查看更多>>摘要：? 2022 Elsevier B.V.A series of LiMn2O4 cathodes with different Mn3+ contents are synthesized by a hydrothermally assisting method combined with a high-temperature solid phase process based on manganese-based metal organic frameworks (MOFs). The effect of NaOH addition on the morphology, structure and electrochemical properties of the LiMn2O4 cathode is investigated. The obtained samples all exhibit obvious octahedral morphology, corresponding to the cubic spinel structure with high crystallinity. Sample LMO-3 prepared with three times the molar amount of NaOH as PTA has the highest Mn3+ content, approximately 46.02%. The (100) and (110) crystal planes are exposed due to the higher Mn3+ content and the special truncated octahedral morphology, which endows LMO-3 with higher capacity and excellent rate performance. Specifically, the first specific capacity of LMO-3 is 140.6 mAh·g?1 at a rate of 1 C, and the capacity retention is 102.82% after 500 cycles. The corresponding capacity retention is 90.2% after 1000 cycles at 10 C. The spinel LiMn2O4 cathode synthesized by taking manganese-based MOFs as a precursor has great potential in practical applications.
查看更多>>摘要：? 2022 Elsevier B.V.We report the presence of austenite and its magnetostructural transition to martensite resulting in a large magnetocaloric effect in Ti doped Ni-Co-Mn-Sn textured ribbons. The evolution of the microstructure, micro-texture and the dynamics of the magnetostructural transition were studied for the as-spun and annealed Ni41.5Ti0.5Co9Mn39Sn10 ribbons. The as-spun ribbons revealed the evolution of a cubic superstructure of B2 ordering at room temperature, which is the characteristic of the austenite phase. The as-spun ribbons possess a strong preferred orientation at room temperature wherein, the< 100 > ║ND fiber texture is the dominant contribution at 90.2%. The austenite is ferromagnetic in nature and undergoes a magnetostructural transformation to weak magnetic martensite at 283.4 K. A large value of the isothermal entropy change of 6.62 J/kg/K, relative cooling power of 114.52 J/kg and an adiabatic temperature change of – 2.6 K have been calculated for a relatively low magnetic field change of 2 T. The annealing and quenching of the ribbons led to the grain growth as well as an overall suppression of the magnetostructural transformation. The austenite phase showed an overall enhancement in its magnetization when field cooled down to low temperatures of 4 K. The presence of strain glass clusters generated in the B2 lattice during the quenching process could be accounted for the observed behavior.
查看更多>>摘要：? 2022 Elsevier B.V.We investigated the microstructure and the crystallography of martensite variants in Ti–Pd–Hf alloy using electron microscopy. The martensitic transformation temperature decreased with increasing amount of Hf substituted into the Ti50?xPd50Hfx alloy. No indication of a martensitic transformation was observed in the as-quenched Ti25Pd50Hf25 and Ti10Pd50Hf40 alloys, even when the samples were cooled to 150 K. The Ti40Pd50Hf10, Ti35Pd50Hf15, and Ti30Pd50Hf20 alloys were composed of a B19 orthorhombic phase having plate-like habit-plane variants consisting of both major and minor correspondence variants several hundred nanometers in width and several tens of micrometers in length at room temperature. Lattice-invariant shear of these alloys was a {111}B19 Type I twin. A solution-treated sample of the Ti25Pd50Hf25 alloy consisted of a B2 cubic matrix with local atomic displacement and lattice distortions, and rounded H-phase particles several tens of nanometers in diameter were precipitated inside the B2 matrix upon aging of the specimen at 823 K for 10.8 ks. The as-quenched Ti10Pd50Hf40 alloy contained rounded H-phase particles several tens of nanometers in diameter embedded in a B2 matrix at room temperature. The martensitic transformation temperature in the Ti50?xPd50Hfx alloy was drastically decreased by both the fully coherent nanosized H-phase particles and the short-range order originating from clustering of solute atoms.
