查看更多>>摘要：The Ni-Al intermetallic sheets were prepared by the reaction synthesis of pure Ni and Al foils with different thickness ratios. The first stage was performed at 640 °C/20 MPa/6 h to consume Al layers, and the second stage was performed at 1200 °C/20 MPa/1 h to complete the synthesis of Ni-Al intermetallic sheets. The thickness ratios of original Ni and Al foils strongly affected the microstructure and mechanical properties of Ni-Al intermetallic sheets. When Ni/Al thickness ratio was 1:1.5 (R1:1.5), the microstructure was single-phase NiAl with bimodal grain structure, and it transformed into coarse grains dominated single-phase NiAl structure when Ni/Al thickness ratio was 1:1 (R1:1). The microstructures changed to NiAl+Ni3Al+Ni when the ratios were 1:0.63 (R1:0.63) and 1:0.25 (R1:0.25). At ambient temperature, Samples R1:0.25 and R1:0.63 had high strength, while Samples R1:1 and R1:1.5 showed serious brittleness. At high temperature, Sample R1:1 showed preferable ductility with the elongation of 61.3%, 71.4% and 101.3% at 800 °C, 900 °C and 1000 °C, respectively; Sample R1:0.63 showed the highest tensile strength, with the values of 350.3 MPa, 230.5 MPa and 140.2 MPa at 800 °C, 900 °C and 1000 °C, respectively. For the fracture at ambient temperature, Sample R1:0.25 showed a mixed fracture mode of dimple fracture and quasi-cleavage fracture; the fracture mode of Sample R1:0.63 was mainly cleavage fracture; Sample R1:1 showed a typical brittle cleavage fracture with a large number of river-like patterns; the fracture mode of Sample R1:1.5 was brittle transgranular fracture for coarse grain layers (CGLs) and intergranular fracture for fine grain layers (FGLs). At high temperature, Samples R1:1.5 and R1:1 were mixed fracture modes of dimple fracture and quasi-cleavage fracture; the fracture mode of Sample R1:0.63 was mixed quasi-cleavage and cleavage fracture; the fracture mode of Sample R1:0.25 was single cleavage fracture with microcracks at the NiAl layers.
查看更多>>摘要：The g-C3N4, Bi3NbO7 and g-C3N4/Bi3NbO7 photocatalysts were prepared. The phase, microstructure, element composition, optical and photochemical properties are revealed by XRD, FTIR, SEM and TEM, XPS, DRS, photocurrent response and EIS results. The FTIR, SEM, TEM and XPS measurements offer the evidence to the formation of electronic interaction in g-C3N4/Bi3NbO7 composites. The DRS indicates that g-C3N4/Bi3NbO7 has the lower Eg and thus has the higher harvest to visible light. The photocurrent response and EIS indicate that g-C3N4/Bi3NbO7 has higher separation efficiency of photogenerated e??h+ pairs than pure g-C3N4 and Bi3NbO7. The photocatalytic reduction of Cr(Ⅵ) indicates that g-C3N4/Bi3NbO7 is more effective than pure g-C3N4 and Bi3NbO7.
查看更多>>摘要：Hot forming-quenching integrated process was developed to fabricate aluminum alloy complex-shaped components by taking advantage of the enhanced formability at the temperature close to solution temperature. But, it is very difficult to evaluate the formability under biaxial tension state and continuous cooling conditions. A measuring method was proposed to evaluate the biaxial formability by combining solution heat treatment and hot gas free bulging test. The effects of temperature and pressurizing rate on the bulging ability and thickness uniformity of an Al-Mg-Si alloy sheet were clarified. The deformation mechanism was revealed by microstructure observation. It is found that excellent formability can be obtained under the high temperature with less heat loss and rapid pressurizing conditions. The limiting strain under rapid pressurizing condition decreases from 1.13 at 500 ℃ to 0.81 at 400 ℃, being at a high strain level. Thickness uniformity can be obviously improved at a higher deformation temperature accompanied by rapid loading due to the remarkable strain-rate hardening effect. Dynamic recovery is the main restoration mechanism, resulting in numerous substructures and unchanged grain size. The obtained biaxial formability closer to actual forming condition can provide fundamental guidance for forming aluminum alloy complex-shaped component by hot forming-quenching integrated process.
