Gas environment

An electrochemical vapor deposition (EVD) technique has been developed that produces thin layers of refractory oxides that are suitable for the electrolyte and cell interconnection in SOFCs (9). In this technique, the appropriate metal chloride (MeCl ) vapor is introduced on one side of a porous support tube, and H2/H2O gas is introduced on the other side. The gas environments on both sides of the support tube act to form two galvanic couples, ie. 

A = effective surface area for heat and mass transfer in m L = latent heat of vaporization at in kj/kg k = mass-transfer coefficient in kg/ (sm kPa) t = mean source temperature for all components of heat transfer in K t = Hquid surface temperature in K p = Hquid vapor pressure at in kPa p = partial pressure of vapor in the gas environment in kPa. It is often useful to express this relationship in terms of dry basis moisture change. For vaporization from a layer of material ... 

A variation on the wet-spinning technique involves extruding into a heated gas environment. In this dry-spinning process, the temperature and composition of the gas control the extraction process. 

In recent years several new Ni-Cr-Fe-Mo and Ni-Cr-Fe-Mo-Cu have been introduced with improved resistance to sulphide stress cracking in sour oil and gas environments. ... 

Both heated stages [224] and ambient temperature gas environments [225,226] have been developed for use in electron microscopy and both are combined [227,228] in the controlled atmosphere instrument. Pressures of up to 30 kPa and temperatures up to 1500 K have been used in studies of a wide variety of solid—gas and catalytic reactions [ 229]. 

Gas flows are encountered in many microsystems like micro-motors, micro-turbines, micro-sensors, and microfluidic systems in the presence of air or gas environment. Since the ratio of surface area to volume increases in such microsystems, surface forces become dominant over the body forces, and gas flows have great affects on the performance and reliability of many microdevices. 

It should be stressed that environment conditions strongly influence the friction behavior of NFC coatings. In Erdemir s work, super-low friction coefficient was attained only in vacuum or an inert gas environment [22,51]. When oxygen and moisture are presented, friction coefficient dramatically increased [22,52,53]. 

If an elastomer is bonded to a substrate such as steel, it is usual for the bond to have small areas of imperfection where the adhesive or the chemical preparation of the surface is defective. Such areas are known as holidays. In high-pressure gas environments, these holidays form nucleation sites for the growth of half-bubbles or domes, under conditions where gas has been dissolved in the elastomer and the pressure has subsequently been reduced. Gas collecting at the imperfection at the interface will inflate the mbber layer, and domes will show as bumps on the surface of the mbber-coating layer—just as a paint layer bubbles up in domes when the wood underneath gives off moisrnre or solvents in particular areas. 

One of the advanced concepts for capturing CO2 is an absorption process that utilizes dry regenerable sorbents. Pure sodium bicarbonate from Dongyang Chemical Company and spray-dried sorbents were used to examine the characteristics of CO2 reaction in a flue gas environment. The chemical characteristics were investigated in a fast fluidized reactor of 0.025 m i.d., and the effects of several variables on sorbent activity, including gas velocity (1.5 to 3.5 m/s), temperature (40 to 70 °C), and solid concentration (15 to 25 kg/m /s)], were examined in a fast fluidized-bed. Spray-dried Sorb NX30 showed fast kinetics in the fluidized reactor. 

Figure 4.15. Atomically resolved TEM images of a Cu/ZnO model catalyst in various gas environments together with the corresponding Wulff construction of the Cu particle (a,b) Cu nanocrystal faceted by (100), (110) and (111) surfaces the TEM image was recorded at 1.5 mbar of H2 at 220 °C with the electron beam parallel to the [Oil] zone-axis of copper. The insert shows EELS data at the Cu L2,3-edge...

Discuss the role of the surface free-energy in phenomena such as alloy segregation, surface reconstruction, faceting and sintering of small particles. How does a gas environment (air, vacuum) affect the surface composition of alloys ... 

The classical Chinese method consists of inoculating steamed rice grains spread on big trays with a strain of Monascus anka and incubating in an aerated and temperature-controlled room for 20 days. In these types of cultures, moisture content, oxygen, and carbon dioxide levels in the gas environment, as well as cereal medium composition, are the most important parameters to conhol. 

These preliminary tests showed the process to be basically sound but left questions concerning, especially, electrode materials. For use in a carbonated gas environment, carbon elements would be unsuitable. At the cathode, carbon would be removed by ... 

But in the melts with 1% vanadia (Table 4) the equilibrium is more determined by Eq. (52) in an S02-rich gas environment, the V204 complex dominates. Addition of sulfate increases the trend to more negative potentials. With 02 present, the equilibria ... 

