查看更多>>摘要：? 2022 Elsevier B.V.The variation of glass forming ability, mechanical properties and atomic structure in Zr72?xCo28Alx (x = 14–19 at%) and Zr56Co44?xAlx (x = 13–20 at%) bulk metallic glasses derived from composition tuning has been studied by using copper-mold suction, high-energy X-ray diffraction, extended X-ray absorption fine structure experiments and ab initio molecular dynamics simulations, respectively. Both experimental and theoretical results indicate that glass forming ability was enhanced when composition approached Zr56Co28Al16, attributed to the densification in the first shell around Co atoms with the increase of 11-coordinated polyhedra. In addition, a ductile-to-brittleness transition induced by minor substitution of larger-sized atoms by smaller-sized atoms has been found. As good glass forming ability is usually accompanied by dense atomic arrangement, the increasing larger-sized atoms may tend to offer more free volume which is beneficial to plastic flow. Compositional tuning, along with structural tuning to influence both glass forming ability and plastic flow, offers a reliable method to develop ductile metallic glasses.
查看更多>>摘要：? 2022 Elsevier B.V.Co-10 at% and -15 at% Cr with the stable hexagonal close packed (hcp) crystal structure at room temperature have been subjected to gaseous nitriding treatment using nitriding temperatures of 400 °C and 450 °C far below the austenite start temperature. Using X-ray and electron backscatter diffraction (EBSD), structural changes as a result of nitrogen incorporation into the initial hcp lattice can be divided into the following steps: (i) expansion of the lattice due to N uptake yielding hcp (hcpexp) at nitriding temperature of 400 °C, (ii) gradual transformation of hcpexp into an expanded face-centered cubic phase (fccexp) by increasing time at 400 °C/ or temperature to 450 °C (mixture of two phases), (iii) development of stable nitrided layer containing fccexp using moderate nitriding times up to 3 h at 450 °C and (iv) decomposition of fccexp layer into CrN nitrides and less expanded austenite and the reverse transformation from fcc to hcp at near-surface regions at 450 °C after prolonged nitriding time of 24 h. Due to occurrence of step (iv), the square-root treatment-time dependence of the nitrided layer thickness breaks down. Nitrogen-depth profiles obtained for Co-15 at% Cr by glow-discharge optical emission spectroscopy (GDOES) along with the Non-Rutherford MeV proton backscattering spectrometry reveal a nitrogen supersaturation of around 20 at% at surface-adjacent areas in hcpexp. A relatively large unit volume expansion has been recognized for hcpexp with a change of c/a ratio of around 0.6%. Hardness-depth profiles obtained for nitrided Co-10 at% and -15 at% Cr alloys using nanoindentation evidence an increase in hardness inside the nitrided layer, compared to the untreated core.
查看更多>>摘要：? 2022 Elsevier B.V.The introduction of heteroatoms into carbon materials is beneficial for enhancing zinc ion storage capability, and thereby obtaining excellent electrochemical performance. Herein, the N, S co-doped porous carbons (NSPCs) with well-developed pores and massive surface area are synthesized from natural biomass by the synergistic activation strategy of KHCO3 and Na2S2O3. Accordingly, NSPCK achieves high capacitance (262.7 F g?1) and long cycle life (remains 99.3% after 10,000 cycles) in 1 M Zn(CF3SO3)2 aqueous electrolyte for supercapacitor. Impressively, the NSPC cathode presents high discharge capacity of 136.3 mAh g?1 in the voltage window of 0–1.8 V, good rate performance (86.5 mA h g?1 at 20 A g?1) and high energy density (122.6 W h kg?1) for zinc ion hybrid capacitor (ZHC). Besides, the ZHC delivers long-term life with 0.5% damage after 15,000 cycles. This study may facilitate the design of high-energy and safe electrochemical energy storage devices based on the heteroatom doping carbons and aqueous electrolyte.
查看更多>>摘要：? 2022Thermal sprayed ZrO2-based abradable coatings have shown great advantages in blade/shroud clearance control systems of aero-engine turbine components due to their good high-temperature stability and abradability. Dysprosia-stabilized-zirconia (DySZ) based Abradable Coating were deposited on the Ni-based single-crystal superalloy via atmospheric plasma spraying technique. Microstructure evolution behaviors of the ZrO2-based abradable coating and the substrate were examined after 1100 ℃ thermal cycling. Besides, variation of the residual stress of the top layer was measured by Raman spectroscopy. Nanoindentation tests were conducted on the polished cross-section samples to evaluate Young's modulus and hardness evolution behavior. Results indicated that the DySZ top layer exhibits superior phase stability and good thermal shock resistance during thermal cycling. Thermally Grown Oxide (TGO) layer, Inter-Diffusion Zone (IDZ), and Second Reaction Zone (SRZ) was detected with the prolongation of the heat treatment time. Correlation between the microstructure and residual stress, hardness, Young's modulus of the coating was discussed. This study aims to further understand the relationship between the coating evolution behavior and the service time.
查看更多>>摘要：? 2022Metallic 1 T-MoS2 exhibits higher conductivity and electrocatalytic activity for hydrogen evolution reaction (HER) than semiconductor 2 H-MoS2. However, 1 T-MoS2 is a metastable state on thermodynamics, which hinder its further application as catalyst for HER. In this work, we report a new strategy to prepare MoS2 @CoS2/G electrocatalysts (G=graphene) with high-percentage metallic 1 T-MoS2 phase through a simple hydrothermal method followed by sulfurization treatment. We show that the introduction of CoS2 and the sulfurization can both promote the formation of 1 T-MoS2 phase (87.94%) in the MoS2 @CoS2/G electrocatalysts, which leads to improved charge transfer efficiency and electrochemical conductivity, larger surface area, and extensive active sites. These properties ultimately lead to the significantly enhanced catalytic activity of MoS2 @CoS2/G for HER with a small overpotential of 118 mV at 10 mA cm?2, and a small Tafel slope of 53 mV dec?1, as well as excellent durability and cycling stability in acidic electrolyte.
