Increase Of Co Content Research Articles

Вплив препарату «Шумерське срібло» на життєздатність медоносних бджіл та вміст окремих мікроелементів в їх організмі

Вплив препарату «Шумерське срібло» на життєздатність медоносних бджіл та вміст окремих мікроелементів в їх організмі

Ammonia-free synthesis of Mo/CoMgAl catalysts with excellent activities in water-gas shift reaction

A series of CoMgAl mixed oxides with homogeneous Co dispersion were prepared using co-precipitation method. The CoMgAl composites were then doped with Mo species, giving Mo/Co(x)MgAl (x=Co/(Co+Mg)) catalysts for water-gas shift reaction (WGSR). In the synthesis of these catalysts, there is limited release of ammonia, which is traditionally common in the generation of Mo-Co catalysts for WGSR. The Mo/Co(x)MgAl catalysts were characterized using techniques such as XRD, N2-physisorption, H2-TPR, H2S-TPS, Raman, HRTEM and XPS. It is noted that the Mo/Co(5%)MgAl catalyst gives 91.2% CO conversion at 350 °C, which is close to the equilibrium CO conversion (91.7%). The H2S-TPS results disclose that there is decrease in activation energy for Mo sulfidation with increase of Co content in Mo/Co(x)MgAl, indicating the presence of Co promotes Mo sulfidation. The outcomes of HRTEM and XPS analyses reveal that the role of Co is to decrease stacking number and slab length of MoS2 moieties. The EDX elemental analysis suggests synergism between Co and MoS2, especially in the case of Mo/Co(5%)MgAl. With the formation of small-size MoS2 slabs and enhanced Co-MoS2 synergistic effect, the Mo/Co(5%)MgAl catalyst has high exposure of active sites, leading to improved catalytic activities in WGSR.

Dilute magnetic semiconductor of ZnCoSe thin films: Structural, optical, and magnetic characteristics

AbstractA series of Zn1−xCoxSe (x = 0, 0.025, 0.050, 0.075, and 0.100) films using were evaporated (thickness of 1 μm) using electron beam gun. The effect of Co doping on the structural, optical, and magnetic properties has been investigated. X‐ray diffraction studies confirm formation of zinc blend structure for all Zn1−xCoxSe films. The crystallite size increases and the lattice strain decreases with the increase in Co content. The elemental constituents were characterized by energy dispersive X‐ray. Optical studies showed an increase in refractive index and a decrease in energy gap with the increase in the cobalt doping. The dispersion of the refractive index has been analyzed in terms of the Wemple‐DiDomenico single oscillator model. The oscillator parameters including the single oscillator energy (Eo), the dispersion energy (Ed), and the static refractive index (n0) were estimated. Magnetization measurements via vibrating sample magnetometer showed a hysteresis loop and confirmed room‐temperature ferromagnetism in Co‐doped ZnSe films.

Codeposition of Nanocrystalline Co-Ni Catalyst Based on 1-ethyl-3-methylimidazolium Bisulfate and Ethylene Glycol System for Hydrogen Evolution Reaction

The codeposition behavior of Co(II) and Ni(II) in 1-ethyl-3-methylimidazolium bisulfate ([EMIM]HSO4) ionic liquid (IL) and ethylene glycol (EG) system is recorded using cyclic voltammetry (CV). The result indicates that the mechanism of Co-Ni codeposition is an anomalous codeposition, and both the inhibition for Ni(II) reduction and the anomalous codeposition phenomena can be improved by the increase of Co(II) concentration in the system. These Co-Ni deposits are characterized using EDS, XRD and SEM. SEM micrographs indicate that the surface morphology of Co-Ni deposits can be changed by the increase of Co content, and these deposits with many additional elongated acerose crystals, which are germinated on the spherical “nodules” surface, can be prepared. XRD pattern reveals the feature peak of crystalline Co1.2Ni2.8 with a preferred orientation direction and the average size of grains is calculated to be about 14.6 nm. Moreover, the electrocatalytic activity for hydrogen evolution reaction (HER) on the prepared Co-Ni catalyst surface is investigated using linear sweep voltammetry (LSV) and electrochemical impedance spectra (EIS). These results indicate that the obtained catalyst presents an excellent electrocatalytic activity and durability for HER with an overpotential of 139 mV at 10 mA cm−2 in 1 M KOH solution.

Tensile mechanical performance of Ni-Co alloy nanowires by molecular dynamics simulation.

