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Microwave Plasma Chemical Vapor Deposition of Diamond
Published in Mark A. Prelas, Galina Popovici, Louis K. Bigelow, Handbook of Industrial Diamonds and Diamond Films, 2018
Remote plasma generation and transport of growth species via high velocity gas streams was investigated by several groups (see, e.g., [Rudder et al. 1988]) and in 1992 ASTeX introduced their 2.45 GHz remote microwave plasma LADS (Large Area Deposition System) reactor for up to 8 inch diameter substrates4 [Post, 1993]. Figure 12 sketches the system set-up. A microwave plasma is generated in a tubular reactor and the species are ejected into a chamber with the substrates mounted inside a furnace. Stationary or rotating substrates of up to 8 inches can be used in such a system. The high gas velocities required to produce the plasma jet would consume substantial amounts of gas. Therefore, the LADS approach includes a gas recycling system with gas circulation pump, filter and heat exchanger. The gas composition is measured by mass spectrometry and kept at the desired level by a gas supply and metering unit.
Biogas Production
Published in Luis F. Diaz, George M. Savage, Clarence G. Golueke, Resource Recovery from Municipal Solid Wastes, 2018
Luis F. Diaz, George M. Savage, Clarence G. Golueke
Gas production and composition are two very useful parameters. Total gas production is a measure of the activity of the entire microbial complex, inasmuch as CO2 is produced both by the acid formers and by the methanogens. Gas composition is important because it distinguishes between methane and CO2. Since methane is a product only of the methanogens, its concentration is indicative of the condition of the methanogen population.
MICROSTRUCTURE SENSORS FOR FLOW, DIFFERENTIAL PRESSURE AND ENERGY MEASUREMENT
Published in A. Attari, D.L. Klass, Natural Gas Energy Measurement, 2003
R. Higashi, R.G. Johnson, A.K. Mathur, A.N. Pearman, U. Bonne
temperature even if its temperature coefficient is much smaller than that of diodes or thermistors. Figure 4 shows the temperature changes of the detector resistors in a typical differential pressure measurement, and the resulting temperature differential between the upstream and downstream detector resistances. Figure 5 shows pressure differential characteristics at four ambient temperatures and illustrates the temperature compensation that can be achieved over a broad operating temperature range. The sensor measures mass flow quite accurately under density changes caused by variations in ambient temperature and ambient pressure. Variations of gas composition involve changes in many properties of the gas such as specific heat, molecular weight and size, and others. Therefore, because the gas flow sensor responds to changes in the gas other than just molecular mass, changes in composition may not always lead to sensor outputs indicative of changes in molecular mass, (Fig. 6). Figure 7 shows a comparison between helium (He) and air as an example in which the sensor output appears consistent with the mass flow rather than volume flow, and is independent of gas composition. For minor gas composition differences, the mass flow errors are generally quite small. Figure 8 shows the excellent reproducibility in signal vs. differential pressure across the flow channel obtained for four sensor units from one process batch. Because of the close relationship between heating value of natural gas and its density, we believe that energy flow sensing is directly possible with this device. A correlation between natural gas heating value and density, shown in Figure 9, is less satisfactory than generally assumed, since errors of over 10% occur, even if propane-air peaking mixtures are excluded. If included, the accuracy deteriorates further. However, means to improve these accuracies are possible and are being studied. Applying corrections to density can lead to results which may be useful for natural gas energy flow measurement, as shown in Figure 10. A safety test was made at PSC to demonstrate that a microbridge overvoltage burnout does not ignite a stoichiometric gas-air mixture. The microbridge chips were placed in a premlxed (0.8 stoichiometry) gas air
Gasification of cotton stalk in a downdraft gasifier
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
The gas composition was analyzed using gas chromatograph. The heating value of the producer gas is sum of the product of heating value of different combustible gas constituent and its volume fraction in the gas. The relation for determining the heating value of producer gas is given by Eq. (12).
Cathodic hydrogen recovery using Y zeolites loaded nickel(II) Oxide instead of Pt/C in microbial electrolysis cell
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Gai Wang, Qiong Bo, Donghua Yang, Yupeng Li, Yanchun Li, Chao Ge
The current of the MEC was recorded every 30 min using a digital multimeter (UNI-T 803; Uni-Trend Electronics Co., Ltd., Shanghai, China). Gas production in the MEC was measured by water replacement utilizing g a graduated flask. The gas composition was analyzed by a gas chromatograph (Thermo Fisher Scientific, Waltham, MA, USA).