查看更多>>摘要：? 2022 Elsevier B.V.Grain boundary diffusion of heavy rare earth-based alloys can effectively enhance the coercivity of Nd-Fe-B magnets. Although the light rare earth elements can further improve the diffusion efficiency of Dy and Tb, they generally lead to reduced anti-corrosion properties of the magnets. Here, we successfully enhanced the coercivity and corrosion resistance of Nd-Fe-B magnets by GBD of Ni alloyed Pr-Tb-Cu diffusion source. The ternary Pr35Tb35Cu30 alloy diffusion increased the coercivity of Nd-Fe-B magnet from 1330 to 1923 kA/m, but the coercivity was enhanced to 1990 kA/m by Pr35Tb35Ni15Cu15 alloy diffusion. The formation of high-anisotropy (Nd,Tb)2Fe14B phase is the main reason for the coercivity improvement. Partially substitution of Cu by Ni can reduce the melting point of Pr35Tb35Cu30 alloy, which is effective in promoting the infiltration of Tb. Cu is also a necessary element for improving the diffusion process, and the diffusion of Pr35Tb35Ni30 alloy only increased the coercivity to 1747 kA/m. More interestingly, the diffusion of Pr35Tb35Ni15Cu15 also enhanced the chemical stability of the magnet in NaCl solution. Scanning Kelvin probe force microscopy characterized that the modified GB phase in Pr35Tb35Ni15Cu15 treated magnet exhibits a higher Volta potential than the 2:14:1 main phase, which is the main reason for the improved corrosion resistance. The present results suggest that the non-rare earth elements in the alloy diffusion sources play important roles in enhancing both coercivity and corrosion resistance of Nd-Fe-B magnets.
查看更多>>摘要：? 2022 Elsevier B.V.Poor sinterability of powder metallurgy TiAl-based alloy is an important factor that restricts its industrial production. In this paper, we improve the sinterability of Ti-48Al alloy by adding Co element. In such case, the relative density of Ti–48Al based alloy sintered at 1250 ℃ increases from 82.6% to 96% with an increase of Co content from 0 to 1.5 at%. The densification improvement is caused by liquid TiAl2Co phase, which is formed at 1230 ℃. Then, uniform and fine near-γ microstructure is obtained, and the grain size increases with the increasing of Co content. More than 70% of grains in the Ti-48Al-0.5Co alloy are smaller than 2 μm. Overall, Ti-48Al-0.5Co alloy has better comprehensive performance, with compressive strength of 2533 MPa, yield strength of 683 MPa and fracture strain of 29.5%.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, different volume ratios (NiTiO3: CoFe2O4 = 1:3, 2:3, 1:1) of NiTiO3/CoFe2O4 composites were synthesized using the sol-gel method. The effects of different NiTiO3 volume ratios on the structural, morphological, magnetic, and microwave properties were systematically investigated by X-ray diffraction spectroscopy (XRD), field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy (RAMAN), vibrating-sample magnetometery (VSM), and vector network analysis. Electromagnetic wave absorption analysis indicated that 1:3 composite sample showed the greatest reflection loss (?21.7 dB at 17.1 GHz frequency) at a thickness of 10.0 mm. The microwave absorbing properties decrease with the increasing NiTiO3 volume ratio. The observed improvement can be attributed to the low degree crystallization of NiTiO3 that increases magnetic losses through increased exchange resonance.
查看更多>>摘要：? 2022 Elsevier B.V.We report the influence of Ni substituting for Fe on the phase stability and thermoelectric properties of YbxFe4-yNiySb12 (x = 0.6, 0.7, 0.8, 0.9, 1.0; y = 1.0, 0.8, 0.6). Ni substituting can efficiently enhance phase stability but reduces band gap, which establishes an optimum Ni substituting content to keep the balance. Meanwhile, the atomic disorder caused by Ni substituting together with Yb-filling leads to a significant reduction in lattice thermal conductivity. The most marked reduction in lattice thermal conductivity is achieved in the Yb0.9Fe3.4Ni0.6Sb12 compound with a minimum value of 0.71 W m?1 K?1 at about 650 K. Finally, a peak zT of 0.85 is attained at 673 K in the Yb0.9Fe3.4Ni0.6Sb12 compound, which is comparable to other p-type skutterudites at the same temperature. This work highlights the importance of considering the competition between phase stability and band gap when designing high thermoelectric performance cobalt-free skutterudites.
查看更多>>摘要：? 2022 Elsevier B.V.As the high energy-density energy storage and greenhouse gas capture device, Na-CO2 battery development is impeded by the sluggish CO2 reduction and difficult decomposition of insulating discharge products on the cathode. Here, the cobalt (Co)-decorated carbon nanofibers accompanying with slight Co oxidation were used as the self-standing cathode for Na-CO2 battery. It greatly reduces the discharge overpotential by 500 mV and charge overpotential by 210 mV, delivers a 12 times higher discharge capacity and runs nearly 4 times cycle life than its counterpart. Experiment combined with theory calculation demonstrates that the evenly dispersive, abundant and stable active sites (Co-CoO) with an equal CO2 adsorption-desorption capability is the key to improving cell performance. This work reveals the importance of catalysts/cathodes and provides a direction to design highly efficient catalysts/cathodes for alkali metal-CO2 batteries.
