Search

The Mo alloys reinforced by Al2O3 particles were fabricated by hydrothermal synthesis and powder metallurgy. The microstructures of Mo−Al2O3 alloys were studied by using XRD, SEM and TEM. The results show that Al2O3 particles, existing as a stable hexagonal phase (α-Al2O3), are uniformly dispersed in Mo matrix. The ultrafine α-Al2O3 particles remarkably refine grain size and increase dislocation density of Mo alloys. Moreover, a good interfacial bonding zone between α-Al2O3 and Mo grain is obtained. The crystallographic orientations of the interface of the Al2O3 particles and Mo matrix are [ 1 ¯ 11 ] α - Al 2 O 3 / / [ 1 ¯ 11 ] Mo and [ 1 1 ¯ 2 ] α - Al 2 O 3 / / [ 0 1 ¯ 1 ] Mo . Due to the effect of secondary- phase and dislocation strengthening, the yield strength of Mo−2.0vol.%Al2O3 alloy annealed at 1200 °C is approximately 56.0% higher than that of pure Mo. The results confirm that the addition of Al2O3 particles is a promising method to improve the mechanical properties of Mo alloys.

Nano-sized α-Al2O3 ceramic-particle-reinforced molybdenum alloy plates were fabricated by a series of processes including hydrothermal synthesis, powder metallurgy, and rolling. The quantitative effect of α-Al2O3 ceramic (particle size and volume fraction) on the microstructures and mechanical properties of molybdenum alloy plates was investigated. Nano-sized α-Al2O3 ceramic particles were obtained and uniformly dispersed in the molybdenum matrix. The α-Al2O3 ceramic refined the molybdenum grains and remarkably increased the microhardness, elastic modulus, and yield strength. The yield strength of the alloy reached a peak value when the α-Al2O3 ceramic content was 1.28 vol% and increased by 61.07%–90.2% compared with that of pure molybdenum after annealing at 1000 °C-1300 °C. A quantitative yield strength model correlating α-Al2O3 particle size, α-Al2O3 volume fraction, molybdenum grain size, and annealing temperature was built. This model attributes the strengthening of alloy to the synergy effects of grain refinement strengthening (σHP) and Orowan strengthening (σp). The addition of fine α-Al2O3 ceramic resulted in Orowan strengthening and fine molybdenum grains, thereby increasing yield strength of alloy.

In inorganic–organic perovskites, the three-dimensional arrangement of the organic group results in more subtle balance of charge, spin and space, thereby providing an attractive route toward new multiferroics. Here we report the existing of multiple ferroic orderings in inorganic–organic layered perovskites with relative strong hydrogen bond ordering of the organic chains intra plane. In addition, the inter plane in perovskite is stacking via van der Waals force. However, such magnetoelectric coupling properties for this compound have not been reported since it is difficult to characterize the properties in single crystals since most of the hybrid perovskites are usually deliquescent and unstable when exposed to air. To deal with these problems, we synthesized a (CH3NH3)2CuCl4 single crystal by using a simple evaporation technique, and demonstrated ferroelectric, magnetic and magneto-electric properties of (CH3NH3)2CuCl4. The internal hydrogen bonding of easily tunable organic unit combined with 3d transition-metal layers in such hybrid perovskites make (CH3NH3)2CuCl4 a multiferroic crystal with magnetoelectrical coupling and offer an new way to engineer multifunctional multiferroic.

Hot compression and dynamic recrystallization (DRX) behavior corresponding to the second phases of as-cast Mg-4.3Li-4.1Zn-1.4Y (wt.%) alloy was investigated in the range of 250–450 °C and 0.001–10 s−1. True strain-true stress curves showed typical characteristics DRX process. Constitutive relationship yielded an average activation energy (Q) and stress exponent (n) of 147.183 kJ/mol and 5.49, respectively. The hot deformation was mainly controlled by climb of edge dislocations, which turned into cross-slip of screw dislocations at ≥400 °C. The volume fraction of second phases changed the dislocation movement and resulted in the variation of the rate-controlling mechanism. The peak power dissipation efficiency (η) was observed at 450 °C/0.1 s−1 (32%), and the corresponding uniform and fine microstructure was attributed to the dynamic precipitation and complete DRX from uniformly distributed second phase particles. A wide flow instability region was observed at all temperatures and relatively high strain rates, corresponding to the non-uniform microstructure of the incomplete DRX and deformation band composed of ultrafine DRXed grains, which resulted from local distributed second phase particles. DRX process was attributed to the nucleation at second phase particles by the mechanism of particle stimulated nucleation (PSN), and the incomplete DRX process was accompanied by the dynamic recovery (DRV) process.

