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Journal of Alloys and Compounds
Elsevier Science S.A.
Journal of Alloys and Compounds

Elsevier Science S.A.

0925-8388

Journal of Alloys and Compounds/Journal Journal of Alloys and CompoundsSCIISTPEI
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    High temperature oxidation behavior and interface diffusion of Cr3C2-NiCrCoMo/nano-CeO2 composite coatings

    Li F.Li Y.Lu H.Qi X....
    15页
    查看更多>>摘要:? 2022 Elsevier B.V.The high-temperature oxidation resistance of chromium carbide cermet coating was improved by developing a novel Cr3C2-NiCrCoMo/nano-CeO2 (NCE) composite coating based on the collaborative modification of the multielement alloy adhesive phase. The present study aimed to investigate the influence of nano-CeO2 on the high-temperature oxidation resistance, interfacial element diffusion and oxidation mechanism of the coating deposited by the high-velocity oxygen fuel spraying technology (HVOF). The results showed that the novel NCE coating with the addition of 4 wt% nano-CeO2 resulted in lower oxidation rates of 0.10, 0.23 and 0.39 mg/cm2 at 700–900 °C and superior oxidation resistance compared with the original Cr3C2-NiCrCoMo (NCC) coating because of the improvement of the thickness and denseness of the oxide film. The addition of nano-CeO2 promoted the reaction between oxides and the content of spinel phases generated in the NCE coating oxide film. The oxide film of NCE coating with high content of spinel phases strongly inhibited on the ion diffusion, thus reducing the decarburization of the Cr3C2 particles at the coating-oxide film interface. The present study will contribute to improving the service life of chromium carbide cermet coatings in high-temperature oxidation environments and extending the application of coating.

    Al-Fe-Ge: Phase equilibria and new ternary compounds at 400 °C

    Reisinger G.R.Richter K.W.Effenberger H.S.
    10页
    查看更多>>摘要:? 2022 The Author(s)The ternary system Al-Fe-Ge was investigated for a partial isothermal section at 400 °C, evaluating the all-solid phase equilibria in the Al-rich corner of the system for the first time. Investigations with SEM/EDX were combined with extensive XRD studies using powder- as well as single-crystal techniques. Four new compounds labelled τ5 to τ8 were identified and characterized. Complex phase equilibria in the partial section with Fe < 50 at% include all ternary phases from τ1 to τ8 with the exception of τ2 which is replaced by the low-temperature phase τ5 at 400 °C. The τ5 phase (Al1?xFeGe1+x) was found to crystallize in a ternary variant of the La2Sb-type (I4/mmm) and was characterized by Rietveld refinements. The compound τ7 (Al4.5?xFeGe1+x) is related to the β-phase in the Al-Fe-Si system (Al4.5FeSi). Its crystal structure was determined by single-crystal XRD in space group Cmce. The crystal structures of τ6 and τ8 were not determined up to now, but their stability with respect to decomposition into neighbouring phases was confirmed by additional liquid-solid diffusion couple experiments at 470 °C.

    Microstructural evolution and cracking behavior of Hastelloy X superalloy fabricated by laser directed energy deposition

    Liu F.Huang C.Zheng H.Zheng Y....
    12页
    查看更多>>摘要:? 2022 Elsevier B.V.Hastelloy X (HX) block was fabricated by laser directed energy deposition (LDED). Microstructure evolution and cracking behavior of the as-deposited LDED HX were investigated. The results showed that the microstructure of LDED HX was composed of columnar grains with interior fine columnar dendrites, and some of the second phases (Laves, M6C, σ, M23C6) caused by micro-segregation can be observed at the inter-dendrite and grain boundary. From the bottom to the top of the sample, the grain size became coarser and the micro-segregation intensified due to the decreasing cooling rates. The formation of continuous γ-M23C6 eutectic at the grain boundaries led to the hot cracking at the middle and top of the sample. Hot cracking was determined to be caused by a stable liquid film and thermal stress. The liquid film was caused by continuous γ-M23C6 eutectic, and the stability of the liquid film was depended on dendrite coalescence undercooling, ΔTb, which was related to the misorientation angle θ. When the misorientation angle exceeds 11.6°, the dendrite coalescence undercooling, ΔTb> 0. The liquid film was stable at the grain boundary. Therefore, cracking always occurred at high angle grain boundaries (HAGBs). The stress concentration at the grain boundaries was intensified at the middle and top of the sample and provided the driving force for crack initiation and propagation. Carbide particles at the grain boundary promoted a pinning effect on the liquid feeding, which led to the liquation cracking propagating to solidification cracking.

