Formation of Titanium Oxide by Thermal-Electrochemical Process on the Blasted Titanium Alloys Substrate

Titanium oxide is believed as one of the key factors that influence the excellent corrosion properties as well as biocompatibility of titanium alloy. In the present research, thermal-electrochemical anodizing processes were performed in order to form thick layer of titanium oxide on titanium alloys (Ti6Al4V) surface. Oxidation temperature, blasting and anodizing voltage were selected as the evaluated parameters process at the present study. It was observed that temperature plays important role in the formation of oxide layer, where the thickness of the oxide increases significantly as temperature increases. However, for the case of oxide layer formed by thermal oxidation at temperature of 950oC, oxide layer on the non-blasted sample become easily peel off, whereas oxide layer on the blasted sample shows good adhesion properties. In addition, oxide layer on the blasted samples also have thicker layer as compared with oxide on the non-blasted sample. On the other hand, it was observed that further oxidation by anodizing at 43V and 63V create finer oxide layer by the filled up of porosity on the existing oxide layer. However decreasing of oxide layer thickness was also observed after anodizing, which is predicted due to the breaking up the outer oxide layer during anodizing process.

Research on the Microstructure and the Growth Mechanism of Oxidation Film of T91 Steels after Service

The character of structure and the micro-area elements of inner oxidation film were investigated by using metallographic microscope, electron microscopy, energy spectrum analysis and other testing methods based on samples of superheater and reheater tube cutting from three units. The results showed that the inner wall oxide layer of T91 steel superheater tube after running exhibited a double-layer structure, including inner and outer layer, and the interface between the two layers is the original metal surface. There exists a transition zone between the inner oxide film and metal matrix. A concentration gradient of alloy element in transition zone can be observed and the intergranular oxidation is present. The Fe-rich outer oxide layer does not contain Cr, which consists of Fe3O4, and the internal oxidation layer is composed of (Fe,Cr)3O4.

The Influence of Vacuum Annealing on the Nucleation and Growth Kinetics of Uranium Hydride

ABSTRACTThe reaction kinetics of depleted uranium under constant hydrogen pressure (1 bar) have been measured as a function of reaction temperatures between 65 and 385 °C for as-polished and vacuum annealed samples. Enhanced hydrogen reactivity was observed on samples that underwent vacuum annealing prior to hydrogen exposure. The enhanced reactivity was found to be the result of enhanced nucleation rates on annealed samples since the specific rate per reacting unit area remained unaffected. X-ray photoelectron spectroscopy demonstrates that the nucleation kinetics were promoted on annealed samples as a result of the dehydration and partial reduction of the UO2+x outer oxide layer and the formation of an oxycarbide (UOxCy) sub-layer.

Effect of Oxidation Agent on Pickling of 430 Stainless Steel

430 stainless steel is used as raw material and pickling in HCl-based electrolytes is adopted, and the effect of oxidation agent on removal behavior of the oxide layer on stainless steel is systematically studied; study found that the oxide layer of stainless steel after heat treatment in the lab is composed of iron oxide and chromium oxide, and outer oxide layer has dense structure while inner layer has multihole structure; with the increasing oxidation agent addition, corrosion potential of stainless steel after heat treatment increased; under 1.0% oxidation agent addtion condition, only few inner oxide remained and removal tendency of oxide layer is obvious when pickled for 200s; oxide on surface totally got removed, and a smooth surface obtained after pickled for 400s.