查看更多>>摘要：? 2022 Elsevier B.V.AlxCoCrFeMnNi high-entropy alloys with different aluminum concentrations (x = 0.5, 1, and 1.5 at%) were synthesized by mechanical alloying followed by consolidation using two different sintering methods, conventional (CS) and high-frequency induction heat + conventional (HFIHS + CS). The results show the presence of FCC, BCC, and B2ordered phases in all systems, regardless of the sintering method. The BCC phase exhibits morphological changes (cuboidal-type and plate-like) associated with the two sintering methods involving different diffusion rates and affecting the hardness values. The M23C6 carbide is identified in systems sintered by the CS method; meanwhile, the M7C3 carbide is identified in the HFIHS + CS method. Finally, the HFIHS + CS method results in a higher level of densification (~95%) than the CS method (~80%).
查看更多>>摘要：? 2022 The Author(s)With this work we attempt to raise awareness of spinodal decomposition among the members of the ion implantation researcher community. In the literature about nanoparticle formation via ion implantation, spinodal decomposition is rarely mentioned. Probably because it is not associated with individual particles which are often the desired goal of the implantation process, but with contiguous, often “labyrinth-like" nanostructures. Using a modified version of the Stochastic Kinetic Modelling Framework (SKMF), we show that spinodal decomposition can directly form nanoparticles, too. Distinguishing nucleation and growth from spinodal decomposition and coarsening based only on the result is very difficult, often impossible, and researchers regularly rely solely on morphological identification, which, as we demonstrate here, can be misleading. The authors believe that understanding nanoparticle formation during and after ion implantation is a good way to initiate a step forward in nucleation theory development, and move away from the strong distinction between nucleation and spinodal decomposition to a more general phase separation theory.
查看更多>>摘要：? 2022 Elsevier B.V.The exploration of promising anode materials with high capacity represent great challenge for LIBs and SIBs. Zinc sulfide (ZnS), has attracted more attention owing to its high capacity and abundant resource. However, the poor cycle performance have seriously hinder the practical application, which induced by the seriously volume expansion during the lithiation process. In this work, in-situ growth of the ZnS nanoparticles (NPs) on 3D N-doped carbon architecture (ZnS/NC) have been prepared by a simple method. In such a architecture, the N-doped carbon can not only avoid the volume change of ZnS, but also much improve the conductivity of hybrids, as well as facilitate a fast ions/electrons transport. As a result, the ZnS/NC composite exhibits outstanding cycle performance (377.1 mAh g?1 after 400 cycles at 1.0 A g?1) and outstanding rate performance (404 mA h g?1 at 3 A g?1) for LIBs. As for SIBs, a high reversible capacity of 244.1 mAh g?1 is obtained after 900 cycles at 1.0 A g?1, and high even at 3.0 A g?1, high reversible capacity of 241 mAh g?1 is also achieved, demonstrating excellent cycling performance and rate performance.
查看更多>>摘要：? 2022 Elsevier B.V.The chemical etch pitting method is a powerful technique to reveal dislocations in semiconductor materials; however, a reliable etchant has not been established for β-Ga2O3. In this work, we performed a comparative study of two etchants, molten KOH+NaOH and hot H3PO4, to reveal dislocations from the (?201) surface. Using transmission electron microscopy, it was determined that KOH+NaOH could reveal all grown-in dislocations. The dislocation outcrops were located at the pit cores. The pit shape, specifically, its symmetry in the [010] direction, had a close correlation with the line direction of the dislocations but there was no simple correlation with the Burgers vector. On comparing H3PO4 with KOH+NaOH on the same sample, the results indicated that both etchants could reveal dislocations with a large angle to the (?201) surface but H3PO4 could not reveal dislocations nearly parallel to this surface. Surface damage induced by polishing produced etch pits in both etchants with smaller dimensions than those of the grown-in dislocations.
查看更多>>摘要：? 2022 Elsevier B.V.The layered lithium nickel manganese oxide LiyNixMn1?xO2 cathode materials with O2 structure exhibit good cyclic stability owing to their special arrangement of oxygen layers. However, the O2-type oxides generally present limited discharge capacity because of Li+ ions defects in the lithium layer (as in LiyNixMn1?xO2, y < 1). Herein, an O2-type layered lithium nickel manganese oxide LiNi0.33Mn0.65Al0.02O2 with high capacity and good capacity retention is obtained by introducing lithium and aluminum into the transition metal layer. The results of structural characterization and performance tests show that the optimal amount of Li+ and Al3+ in the transition metal layer effectively inhibits the disordered migration of transition metal ions and increases the electrochemical stability. The LiNi0.33Mn0.65Al0.02O2 cathode delivers an initial discharge capacity of 153 mAh g?1 and the capacity only attenuates 13% after 100 cycles at the current density of 200 mA g?1, which are higher than that of undoped oxide LiNi0.33Mn0.67O2.
查看更多>>摘要：? 2022 Elsevier B.V.A powder metallurgy processed metastable Ti-10V-3Fe-3Al alloy is thermo-mechanically processed for obtaining two phase (α and β) microstructure. Subsequently, the alloy is compressed up to 0.4 (true) strain. Deformation mechanisms of the compressed sample are then thoroughly investigated. Stress-strain curve uniquely displays double yielding with serrated flow that are characteristics of formation of deformation twins, martensite in the constituent phases. In α phase, {1?011}〈1012?〉α deformation twin is found to be operative. In β phase, {112}〈111〉β twin with stress-induced α″ martensite are formed. For the first time, a simultaneous operation of twinning in both β (bcc) and α (hcp) is noticed in a titanium alloy. α″ martensite layer formation at β/α interface is also observed. These operational mechanisms have been discussed based on the β phase stability and atomic movement in (11?01) planes of α phase. These results will greatly benefit in designing in new titanium alloy with desired mechanical properties.
