查看更多>>摘要：Additive technologies are actively implemented in various industries. The actual task is a complex study of the properties of the products. In the present work, electrochemical studies of the heat-treated Ti-6Al-4V alloy manufactured by Direct Energy Deposition were carried out to determine the evolution of electrochemical and mechanical properties. The analysis of the structure and phase composition were compared with the results of electrochemical and mechanical properties. The effect of the lamellae size and phase composition on corrosion and mechanical properties is more pronounced for the DED Ti-6Al-4V alloy. It was determined that the best electrochemical properties are possessed by a heat treated sample at 800 °C. With an increase the temperature of the heat treatment up to 900 °C, the corrosion resistance decreases, however, the values of relative elongation increase.
查看更多>>摘要：Formaldehyde is one of the most serious threats to human health in modern interior decoration. Thereby, online detection of indoor formaldehyde concentration has become an urgent problem. In this work, the Pt deposited porous SnO2 nanospheres were synthesized as the formaldehyde sensing materials, which were prepared by hydrothermal and chemical reduction methods. The diameter of as-synthesized Pt-SnO2 were centered in the range of 30–50 nm, with the dominant pore size of ~10 nm and the specific surface area of 89.79 m2 g?1, which provided a raft of passages and active sites for gas molecules to diffuse and interact mutually. Moreover, the experimental results demonstrated that the 1 wt.% Pt-SnO2 exhibited higher response (16.03), high-speed response time (9 s) and outstanding selectivity with exposure to low-concentration formaldehyde compared with original SnO2. The porous structures and catalytic effect of Pt nanoparticles were jointly responsible for the enhancement of SnO2 on sensing performance towards formaldehyde.
查看更多>>摘要：For decades, enhancing both strength and thermal stability in nanocrystalline materials for structural applications has been a significant challenge. Recently, entropy-based stabilization strategies for nanostructured materials have gained traction in the high-entropy alloy (HEA) community, however, such studies typically focus on synthesis techniques that require high energy input, such as severe-plastic-deformation or sputtering-based techniques. By contrast, electrodeposition offers itself as a low-energy and low-cost method of producing nanocrystalline materials, which has seen infrequent investigation in the HEA design space. Here we identify two nanocrystalline medium-entropy alloys (MEAs), NiFeCo (grain size, D = 13–360 nm) and NiFeCr (D ~ 1 nm), to serve as a baseline for the further development of higher-order quaternary and quinary systems. These alloys show enhanced thermal stability when compared to pure metal and binary alloy electrodeposits, and even nanocrystalline CoCrFeNiMn (made by high-pressure torsion) in the case of NiFeCr. Hardness values ranged from 3.4-5.5 GPa in NiFeCo and 4.6–8.5 GPa in NiFeCr, which are comparable with nanocrystalline HEAs made by other techniques. This study provides a framework for the development of nanocrystalline HEAs by electrodeposition, whose further development has the potential to accelerate the commercialization of HEAs, which currently have limited use despite their widespread acclaim in the materials community.
查看更多>>摘要：Miniaturization and low power dissipation are a trend for the development of ceramic-based microwave devices. Therefore, the decrease of the dielectric loss properties of microwave dielectric ceramic material compounds with a high dielectric constant is considered a quite important subject. In this work, the Ca0.61Nd0.26TiO3 material configuration with orthorhombic perovskite structure was thoroughly investigated by applying the strategy of (Al0.5Nb0.5)4+ substitution at the B-site. More specifically, the Ca0.61Nd0.26Ti1-x(Al0.5Nb0.5)xO3 sample with a nearly 60% increase in the quality factor (Q×f) was obtained. Also, the relationship between the structural and the electrical properties of Ca0.61Nd0.26Ti1-x(Al0.5Nb0.5)xO3 (0 ≤ x ≤ 0.15) samples were explored via performing X‐ray diffraction (XRD) measurements, Raman spectra, transmission electron microscopy (TEM) and calculation of the insulation resistance, etc. The extracted outcomes divulged that samples at x = 0–0.12 formed a single perovskite-structured phase, while the grain size of samples decreased by increasing the x value, leading to a drop decline of both the dielectric constant (εr) and electrical conductivity. Additionally, insights from the acquired Raman spectra confirmed that the stressed-rigid oxygen octahedral networks could lower the positive τf value of Ca0.61Nd0.26TiO3-based ceramic compounds. Interestingly, as the doping content of (Al0.5Nb0.5)4+ increased, the Ti3+ in samples was restrained at x = 0.04, whereas the insulation properties of the samples increased. Hence, the conductivity loss was declined. Furthermore, the TEM images illustrated the appearance of a 1: 1 ordered structure at the B-site of the (Al0.5Nb0.5)4+-doped samples. As a result, the Q×f value of the samples raised from 11,095GHz at x = 0–17,802 GHz at x = 0.12, enhanced by 60%. On top of that, for the sample with x = 0.15, the existence of the Ca2Nb2O7 phase deteriorated the microwave dielectric properties of the Ca0.61Nd0.26Ti1-x(Al0.5Nb0.5)xO3 samples, and especially Q×f value.
