查看更多>>摘要：Exploring a simple, low-cost preparation method to synthesize excellent catalyst for hydrogen evolution reaction (HER) in alkaline solution is highly meaningful for large-scale electrolysis of water for hydrogen production. Herein, a one-step electrodeposition method with simultaneous electrodeposition and phos-phation was proposed to synthesize the three-dimensional NiCoP/carbon cloth (NiCoP/CC) nanoparticles at room temperature on the conductive carbon cloth (CC). The results showed that the NiCoP nanoparticles covered by nanowires had an amorphous structure. The NiCoP/CC electrode exhibited a good catalytic activity in 1.0 M KOH solution. It required only 74,101,149 mV overpotential for HER in basic solution to obtain current densities of - 10, - 20, - 50 mA cm~(-2), respectively, with a corresponding Tafel slope of 89.5 mV dec~(-1). Furthermore, after 24 h constant voltage test, the current density of NiCoP/CC only showed 2% decay, indicating a good stability. The obtained excellent catalytic activity can be attributed to the amorphous structure, the synergetic effect of Ni and Co, the charge transfer among Ni/Co and P, and nanoparticles in situ grown on carbon cloth. The simple one-step electrodeposition method shows a very promising potential for the preparation of bimetallic phosphides.
查看更多>>摘要：Layered double hydroxide (LDH) has great potential as advanced electrode material for supercapacitor. In this paper, by tuning the reaction temperature, two Ni Co-LDH nanostructures (hollow nanocage and sea urchin) were synthesized through the hydrolysis etching process of ZIF-67 crystals and Ni~(2+) ions. It has been found that the morphology of the electrode material has a great influence on the electrochemical performance and analysis the reason of this behavior is essential for understanding the morphology-related electrochemical performance. Here, a much more capacitive charge storage behavior of hollow Ni Co-LDH than that of sea urchin-shaped product is demonstrated by electrochemical kinetic analysis. The higher capacitive behavior of hollow Ni Co-LDH suggests a rapid surface redox reaction during the electrochemical process, which will lead to excellent electrochemical properties. An asymmetric supercapacitor assembled using hollow NiCo-LDH as the positive electrode displays a high energy density of 88.6 Wh kg~(-1) at 749.9 W kg~(-1), further demonstrating its great application potential. These results provide insights into the reasons for the excellent electrochemical performance of hollow nanostructure.
查看更多>>摘要：A double layer coating (Ca-P/PEO) was designed to form on pure magnesium. The Ca-P coatings were prepared at three pH values of the solution. The morphology, phase composition, microstructure, corrosion resistance, and degradation properties of the samples were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and in vitro assessments. The XRD results indicate that the 5.7Ca-P coating is mainly composed of octacalcium phosphate (OCP). The potentiodynamic polarization test indicates that the corrosion current density of the 5.7Ca-P/PEO coated Mg is 100 times and 3 times lower than that of uncoated Mg before and after immersion in SBF solution for 168 h, respectively. The 5.7Ca-P coating promotes the nucleation of osteoconductive minerals (i.e., bone-like apatite), and the hydro-xyapatite (HA) layer formed on the surface of the 5.7Ca-P coating is dense, thick, and stable after immersion in SBF solution for 30 days. These experimental results have demonstrated that the 5.7Ca-P/PEO coating can introduce a high biocompatibility of the bone-Mg substrate interface and provide long-term stable protection in SBF solution in the initial degradation stage.
查看更多>>摘要：The pigments with high near-infrared (NIR) reflectance hold great promise toward both fundamental types of researches and applications for the realization of comfortable indoor-temperature by mitigating urban heat island effect. However, the facile yet simple method for the NIR reflective pigments with bright color and non-toxic feature remains a huge challenge, limiting their practical application. Herein, we proposed a mild and universal method of solution combustion for constructing the non-toxic and NIR reflective yellow-green pigments of Al-doped Y_3Fe_5O_(12). The Y_3Fe_4AlO_(12) pigment presented a high NIR reflectance of 87.66%, and an outstanding acid/alkali resistance. Moreover, the pigment had an impressive color performance (L* = 78.72, a* = - 4.05, b* = 40.04). Besides, the practical near-infrared reflection performance revealed that the transient surface temperature of the Y_3Fe_4AlO_(12) pigment was 7.6 °C lower than that of the pigment with similar color on the market. This research supplied high NIR reflecting pigments of Y_3Fe_(5-x)AlO_(12) as promising coatings for roofs and exterior walls of buildings, acting as a favorable solution for urban heat island effect.
