查看更多>>摘要：Development of lithium-sulfur batteries faces various challenges, thus it is crucial to design efficient cathode material. We designed a dual carbon source precursor material, which benefits form merging the characteristics of the huge specific surface area of the MOF material and the excellent conductivity of carbon nanotubes to improve the performance of the lithium-sulfur battery. Furthermore, the added nickel-rich metal phosphide can effectively improve the material's ability to adsorb polysulfides. When the addition amount of carbon nanotubes is optimized, the polarization voltage of the battery is reduced, which is conducive to the reaction kinetics of the battery. Due to the above-mentioned advantageous features, the specific capacity of the battery reaches 1453.5 mAh/g at a cycle rate of 0.1 C. In addition, after 500 cycles at 1 C, the coulombic efficiency of the battery always remains above 96%, and the retention rate of specific capacity is also above 90%.
查看更多>>摘要：This study determines the effect of the addition of graphene on the electrical and ferromagnetic properties of the ZnO thin films that are prepared by the sol-gel method. ZnO is a typically oxygen-deficient metal oxide and exhibits intrinsic n-type conductivity. ZnO thin films to which graphene is added and those to which it is not, which are annealed at 500 °C for 30 min in oxygen, exhibit p-type behavior. There is an increase in the hole concentration of the graphene-doped ZnO thin film because of competition between the densities of donor-like defects such as oxygen vacancies and acceptor-like defects such as oxygen interstitials (Oi) and the defect complex that is related to the substitution of carbon for zinc (CZn) and Oi. There is ferromagnetism in a ZnO thin film at room temperature because of the presence of Oi. The intensity of the ferromagnetic signal is increased because CZn and Oi are formed in a graphene-doped ZnO thin film.
查看更多>>摘要：InyAl1?yN epifilms with alloy compositions (y) ranging from 0.13 to 0.47 were grown on a GaN template using a low-temperature molecular-beam-epitaxy technique. Because of the larger lattice constant of high-indium-content InyAl1?yN epifilm, the compressive stress accumulated during epitaxy. When the compressive stress exceeded the elastic limit of the InyAl1?yN epifilms, a “concave-valley” crack with an equivalent width (~25 nm) was generated to form a prismatic domain. Our calculation and fitting results showed that no cracking occurred when the lattice mismatch was<1% because the stress was within the elastic limit. By contrast, the cracks appeared when the lattice mismatch was>2.4% because the stress exceeded the elastic limit.
查看更多>>摘要：Bulk polycrystalline samples of hexagonal Fe2P-type Al-added Mn1.15Fe0.85P0.55Si0.45 were prepared via a solid-state reaction under controlled heat treatment, and their magnetocaloric properties, including magnetization and entropy change, were investigated. Notably, the Curie temperature, which is directly related to the operating temperature of magnetocaloric materials, could be systematically tuned through Al substitution at Si sites owing to the lattice engineering effect. We found an inverse relationship between the Curie temperature and the ratio of the c-axis lattice constant to a-axis lattice constant, which enables the design of magnetocaloric materials for high-performance magnetic cooling systems.
查看更多>>摘要：(1-x)(K0.5,Na0.5)(Nb0.97Sb0.03)O3-x(Bi0.5Ca0.5)ZrO3 [(1-x)KNNS-xBCZ] lead free piezoelectric ceramics with excellent electrical properties were successfully fabricated through the conventional solid-state reaction method. The relationship between (Bi0.5Ca0.5)ZrO3 content and their phase structure, microstructure, piezoelectric properties, dielectric properties and ferroelectric properties were systematically studied. The results show that the unmodified KNN-based ceramics are orthorhombic phase and tetragonal phase appears after the introduction of BCZ and demonstrate that the O-T polymorphic phase boundary (PPB) was formed in 0.01 ≤ x ≤ 0.04. Benefiting from the construction of the PPB, a large piezoelectric coefficient (d33 ~ 303 pC/N), dielectric constant (εr ~ 7158) and a high Curie temperature (TC ~ 340 °C) were achieved in the ceramics with x = 0.02. The coexistence of O-T phases promotes the motion of domain walls, which is the fundamental reason for the improvement of piezoelectric properties. The ceramics demonstrated remarkable piezoelectric properties and high Curie temperature (TC ~ 340 °C), which are promising candidates for practical application to eliminate the Pb-based piezoelectric ceramics from the market.
