In this study, two compounds of TiNb2O7 and Ti2Nb10O29 were successfully synthesized by mechanochemical method and post-annealing as an anode material for lithium-ion batteries. The effect of ...annealing atmosphere on the morphology, particle size, and electrochemical characteristics of two compounds was investigated. For these purposes, the reactive materials were milled under an argon atmosphere with a certain mole ratio. Subsequently, each sample was subjected to annealing treatment in two different atmospheres, namely argon and oxygen. Phase and morphology identifications were carried out by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) to identify the phases and evaluate the morphology of the synthesized samples. The charging and discharging tests were conducted using a battery-analyzing device to evaluate the electrochemical properties of the fabricated anodes. Annealing in different atmospheres resulted in variable discharge capacities so that the two compounds of TiNb2O7 and Ti2Nb10O29 annealed under the argon atmosphere showed a capacity of 60 and 66 mAh/g after 179 cycles, respectively, which had a lower capacity than their counterpart under the oxygen atmosphere. The final capacity of the annealed samples in the oxygen atmosphere is 72 and 74 mAh/g, respectively.
The present paper aims to investigate the influence of the current density in the electroplating process on the microstructure, crystal texture transformations, and corrosion behavior of Ni/Co–pumice ...multilayer nanocomposite coatings. The Ni/Co–pumice composite coatings were prepared by deposition of Ni, followed by the simultaneous deposition of pumice nanoparticles (NPs) in a Co matrix via an electroplating process at various current densities. Afterward, the morphology, size, topography, and crystal texture of the obtained samples were investigated. Furthermore, electrochemical methods were used to investigate the corrosion behavior of the produced coatings in a solution of 3.5wt% NaCl. The results indicated that increasing the plating current density changed the mechanism of coating growth from the cell state to the column state, increased the coating thickness, roughness, and texture coefficient (TC) of the Co (203) plane, and reduced the amount of pumice NPs incorporated into the Ni/Co–pumice composite. The electrochemical results also indicated that increasing the current density enhanced the corrosion resistance of the Ni/Co–pumice composite.
Mechanochemical behavior of WO3–B2O3–Mg ternary system to produce tungsten boride-based nanocomposites was investigated in terms of milling duration. To provide essential conditions for the ...occurrence of a mechanically induced self-sustaining reaction (MSR), a mixture of tungsten trioxide, boron oxide and elemental magnesium with the stoichiometric composition was activated using a high-energy planetary ball mill. Based on the obtained data, the adiabatic temperature was around 3659K which confirmed that the reaction mode was MSR. Due to the occurrence of a combustion reaction at the beginning of milling, the phase compositions were W, WB, W2B, and MgO. After 60min of milling, WB disappeared completely and a ternary nanocomposite with the phase constituents of W2B, W and MgO was obtained. With increasing the milling time to 1800min, no phase transformation was observed and thus a nanocomposite powder with similar phase compositions was produced. However, the percentage of the detected phases fluctuated in terms of milling time. During the leaching process, MgO (unwanted phase) was completely removed and consequently a nanocomposite powder with the phase compositions of W2B and W was formed. From the microscopic observations, the size of the composite particles was varied from 38 to 500nm.
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•Mechanochemical behavior of WO3–B2O3–Mg ternary system was studied.•Tad was around 3659K which showed that the reaction mode was MSR.•After the leaching process, W2B–W nanocomposite powder was obtained.•From SEM images, the size of the composite particles was varied from 38 to 500nm.•Based on the thermodynamic assessments, the reactions consisted of two stages.
Abstract
In this study, sintering of magnesia nanopowder was investigated using spark plasma sintering (SPS), and the effects of time and pressure on microstructure, physical properties, density, and ...infrared transparency were studied. Densification of magnesia nanopowder was examined at 1100 °C and the pressure of 40, 60, and 80 MPa, and at different times. Findings indicated that MgO ceramics’ density rapidly increased with increasing the sintering time up to 5 min, while it increased with a slow speed after 5 min. Analysis of grain growth rate at different times indicated that, in the initial stages of sintering, the process was done through a non-diffusional process and, in the final 15 min of the process, it was done through lattice diffusion. In addition, examining the yield stress of the sintered sample at 1100 °C and considering its conformity with the results of theoretical density showed that it underwent plastic deformation up to 15 min. In general, the results revealed that the main mechanism of magnesia sintering was plastic deformation. The highest infrared transmittance of 65% was obtained for the sample sintered at 1100 °C for 20 min at 80 MPa.