UDP-glucose pyrophosphorylase (UGPase) is an important pyrophosphatase that reversibly catalyzes the synthesis of UDP-glucose during glucose metabolism. We previously found that the deletion of UGPase may affect structure, growth, the virulence of Brucella, and the activation of cellular NF-κB. However, the exact mechanism of activation of NF-κB regulated by Brucella UGPase is still unclear. Here, we found for the first time that UGPase can regulate the expression of virB proteins (virB3, virB4, virB5, virB6, virB8, virB9, virB10, and virB11) of type IV secretion system (T4SS) as well as effectors (vceC, btpA, btpB, ricA, bspB, bspC, and bspF) of Brucella by promoting the expression of ribosomal S12 protein (rpsL), BMEI1825, and quinone of 2,4,5-trihydroxyphenylalanine (topA) proteins, and further inhibits the activation of cellular NF-κB and affects the virulence of Brucella. Our findings provide new insights into the mechanism used by Brucella to escape the immune recognition, which is expected to be of great value in the designing of Brucella vaccines and the screening of drug targets.

Hybrid materials of chitosan–silica (CS–SiO2) with nonprecious-metallic ions (Cu) immobilized on (Cu–M@CS–SiO2) were developed as green catalysts for degrading 1,1-dimethyl hydrazine (UDMH) wastewater. SEM, XRD, EDX, and FT-IR were employed for characterizing the catalysts. Results indicated that metal ions were chelated with N or N and O atoms of CS–SiO2. The efficiency of UDMH degradation, chemical oxygen demand (COD) removal and the concentration of N-nitrosodimethylamine (NDMA) were used to evaluate the catalytic activity. The catalysts were firstly combined into the process of catalytic wet peroxide oxidation (CWPO) for the degradation of UDMH wastewater with H2O2. Based on the study of the effects of different metallic ions, anions and reaction factors on the catalyst activity, the optimal conditions for CWPO with M@CS–SiO2 were determined, the H2O2 dosage and temperature were 3.0 mL and 65 °C, respectively. Under these conditions, the treatable UDMH concentration was 500 mg L−1, obtaining the high efficiency of UDMH degradation and COD removal (100% in 10 min and 87.38% in 30 min, respectively) and the low concentration of NDMA (0.31 mg L−1). The catalyst activity was less affected within six reaction cycles. Meanwhile, owning a huge surface area and strong adsorption performance, this kind of hybrid material can rapidly degrade, adsorb, and separate pollution.

Transition metal perovskite chalcogenides, a class of materials with rich tunability in functionalities, are gaining increased attention as candidate materials for renewable energy applications. Perovskite oxides are considered excellent n-type thermoelectric materials. Compared to oxide counterparts, we expect the chalcogenides to possess more favorable thermoelectric properties such as lower lattice thermal conductivity and smaller band gap, making them promising material candidates for high temperature thermoelectrics. Thus, it is necessary to study the thermal properties of these materials in detail, especially thermal stability, to evaluate their potential. In this work, we report the synthesis and thermal stability study of five compounds, \alpha-SrZrS$_3$, \beta-SrZrS$_3$, BaZrS$_3$, Ba$_2$ZrS$_4$, and Ba$_3$Zr$_2$S$_7$. These materials cover several structural types including distorted perovskite, needle-like, and Ruddlesden-Popper phases. Differential scanning calorimeter and thermo-gravimetric analysis measurements were performed up to 1200{\deg}C in air. Structural and chemical characterizations such as X-ray diffraction, Raman spectroscopy, and energy dispersive analytical X-ray spectroscopy were performed on all the samples before and after the heat treatment to understand the oxidation process. Our studies show that perovskite chalcogenides possess excellent thermal stability in air at least up to 600{\deg}C., Comment: 9 Figures

The high-temperature properties of the molybdenum sheet doped with 1.0 wt%Al2O3 particles were investigated. The Al2O3 particles have a good bond with the Mo matrix and there exists an amorphous transition layer at the interface between Al2O3 particles and Mo matrix in the as-rolled sheet. The tensile strength of the Al2O3-doped Mo sheet is higher 23–62% than that of the pure Mo sheet at room and high temperatures, with its recrystallization temperature increased by about 200 °C than that of the pure Mo sheet. Furthermore, the fracture and strengthening mechanisms were discussed.

Mo/ZrO2–Y2O3 composites were successfully prepared through high-energy ball milling and powder metallurgy technique. The morphologies of the composite powders, the microstructures and properties of the sintered compacts and rotary swaged compacts were studied. The results show that ZrO2 addition refined the grains of composite powders and Mo alloys by promoting grains nucleation and inhibiting grains growth. Tetragonal zirconia (t-ZrO2) was completely stabilized at room temperatures by Y2O3 and evenly distributed in the molybdenum matrix. Moreover, ZrO2 was bonded with Mo matrix by an interfacial bonding zone. All above microstructures improve the mechanical properties and recrystallization temperature of the composites. The added values of yield strength, tensile strength and elongation of the doped Mo alloys after annealing all exceed 30% at room temperature, compared with pure Mo. ZrO2 particles make an effect on dispersion strengthening and improving recrystallization temperature by hindering dislocations movement.

