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Liquid Chromatography
Published in Ernő Pungor, A Practical Guide to Instrumental Analysis, 2020
Take racemic and enantiomerically pure norephedrine hydrochloride salts about 100 mg and add 1.5 cm3 10% sodium hydroxide solution and 5 cm3 diethyl ether and cool to 0°C in cooling bath containing ice and sodium chloride solution; add 2.5 cm3 of 12.5% phosgene in toluene dropwise; stir the solution for about 1 hour. Evaporate the organic layer with the rotary evaporator and dry it with anhydrous sodium sulfate; recrystallize the solid from absolute ethanol.
Specific Surface Area
Published in Ko Higashitani, Hisao Makino, Shuji Matsusaka, Powder Technology Handbook, 2019
To obtain an adsorption isotherm, a known amount of adsorptive gas is introduced into a sample tube. The sample adsorbs the adsorptive molecules, and the vapor pressure decreases gradually until equilibrium attains. The introducing pressure and equilibrium pressure must be measured precisely. The adsorbed amount is determined from the difference between the introduced amount and residual amount. The residual amount is evaluated from the same procedure using He gas. In this case, adsorption of He molecules does not occur. Therefore, the adsorbed amount is determined from the difference between the amount of introduced adsorptive molecules and the amount of He gas introduced into the sample tube, comparing at the same equilibrium pressure. By repeating this procedure, adsorbed amounts at various pressures can be obtained. Generally, estimation of the residual amount of adsorptive molecules is performed using He gas, then a dead volume is determined. The residual amounts of adsorptive molecules at the other vapor pressures are calculated using this dead volume. Usually the adsorptive gas is assumed as an ideal gas in the calculation of the amount of gas. In the special case, the correction of a non-ideal gas and the thermal transpiration effect11 are required. The dead volume must be measured immediately before or after the adsorption measurement. During the measurement, the surface level of liquid nitrogen in a cooling bath should be maintained constant within 1 mm at least 5 cm above the powder sample.
Physical Vapor Deposition
Published in Robert Doering, Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology, 2017
Production magnetrons are configured with a moving magnet array, rather than the fixed magnets of Figure 15.5. As shown in Figure 15.6, the magnet assemble is located behind the cathode surface and sloshes around in the water cooling bath, rotating about the cathode centerline. The etch track is usually somewhat heart-shaped with the indentation at the top of the heart roughly on the cathode centerline. This etch track/magnet system is driven by an external motor to cycle around the cathode surface at several Hertz. The exact shape of the etch track can be tailored by adjusting the magnets or the pole pieces. Changing the shape of the etch track results in changes in the uniformity of the deposition, which may be desirable either because of the material used or else the specific geometrical configuration. For example, if the throw distance is increased then more sputtered atoms are lost to the sides of the chamber, resulting in a net reduction in rate as a function of radius. In this case, it may be necessary to adjust the etch track to increase the erosion rate near the edge of the cathode to compensate. Alternatively, the use of a collimator (described below) completely changes the requires erosion profile of the cathode. Each cell of the collimator functions as a tiny pinhole camera, imaging a surface of the cathode onto the sample. Therefore the etch uniformity in that case must be higher than the long-throw case. In each case, it is also possible to tailor the erosion uniformity of the cathode to provide a high level of cathode utilization. Rotating-magnet cathodes might typically use 50–70% of the high purity cathode material before they must be replaced. This is much different from the conventional cathode (Figure 15.5), which may only 15% of its material before the erosion track becomes too deep. Higher cathode utilization results in lower operating cost for the tool as well as longer times between cathode changes.
Hydrogen Isotope (H2 and D2) Sorption Study of CHA-Type Zeolites
Published in Fusion Science and Technology, 2020
Akira Taguchi, Takumi Nakamori, Yuki Yoneyama, Takahiko Sugiyama, Masahiro Tanaka, Kenji Kotoh, Yu Tachibana, Tatsuya Suzuki
Hydrogen isotope adsorption isotherms were obtained using an Autosorb-1MP instrument (Quantachrom, United States). Samples were pre-evacuated at 350°C for more than 15 h. The temperature of the cooling bath was set at either 77, 201, or 250 K. These baths were prepared using liquid nitrogen, a dry ice/ethanol bath, or a circulating freezer containing ethylene glycol, respectively. These same cooling baths were also used in a subsequent desorption study.