查看更多>>摘要：? 2022 Elsevier B.V.The electrochemical efficacy of an electrocatalyst can be improved by an elaborate surface modification. In this study, phosphorus co-doped reduced graphene oxide embedded (rGO) flower like CoS/CoS2 heterostructures have been prepared, via one step hydrothermal process, by taking different mole ratio of phosphorus source for excellent hydrogen evolution reaction (HER) in acid solution. The as-fabricated catalysts are studied by XRD, FT-IR, XPS, SEM, EDS, and HR-TEM analyses. The rGO-CoS/CoS2 @P5 (5 mmol) catalyst exhibits a superior catalytic behavior for HER with a less overpotential (148 mV), low Tafel slope (44 mV dec?1) and enhanced cyclic durability (1000 cycles) in acid condition in comparison with other composition. The synergetic effect of hetero-interface and rapid charge transfer through rGO on the active sites of CoS/CoS2 have improved the HER efficiency. This study demonstrated that the component of rGO and P-incorporation on CoS/CoS2 interface offered an achievable yet easy strategy to synthesize platinum (Pt) free metal-based heterostructured catalyst as the favorable electrode material in sustainable energy applications.
查看更多>>摘要：? 2022 Elsevier B.V.The pollution of heavy metals in aqueous solution has been paid considerable attention in the past several decades. Many researches focused on developing new materials or methods for removing heavy metals. The two-dimensional lamellar structure of molybdenum disulfide (MoS2) has attracted extensive interest and was regarded as a potential material due to it has a large number of active sites. In this paper, a novel one-step hydrothermal method was proposed to prepare the MoS2/Bentonite composite material. The MoS2 composed of many nano petals grew successfully in the pores of bentonite to form flower spheres, and the addition of bentonite can effectively avoid the agglomeration phenomenon of MoS2 prepared by the hydrothermal method. Pseudo-second-order model was applied to describe the adsorption process, revealing the adsorption dominated by chemical adsorption. The dynamic model was in accord with the Langmuir model and the maximum adsorption capacity of Cd2+ was 89.45 mg/g. The excellent performance of MoS2/Bentonite made it have the tremendous application of removing heavy metal ions.
查看更多>>摘要：? 2022 Elsevier B.V.Good thermal stability and low thermal expansion are critical challenges for magnetic microwave absorbers in engineering applications. Herein, we develop a low-cost and large-scale electrical discharge method to design a high-thermostability FeCoNi Kovar alloy microwave absorber to address the low-frequency absorption issue. The spherical fine FeCoNi (FCN) powders are achieved from thermal ablation of bulk alloys by this technique, which possesses a dual-peak size distribution and gives the strongest RL value at ? 40 dB at a frequency of 10.8 GHz with a qualified frequency bandwidth of 5.7 GHz from 8.2 to 13.9 GHz. To exceed Snoek's limit, the ball-milling method is applied to flatten FCN powders. Increasing the ball-milling time from 12 h to 36 h, the microwave attenuation shifts to a lower frequency band. FCN-36 powders achieve a maximum RL value of ? 50.1 dB at 3 GHz. Good conductive loss among the overlapped flaked powders with a papillated surface, well dielectric loss caused by interface and dipolar polarization between the oxide coating layer and metal bases, smaller grain size, and the natural resonance contributes to enhancing the electromagnetic wave energy conversion. The research demonstrates a new inspiration toward the preparation of metallic microwave absorbers on scale large scale and provides novel alloy powders for microwave absorption in the low-frequency range.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, a metal-organic framework (Cu-MOF) and two none-precious metals (Ni and Co) are used for preparation of a highly efficient electrocatalyst for methanol oxidation reaction. Nickel/cobalt hydroxides are coprecipitated on Cu-MOF in alkaline solution. The composite is then calcinated at 350 °C to obtain a carbonaceous framework and flower-like NiCo2O4 deposits (CuO-C/NiCo2O4). The obtained composite is characterized by several methods (XRD, XPS, FT-IR, SEM, TEM, and electrochemical techniques). The presence of metal oxides CuO and NiCo2O4 in the prepared electrocatalyst is confirmed by XRD and XPS methods. CuO-C/NiCo2O4 shows excellent catalytic activity towards MOR in alkaline solution (NaOH, 1 M). The electrocatalytic activity of CuO-C/NiCo2O4 is compared to stepwise composites (CuO-C/NiO, CuO/CoO, NiCo2O4) and commercial Pt/C, which confirms the superiority of the proposed catalyst in terms of current density (208.1 mA cm?2) and amperometric stability (7000 s) in methanol oxidation reaction. The observed benefits are attributed to synergistic effects between the porous conductive carbonaceous material and multi transition-metal oxides (CuO and NiCo2O4).