Hot deformation behavior of as-cast Mg-5Li-3Zn-0.3Y (wt.%) alloy has been studied by establishing processing maps covering the range of 200-450 °C in temperature and 0.001-10 s−1 in strain rate. The map corresponding to the strain of 0.7 reveals that a domain of dynamic recrystallization occurred at 340-400 °C/0.01-0.158 s−1 with its peak efficiency of approximately 31%. Analysis of the flow behaviors and microstructural observations indicated that dynamic recrystallization occurred in the domain, in which fine microstructure can be achieved. The above conditions represent the optimum processing parameters, and the flow instability regimes are also recognized from the maps. The average deformation in the deformed range was 136.414 kJ/mol which is close to that for lattice self-diffusion in magnesium and far smaller than that for as-cast Mg-5.75Zn-0.73Y-0.36Zr (wt.%) alloy. It is believed that a lower activation energy for Mg-5Li-3Zn-0.3Y alloy can partly result from both the weak particle pinning effects and adding Li into the Mg-Zn-Y-Zr alloy. Results of extrusion experiments conducted at 350 °C show that the alloy can be easily extruded with good mechanical properties of the yield strength of 132 MPa, the fracture strength of 215 MPa and the elongation of 20.9%, and the grains can be well refined.

Transition metal perovskite chalcogenides (TMPCs) are explored as stable, environmentally friendly semiconductors for solar energy conversion. They can be viewed as the inorganic alternatives to hybrid halide perovskites, and chalcogenide counterparts of perovskite oxides with desirable optoelectronic properties in the visible and infrared part of the electromagnetic spectrum. Past theoretical studies have predicted large absorption coefficient, desirable defect characteristics, and bulk photovoltaic effect in TMPCs. Despite recent progresses in polycrystalline synthesis and measurements of their optical properties, it is necessary to grow these materials in high crystalline quality to develop a fundamental understanding of their optical properties and evaluate their suitability for photovoltaic application. Here, we report the growth of single crystals of a two-dimensional (2D) perovskite chalcogenide, Ba3Zr2S7, with a natural superlattice-like structure of alternating double-layer perovskite blocks and single-layer rock salt structure. The material demonstrated a bright photoluminescence peak at 1.28 eV with a large external luminescence efficiency of up to 0.15%. We performed time-resolved photoluminescence spectroscopy on these crystals and obtained an effective recombination time of ~65 ns. These results clearly show that 2D Ruddlesden-Popper phases of perovskite chalcogenides are promising materials to achieve single-junction solar cells., 4 Figures

Optical anisotropy is a fundamental building block for linear and nonlinear optical components such as polarizers, wave plates, and phase-matching elements1–4. In solid homogeneous materials, the strongest optical anisotropy is found in crystals such as calcite and rutile5,6. Attempts to enhance anisotropic light–matter interaction often rely on artificial anisotropic micro/nanostructures (form birefringence)7–11. Here, we demonstrate rationally designed, giant optical anisotropy in single crystals of barium titanium sulfide (BaTiS3). This material shows an unprecedented, broadband birefringence of up to 0.76 in the mid- to long-wave infrared, as well as a large dichroism window with absorption edges at 1.6 μm and 4.5 μm for light with polarization along two crystallographic axes on an easily accessible cleavage plane. The unusually large anisotropy is a result of the quasi-one-dimensional structure, combined with rational selection of the constituent ions to maximize the polarizability difference along different axes.

The dry sliding tribological characteristics of B 4 C-hBN ceramics with different contents of hBN against GCr15 bearing steel under two different test modes (upper disc on bottom pin test mode and upper pin on bottom disc test mode) have been evaluated using a pin-on-disc friction and wear tester. The experimental results show that, with increasing hBN content, the dry sliding tribological characteristics of B 4 C-hBN/GCr15 bearing steel pairs have different variation rules under two different test modes. Under upper disc on bottom pin test mode, with increasing hBN content, the friction coefficients of B 4 C-hBN/GCr15 bearing steel pairs decrease firstly and increase subsequently; however, under upper pin on bottom disc test mode, the friction coefficients of B 4 C-hBN/GCr15 bearing steel pairs increase continuously with increasing hBN content. In this paper, the possible reasons for these interesting results are most deeply discussed.

This paper focuses on the microstructures and frictional wear behaviors of high-speed steel (HSS) with high molybdenum content under different rolling-sliding conditions using self-made wear tester. Results showed that the molybdenum element in HSS mainly formed M 2 C-type carbide ((Fe 27.42 Mo 48.26 Cr 24.32 ) 2 C). M 2 C (21-1) is coherent with α-Fe (110). The sliding ratio has a significant influence on frictional wear behaviors. As sliding ratio increases from approximately 1%–10%, the frictional coefficient rises and then decreases, and the wear weight loss rises obviously because the wear mode varies from fatigue to sliding wear. The high stress rolling-sliding contact can cause not only fracture and desquamating of M 2 C, but also martensitic transformation in subsurface. The martensitic transformation contributes in improving hardness and wear resistance.