In this present contribution, tensile mechanical properties of Ni–Co alloy nanowires with Co content from 0 to 20% were studied by molecular dynamics. The simulation results show the alloy nanowire with the Co content of 5% has the highest yield value of 9.72 GPa. In addition, more Frank dislocations were generated during the loading process to improve the performance of the alloy nanowire. The Young's modulus increases little by little from 105.68 to 179.78 GPa with the increase of Co content. Secondly, with the increase of temperature, the yield strength gradually decreases to 2.13 GPa. Young's modulus tends to decrease linearly from 170.7 GPa to 48.21 GPa. At the temperatures of 500 K and 700 K, it is easier to form Frank dislocation and Hirth dislocation, respectively, in the loading process. The peak value of the radial distribution function decreases and the number of peaks decreases, indicating the disappearance of the ordered structure. Finally, after the introduction of the surface and inner void, the yield strength of the nanowire drops about to 8.97 and 6.6 GPa, respectively, and the yield strains drop to 0.056 and 0.043. In the case of the existence of internal void, perfect dislocation and Hirth dislocation can be observed in the structure.

Electrochemical properties and microstructure of Pb-Co anodes during electrolysis in H2SO4 solution

The Pb-Co anodes were prepared by hot press and the parameters of oxygen evolution dynamics of Pb-Co anodes were analyzed by Double-Slope Tafel, Cyclic Voltammograms and EIS carried out in 2 molL-1 H2SO4 solution. The results showed that with an increase Co content the OER over-potentials η of Pb-1%Co and Pb-2%Co anodes increase at 48 h of electrolysis but then decrease at 96 h of electrolysis when the passivation react. With an increase of Co content the corrosion current density icorr of Pb-Co anodes increase at 96 h of electrolysis, which revealed the formation process on the anodic layers of Pb-Co anodes at 96 h of electrolysis. The phase transformation and microstructure change were measured by XRD analysis and SEM observations. At 48 h of electrolysis, the anodic layers determined with orthorhombic crystals of α-PbO2. At 96 h of electrolysis, the anodic layers were mainly composed of tetragonal crystals of β-PbO2 phase, probably. It's obvious that the CoS2 phase appears on the anodic layer of Pb-3%Co anodes at 96 h of electrolysis in 2 molL-1 H2SO4 solution.

A further investigation on the MnO2-Fe2O3 system roasted under CO-CO2 atmosphere

Investigations on the MnO2-Fe2O3 system roasted in air has been reported in our previous work. This study further investigated the MnO2-Fe2O3 system roasted under CO-CO2 atmosphere. Extensive investigations were concentrated on the reduction of simplex iron oxides or manganese oxides, and little attention were paid on the reduction of MnO2-Fe2O3 system regarding to interactive reactions between them. In this work, it was found that spinel-type MnxFe3−xO4 with high magnetism formed easily under CO-CO2 atmosphere. The reduction and thermodynamic analyses of pure MnFe2O4 were also researched to better understand the reduction behaviors of MnO2-Fe2O3 system. Phase study showed that a series of Mn-Fe composite oxides, including MnxFe3−xO4 and (MnO)y(FeO)1−y, generated during the reduction of MnO2-Fe2O3 system. MnxFe3−xO4 was readily generated under CO content of 2.5–25 vol% at 1000 °C. With further increase of CO content, MnxFe3−xO4 was reduced to (MnO)y(FeO)1−y and then to MnO and metallic iron. Reduction of manganese oxides, iron oxides and manganese ferrites happened concurrently during the reduction of MnO2-Fe2O3 system. And the reduction of MnO2, Fe2O3, Fe3O4 and MnFe2O4 were compared by TG and thermodynamic analyses. In addition, the morphology evolution and magnetism change of the MnO2-Fe2O3 system reduced under different CO contents were also studied.

New insights on the co-electrolysis of CO2 and H2O through a solid oxide electrolyser operating at intermediate temperatures

A solid oxide electrolyser cell based on a Ni-yttria-stabilized zirconia (Ni-YSZ) supporting cathode, a double layer YSZ and Gadolinia-doped Ceria (GDC) electrolyte and a strontium doped lanthanum cobaltite anode (LSC) was investigated for the co-electrolysis of H2O and CO2 in the range of temperatures between 525 °C and 700 °C. The flow rate of the inlet stream was selected in order to reproduce practical operating conditions conventionally adopted for solid oxide electrolysis stacks. The flow of CO2 and H2O, was 2 times of that required by the faradaic reaction at high current densities in order to achieve an utilization close to 50%. A steady-state galvanostatic operating mode was selected in combination with the analysis of the effluents by gas-chromatography. Electrochemical studies also included electrochemical impedance spectroscopy (EIS) and polarization curves. The results showed an increase of CO content versus H2 in the formed syngas promoted by the increase of temperature. A small occurrence of methane was observed at 525 °C. The post operation analysis of the spent cell excluded the presence of carbon but it showed a fracture occurring in the cell at the interface cathode-electrolyte possibly as consequence of the re-oxidation of the cathode at the high operating temperatures. Such evidence suggests that an improvement of cell microstructure for high temperature solid oxide electrolysis is required.

