Different Contents Of Co Research Articles

Hierarchical waxberry-like V2O3@Co/Co3O4/Ni absorbers with remarkable microwave absorption via regulation of magnetic and dielectric loss

The design of microwave absorbers with hierarchical architectures are garnering increasing attention, but the regulation of the dielectric/magnetic loss remains a challenge. Herein, waxberry-like V2O3@Co/Co3O4/Ni (VCN-x) absorbers are fabricated by hydrothermal and annealing process, with magnetic Co/Co3O4/Ni uniformly riveted on the surface of V2O3 microspheres. The morphological evolution of Co/Co3O4/Ni, including nanoparticles, nanosheets, and nanoflowers, was modified by introducing different content of Co and Ni particles. This enrichment the multiple heterogeneous interfaces leads to an enhancement in interfacial polarization. This enhancement is attributed to the internal core-double shell structure, abundant intrinsic defects, and multiple interfaces, VCN-x absorbers exhibit remarkable microwave absorption (MA) performance and a broad effective absorption band (EAB). The enrichment of multiple heterogeneous interfaces leads to an enhancement in interfacial polarization. This enhancement is attributed to the internal core-double shell structure, the presence of abundant intrinsic defects, and the existence of multiple interfaces within VCN-x absorbers. As a result of these structural characteristics, VCN-x absorbers demonstrate exceptional MA performance and exhibit a broad EAB. At a thickness of 2.26 mm, the minimum reflection loss (RLmin) is −59.6 dB. By varying the matching thickness between 1.60 mm and 2.26 mm and by adjusting the EAB from 3.8 GHz to 6.8 GHz, the EAB of VCN-x absorbers can encompass the CKu band.

Controlled Oxidation of Cobalt Nanoparticles to Obtain Co/CoO/Co3O4 Composites with Different Co Content.

The paper studies patterns of interaction of electroexplosive Co nanoparticles with air oxygen during heating. The characteristics of Co nanoparticles and composite Co/CoO/Co3O4 nanoparticles formed as a result of oxidation were studied using transmission electron microscopy, X-ray phase analysis, thermogravimetric analysis, differential scanning calorimetry, and vibrating sample magnetometry. It was established that nanoparticles with similar morphology in the form of hollow spheres with different content of Co, CoO, and Co3O4 can be produced by varying oxidation temperatures. The influence of the composition of composite nanoparticles on their magnetic characteristics is shown.

Co-doped amorphous MoSx supported on CuO/CM (Cu mesh) with enhanced photocatalytic activity for ammonia synthesis

As one of the world's most significant industrial synthetic chemicals, ammonia has critical applications in many fields. Mo-based catalyst has an excellent effect on photocatalytic nitrogen fixation. Compared with crystalline molybdenum sulfide, low crystalline or amorphous molybdenum sulfide has rich unsaturated defects to improve the photocatalytic activity. Therefore, we used CuO/CM (Cu mesh) as the substrate and a simple electrochemical deposition method to load amorphous MoSx doped with different contents of Co on CuO/CM and successfully synthesized a thin film heterojunction photocatalyst. At the same time, we fabricated a gas-liquid-solid three-phase photocatalytic reactor to evaluate the catalytic activity of the catalyst. Compared with the powder catalyst reported in the literature, because the catalytic reaction of the three-phase gas-liquid-solid three-phase reactor occurs at the gas-liquid interface, the film catalyst can also absorb sufficient N2 in the gas phase while contacting the liquid proton source (water). It can effectively enhance photocatalytic nitrogen fixation efficiency. The constructed film photocatalyst showed good photocatalytic performance and stable structure under the 350 W simulated light source. While exploring the catalyst structure, the photocatalytic effect of the catalyst was evaluated. When the molar ratio of Mo and Co is 1:0.9, the photocatalyst efficiency shows the high photocatalysis at a rate of 1.062 mg·L−1 for 4 h. Compared with pure CuO / CM and MoSx / CuO / CM, the NH3 yield of the catalyst was increased by 7.86 and 7.52 times, respectively. In addition to N2, no other N sources were introduced during the reaction, which ensured the accuracy of the experimental results.

Cobalt on boron‐doped carbon nitride for a novel bifunctional electrocatalyst in zinc‐air batteries

AbstractCarbon‐based materials have been widely applied in electrochemical field because of good conductivity and low cost. However, the electrochemical performances have been hindered by few active sites in themselves, heteroatom doping is a general method to solve the problem. Herein, boron (B) is doped into the carbon nitride (CN) derived from glucose and melamine by a facile way, and cobalt (Co) is introduced in the B‐doped carbon nitride (BNC) to form Co@BNC nanocomposites. Among the different contents of Co in Co@BNC series, 12%Co@BNC shows the best oxygen reduction reaction properties with half‐wave potential of 0.78 V, good stability and methanol tolerance in alkaline solution. Besides, 12%Co@BNC also shows oxygen evolution reaction voltage of 1.67 V, and good bifunctional electrocatalysis behaviors with ∆E of 0.89 V. This bifunctional electrocatalyst can be applied in zinc‐air batteries for transportation field.