Dynamic nano precipitation behavior of as-cast Mg-4Li-4Zn-Y alloy during high temperature compression at 450 ℃ was investigated in this paper. The grains were coarse, interdendritic W-Mg3Y2Zn3 mainly existed at grain boundaries and MgZn2 mainly existed in grains in the as-cast alloy. After hot deformation at 400 ℃/0.1 s−1 and 450 ℃/0.1 s−1, complete dynamic recrystallization occurred, MgZn2 was dissolved and Mg24Y5 appeared. Compared with 400 ℃, the number of second phases was more and grains were finer at 450 ℃. Bulk W-Mg3Y2Zn3 particles were broken and partly dissolved during hot deformation, and Zn and Y atoms diffused from grain boundaries into inner grains. Diffused atoms were aggregated at defects caused by deformation, then nano precipitates with a size of tens of nanometers formed at these places without growth. High-density ultrafine nano precipitates with a size of several nanometers were also found. Grains were refined due to PSN progress promoted by relatively large particles and growth restraint by nano precipitates at grain boundaries. The combined strengthening effect of particle dispersion and grain refinement can significantly improve the mechanical properties. Texture in the alloy was randomized during high temperature deformation as well, which was beneficial to reduce mechanical property anisotropy.

The Mo-ZrO 2 alloys were prepared by a hydrothermal synthesis and a powder metallurgy process. The grain size, density and hardness of the alloy sintered compacts were investigated. The deformation behavior of the alloy at high temperature was studied by using a Gleeble-1500D thermal simulated test machine. The strengthening effect of zirconia particles was found during the deformation process of the alloy at high temperature. The result shows the mechanical properties of the Mo-ZrO 2 alloys were obviously improved due to the uniform distribution of the small second phase. After adding ZrO 2 , the hardness of the alloys has increased by 40%, and the high temperature strength of the alloy was increased. At the temperature of 1400 °C, the strength of the alloys was increased by 35% compared with that of the pure molybdenum. The ZrO 2 particles can effectively improve the deformation resistance, resulting in increase of the mechanical properties of the Mo-ZrO 2 alloys.

In this article, we report a hybrid microstructure design strategy for preparing tungsten alloy reinforced by Y 2 O 3 -stabilized cubic ZrO 2 (W-ZrO 2 (Y)) with high compressive strength and critical failure strain. The processing route involves a molecular-level liquid–liquid doping technique combined with vertical sintering and hot rotary swaging that causes the uniform distribution of cubic ZrO 2 (Y) particles in the grain interior. The cubic ZrO 2 (Y) particles in tungsten matrix are prepared by liquid–liquid incorporation of Zr(NO 3 ) 4 and Y(NO 3 ) 3 aqueous solutions. The alloy powders with 1.5 wt% ZrO 2 (Y) present nano/microbimodal distribution. The cubic ZrO 2 (Y) particles are also uniformly distributed in the grain interior of refined tungsten grains, which consequently improves the relative density, Vickers hardness, compressive strength, and critical failure strain of alloy. The compressive strength and critical failure strain of the swaged W-1.5 wt% ZrO 2 (Y) alloy are 1680 MPa and 0.24, which are approximately 24.9% and 33.3% higher compared with those of pure tungsten, respectively. The strengthening mechanism of W-1.5 wt% ZrO 2 (Y) alloy is also discussed.

Tungsten alloys reinforced by in-situ tetragonal zirconia (W–ZrO 2 ) were developed via the azeotropic distillation method combined with the powder metallurgy method. The microstructure and abrasive wear properties were studied. The in-situ ZrO 2 particles in the tungsten matrix were obtained by the decomposition of zirconium nitrate after liquid–liquid incorporation of (NH 4 ) 6 H 2 W 12 O 40 and Zr(NO 3 ) 4 aqueous solution. The ZrO 2 particles were distributed evenly in the tungsten matrix, which refined tungsten powders and the grains of tungsten alloys significantly. The density and Vickers hardness of the tungsten alloys decreased with increasing ZrO 2 mass fraction. However, the wear resistance increased firstly and then decreased with increasing ZrO 2 mass fraction. The optimal amount of ZrO 2 for improving wear property is 3%, with the wear resistance of W–3% ZrO 2 improving by approximately 20%–40% compared with that of pure tungsten. The proper amount of ZrO 2 particles can efficiently prevent microcutting to protect the tungsten matrix, thereby enhancing the wear resistance of tungsten alloys.

