查看更多>>摘要：? 2022In this study, the metastability of In0.68Ga0.32As layers on InP substrates was investigated at various growth temperatures. The thickness of each metastable In0.68Ga0.32As layer was 40 nm, which is four times the critical thickness of the stable lattice with a stress of approximately 1%. The surface morphologies and roughness of the metastable In0.68Ga0.32As layers were highly sensitive to the growth conditions. Cross-hatches were observed on their surfaces when they were grown at various growth temperatures, and over this range, the surface roughness varied from 0.11 nm to 0.16 nm. The lowest surface roughness of 0.11 nm was achieved at 770 °C, and the metastable In0.68Ga0.32As layer showed a flat surface morphology with terraces parallel to the step edges. These results corresponded to those of the strain relaxation analysis of the metastable In0.68Ga0.32As layers using X-ray diffraction spectra. The In0.68Ga0.32As layer grown at 770 °C was almost fully strained, whereas those grown at other growth temperatures were relieved by approximately 10%. The flat surface morphologies and almost fully strained lattices suggested that the growth conditions were suitable for preparing high-quality superlattices with well-defined interfaces. The intuitive results of the metastable In0.68Ga0.32As single layers were utilized to grow high-quality In0.67Ga0.33As/Al0.64In0.36As superlattices with a reduction in the misfit dislocation by 41.8%. The results obtained herein suggest that the growth conditions for superlattices can be easily and efficiently optimized using the metastability of the materials.
查看更多>>摘要：? 2022 Elsevier B.V.Cobalt based electrocatalysts for oxygen evolution reaction (OER) have better OER activities than other transition metals and have attracted great interest in the development of efficient and economic catalysts. However, rational design and manufacture of OER catalysts for further enhancing the electrochemical activity and durability are still challenging, which significantly limits their practical utilization. Herein, novel three-dimensional reduced graphene oxide/Co9S8 composites (Co9S8/rGO) are constructed by a facile strategy of ultrasonic spray drying assisted with sequential heat treatment process. Such crumpled structure possesses extraordinary synergistic effects between the two components of Co9S8 and rGO. The optimal sample exhibits ultra-low overpotential of 0.308 V, Tafel slope of 130.0 mV dec?1 at the current density of 10 mA cm?2, as well as excellent cycling stability in 1 M KOH. The superior catalytic activity of the crumpled Co9S8/rGO composite is attributed to its unique structure including large surface area and abundant sites for potential catalysis. This work provides a potential large-scale strategy to prepare cobalt sulfides based OER electrocatalysts and realize the development of the energy research for the generation of hydrogen from water.
查看更多>>摘要：? 2022 Elsevier B.V.Hollow microspheres with hybrid shell hold great potential to be employed as microwave absorbents aiming at high efficient dissipation and lightweight design, but their rational design and high efficient construction remain a big challenge. In the present work, novel Carbon/Carbon-Ag-Fe3O4 dual shell hollow microspheres (DSHM) were designed and prepared through a facile two step calcination induced pyrolysis route with distinct temperature. It is found that DSHM with various shell composition and microstructure can be obtained simply via tuning the calcination condition and the composition of the starting materials, which further determines the electromagnetic and microwave absorbing properties. The microwave absorption measurements demonstrate that with properly controlled shell composition, the optimized product presents an effective absorption bandwidth (EAB) of 7.8 GHz at a relatively low thickness of 2.0 mm. The DSHM reported here possess great potential to be employed as high efficient microwave absorbent towards multicomponent and wideband absorbing design.
查看更多>>摘要：? 2022 Elsevier B.V.The modified Li3+xMg2-xZnxNb1-xTixO6 ceramics were fabricated through a conventional solid-state reaction method. The charge compensation of Zn2+ ions substitution into Mg2+ site and Ti4+ ions substitution into Nb5+ site of Li3Mg2NbO6 ceramics were performed by introducing lithium ions. XRD patterns analysis and Rietveld refinements verified that Li3+xMg2-xZnxNb1-xTixO6 ceramics displayed an orthorhombic structure accompany with a little of impure phase. B/C site modification improved dielectric properties. An optimal dielectric properties of εr = 16.3, Q×f = 93,100 GHz, and τf = ?34.1 ppm/°C were acquired for Li3.04Mg1.96Zn0.04Nb0.96Ti0.04O6 ceramics, which heralds their microwave application potential.
