Effect Of Cobalt Oxide Research Articles

Effect of cobalt oxide on characteristics of micro‐arc oxidation coatings on TC11 alloy

AbstractIn order to improve the comprehensive performance of TC11 titanium alloy and make it more widely used in the field of oil and gas wells, cobalt oxide micro‐powder from 0 to 0.8 g·L−1 was added in the electrolyte. The effects of cobalt oxide micro‐powder concentration on properties of micro‐arc oxidation (MAO) coatings were analyzed by scanning electron microscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, and electrochemical workstation. With cobalt oxide micro‐powder increased, the oxide voltage increased, and the discharge coating micropores became more uniform. The increase in thickness and hardness also improved corrosion resistance. The comprehensive performance after added 0.6 g·L−1 of cobalt oxide was the best, with a doubling increase in thickness and hardness, reaching 32.1 µm and 721.2 HV, respectively. The corrosion rate reduced to 4.19 × 10−10 mm·a−1, which reduced by three orders of magnitude. In addition, the substrates and samples prepared with 0.6 g·L−1 cobalt oxidation were used for the erosion corrosion tests in different NaCl solutions, and it was found that the weight loss and rate of the MAO sample (slight corrosion) were lower than substrates, indicating that the cobalt oxide doped coatings had better corrosion resistance.

Effect of Cobalt Oxides on the Catalytic Combustion of Odor.

The catalytic combustion of acetaldehyde was studied using various types of Co oxides and Co-PC. The Co oxides and Co-PC were characterized using an X-ray diffractometer (XRD), X-ray photo-electron spectroscopy (XPS), and a particle sizing analyzer. The Co-PC and CoO were converted into Co₃O₄ under an air atmosphere at 450 °C, and the results were confirmed using the XRD and XPS. According to the pretreatment of the Co-PC and Co oxides, the conversion of acetaldehyde increased. The order of particle size for both fresh and pretreated samples is summarized as follows: CoO < Co-PC < Co3O4 powder < Co₃O₄ (99.995%). For all samples, acetaldehyde was not observed at temperatures above 320 °C owing to complete combustion. The conversion of acetaldehyde in the samples was affected by the fresh state of the Co oxides and the space velocity. The catalytic activity depended on the chemical state of the Co oxides and the surface concentrations of Co, O, and N.

P-CoOx/n-SnO2 nanostructures: New highly selective materials for H2S detection

Nanostructures p-CoOx/n-SnO2 based on tin oxide nanowires have been prepared by two step CVD technique and characterized in detail by XRD, XRF, XPS, HAADF-STEM imaging and EDX-STEM mapping. Depending on the temperature of decomposition of cobalt complex during the second step of CVD synthesis of nanostructures cobalt oxide forms a coating and/or isolated nanoparticles on SnO2 nanowire surface. It was found that cobalt presents in +2 and +3 oxidation states. The measurements of gas sensor properties have been carried out during exposure to CO (14ppm), NH3 (21ppm), and H2S (2ppm) in dry air. The opposite trends were observed in the effect of cobalt oxide on the SnO2 gas sensitivity when detecting CO or NH3 in comparison to H2S. The decrease of sensor signal toward CO and NH3 was attributed to high catalytic activity of Co3O4 in oxidation of these gases. Contrary, the significant increase of sensor signal in the presence of H2S was attributed to the formation of metallic cobalt sulfide and removal of the barrier between p-CoOx and n-SnO2. This effect provides an excellent selectivity of p-CoOx/n-SnO2 nanostructures in H2S detection.

Effect of cobalt oxides on heat transfer property of peritectic steel mould flux

During the solidification of peritectic steels (PS), the peritectic reaction causes volume contraction which is associated with surface longitudinal cracks. Therefore much research has been focused on deceasing the heat transfer properties of PS mould flux. In this work Co2O3 was successfully added to PS mould flux and the optimal content was found to be 2·0 wt-% and that Co doping could decrease the heat flux density of the flux. The structures, composition and colour properties of the samples were characterised by SEM, EDS, EPMA, XRD and CIE.