查看更多>>摘要：? 2022 Elsevier B.V.Oxygen deficiency is a common phenomenon in the sintering process of nickel ferrite spinel, and has a significant impact on the properties of the NiFe2O4 sintered body. This work investigated the effects of oxygen deficiency on the evolution of the lattice defects in spinel crystal. The oxygen deficiency led to the generation of a non-stoichiometric nickel ferrite containing oxygen vacancies (NiFe2O4-δ). As the sintering temperature increased from 1150 °C to 1400 °C, the concentration of oxygen vacancies in NiFe2O4-δ increased, with a δ value increasing from 0.0014 to 0.0355 and a lattice parameter increasing from 8.3485 to 8.3567 ?. X-ray photoelectron (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy all showed that the crystal structure of NiFe2O4-δ belonged to the Fd3m space group with Fe2+ ions partially replacing Fe3+ in the octahedral sites. Furthermore, a tendency for NiFe2O4-δ to decompose to Ni alloy and Fe3O4 during sintering could be observed.
查看更多>>摘要：? 2022 Elsevier B.V.To investigate the interrelation of dynamic recrystallization and detwinning behaviors, especially during the inchoate deformation stage at elevated temperatures, a commercial rolled AZ31 Mg alloy sheet is pre-twinned along the transverse direction to introduce {10?12} tensile twins, then the uniaxial stretch deformation is conducted. Results reveal that the detwinning dominates the microstructure evolution at room temperature, 100 °C, and 150 °C, while the dynamic recrystallization participates at temperatures of 200 °C and 250 °C. Further, the continuous dynamic recrystallization and detwinning accommodate the strain at 200 °C, while the discontinuous dynamic recrystallization suppresses the detwinning and predominates the deformation at 250 °C. Under different deformation temperatures, the interaction of dynamic recrystallization and detwinning exhibits different influences on the microstructure. Non-basal slips are activated at elevated temperatures, which affects the dynamic recrystallization behaviors and accommodates deformation strain. The texture evolution is closely related to the microstructure evolution mechanisms. The detwinning plays a hardening role in strength while dynamic recrystallization has a softening influence, the eventual effect on strength depends on the temperature.
查看更多>>摘要：? 2022 Elsevier B.V.Broader visible light response, higher carrier separation efficiency and injection efficiency are extremely important methods to enhance photoelectrochemical (PEC) performances of WO3. In this work, FeOOH with the property of storing holes is firstly applied to modify WO3/Cu2O heterojunction as an interlayer, and the WO3/FeOOH/Cu2O ternary heterojunction with excellent PEC performances is obtained. The separation efficiencies of photoinduced carrier in bulk is enhanced to 29.33% with the formation of dual built-in electric filed as well as the storage of photoinduced carriers transferred from WO3 in FeOOH, which is 3.27 folds higher than that of bare WO3. With the synergistic effect of expanded light absorption and accelerated charges transfer, the photocurrent density of 2.14 mA/cm2 at 1.23 V vs. RHE is achieved by WO3/FeOOH/Cu2O ternary heterojunction. This work can be applied for reference to improve the PEC performance of other photoelectrodes through adequate utilization of storing holes interlayer.
查看更多>>摘要：? 2022 Elsevier B.V.The high temperature deformation behavior of a X30CrMoN15-1 high-nitrogen stainless steel has been investigated using uniaxial compression test in the temperature range of 850–1250 ℃ and strain rate of 0.001–10 s?1. An Arrhenius-based hyperbolic sine equation was used to establish the flow stress constitutive model of the alloy at high temperatures, and the activation energy was 385.5 kJ/mol. Processing maps based on the dynamic material model were developed for true strains of 0.2, 0.4, 0.6 and 0.8. The domain of the safe region was in two parts: first, a strain rate range of 1–10 s?1 and temperature range of 1000–1100 ℃, and second, a strain rate range of 0.3–0.001 s?1 and temperature range of 1100–1250 ℃. The deformed microstructure at 1050 °C was characterized at different strain rates, strong< 100 >fiber textures parallel to the compression axis developed during high temperature deformation, and the strength gradually increased and became more concentrated with decreasing strain rate. The maximum dynamic recrystallization fraction and geometrically necessary dislocation densities were recorded at a medium strain rate (ε?=0.1s?1), which was more conducive than a low strain rate to the continuous dynamic recrystallization process. Discontinuous and continuous dynamic recrystallization both contributed to the microstructural evolution of the columnar grains studied in this research, but discontinuous dynamic recrystallization was the dominant mechanism.