The microstructure and mechanical properties of Co/YCF102 composite coating

PurposeLaser cladding has been used in the field of repairing damaged parts of machine tools due to its advantages of less processing restrictions and easy formation of a good metallurgical bond with the base material. However, the mechanical properties of the coating sometimes cannot meet the process requirements. Therefore, the purpose of this paper is to prepare coatings with high microhardness and flexural strength.Design/methodology/approachThe YCF102 alloy powder was mixed with different contents of Co and tested for laser cladding on AISI 1045 substrate under the same process parameters. The main phase composition of the coating was revealed by the XRD results. The main chemical composition of the coating was determined by the SEM and EDS results. In addition, the effect of Co content on the microstructure, microhardness and flexural strength of the coatings was investigated.FindingsThe results show that when the Co content is 2 wt% and 4 wt%, Co does not form compounds with other elements, but is uniformly distributed in the coating. And when the Co content is 6 wt% and 8 wt%, the Co reacts with Fe in the coating and generates Co3Fe7 in situ. The increase in Co did not result in a monotonic change in microhardness, but significantly improved the flexural strength and the flatness of the microstructure of the coating. When the Co content of the mixed powder is 8 wt%, the coating has high microhardness and flexural strength.Originality/valueCo/YCF102 composite coating with high microhardness and flexural strength was prepared. This paper provides a theoretical and practical basis for research in the area of repairing damaged parts of machine tools by laser cladding.

Effect of Co addition on microstructural and mechanical properties of WC–B4C–SiC composites

In this study, the effect of Co addition on microstructural and mechanical properties of WC-B4C–SiC composites sintered by spark plasma sintering (SPS) method was investigated. For this purpose, three batches of WC-B4C–SiC with different contents of Co (10 vol%, 15 vol%, and 20 Vol %) were sintered at 1400 °C. The results of X-ray diffraction (XRD) analysis of the samples indicated the formation of W2B5, W3CoB3 as well as the remained C phases and unreacted SiC phase. It was observed that by increasing the Co content, the amount of W2B5 phase reduces and W3CoB3 and C contents increase. Therefore, W2B5 peaks were not detected in the sample containing 20vol% Co. Relative density values above 97% were obtained for all the composites. However, a decrease was observed in relative density by increasing the Co content in the composites. The highest flexural strength (510 ± 42 MPa), fracture toughness (10.34 ± 0.82 MPa m1/2), and hardness (20.63 ± 0.75 GPa) were also obtained for the sample containing 10vol% Co compared to the other samples. In addition, Transgranular fracture of SiC as well as pulling out of W3CoB3 and W2B5 particles were observed in the fracture surface micrographs of the samples. The presence of micro-cracks in the SiC grains, fracture of W3CoB3 grains, and crack deflection was reported as dominant toughening mechanisms.

Effect of Co content on [Ca2CoO3−δ]0.62[CoO2] thermoelectric properties

The use of thermoelectric materials, which is a clean energy conversion method, can realize the direct conversion of thermal energy and electrical energy. Ceramic samples of the [Ca2CoO3−δ]0.62[CoO2] system with different contents of Co were prepared by sol–gel method combined with cold-press technology. X-ray diffraction and field emission scanning electron microscopy were used to confirm the single-phase composition and plate grain morphology of the samples. Analysis of the thermoelectric properties of [Ca2CoO3−δ]0.62[CoO2] (300–1026 K) shows that the electrical conductivity of the CCO–Co3 sample with low Co content is increased by 12% compared with that of the original sample CCO–Co1 at 1026 K. The thermal conductivity is decreased to 2.99 Wm−1 K−1. The ZT value of the samples with low Co content reaches 0.09 at 1026 K, which is 50% higher than that of the original sample CCO–Co1. Therefore, reducing Co content is an effective method to improve the thermoelectric properties of [Ca2CoO3−δ]0.62[CoO2] ceramics.