This study aims to investigate the effect of the potential window on heat generation in carbon-based electrical double layer capacitors (EDLCs) with ionic-liquid (IL)-based electrolytes using in operando calorimetry. The EDLCs consisted of two identical activated-carbon electrodes with either neat 1-butyl-1-methylpyrrolidinium bis(trifluoromethane-sulfonyl)imide ([Pyr14 ][TFSI]) electrolyte or 1.0 m [Pyr14 ][TFSI] in propylene carbonate (PC) as electrolyte. The instantaneous heat generation rate at each electrode was measured under galvanostatic cycling for different potential windows ranging from 1 to 4 V. First, the heat generation rates at the positive and negative electrodes differed significantly in neat IL owing to the differences in the ion sizes and diffusion coefficients. However, these differences were minimized when the IL was diluted in PC. Second, for EDLC in neat [Pyr14 ][TFSI] at high potential window (4 V), a pronounced endothermic peak was observed at the beginning of the charging step at the positive electrode owing to TFSI- intercalation in the activated carbon. On the other hand, for EDLC in 1.0 m [Pyr14 ][TFSI] in PC at potential window above 3 V, an endothermic peak was observed only at the negative electrode owing to the decomposition of PC. Third, for both neat and diluted [Pyr14 ][TFSI] electrolytes, the irreversible heat generation rate increased with increasing potential window and exceeded Joule heating. This was attributed to the effect of potential-dependent charge redistribution resistance. A further increase in the irreversible heat generation rate was observed for the largest potential windows owing to the degradation of the PC solvent. Finally, for both types of electrolyte, the reversible heat generation rate increased with increasing potential window because of the increase in the amount of ion adsorbed/desorbed at the electrode/electrolyte interface.

Pure molybdenum and ZrO2 dispersion strengthened Mo alloy were prepared by liquid-liquid doping method. The effects of adding ZrO2 on their microstructure and properties were investigated by tensile test and low cycle fatigue (LCF) test at room temperature, and the fracture mode and energy absorption were analyzed. The research shows that ZrO2 can refine the grain size and increase the recrystallization temperature of molybdenum alloy. The enhancement of yield strength by ZrO2 is mainly reflected in grain boundary strengthening. The tensile fracture mode is related to grain size, and changes from transgranular fracture to transgranular-intergranular fracture with the decrease of grain size. At the initial stage of the cycle, the increase of strain amplitude changes the cyclic hardening into cyclic softening, and the addition of ZrO2 accelerates the cyclic hardening/softening. With the increase of strain amplitude, the loading energy and absorption energy of a single stable cycle increase, while the unloading energy is basically unchanged. ZrO2 can increase the total fatigue absorption energy of molybdenum alloy at the same strain amplitude, and the single cycle absorption energy is lower than that of pure Mo, thus increasing the fatigue life.

The fast-expanding electric vehicle market demands eco-friendly, high-performance, and low-cost energy storage systems. Lithium-sulfur battery with higher theoretical specific capacity and lower cost is regarded as a promising successor to lithium-ion battery. However, lithium-sulfur battery's polysulfide shuttling and lithium degradation have hindered its practical applications. In this study, cellulose fibers (CFs) were extracted from recycled paper hardboards by a simple alkaline treatment and then coated onto polypropylene separators by vacuum filtration. When being used as lithium-sulfur battery separators, the negatively charged functional groups on the CFs repelled polysulfide ions and redistributed lithium ions, enabling the assembled cells' superior stability and long life span. The lithium-sulfur battery with the recycle paper CF-coated separator exhibited a life span of over 800 cycles with a capacity retention rate of 71.69% and nearly no capacity decay after the initial formation cycles. The finding demonstrates that renewably produced, CF-coated polypropylene separators can simultaneously reduce the shuttle effect and degradation of lithium, paving the way toward commercially -viable and environmentally friendly lithium-sulfur batteries.

The article studies on the effect of slippage rate on frictional wear behaviors of high-tungsten high-speed steel (HTHSS) under high-pressure contact by using a self-made ring-on-ring wear machine. The microstructure of HTHSS is characterized by dual-scale tungsten carbides, including microscale eutectic M6C carbide [(Fe0.55W0.30Cr0.08Mo0.07)6C] and nanoscale secondary M6C carbide. Slippage rate has a significant effect on frictional wear behaviors. The peak value of friction coefficient occurs at the slippage rate of 5.5%. The friction coefficient will reduce whether the slippage rate increases or decreases. However, the increase in slippage rate makes wear failure mechanism change from fatigue to scratch, causing continuously significant increase in wear weight loss. The roles of different scale M6C carbides in resisting wear were also discussed.

MEPCMs have drawn tremendous attention in TES fields. In this study, eutectic of CA and PA was encapsulated by PVC, and the novel MEPCM for TES applications was developed. Microcapsules were prepared by solvent evaporation method and examined using DSC, SEM, LPSA, FTIR, thermal cycling test and TGA. DSC results demonstrated that the phase change temperature of CA-PA eutectic decreased after microencapsulation. The most satisfied sample was the MEPCM with a shell-core ratio of 1:2, which melted at 17.1 °C with the latent heat of 92.1 J/g, the encapsulation ratio was 57.7%. SEM images and LPSA results showed that the prepared MEPCMs were consisted with micro-sized spheres. FTIR results confirmed that the PCM core was successfully encapsulated by the PVC shell, and no chemical reaction was found among the components. The prepared MEPCM showed an excellent thermal reliability after 500 times of thermal cycling. Microencapsulation enhanced the starting temperature of CA-PA eutectic thermal decomposition, and the novel MEPCM exhibited an excellent thermal stability at working temperature from TGA results. Consequently, MEPCM (1:2) was the optimal composition and had great potential for TES applications.