查看更多>>摘要：A powder metallurgy process for manufacturing hard magnetic alloy Fe–30Cr–16Co (wt%) was optimized. An acceptable level of magnetic properties of the alloy was reached upon sintering within the temperature range 1100–1400 °C (with a maximum at 1350 °C; Br = 1.21 T, Нс = 54.6 kA/m, and (BH)max = 37.6 кJ/m3) and at an overall duration of thermal treatment of 15 h. Lowest magnetic properties (Br = 1.12 T, Нс = 48.6 kA/m, and (BH)max = 31.1 KJ/m3) were observed at 1100 °C most likely due to higher porosity of about 7%. After full thermal treatment with temperature of thermomagnetic stage, 670 °C, we observe the presence of non-magnetic σ-phase, which leads to a sharp drop in magnetic properties. Based on the magnetic measurements at intermediate stages it can be deduced that the σ-phase is formed during the 2nd stage of thermal treatment during cooling down from 670° to 580°C Significant ductility is observed upon material failure during compression tests; fracture strain (εf ?100%), around 40%. Yield strength, compressive strength, and linear thermal expansion for obtained alloys are presented. The yield strength decreases with increasing sintering temperature within the range 1100–1400 °C due to grain growth.
查看更多>>摘要：In this study, texture c-axis//ND of ZK61-T6 Mg alloy was reoriented towards c-axis//ED, TD and tilted in between ED and TD in a ZK61-PC Mg alloy through cross pre-compression. Subsequently, quasi-static and dynamic mechanical behaviour was examined. The results showed that compressive yield strength, ultimate compressive strength and elongation to fracture were considerably increased from 140 to 220 MPa, 374–437 MPa and 0.15–0.16, respectively. This increase was the synergistic effect of texture, grain refinement through twin boundaries and pre-induced dislocation hardening effect. In addition, an exceptional increase of ultimate compressive strength (531 MPa) was obtained under dynamic loading. The microstructure evolution of deformed specimens revealed that the propensity and width of the adiabatic shear band were increased with an increase in strain rate in ZK61-PC Mg alloy. In addition, twinning, de-twinning,<a> and<c+a> dislocation inside the twin and the matrix absorbed the high-stress energy and provided a higher mechanical response in ZK61-PC Mg alloy. The twinning induce rotational dynamic recrystallization mechanism was responsible for the development of fine grains. Based on the results, it is recommended that pre-compression is a practical way to increase the efficiency of the ZK61 Mg alloy.
查看更多>>摘要：Non-linear optical (NLO) materials require a balance of high second-harmonic generation (SHG) signal and laser damage threshold (LDT), as well as phase matchable behavior. Herein, we report a new member of the (RE)6(TM)x(Tt)2Q14 family of compounds, La6PdSi2S14, which, unlike all other reported TM analogues crystallizing in hexagonal P63 space group, crystallizes in the non-centrosymmetric monoclinic P21 space group. The crystal structure contains chains of edge-sharing distorted square planar [PdS4] units. The square-planar coordination of Pd in La6PdSi2S14 exhibits remarkable NLO properties with high SHG (3.7 × AgGaS2) and LDT (3 × AgGaS2) values as well as phase matchability. This shows the promise of novel materials with distorted structural motifs for enhanced NLO properties. Upon formation of bimetallic chiral sulfides containing both Cu and Pd, Cu occupies the opposite faces of the octahedra forming [CuS3] units while Pd can be stabilized in the center of PdS6 octahedra in the hexagonal P63 crystal structure of La6Pd0.5CuSi2S14. This suggests that it is possible to form mixed metal systems which could further enhance NLO properties by incorporation of additional structural distortions.