查看更多>>摘要：As one of the most promising electrode materials for lithium-ion batteries, silicon offers a high theoretical capacity, but it has been greatly limited by a volume expansion effect and the formation of unstable solid–electrolyte interface (SEI) film. Herein, Si@C/P nanoparticles with excellent electrochemical properties were prepared simply by sol-gel method and carbonization process. For lithium-ion batteries, phosphorus-doped phenol formaldehyde resin was used as carbon source for the first time, and phosphorus was successfully doped into carbon skeleton. The synergistic effect of carbon layer and phosphorus doping limits the volume expansion of silicon, and improves the diffusion rate of Li+. The Si@C/P anode exhibits a high initial Coulombic efficiency (ICE) of 84.4% and a specific capacity of 1873 mAh g?1 at 1 A g?1 after 100 cycles. The material shows a good rate performance, the average specific capacity reaches 1422.3 mAh g?1 even at a high current density of 4 A g?1, demonstrating a bright perspective.
查看更多>>摘要：Supercapacitor devices fabricated from capacitive and battery-type hybrid electrodes have been projected as a promising energy storage system because of their ability to produce high specific power and energy simultaneously. In this work, we have demonstrated a facile method of impregnation of faradaic type manganese (III) polyoxovanadate, [MnV14O40]?6 on the high surface area substrate of activated carbon (AC) as well as graphene oxide (GO). Materials and electrochemical characterizations data confirm the successful incorporation of capacitive and faradaic type manganese (III) polyoxovanadate into the nanohybrid electrode material. Furthermore, the synergic effect between the carbonaceous nanostructures (AC/GO) and redox-active oxometalate (MnV14) provides a better pathway for ion transport to the interface resulting in enhancement of the conductivity, diffusion ability of the nanohybrid. Moreover, the battery-type MnV14 clusters disperse in the micro/mesopores of AC, whereas the oxygen-containing functional groups in GO act as active sites for anchoring of MnV14 clusters. Thus, the surface modification with MnV14 clusters enhances the specific capacitance of nanohybrid with remarkable electrical and mechanical stability. The AC/MnV14 nanohybrid exhibits an enhanced specific capacitance of 547 F g?1 with specific energy and power of 76 Wh kg?1 and 1600 W kg?1, respectively, at 0.8 A g?1 current density. Additionally, GO/MnV14 shows a specific capacitance of 330 F g?1 with improved specific energy and power of 30 Wh kg?1 and 1276 W kg?1, respectively, at the same current density. Moreover, both the nanohybrids possess excellent cycle stability by retaining 92% (AC/MnV14) and 90.6% (GO/MnV14) of initial capacitance even after 5000 sweeping cycles.
查看更多>>摘要：The application of lithium-sulfur batteries (LSBs) encounters many problems including polysulfides shuttling, low sulfur conductivity and poor stability. To address these issues, a porous microsphere-based sulfur cathode, consists of Mg2+ etched ZIF-67 and carbon nanotubes encapsulated with graphene oxide (Mg ZIF-67/CNT@GO), was fabricated. The introduction of CNTs endows the composite with good electrical conductivity, and at the same time the loss of polysulfides is mitigated through its unique porous structure. Moreover, the Mg2+ etched ZIF-67 also provides a large area of active interface, which promotes its trapping with polysulfides and catalytic performance towards polysulfides conversion. Accordingly, the sulfur cathode with Mg ZIF-67/CNT@GO composite delivers good electrochemical performance. The battery exhibits a high capacity retention rate of 87.4% and an areal capacity of 3.35 mAh cm-?2 under 3.0 mg cm-2 sulfur loading at 0.2 C. In addition, the pouch cell cycled at 0.1 C retains its high capacity of 640.8 mAh g-l after 50 cycles. This work provides a promising sulfur cathode design approach for the implementation of LSBs.