Microstructure and Magnetic Properties of Ba0.95Y0.05Fe12−xCoxO19 Hexaferrites

Magnetoplumbite-type (M-type) barium ferrites doped with different Y–Co doping content Ba0.95Y0.05Fe12−xCoxO19 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5) were successfully prepared by ceramic process and investigated in this paper for the first time. X-ray diffraction were used to analyze the phase of the prepared sample. The scanning electron microscopy (SEM) was used to measure the morphology, and magnetic properties were measured by vibrating sample magnetometer (VSM). The results of XRD show that the single phase of M-type barium ferrites was obtained with the increase of Co content (x), but α-Fe2O3 occurred when x exceeds 0.3. The SEM results exhibit the uniform plane hexagonal structures of M-type ferrites with all range of Co doping content. VSM results display that magnetization (Ms) and coercivity (Hc) show the same tendency that their values first increase and then decrease with the increase of Co content.

Effect of composition, heat treatment and deformation on mechanical properties of tungsten heavy alloys

Five different compositions of tungsten heavy alloy with Ni, Fe, Co and Mo were prepared through powder metallurgy route using liquid phase sintering. Three alloys were based on quaternary W-Ni-Fe-Co (with varying Ni to Fe ratio and Co content) and the other two quinary systems with Mo addition. The sintered alloy blanks (cylindrical cross section) were subjected to a thermo-mechanical treatment, which comprised three vacuum heat treatments (at 1100 °C for 1.5 h followed by oil quenching) before and in between multiple swaging operations (at 500 °C) with a total deformation of 53%. This was followed by a detailed evaluation of different microstructural parameters in all compositions. Mechanical properties such as tensile strength, % elongation and impact were evaluated at the final stage (26 mm dia and 600 mm length). Increase in Co content resulted in better strength and elongation with marginal loss in impact values. The alloy containing 0.25 wt% Mo showed the best combination of tensile and impact properties. Further increase in Mo concentration to 0.5 wt% resulted in marginal increase in strength value but rapid deterioration in elongation and impact values. Scanning electron microscopy, electron probe micro analysis, quantitative metallography and fractography were carried out to establish an inter-relationship between microstructure, properties and fracture behaviour of the alloys investigated.

Composition-tunable Ni1−xCox nanotubes: Template synthesis, magnetic properties, and catalytic activities for the reduction of 4-nitrophenol

Ni1−xCox (0 ≤ x ≤ 1) nanotubes with outer diameters of 180–210 nm were quickly fabricated by a facile template-assisted chemical deposition method. Their microstructures, magnetic properties and catalytic activities for the reduction of 4-nitrophenol were studied. The results showed that the as-obtained boron-doped transition-metals had uniform size, noncrystalline structure and typical hollow tube-like morphologies. The content of Ni and Co in the nanotubes can be easily adjusted by changing the Ni2+/Co2+ ratios in the solution used for the co-deposition process. Except for the similar coercive force (Hc), their saturation magnetization (Ms) and remanent magnetization (Mr) increased with the increase of Co content. In addition, all of the metal nanotubes presented good catalytic performances for the reduction of 4-nitrophenol (4-NP). The catalytic efficiencies gradually became better in the order of Ni, NiCo, NiCo2 and Co.

An experimental investigation on wear and corrosion characteristics of Mg-Co nanocomposites

In this research, Mg-Co nanocomposites were synthesized using powder metallurgy process. The impact of Co nanoparticle reinforcements on the hardness, wear and corrosion characteristics of Mg-Co nanocomposites were investigated. The dry sliding wear of the Mg-Co nanocomposites was examined using pin-on-disc apparatus under various loading conditions. The results substantiate that the hardness (70 HV) and wear resistance of Mg-25Co were higher than pure Mg (25 HV). The morphological analysis of Mg-based nanocomposites has been carried out using Scanning Electron Microscope and Atomic Force Microscope. The electrochemical corrosion analysis reveals that the increase in Co content in Mg matrix decreases the corrosion rate. The Mg-25Co nanocomposites shows better corrosion resistance (Icorr = 0.397 × 10−3 μA cm−2) than that of Pure Mg (Icorr = 0.544 × 10−3 μA cm−2). An increase in Polarization resistance (RP) also authenticates the increase in corrosion resistance of Mg-25Co nanocomposites. The EIS spectroscopy results reveal that the charge transfer resistance (Rct) has enhanced from 14.44 Ω cm2 for the pure Mg to 42.50 Ω cm2 for the Mg-25Co nanocomposites.