Effect of ultrafine gradient cemented carbides substrate on the performance of coating tools for titanium alloy high speed cutting

Gradient cemented carbides usually used as substrate for coating tools, and the substrate has different gradient layer thickness and grain size, which would affect the cutting performance of the coating tools. In this study, different contents of Co and cubic carbonitride were added, the ultrafine gradient cemented carbides with different gradient layer thickness and grain size were prepared by one-step sintering, and then the CAT films (films containing Cr, Al and Ti, basically.) were deposited on alloy surface by Arc Ion Plating (AIP) in Ar gas atmosphere for titanium alloy high-speed cutting. The influence of Co and cubic carbonitride content on the microstructure of alloy and the cutting performance of coated tools was studied. The results show that the gradient layer thickness could be controlled by changing the Co and cubic carbonitride contents, and then affected the cutting performance. The coating tools enhanced cutting performance obviously by reducing the flank wear in the high-speed Ti-alloy cutting. A thinner gradient layer can be formed in alloys that with a lower Co addition, thus leading to tools chipping during high-speed cutting Ti-alloy. The wear resistance and the cutting performance of the tools could be improved by adding cubic carbonitride. The Co10Ti3-CAT coated tool has the best cutting performance. And the wear resistance of Co8Ti4-CAT coated tool can be increased by 50% compared to substrate.

Electrochemical Comparative Characteristics of La(Fe,Si)13 Type Materials with Different Content of Co in Acidified Phosphate Environment in Presence of Cl- Ions

In the paper the electrochemical characteristics of alloys based on La(Fe,Si)13 phase have been presented. The material for research was the LaFe11.8-xCoxSi1.2 alloy with different cobalt content. Presented electrochemical characteristics provide information about pitting corrosion. This kind of corrosion is one of the most common local corrosion, it is especially undesirable for multi-phase alloys based on rare earth elements, as it contributes to the sudden and unexpected destruction of the surface of the material in working conditions. In the paper the results of potentiokinetic corrosion tests determined for LaFe10.72Co1.08Si1.2 and LaFe11.00Co0.8Si1.2 alloys in acidified phosphate solution (pH = 3) with different addition of chloride ions (Cl-) have been presented. Also analysis of alloys surface before and after corrosion measurement have been presented. The surface analysis have been carried out on the basis of profilometric roughness tests and optical microscopy observation. The studies have shown low resistance of LaFe10.72Co1.08Si1.2 and LaFe11.00Co0.8Si1.2 alloys to pitting corrosion, which, however, increases with Co content increase. DOI: http://dx.doi.org/10.5755/j01.ms.25.3.19536

Precipitation and phase transformation mechanism of additive manufactured Ni-Co base superalloy

Microstructures of a newly developed Ni-Co base superalloy with different contents of Co manufactured by additive manufacturing (AM) have been investigated using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results show that, the Ni-Co base superalloy made by AM presents a columnar microstructure. This columnar microstructure is achieved through epitaxial growth of fine parallel dendrites from a substrate. η phase and γ′ phase precipitate during the deposition process. After heat treatments, there are primary γ′, secondary γ′ and tertiary γ′ precipitated. The heat treatments also promote the precipitation of η phase. The inductively coupled plasma atomic emission spectroscopy (ICP-AES) investigation shows that the loss and segregation of elements can account for the formation of η phase. The results also indicate that the addition of Co promotes the precipitation of γ′ and impedes the precipitation of η phase. Electron probe microanalyser (EPMA) results show that increasing of Co content decreases the segregation of Ti in the heat-treated state and is beneficial for decreasing the precipitation of η phase. TEM analysis confirms that the phase transformation mechanism is mainly the reordering of atoms and the formation of stacking faults.

Corrosion behavior and product film formation of Ni[sbnd]Co[sbnd]Cu nanocrystalline coatings in neutral salt environments

The corrosion behavior of NiCoCu nanocrystalline coatings in neutral salt environments was systematically investigated by potentiodynamic polarization, linear polarization, electrochemical impedance spectroscopy, and long-term salt spray tests. The electrodeposited ternary coatings were Ni-based solid solution alloys that contained markedly different contents of Co and Cu. Greater Co and Cu contents strongly reduced the polarization and charge-transfer resistance of the coatings, thus decreasing their corrosion resistance in neutral NaCl solutions. In salt spray tests, the initial porous corrosion product film on the Co-/Cu-poor coating evolved into a compact film that finally grew to cover the coating surface, while such morphological transition was absent on the Co-/Cu-rich coating, where the formed film showed a continuous deterioration in its initial porous structure. Abundant Co-/Cu-substituted α-Ni(OH)2 might grow to form the primary compact films that could coalesce and thicken as corrosion was suppressed. A large amount of Cu(OH)2 together with high corrosion rates might be detrimental to the formation of compact films. A mechanism of the formation of the corrosion product films was proposed based on the corrosion characteristics of the ternary system and detailed corrosion product film analysis.