Effect of cobalt oxide on performance of Pd catalysts for lean-burn natural gas vehicles in the presence and absence of water vapor

Pd-based catalysts modified by cobalt were prepared by co-impregnation and sequential impregnation methods, and characterized by X-ray powder diffraction (XRD), N 2 adsorption/desorption (Brunauer-Emmet-Teller method), CO-chemisorption and X-ray photoelectron spectroscopy (XPS). The activity of Pd catalysts was tested in the simulated exhaust gas from lean-burn natural gas vehicles. The effect of Co on the performance of water poisoning resistance for Pd catalysts was estimated in the simulated exhaust gas with and without the presence of water vapor. It was found that the effect of Co significantly depended on the preparation process. PdCo/La-Al 2O 3 catalyst prepared by co-impregnation exhibited better water-resistant performance. The results of XPS indicated that both CoAl 2O 4 and Co 3O 4 were present in the Pd catalysts modified by Co. For the catalyst prepared by sequential impregnation method, the ratio of CoAl 2O 4/Co 3O 4 was higher than that of the catalyst prepared by co-impregnation method. It could be concluded that Co 3O 4 played an important role in improving water-resistant performance.

Effect of cobalt oxide on the sintering and grain growth of Al2O3-YAG composite nanopowder

In the present study, the effect of cobalt oxide on the densification of Al2O3-YAG composite nanopowder was investigated. An amorphous nanopowder was synthesized and crystallized to Al2O3-YAG after heat-treatment via a solid-state reaction. The average particle size of heat-treated powder at 800?C was about 80 nm. Cobalt oxide improved the sintering rate of Al2O3-YAG composite nanopowders and promoted grain boundary mobility. Cobalt oxide doping increased the ratio of densification/grain growth rate. The activation energy for grain growth decreased from 590 to 485 kJ/mol by adding cobalt oxide to the composite nanopowder.

The effect of cobalt oxide on zinc oxide in a new anticorrosive green pigment

Purpose – Aims to study inhibitive properties of new compounds that are based on the Wurtzite structure of zinc oxide with an admixture of cobalt using zinc oxide as a reference.Design/methodology/approach – The conditions for the preparation of pigments using different ratios of both cobalt and zinc were investigated. Characterization of these pigments was carried out using spectroscopic methods of analysis via X‐ray diffraction, transmission and scanning electron microscopy. Also, evaluations of the pigments prepared, in terms of oil absorption, specific gravity, water‐soluble matter and pH, using international standard testing methods was performed. The pigments prepared were incorporated in anticorrosive paint formulations based on medium oil alkyd resin as a binder. The physico‐mechanical properties of the relevant paint films were obtained, while their anticorrosive properties were assessed by tests in 3.5 percent NaCl solution for 28 days. Electrochemical measurements based on corrosion rates of pa...

Effect of cobalt oxide on the densification of yttrium aluminum garnet

The solid state sintering of yttrium aluminum garnet (YAG) without any additive at 1873 K could not be achieved beyond 90% of theoretical density. Higher temperature was not tried to avoid abnormal grain growth in the material. To densify further, cobalt nitrate was added to alumina–yttria stoichiometric mixture in various proportion by solution infiltration method. The samples were sintered at 1873 K in air to achieve full density. The as-sintered microstructure revealed no abnormal grain growth.

