Papers by Keyword: Surface Oxidation

Abstract: Different types of ALD Ru films, including as-deposited, annealed Ru, without and with a subsequent CMP step, were used for wet etching study. With respect to the as-deposited Ru, the etching rate of the annealed Ru film in metal-free chemical mixtures (pH = 7-9) was found to decrease substantially. X-ray photoelectron spectroscopy characterization indicated that this behavior could be explained by the presence of the formation of RuOx (x = 2,3) caused by the anneal. A short CMP step applied to the annealed Ru wafer removed the surface RuOx, at least partially, resulting in a significant increase of the etching rate. The change in surface roughness was quantified using atomic force microscopy.

Abstract: This research presented the surface oxidation of stainless steel grade 304 (S304) welded by a gas tungsten arc welding (GTAW) process. The welded S304 was inspected by visual and penetrant testing methods. The surface of the welded specimen was oxidized by the chromic solution to an obtained oxide film on S304 welded specimen. After that, the structural phase and crystallite size of the oxide film were investigated by X-ray diffractometer (XRD). The thickness of the obtained film was analyzed by an atomic force microscope (AFM). Furthermore, the effects of the oxide film on hardness and corrosion properties of specimen were analyzed by Vickers hardness tester and potentiostat instrument to study the correlation between the property of oxide film and the surface properties of the welded pipe S304 after oxidation.

Abstract: In paper laser thermal oxidation of austenitic stainless steels AISI 201, 304L of different surface mill finishes, the hot and cold rolled was investigated by the Ytterbium-doped fibre laser (λ=1070 nm) with an output power of 400W by varying scanning speed in the range 5÷20m/s in the air atmosphere. The influence of laser oxidation parameters on the surface colour was evaluated by colorimetric identification.

Abstract: Poly [2-methoxy, 5-(2¢-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) is a well known hole-conducting semiconductor utilized in the fabrication of optoelectronic devices because of its interesting electroluminescence. However, both electroluminescence and electrical conduction in this material sharply deteriorate upon exposure to oxygen, necessitating fabrication and hermetic sealing of the MEH-PPV-based devices in oxygen-free environments. Same shortcoming has excluded the material from applications requiring air exposure. We have recently presented a model for the oxidation mechanism of an MEH-PPV layer and have shown that such layers, after oxidation at certain conditions, can support air-stable electrical conduction. Here, we describe the experimental conditions required for the preparation of an oxidized MEHPPV layer, and provide experimental data on the stability of such layers at different conditions. It is shown that the fabricated air-stable oxidized MEH-PPV layers are excellent for a number of chemical sensor applications.

Abstract: The 22MnB5 steel of Wuhan Iron with three early treatment (pickling, cold-rolling and cold-rolled annealing), then high-temperature oxidation, surface morphology and element of the oxide layer were observed after oxidation testing. The result shows that the oxide layer thickness of cold-rolled annealed sheet is maximal, followed by cold rolled sheet, the pickling sheet is minimum; The surface roughness is associated with degree of oxidation; Si and Cr content increase sharply in oxide layer of 22MnB5 steel after annealing, annealing and cold rolling have little effect of Mn content in the oxide layer.

Abstract: In order to solve the problem of the magnetic property deterioration of the amorphous cores annealed under high absolute water content condition, the deterioration mechanism was studied by using the SEM and X-ray diffraction equipment. The experimental results indicate that the magnetic properties deterioration of the amorphous cores is mainly related with the oxidation of the amorphous cores. It has been found that the oxidation occurred on the surface of the annealed amorphous materials. What’s more, the oxidation formed at the defects of the amorphous materials in priority. Thus the surface quality has a major impact on the oxidation and the magnetic properties deterioration. By analysis of the possibility of the chemical reaction, it is believed that the oxidation is caused by the Fe or B reaction with H₂O. With the holding time increased, the oxides size and quantity increased. To reduce the influence of the H₂O in the air on the magnetic properties deterioration of the amorphous materials during heat treatment, the experiment by aerating the N₂ to the heat treatment furnace was performed. The experiment result proves that the magnetic properties of the amorphous cores were improved during annealing in N₂, which almost reaches the same level of the amorphous cores annealed under low absolute water content condition.

