•Nanocrystallines of MgAl2O4 were synthesis by the simple, short time and inexpensive sol–gel method.•The structure properties of MgAl2O4 nanoparticles obtained was excellent including.•The average ...crystallite’s sizes spinel and specific surface area were estimated about 11.07nm and 154m2g−1.•The nanoparticles sizes were about 12nm and have mesoporous structure.•MgAl2O4 nanopowders with these structure properties are suitable as catalyst supports.
Nanocrystallines of magnesium aluminate spinel (MgAl2O4) were synthesis by modified sol–gel method using aluminum nitrate, magnesium nitrate, citric acid and diethylene glycol monoethyl ether were used as precursor materials with a molar ratio Al/Mg=2. After obtained a dry powder, the precursor was heat-treated in air at desired temperatures (700–900°C) for 2h. The formation nanocrystallines of MgAl2O4 spinel were characterization by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Thermal gravimetric and differential thermal analysis (TGA/DTA), Field emission scanning electron microcopy (FESEM) with the energy dispersive X-ray spectroscopy (EDX), High resolution transmission electron microscopy (HRTEM) and specific surface area of the synthesized powders was measured with a Brunauer–Emmett–Teller (BET) apparatus using N2 adsorption. According to obtained XRD patterns the formation of single phase MgAl2O4 completed up 700°C. The average crystallite’s sizes increased with increasing temperature of calcination, but the specific surface area spinels decreased. The average crystallite’s sizes spinel and specific surface area at 800°C were estimated about 11.07nm and 154m2g−1, respectively. The results of FESEM analysis show that the nanoparticles shape are as spherical shape, uniform and a little agglomerated. The dimension of nanoparticles used by HRTEM was measured to be about 12nm by averaging 20 particles at 800°C.
In this study, copper manganese oxide films with various compositions were synthesized using electrochemical deposition technique. In order to achieve different chemical compositions, the influence ...of sodium citrate as a complex agent was investigated. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Brunauer-Emmet-Teller adsorption (BET) were used to study the morphology, chemical composition, crystal structure and surface area of deposited layers, respectively. We observed that by optimizing the citrate concentration in the electrodeposition electrolyte, improved capacitance of 744 F/g at 10 mV/s with retention capacitance of 91% over 10,000 cycles can be achieved. The obtained stability of copper-manganese oxide is 3 times and about 2 times higher than pristine copper oxide and manganese oxide, respectively. The enhanced stability of the achieved crystalline copper-manganese oxide ascribe to formation of CuMn2O4 spinel, improved ultrafine structure and a better chemical stability.
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•Synthesis of spinel structure beside of other metal oxides, by one step, without using the heat treatment process.•Investigation of the effect of complex agent concentration on the structure and compounds containing copper-manganese oxide.•CuMn2O4 exhibited better cyclic stability than composite of copper oxide and manganese oxide.•Investigation of capacitive properties of synthesized composites.
In this study, Cu–Ni foam with different percentages of nickel and copper was fabricated by the electrodeposition method. The morphology and phase structure of deposited foams were investigated by ...field-emission scanning electron microscope and X-ray diffraction, respectively. Moreover, TEM was utilized to see the foam morphology and the feather-like structures in more detail. It was observed that Cu–Ni foam had a feather-like structure, and the presence of this type of structure led to an increase in the electrode/electrolyte interface. Based on the results, it was found that by adding nickel to copper, the electrocatalytic performance was improved, and the hydrogen evolution reaction (HER) activity of Cu–Ni foam was also higher than Cu foam. The electrochemical surface area of fabricated structures was measured by the electrochemical test and it was revealed that the fabricated electrode possesses a high surface area (85.9 cm
2
). The HER activity of electrodeposited feather-like foams was studied by linear sweep voltammetry in 1.0 M KOH, which showed that the Tafel slope of the Cu–Ni foam (50 wt% Ni) was 97 mV dec
–1
and its required overpotential to attain the current density of 10 mA cm
–2
was 229 mV. Overall, this research proposes a highly efficient and affordable Cu–Ni foam with remarkable electrocatalytic properties in alkaline media.