查看更多>>摘要：? 2022 Elsevier B.V.The transition mixed spinel ferrites (SFs) are the components used in the current modern technology and these include better elements whose ionic radii and oxidation state for exploring their electrochemical (EC) - photoelectrochemical (PEC) water splitting properties. In the current work, Ca2+ - doped MgFe2O4 NPs are synthesized and characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) to examine the crystal structure and particle size. The EC characteristics such as cyclic voltammetry were used to perform the super capacitive (SC) behavior of Ca2+ - doped MgFe2O4 electrodes. The cyclic voltammetry measurements analysis confirmed the prepared electrode's EC activity behavior. The current study was performed to examine the EC behavior of Ca2+ - doped MgFe2O4 electrodes in 1 M KOH electrolytes. The Mg0.9Ca0.1Fe2O4 revealed a significant specific capacitance (SP) of 221.57 F g?1 at 0.33 A g?1 current density (CD). Accordingly, Mg0.9Ca0.1Fe2O4 may be employed as a favorable electrode for supercapacitor applications. The oxygen evolution reaction (OER) of Ca2+ - doped MgFe2O4 electrodes was performed as electrocatalysts in 1 M KOH. The Mg1?xCaxFe2O4 (x = 0.1, 0.3 & 0.5) NPs could be significant agents for PEC water splitting applications. The current study may lead to a new insight into the growth of a new class of mixed transition SFs for energy and environmental applications.
查看更多>>摘要：? 2022 Elsevier B.V.A bimetallic structure prepared by directed energy deposition (DED) can simultaneously meet multiple property demands in service. However, in existing studies, formation mechanism and controlling method of transition zone (TZ) remain elusive due to narrow TZ in Functionally graded Materials (FGMs). In this article, a bimetallic structure of Ti17 and γ-TiAl alloy with a wide transition zone prepared by DED was obtained with special powder feeding method, and microstructure of TZ was studied in more details. According to change of element content and microstructure, the wide transition zone (TZ) is distinguished as TZ1 and TZ2. With the increase of Al content from TZ1 to TZ2, α phase grows up and (α2+γ)lamellar precipitates according to a certain burgers orientation relation. Meanwhile, massive γ phase nucleates at α grain boundary, and β phase transforms into ordered phase B2. Microhardness of TZ1 is much higher than that of Ti17 because the effect of solid-solution strengthening. The microhardness of TZ2 is reduced by precipitation of softer phases (α2+γ)lamellar and massive γ. In TiAl, the increase of Al content leads to coarsening of (α2+γ)lamellar and massive γ, so microhardness declines. The sequence of phase transitions in different zones is simulated and the results are consistent with the observed microstructure. Due to low strength microstructure with coarsening α phase and fine (α2+γ)lamellar, the average tensile strength of gradient sample at room temperature is only 167 MPa, and fracture shows typical cleavage fracture characteristic.
查看更多>>摘要：? 2022 Elsevier B.V.A stacking fault tetrahedron (SFT) is a very common kind of defects in face-centered cubic (FCC) metals under irradiation environment. The migrating GB can heal the SFT through dislocation reactions. To explore the healing mechanisms and conditions required, the low-angle GB interactions with an SFT in pure Ni and Ni-Fe bicrystals were investigated using molecular dynamics (MD) simulations. Ni-Fe bicrystals have higher healing efficiency on SFT than pure Ni due to their more diverse dislocation reactions. The addition of Fe atom can reduce the stacking fault energy (SFE), so that most of stair-rod dislocations (SRDs) of SFT in Ni-Fe bicrystals can be transformed into Shockley partial dislocations (SPDs) through the energetically unfavorable reactions. As a result, the vacancies of SFT are redistributed and some of them are carried away by migrating GBs. In pure Ni, however, only a small part of SRDs can undergo the energetically unfavorable reactions, and the SPDs generated would spontaneously be transformed back to SRDs after the GB-SFT interaction. The healing efficiency on SFT can be gradually enhanced with the increasing Fe atom concentration and elevated temperature.
查看更多>>摘要：? 2022 Elsevier B.V.In this study, the growth mechanism and its influence on the phase transition and magnetocaloric effect of FeRh films grown on MgO, LaAlO3, SrTiO3, and PMN-PT substrates were studied. The results demonstrate that different growth mechanisms are possessed in these FeRh films, although the orientation and lattice parameter are similar for these substrates. Thus, various strains and local disorder are generated in FeRh films, resulting in manipulation of the phase transition and magnetocaloric effect within them. The transition temperatures of FeRh films are tuned from 342.5 K to 382.5 K by changing substrates, whereas their entropy changes (ΔS) are comparable with that of the bulk FeRh. As a result, regulated entropy changes and refrigeration capacity in a wide temperature span have been achieved, reaching 80 (65) K with ΔS exceeding 6 (10) J/kgK. This study provides direct experimental evidence for the feasibility of broadening the working temperature span of first-order phase transition materials via epitaxial growth, exhibiting their potential in microelectronic circuitry.
NSTL
Elsevier