Copper polycrystalline structure

Figure 7.19. The four basic deposit structural forms of Cu deposited on Cu(lOO) face from acid copper solutions a) ridge b) platelet (c) block (d) polycrystalline. (From Ref. 44, with permission from Elsevier.)...

Hathaway has attempted to assess the value of the electronic properties of polycrystalline mononuclear copper complexes with the [CUN4], [CuNj], and [CuN ] chromophores of unknown crystal structure, in predicting the stereochemical environment of the copper(ii) atom. The value of having B. J. Hathaway, J.C.5. Dalton, 1972, 1196. 

Barnes et al. (Section 7.15, Ref. 10) observed similar results on copper singlecrystal surfaces near the (100) face below 10 mV ridges, 40-70-mV platelets, 70-100 mV blocks, and fine platelets and above 100 mV, polycrystalline deposit. The four basic structural forms are shown in Figure 7.19. 

How the experimental panorama is influenced by parameters still to be defined was demonstrated by Shibata et al. [86]. Here, preliminary results obtained in aqueous media using a specific brand of high-purity commercial copper cathode were positive with regards to hydrocarbons C3+, provided that no electropolishing was performed before the electrochemical process. If electropolishing preceded the C02 reduction, the cathodes behaved similarly to any other copper cathode, leading essentially (besides hydrogen) only to methane end ethylene. A tentative explanation of this behavior was proposed which referred to the polycrystalline matrix of this brand of copper, which made it particularly adaptable to be covered by oxide layers active in the formation of C3+. However, further experimental evidence on the surface structure, composition and modifications with electrolysis time will be required to substantiate this hypothesis. 

The preparation of well-defined single-crystal surfaces of copper oxides in UHV or of well-sintered powders, starting from polycrystalline materials, is difficult. Consequently, structure-catalytic property correlations remain to be established. 

Core level XPS studies of adsorbates of mpim on polycrystalline copper substrates show a double peak structure... 

Thereafter, crystals were brought back to the aerobic 25% MPD solution, buffered with 50 mAf sodium phosphate, pH 5.5. This procedure is based on Avigliano et al. s (157) method of preparing T2D ascorbate oxidase in solution and was modified by Merli et al. (159) for use with ascorbate oxidase crystals. The 2.5-A-resolution X-ray structure analysis by difference-Fourier techniques and crystallographic refinement shows that about 1.3 copper ions per ascorbate oxidase monomer are removed. The copper is lost from all three copper sites of the trinuclear copper species, whereby the EPR-active type-2 copper is the most depleted (see Fig. 10). Type-1 copper is not affected. The EPR spectra from polycrystalline samples of the respective native and T2D ascorbate oxidase were recorded. The native spectrum exhibits the type-1 and type-2 EPR signals in a ratio of about 1 1, as expected from the crystal structure. The T2D spectrum reveals the characteristic resonances of the type-1 copper center, also observed for T2D ascorbate oxidase in frozen solution, and the complete disappearance of the spectroscopic type-2 copper. This observation indicates preferential formation of a Cu-depleted form with the holes equally distributed over all three copper sites. Each of these Cu-depleted species may represent an anti-ferromagnetically coupled copper pair that is EPR-silent and that could explain the disappearance of the type-2 EPR signal. 

A characterization of copper/porous silicon (Cu/PS) nanocomposites fomied by an immersion displacement method is presented. Morphology and structural properties of Cu-PS samples were analyzed using SEM and XRD techniques. The SEM study demonstrates the complicated structure of the Cu/PS samples. The XRD study confirms that deposited Cu is polycrystalline. Copper deposition time has a strong influence on Cu crystal size and the Cu/PS composition. 

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