查看更多>>摘要：? 2022 Elsevier B.V.Transition metal oxides are potential electrodes for lithium/sodium-ion batteries, but they are generally characterized by low electronic conductivity and a large volume change during charge/discharge. Metal oxide/bio-carbon composites have shown tremendous promise, but traditional methods for the preparation of bio-carbon-based composites are incapable of achieving high porosity and even distribution. Herein, we used a combined strategy aided by salts and ball milling to facilely prepare vanadium oxide/biomass (i.e., black fungus)-derived carbon (BFC) composites for mass production. The optimized composite (e.g., V2O3/BFC), assembled in lithium-ion batteries, offers high reversible capacity of 461.9 and 377.2 mAh g?1 after 120 cycles at 0.5 and 1.0 A g?1, and demonstrates good capacity retention after experiencing rate-capability and long-term measurements. Notably, the V2O3/BFC composite further shows good cycle stability for sodium-ion batteries, with 253.3 mAh g?1 at 0.2 A g?1 after 160 cycles. The excellent electrochemical performance of V2O3/BFC can be attributed to the simultaneous introduction of salts and ball milling in effectively cracking bulk carbon and dispersing V2O3, leading to the formation of a hierarchically porous structure with a high specific surface area and a homogeneous distribution of V2O3. Furthermore, the hierarchically porous structure favors ion/mass transport and alleviates the adverse impacts of volume expansion, while electrons are facilely transferred via the carbon framework. The work highlights a combination method that includes salts and ball milling, and the feasibility of employing natural-abundant biomass and commercial vanadium oxide for high-performance lithium/sodium-ion batteries.
查看更多>>摘要：? 2022 Elsevier B.V.Biomedical Ti-xNb-7Zr-0.7O (wt%) alloys were manufactured from elemental powders and controlled addition of TiO2 using field assisted sintering technique (FAST). First, sintering parameters were optimized on the benchmark Ti-29Nb-7Zr-0.7O alloy. Second, alloys with various content of Nb (20, 23, 26 and 29 wt%) were manufactured. FAST is capable to produce homogeneous material with controlled amount of oxygen. In addition, FAST is a valuable method for fast sampling of alloys with different compositions. Detailed XRD and SEM study proved that oxygen prevents formation of α” martensite phase. Presence of α phase, α” phase and especially ω phase causes an increase of elastic modulus and microhardness. Single phase β Ti-29Nb-7Zr-0.7O alloy can be manufactured by FAST from elemental powders and subsequent solution treatment. The alloy is proposed for biomedical use due to its low elastic modulus.
查看更多>>摘要：? 2022 Elsevier B.V.Changes triggered by low temperature metastable relaxation annealing in the peculiar magnetic behavior of rapidly solidified submicronic amorphous wires are reported. The overall aim was to understand the effects of the associated stress relief process on magnetization switching and magnetic domain wall propagation in these low dimensional amorphous wires with cylindrical symmetry. The results have shown that, even though the employed relatively low annealing temperatures did not initiate any crystallization, i.e., the amorphous state has been preserved, the consequences in terms of magnetic behavior are significant, with important variations in both magnetic switching field and domain wall velocity values. The observed modifications have been interpreted based on the interplay between the magnetoelastic and magnetostatic anisotropies within the submicronic amorphous wires, as well as on the complex changes in the underlying nonlinear stress distribution generated by the rapid solidification process. The outcomes of this investigation, alongside the general framework for their explanation, have unraveled novel ways of accurately tailoring and controlling the magnetic characteristics of the amorphous submicronic wires for developing new applications in sensors and domain wall logic devices, in which rapid switching and fast domain walls can make an important impact.