Interfacial reaction and microstructure between the Sn3Ag0.5Cu solder and Cu–Co dual-phase substrate

In this study, interfacial reactions and microstructures of the Sn3Ag0.5Cu (SAC305)/Cu–xCo (x = 0, 30 and 50 wt%) systems were investigated during reflowing at 290 °C and solid-state aging at 150 °C for various time. The effects of different contents of Co in substrate on interfacial reaction in SAC305/Cu–xCo system were discussed. It was found that the addition of Co into pure copper substrate to achieve alloying would effectively inhibit the growth of IMC layers. Comparison among the thickness of the intermetallic compound (IMC) in three kinds of SAC305/Cu–Co systems indicated that the IMC layer of SAC305/Cu joint was thicker than that of the other two types of solder joints. The composition of the SAC305/Cu IMC layers was Cu6Sn5 and Cu3Sn. Three kinds of reaction phases (Cu,Co)6Sn5, (Cu,Co)Sn2 and (Cu,Co)3Sn were found at the interfaces of the SAC305/Cu-30Co and SAC305/Cu-50Co joints. Remarkably the (Cu,Co)Sn2 phase was found adjacent to the Co-rich phase after soldering and eliminated after the aging treatment. While the (Cu,Co)3Sn phase accumulated increasingly adjacent to the substrate with the increased aging time. The results suggested that the Co content increased from 30 to 50 wt% in substrate lead to significant restraint of the growth of interfacial IMC. In addition, the thickness of the interfacial IMC layer was linear with the square root of the aging time during the aging process. The reaction rate between Sn atoms in solder and Cu, Co atoms in substrate was quite different, which lead to the fact that the interface of SAC305/Cu–Co is uneven on the side of substrate after reflowing and aging.

Tunable frequency response of tunnel-type magneto-dielectric effect in Co−MgF2 granular films with different content of Co

We have demonstrated the frequency dependence of the tunnel-type magneto-dielectric (TMD) effect in superparamagnetic Cox−(MgF2)1–x granular nanostructures by precise variations of x from 0.06 to 0.2. The structures consist of the nanometer-sized Co granules embedded in a crystallized MgF2 dielectric matrix. We observed an increased peak dielectric change Δε′/ε′0 from 0.8% to 3% at a specific frequency fTMD, and tunable fTMD was achieved from 8 kHz to 6.6 MHz by increasing x. Theoretical fittings predict that the narrow distribution of relaxation time gave rise to an enhanced Δε′/ε′0 and the narrowing of fTMD; the position variation of fTMD was attributed to the change in the intergranular distance between a pair of two neighboring granules. This study may help understand the fundamental physics between the TMD effect and nanometric structure and indicate that the films may work at higher frequency for devices with tunable dielectrics.

Study of Co-Mn/TiO<sub>2</sub> SCR Catalyst at Low Temperature

The Co-Mn/TiO2 catalysts with different contents of Co were prepared by the impregnation method. Catalytic activity tests showed that the addition of Co could obviously enhance the SCR performance of Mn/TiO2 catalyst, and the NO conversion of 0.05Co-Mn/TiO2 samples could reach 94.03% at 180 °C. At the same time, with the help of XRD, BET, H2-TPR and NH3-TPD, the various physical and chemical characteristics as well as phase structures of catalysts were characterized systematically. According to the results, the formations of crystalline CoMn2O4, Mn3O4 and amorphous Mn2O3 were detected. Furthermore, Co doping could reduce the reduction temperatures of catalysts and enhance the adsorption capacities of NH3, resulting in the excellent SCR performance at low temperature.

Effect of Cobalt content on mechanical properties of Al-Si alloy

This work encompasses studying the effect of different contents of Co on Al-Si alloy with Sb modification prepared by stir casting method. The content of Co is varying from 0 to 1.2wt%, The effect of Cobalt on microstructure, micro hardness, tensile strength and wear rate were studied extensively. The results show that the intermetallic compounds was increased with the increasing of Cobalt content .The Co-bearing compounds presented as small block shape at first and gradually turned into dendrite or fish bone shape. The addition of Co has appositive effect on tensile strength of the Al-Si alloys that used in the current research, the maximum tensile strength was (177MPa) when Co content was 0.9%Co at room temperature as well as wear rate were studied in this paper and noticed that the addition at 0.9%Co had the better effect at low and high load(5N),(10N).

