Comparison metal deposition techniques

We have employed two multi-elemental techniques (INAA and ICP-AES) to determine sulphur, halogens and 14 other trace elements in urban summer rainfall. Quality control was assured using NBS reference materials. The overall accuracy and precision of these two methods makes possible the routine analysis of many environmentally important trace elements in acid rain related investigations. Enrichment factor calculations showed that several elements including S, Cu, Zn and Cr were abnormally enriched in the urban atmosphere. A comparison of three separate sites showed a strong gradient of metal deposition from the industrial to the outlaying areas. 

In the displacement of Cu from CuSO by Zn and Cd, and of Ag from AgNC>3 by Zn and Cu (24), rates were found as high as eight times the values expected by comparison with dissolution from smooth cylinders. This was ascribed to enhanced transport by local cell electrolysis, but much of the effect was probably due to roughness caused by the metal deposit. With Zn in 2. 5 x 10" M AgNOg (followed by radiotracer technique) the rate was not abnormal of course very little Agwas deposited. 

Besides these chemical methods, electrochemical techniques are of interest. This is because the electrodeposition is a convenient and fast method for the preparation of metallic nanoparticles on large areas of conductive substrates. However, for precise and systematic investigation of the nanoparticle properties control of the particle size, form and distribution is necessary. From this point of view, the classical electrodeposition technique from solution is not so successful, as the homogeneity in particle size and spatial particle distribution is presumably disappointing in comparison to the invasive tip-directed SPM routes [21] or deposition techniques into nanotemplates. 

Following deposition of an active metal upon a ceria surface, it is possible to study chemisorption on a surface that models many of the important aspects expected for actual ceria supported catalysts. Surface techniques offer the possibility to identify where the adsorbates are located and to identify intermediates that are formed in their interaction. By comparison of ceria surfaces, with and without metal, the synergisms between metal and support can be deduced. By controlled metal deposition, it is possible to study the effects of loading and particle size. By selected preparation of the ceria substrate it is possible to vary factors which may affect the interaction between the metal particle and the ceria, sueh as structure, defeet concentration or oxidation state of the ceria. The goal of chemisorption studies, summarized below, is to relate all these factors to the interaction of the model catalyst with particular adsorbates. 

Alternatively PAA can be obtained without solvent by vapor deposition polymerization as described first by Salem et al. [2], In this technique the dianhydride py-romellitic and the dianhydride diamine (4,4 -oxidianiline) are codeposited onto a substrate, where they react to form PAA. Again the transformation to Polyimide is obtained by subsequent heating to temperatures up to 350°C. By comparison to spun dn films, initial interaction of the polymer with the substrate occurs in the uncomplexed PAA state. The chemical interaction between PAA and the metal establishes the adhesion of the final polyimide film. This is discussed in this communication for evaporated gold cluster and bulk silver surfaces. 

Most of the work cited above has dealt with treating the soot in some way before doing the combustion experiments. We wish to report experiments conducted on soot from a diesel vehicle which has been deposited onto catalytic monolithic substrates. This sooted substrate is then placed in a laboratory apparatus where a synthetic gas mixture flows over the sample, and the soot combustion is monitored as a function of temperature. The laboratory set up simulates regeneration conditions on a vehicle. Using this technique we have been able to obtain kinetic information about the oxidation of soot and gaseous products. Comparisons of base metal and noble metal catalysts were also conducted and are reported. It is intended that this work will help elucidate the mechanism involved in the catalytic combustion of soot which should help in developing improved catalytic materials. 

In the production of dials on glass, enormous progress was achieved by replacing old techniques such as chemical etching and mechanical scratching by thin film deposition. Depending on the size of scale, mechanical masks or photo masks are used. The deposited metal is for the most part chromium. Figure 40a shows a comparison of the quality of scales produces by different techniques. 

By the laser treatment, the surface of PTFE films could be made hydrophilic and the surface energy increased in comparison with that of a native PTFE film. As the results, we intended to extend the hydrophilic modification technique into metallization on the PTFE film by using a chemical (electroless) plating technique. If the activators for the plating will deposit only on the hydrophilic region, area-selective metallization will be performed on the surface of PTTE films modified upon the laser-irradiation through a mask by a projection method. 

MOCVD is traditionally a planar surface technique used for the deposition of very thin layers of materials from the vapor phase. This technique offers a wide versatility in the synthesis of dusters in zeolites. The advantage of this technique, in comparison with the ion exchange technique, is that the location of the clusters in the zeolites can be easily controlled by the choice of organometallic precursors e.g. a metal carbonyl or metal alkyl), such that they can be sterically restricted to large channels or cages. For example, with zeolite Y, one can select... 

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