查看更多>>摘要：? 2022 Elsevier B.V.The present study explores the near atomic scale spatial distributions of substitutional alloying elements (aluminium and vanadium) and interstitial impurities (oxygen and carbon) in the microstructures of Ti-6Al-4V and its boron modified counterpart (Ti-6Al-4V-0.1B) alloys using transmission electron microscopy (TEM) and atom probe tomography (APT) techniques. The latter alloy possesses zero solubility of boron in α-Ti and high oxygen concentration around TiB particles. The results suggest that aluminium and vanadium atoms enrich α and β phases, respectively due to strong elemental partitioning between these phases, to an extent that the atomic scale concentrations of various elements considerably differ from the bulk compositions of the two alloys. Furthermore, oxygen atoms are preferentially distributed within the α phase where other interstitial impurities (carbon) also segregate. Substitutional aluminium atoms share an inverse interrelation with interstitial oxygen atoms while vanadium atoms reside besides the impurity-rich regions for both the alloys. The size differences for these elements (substitutional vs. interstitial) with host titanium atoms and related lattice distortion is (partially) held responsible for the atomic scale elemental distributions and the observed interrelations within the α phase. These arguments are further substantiated from DFT results previously obtained for Ti-6Al-4V alloy.
查看更多>>摘要：? 2022 Elsevier B.V.The potential cerium doped yttrium aluminum garnet (YAG:Ce3+) phosphor particles of different sizes are mixed with ethylene-vinyl acetate (EVA) to make luminescent downshifting films, which are then utilized for packaging monocrystalline silicon solar cells. The luminescence of YAG:Ce particles with the different diameters (3–5 μm, 5–8 μm, 8–10 μm, 10–15 μm, 15–20 μm, and 20–30 μm), the transmission of the down-shifting EVA films with the phosphor particles and performance of the packaged solar cells have been investigated. Experimental results show that the particles with 15–20 μm have the highest luminescent intensity. When the mass ratio of phosphors to EVA is fixed, the films with 20–30 μm have the highest transmission. The most significant increase in solar cell conversion efficiency after packaging is due to the downshifting EVA films with 15–20 μm particles. This research could be useful in the selection of downshifting phosphors for solar cells in the future.
查看更多>>摘要：? 2022 Elsevier B.V.The intense 2.9 μm MIR (mid-infrared) luminescence corresponding to the Dy3+: 6H13/2→6H15/2 transition was achieved for the first time in Dy3+/Yb3+ ions co-doped SrF2 crystals. 2 at% Dy3+: SrF2，2 at% Dy3+/5 at% Yb3+: SrF2, and 5 at% Yb3+: SrF2 crystals were grown by Bridgman method. The influence of Yb3+ on its spectral properties and energy transfer mechanisms has been studied. In comparison to Dy3+ doped SrF2 crystals, Dy3+/Yb3+ co-doped crystals exhibit not only intense 2.9 μm emission but also longer high laser energy level lifetimes, favoring 2.9 μm population inversion and lasing behavior. Furthermore, the ET efficiency from Yb3+ to Dy3+ in Dy3+/Yb3+ co-doped crystals is found to be as high as 95.34%, indicating that the ET from Yb3+ is efficient. The results show that incorporating Yb3+ into Dy3+: SrF2 crystals improves the ability to achieve 2.9 μm lasing action, which could be used as a potential gain media for laser diode-pumped MIR lasers.