    Effects of vanadium content on the high temperature oxidation behavior of NbTiZrAlV refractory complex concentrated alloys

    Lin Y.Guo Y.Dong Q.Tan J....
    11页
    查看更多>>摘要:? 2022 Elsevier B.V.Oxidation behavior and microstructural evolution of NbTiZrAlV refractory complex concentrated alloys (RCCAs) with vanadium (V) concentration of 3 and 11 at% were investigated at 500 and 800 °C in the air atmosphere. When NbTiZrAlV RCCAs were exposed at 500 °C, the oxidation behavior was controlled by internal oxygen (O) diffusion, and single oxide layer predominating by Ti2ZrO6 and Nb2Zr6O17 were produced after oxidation for 200 h. The mass gains of alloys with 3 and 11 at% V were 0.042 and 0.018 mg/mm2, and corresponding average thickness of oxide layer was 70 and 30 μm. As oxidation temperature was increased to 800 °C, volatilization of V2O5 brought out the aggravation of oxidation degree for NbTiZrAlV RCCA, and complex oxide layers consisting of Nb9VO25, Nb2Zr6O17 and TiO2 were obtained after thermal exposure for 24 h. The mass gains of alloys with the V content of 3 and 11 at% were 1.135 and 0.514 mg/mm2, and the average thickness of oxide layer was 500 and 300 μm, respectively. In both cases, the antioxidant performance of NbTiZrAlV RCCA was significantly improved by the increased content of V. And the enhanced oxidation resistance could be ascribed to the fact that the increase of V addition enhanced the atom diffusion resistance via minimizing mixing enthalpy and maximizing configurational entropy.

    Improving tensile property and thermal stability of the Cu-Ta alloy by alloying with Cr

    Li M.Chang Y.
    14页
    查看更多>>摘要:? 2022 Elsevier B.V.The wide applications of Cu-10Ta (at%) composite are limited due to the high cost of Ta element (24 wt%). In the present research, Cu-0.6Ta-0.6Cr and Cu-0.6Ta alloys with low Ta content were fabricated by mechanical alloying and spark plasma sintering. The results indicate that the thermal stability and tensile strength of Cu-0.6Ta-0.6Cr alloy are significantly increased by the addition of Cr. The microstructure characterizations reveal that the performance enhancement of Cu-0.6Ta-0.6Cr alloy is ascribed to the transformation of nanoparticles in the matrix from Ta to more stable Cr2Ta Laves and the refinement effects of these nanoparticles from 19.4 nm to 14.1 nm. This work provides a potential for the wide applications of Cu-Ta alloy with low Ta by alloying with Cr at elevated temperatures.

    Effect of zinc-based active sites on porous carbon and electrochemical properties in lithium-sulfur batteries

    Ren X.Lu C.Yuan S.Liu Z....
    13页
    查看更多>>摘要:? 2022 Elsevier B.V.Hierarchically porous carbon (HPC) is considered as one of the promising cathodes of lithium-sulfur batteries (LSBs) owing to its appealing merits. However, it is still preventing the shuttle effect poorly due to the weak interaction between nonpolar carbon and polar polysulfide (LiPS). Herein, we report a facile method to prepare polar hierarchically porous carbon by in-situ loading the different amounts of zinc-based active sites (p-HPC-X) onto the HPC materials. The close combination of a carbon interconnected skeleton and ZnS nanoparticles derived zinc-based active sites forms the strong interaction that suppresses the soluble polysulfide shuttle effect and catalyzes the kinetics redox reactions of lithium polysulfide/sulfide. Moreover, the effect of polar sites introduced in situ on the morphology/porosity of carbon materials is also focused on. Crystallization of zinc-based active sites during the freeze-drying process and self-assembly during carbonization allow the pore size distribution of porous carbon to be customized, which offers fast lithium-ion and electron transport channels. Due to the synergistic effect of the hierarchical pore structure and suitable polarity sites, the p-HPC-X exhibits high capacity and good cycling performance. Especially p-HPC-1, it yields a high reversible capacity of 683.7 mAh g?1 and a low fading rate of 0.041% per cycle over 900 cycles at a current density of 1 C. This work offers novel insights into realizing the effect of in-situ loaded active sites on pore structure and electrochemical performance in LSBs.

    Chemical nature of the enhanced energy storage in A-site defect engineered Bi0.5Na0.5TiO3-based relaxor ferroelectrics

    Zhai J.Yao Y.Chen J.Wu L....
    10页
    查看更多>>摘要:? 2022 Elsevier B.V.Defect engineering has attracted significant interest in perovskite oxides because it can be applied to optimize the content of intrinsic oxygen vacancies (VO) for improving their recoverable energy-storage density (Wrec). Herein, we design 0.84Bi0.5+xNa0.5-xTiO3-0.16KNbO3 (?0.02 ≤ x ≤ 0.08) relaxor ferroelectric ceramics with A-site defects and discuss the influence of VO on Wrec. The composition with x = 0.02 has a high Wrec (3.35 J/cm3) as well as a high efficiency (η = 91%) at 240 kV/cm, and exhibits excellent temperature, frequency, and fatigue stabilities. This optimized composition also provides a large discharge-energy-density (WD = 1.0 J/cm3), a high power-density (PD = 66 MW/cm3), a fast discharge-rate (122 ns) at 150 kV/cm, and favorable temperature-induced charge-discharge properties (CDPs). Electron paramagnetic resonance, X-ray photoelectron, and Raman spectroscopic results reveal that the outstanding comprehensive performance of the designed materials is attributed to the coupling effect of low contents of dimeric TiTi′?VO?× clusters and high contents of trimeric TiTi′?VO???TiTi′× clusters. This work provides key insights relevant for developing lead-free ceramics with excellent energy-storage properties (ESPs).