查看更多>>摘要：? 2022 Elsevier B.V.A series of Bi3+ or Eu3+ ion single doped and Bi3+ and Eu3+ co-doped CaZnOS phosphors were synthesized via high temperature solid state method. Under ultraviolet (UV) excitation, CaZnOS: Bi3+ has an intense emission band ranged from 400 to 600 nm owing to the 3P1,0 → 1S0 transition of Bi3+. And CaZnOS: Eu3+ shows superior red emissions due to the characteristic 5D0 → 7FJ (J = 1, 2, 3, 4) transitions of Eu3+. Tunable emission chromaticity from cyan, white, yellow to red is obtained by regulating the proportion of Eu3+ in CaZnOS Bi3+, Eu3+. The energy transfer mechanism from Bi3+ to Eu3+ was confirmed to be a quadrupole-quadrupole interaction based on the overlap of emission band of Bi3+ and excitation band of Eu3+ combined with the luminescent lifetime measurement. In addition, CaZnOS: 2.5 mol% Bi3+, 3 mol% Eu3+ phosphor with optimized concentrations has standard white light chromaticity coordinates (0.315, 0.323) and activation energy about 0.372 eV, which reflects its potential application in ultraviolet-chip excited white light emitting diodes (W-LEDs).
查看更多>>摘要：? 2022 Elsevier B.V.Design and synthesis of cheap and high-efficient bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are very important for the large-scale H2 production by water splitting. In this work, a series of core-shell nanostructure NiO-x@Co0.5Fe0.5P/CC have been fabricated by an easy synthetic strategy and served as bifunctional electrocatalytic electrode for overall water splitting. Owing to the heterostructure and interaction between the outer NiO nanoparticles shell and inner Co0.5Fe0.5P nanowires core, the optimal NiO-3@Co0.5Fe0.5P/CC catalytic electrode exhibits admirable catalytic performance both for HER and OER (73 mV and 262 mV at 10 mA cm?2, respectively) in 1 M KOH solution. As a result, the water electrolysis device based on NiO-3@Co0.5Fe0.5P/CC || NiO-3@Co0.5Fe0.5P/CC system only needs 1.585 V to offer the current density of 10 mA cm?2 and keeps excellent durability for 40 h, suggesting its great practical application value for overall water splitting.
查看更多>>摘要：? 2022 Elsevier B.V.Nanostructured alloys possess exceptional desirable properties but suffer from low thermal stability, as a consequence of a high content of grain boundaries where the atoms are in non-equilibrium lattice positions. Here nanocrystalline Ti/AZ61 magnesium matrix composite (AZ61Mg-Ti) was annealed isothermally between 573 K and 723 K. Subsequently, the thermal stability was analyzed, taking nanocrystalline AZ61 alloy as the comparative object. After annealing at 723 K for 600 min, the average grain size of AZ61Mg-Ti was approximately 95 nm, much less than that for the annealed AZ61 alloy (~450 nm). And Ti particles with size of ~410 nm and nano scale Ti3Al particles with size of ~ 8 nm were uniformly distributed in magnesium matrix. The kinetics of magnesium grain growth for nanocrystalline AZ61Mg-Ti, was well interpreted by generalized parabolic grain growth model, D8?D08=kt. The activation energy (Eg) for grain growth was calculated to be 134 kJ/mol, being 42 kJ/mol higher than that for pure Mg. For Eg, the contribution rates of drag effect and pinning effect to improve thermal stability were calculated to be 62% and 38%, respectively. Hardness evolution of annealed samples was studied and with raising annealing temperature the downtrend for AZ61Mg-Ti was more gradual than for AZ61 alloy due to the effect of the non-thermal sensitive Ti particles and the restricted Mg grain growth. After annealing treatment at 723 K for 600 min, the hardness was 1.27 GPa, higher than that for the annealed AZ61 (1.13 GPa).
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