Abstract: Linear assembly of densely packed oxidized nanodiamonds (OxNDs) was achieved in polyepoxide-based nanohybrid films. A homogeneous suspension of pre-polymer of polyepoxide and OxNDs was cast onto a polyamide-spacer and subjected to an electric field in order to induce relocation and stretched-assembles of the fillers before the mixture became cross-linked. The OxNDs suspended readily, forming linear assemblies of OxNDs (LAOxNDs) of varying thicknesses, and aligned vertical to the film surfaces. Nanohybrid films with assemblies of LAOxNDs led to a significant enhancement in thermal conductivity while maintained the electrical insulation property of the polyepoxide. Mechanisms for the formation and structural variation of LAOxNDs in the matrix are elaborated regarding the improvement in physical properties. The present ambient-oxidation process and field-induced application are simple, but effective in enhancing the thermal properties of the polymer-based hybrids, and hence, promising for applications in the semiconductor industry, such as thermal interface materials.

Abstract: NiTi shape memory alloy is widely used as biomaterial for its superior mechanical properties and good biocompatibility. Effective protocols based on the surface oxidation mechanisms, which would precisely control the formation of surface oxide, should be designed and implemented to improve the biocompatibility of NiTi alloy based biomaterials. To shed light on the TiOx species formation mechanism on NiTi surface, density functional theory (DFT) based calculations were carried out to study the adsorption and reactions of O2 on the NiTi alloy (100) surface. O2 is found activated and will decompose upon adsorption. At higher O2 coverage, the reconstructed bridge configuration will generate (110) surface of TiO2, and the hollow configuration will evolve to (100) surface of TiO. The formation of TiO2 phase is thermodynamically favored, but only feasible when the temperature is enough high. At lower temperature, the atomic diffusion is slowed down, and the surface reconstruction will be limited. This explains why TiO2 will be dominant TiOx at higher temperature, and TiO will exist at lower temperature. Our current work provides more insights on the initial oxidation of NiTi surface, and these findings would be beneficial to improve NiTi alloy based biomaterials, and might guide the design of new functional materials.

Abstract: In the present study, effect of pre-oxidized (PO) CuO layer in the joining between polyethylene terephalate (PET) and copper (Cu) by using pulsed Nd:YAG laser was investigated. The experimental result for PET/PO Cu (with pre-oxidized layer) and PET/Cu (without pre-oxidized layer) were presented in this paper. The results showed the pre-oxidation surface improved the welding efficiency. The welded area and tensile shear failure load (TSFL) of PET/PO Cu joint were increased when pre-oxidized layer was introduced. This indicates that high heat was absorbed during laser irradiation of PET/PO-Cu joint compare to PET/Cu joint. On the other hand, the fracture surface of PET/PO-Cu showed the presence of Cu and Cu oxide particles in the PET side. While in case of PET/Cu, no occurrence of Cu particles can be observed. The presence of Cu oxide particles and Cu particles were believed may increase PET/PO Cu joint shear force. From the cross-sectional observation of PET/PO Cu joint interface, it was found that an oxide layer in the laser irradiation area was removed and PET seemed to have intimate contact with Cu surface.

Abstract: Alloying elements are added to steel for improving surface properties such as corrosion resistance. The alloying elements exhibit different chemical characters, and they are often enriched to the surface of the alloys during annealing at high temperatures. In this study, depth-resolved X-ray absorption spectroscopy (XAS) measurements were carried out using a two-dimensional detector with geometrical arrangement of grazing exit in detection of fluorescence X-ray emitted from sample surface, in order to characterize the enrichment and oxidation of manganese on the surface layers of an Fe-Mn alloy annealed under low oxygen partial pressure. This technique facilitates non-destructive measurement for characterizing the compositional distribution of manganese in the depth direction. The results showed that manganese was enriched to surface layers of the Fe-Mn alloys during annealing at high temperatures and formed as manganese oxide. The preferential oxidation of manganese by annealing under low oxygen partial pressure is considered the driving force for their enrichment on the alloy surface.