查看更多>>摘要：Transition metal sulfides exhibit great potential in the application of sodium ion battery anode materials because of their unique properties and high theoretical capacity. Nevertheless, their inferior rate and cycling performances impede the commercialization process. Pseudocapacitance is a significant sodium ion storage behavior to enhance reaction kinetics, which is beneficial to the improvement of electrochemical performances. Herein, an anode material possessing heterojunction structure has been constructed through decorating SnS_2 nanoparticles on the surface of MoS_2@rGO (SnS_2@MoS_2@rGO), displaying a high reversible capacity of 237 mAh g~(-1) at 3.2 A g~(-1) and 167 mAh g~(-1) at 6.4 A g~(-1) after 140 cycles. The good electrochemical performances of SnS_2@MoS_2@rGO electrode can be ascribed to the enlarged surface areas and fast sodium ion transport channel resulting from the heterojunction structure. In addition, the sodium ion full cell consists of SnS_2@MoS_2@rGO anode and Na_3V_2(PO_4)_3@C cathode can even exhibit ideal specific capacity (33 mAh g~(-1) at 20 C (1 C = 117 mA g~(-1))), showing potential application prospects.
查看更多>>摘要：In the present work, a novel strategy is proposed to control the microstructures of microporous spinel aggregates and improve their strengths. This strategy controls the in-situ decomposition behavior of raw material particles and the Kirkendall effect through preheating magnesite and Al(OH)_3, then milling with balls and water. Thus, the expected microstructures of microporous spinel aggregates can be obtained. Four microporous magnesium aluminate spinel aggregates of stoichiometric ratio were prepared using magnesite, Al(OH)_3, calcined magnesite, and calcined Al(OH)_3. The microstructures and strengths of microporous spinel aggregates were analyzed by XRD, SEM, image analysis method, etc. The microporous spinel aggregates prepared from magnesite and Al(OH)_3 had slightly lower apparent porosity (58.2%) than the one (59.2%) synthesized from Al(OH)_3 and calcined magnesite. In addition, the median pore size significantly reduced from 9.5 to 6.8 um, and the compressive strength dramatically increased from 7.3 to 15.2 MPa. These results verify the reliability of this strategy.
查看更多>>摘要：The microstructure changes and mechanical properties of dual-phase U-2 Nb alloy subjected to shot peening treatment (SPT) were investigated. SPT induced severe plastic deformation in the U-2 Nb alloy surface, and a gradient nanostructure was formed on the surface with the grain size ranging from nanocrystallization structure to coarse grains from the surface to the matrix. The results showed that both the α phase with an orthorhombic crystal structure and the y phase with a body-centered cubic structure in the surface layer of the U-2 Nb alloy were refined to nanocrystals with an average nanocrystallization structure size of 63 nm. Due to the concentration of stress at the α/γ interface and grain size effect, the refinement of the α phase matrix occurred before y phase. Furthermore, dislocation slipping caused by deformation, rather than deformation twinning, played a key role in the grain refinement of U-2 Nb alloy. Microhardness and tensile tests showed that both surface microhardness and tensile strength were improved after SPT.
查看更多>>摘要：We prepared a novel three dimensional (3-D) 3d-4f MOF (named as CeCu-MOF; C_(10)H_(10)CeCu_2N_4O_(12)) which exhibits triclinic symmetry P-1 space group, and applied it to the study of electrode materials in organic system and aqueous solution system respectively. In order to overcome the shortcomings of poor electrical conductivity of MOF, we prepared several plant-charcoal materials with discarded grapefruit peel by different carbonization methods. The best electrochemical performance is selected for detailed study. In this paper, different amounts of plant-charcoal and MOF were used as electrode materials for supercapacitors and lithium-ion batteries, and their electrochemical properties were investigated. The results showed that the addition of plant-charcoal did help to improve the electrochemical performance compared with the single-phase MOF.
查看更多>>摘要：Nonlinear-optical (NLO) metal aluminium phosphate crystal materials with deep-ultraviolet (DUV) transparent ability remain greatly unexplored. Herein, mixed alkali/alkaline-earth metal aluminium phosphate DUV NLO crystal Na_2Ca_(17)Al_2(PO_4)_(14) was successfully synthesized through the high-temperature molten technology. Na_2Ca_(17)Al_2(PO_4)_(14) features a 3D Ca-cluster-constructed framework by the stacking of Ca_6O_(36) and (Ca/Na)_3O_(19) clusters, which is filled by isolated A1(PO_4)_6 clusters and isolated PO_4 tetrahedra. Na_2Ca_(17)Al_2(PO_4)_(14) exhibits a short UV absorption edge below 190 nm, phase-matching behavior with strong NLO effect of 0.9 × KDP, high thermal stability. First-principles calculations indicate that the optical properties of Na_2Ca_(17)Al_2(PO_4)_(14) derive primarily from the Ca-O groups, rather than Al-O and P-O traditional groups. The work may further promote the exploration of new DUV NLO aluminium phosphate crystal materials.