Microwave assisted hydrothermal synthesis of (Fe,Co)3O4 nanoparticles in the presence of surfactants and effects of Co/Fe ratio on microstructure and magnetism

Microstructure and magnetic properties of nanoparticles can be tailored by optimising the synthesis procedure and changing chemical composition. In this study, a two-step procedure, i.e., coprecipitation in the presence of PEG 300 followed by microwave assisted (MW) hydrothermal synthesis, was introduced to obtain CoxFe3-xO4 (x = 0, 0.1 and 0.2) nanoparticles. It was found that with the increase of Co content, particle/crystallite size increased, with significant change of coercivity (Hc). The mixed samples of CoxFe3-xO4 (x = 0.1 and 0.2) were magnetically harder in comparison with Fe3O4. Тhe Hc of Fe3O4 was 91 Oe, while for Co0.10Fe2.90O4 and Co0.20Fe2.80O4, Hc was 256 Oe and 1070 Oe, respectively. Saturation magnetisation (Ms) of mixed samples also increased up to 6% compared to Fe3O4. A special effort was devoted to study the effects of introducing different surfactants (PEG 300, PEG 4000 or SDS) during the synthesis procedure in order to improve morphological and microstructural properties of CoFe2O4 nanoparticles. The influence of surfactants on physical/chemical properties of nanoparticles is discussed.

Effects of cobalt content on the decolorization properties of Fe-Si-B amorphous alloys

Abstract This research attempts to study the effects of Co addition on the decolorization properties of Fe-Si-B amorphous alloys. It was found that Fe-Co-Si-B glassy ribbons (GRs) with different cobalt contents could all decolorize acid orange II (AO) solution through adsorption or reductive degradation no matter at lower or higher temperatures. When Co content was low (10 at.%), Fe-Co-Si-B GRs showed similar decolorization properties to those of Fe-Si-B GRs. With the increase of Co content, reductive degradation of AO by the GRs was not detected basically at lower temperature, and Fe-Co-Si-B GRs could decolorize AO solution only through adsorption; at higher temperature, reductive degradation contributed a lot to the decolorization of AO solution, but adsorption effects still played an important role in the decolorization process. The higher the Co content in the glassy ribbons, the more prominent the adsorption effects, and the more time required to activate reductive degradation of dye molecules. The effects of Co addition on the decolorization properties of Fe-Si-B amorphous alloys are considered to be attributed to the compound effects of zero-valent iron atoms and zero-valent cobalt atoms in the GRs.

Effects of Cobalt on the structure and mechanical behavior of non-equal molar CoxFe50−xCr25Ni25 high entropy alloys

Non-equal molar high entropy alloys (HEAs) are promising to obtain better mechanical properties owing to abundant composition designs compared with single equal molar HEAs point. CoxFe50−xCr25Ni25 HEAs were designed to investigate the effect of Co compositional variation on the structure and mechanical properties of single phase solid solutions. Microstructure evolution at different strain levels was studied by electron backscatter diffraction. The results indicate that lattice parameter tends to decrease and yield strength are enhanced, with the increase of Co content. The ultimate tensile strength and ductility are improved at Co 30–35 at%, especially the ductility, compared to the equal molar CoCrFeNi HEAs. Meanwhile, grain rotation is slower and more difficult in non-equal molar Co35Fe15, and the greater low angle boundary fraction indicates the higher dislocation density. In different deformation stages, the dislocation forest strengthening and twinning-induced plasticity effect result in better strength-ductility combination in Co35Fe15.

