Dimension stable anodes

Titanium as a carrier metal Titanium (or a similar metal such as tantalum, etc.) cannot work directly as anode because a semiconducting oxide layer inhibits any electron transport in anodic direction ( valve metal ). But coated with an electrocatalytic layer, for example, of platinum or of metal oxides (see below), it is an interesting carrier metal due to the excellent corrosion stability in aqueous media, caused by the self-healing passivation layer (e.g. stability against chlorine in the large scale industrial application of Dimension Stable Anodes DSA , see below). 

Dimethyl sulphoxide has also been oxidized electrochemically, using either a platinum anode or a dimensionally stable anode containing iridium and selenium in 1 M sulphuric acid solution158. The former electrode requires a potential close to that required for oxygen evolution whilst the latter needed a potential 0.5 volts lower. Thus the dimension-... 

Ebonex electrodes — When Ti02 is placed into an atmosphere of hydrogen at a temperature higher than 1000 °C partial reduction and formation of Ti02 x phases occurs. Of particular interest is Ti407, a black ceramic material of high electrical conductivity and chemical inertness. This material, Ebonex, has been formed into ceramic electrodes for applications as -+ dimension-ally stable anode [ii] or - cathode [iii]. 

During the 1960s, major research efforts were devoted to the oxides of platinum group metal exhibiting high metallic conductivity, and in 1967, Beer invented RuO2 coatings on Ti substrates for application as anode in chlor-alkali cells.40 41 These dimension-ally stable anodes (DSA ) have been further developed and commercialized by V. deNora.42... 

For small-scale electrolysis units, energy consumption will be much less important than in a chlor-alkali process ease of operation with a minimum of maintenance and replacement of components and the initial cost of the total unit will more often determine the choice of the cell. As a result, for example, while the cathode will generally be steel, a wide range of anode materials including graphite, lead dioxide and platinized titanium have been used as well as dimension-ally stable anodes. Hence the quoted energy consumptions of hypochlorite cells lie in the range 4.5—7.0 kWh kg , considerably above those for a chlor-alkali cell. 

In late 70s of the twentieth century, dimension-ally stable anodes, DSA , were introduced in CAT, bringing forth one of the most important breakthroughs in industrial electrolytic processes... 

Dimensionally stable electrodes — Electrodes (in particular anodes) which remain dimensionally stable during prolonged operation. Many metal and carbon electrodes undergo severe corrosion when employed as cathodes or as anodes. For industrial applications this is not acceptable and metal oxide-based electrodes were discovered as an important alternative [i]. Dimension-ally stable oxide electrodes are manufactured by coating... 

Owing to the finite electrolyte volume ofthe nanoliter droplet, the diffusion boundary layer reaches the dimensions of the droplet within seconds, assuming a diffusion coefficient of for example D = 110-5 cm2 s 1. A constant diffusion gradient can not be established because the bulk concentration is reduced. Thus, measurements of diffusion limited currents are not stable over time. The electron transfer reactions discussed below were carried out on anodic oxide layers with maximum current densities 3 to 4 orders of magnitude lower than the diffusion limited current densities, thus ensuring a stable support of consumables over the time of the measurement. In order to prevent evaporation of electrolyte, the ambient was saturated with water vapor. 

The combination of the rotating anode X-ray generators which are nowadays very stable, the robust one-, two-, three-, or four-circle singlecrystal diffractometers, the area detectors (image plate, wire counters, or CCD), and powerful PCs make solving the crystal structure of a mediumsized molecule a job of a few hours, of a few days, or exceptionally of a week for crystals that are relatively small (< 50 pm in one or all dimensions) and/or show greater disorder. 

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