查看更多>>摘要：? 2022 Elsevier B.V.Alignment of spin of Mn-Mn atoms in Heusler structure mainly depends upon the distance between them which can be easily manipulated by substituting the main group Z-elements in the Mn2-based full-Heusler alloys. In this article, we report the effect of Sn doping at the Sb site in the Mn2NiSb1?XSnX (0.02≤x≤0.1) full-Heusler alloys. We have performed the X-Ray diffraction (XRD) measurement of each sample to obtain the structural information of the synthesized full-Heusler phase. Rietveld refinement performed on the each XRD data of Mn2NiSb1?XSnX (0.02≤x≤0.1) revealed that all the samples were crystallized in the Hg2CuTi prototype (Space group-Fm3m) structure. Analysis of selected area diffraction (SAED) pattern obtained from transmission electron microscopy (TEM) measurement revealed that a single phase of full-Heusler was obtained for the highest Sn content (x = 0.1) sample. Magnetization variation with applied magnetic field plot exhibited the ferromagnetic ground state of each sample as evidenced from hysteresis loop and saturation was obtained up to 1.0 Tesla field. Zero field cooled (ZFC) and field cooled (FC) measurements were also investigated and splitting between ZFC and FC were found to be increasing with an increase in the Sn content. This increment in ZFC and FC splitting with Sn content was attributed to the coupling between the ferrimagnetic (FIM) nature of Mn2NiSn phase with ferromagnetic (FM) nature of Mn2NiSb phase at the interfaces. Small shifting of hysteresis curve observed in the virgin M-H loop around the origin also indicated the spontaneous exchange biasing due to the FM/FIM interaction. Compensation of magnetization followed by exchange biasing with two magnetic phase (FM/FIM) governed by the controlled doping of Sn in Mn2NiSb have been alluringly elaborated. Direct interaction between different known magnetic phases/sub-lattices are rarely investigated which can be used to make suitable materials for spintronic application such as magneto resistive read heads and sensors.
查看更多>>摘要：? 2022 Elsevier B.V.Increased demands for multifunction, integration and miniaturization of electronic devices lead to the investigation of M-type hexaferrite with more abundant properties. In this paper, Ni-Zr co-doped barium ferrite (BaFe12–2xNixZrxO19, 0 ≤ x ≤ 1 with step of 0.2) with concurrent of considerable saturation magnetization and dielectric properties are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM) and LCR meter. Results reveal that pure M-type hexaferrite phase are obtained with expanded cell parameters by increasing Ni-Zr substitution content. The microstructure shows that Ni-Zr doping has small influence on the average grain size. Magnetic measurements indicate that a maximum saturation magnetization is obtained at x = 0.2 with considerable value of 71.5 emu/g. While the permittivity is substantially enhanced by Ni-Zr co-doping for barium hexaferrite with values reach up to ~103 at 100 kHz and dielectric tangent loss about 0.2. These results imply that Ni-Zr doped barium hexaferrites may have potential application in multifunctional and miniaturized electronic devices.
查看更多>>摘要：? 2022 The Author(s)Over the past decades, there has been significant interest in new cooling technology based on the large electrocaloric effect observed in polymeric and inorganic ferroelectric materials. We report a dramatic impact of annealing on the electrocaloric effect observed by direct measurements in Pb0.88La0.12(Zr0.65Ti0.35)0.97O3 bulk ceramics (12/65/35 PLZT). In addition, the EC response was measured deep in a relaxor part of the PLZT composition phase diagram. After additional one-hour sample annealing at 600 °C, the EC response increased by about six times. Electrocaloric results confirm the existence of the significant electrocaloric response with the EC temperature change (ΔTEC) of 4.5 K at 360 K and 90 kV/cm in an annealed sample. This value exceeds previously obtained maximum ΔTEC values at the same field in perovskite relaxor ferroelectrics such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and 8/65/35 PLZT ceramics. The electrocaloric responsivity ΔT/ΔE = 5.09 × 10?7 Km/V determined at 360 K is among the highest observed in bulk perovskite ferroelectrics at a relatively high electric field of 90 kV/cm.
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