    Hollow FeS2 nanospheres encapsulated in N/S co-doped carbon nanofibers as electrode material for electrochemical energy storage

    Yin Y.Zhang Y.Lu J.Huang Y....
    12页
    查看更多>>摘要:? 2022 Elsevier B.V.Pyrite iron sulfide (FeS2) is a fascinating electrode material for energy reserve devices because of its high theoretical capacity, non-polluting nature and abundant resources. However, the practical application has been extremely inhibited owing to its poor rate capacity and short cyclability caused by volume change during charge/discharge processes. In this article, a novel nanocomposite that is hollow FeS2 nanospheres encapsulated in N/S co-doped carbon nanofibers (FeS2CNFs) was synthesized through electrostatic spinning. The FeS2CNFs nanocomposite demonstrates a terrific specific capacity of 511 F g?1 at 1 A g?1 for all-solid-state supercapacitors. The FeS2CNFs as electrode material for sodium-ion batteries (SIB) displays a specific capacity of 827.7 mAh g?1 and possesses a capacity of 490.6 mAh g?1 at 0.05 A g?1 after 200 cycles. The results indicate that this encapsulated structure can guarantee the integrity of electrode materials. And the abundant defects in carbon nanofibers caused by N/S co-doping may increase electrochemical reaction sites to facilitate charge transfer. The N/S co-doped FeS2CNFs nanocomposite exhibits a great potential for applying in SIB and supercapacitors.

    Ordered mesoporous carbon/molybdenum carbide nanocomposite with high electrochemical performance asymmetric supercapacitor

    Abdolahi B.Gholivand M.B.Shamsipur M.Amiri M....
    8页
    查看更多>>摘要:? 2022Supercapacitors are a different promising technique to satisfy the rising demand for energy storage systems. Introducing an economical and highly active electrocatalysts is crucial to exploit clean and environmental-friendly energy technology in the future. We have successfully manufactured a supercapacitor based on ordered mesoporous carbon/ molybdenum carbide (OMC/Mo2C) nanocomposite. OMC has been chosen as a substrate due to its conductivity, favorable physical strength, high flexibility, and light structure. The OMC/Mo2C nanocomposite electrode performed exceptionally well from electrochemical perspective, with a high capacity of 1718 F g?1 at 1 A g?1 current density. It was seen that the capacitance retention rate could still reach 90.3% after 5000 cycles, indicating that the OMC/Mo2C nanocomposite electrode has excellent stability. Moreover, the assembled OMC/Mo2C//AC asymmetric supercapacitor exhibits capacitance of 299.4 F g?1 at a current density of 1 A g?1, and a large energy density of 106.4 Wh kg?1 at a power density of 800 W kg?1, by exceptional cycling stability with 90% capacity maintenance after 5000 cycles. The research findings can be applied in the development of high-performance energy storage devices based on carbides of transition metals.

    Temperature-dependent yield strength and deformation mechanism of a casting Ni-based superalloy containing low volume-fraction γ′ phase

    Ou M.Li H.Ma Y.Liu K....
    10页
    查看更多>>摘要:? 2022 Elsevier B.V.This study investigates the temperature-dependent yield strength and deformation mechanism of a new casting Ni-based superalloy K4750. This alloy exhibits yield strength anomaly (YSA) at 650–750 °C though it contains only low volume-fraction γ′ phase (22%). Using the interrupted samples after ~1.0% plastic strain, the dominant deformation mechanisms at the initial yielding stage are identified as: (ⅰ) (anti-phase boundary)APB-coupled dislocation pairs shearing γ′ from room temperature to 650 °C, (ⅱ) dislocations bypassing γ′ and creating loops above 650 °C, and (ⅲ) dislocations overcome γ′ by the thermally activated cross-slip and local climb at 850 °C. Additionally, with the proceeding of deformation, superlattice stacking faults shearing is active above 750 °C, implying that the deformation mechanism changes as the deformation progresses. According to the theoretical calculation, the critical resolved shear stress of Orowan looping decreases faster than APB shearing with the temperature increase, which is in agreement with the observed transition of deformation mechanism. Moreover, the remaining loops hinder the movement of subsequent dislocations, resulting in severe dislocation entanglement and high dislocation density in the heterogeneous slip bands, contributing to YSA. By contrast, dislocations can easily surmount γ′ phase by cross-slip and climb at 850 °C, leading to a rapid degradation of yield strength.