Type conversion

As with HjS, the distribution of sulfur among the other FCC products depends on several factors, which include feed, catalyst type, conversion, and operating conditions. Feed type and residence time are the most significant variables. Sulfur distribution in FCC products of several feedstocks is shown in Table 2-4. Figure 2-9 illustrates the sulfur distribution as a function of the unit conversion. 

Darkowski and Cocivera [94] investigated trialkyl- or triarylphosphine tellurides, as low-valent tellurium sources, soluble in organic solvents. They reported the cathodic electrodeposition of thin film CdTe on titanium from a propylene carbonate solution of tri-n-butylphosphine telluride and Cd(II) salt, at about 100 °C. Amorphous, smooth gray films were obtained with thicknesses up to 5.4 p,m. The Te/Cd atomic ratio was seen to depend on applied potential and solution composition with values ranging between 0.63 and 1.1. Polycrystalline, cubic CdTe was obtained upon annealing at 400 C. The as-deposited films could be either p- or n-type, and heat treatment converts p to n (type conversion cf. Sect. 3.3.2). 

Peter and Wang [266] invented a channel flow cell for rapid growth of CdTe films they showed that 2 p,m Aims can be deposited in less than 20 min, as opposed to the 2-3 h normally required in the conventional stirred single batch cells. The as-deposited films were structurally more disordered than the conventional ones, but after annealing and type conversion they became suitable for fabrication of efficient solar cells. A test cell with an AMI.5 efficiency approaching 6% was fabricated using a film prepared in the channel cell. 

Mediated by Other Metals. In addition to the metals discussed above, other metals have been found to mediate the Barbier-Grignard-type conversions in water, but investigations on these metals are relatively limited. 

The coordination numbers of the atoms increase from 6 to 8 in the NaCl —> CsCl type conversion therefore, it is a reconstructive phase transition which can only be a first-order transition. 

In comparison to the research in n-type oxide semiconductors, little work has been done on the development of p-type TCOs. The effective p-type doping in TCOs is often compensated due to their intrinsic oxide structural tolerance to oxygen vacancies and metal interstitials. Recently, significant developments have been reported about ZnO, CuA102, and Cu2Sr02 as true p-type oxide semiconductors. The ZnO exhibits unipolarity or asymmetry in its ability to be doped n-type or p-type. ZnO is naturally an n-type oxide semiconductor because of a deviation from stoichiometry due to the presence of intrinsic defects such as Zn interstitials and oxygen vacancies. A p-type ZnO, doped with As or N as a shallow acceptor and codoped with Ga or Zn as a donor, has been recently reported. However, the origin of the p-type conductivity and the effect of structural defects on n-type to p-type conversion in ZnO films are not completely understood. 

On the other hand, n-type behavior was observed at more negative potentials, where excess Cd may have been present. Type conversion, from n-to p-, was also frequently achieved by annealing deposits near 350°C [218],... 

Maximizing LCO yield is largely a bottoms management process. Recycle can be employed to fully maximize LCO at reduced conversion, while maintaining bottoms equal to that of a traditional maximum gasoline operation. Due to the lower conversion, coke yield is also reduced. Feed type, conversion level, recycle stream need to be chosen carefully to fully optimize the recycle operation. 

A masking layer 31 is formed on a p-type HgCdTe body 10 to restrict the etching and conductivity-type conversion. The body is bombarded with ions 11 to etch away a part 21 of the body and to produce from the etched-away part of the body an excess concentration of... 

Selectivity is a key topic for the design of reactors in recycles. From the standalone viewpoint the means to influence selectivity are reactor type, conversion level and mixing method. In the standalone view low conversion and PFRs are recommended for achieving good selectivity. By contrast, following the results of RSR analysis, the recycle policy and the plantwide control of reactant feeds can play the determinant role the reactor type or the conversion level is less important... 

The measurement of a thermal activation energy implies that type conversion has been achieved, which restricts application to a very few acceptors, i.e. Mg, Ca, Be and an unknown native defect (possibly V<3a). Mg is the only acceptor which has been at all widely studied, mainly in GaN but also, to some... 

A perhaps still more general type conversion was incidentally -uncovered by Bradley and co-workers during the eame -work, win n epkddorohydrin was found to react -with ethylene ehlorohydrin in ibo... 

With optimized process operation the reaction is strongly regioselective. The process is commercialized by Rhone-Poulenc using Ruhrchemie s TPPTS and yields precursors for vitamin E cf. Section 3.1.1.1.3 [163, 164] Sc or Y triflates catalyze aqueous biphasic reactions which are alternatives to base-catalyzed processes such as aldol or Michael-type conversions [257]. 

This determination is of key importance for the optical and electronic characterisation of solar cells, since a thickness determination is otherwise quite challenging. The as-grown electrodeposited CdTe is nanocrystalline and has rather poor electronic properties. Marked improvement is obtained in a subsequent annealing process involving CdCb vapour and temperatures around 430 C, as described by Birkmire et al. (1991). If this process is performed in air, the crystallisation is accompanied by a type-conversion towards p-type material. 

Tab. 3.28 Cobalt-catalyzed intramolecular Heck-type conversion...

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