This paper develops a new type of high-density iron-tungsten alloy (FWA) with high hardness and tensile strength by adding 15.6 wt% W into DT300 steel. The microstructure of FWA is characterized by separated network-like Fe7W6 around the grain boundary of ɑ-Fe matrix and nano-scale fine Fe2W particles are evenly distributed in the ɑ-Fe matrix, with some dispersive SiO2 particles. The new FWA has higher elastic modulus, micro-hardness, and tensile strength compared to DT300 steel. The micro-hardness and tensile strength of the FWA are 716.6 HV and 1267.7 MPa, which are approximately 18.1% and 6.5% higher than those of DT300 steel, respectively. The specific strength of new FWA is 1.49∗105 (N/m2)/(kg/m3), which is 1.8–4 times higher than that of tungsten heavy alloys. The high strength of FWA is attributed to the strengthening of the multiscale iron-tungsten intermetallic compound.

The limited solid solutions of nominal (1 − x) CuFeO2 − xCuAlO2 have been prepared by conventional solid-state reaction, and thermoelectric property has been measured. From the XRD powder pattern, we found that the major phase of the limited solid solution is rhombohedral delafossite structure when the composition is near the end members. Cubic Cu(Fe,Al)2O4 phase has been formed in composition from x = 0.4 to 0.8. Electrical resistivity of samples with major delafossite structure is lower than that of samples with Cu(Fe,Al)2O4 phase. In the zone of phase transform, the electrical resistivity can be got with lower value, such as x = 0.2, 0.3 and 0.9. The Seebeck coefficient for the limited solid solution with delafossite structure is positive in whole measured temperature range from 300 to 923 K. In the end, the power factor for the limited solid solution with major delafossite structure shows higher value, which is resulted from the lower electrical resistivity by the phase transposition. The highest power factor of 1.14 × 10−4 W/mK2 has been addressed at 907 K for x = 0.2, which value is enhanced by 3–4 times than that of pure phase CuFeO2 or CuAlO2.

A new Dy3+/Na+ co-doping system was attempted for improving the thermoelectric properties of CaMnO3 system in this paper. [Ca1-x(Na1/2Dy1/2)x]MnO3 samples were produced by the solid state reaction method, and the electrical properties and the microstructure were investigated. The X-ray diffraction data and tolerant factor were obtained, indicating the second phase and the geometric distortion in this system. Besides, compared with the resistivity and the Seebeck coefficient of single Dy-doped system, Dy3+/Na+ co-doping method could partially decrease the variation of carrier concentration as our expectation. More specifically, the holes introduced by doping Na+ could compensate electrons introduced by doping Dy3+, leading to a low variation of carrier concentration. As the result, a relatively high Seebeck coefficient (−251.6 μV/K) and a relatively low resistivity (8.7 mΩ cm) were gained in this system, and the highest power factor value of 298.0 μW/K2m was obtained at 323 K in [Ca0.95(Dy1/2Na1/2)0.05]MnO3.

The pure molybdenum sheet and the Al2O3-doped molybdenum alloy sheets were prepared by the hydrothermal method and a subsequent powder metallurgy process. The effects of Al2O3 particles addition on the recrystallization temperature, microstructures and properties of the Mo sheets were investigated as the focus. The Al2O3-doped Mo sheets have greater strength than the pure Mo sheet, and the 0.50 wt% Al2O3-doped Mo sheet has the best performance. For the unannealed specimens, the strength increases with the increase in Al2O3 content. Compared with that of pure Mo sheet, the strength of 0.50 wt% Al2O3-doped Mo sheet increases by 72 %, 54 %, 73 % and 76 %, respectively, when annealed at 1000, 1100, 1200 and 1300 °C, which is a very obvious reinforcement effect. When lower than 1100 °C, the elongation of the pure Mo sheet is the best. However, when the annealing temperature is equal to or greater than 1100 °C, the 0.50 wt% Al2O3-doped Mo sheet obtains the best elongation. Moreover, the Al2O3 addition can greatly improve the recrystallization temperature of molybdenum sheets; for example, the recrystallization temperature of the 0.50 wt% Al2O3-doped Mo sheet increases by 200 °C at least than that of the pure Mo sheet. Lastly, the strengthening mechanism was discussed.

Transition metal-carbon hybrids have been proposed as efficient electrocatalysts for hydrogen evolution reaction (HER) in acidic media. Herein, effective HER electrocatalysts based on metal-carbon composites are prepared by controlled pyrolysis of resin containing a variety of heavy metals. For the first time, Cr2 O3 nanoparticles of 3-6 nm in diameter homogeneously dispersed in the resulting porous carbon framework (Cr-C hybrid) is synthesized as efficient HER electrocatalyst. Electrochemical measurements show that Cr-C hybrids display a high HER activity with an onset potential of -49 mV (vs reversible hydrogen electrode), a Tafel slope of 90 mV dec(-1) , a large catalytic current density of 10 mA cm(-2) at -123 mV, and the prominent electrochemical durability. X-ray photoelectron spectroscopic measurements confirm that electron transfer occurs from Cr2 O3 into carbon, which is consistent with the reported metal@carbon systems. The obtained correlation between metals and HER activities may be exploited as a rational guideline in the design and engineering of HER electrocatalysts.