Table 3. Comparison of experimental and calculated equilibrium potentials for various gas environments and electrolyte compositions, 400 °C, relative to Ag/Ag+ reference. Results are reported on the basis of changes in the equilibrium potential relative to a base case of pure potassium pyrosulfate under an air environment.

Table 4. Comparison of the equilibrium potential of non-vanadia and vanadia containing electrolytes (versus Ag/Ag+) under different gas environments and sulfate compositions, 370 °C.

Base Electrolyte Composition Gas Environment Experimental (V) 0.0% v2o5 1.0% v2o5 ... 

Because carbon has a natural affinity for adsorption of heavy hydrocarbon species and polar molecules, CMS membranes need to be used at a sufficiently high temperature to eliminate contribution/interference of the adsorption. In contrast, strong adsorption of heavier molecules may be used to separate those species by adsorption as discussed earlier by the SSF mechanism (Rao and Sircar, 1993b). The SSF carbon membranes typically have pore dimensions much greater than those needed for CMS membranes since the separation is based on the adsorbed species effectively blocking permeation of other components (Fuertes, 2000). Carbon membranes are resistant to contaminants such as H2S and are thermally stable and can be used at higher temperatures compared to the polymeric membranes. For the synthesis gas environment, the hydrothermal stability of carbon in the presence of steam will be a concern limiting its operation temperature. 

It has been observed that cobalt may undergo large-scale reconstruction under a synthesis gas environment.27 Reconstruction is a thermodynamically driven process that results in the stabilization of less reactive surfaces. Recent molecular modeling calculations have shown that atomic carbon can induce the clock reconstruction of an fee cobalt (100) surface.28 It has also been postulated and shown with in situ x-ray adsorption spectroscopy (XAS) on cobalt supported on carbon nanofibers that small particles (<6 nm) undergo a reconstruction during FTS that can result in decreased activity.29... 

Conductive sample coatings are not needed because the gas molecules in the chamber replenish electrons on the sample surface to prevent charging. Direct observation of either wet or dry specimens is possible based on the continuously variable specimen environment. The instrument accommodates a micromanipulator, heatable stage, and gaseous environment. Energy dispersive x-ray (EDX) units can also be added to the sample chamber for elemental analysis. Samples can be analyzed in their natural state, at elevated relative humidities, elevated temperatures, and in various gas environments (including 100% relative humidity). 

Finally, also in the laboratory the study of the interaction of cavities inside a uniform fermionic background is of importance (Bulgac and Wirzba., 2001). Examples are C6o buckyballs immersed in liquid mercury. The liquid metal itself serves only as free-moving shapeable neutral background which provides the Fermi gas environment by its conductance electrons, in which the buckyballs drill the voids. Another example would be buckyballs in liquid 3He as Fermi gas. Finally, in the future, boson condensate cavities immersed in dilute atomic Fermi condensates could serve as further system with which the effective interactions of cavities inside a Fermi gas can be studied in the lab. 

This paper explores the trade-offs of gem damage during LIBS analysis and data quality under a variety of analytical conditions. Two lasers, a Big Sky Laser Technology (now Quantel USA) Nd-YAG nano-second laser operated at its fundamental wavelength of 1064 nm, and a Raydiance, Inc., pico-second laser operated at its fundamental wavelength of 1552 nm as well as harmonics at 776, 517.2, and 388 nm, are used in separate LIBS systems. Furthermore, the use of inert gas environment (He or Ar) is explored to increase peak intensities at lower laser power and sample damage. 

Several conditions must be met for successful ETEM investigations. Thin, electron-transparent samples are necessary—this requirement can usually be met with most catalyst powders. Ultrahigh-purity heater materials and sample grids capable of withstanding elevated temperature and gases are required (such as those made of stainless steel or molybdenum). The complex nature of catalysis with gas environments and elevated temperatures requires a stable design of the ETEM instrument to simulate realistic conditions at atomic resolution. 

The design of in situ atomic-resolution environmental cell TEM under controlled reaction conditions pioneered by Gai and Boyes (87,89) has been adopted by commercial TEM manufacturers, and latter versions of this in situ instrument have been installed in a number of laboratories. In situ atomic resolution-ETEM data demonstrated by Gai et al. (85-90) have now been reproduced by researchers in laboratories using commercial instruments examples include investigations of promoted ruthenium and copper catalysts in various gas environments (93) and detailed investigations of Ziegler-Natta catalysts (94). 

In situ dynamic surface structural changes of catalyst particles in response to variations in gas environments were examined by ETEM by Gai et al. (78,97). In studies of copper catalysts on alumina, which are of interest for the water gas shift reaction, bulk diffusion of metal particles through the support in oxygen atmospheres was shown (78). The discovery of this new catalyst diffusion process required a radical revision of the understanding of regeneration processes in catalysis. 

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