Nonlinear electrical properties of cobalt doped SnO2·Ni2O3·Nb2O5varistors

A new varistor system of SnO 2 ·Ni 2 O 3 ·Nb 2 O 5 exhibits the relative dissatisfactory physical and electrical properties. The effect of cobalt oxide on the properties of the SnO 2 ·Ni 2 O 3 ·Nb 2 O 5 varistors was investigated by measuring the densities, permittivities, the current-voltage properties and the properties of the defect barriers. It is found that the sample doped with 0.25 mol% Co 2 O 3 exhibits the abnormal poorer electrical properties than the samples without Co 2 O 3 dopants. However, the sample doped with 6.0 mol% Co 2 O 3 exhibits the highest nonlinear coefficient ( $\alpha=17.24$ ) and reference electrical field ( $E_{\rm B}=561$ V/mm), although the sample doped with 1.0 mol% Co 2 O 3 exhibits the highest densities ( $\rho =6.87$ g/cm 3 ) and permittivities. The sample with 6.0 mol% Co 2 O 3 bears the highest barriers, but the sample with 1.0 mol% Co 2 O 3 shows the narrowest barriers. The investigation of the sintering temperature shows that the samples sintered at 1450 °C exhibit the better physical and electrical properties. The results were discussed and the defect barrier model was also introduced to explain.

Effect of cobalt oxide on surface structure of alumina supported molybdena catalysts studied by in situ Raman spectroscopy

A set of Co promoted 10% Mo/Al2O3 samples have been characterized by means of Raman spectroscopy under ambient as well as in situ dehydrated conditions. Under ambient conditions, the degree of the polymerization of surface molybdenum oxide species decreases with increasing Co loading. Under dehydrated conditions, the polymeric molybdenum oxide species is absent with the addition of only 0.2% Co. At low Co loadings (⩽2%), before the formation of CoMoO4 compound, the spectral features are very similar under ambient conditions. Dehydration causes the upward shift of the Mo=O symmetric stretching mode. A broad band around 920–930 cm−1 was thus observed. This band has been suggested to be associated with the Co-Mo interaction species. In contrast to crystalline CoMoO4, this species shows a reversibility on H2 reduction-O2 reoxidation treatments. From the results obtained, it is proposed that cobalt oxide interacts with the most polymerized molybdenum oxide species to form Co-Mo interaction species and/or crystalline CoMoO4; therefore, the amount of the surface molybdenum oxide species decreases with a change in the molecular structure as a function of the Co concentration.

Effect of cobalt oxide on the a.c. conduction mechanism of copper tellurite glasses

Electrical measurements on binary and ternary glasses of compositions 65TeO2-35CuO and 65TeO2-34CuO-1CoO (mol%) are reported at temperatures between 293–458 K in the frequency range up to 10−6 Hz. The measured conductivity shows a frequency dependence obeying the equation σ(ω) =Aωs withs <1 but taking different values at different temperatures. The capacitance of the glasses shows an increase in value with increase in temperature at low frequencies. The tangent of the loss angle (tan δ) and dielectric loss factor ɛr″were found to increase with the increase in temperature and decrease in frequency but the usual Debye loss peaks were absent even at high temperatures. The relative dielectric constant ɛr was unexpectedly high, approximately 103, and was found to decrease very slightly with increasing frequency. Overall the effect of a small amount of CoO (a 1 mol%) is found to have a dominant effect on the dielectric properties of copper tellurite glasses.

Effect of cobalt oxide on the structure and phase constitution of the zirconium-bearing materials

This paper presents results of a study to determine the effects of cobalt oxide doping on the lattice parameters and microstructure of a zirconium oxide-yttrium oxide solid solution. Phase and structure data were obtained by x-ray diffraction. Results for grain size and lattice parameters prior to and after doping are tabulated and the effect of the cobalt oxide on the sinterability of the final product is assessed.

Effect of Cobalt Oxide in Porous Nickel Ferrites at Very High Frequency

Very high frequency measurements of a series of porous, low-loss ferrites (NiO(1−x)CoOxFe2O2) are described. In many cases, a resonance-type dispersion appears. Comparison of the data with theory indicates that the dispersion results not from domain rotation but from high-frequency wall resonance. Extrapolation of the data for x = 0 to theoretical density gives results which are consistent with single-crystal measurements suggesting that the loss in porous nickel ferrite occurs in small, relatively perfect regions or grains.