Cadmium surface preparation

Mercury, lead, cadmium and graphite are commonly used cathode materials showing large overpotentials for hydrogen evolution in aqueous solution. Liquid mercury exhibits a clean surface and is very convenient for small-scale laboratory use. Sheet lead has to be degreased and the surface can be activated in an electrochemical oxidation, reduction cycle [3, 22], Cadmium surfaces are conveniently prepared by plating from aqueous cadmium(ii) solutions on a steel cathode. 

While it is possible to bond to a freshly abraded or cleaned metal surface, chemical treatments are preferred for rendering the metal surface inactive to corrosion over time. For low carbon steel, phosphatising is the recommended pre-bond surface preparation treatment. Stainless steel should be passivated or acid etched, while titanium is usually treated with a hydrofluoric acid pickle. Almninium or magnesium are best treated with a chromate conversion coating. Zinc and cadmium are generally prepared mechanically but a phosphate or chromic acid treatment may be used. Brass and copper may be treated with an ammonium persulphate etch or an acid-ferric chloride etch. 

Aluminium is widely applied for decorative and protective requirements, while cadmium , zinc and titanium have been applied to ferrous materials chiefly for their protective value. The method finds particular application in the plating of high-tensile steels used in aviation and rocketry, car fittings and lamp reflectors, and gramophone record master discs, as well as in the preparation of specimens for electron microscopy and in rendering insulated surfaces electrically conducting, e.g. metallising of capacitors and resistors. 

Elbaum R, Vega S, Hodes G (2001) Preparation and surface structure of nanocrystalline cadmium sulfide (sulfoselenide) precipitated from dimethyl sulfoxide solutions. Chem Mater 13(7) 2272-2280... 

Stranski-Krastanov growth has been documented for copper on Au(lll) [101, 102], Pt(100) and Pt(lll) [103], for silver on Au(lll) [104, 105], for cadmium on Cu(lll) [106] and for lead on Ag(100) and Ag(lll) [107-109]. In all of these examples, an active metal is deposited onto a low-index plane of a more noble metal. Since the substrate does not undergo electrochemical transformations at the deposition potential, a reproducible surface can be presented to the solution. At the same time, the substrate metal must be carefully prepared and characterized so that the nucleation and growth mechanisms can be clearly identified, and information can be obtained by variation of the density of surface features, including steps, defects and dislocations. 

The hetero Y-type layers were prepared by an alternating deposition of compound C180AZ0SN and arachidic add ( surface pressure = 25 mNm1 for C180AZ0SN and 30 mNm 1 for arachidic add, and subphase was 10 M aq. cadmium chloride solution). For the preparation of the Z-type layers, the monolayers of C180AZ0SN were deposited only during withdrawing substrates. The Y-type layers were prepared by the ordinary deposition procedure. 

To prepare metal hexacyanoferrate films, very frequently the following procedure was followed first a film of the respective metal, for example, cadmium [79], copper [80], silver [81], or nickel [82, 83] was elec-trochemically plated on the surface of a platinum electrode, and that was followed by chemical oxidation of the metal film in a solution of K3[Fe(CN)6], leading to the formation of the metal hexacyanoferrates. The same method has been used to produce films of nickel hexacyanoruthen-ate and hexacyanomanganate using the appropriate anions [83]. It is also possible to perform the oxidation of the deposited metals in solutions containing hexacyano-ferrate(II) by cyclic oxidation/reduction of the latter. In a similar way, films of copper heptacyanonitrosylferrate have been deposited [84]. 

Hexammino-cadmium Chloride, [Cd(NH3)6]Cl2.—When anhydrous cadmium chloride is exposed to an atmosphere of dry ammonia the gas is rapidly absorbed, the mass increases in bulk, heat is developed, and the hexammine produced. It has also been prepared by exposing anhydrous cadmium chloride to dry gaseous ammonia for two hours in a tube cooled to very low temperature. A layer of liquid ammonia forms on the surface of the solid, and the tube is sealed and kept for some time at —70° C. On opening and allowing the temperature to rise to —30° C. to remove the condensed ammonia a residue of the hexammino-salt is left.2... 

A higher level of size and morphology control in the incipient semiconductors has been accomplished in reversed micelles prepared from cadmium AOT [614] and from mixtures of cadmium AOT and sodium AOT [615] or, alternatively, by arresting particle growth by surface derivatization [592, 621, 622]. Indeed, surface derivatization of semiconductor clusters was first reported for particles in reversed micelles [621] the reversed micelles act to confine precursor ions and to control the growth of the semiconductor particles. Conditions are typically arranged so that, initially, there is no more than one metal ion (say Cd2+) per water pool. Addition of a heptane solution of bis(trimethylsilyl) selenium resulted in the formation of size-quantized metal selenide particles (say CdSe) in the reversed micelles. This solution could be evaporated to dryness and the resultant particles could be reconstituted in a hydrocarbon solvent Alternatively, addition of metal (say Cd2+) ions to the reversed-micelle-entrapped metal selenide particles, followed by the addition of alkyl(trimethylsilyl)selenium, RMSiMe3, led to the formation of alkyl-capped... 

The stripping performances of Bi film on glassy carbon or carbon fiber substrates were examined very carefully by Wang et al. [17]. In addition to these materials, GECE (combined with bismuth film), a very easy to prepare and low-cost electrode, can also be used successfully for simultaneous stripping analysis of cadmium and lead. Zinc was also tried to be detected simultaneously with lead and cadmium but it was not possible to obtain undistorted and linearly increased peaks. The poor response to zinc can be probably attributed to the preferable accumulation of Bi on GECE rather than of Zn which is a result of the competition of these two metals for the GECE surface sites as also observed in other works [18]. 

The clean trough is filled by the liquid on the surface of which the films will be prepared. This liquid is referred to as the subphase. Usually the subphase is either pure water or a dilute aqueous solution of an inorganic salt, typically with a divalent cation, such as cadmium. The nature of the cation and its concentration, as well as the pLI and temperature of the subphase, were found to play an important role in the structure and stability of the films. 

A substrate 10 of silicon comprising an array of switching elements is prepared. Contact pads such as 16 and 18 are connected to inputs of the switching elements. A protective nitride layer 20 is formed, with openings for the contact pads, on top of the substrate. A layer of photoresist 25 is patterned on top of the nitride layer. A layer of indium alloy 26, fabricated from a combination of indium, bismuth, lead, cadmium and tin, is deposited on the substate so as to contact the contact pads. This layer is built up such that its upper surface is higher than the structures that constitute the topography of the substrate. Portions of the conductive layer overlying the photo-resist are removed by a lift off process... 

---