查看更多>>摘要：In this work, we have studied the preparation and properties of an alumino-phosphate glass with composition 13Na_2O-13K_2O-16BaO-4Al_2O_3-54P_2O_5 (mol%). The first part of the work deals with the study of the processing conditions of the dehydroxylation of the phosphate glass, which was performed by remelting under N_2 flow using graphite crucibles. Glass samples from 5 to 50 g and Nd_2O_3 doped were submitted to dehydroxylation and the influence of temperature, time, mass of glass and viscosity were correlated with the content of water in the glasses through the coefficient of absorption of OH ions. The network structure of the glasses was also determined by means of ~(31)P and ~(27)A1 1D/2D nuclear magnetic resonance and the local environment of Nd~(3+) ions was probed by electron paramagnetic resonance. The optimized conditions of processing were then used to obtain a dehydroxylated glass with a 2.5 wt% Nd_2O_3 whose spectroscopic and laser emission properties were studied. The spectroscopic properties of Nd~(3+) ions which include, Judd-Ofelt calculation, stimulated emission cross-section of the laser transition, lifetime, and quantum efficiency are presented. Site-selective laser spectroscopy and stimulated emission obtained under selective wavelength pumping along the ~4I_(9/2)→~4F_(5/2) absorption band were performed to determine the distribution of crystal field in which the rare earth is located, together with its influence in the pump wavelength dependence of the spontaneous and laser emissions of Nd~(3+) in this glass matrix.
查看更多>>摘要：Interfacial defects and electrical characteristics were analyzed to confirm the formation of dipole due to the densification of the SiO_2 buffer layer and the resulting movement of the flat-band voltage. Through the NAOS, the SiO_2 layer was densified without any change in thickness, and the suboxide density after the NAOS decreased from 2.23 × 10~(14) atoms/cm~2 (PE-CVD) to 1.33 × 10~(14) atoms/cm~2 (PE-CVD+NAOS). In addition, both electrical and interfacial defects decreased after NAOS and PMA. From these results, the SiO_2 buffer layer through the NAOS was densified and the interface defect state density was reduced. The PE-CVD sample with low atomic density had a dipole layer strength of 0.799 V before PMA, but it was 0.457 V in the case of PE-CVD+NAOS with high atomic density due to the densification of the SiO_2 buffer layer. Also, both samples were reduced to 0.488 V and 0.422 V after PMA. Based on this, the leakage current of PE-CVD was measured to be 3.05 × 10~(-5) A/cm~2, and the leakage current of PE-CVD+NAOS was measured that the difference in about four orders of magnitude was 1.64× 10~(-9) A/cm~2. Through the densification of the SiO_2 layer, the interface atomic density increased, and consequently, the dipole layer strength decreased, thereby improving the electrical properties.
