Behavior Of Metal Oxides Research Articles

Efficient and stable supercapacitors using rGO/ZnO nanocomposites via wet chemical reaction

The electrochemical behaviorof metal oxide nanoparticles (NPs) can be improved by maximizing the surface area and combining materials with high electrical conductivity. The reduced graphene oxide (rGO) enables to bestow a larger surface area for intercalation and deintercalation as well as shorter paths for ion transfer, lowering ionic resistance. In the current research, hybrid composites of rGO and zinc oxide (ZnO) NPs were successfully synthesized by using a wet chemical method for the application of supercapacitors. The wet chemical technique for industrial-scale nanocomposite synthesis is easy, fast, and cost-effective and requires no specialized equipment. The size, surface morphology, and crystalline structure of the rGO/ZnO nanocomposites were characterized by using FE-SEM, HR-TEM, and XRD, respectively. By using cyclic voltammetry and Galvanostatic charge–discharge tests, it was confirmed that the capacitances of rGO/ZnO composites were significantly enhanced compared to that of pure ZnO NPs. The proposed nanocomposite could achieve significantly enhanced specific capacitance (258 Fg−1) and also, it was able to achieve a longer life cycle with maximum capacitance retention. We expect that this work provides a simple but very effective strategy for the rGO and metal oxide NP composites.

Microstructure and Oxidation Behavior of Metal V Films Deposited by Magnetron Sputtering.

Direct-current magnetron sputtering (DCMS) was applied to prepare vanadium (V) films on Si substrate. The influence of substrate temperature (Ts) and target–substrate distance (Dt–s) on phase structure and surface morphology of V films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscope (AFM) and transmission electron microscopy (TEM). The results show that the crystallinity of the V films increases with increasing Ts and decreasing Dt–s. The film deposited at Ts = 400 °C and Dt–s = 60 mm exhibits the best crystallinity and <111> preferred orientation with a regular tetrahedral surface morphology. Oxidation behavior of the V thin films has also been studied by X-ray photoelectron spectroscopy (XPS).

Old Technique for New Materials: Characterization of Solid State Hydrogen Storage Materials by Temperature Programmed Reaction

ABSTRACTThe most common diagnostic tools in studying reversible solid-state hydrogen storage materials involve volumetric or gravimetric approaches. In this study, a mature gas solid analysis technique called Temperature Programmed Reaction (TPR) is presented as an alternative and complementary approach in investigating solid-state hydrogen storage materials. TPR is fast, simple and offers valuable information from a wide range of solid materials. This technique is routinely used to characterize the reduction behavior of metal oxide and sulfide catalysts. In a typical TPR experiment, a sample powder is heated at a constant rate under a non steady-state environment of constant pressure and flow of a hydrogen/inert gas mixture, while monitoring the rate of hydrogen absorption and desorption by a thermal conductivity detector. The principle behind TPR is the high thermal conductivity coefficient of hydrogen when compared to other gases. The detector is sensitive enough that a slight change in hydrogen concentration is reflected by significant changes in the thermal conductivity signal. Hydrogen storage materials exhibit fingerprint type TPR spectra, unique to their composition and structure. Specific rates of hydrogen intake, heats of absorption and desorption as well as extent of activation can be extracted from TPR curves. In addition, multiple absorption and desorption states can be identified from the number of absorption or desorption peaks. Material stability and potential structural or phase changes can also be inferred indirectly. The simplicity and the highly sensitive thermal conductivity measurement provide a number of advantages over the traditional volumetric or gravimetric methods. Metal hydride alloys of AB5-type are used to demonstrate the effectiveness of TPR technique in characterizing hydrogen storage materials.

Selective hydrogenation of acetylene on Pd/SiO 2 catalysts promoted with Ti, Nb and Ce oxides

Transition-metal oxides added to Pd/SiO 2 improve significantly the activity and the ethylene selectivity of the catalyst in acetylene hydrogenation, which is caused by the interaction between the oxides and the Pd surface similar to the case of the oxide-supported catalysts. It has been confirmed through experiments that metal oxides spread on and modify both geometrically and electronically the Pd surface after the catalyst is reduced at 500°C. Such a behavior of metal oxides in the catalyst is correlated well with their promotional effect on the catalyst performance. That is, the oxides on the Pd surface retard the sintering of the dispersed Pd particles, suppress the adsorption of ethylene in the multiply-bound mode, and facilitate the desorption of ethylene produced by acetylene hydrogenation. Among the three metal oxides examined in this study, Ti oxide is found to have the most promotional effect.

光電子放射測定による金属の初期酸化挙動の研究

光電子放射測定による金属の初期酸化挙動の研究

On some aspects of low-temperature and anodic oxidation of metals and semiconductors

Recent ideas of Fehlner and Mott on low-temperature oxidation, both thermal and anodic, are examined with regard to the magnitudes of metal-metal and metal-oxygen bond strengths and their involvment in the interpretations of oxidation behavior of metals and semiconductors. It is pointed out that the magnitudes of bond strengths used by them appear to be inconsistent with the estimates of other workers based on well-established procedures. Some possible consequences of the reevaluated M-M and M-O bond strengths as regards the oxidation characteristics of metals are briefly mentioned. Also discussed is the influence of the estimated semiconductivity of anodization oxides on the subsequent anodic behavior of these metals.

Oxidation behaviour of metal at its allotropic transformation temperature

Oxidation behaviour of metal at its allotropic transformation temperature

The role of oxide plasticity on the oxidation behavior of metals: A review

The role of oxide plasticity on the oxidation behavior of metals: A review

High Pressure Oxidation of Metals: Oxidation of Metals Under Conditions of a Linear Temperature Increase

The oxidation behavior of metals was studied by subjecting the metal sample to a linear temperature increase at constant oxygen pressure. The advantages of this method over previous isothermal methods are that (a) a rapid preliminary examination of the oxidation behavior of any metal or alloy over a desired temperature and pressure range can be made quickly, (6) the region of pressure dependence usually can be found in a single experiment, (c) the number of samples needed is greatly reduced, and (d) the method serves as a guide for isothermal measurements at constant pressure.The linear temperature increase method was applied to Ta, Nb, Mo, Cu, Zr, Mg, Ti, and W. Results are in good agreement with those of previous investigations made in this laboratory.Theoretical considerations show that the results could be explained by imposing the conditions of a linear temperature increase on a general type rate equation.