查看更多>>摘要：Two-dimensional (2D) MXene materials have significant potential applications in electrochemical energy storage. A Ti3C2Tx MXene film can be used as a high-performance electrode for a flexible supercapacitor owing to its flexibility and excellent rate capability. However, Ti3C2Tx is usually only used as a negative electrode material because it can be easily oxidized under positive (anodic) potential. Herein, we report a simple filtration method to fabricate a hybrid cathode by mixing a colloidal solution of 2D Ti3C2Tx nanosheets and 1D MnO2 nanobelts to form an alternating MnO2/Ti3C2Tx stacked structure. Compared with pure Ti3C2Tx, the hybrid cathode has higher electrochemical stability toward anodic oxidation. The MnO2/Ti3C2Tx hybrid cathode delivers a high gravimetric capacitance of 315 F g?1 at 10 mV s?1 and a good rate capability of 166 F g?1 at 100 mV s?1. The high stability of the MnO2/Ti3C2Tx hybrid cathode is mainly attributed to the charge transfer-induced work function enlargement at the Ti3C2Tx and MnO2 heterointerface. Furthermore, a flexible asymmetric supercapacitor assembled using MnO2/Ti3C2Tx as the cathode and alkalized Ti3C2Tx as the anode delivers a high-voltage window up to 1.9 V. This work provides new insights for designing high-performance MXene-based cathode materials and devices for wearable electronics.
查看更多>>摘要：In the present work, microstructure and texture evolution during plastic deformation and annealing treatment of near beta (β), meta-stable β, and stable β-Ti alloys are reviewed. The evolution of microstructural features such as shear bands (SBs), martensite (α″/α′), dislocations and precipitation (omega (ω), and alpha (α) phases) during plastic deformations significantly influence the mechanical properties. Further, the microstructure and texture evolution in the deformed β-Ti alloys also depend on the deformation process like rolling, extrusion, and/or severe plastic deformation (SPD). The formation of α-fiber (RD// <110>) and γ-fiber (ND// <111>) are typically observed in cold-rolled and recrystallized β-Ti alloys. However, the fiber texture intensities or the volume fraction of these fibers and other texture components (Cube (100) <001>, Rotated Cube (100) <011>, Goss (110) <001> and others) varies from process to process. Dynamic recrystallization (DRX) and dynamic recovery (DRV) are influenced mainly by the imposed strain rate, activated deformation modes, and deformation temperature in β-Ti alloys. In general, the activation of deformation mechanisms viz. slipping, twinning, kinking, and SBs formation are primarily dependent on the reduction ratio and the composition of the β-Ti alloys. The formation of SBs and deformation twins contributes to the ductility of the β-Ti alloy sheets for structural/automotive applications. Moreover, the presence of α″/α′ and ω-phase showed an improvement in the strength of β-Ti alloys. β-Ti alloys such as Ti-Nb alloys are known for their acceptable biocompatibility and low young's modulus (E, 40–65 GPa). However, the formation of α′/α″ during plastic deformation leads to lowering of E.
查看更多>>摘要：High near-infrared (NIR) reflectivity and low thermal conductivity are desired in cooling pigments used in exterior coating of buildings. In this work, brown-red whisker-like sodium iron titanate pigment were synthesized using Na2CO3, TiO(OH)2 and Fe2O3 as the raw materials and NaCl as the flux. We explored the optimal preparation conditions of sodium iron titanate, and investigated the near-infrared reflection characteristics, thermal conductivity and thermal stability of sodium iron titanate. The results show that single-phase sodium iron titanate whiskers can be obtained after calcination at 900 °C for 4 h. The growth of sodium iron titanate whiskers conforms to the series-parallel growth mechanism, and the well-developed sodium iron titanate whisker has a high average reflectivity (81.43%) in the near-infrared band of 780–2500 nm. The sodium iron titanate whisker has a low thermal conductivity (0.136 W/mK, at room temperature), which is mainly attributed to the inherent tunnel crystalline structure. In addition, sodium iron titanate has good thermal stability in the temperature range from room temperature to 900 °C. The present brown-red NaFeTiO4 whisker is expected to be a candidate pigment for building energy conservation.
NSTL
Elsevier