查看更多>>摘要：? 2022We report an in-depth study on exotic magnetic nature including giant exchange bias in single layered Ruddlesden-Popper structure polycrystalline perovskites SrRCo0.5Mn0.5O4 (R = Pr, and Nd). X-ray diffraction, neutron diffraction, and Raman spectroscopic studies on both compounds confirm tetragonal crystal structure with I4/mmm space group. Temperature evolution of dc magnetization and ac susceptibility show multiple magnetic phase transitions in both the compounds, i.e., high temperature ferromagnetic transition (Tc = 178/172 K) followed by antiferromagnetic transition at an intermediate temperature (TN = 90/100 K) and finally entering to a glassy magnetic state at lower temperatures (Tg = 35/25 K). Neutron powder diffraction confirms the absence of long-range magnetic order in both compounds. Atomically disordered (Co/Mn)O2 layers give rise to intralayer short range 3d-3d magnetic interactions resulting in co-existence of ferromagnetic and antiferromagnetic regions producing frozen magnetic state below Tg. Present experimental results and analysis show giant exchange bias of ? 3.6/? 1.7 kOe (Pr/Nd systems) under cooling field of 50 kOe at 5 K, which stems from the inherent magnetic inhomogeneity. Our results reveal that magnetic rare-earth ion (Pr/Nd) induces a pathway of interlayer 4f-3d magnetic interactions leading to antiferromagnetic interaction between adjacent (Co/Mn)O2 layers, and this has a significant influence on the exchange bias values at low temperature.
查看更多>>摘要：? 2022 Elsevier B.V.Lithium-sulfur (Li-S) battery possess the advantage of high specific energy but suffer from unstable cyclic performance due to the sluggish liquid-solid conversion kinetics causing severe lithium polysulfides (LiPS) shuttling. Designing multifunctional electrocatalysts with improved activity and abundant active sites to regulate the dynamics for sulfur electrochemistry is still a significant challenge. Herein, we proposed a thiourea assisted pyrolysis combined with hard template method to synthesize cobalt single atoms co-coordinated by N and S atoms embedded hollow carbon spheres (Co-NS-HCS) as a novel sulfur host. The Co-NS-HCS mainly consists of well-dispersed Co-N3S-C center sites where Co is co-bonded by N and S atoms. Systematical characterizations revealed that the Co-NS-HCS exhibit improved SRR electrocatalytic properties with higher exchange current density and larger electron transfer number than that of Co-N-HCS. When equipped in sulfur cathodes, the S@Co-NS-HCS exhibits superior rate performance (925 mAh g?1 at 2 C), long cycle stability (69.1% of capacity retention after 500 cycles at 1 C). Moreover, the assembled Li-S pouch type cell also exhibits competitive cyclic performance that work stably for 100 cycles at 0.1 C with a high capacity retention of 84.7%. This work furnishes a feasible scheme for the rational design of single atoms catalysts with improved electrocatalytic activity for sulfur cathodes based on the coordination environment regulation strategy.
查看更多>>摘要：? 2022 Elsevier B.V.A novel crack-free Ti-modified Mo alloy with good mechanical properties was fabricated successfully by laser powder bed fusion (L-PBF). The micro-Ti particles dissolve homogeneously into the Mo matrix. The homogeneous mixture of Ti in Mo does not allow the formation of any new secondary phases. The presence of Ti increases the resistance to deformation within the grains and hence, eliminates the formation of hot-tearing cracks between Mo grains. The presence of high compressive properties (compressive yield strength (656 ± 9 MPa) and fracture strain (18.2 ± 1.9%)) in the L-PBF Tiμm/Mo alloy sample may be attributed to the presence of a high degree of geometrically necessary dislocations (GNDs). The doping of Ti in Mo not only helps in the successful fabrication of L-PBF Mo but also improves their mechanical properties, which paves the way for the fabrication of high-performance Mo-based alloys by L-PBF via innovative alloy design.
查看更多>>摘要：? 2022 Elsevier B.V.The importance of ZT in thermoelectric (TE) materials is critical for green power generation and cooling applications. Therefore, tremendous efforts were underway to improve ZT, in which we proposed a layer structured approach by successively arranging of coarse Bi0.5Sb1.5Te3 (BST) and fine BST/0.07Cu microstructure materials and investigated their transportation mechanism. The dual bulk microstructure was well-bonded and confirmed by analyzing the microstructure through scanning electron microscope (SEM), electron backscatter diffraction analysis (EBSD) and simulated the electrical potential and temperature distribution during spark plasma sintering with COMSOL software. The results indicate that the highest power factor of 3.8 mW/m-K2 was attained in the layer structured sample, which is significantly higher than other samples due to its synergistically optimized electrical conductivity and Seebeck coefficient. Through the varied microstructure, the κ was decreased at 400 K and consequently the ZT was improved to 1.25 at 400 K for the layer structure samples. Therefore, it is suggested that layered arrangement of different microstructure material could improve the thermoelectric properties of materials.
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