Preparation of Co/Ce0.5Zr0.5O2 catalysts and their catalytic performance in methane partial oxidation to produce synthesis gas

Porous Ce0.5Zr0.5O2 solid solution support was prepared by co-precipitation and then different contents of Co (10%, 20%, and 30 %) were loaded over the Ce0.5Zr0.5O2 support by impregnation; the Co/Ce0.5Zr0.5O2 catalysts obtained in this way were used in partial oxidation of methane (POM) to produce synthesis gas. The fresh catalysts were characterized by N2 physical sorption (BET), X-ray diffraction (XRD), temperature-programmed reduction by hydrogen (H2-TPR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The amount of deposited carbon over the spent catalysts after POM tests was determined by temperature-programmed oxidation (O2-TPO) and thermogravimetric (TG) analysis. The results showed that cobalt oxide over Ce0.5Zr0.5O2 is easy to be reduced to metal cobalt. The Co/Ce0.5Zr0.5O2 catalysts show high activity and selectivity to H2 and CO in methane partial oxidation; higher Co loading is beneficial to enhance their catalytic activity and resistance to catalyst deactivation from coke deposition.

Effects of cobalt content on microstructure and mechanical properties of hypereutectic Al–Si alloys

Abstract Cobalt is generally considered as the element that can promote the high-temperature mechanical properties of Al–Si alloys. In order to develop new hypereutectic Al–Si alloys that can be used at high temperature, the changes of microstructure of Al–20Si–2Cu–1Ni–0.6Mg–xCo alloy with different contents of Co were studied in this paper. The results show that the volume fraction of intermetallic compounds was increased with the increasing of Co content. The Co-bearing compounds presented as small block shape at first and gradually turned into dendritic or fish-bone shape. After Co addition, the Fe-bearing compounds such as Al9(Fe, Co, Ni)2 could be dissolved and spheroidized to a certain degree through heat treatment. The addition of Co has a positive effect on tensile strength of the Al–20Si–2Cu–1Ni–0.6Mg alloys that added equal or less than 0.7% Co. The maximum tensile strength at room temperature and elevated temperature (300 °C) was 290 MPa and 182 MPa respectively with a Co content of 0.7%. Furthermore, the content of Co varying from 0 to 1.5% had little influence on the refining effect of primary Si and modification effect of eutectic Si, under P modification of the alloy melt.

High temperature PEM fuel cell performance characterisation with CO and CO 2 using electrochemical impedance spectroscopy

In this work, extensive electrochemical impedance measurements have been conducted on a 45 cm 2 BASF Celtec P2100 high temperature PEM MEA. The fuel cell performance has been examined subject to some of the poisoning effects experienced when running on a reformate gas. The impedance is measured at different temperatures, currents, and different content of CO, CO 2 and H 2 in the anode gas. The impedance spectrum at each operating point is fitted to an equivalent circuit and an analysis to identify the different mechanisms governing the impedance is performed. The trends observed, when varying the operating conditions under pure H 2, generally show good agreement with results from the literature. When adding CO and CO 2 to the anode gas the entire frequency spectrum is affected, and especially the measurements conducted at low temperatures and high CO concentrations reveal undesirable transient effects.

Variation of microstructure of RE-containing AlSi 20Cu 2Ni 1RE 0.6 alloy with different cobalt contents

Cobalt is generally considered as the element that can promote the high-temperature mechanical properties of Al–Si alloys. In order to develop new hypereutectic Al–Si alloys that can be used at high temperature, the changes of microstructure of Al–20Si–2Cu–1Ni–0.6RE– xCo alloy with different contents of Co were studied in this paper. The results show that, under P–RE complex modification of the alloy melt, the content of Co varying from 0 to 1.5% had little influence on the refining effect of primary Si and modification effect of eutectic Si, but the amount of acicular RE-bearing Al–RE–Ni–Co–Si compounds gradually increased with the increase of Co content. In addition, Co could also modify the morphology of Fe-bearing phases, which solidified as particles instead of long needles. The addition of Co even has an adverse effect on the tensile strength of this RE-containing hypereutectic Al–Si alloy.

Induced magnetic anisotropy and the structure of nanocrystalline Fe-Co-Cu-Nb-Si-B alloys with different content of Co: II structure of alloys with an induced magnetic anisotropy

A connection has been established between the structural state (phase composition) of the nanocrystalline alloys Fe73.5 − x Co x Cu1Nb3Si13.5B9 (x = 0, 10, 20, 30) and the type of the induced magnetic anisotropy (IMA), which is formed in the process of thermomechanical treatment (TMechT), on the one hand, and its thermal stability, on the other hand. It is shown that the addition of cobalt entails a decrease in the quantity of Fe-Si grains and the formation of phases that contain Fe-Co-B. The induced magnetic anisotropy depends on the volume fractions of structural components, their elastic properties, and coherent bonding of their crystal lattices.