查看更多>>摘要：Materials of perovskite-type structure have been widely investigated for their prospect in photocatalysis. In this work, a novel composite material of p-type LaFeO3 microsphere coated with n-type In2S3 nanoparticles was fabricated to settle the water pollution problems through a mild hydrothermal method. The structure and morphology were studied by XRD, SEM, TEM, EDX mapping and UV–visible absorption spectra. The results indicated that the LaFeO3/In2S3 heterostructured photocatalyst was prepared successfully, and show an enhanced BET surface area and visible light absorption. The obtained heterostructured photocatalyst was applied to the photocatalytic degradation of rhodamine B (Rh B), tetracycline (TCH) and brilliant blue (BB). Under optimized conditions, the degradation rate of LaFeO3/In2S3 photocatalyst was dozens of times that of the pristine LaFeO3 and pristine In2S3. Notably, the degradation rate constant for Rh B, TCH and BB was 0.16709, 0.02684 and 0.0175 min?1 over as-prepared LaFeO3/In2S3 photocatalyst, respectively. The surface photovoltage (SPV), reactive oxidation species scavenger (ROSs) and work function (WF) tests were applied to investigate the photoexcited charge behavior of LaFeO3/In2S3 and the possible mechanism of photocatalytic degradation. The results demonstrate that the band bending is formed at the LaFeO3/In2S3 heterostructured interface because the WF of LaFeO3 is higher that of In2S3, which leads to the transfer of photoexcited electron from conduction band (CB) of LaFeO3 to valence band (VB) of In2S3 and the excellent photocatalytic degradation activity of water pollutants. And the Z-scheme charge transfer process was suggested at the LaFeO3/In2S3 interface based on the energy band structure of LaFeO3 and In2S3 and ROSs results. Therefore, we believe that our rationally conceived LaFeO3/In2S3 heterostructured photocatalyst advances the development of photocatalytic degradation and environmental remediation.
查看更多>>摘要：Cu-doped NiCo2S4/flake graphite nanosheet arrays were prepared by multi-step hydrothermal calcination. Three-dimensional structure provides a wealth of active sites and structure stability to improve the charging/discharging rate. Moreover, 5% Cu-doped NiCo2S4/flake graphite composite fulfills an excellent specific capacitance of 3080 F·g?1 at 1 A·g?1 and remains 2600 F·g?1 at 20 A·g?1 with an outstanding capacitance retention rate of 86% at 20 times current density. The all-solid supercapacitor with 5% Cu-doped NiCo2S4/flake graphite electrode and activated carbon electrode exhibits an excellent energy density of 79.4 Wh·g?1 at a power density of 400 W·kg?1 with an outstanding cycling stability of 94% retention after 10000 cycles，suggesting its great potential for the development of high-performance energy storage devices.
查看更多>>摘要：The microstructure of Cu-Ni-Mn-P alloys prepared with different contents of Ni and Mn was explored by using EBSD、TEM、HADDF STEM and HRTEM. The findings revealed that the hardness of the Cu-Ni-Mn-P alloy was significantly increased by addition Ni or Mn. However, the conductivity was declined to vary degrees. The peak hardness of Cu-0.78Ni-0.32Mn-0.21P (NMP211) and 0.4Ni-0.81Mn-0.19P (NMP121) alloys were 176.8 and 178.1 HV，respectively, which is 9.1 and 10.4 HV higher than that of Cu-0.39Ni-0.29Mn-0.18P (NMP111) alloy. In addition, the softening temperature of NMP121 alloy was 530 °C, which is 25 °C higher than that of NMP111 alloy.TEM observation demonstrated that after aging the precipitates of NMP111, NMP211, and NMP121 alloys were calibrated as NiP phase. The phase relationship between the NiP phase and matrix was as (11?1)NiP // (02?2)Cu. With the addition of Ni, the precipitation phase became fine and dispersed, resulting in the improvement of the hardness of NMP211 alloy. XRD analysis showed that the addition of Mn increased the lattice distortion and hardness of NMP121 alloy and sharply decreased its conductivity. The addition of Mn inhibited coarsening of precipitates in high temperature environment, and increased the softening temperature of NMP121 alloy.
查看更多>>摘要：A thermodynamic model was proposed to assess the feasibility of the synthesis of single-phase multi-principal-component alloy. Based on this model, single-phase TiVZrNbTa equiatomic alloys with body centered cubic (BCC) structure were obtained by arc melting (AM), electron beam melting with pendant drop melt extraction (EBM-PDME) and mechanical alloying (MA). The alloys were characterized by powder X-ray diffraction, scanning and transmission electron microscopy, thermal analysis and mechanical testing. The hydrogenation behavior of the synthesized materials was studied by a volumetric method. It was found that for AM and EBM-PDME alloys a complete BCC-to-FCC structure transformation occurs upon hydrogenation, and hydrogen concentration in the hydrides formed reaches 1.5 H/M (1.6 wt%). MA alloy undergoes partial amorphization with maximum hydrogen absorption capacity of 0.9 wt%.
