Planar reactor

For the CVD processes organometalhc hafninm compounds are often used. Thus, thin films of hafnium carbide were obtained in a planar reactor from bis(cycl-opentadienyl)dimethylhafhium, (ii -C5H5)Hf(CH3)2 as precursor [11]. The carbon content ranged from 11 to 40 weight % and increased with the deposition rate. The film hardness varied between 1,300 and 2,000 HK. 

Following Sielewiesiuk and Gdrecki, we consider here the FHN model of the BZ reaction in the case of a square planar reactor containing a thin layer of the BZ reactive solution [the position in the reactor is given by (x, y), the solution s depth is assumed being negligible]. Two quantities, u (x, y) and v (x, y), denote the concentration amplitudes of two chemical substances, one called the activator (which is present in the solution) and the other called the inhibitor (which is uniformly immobilized on the bottom of the reactor). The time evolution of their values is modeled by the following set of FHN equations ... 

There are many nonintrusive experimental tools available that can help scientists to develop a good picture of fluid dynamics and transport in chemical reactors. Laser Doppler velocimetry (LDV), particle image velocimetry (PIV) and sonar Doppler for velocity measurement, planar laser induced fluorescence (PLIF) for mixing studies, and high-speed cameras and tomography are very useful for multiphase studies. These experimental methods combined with computational fluid dynamics (CFDs) provide very good tools to understand what is happening in chemical reactors. 

In principle, TPD can also be applied to high-surface area catalysts in plug-flow reactors. Often, however, the curves are seriously broadened by mass-transport phenomena. Hence, the use of single crystals or particles on planar supports offers great advantages for these investigations. 

Owing to the planar layer structure of most micro reactors, uniform illumination is yielded in addition, which can be maintained on increasing throughput by numbering-up [6]. Here, the individual reaction units are assembled in parallel again on a plane, but a larger one. 

The deposition setup as shown in Figure 4a is the central part of the most commonly used planar diode deposition system. The power to the reactor system is delivered by means of a power supply connected to the reactor via appropriate dc or RF circuitry (matchboxes). Power supplies can consist of generator and amplifier combined in one apparatus, with a fixed RF frequency. More flexible is to have an RF generator coupled to a broadband amplifier [119, 120]. 

Another advantage of the micro-LC approach is that the required sample size is minimal, so the sample can be drawn from a 1-1 laboratory scale reactor without influencing the reactor composition. The ISCO pLC-500 microflow syringe pump has proven to be reliable and reproducible in evaluations in our laboratory. Capillary liquid columns have been fabricated on planar devices such as silicon to form a miniaturized separation device.19... 

Two-dimensional distributions of ground-state NO were detected by planar laser-induced fluorescence during the process of NO removal in a corona radical shower system in NO/dry air mixtures [57,58], The authors observed that the density of NO molecules decreased not only in the plasma region formed by the corona streamers and the downstream region of the reactor, but also in the upstream region of the reactor. They explained this behaviour by oxidation with ozone, which is transported upstream by electrohydrodynamic flow. 

Kotaka M, Kakihana H (1977) Thermodynamic isotope effect of trigonal planar and tetrahedral species. Bull Research Lab Nuc Reactors 2 13-29... 

Arthur D. Little has carried out cost structure studies for a variety of fuel cell technologies for a wide range of applications, including SOFC tubular, planar and PEM technologies. Because phenomena at many levels of abstraction have a significant impact on performance and cost, they have developed a multi-level system performance and cost modeling approach (see Figure 1-15). At the most elementary level, it includes fundamental chemical reachon/reactor models for the fuel processor and fuel cell as one-dimensional systems. 

One way to ease any difficulties that may arise in fabricating a membrane, especially in design configurations that are not planar, is to go membraneless. Recent reports take advantage of the laminar flow innate to microfluidic reactors ° to develop membraneless fuel cells. The potential of the fuel cell is established at the boundary between parallel (channel) flows of the two fluids customarily compartmentalized in the fuel cell as fuel (anolyte) and oxidant (catholyte). Adapting prior redox fuel cell chemistry using a catholyte of V /V and an anolyte of Ferrigno et al. obtained 35 mA cmr at... 

Thus most catalysts consist of porous catalyst pellets that may be spherical, cylindrical, or planar and have a characteristic size chosen for desired reactor properties, as we will consider later in this chapter. In most situations reaction occurs throughout the porous peUet, not just on its external surface. 

It is evident that in many situations the reaction rate will be directly proportional to the surface area between phases whenever mass transfer hmits reaction rates. In some situations we provide a fixed area by using solid particles of a given size or by membrane reactors in which a fixed wall separates phases Ifom each other. Here we distinguish planar walls and parallel sheets of sohd membranes, tubes and tube bundles, and spherical solid or liquid membranes. These are three-, two-, and one-dimensional phase boundaries, respectively. 

It is important to attain as high an area as possible for a membrane reactor. Configurations with multilayer planar membranes, coiled membranes, or as multiple tubes also can be used for similar processes with potentially very high surface areas, as sketched in Figure 12-6. 

In the membrane reactor a wall of area separates the phases, and this area is generally fixed by the geometry of the reactor using planar or cylindrical membranes. However, most multiphase reactors do not have fixed boundaries separating phases, but rather allow the boundary between phases to be the interfacial area between insoluble phases. This is commonly a variable-area boundary whose area wiU depend on flow conditions of the phases, as shown in Figure 12-7. 

The concentration profile for a reactant A which must migrate from a drop or bubble into the continuous phase to react might be as shown in Figure 12-10. There is a concentration drop around the spherical drop or bubble because it is migrating outward, but, as with a planar gas-liquid interface in the falling film reactor, there should be a discontinuity in at the interface due to the solubility of species A and a consequent equilibrium distribution between phases. 

In the preceding expression we include an effectiveness factor r to account for pore diffusion limitations of A. Hi fact, if the catalyst film thickness on the wall of the reactor is small enough that we can assume it planar, then the effectiveness factor becomes... 

Figure 12-15 Sketch of concentration profiles between a spherical bubble and a solid spherical catalyst particle in a continuous liquid phase (upper) in a gas-liquid sluny reactor or between a bubble and a planar solid wall (lower) in a catalytic w bubble reactor, It is assmned that a reactant A must migrate from the bubble, tirough the drop, md to tiie solid catdyst smface to react. Concentration variations may occur because of mass transfer limitations around both bubble and solid phases.

Planar or Parallel-Plate Reactor. Because very-large-scale integration (VLSI) demands nearly vertical etch profiles, planar or parallel-plate... 

The active surface to volume ratio of the tubular arrangements previously described is approximately 1 cm2/l cm3. This parameter could be increased with corresponding increases in both volume power density and area power density. New concepts for solid state electrochemical reactors have been proposed based on more or less planar cell structures which can be integrated to make blocks. 

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