查看更多>>摘要：Fe-based bulk metallic glasses (BMGs) are of significant interest because of their superior magnetic and mechanical properties, but the plastic strain deficiency at room temperature restricts their application. In the present study, the effect of Ni content on thermal stability, soft magnetic properties and compressive plastic deformation was investigated in Fe80?xNixP12B4.9Si2.5Cu0.6 (x = 0, 3, 6, 9, 12, 15) BMGs. We discovered that the Ni-bearing BMGs exhibit strong GFA, good soft magnetic and mechanical properties, and high Tc, while the excessive Ni addition causes performance deterioration. The Fe71Ni9P12B4.9Si2.5Cu0.6 bulk glass exhibits high strength of about 3000 MPa and elevated plastic strain of 5.1%, together with high saturation magnetic induction of 1.51 T and low coercivity of 1.8 A/m. The Curie temperature up to 636 K was an intriguing finding. X-ray photoelectron spectroscopy results suggest that the brittle-ductile transition comes from the more s-like bonds between clusters because of the Ni addition. In terms of the inherent elastic nature, we consider that the high Poisson's ratio and the low G/K ratio of Ni lead to a large effective volume of the shear transition zone, which corresponds to the nucleation of shear bands. The significant compressive plastic behavior, large GFA and good soft magnetic properties indicated that the current Fe-based BMGs are promising for structural and magnetic functional applications.
查看更多>>摘要：Tin selenide has been considered as one of the most promising anode materials for lithium-ion battery owing to its high theoretical capacity. In this work, a facile colloidal synthetic method was successfully used to obtain nanocomposites comprising ~7 nm SnSe nanocrystals and carbon nanotubes (SnSe NC/CNT). When applied as anode materials in lithium-ion battery, the SnSe NC/CNT nanocomposites exhibited excellent electrochemical performance with a reversible capacity of 706.5 mAh g?1 after 300 cycles at a constant current density of 200 mA g?1. The SnSe NC/CNT nanocomposites also delivered the high reversible capacity of 532.0 mAh g?1 at a high current density of 1.0 A g?1. The SnSe nanocomposites are advantageous to the ion and electron transport. Interconnected by CNT after annealing at 200 °C, SnSe NC/CNT nanocomposites can accommodate the volume expansion even after 300 cycles. The complex conversion and alloying reaction are studied by X-ray diffraction and X-ray absorption near edge structure.
Lopez-Sanchez J.Munoz-Noval A.Rodriguez de la Fuente O.Carmona N....
11页
查看更多>>摘要：Epsilon iron oxide (ε-Fe2O3) coatings on Si(100) substrates are obtained by an easy one-pot sol-gel recipe assisted by glycerol in an acid medium. Glycerol, given its small dimensions, enables the formation of ε-Fe2O3 nanoparticles with a size of a few nanometers and the highest purity is reached in coatings after a densification treatment at 960 °C. The structural and compositional evolution up to 1200 °C is studied by confocal Raman microscopy and X-ray absorption spectroscopy techniques, correlating the existing magnetic properties. We report a novel characterization method, which allows monitoring the evolution of the precursor micelles as well as the intermediate and final phases formed. Furthermore, the inherent industrial technology transfer of the sol-gel process is also demonstrated with the ε-Fe2O3 polymorph, impelling its application in the coatings form.
查看更多>>摘要：Herein, a series of TiO2/Bi0.5Na0.5TiO3 heterojunctions with different mass ratio are first constructed under ultrasound irradiation, which shows superior sonocatalytic and photoelectrochemical properties. The improved performance is attributed to the internal electric field and close interfacial contact of TiO2 and Bi0.5Na0.5TiO3, which promote the transfer of photoinduced electrons from TiO2 to Bi0.5Na0.5TiO3. The spontaneous polarization of ferroelectrics in the heterostructures can be adjusted by ultrasonic treatment durations, which further influences the internal electric field. The TiO2/Bi0.5Na0.5TiO3 sample with mass ratios of 5:1 and ultrasonic treatment for 15 min presents the highest sonocatalytic degradation of Rhodamine B. Moreover, the sonocatalytic activity also shows a close relevant to the ultrasonic temperature and frequency of degradation process. And, the ?OH radicals are mainly responsible for Rhodamine B sonodegradation. This work provides a novel TiO2/Bi0.5Na0.5TiO3 heterojunctions and promotes the application of ferroelectrics modified materials in sono-/photo-catalysis.
查看更多>>摘要：The design of phosphors simultaneously having excellent quantum efficiency, ultra-narrow emission band and zero thermal quenching is yet a big challenge. Herein, we report a blue-emitting K2SrBa(PO4)2:xEu2+ phosphor with ultra-narrow emission peaked at 425 nm with a full width at half maximum (FWHM) of 37 nm (2088 cm?1), high color purity (0.93), together with superior thermal stability and quantum efficiency. This phosphor displays an external quantum efficiency (EQE) of 75.3%, exceeding those of blue phosphors reported thus far. It also has excellent thermal stability showing near zero thermal quenching up to 300 °C, retaining 102%, 100% and 96% of its initial integrated emission intensity at 75, 200 and 300 °C, respectively. Rietveld refinements and density functional theory (DFT) calculations reveal that the Eu2+ ions preferentially occupy the Sr/Ba sites, rather than the K sites, of the host structure, contributing to the superior photoluminescence properties. The as-developed phosphors can be potentially applied in the phosphor-converted white light emitting diodes (pc-WLEDs) for applications such as high-power lighting and backlight display.