Mo-0.5Ti and Mo-0.1Zr alloys were prepared by powder metallurgy. In Mo-0.5Ti and Mo-0.1Zr alloys, there appears the second-phase particles of Ti2O3 and ZrO2 respectively, each of which can effectively prevent the dislocation activity in the process of plastic deformation. The addition of Zr can increase the strength of molybdenum alloys. Meanwhile, the ZrO2 formed from the alloy element Zr can refine the grains of molybdenum alloys to improve the recrystallization plasticity. After annealing, the tensile strength decreases while the plasticity greatly increases compared to the annealed Mo-0.5Ti and Mo-0.1Zr alloys. With the increase of annealing temperature, both the tensile strength and plasticity of Mo-0.5Ti and Mo-0.1Zr alloys decrease. Compared with pure Mo, after annealing the properties of the Mo-0.5Ti alloy and the plasticity of the Mo-0.1Zr alloy significantly increases.

A novel type of alumina (Al2O3)-doped molybdenum (Mo) alloy sheet was prepared by a hydrothermal method and a subsequent powder metallurgy process. Then the characterization of α-Al2O3 was investigated using high-resolution transmission electron microscopy as the research focus. The tensile strength of the Al2O3-doped Mo sheet is 43–85% higher than that of the pure Mo sheet, a very obvious reinforcement effect. The sub-micron and nanometer-scale Al2O3 particles can increase the recrystallization temperature by hindering grain boundary migration and improve the tensile strength by effectively blocking the motion of the dislocations. The Al2O3 particles have a good bond with the Mo matrix and there exists an amorphous transition layer at the interface between Al2O3 particles and the Mo matrix in the as-rolled sheet. The sub-structure of α-Al2O3 is characterized by a number of nanograins in the $\left[ {2\bar{2}1} \right]$ direction. Lastly, a new computer-based method for indexing diffraction patterns of the hexagonal system is introduced, with 16 types of diffraction patterns of α-Al2O3 indexed.

A three-component metal catalyst was prepared and used in the process of catalytic wet peroxide oxidation (CWPO) for the degradation of unsymmetrical dimethylhydrazine (UDMH) in propellant wastewater with H2O2. It was structurally characterized using scanning electron spectroscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDX), and its catalytic activity was evaluated using indexes such as the efficiency of UDMH degradation and chemical oxygen demand (COD) removal and the concentrations of ammonia (NH3–N), formaldehyde (HCHO), total nitrogen (TN), total organic carbon (TOC) and N-nitrosodimethylamine (NDMA). Besides, the reaction system was monitored using UV-Vis full wavelength scanning spectroscopy and liquid chromatography-mass spectroscopy (LC-MS). As a result, it was observed that the degradation mechanism involved ˙OH attacking the amino group and homocoupling in UDMH with the simultaneous transformation of the active component CuII/I. Based on investigation of the reaction factors (H2O2 dosage, temperature, catalyst dosage, pH and initial concentration of UDMH) focusing on the removal of NDMA, the optimal conditions for CWPO with a three-component metal catalyst were determined. The high treatable concentration of UDMH (500 mg L−1), rapid rate and good reusability with a high efficiency of UDMH degradation and COD removal (99.9% in 10 min and 94.6% in 30 min, respectively) and the low concentration of NDMA are merits of the present catalyst.

Thermoelectric properties of La doped Sr 0.7 Ba 0.3 Nb 2 O 6- δ ceramics were investigated in the temperature range from 323 K to 1073 K. The electrical resistivity decreases due to the subsitution of La for Sr, leading to the enhancement of thermoelectric power factor in the heavily doped sample Sr 0.50 La 0.20 Ba 0.30 Nb 2 O 6− δ . Slight La-doping promotes the growth of Sr 0.7 Ba 0.3 Nb 2 O 6− δ grains, but it will be impeded in the heavily La doped samples. Thus, La heavily doped sample Sr 0.50 La 0.20 Ba 0.30 Nb 2 O 6− δ shows low thermal conductivity because of the phonon scattering caused by grain boundaries. The highest thermoelectric performance was observed in the sample Sr 0.50 La 0.20 Ba 0.30 Nb 2 O 6− δ , and the thermoelectric figure of merit reaches the maximum value ~0.22 at 1073 K.

