The Deposition Mechanism and Protective Properties of Manganese-Based Conversion Coatings on the Surface of AD31 Aluminum Alloy

Protection of Metals and Physical Chemistry of Surfaces - The stage mechanism of manganese-containing conversion coatings (MCCs) formation on the surface of AD31 alloy (AA6063) in acidic (pH 3)...     

The Effect of Ultrasound Treatment on Physicochemical and Tribological Properties of Electrolytic Cu–Sn–TiO2 Coatings

Protection of Metals and Physical Chemistry of Surfaces - In this work, Cu–Sn–TiO2 composite coatings have been deposited from an oxalic acid electrolyte additionally containing 4 g/dm3...     

Influence of the hydrogen reduction time and temperature on the morphology evolution and hematite/magnetite conversion of spindle-type hematite nanoparticles

We report on the transformation via hydrogen reduction of spindle-type hematite nanoparticles into hematite/magnetite hybrid iron oxide particles. The transformation process consists of the reduction of nanoparticles powder in an autoclave using hydrogen gas at a fixed pressure of 11 bars. Both temperature and time of reduction are varied between 300 °C to 360 °C and 0 to 45 h. X-Ray powder diffraction data on the obtained powder and corresponding Rietveld refinement allow the amount of reduced hematite to be determined as a function of these two parameters. Kinetics parameters are measured and an estimation of the activation energy is obtained through linearization of the Arrhenius equation. While reduction is dramatically accelerated at higher temperature, the morphology of the nanoparticles only remain qualitatively unchanged at 300 °C as seen from transmission electron microscopy images. The mechanisms underlying morphology changes are still under study and seem to be closely related to reactor pressure.     

Synthesis and dielectric investigations of ZnTiO3 obtained by a soft chemistry route

In this paper, we report a strategy for preparing an inorganic zinc titanate precursor by applying a chemical bath deposition method (CBD) to ZnO nanocrystals in an aqueous layered titanate colloid. The zinc titanate precursor, obtained as a precipitate, undergoes profound changes under the influence of elevated temperatures in normal atmospheric conditions and allows us to obtain zinc titanate ZnTiO₃ with a rhombohedral symmetry. Investigations of its dielectric properties enabled us to determine a dielectric permittivity (?) of 25, a low loss factor tan(δ) < 10⁻³, and a temperature coefficient (τ_?) of 18 ppm at the frequency of 1.15 MHz. The density of the zinc titanate ceramic was equal to approximately 80% of the theoretical density of the ZnTiO₃ crystals.