Dissimilar transient liquid phase (TLP) bonding of GTD-111 and IN-718 nickel-based superalloys was investigated using BNi-9 (AWS A5.8/A5.8M) as an interlayer. The effect of the bonding time on the ...microstructure and mechanical properties of the TLP-bonded specimens was studied at 1100 °C using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry (EDS), and micro-hardness and shear strength analyses. Joint microstructural studies revealed that at the bonding times shorter than 75 min, nickel- and chromium-rich borides were formed with the joint centerline. The volume fraction of intermetallic compounds decreased with the increase of the bonding time and the diffusion of boron element whereby the isothermal solidification eventually completed after 75 min. Micro-hardness investigations along the bonding joint showed that the hardness of an isothermal solidification zone (ISZ) decreased with the completion of isothermal solidification. The hardest zone in the joint structure belonged to the athermal solidification zone (ASZ). The shear strength test results showed that incrementing the bonding time increased the shear strength where the shear strength value at 1 min/1100 °C (320 MPa) raised to 590 MPa after the completion of isothermal solidification.
The effect of aluminum content on the mechanochemical behavior of ternary system Al–B2O3–C to fabricate Al2O3/B4C composite was investigated. A mixture of boron oxide powders along with different ...amounts of aluminum and graphite was activated in a ball mill. The value of Al content varied from 2mol to 7mol compared to the stoichiometric mole ratios (4mol). Thermodynamics evaluation indicates that the value of Al content in the mixture plays a key role and overall reaction enthalpy and adiabatic temperature altered by variation of aluminum and carbon content. Experimental findings revealed that at low aluminum content (2mol Al), aluminothermic reaction proceeded in gradual mode and no carbothermal reduction took place. Increase in Al content up to 3mol led to a change in the mode of aluminothermic reaction to MSR (mechanically induced self-propagating reaction) and gradual occurrence of carbothermic reaction. By increasing the amount of Al (10/3–4mol Al), aluminothermic reaction provided sufficient heat for activating endothermic carbothermic reduction; hence, both reducing reactions happened simultaneously. Further increase in Al content (7mol Al) led to gradual aluminothermic reaction and excess Al acted as inert matrix.
► Effect of Al content on the mechanochemical behavior of Al–B2O3–C was investigated. ► Al amount, within a range of 2–7mol plays key role. ► This suggests that increasing Al amount to 4mol is thermodynamically favorable. ► Aluminothermic reaction provided enough heat for activating carbothermic reduction.
The dissimilar austenitic stainless steel (AISI304L) and ferritic stainless steel (AISI430) have been welded with two types of filler metals (316L and 2594L) by GTAW. Then, the effect of heat ...treatment on the microstructure, mechanical properties, and corrosion properties of welded joint was investigated. Due to remove chromium carbide created during welding process and homogenize the microstructure, heat treatment was carried out on the whole series of the samples at 860°C and 960°C. The microstructural, fracture cross-section and corrosive areas of the samples were investigated by SEM. Tensile, bending and potentiodynamic polarization tests were employed to characterize mechanical and corrosion performance of the samples. The results indicate that the welded joints had good mechanical properties after heat treatment so that the best tensile strength was obtained at 960°C. Due to reduce grain size, the heat treatment samples show minimum corrosion resistance at 960°C in comparison to 860°C.
ZnO sorbents supported on alumina particles showed greater sulfur adsorption capacity than pure agglomerated ZnO sorbents.
ZnO–Al2O3 composite particles composed of ZnO nanosheets (thickness of ...40–80nm) on alumina particles were prepared by heterogeneous precipitation method using bayerite seed particles. The as-prepared composite particles were characterized in terms of crystal structure, morphology, surface area and pore volume. The composite particles were used as sorbent for H2S adsorption at low temperature, and were compared with pure ZnO sorbent. The composite sorbent showed a greater sulfur adsorption capacity (0.052g/g) than pure form of ZnO (0.028g/g). This significant improvement was mainly attributed to higher surface area, more pore volume and unique morphology in nanoscale, which were also obtained by low cost presented method in this work for synthesis of ZnO sorbent supported on alumina particles.
Titanium oxide (TiO2) nanoparticle coatings were deposited on the 316L stainless steel substrates by sol‐gel method. The morphology, structure, and corrosion resistance of the coating were analyzed ...using SEM, AFM, X‐ray diffraction, and electrochemical techniques. The deposition parameters employed to realize the anticorrosion performance including calcinations temperature, polyethylene glycol (PEG) content, pH value, and number of dipping cycles were investigated. Taguchi statistical experiments were carried out to determine the influence of the deposition variables on anticorrosion properties and optimal conditions. The results indicated that a higher anticorrosion performance of TiO2 films could be achieved using 1 g of PEG in a sol with pH in range of 7–9, six cycles of dipping, and calcination temperature at 400°C. The Tafel polarization measurements indicate that icorr value decreases about 200 times and the Rcorr value increases around 57 times compared with uncoated 316L stainless steel.
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