Preparation by Chemical Deposition

1) The effect of inihal concentration (Q) of the metal ions M in the bath, which influences the kinetics of film formation through a first-order dissociation of metal-ligand (M-L) complex [ML,] (rate constant, fe), leading to the formation of metal chalcogenide It was assumed that chalcogenide (X) ions are 

Precipitate formation (y), which is nonlinear with concentration and temperature (T). 

A geometry factor, which takes into account the ratio of substrate area to volume of the solution used (s). 

An induction period for the setting up of the relevant chemical equiUbrium 

An induction period (tj for the formation of the catalytic surface on the substrate for film formation. The quantity (C of the soluble metal ions utilized in the formation of the thin film of insoluble semiconductor metal chalcogenide compound at the end of a duration t of the deposition process is  

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Catalysts were prepared by chemically depositing Cu, Ni and Cr on alumina. SRE reaction produces a mixture of H2 and CO. Ni was thought to help breaking C-C bond while Cu and Cr for oxidation of Cl species into CO and H2... 

Physical templates have also been used to facilitate the growth of PAn nanostructures. Nanofibril arrays were prepared by chemically depositing PAn into 20-200 nm pores in anodic aluminum oxide film (30-60 pm thick) that was subsequently etched away with 0.3 M H3P04or through ultrasonication.221... 

Lifshitz, E., Dag, I., Litvin, L, Hodes, G., Gorer, S., Reisfeld, R., Zelner, M., Minti, H. (1998). Optical properties of CdSe nanoparticle films prepared by chemical deposition and Sol-Gel methods. Chemical Physics Letters, 288,188-196. 

Figure 5.53 shows the conductivity of Sn02 films, that were prepared by chemical deposition using SnCl gas in the presence of H2O or O2. As in the first case, it is possible to identify the native region at high temperatures and low partial pres-smes. However, in the impurity region the conductivity is now almost completely independent of P02 and T. The reason for this is that contamination with Cl from the preparation procedmre, leads to a positive doping and thus to an increase in [e ] and a reduction of [Vq] ... 

Detector elements are prepared either by sublimation in the presence of a small partial pressure of O2 or by chemical deposition from alkaline solution containing a lead salt and thiourea or selenourea (63). Lead sulfide and lead selenide deposit from solutions as mirror-like coatings made up of cubic crystallites 0.2—1 p.m on a side. The reaction may nominally be represented by the following ... 

Dirubidium phthalocyanine (PcRb2) and dicesium phthalocyanine (PcCs2) can be prepared by chemical-vapor deposition of benzene-1,2,4,5-tctracarbonitrile and the metal chloride.135 In the solid phase, additional rubidium atoms are complexed between peripheral cyano groups. 

Lead sulfide films have been prepared by various deposition processes like vacuum evaporation and chemical bath deposition. Electrochemical preparation techniques have been used in a few instances. Pourbaix diagrams for all three aqueous lead-chalcogen Pb-S, Pb-Se, and Pb-Te systems, along with experimental results and cited discussion on the chemical etching and electrolytic polishing of lead chalcogenide crystals and films, have been presented by Robozerov et al. [201]. 

The GRADEIS listed are named for the usage to which they are applied, and are usually minimum purities required for the particular application. Fiber optic materials are currently prepared by chemical vapor deposition techniques because any handling of materials introduces impurities. 

Kuo, C.S., Tseng, Y.H., Huang, C.H., and Li, Y.Y. (2007) Carbon-containing nano-titania prepared by chemical vapor deposition and its visible-light-responsive photocatalytic activity. Journal of Molecular Catalysis A Chemical, 270 (1-2), 93-100. 

K.M. Vaeth and K.F. Jensen, Selective growth of poly(p-phenylene vinylene) prepared by chemical vapor deposition, Adv. Mater., 11 814—820, 1999. 

Q. Zhu, R. M. van Teeffelen, R. A van Santen, and E. J. M. Hensen, Effect of high-temperature treatment on Fe/ZSM-5 prepared by chemical vapor deposition of FeCls 11. Nitrous oxide decomposition, selective oxidation of benzene to phenol, selective reduction of nitrous oxide by MO-butane, J. Catal. 221, 575—583 (2004)... 

Copper, silver, and gold colloids have been prepared by Chemical Liquid Deposition (CLD) with dimethoxymethane, 2-methoxyethyl ether, and ethylene glycol dimethyl ether. The metals are evaporated to yield atoms which are solvated at low temperatures and during the warm-up process colloidal sols with metal clusters are obtained. Evaporation of the solvent was carried out under vacuum-generating metal films. These films are showing very low carbon/hydrogen content and were characterized by elemental analyses and infrared spectroscopy (Cardenas et al., 1994). 

Nanomaterials are also prepared by chemical vapor deposition (CVD) or chemical vapor condensation (CVC). In these processes, a chemical precursor is converted to the gas phase and then it undergoes decomposition to generate the nanoparticles. These products are then subjected to transport in a carrier gas and collected on a cold substrate, from where they are scraped and collected. The CVC method may be used to produce a variety of powders and fibers of metals, compounds, or composites. The CVD method has been employed to synthesize several ceramic metals, intermetallics, and composite materials. 

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