In order to improve the performance of molybdenum, the Mo/Al 2 O 3 composites were prepared by using a hydrothermal method for the synthesis of the precursor powders and subsequent powder metallurgical processing. The morphologies of the composite powders and the microstructures and properties of the composites were investigated. Compared with the pure Mo powder, the grains of composite powders are smaller because of the existence of the fine Al 2 O 3 particles. The results from the sintered composites show that the fine Al 2 O 3 particles are evenly distributed in the Mo matrix and well bonded with the Mo matrix. With increasing Al 2 O 3 content, all the values of the micro-hardness, compressive strength and flow stress at 0.08 strain are increased. The strengthening effect is more remarkable at elevated temperatures. At room temperature, the compressive strength and the flow stress at 0.08 strain of the composite with 40 vol.% Al 2 O 3 are 1.67 and 2.01 times greater than those of pure molybdenum, respectively, while the values are up to 2.02 and 2.52 at 1100 °C.

A thermal fatigue testing machine was designed for evaluating the thermal fatigue resistance of materials with a protective atmosphere. And then, the thermal fatigue resistance of the molybdenum plate doped with Al2O3 particles was investigated, with the crack initiation and extending mechanism discussed. At the test temperature of 900 °C, the thermal fatigue resistance of pure molybdenum plate and composite molybdenum plate is almost equal. At the test temperature of 1200 °C, the crack propagation rate of the composite molybdenum plate is greater than that of the pure molybdenum plate at the prefabricated notch, and the thermal fatigue resistance of the composite molybdenum plate is obviously lower than that of the pure molybdenum plate. However, the anti-crack initiation ability of the composite molybdenum plate is better than that of the pure molybdenum plate, where there is no prefabricated notch.

Mid-wave infrared (IR) and long-wave IR spectral ranges are of growing interest in various applications such as thermal imaging, thermography-based remote sensing, and night vision. Materials widely used for IR photodetectors in this regime include cadmium mercury telluride alloys and nanostructures of compound semiconductor. The materials development for IR optics will drive down the cost of IR optical systems and enable larger scale deployment. Here, we report a mid-wave IR responsive material composed of earth abundant and non-toxic elements, Sr1+xTiS3. It has a highly anisotropic quasi-one-dimensional structure similar to hexagonal perovskites. We grew large, high quality single crystals and studied its anisotropic optical properties. We observed two distinct optical absorption edges at ~2.5 um and ~5 um, respectively, for linear polarizations along two principal axes. The material demonstrated strong and broadband linear dichroism spanning mid-wave IR and long-wave IR, with a dichroitic ratio of up to 22., 4 Figures

A change in the system Gibbs free energy can be used as a criterion for spontaneous reactions, including the ferroelectric domain switching process. In this work, a new effective graphical method is introduced to investigate the change in the Gibbs free energy of a grain system and intuitively represent the domain switching state since its expression is too complex to study directly. A barium titanate crystal is considered as an example, and only 90∘ domain switching is involved. We can obtain two kinds of applications by virtue of the graphical method by controlling different variables in the change of the free energy: one application involves a new form of a ferroelectric domain switching criterion that considers the effect of the grain size, and the other application involves the critical single-domain grain size. For different loading methods, there will be different critical single-domain grain sizes in ferroelectrics.

This study theoretically and rigorously validates the use of the recently proposed step potential electrochemical spectroscopy (SPECS) and multiple potential step chronoamperometry (MUSCA) methods and their fitting analysis for determining the respective contributions of electrical double layer (EDL) and faradaic reactions to charge storage in pseudocapacitive electrodes. The continuum modified Poisson-Nernst-Planck model coupled with the Frumkin-Butler-Volmer theory were used for simulating interfacial, transport, and electrochemical phenomena in pseudocapacitive electrodes. The model accounted for (i) electron transport in the electrode, (ii) reversible redox reactions, (iii) ion electrodiffusion in binary and symmetric electrolytes, (iv) ion intercalation into the pseudocapacitive electrode, and (v) steric repulsion due to finite ion size. First, typical experimental measurements obtained from the SPECS method were reproduced numerically for a planar pseudocapacitive electrode. The EDL and faradaic currents retrieved from the SPECS fitting procedure were found to be in excellent agreement with those defined from first principles and computed numerically. Here, the faradaic current was modeled in the SPECS method as a diffusion process accounting for interfacial charge transfer kinetics and IR drop. The resistance obtained by SPECS matched the internal resistance obtained from electrochemical impedance spectroscopy. Similarly, the EDL capacitance retrieved by SPECS corresponded to the differential capacitance obtained from cyclic voltammetry (CV). Finally, the CV curves were successfully corrected for ohmic polarization effect using the MUSCA method. Then, the capacitive and diffusive currents retrieved from the electrochemical analysis of CV curves corrected by the MUSCA method were in good agreement with the EDL and faradaic currents reconstructed from the MUSCA method.

The nano-sized ZrO2-reinforced Mo alloy was prepared by a hydrothermal method and a subsequent powder metallurgy process. During the hydrothermal process, the nano-sized ZrO2 particles were added into the Mo powder via the hydrothermal synthesis. The grain size of Mo powder decreases obviously with the addition of ZrO2 particles, and the fine-grain sintered structure is obtained correspondingly due to hereditation. In addition to a few of nano-sized ZrO2 particles in grain boundaries or sub-boundaries, most are dispersed in grains. The tensile strength and yield strength have been increased by 32.33 and 53.76 %.