Graphical Abstract
In this study, a novel Ni-P-coated WC/NiCrBSi composite cladding was prepared on a carbon steel substrate through high-temperature vacuum brazing technique with the aim of improving the wear ...properties of the surface. In order to improve the wettability of WC particles by a liquid phase (NiCrBSi alloy), Ni-P layer was deposited on carbide particles by electroless plating. This layer assisted to fabricate a thick coating with very low porosity, improving adhesion strength between ceramic particles and the matrix. The morphology, crystal structure and microstructure of coated carbides and the resultant composite cladding were characterized by field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. Thin electroless plated Ni-P shell with a thickness about 50–150 nm, were coated on WC particles. In the claddings, a uniform and homogenous distribution of WC particles in Ni-based matrix was observed. The pin on disk wear test was carried out to investigate the wear behavior of the fabricated cladding reinforced with and without Ni-P coated WC particles. The results indicated that the resistance against crack initiation and propagation significantly improved by using Ni-P layer in the sintered cladding. This cladding exhibited very low wear weight loss than conventional brazed cladding.
•A thick brazed coating was performed by core-shell powder (ultrafine WC@NiP) and Ni-based alloy as an infiltrant material.•Ni-P shell layer on WC particles improved the adhesion of particles to the Ni-based brazing alloy.•The remaining pore space value was decreased by using WC@NiP, resulting in increased the wear resistance.•The cracking susceptibility was decreased for Ni-based brazed cladding reinforced with Ni-P coated WC particles.
In vacuum infiltration of Ni-based self-fluxing alloy (NiCrBSi) cladding, reinforced with ultrafine WC particles with average particle size (APS) of 0.2–0.4 μm, several plate-like anomalous WC grains ...were observed with size of greater than 20 μm. To prevent this anomalous grain growth, Cu shells were coated on WC particles. The very low solid state solubility of WC in copper phase at high temperature can lead to no anomalous WC grain growth. Cu shell with a thickness about 30–50 nm was deposited by means of electroless plating on ultrafine WC particles. The microstructural features of Cu-coated carbides and the resultant brazed claddings were characterized by field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS). The evaluation of the brazed cladding revealed a thick ultrafine grained-microstructure with homogeneous grain size distribution, in contrast to the bare WC-based cermet cladding. The hardness of this novel composite cladding was nearly increased up to 1500 HV, which was 40% more than that of the un-coated WC reinforced cladding. The results demonstrated that the resistance against crack initiation and propagation considerably improved by using Cu-coated WC particles in the sintered media.
•To prevent anomalous WC grain growth in Ni based cladding, Cu shell was coated on WC particles by electroless deposition.•The very low solid state solubility of WC in copper phase at high temperature led to no anomalous WC grain growth.•A fine microstructure with homogeneous grain size distribution was obtained in Cu-coated WC reinforced Ni based cladding.•The hardness of this cladding was increased up to 1500 HV, 40% more than that of uncoated WC reinforced Ni base cladding.•The resistance against crack initiation and propagation was considerably improved in Cu-coated WC reinforced Ni based cladding.
► The effect of milling time on the morphology of TiC/steel was investigated. ► The nanocrystalline structure powder at 40h milling time was obtained. ► The maximum hardness of consolidated composite ...powders was 67 HRC.
This paper presents the results of milling time on the structure and properties of obtained stainless steel/30%TiC nanocomposite prepared by planetary milling in argon atmosphere using stainless steel 316 and titanium carbide powders. Achievement of a fine distribution of TiC nanoparticles in the steel matrix was the main purpose of this study. The results showed that increasing of the milling time up to 40h led to good distribution and grain refinement of nanocomposite powder. The microstructure evolution of milled powders and nanocomposite were investigated by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and optical microscopy. TEM image revealed clearly that TiC nanoparticles with grain size of 50nm were distributed in steel matrix at milling time of 40h. The maximum hardness and density were 67 HRC and 6.63g/cm3, respectively, when the sample was pressed under 550MPa pressure and sintered at 1400°C.
•Combination of copper oxide foam and GO layer by EPD provides a good design strategy for high-performance energy storage device.•The supercapacity of the composite film was studied with various GO ...morphology.•Specific capacity of CuO foam layer has been improved by amounts of 72%, 49% and 40% for EPD time deposition of 1, 3 and 7 min of GO, respectively.