查看更多>>摘要：In this work, we prepared N-doped reduced graphene oxide/Co0.85Se (N-rGO/CS) microflowers through a two-step method. Since introducing N-doped rGO, the fabricated N-rGO/CS electrode with a high mass loading (~8.83 mg/cm2) exhibits high areal specific capacity of 0.522 mAh/cm2 (4.24 F/cm2) at 1 mA/cm2, and a long-term cycling stability (85.8% of capacity retention after 6000 charge-discharge cycles). This is mainly because N-doped rGO can increase specific area and electrical conductivity, enhance the electrochemical activity and effectively facilitate the electron/ion transport between the electrode and electrolyte. Besides, the quasi-solid-state hybrid supercapacitors (HSCs) assembled by the N-rGO/CS delivers a high volumetric specific capacity of 5.82 mAh/cm3 at 1 mA/cm2, excellent energy density of 4.65 mWh/cm3 under 10.5 mW/cm3 and eminement cycle stability (87.6% retention over 6000 cycles at 10 mA/cm2).
查看更多>>摘要：Metal oxide semiconductors are among the most promising photoelectrode materials for solar water splitting, mainly due to their robustness in aqueous solutions. In this work, a multi heterojunction with metal oxides is fabricated to enhance the photoelectrochemical (PEC) water splitting through unified surface modification. The two-dimensional MoS2 nanosheets are synthesized through the liquid-phase exfoliation (LPE) process. The characteristics of the MoS2 nanosheets for improving light harvest and charge separation, including thickness, number of layers, and concentration, are all estimated using the proper techniques. The best photocurrent density of the α-Fe2O3/BiVO4/MoS2 at 1.23 V vs. RHE under 100 mW/cm2 (AM 1.5) illumination that was identified around 15 times greater than that of the α-Fe2O3 photoanode. The α-Fe2O3/BiVO4/MoS2 electrode shows the highest donor concentration value (4.36E+26 m3) with the lowest flat band potential (0.15 V) among all the prepared electrodes. Furthermore, the obtained hydrogen and oxygen production in 2 h irradiation for α-Fe2O3/BiVO4/MoS2 is 46.5 and 22.3 μmol cm?2, respectively.
查看更多>>摘要：H3BO3 was added to Ca2V2O7 ceramics to decrease the sintering temperature by the solid-state reaction. The effects of H3BO3 addition on microstructure, sintering mechanism, and microwave dielectric properties of Ca2V2O7 ceramics were investigated. The results indicated that H3BO3, as a sintering aid, accelerated the mass transportation and facilitated the densification during the sintering process. An appropriate amount of H3BO3 doped Ca2V2O7 resulted in the decrease of sintering temperature along with the promotion of microwave dielectric properties. Moreover, the decline of V[sbnd]O bond energy and the formation of CaV2O6 explained the variation of τf for Ca2V2O7. In particular, Ca2V2O7 + 9 wt% H3BO3 ceramics sintered at 725 °C exhibited good microwave dielectric properties of εr = 10.36, Q×f = 37,565 GHz and τf = ?106.56 ppm/°C.
查看更多>>摘要：This work developed novel surface-modified carbon foams (SMCFs) with high heteroatom contents and a certain amount of iron oxide particles via the carbothermal reduction reaction between iron oxide and the cyanate resin-based carbon foam. The effects of carbothermal reduction of iron oxide on microstructures and electrochemical properties of the carbon foams have been studied systematically using TG, XRD, FESEM, BET, and XPS. Results show that the carbothermal reduction greatly influences the microstructures of carbon foams when the temperature is higher than 600 °C. The generated iron oxide particles were embedded into the surface of carbon foams. With the increase of temperature, the surface became porous and rough with a certain graphitic structure. When the temperature arrives at 1000 °C, the as-prepared SMCF-1000 has a highest specific capacitance of 212.42 F g?1 at 1 A g?1, and the specific capacitance maintains 107% of the initial value after 10,000 charge-discharge cycles. In addition, the SMCF-1000 exhibits a maximum compressive strength of 2.52 MPa, which is expected to be a novel three-dimensional self-supporting electrode material.
查看更多>>摘要：A novel core-shell structure of Co/N-doped carbon polyhedron@NiCo layered double hydroxides (Co/NCP@NiCo-LDHs) was designed and synthesized. Except for the advantages of core-shell structure of the electronic redistribution at the heterostructure and exposure of numerous active sites, metallic Co encapsulated into NCP was proved to be crucial to fine-tune the electronic transfer between NCP and NiCo-LDHs. The above merits rendered Co/NCP@NiCo-LDHs with improved oxygen evolution reaction (OER) activity with a low overpotential of 277 mV at 10 mA cm?2 in 1 M KOH solution, which is much better than the Co/NCP, NiCo-LDHs and NCP@NiCo-LDHs, and showed quite high durability. This strategy is demonstrated to be a reliable approach for improving the catalytic efficiency of LDHs catalysts.
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Elsevier