查看更多>>摘要：? 2022 Elsevier B.V.Novel magnetic composites consisting of a polystyrene matrix containing La0.80Sr0.20Fe0.90Cu0.10O3-w (LSFC10) and La0.80Sr0.20Fe0.80Cu0.20O3-w (LSFC20) particles, each with two weight concentrations, 0.5% and 1.0%, are prepared by extrusion technique. The LSFC10 and LSFC20 filler phases are synthetized by citrate auto-combustion technique. From the XRD data, only a single crystalline phase, namely an orthorhombic perovskite structure, is observed. Additionally, the TEM images and EDX analysis show single phase compounds, confirming the absence of other phases. SEM images of the composites show the presence of perovskite nanoparticles, aggregated in structures with dimensions in the order of ten microns or lower, probably due to their magnetic interactions. Differently to bare particles, showing a single-phase hysteresis loop, the room temperature field-dependent magnetization loops of polymer composites exhibit a wasp-waisted-like magnetic hysteresis loops, which may origin from different mechanisms that likely emerge when the particles are dispersed in the matrix, such as the particle surface spin canting and the interparticle interactions, along with a physical rotation of the particles that are not firmly blocked in the polymer matrix.
查看更多>>摘要：? 2022A novel refractory high-entropy alloy (RHEA) spherical powder WTaMoNbZr was synthesized successfully through four-steps: melting, hydrogenation, crushing and spheroidization. The alloy ingot with ~110 mm in diameter and ~120 mm in height was prepared by vacuum electron beam melting. The ingot formed a single body-centered cubic (BCC) solid solution phase, with lattice parameters of 3.244 ?, thereby possessing a good combination of compressive stress (1973 MPa) and strain (17.63%). And this increased the difficulty to pulverize it into fine powder. It was found that hydrogenated treatment can embrittle the ingot, and irregular powders with the particle size ranging from 1.56 μm to 59.5 μm were then easily obtained by using a disk crusher. Finally, highly spheroidized RHEA powders with spheroidization ratio of 95.3% were fabricated by plasma spheroidization. After the plasma treatment, the powders possessed an average particle size of 37.5 μm and a single BCC phase structure was also obtained. The flow property and apparent density were 15.09 s?(50 g)?1 and 7.42 g?cm?3 respectively, indicating a better spheroidization effect. The nano-microhardness of the RHEA powder was 7.99 GPa, which was about 1.68 GPa higher than that of the bulky RHEA with the same composition. These excellent properties endow RHEA powder with broader potential applications, such as protective coatings, additive manufacturing. More importantly, this study provides a new approach to prepare spherical RHEA powder, which is of great significance for the further development.
查看更多>>摘要：? 2022 Elsevier B.V.Flexible piezoresistive sensors (FPS) are important components of wearable electronics for human-machine interaction, human physiological signal monitoring and electronic skin. In this work, carbon nanotube (CNT)-polydimethylsiloxane (PDMS) (abbreviated as CP) composite materials with hierarchical porous structures were prepared by a facile solvothermal method. The electrical conductivity and mechanical elasticity of the porous structure CP composite materials can be separately tuned by varying the CNT mass fraction and PDMS composition ratio, respectively. A flexible piezoresistive sensor using porous structure CP composite materials as the sensing material was designed and fabricated. The optimized sensor exhibits a sensitivity of 0.59 kPa?1 in the pressure ranges of 0–260 kPa, a low detection limit of 12 Pa, a fast response time of 25 ms and outstanding cycling stability over 1,700 cycles. Such sensor design can be integrated into flexible wearable electronic devices for physiological signal monitoring in real-time.
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