查看更多>>摘要：In this work, a novel CoMn_2O_4@CoMn_2S_4 core-shell nanocluster@nanosheet was successfully grown onto Ni foam via a hydrothermal reaction, which omitted the addition of a binder and conductive additive and the need for a complicated electrode preparation process. CoMn_2S_4 nanosheets as "shells" were found to be uniformly distributed on the surface of CoMn_2O_4 nanoclusters as "cores" to form a typical core-shell structure. These structures possess a high specific surface area and abundant active sites, which not only shorten the transmission path for electrons and ions, but also prevent collapse of the structure, thus improving its cycling stability. The specific capacity of CoMn_2O_4@CoMn_2S_4 is 1542.0 C g~(-1) at a current density of 1 A g~(-1) which is 3.1 times higher than that obtained for CoMn_2O_4. Moreover, CoMn_2O_4@CoMn_2S_4 shows excellent electrochemical cycling performance, and the specific capacity retention rate for CoMn_2O_4@CoMn_2S_4reaches 95.81% after 5000 cycles at a current density of 20 A g~(-1). The specific energy of the CoMn_2O_4@CoMn_2S_4 reaches 44.30 Wh kg~(-1) at a specific power of 774.98 W kg~(-1). Therefore, the CoMn_2O_4@CoMn_2S_4//AC device shows excellent practical application capability.
查看更多>>摘要：The valence electron structures, thermal properties, hardness and magnetic moments of single-phase high entropy alloys with the face-centered cubic structure have been first investigated with the empirical electron theory of solids and molecules. The theoretical bond lengths agree with the experimental ones well. The calculated melting points of CrFeCoNi, CrMnFeCoNi and CrFeCoNiCu alloys are consistent with their differential thermal analysis (DTA) measured ones. The calculated magnetic moments of ferromagnetic FeCoNi and FeCoNiX_(0.25) (X=A1 or Si) alloys agree with the observed ones well. The physical properties of these alloys are strongly associated with their valence electron structures. It is suggested that the melting point, cohesive energy, hardness and magnetic moments of the face-centered cubic high entropy alloys are mainly modulated by bonding factor/, covalent electrons per atom n_c/atom, covalence electron pair n_A and 3d magnetic electron, respectively.
查看更多>>摘要：Fabricating Ti_3C_2T_x Mxene based composite with good control of size, morphology and facet for the high-efficiency photocatalytic application is of great potential and highly challenging. In this work, Ti_3C_2-TiO_2 composite are prepared by a simple two-phase assembling method from the Ti_3C_2 Mxene dispersion modified with tetraethyl hydroxyl ammonium (TEHA) and rhombic-shaped TiO_2 nanoparticles with exposed {101} facets. The Ti_3C_2 Mxene acts as a good support to anchor TiO_2 nanoparticles of 15 nm with good facet control. A significantly enhanced photocatalytic hydrogen evolution activity is acquired by the Ti_3C_2-TiO_2 composites. The highest H_2 production rate of 390.92 μmol h~(-1) is gained by the Ti_3C_2-TiO_2 composites with the Ti_3C_2 weight percentage of 6.7%, which is 2.1 times that of pristine TiO_2. The excellent photocatalytic activity can be attributed to the extended light absorption, the boost charge separation efficiency and exposed {101} facets in the TiO_2 nanoparticles. This work provides a new strategy to prepare high quality MXene Ti_3C_2-TiO_2 hybrids with good photocatalytic properties, which could be widely applied to produce other MXene-based composites with excellent properties.
查看更多>>摘要：Poor tribocorrosion resistance of Ti and its alloys remains as a concern for load-bearing biomedical implants. Despite being an effective method to improve tribocorrosion resistance, titanium matrix composites (TMCs) have yet to be used in this type of applications. In-situ TiB (titanium boride) and TiC (titanium carbide) reinforcement phases have been considered as one of the best options to produce TMCs once these phases present high compatibility and strong interfacial bonding with Ti. Although the effect of these phases on the mechanical properties of Ti has been thoroughly researched in the last years, their effect on corrosion, tribocorrosion and biocompatibility of Ti is yet to be fully understood. In this work, in-situ Ti-TiB-TiC_x composites obtained by reactive hot pressing showed identical corrosion response compared to the unreinforced Ti but displayed improved tribocorrosion behaviour. Under 0.5 N load, composites presented as average a reduction of 51% in wear volume loss and under 10 N the reduction was up to 93%. Early biological tests showed promising results, as composites were biocompatible and induced osteoblasts spreading and possibly proliferation most probably due to composite chemistry and surface hardness.
查看更多>>摘要：Nanoporous silver (NPS) with a three-dimensional (3D) bicontinuous ligament/pore structure can be fabricated in different ways and with different treatments. Thermal treatments before or after dealloying can have a considerable impact on the dealloying process. High-temperature oxidation (HTO) has been researched as a method to tune the process of NPS fabrication. In this work, X-ray diffraction and X-ray photoelectron spectroscopy characterizations were used to identify the phase after HTO and dealloying. Copper oxide was found in the precursor alloy after HTO, which could be the key factor that would influence the mechanism of NPS fabrication. Scanning electron microscopy and transmission electron microscopy were executed to characterize the pathway of forming NPS and research the difference between HTO specimens and the as-cast sample. This demonstrated that, compared to the free corrosion pathway, the diffusion method of Ag atoms was different under HTO pretreatment, which was the predominant factor causing a larger 3D bicontinuous ligament/pore structure. Finally, the microstructure of the final NPS pretreated with HTO for 3 min was much more homogeneous than that of the others, and when the pretreatment time of HTO reached 5 min, the ligament/pore structure almost collapsed.
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Elsevier