Rhodium coatings

Laister and Benham have shown that under more arduous conditions (immersion for 6 months in sea-water) a minimum thickness of 0-025 mm of silver is required to protect steel, even when the silver is itself further protected by a thin rhodium coating. In similar circumstances brass was completely protected by 0 012 5 mm of silver. The use of an undercoating deposit of intermediate electrode potential is generally desirable when precious metal coatings are applied to more reactive base metals, e.g. steel, zinc alloys and aluminium, since otherwise corrosion at discontinuities in the coating will be accelerated by the high e.m.f. of the couple formed between the coating and the basis metal. The thickness of undercoat may have to be increased substantially above the values indicated if the basis metal is affected by special defects such as porosity. 

Rafaeloff, R., Tricot, Y.-M., Nome, F., and Fendler, J.H., Colloidal catalyst coated semiconductors in surfactant vesicles In situ generation of rhodium-coated cadmium sulfide particles in diocta-decyldimethylammonium halide surfactant vesicles and their utilization for photosensitized charge separation and hydrogen generation, J. Phys. Chem., 89, 533,1985. 

Hydrogen production from PhSH in colloidal, rhodium-coated CdS located selectively in the inside of DHP vesicles, was reproducible and had about the same efficiency that symmetrically distributed CdS particles, at equivalent CdS concentration. It seems, therefore, that homogeneously distributed CdS particles contributed to hydrogen production even if they did not exhibit a detectable fluorescence. 

Figure 7 illustrates the mechanism of photosensitized H formation from PhSH in rhodium-coated colloidal CdS in nonpolymerized rationic vesicles. The proposed position of the CdS particle (partially buried in the vesicle bilayer) is supported by the following observations, the last two made specifically in DHP vesicles ... 

Kelly et al. [68] L-Lysine Protein samples from milk and pasta L-Lysine a-oxidase/with BSA and glutaraldehyde Ruthenium/rhodium coated glassy carbon electrode covered with 1,2-diaminobenzene polymer/ + 100 mV vs. an Ag/AgCl ... 

Vukovic, M., Marijan, D. and Cukman, D. (1999) Electrocatalytic activity and anodic stability of electrodeposited ruthenium-rhodium coatings on titanium. J. Mater. Sci. 34, 869-874. 

Visible Light Induced Hydrogen Production from In Situ Generated Colloidal Rhodium-Coated Cadmium Sulfide in Surfactant Vesicles. The first of a series of studies (see also Refs. 505-507) exploring the use of vesicles and reverse micelles for photo-induced charge separation and HER. 504... 

Pemsler et al. earlier introduced the concept of carbon fiber reinforced internal barrier, where diffusion barrier metals are infiltrated electrochemically into matrix-free carbon fibers in a specially oxidized surface ply of C-C. Infiltration was carried out successfully with Re, Rh and Ir. The rhodium coatings were found non-cracked, adherent, and survived thermal cycles to as high as l,600 C. 

Brookhaven (1) X-12C Bending 3 A 2 mrad Rhodium coated Double Si (111)... 

The Biology Department beam line includes a station for protein crystallography (with Supper oscillation camera and FAST TV diffractometer) and a station for small angle diffraction (with a three-circle goniostat and MWPC electronic area detector). The latter station may be available for optimised anomalous dispersion crystallographic studies. The optical design for each consists of a bent pre-mirror, double crystal monochromator and bent post-mirror the mirrors have rhodium coatings (Wise and Schoenborn 1982). 

The data sets from this initial engine work shows that the thrifted rhodium coating at this loading reduces the NOx eluent from the palladium only monolith by ca 50%. Work is underway to optimise the rhodium coating and the data will be published elsewhere. 

The microcalorimetric cell, which is where the process we are studying takes place, is connected to the external enclosure through a thermoelectric cell. The cell contains platinum - rhodium-coated platinum thermocouples coimected in series and electrically isolated from the cell. There mnst be enough thermocouples to record the entire flux emitted by the internal enclosure (see Figure 6.1). 

Sections are collected on gold grids, or on palladium- or rhodium-coated Cu grids. If Cu grids are used, they are first washed in formic acid, followed by distilled water. 

A wider variety of alcohols [18] and alkenes [17] were investigated under CPO conditions on platinum- and rhodium-coated monoliths with 5 wt.% of catalytically active species. The results obtained with monoliths having the same dimensions as for methanol CPO revealed that a small surface area of active species can lead to higher alkene selectivity by homogeneous reactions. Platinum was also judged to be unable to dissociate higher alkenes completely. Thus, an increase in catalytically active surface area by means of a washcoat or a reduction in the channel size can lead to a higher H2 yield. 

Williams, KA, Schmidt, LD. Catalytic autoignition of higher alkane partial oxidation on rhodium coated foams. Appl. Catal. A Gen. 2006399 30-45. 

Jewelry and silverware. Because of its high reflectivity, sterling silver (i.e., a silver-copper alloy) is extensively used for jewelry, silverware, and tableware where appearance is paramount. Sometimes, a protective rhodium coating is electrodeposited onto thin nickel-plated silver objects to avoid tarnishing. Sterling-silver alloy contains roughly 92.5 wt.% Ag, the remainder being copper or some other metals. 

This method is used primarily for the formation of metallic coatings on noncon-ductive substrates. Common deposited coatings using this method include aluminum coatings on plastics and rhodium coatings on mirrors. 

Rhodium is used mainly in platinum alloys the rhodium imparts additional corrosion resistance and good high-temperature characteristics. A rhodium coating on steel or brass is effective for corrosion prevention, especially in sea water. The coating must be very thin to justify its cost. Rhodium has very high optical reflectance and has been used in optical equipment, especially where tarnish might be a problem. Sometimes, it is coated on to silver... 

The reaction is significantly faster than steam reforming and is usually performed in the diEFusion limited regime (57]. The catalytic reaction of hydrocarbons such as octanes over rhodium coated foams starts at relatively low temperatures of around 250 °C [58]. 

Figure3.6 Selectivities as determined for n-octane, isooctaneand a 1 1 mixture thereof over a rhodium coated ceramic foam [65].

Hickman and Schmidt were amongst the first to propose partial oxidation of methane over noble metal catalysts with short contact times of few milliseconds [225]. They used platinum and rhodium coated onto porous alumina foam monoliths. Rhodium showed superior performance, namely higher activity and hydrogen... 

Panuedo, G.J., Williams, K.A. and Schmidt, L.D. (2006) Contributions of heterogeneous and homogeneous chemistry in the catalytic partial oxidation of octane isomers and mixtures on rhodium coated foams. Chem. Eng.J., 61, 4207-4219. 

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