查看更多>>摘要：Surface engineering of transition metal oxide cathode materials for Li-ion batteries is highly important to achieve high-capacity retention, high-rate capability, and long-life term. In this study, VSe2 nanosheets are prepared and used as a surface sensitizer to enhance the electrochemical properties of LiFePO4 (LFP) cathode material. The LiFePO4 @VSe2 (LFP@VSe2) composite is formed by anchoring 1D-LFP particles with the as-prepared 2D-VSe2 nanosheets by using an in-situ solution phase technique. When the LFP@VSe2 composites are used as cathode materials for Li-ion batteries, the Li surface-controlled storage behavior of the batteries is reasonably enhanced. The performance is attributed to the improvement in the inherent Li-ion conductivity of LFP particles, thereby inhibiting surface diffusion drawbacks and decreasing charge transfer resistance. The exterior VSe2 attached to the LFP serves as a second electrically conducting layer to increase conductivity into the entire electrode. Thus, these conditions enhance the electron transfer kinetics and surface stability of the LFP cathode. LFP@VSe2 composite cathode exhibits an ultrastable specific capacity of 166.5 mAh g?1 after 100 cycles @ 0.1 C and can retain a specific capacity of 146.7 and 46.5 mAh g?1 after 700 and 2000 cycles respectively at a current rate of 0.3 C and 10 C.
查看更多>>摘要：The paper explores the possibilities of the successive ionic layers deposition (SILD) nanotechnology for Pt nanoparticle synthesis. It is shown that the SILD nanotechnology, which is based on successive treatment of appropriate substrates in solutions of a platinum complex compound and a reducing agent, is effective for controlled Pt0 nanoparticles formation on the substrate surface. The Pt nanoparticles synthesized using Na2PtCl6 and NaBH4 precursors are characterized. It is found that the concentration and size of the Pt0 nanoparticles deposited on the titanium foil surface can be controlled by the number of deposition cycles. It is established that the size of the Pt nanoparticles depends on the synthesis conditions and varies from 3.3 nm to 10.0 nm for samples synthesized as a result of 10–40 SILD cycles. A model explaining Pt nanoparticle growth during SILD is suggested. It is shown that the nanoparticles obtained exhibit electrocatalytic properties in the hydrogen evolution reaction during acidic water electrolysis. In a series of samples synthesized using 10–40 SILD cycles, the best electrochemical characteristics are demonstrated by the sample obtained after 20 deposition cycles: its overpotential value is 44 mV and the Tafel slope is 30.4 mV/dec.
查看更多>>摘要：The limited resources of lithium stimulated the research work to develop new polyanionic cathode materials for sodium-ion batteries. The Na2M2+2Fe3+(PO4)3 (M = Mn, Ni and Co) phases were prepared by autocombustion method assisted by glycine. Structural, morphology, thermal, electrical and electrochemical properties have been investigated. Its structures were determined using Xray powder diffraction and Rietveld method refinements. The two compounds Na2M2+2Fe3+(PO4)3 (M = Mn and Co) are alluaudite-type. Both compounds crystallize in monoclinic system with the space group C2/c and similar parameters: a = 12.0337(3) ?, b = 12.6268(3) ?, c = 6.5070(1) ?, β = 114.563(2)° for Na2M2+2Fe3+(PO4)3 (NMFP) and a = 11.7597(3) ?, b = 12.4579(3) ?, c = 6.4607(1) ?, β = 113.968(1)° for Na2Co2Fe(PO4)3 (NCFP). The NaNiFe2(PO4)3 (NNFP) compounds crystallize in orthorhombic system with the space group Imma and unit cell parameters: a = 10.3993(1) ?, b= 13.1966(1) ?, c = 6.4955(1) ?. The composition and morphology of the compounds were checked by energy dispersive spectroscopy coupled with scanning electron microscope. The thermal analysis confirmed the allotropic transition of the three materials from monoclinic to orthorhombic symmetry with the changing of divalent transitions metal ion. The electrical conductivity results of indicated that NNFP has the lowest value of activation energy of value= 0.63 eV owing to the large size of open channels existed in the orthorhombic symmetry. The electrochemical cycling results showed that NMFP cathode delivered the maximum storage capacity of about 94.2 mAh/g which correspond to coloumbic efficiency of about 75.5% after the initial cycling.
查看更多>>摘要：In the present study, (Ba0.65Sr0.35)1?xLaxTi1?xFexO3(x = 0, 0.0025, 0.005, 0.01) ceramics were designed and prepared by the conventional solid-state reaction method. The microstructures and electrical properties of La/Fe co-doped Ba0.65Sr0.35TiO3 ceramics were investigated. Enhanced dielectric tunability and reduced dielectric loss were achieved in this system. The acceptor dopant Fe3+ was used to lower dielectric loss while the donor dopant La3+ was added to improve dielectric tunability. The optimum tunable properties took place at x = 0.0025 with the dielectric tunability = 78.8% and the dielectric loss = 0.0040. The figure of merit (FOM) was improved to 197, about five times that of pure BST. The breakdown strength (BDS) enhanced from 59.9 kV/cm to 111.4 kV/cm by La3+ and Fe3+ dopant, which promoted the stability of BST ceramics under high applied electric field. In conclusion, excellent tunable properties and improved breakdown strength made it possible for the La/Fe co-doped BST ceramics to be promising for tunable microwave applications.
查看更多>>摘要：AA 5052 aluminum alloy tube billets were prepared by HCCM vertical continuous casting to study the effect of homogenization temperature and time on the second phases and mechanical properties. The volume fraction of constituent, length of constituent colonies, number density and volume fraction of dispersoids were examined in different homogenization conditions. Optimized homogenization can be obtained at 560 °C for 20 h, and the elongation of the HCCM continuous casting billet increases from 25.5% (as-cast) to 35.5%, while that of the semicontinuous casting billets only increases from 21.5% (as-cast) to 23.5%. In particular, fine and interlaced Mg2Si and Al6(Fe,Mn) phases are obtained after HCCM continuous casting, which is different from the separated distribution phases after traditional semicontinuous casting and improves the effectiveness of homogenization treatment.
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Elsevier