Copper-embedded low-density polyethylene (LDPE) composites were fabricated using different copper concentrations in the polymer matrix. The copper particles were spherical with a mean particle size between 200 and 300 nm. All the samples were compacted under pressure and melted. The LDPE matrix was analyzed using gel permeation chromatography (GPC) and it did not evidence degradation of the LDPE matrix. The microstructure of the composites was examined with scanning electron microscopy. The electrical conductivity was measured as a function of the copper content, and the composite fabricated with a 10 vol % copper presented a conductivity 15 orders of magnitude higher than that of pure LDPE. The enhancement in conductivity can be explained by means of segregated percolation path theory and the experimental results are in agreement with the theoretical law.

SrTiO, films in the 100-nm thickness range were grown on Ti foils by a 2 4 h hydrothermal treatment at 225°C in an aqueous solution of Sr(OH),. X-ray diffraction showed the principal reflections of cubic SrTiO,. Photoelectron analysis revealed the presence of carbon contamination and suggested the presence of hydroxyl groups on the surface, which disappeared in the film bulk. The Auger depth profiles showed three distinct zones. The outermost layer, besides the common carbon contamination, had a large number of OH groups. The second zone was a clean, almost carbon-free SrTiO, film. The third zone was a diffuse interface region where the Sr and 0 concentrations slowly decreased toward the substrate.

Insulating barium titanate films were successfully grown on Ti-deposited silicon substrates using the hydrothermal method. The film thickness was 35 and 49 nm for films treated at 200 and 250 °C, respectively, in a 0.25 M Ba(OH)2 solution for 8 h. The BaTiO3 films did not reach the Ti/Si interface. X-ray photoelectron spectroscopy revealed OH-free and nearly carbon-free films, which was corroborated using Auger electron spectroscopy (AES) depth analysis. AES revealed that the oxygen and barium concentrations are correlated throughout the film, and the existence of a diffuse BaTiO3/Ti interface. A discussion on the film growth mechanism is made using existing information on the subject.

It is known that lead anodes used in the industrial extraction of copper by electrolysis (electrowinning) suffer corrosion as a result of accidental or intended current interruptions. In order to improve understanding of the corrosion and protection of such anodes, the effects of the concentrations of copper, sulphuric acid, cobalt, iron, manganese, chloride and an organic additive (guar) on the corrosion of lead have been studied by means of weight loss tests and surface analysis techniques (X-ray photoelectron spectroscopy, X-ray diffraction, and wavelength dispersive spectroscopy). The rate of corrosion of lead during current interruptions increases with increasing concentration of sulphuric acid and copper, whereas it decreases markedly in the presence of cobalt and iron and, to a lesser extent, in the presence of chloride and the organic additive. Manganese is the only impurity whose presence does not reduce the rate of corrosion; it is also the only element which precipitates in significant amounts on the lead anode surface under the conditions studied. A method is proposed to establish the optimum anodic protection current density during current interruptions in electrowinning cells. Three current density ranges have been found, of which the 'high' protection range could be caused by the degree of compactness acquired by the PbO 2 layer at applied anodic current densities in excess of 60 A m 22 .