equipment and the experimental procedures using the C02-methanol medium have already been described in previous papers. . For the photoelectrochemical experiments, a stainless steel pressure vessel was equipped with a 2-cm thick quartz window for illumination, p-type InP and GaAs wafers were cut into ca. 0.4 cm x 0.5 cm electrodes and were mounted using epoxy resin. Ohmic contact was made with successive vapor deposition of Zn (30 mn) and Au (100 nm), which was annealed afterward at 425 C in Ar. A silver wire (0.8 mm dia) was used as a quasi-reference electrode (Ag-QRE, ca. +80 mV vs. SCE). A Pt wire (0.8 mm dia) was used as the counter electrode. The photocathode was etched in hot aqua regia for ca. 5 s before each experiment. The electrolyte solution [3 cm, 0.3 mol dm" tetrabutylammonium perchlorate (TBAP) in CH3OH] was placed in a glass cell liner in the stainless steel vessel. Gases were introduced into the pressure vessel and were left to equilibrate for one hour at the desired pressure (1 to 40 atm). 

C, is a cylindrical glass vessel with a volume of 450 cm. The piezometer contains the solution and 330 gms of Hg. The top of the piezometer is fitted with a Taper joint for filling. A precision bore capillary, E, (2mm in diameter) is fitted to the bottom of the piezometer. The piezometer is suspended (6) in a brass or stainless steel pressure vessel, H. A glass boiler tube, J, encloses the upper portion of the capillary. The pressure vessel is filled with ethylene glycol which serves as a thermal and pressure medium. The entire apparatus is submerged in a constant temperature bath controlled to 0.001 C. The temperature inside the pressure vessel is monitored with a Hewlett-Packard quartz crystal thermometer (to determine when thermal equilibrium is reached after compression and decompression). 

All extractions were conducted using quartz filters and PUF plugs spiked with standards in 33 mL stainless-steel cells by Dionex (ASE 200). Extractions were performed with 40 mL of solvent(s) at 100 atm pressure by one static cycle. The vessels were rinsed with 10 mL of the same solvent, and the extracted analytes were purged from the sample cells using pressurized nitrogen at 100 atm. Varying the pressure in this range does not affect the results (Li et al. 1998 Saim et al. 1998). 

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