查看更多>>摘要：Polycrystalline Mg_(1-x)Zn_xFe_2O_4 (0 ≤ x ≤1) ferrites were prepared with sol-gel method. The obtained samples were characterized by powder X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and Mossbauer spectrometry. The X-ray diffraction analysis combined with the Rietveld refinement confirmed that the samples crystallize in a single-phase cubic spinel structure with (SG: Fd3m) and an average grain size in the range of 29.1-40 nm. Lattice parameter increases with increasing Zn concentration, due to the larger ionic radius of Zn~(2+) ions in regard of Mg~(2+) ions. The Curie temperature T_c decreases linearly with substitution. Saturation magnetization (M_s), magnetic moment of iron (u_Fe)) and magnetic entropy change (-ΔS_M) increase for x≤ 0.5 and decrease for x≥ 0.5, this behavior is attributed to the cationic distribution of the ions on tet-rahedral [A] and octahedral [B] sites, where the structure turns from partially inverse spinel to normal spinel, affecting the remanent magnetization and the coercitive field. Moreover, a new empirical relation is acquired performing linear relation between magnetic moment and the inversion parameter 6. Mossbauer spectra show a transformation from sextuple to an only a doublet which indicates a transformation from ferrimag-netic to paramagnetic phase, this ferrimagnetism degradation is confirmed by the negative values of-ΔS_M and the transition of the magnetocaloric effect from normal to inverse through substitution.
查看更多>>摘要：Copper Nitride (Cu_3N) thin films exhibit promising optoelectronic properties and are favourable for further applications in the field of photodetection, lithium-ion batteries etc. In this work, Cu_3N thin film deposited by reactive High-Power Impulse Magnetron Sputtering (HiPIMS) and used for photodetection application for the first time. The microstructure of Cu_3N nanocrystal shows the uniform crystalline morphology and less defects due to high target species ionization rate. The phase structure analysis results confirmed the presence of nitrogen within Cu_3N thin film that is composed of Cu_3N crystallites with anti-ReO_3 structure. Remarkably, optical properties reveal significant absorbance and enhancement in ultraviolet (UV) and visible (Viz) range, which strongly affect the photodetection properties of fabricated ITO/Cu_3N/ITO device. Excellent photosensitivity of 3792% was attained with a fixed light intensity. Furthermore, the photosensitivity was increased to 7443% with increased light intensity. It was perceived that the enhanced surface properties and perfect formation of ITO/Cu_3N/ITO resulted in beneficial pn junction thus exhibits high performance and ultrafast electron-hole recombination. Also, the HiPIMS technique offers high-quality films with a dense and smooth surface that helped in enhancing photodetection. These outstanding results emanate Cu_3N films could be potential candidate for future optoelectronic devices fabrication that can be applied in smart thin-film gadgets.
查看更多>>摘要：Aqueous zinc-ion supercapacitors are a new type of energy storage device possessing high energy density, high safety, long service life, and abundant raw materials, which have attracted attention toward research. In this paper, NiCo_2O_4 nanosheets rich in oxygen vacancies were used as the cathode material for a novel aqueous zinc-ion supercapacitor. The aqueous zinc-ion supercapacitor device showed excellent electrochemical performance with a high specific capacity of 122.5 mAh/g at a current density of 1 A/g. The specific capacity of discharge at a current density of 10 A/g was found to be 72.6 mAh/g, along with a capacity retention rate of 59.3%. The reduction of NaBH_4 enhanced the content of oxygen vacancies in the materials, which facilitated the enhancement of the conductivity and electrochemical properties of the materials. The high energy density and high multiplier performance of the aqueous zinc-ion supercapacitors showed potential for wide applications in portable electronic products and smart devices.
查看更多>>摘要：For the successful commercialization of Bi_2Te_3-based thermoelectric generator (TEG) devices, not only highly efficient TE materials, but also reliable bonding materials with high thermal stability are essential. In this study, we investigated the application of Cu nanoparticle paste (CNP) bonding for increasing the operating temperature of Bi_2Te_3-based TEG devices. Six-chip TEG devices were fabricated by joining surface-metalized Bi_2Te_3-based TE chips and Cu electrodes by CNP bonding. The optimal bonding was achieved when spark plasma sintering was carried out at 310-320 °C and 15 MPa. The 6-chip Bi_2Te_3-based TEG devices showed a maximum output power of 50-60 mW at the hot-side temperature of 400 °C (AT= 380 °C) and maintained almost the same output power after five thermal cycles. The scanning electron microscopy images of the thermally cycled electrodes further confirmed the robustness of the Cu nanoparticle joints. This work provides an effective method for joining TE chips and Cu electrodes for high-temperature TEG devices.
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Elsevier