Fabrication and examination of oxidation resistance of zinc coated copper and brass components by chemical deposition

n this work, the structure and the oxidation resistance of Zn deposited Cu and brass metallic components are examined. The deposition was accomplished with pack cementation chemical deposition. The examination of the samples was performed with electron microscopy and X-ray diffraction analysis. It was found that coatings on Cu substrate consist of two layers with different Zn concentrations, while coatings on brass were single layered with almost constant Zn concentration. The presence of distinct Zn—Cu phases was revealed in both cases. The subjection of the as coated samples together with the uncoated substrates in air at 400ºC showed that both Zn coated samples have enhanced resistivity in such atmospheres, as most of the coating remained mostly unoxidised, and the substrates were fully protected. On the contrary, the bare substrates appear to have undergone severe damage as brittle oxides were formed on their surface.Publicad

The influence of Tl4Bi2S5 precipitates on the crystalline TlBiS2 properties

Crystalline TlBiS2 having homogeneously distributed Tl4Bi2S5 precipitates was grown by the vertical Bridgman technique in a two-step procedure. X-rays and Transmission Electron Microscopy (TEM) studies were used to identify the as-grown material whereas a Scanning Electron Microscopy (SEM) examination revealed its layered structure. The electrical conductivity a was measured both along (sigma(parallel to)) and across (sigma(perpendicular to)) its layers. IR reflectivity measurements were also performed and the plasma minimum was determined. Both electrical and optical characterization show properties similar to those of TlBiS2 but a reduced N/m* ratio and an irregular voltage oscillation in the I-U characteristics were deduced. Combining the results from these investigations a possible explanation was proposed