查看更多>>摘要：The draining of industrial waste into natural water sources is creating severe destruction to the environment by contaminating the water. Here, 2D/2D nitrogen-doped g-C3N4/In2S3 nanocomposites (NGI) were developed by varying concentrations of Ngcn {337 mg (NGI-1), 675 mg (NGI-2) and 1350 mg (NGI-3), respectively} by simple polycondensation-reflux method. The remediation of organic pollutants from wastewaters was performed by as-prepared photocatalysts periodically. PXRD reveals the monoclinic and cubic structure of Ngcn and In2S3 respectively. FESEM and TEM images confirm the sheet-like morphology with the average size of ~ 500 nm whereas D-spacing values in SAED patterns resemble XRD peaks for both Ngcn and In2S3 respectively. Moreover, the XPS technique was performed to confirm the elemental compositions of Ngcn and In2S3 photocatalysts. The maximum pore size (20.44 nm) and pore volume (1.15 cc/g) of NGI-2 nanocomposite were observed by BET results. NGI-2 showed the maximum photodegradation efficiency ~ 99% in 10 min with photodegradation rate (0.141/min) that is ~ 2 folds than pristine indium sulfide (InS) and 8-folds than nitrogen-doped g-C3N4 (Ngcn). Moreover, NGI-2 showed a good adsorption capacity of 5.02 mg/g which is 2-folds than Ngcn. The enhanced adsorption capacity along with photocatalytic degradation of NGI-2 could be attributed to a high rate of electron-hole pair separation due to the combined effect of band gap, large surface area and interface formation. The industrial sewage analysis was also examined by NGI-2 and found significant photodegradation efficiency.
查看更多>>摘要：Fe6Ge5 was synthesized from the elements both as single crystals and a polycrystalline powder. Its crystal structure was reinvestigated in a wide temperature range using high-resolution powder and single-crystal X-ray diffraction. The crystal structure of Fe6Ge5 is connected with those of other iron germanides and features an alternation of iron-rich and germanium-rich layers. The magnetic behavior was studied by magnetization measurements on a single crystal and 57Fe M?ssbauer spectroscopy. The results of both methods showed that a peculiar two-step antiferromagnetic ordering (TN1 = 110 K, TN2 = 330 K) takes place, with the part of iron magnetic moments remaining disordered between the transitions. Such behavior originates from the large number of both symmetrically and locally distinct iron atoms that form a weakly connected iron framework and yield the competition between ferromagnetic and antiferromagnetic interactions.
查看更多>>摘要：The microstructure and electrochemical properties of Li1.125Ta0.875-xNbxZr0.125SiO5 (x = 0, 0.0625, 0.1875, 0.25, 0.5) ceramics prepared via the solid-phase reaction method were studied. The results reveal that the conductivity of the ceramic specimens at 25 °C increases and then decreases as the Nb increases from 0 to 0.5 mol. 0.1875 mol of Nb doping facilitates the fusion and connection between grains, reduces the number of grain boundaries, leads to densification of the ceramics, decreases the total resistance, and thus increases the conductivity. Moreover, the small structural distortion caused of the discrepancy in ionic radii of Ta5+ and Nb5+ creates more space to accommodate Li ions and promotes the diffusion of Li+, reducing the energy potential barrier for ion transport. The best performing Li1.125Ta0.6875Nb0.1875Zr0.125SiO5 has a conductivity of 3.521 × 10-5 S/cm at 25 °C, with an order of magnitude greater than that of the original sample Li1.125Ta0.875Zr0.125SiO5, reaching 2.288 × 10-4 S/cm at 150 °C and has a minimum activation energy: 0.225 eV. The prepared Li1.125Ta0.6875Nb0.1875Zr0.125SiO5 ceramic is a new type of fast Li-ion conductor with potential for application in all-solid-state batteries.
查看更多>>摘要：Ta2O5 memristors exhibit bipolar switching properties attributable to the growth and destruction of oxygen vacancy filaments (OVFs). The transmission properties of biological synapse are mimicked in these memristors. The Ta2O5 memristor that contains numerous oxygen vacancies (OVs) is heated under N2 at 10 Torr, and it shows high conductance modulation linearity (CML) because the variation of OVF is governed by the redox reaction. The recognition accuracy of artificial neural networks (ANNs) is affected significantly by the CML of the memristor. Simulation using a convolutional neural network reveals that this Ta2O5 memristor exhibits a high learning accuracy of 93% because of its high CML. Spike-timing-dependent plasticity (STDP) was realized in Ta2O5 memristors. The change rate of synaptic weight variation in the STDP curve, which is also related to the learning accuracy of ANNs, is large in the Ta2O5 memristor heated under N2 at 10 Torr; this confirms that this memristor has a good learning accuracy. Spike rate-dependent plasticity and the transition from short-term plasticity to long-term plasticity are observed in Ta2O5 memristors. Further, they were obtained at a small potentiation spike in a Ta2O5 memristor heated under N2 at 10 Torr because numerous OVs exist in this memristor.
NSTL
Elsevier