Superparamagnetic behavior of MOCVD grown ZnO:Co films

Temperature and field dependences of magnetization have been measured for Co-doped ZnO films with different Co content grown by MOCVD on sapphire substrates. Measured field dependences of magnetization show ferromagnetic-like hysteresis loops and paramagnetic contribution. Coercive field decreases with an increase of Co content and temperature. The difference between temperature dependences of magnetization measured in zero field cooling and field cooling conditions was observed in the temperature range from 2 K to 300 K indicating superparamagnetic behaviour of the films. The distribution of blocking temperatures extracted from the temperature dependences of magnetization is broad and shifts to the low blocking temperatures with an increase of Co content

The co-doping effects of Zr and Co on structure and electrochemical properties of LiFePO4 cathode materials

In this work, the band conduction mechanism of Zr and Co co-doped LiFePO4 is studied by a first-principle calculation, which demonstrates Zr, Co co-doping can decrease the band gap of LiFePO4 indicating the electrochemical properties can be improved by Zr and Co co-doping. The pristine LiFePO4 and Li0.99Zr0.0025Fe1-xCoxPO4 (x = 0.005, 0.01, 0.015, 0.02) cathode materials are synthesized by a conventional high-temperature solid-state method. All the samples exhibit a highly crystallized olivine structure of LiFePO4, which demonstrates Zr and Co co-doping does not destroy the olivine structure. A small amount of Co and Zr co-doping can modify the morphology of LiFePO4 cathode. Combining the improved structure with the modified particle morphology, the co-doped Li0.99Zr0.0025Fe1-xCoxPO4 cathodes exhibit the enhanced electrochemical performance. The rate capacity and cycle stability of Li0.99Zr0.0025Fe1-xCoxPO4 cathodes enhanced with the Co content and reached the largest values at x = 0.01, then decreased with the further increase of Co content. The Li0.99Zr0.0025Fe0.99Co0.01PO4 composites show the best rate capability and cycle stability, which have a discharge capacity of 139.9 mAh/g at 0.1 C with a capacity retention ratio of 85% after 50 cycles. The calculated results indicate that the Zr and Co co-doped LiFePO4 have a low lithium ion diffusion energy barrier and high lithium ion diffusion coefficient, which attributes to the enhanced electrochemical performance.

Influence of cobalt content and HVOF deposition process on the cavitation erosion resistance of WC-Co coatings

Cavitation is a wear process that occurs in aqueous environments in which water vapor bubbles on the metal surface of a component implode, leading to erosion. The phenomenon can cause significant damage to structural metal alloys, and many components are therefore covered with coatings to protect against this damage. Thermal spray coatings have long been used for this purpose. With the advent of the HVOF (high velocity oxy-fuel) spray process it became possible to produce denser, harder, tougher coatings, which can be used in applications where fracture toughness is more important. Among the materials most frequently used, tungsten carbide-cobalt (WC-Co) cermet coatings offer a combination of high hardness, toughness and adherence and consequent wear resistance. In this work, two WC cermets with different Co (binder) contents were used to investigate the influence of Co content on the fracture toughness and cavitation resistance of WC coatings deposited by the HVOF process using different fuels. The influence of the HVOF process (specifically the type of fuel used) on the residual stresses in these coatings and their microstructure and properties was also studied. An increase in Co content led to an increase in the fracture toughness and cavitation resistance of the coatings. The primary wear mechanism appears to involve carbide particles becoming detached from the Co matrix. The greater compressive residual stress when liquid fuel was used in the HVOF process resulted in improved properties, including fracture toughness, and a concomitant improvement in cavitation resistance.

Effect of Cobalt on Microstructure and Wear Resistance of Ni-Based Alloy Coating Fabricated by Laser Cladding

Ni-based alloy powders with different contents of cobalt (Co) have been deposited on a 42CrMo steel substrate surface using a fiber laser. The effects of Co content on the microstructure, composition, hardness, and wear properties of the claddings were studied by scanning electron microscopy (SEM), an electron probe microanalyzer (EPMA), X-ray diffraction (XRD), a hardness tester, and a wear tester. The results show that the phases in the cladding layers are mainly γ, M7(C, B)3, M23(C, B)6, and M2B. With the increase in Co content, the amounts of M7(C, B)3, M23(C, B)6, and M2B gradually decrease, and the width of the eutectic structure in the cladding layer also gradually decreases. The microhardness decreases but the wear resistance of the cladding layer gradually improves with the increase of Co content. The wear resistance of the NiCo30 cladding layer is 3.6 times that of the NiCo00 cladding layer. With the increase of Co content, the wear mechanism of the cladding layer is changed from abrasive wear to adhesive wear.

Secondary hardening behavior in ausformed martensitic alloys with different Co content

The influence of Co addition on the secondary hardening behavior in ausformed high Co-Ni secondary hardening alloy steels was analyzed using small-angle neutron scattering and differential scanning calorimetry coupled with a modified Johnson-Mehl-Avrami kinetic model. In severely ausformed alloy steels, an increase in Co content increased the degree of secondary hardening but did not accelerate their aging kinetics. This was determined by Co-independent cementite precipitation, thus leading to the precipitation of M2C carbide nucleated around and/or on cementite during the same aging time of 5 h.