In this study, a facile and reproducible method has been developed to synthesize a nano composite foam layer of CuO/ graphene oxide (GO) intended for supercapacitor applications. GO particles were deposited on elecroplated CuO foam layers through electrophoretic deposition (EPD). The results showed that by varying EPD time (1, 3, 7 min), the degree of coverage of the foam layer with GO changes. This makes it feasible to manipulate the specific capacity of (Csp) CuO foam layers (238.3 F.g−1). It was shown that the specific capacity of the foam layer has been improved by amounts of 72%, 49% and 40% for EPD time deposition of 1, 3 and 7 min of GO, respectively.The results suggest a new versatile design to enhance super capacity and energy storage properties in conventional transition metal oxides. Morphology, phase structure, porosity and surface area of synthesized structures were investigated by field emission secondary electron microscopy (FE-SEM), X-ray diffraction (XRD) and BET (Brunauer– Emmett–Teller) approaches. Super capacity properties of the layers were from cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) tests.
► In the current research, MWCNTs are pretreated by two different chemical treatments and then electrodeposited with nickel from a modified Watt's plating bath. The main results are as bellows ► In ...similar plating condition, shortened nanotubes were more co-deposited than elongated ones. ► Shortened nanotubes are behaved as inert ceramic particles, and embedded into the nickel matrix, whilst the long functionalized nanotubes showed metallic behavior and incorporated into the nickel matrix. ► SMWCNTs enhance more effectively the hardness of matrix due to their smaller length and higher co-deposition in comparison with LMWCNTs. ► Inclusion of nanotubes into the nickel matrix modifies grain orientation from (100) soft mode toward (111) direction. ► As LMWCNTs are more tightly incorporated into the nickel matrix than SMWCNTs, the dissention of them from the matrix posterior is more occurred results in lower corrosion current density in comparison with Ni-SMWCNTs coating.
Two different chemical treatments were performed on multi-walled carbon nanotubes (MWCNTs), namely functionalization, and shortening-functionalization processes. Then, nickel–MWCNTs coatings were co-electrodeposited. The results showed that the chemically shortened nanotubes were behaved as inert particles, and embedded into the nickel matrix, whilst the long functionalized nanotubes showed metallic behavior and during electrodeposition, they were incorporated into the nickel matrix. In similar plating condition, the amount of co-deposited shortened nanotubes was more than elongated ones. Furthermore, it was revealed that the pretreatment of nanotubes significantly affected the microstructure, surface morphology, hardness and corrosion resistance of deposited coatings.
To improve the corrosion protection of sol–gel derived hybrid silica/epoxy coatings containing boehmite nanoparticles, inorganic corrosion inhibitor was introduced into the coating via encapsulation ...in the nanoparticles. The morphology and chemical structure of the deposited films were studied by Scanning Electron Microscopy (SEM) and Fourier Transformed Infra-red Spectroscopy (FT-IR). The anticorrosion and self-healing properties of the coatings were evaluated by Electrochemical Impedance Spectroscopy (EIS). The high corrosion resistance performance of such coatings is due to the presence of encapsulated cerium nitrate corrosion inhibitor that can be released at the defects within the coating, hindering the corrosion reactions at defective sites.
In this study, different Cobalt–Copper mixed oxides compositions for supercapacitor electrodes have been prepared, by means of electrodeposition and thermal annealing. The chemical–physical and ...electrochemical characterization of electrodes, as well as the effect of different Co/Cu in the ratios on the crystal lattice, electrode morphologies, and electrochemical performance of the electrodes, were investigated using X-ray diffraction (XRD), scanning electron microscopic (SEM) and cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge (GCD) tests. The results indicated that the electrode prepared from 0.06 M CoSO
4
·7H
2
O + 0.04 M CuSO
4
·5H
2
O solution (CC4) had a better electrochemical performance. The initial capacity of the CC4 electrode was 28.3 mAh/g at a scan rate of 5 mV/s with a coulombic efficiency of 94%. CC4 electrode featured capacity retention of 79.2% at a constant current density of 1 A/g after 5000 cycles.