查看更多>>摘要：? 2022 Elsevier B.V.In the present work, the method of hot gas bulging with clustering balls (HGBB) was used to investigate the microstructure evolution, texture, and strengthening mechanism of Al–Mg alloys. After an alloy sheet was heated to 450 °C for 15 min, the square-pyramid shaped part was bulged by air at a pressure of 2 MPa. The ultimate tensile strength and hardness of the formed parts increased with the deformation, and the improvements in the most deformed area were by 30% and 40%, respectively, compared with the undeformed area. Microstructural and textural characteristics revealed that dynamic recovery occurred when the effective strain was 0.36, and new grains were created through dynamic recrystallization after the strain was further increased. The grains in the Cube {100} <001> and Brass {110} <112> orientations gradually increased with the deformation. Fine-grain strengthening, second-phase strengthening, and geometrically necessary dislocation density strengthening were the main strengthening mechanisms in the deformed area, which could be enhanced by the deformation during HGBB. A high dislocation density and low-angle grain boundaries were generated, accelerating and enhancing the precipitation and formation of fine recrystallized grains. The HGBB process yielded improved formability and mechanical properties of the formed parts.
查看更多>>摘要：? 2022 Elsevier B.V.A CuSe intermediate layer (IL) is prepared between CZTSSe and Mo electrode to decay the carrier recombination on the rear surface of the CZTSSe absorber. The power conversion efficiency (PCE) can be increased from 7.52% to 10.09% by optimizing the thickness of CuSe IL. The increased PCE comes from improvement in filling factor (FF), short-circuit current density (JSC), and open-circuit voltage (VOC), and their contribution percent is calculated to be 63.08%, 24.83%, and 12.09%, respectively. It is demonstrated that boosted FF is mainly due to decreased reverse saturation current density (J0), raised JSC owing to higher photogenerated current density (JL), and enhanced VOC caused by decreased J0 and higher JL. The contribution percent of (ideal factor (A), J0), JL, Rs, and shunt resistance (Rsh) to increased PCE is calculated to be 60.84%, 27.41%, 10.33%, and 1.42%, respectively. By experimental characterization and SCAPS-1D simulation, it is suggested that decreased J0 results from the formation of passivation field and high electron potential barrier at the rear surface of CZTSSe due to the addition of suitable thickness CuSe IL, higher JL from the increase in width of the depletion region of CZTSSe/CdS, lower Rs from decrease in thickness of Mo(S, Se)2, and bigger Rsh from improved crystal quality of CZTSSe absorber.
查看更多>>摘要：? 2022 Elsevier B.V.Dielectric thin films having high permittivity (high-k) and low dielectric loss is essential for developing high performance capacitive devices like metal oxide field effect transistor or thin film transistor. Ga ion implantation performed on Cu-doped ZnO film fabricated by pulsed laser deposition with optimized doping concentrations and post-implantation annealing yielded film having high permittivity and low dielectric loss (ε = 87 and tan δ = 0.17 at the frequency of 1 kHz). Moreover, the permittivity exhibits good stability over a wide range of frequency from 20 Hz to 10 MHz. The high-k film was characterized by detailed dielectric studies, including frequency dependence of permittivity and dielectric loss, complex electrical modulus analysis, impedance spectroscopy and ac conductivity. The enhancement of the permittivity was attributed to the correlated potential barrier hopping of electrons between the neighboring acceptor-donor defect complex states in the band gap created by the co-doping, thus acting as electric dipoles polarizing the film. This work opens up future possibility for ‘dielectric engineering’. The three-dimensional dielectric spatial profile can be controlled via the selective area ion implantation with the depth controlled by the ion implantation energy.
查看更多>>摘要：? 2022 Elsevier B.V.Hydrophobic silane/reduced graphene oxide (rGO) nanocomposites were successfully constructed on an AA2024-T3 aluminum alloy surface using a facile co-electrodeposition process. The composition and morphology were characterized by ATR-FTIR, XRD, Raman spectroscopy, EDX, XPS and SEM. The results revealed that the implanted GO nanosheets were partially reduced and successfully covalently bonded with silanol groups to fabricate a more compact and denser coating. Electrochemical measurements demonstrated that the electrodeposited silane/rGO nanocomposite markedly decreased the corrosion rate of the AA2024-T3 alloy in 3.5 wt% NaCl solution. The protection efficiency was maintained over 96% after 120 h of exposure, presenting excellent chemical stability. Meanwhile, a sand paper abrasion test was performed to evaluate the mechanical robustness and the contact angle was reduced by only 4.5° after 150 abrasion cycles. The excellent anti-corrosion property and mechanical robustness, along with the feasible electrodeposition procedure, show its great potential for industrial applications.
查看更多>>摘要：? 2022 Elsevier B.V.A commercially available INVAR alloy was subjected to the electrochemical conditionings including Fe-leaching and chronopotentiometric aging, to modulate surface composition and stabilize electrocatalysts for efficient and facile oxygen evolution reaction (OER). Owing to the complexing function of KSCN during Fe-leaching for the optimum Ni/Fe ratio and the stabilization of Fe-doped (oxy)hydroxides under the adequately higher current density within alkaline media, the OER electrode composed solely of 4J36 INVAR alloy as substrate needs an overpotential of only 250 mV to attain 10 mA cm?2 in 1 M KOH, besides its performance stability at two different current densities. This simple and cost-effective fabrication of OER electrode, which is binder-free, self-supporting and matrix-rejuvenating, will open a new door to the cutting-edge design of electrocatalyst for water splitting.
NSTL
Elsevier