查看更多>>摘要：The pristine NaTi2(PO4)3 negative electrode material has a poor electrical conductivity, which significantly inhibits its application in sodium-ion batteries. Herein, carbon coating and Gd3+ doping are simultaneously applied to promote the electrical conductivity of NaTi2(PO4)3 through a simple sol-gel approach. The conductive carbon coating promotes apparent conductivity, while Gd3+-doping effectively improves intrinsic conductivity. Therefore, the resulting Gd3+-doped NaTi2?xGdx(PO4)3@C (x=1%, 3%, 5%, 7%) composites display superior high-rate capabilities for sodium energy storage. A typical obtained NaTi1.95Gd0.05(PO4)3@C anode presents high capacities of 105.9 and 93.1 mAh g?1 at 5 and 10 C, respectively. Furthermore, this anode shows a high capacity retention ratio of 95.2% at 20 C over 500 cycles. These results suggest that this carbon coating and doping strategy is highly effective and can be adopted to enhance the battery properties of other electrode materials.
查看更多>>摘要：To improve the efficiency of light extraction, the vertical-oriented nanoporous (NP) GaN film as scattering medium as well as light-coupling component was prepared by electrochemical (EC) etching followed by annealing process. The Lu2O3:Eu film as fluorescence medium was deposited on the NP-GaN substrate via pulse laser deposition (PLD) method, which has out-of-plane epitaxial relationship of Lu2O3 (222) || GaN (0002). By changing etching and annealing conditions, the average pore diameter, pore density and pore sidewall roughness of NP-GaN are controlled. The experiment shows that the photoluminescence (PL) intensities and quantum efficiencies of epitaxial films are related to the pore density and sidewall roughness of NP-GaN substrates. Due to the scattering effect of nanopores and light-coupling inside Lu2O3:Eu films on the NP-GaN substrates, the PL intensities were enhanced 13–96% compared with that of the films on as-grown GaN substrates, although the crystal quality of the epitaxial film becomes worse with the increase of porosity of the substrates.
Asha Hind P.Rajendra B.V.Patil P.S.Gummagol N.B....
18页
查看更多>>摘要：Transparent nano-crystalline thin films of Sn1?xLaxO2 (x = 0–0.1) were deposited on glass substrates using the cost-effective chemical spray pyrolysis method. The influence of La3+ concentration on the structural, morphological, linear and third-order nonlinear optical properties of the films were analysed. All the films possessed tetragonal crystalline structure, having a preferred (1 1 0) plane orientation irrespective of the doping content. Till a doping of 3 at%, the crystallite size showed a decreasing tendency. The fibrous morphology exhibited by the pure film got transformed into dense spherical microstructures at lower La doping levels. The films with lower doping content showed above 60% of transmittance in the visible wavelength region. The modification in the energy band gaps of the films were observed due to variations in the La concentration. The presence of various defects identified in the deposits by photoluminescence (PL) spectra analysis in the ultraviolet and visible region. Near white light emission was noticed in the films due to these defects. All the films exhibited third-order optical nonlinearity with an observed switching between reverse saturable absorption (RSA) and saturable absorption (SA). The films exhibited self-focussing and defocussing nature due to variation in the doping level. Sn0.94La0.06O2 film was identified as suitable for optical limiting application due to its least limiting threshold value. Hence, these spray pyrolyzed La doped films can be used in optical and nonlinear optical devices.
查看更多>>摘要：A reliable first-principles account of experimentally observed physical properties of perovskite oxides is crucial for realizing their employment in electronic and optical devices. In this context, SCAN meta-GGA functional of DFT offers good approximation for the exchange-correlation energy; facilitating accurate determination of structural and energetic properties. However, SCAN is unable to reproduce electronic and optical properties of wide bad gap materials. In the present study, we report systematic DFT calculations to show that structural, energetic, electronic and optical properties of hafnium based BaHfO3 and SrHfO3 perovskite oxides can be accurately determined through a combine application of SCAN and Tran-Blaha modified Becke-Johnson (TB-mBJ) meta-GGAs. The structural and energetic properties computed using SCAN functional for both BaHfO3 and SrHfO3 are found to be in good agreement with experimental data; achieving a level of accuracy comparable to computationally expansive hybrid DFT calculations. On the other hand, TB-mBJ calculated band gaps computed using the SCAN optimized lattice parameters provide better agreement with experimental data at a low computational cost. The optical properties, band edge potentials and effective masses of the charge carriers in BaHfO3 and SrHfO3 are also computed to examine the combined application of SCAN and TB-mBJ meta-GGAs in predicting the photocatalytic performance of these wide band gap materials. Our results clearly show that the combination of the two meta-GGAs provide a computationally economical route for evaluating the photocatalytic performance of alkaline-earth metal hafnates.
查看更多>>摘要：For usual grain boundary diffusion, the diffused source infiltrates into the magnet from the surface, and a long diffusion distance leads to non-uniform distribution of elements, which seriously restricts the improvement of properties and reduces the uniformity of coercivity. In this work, based on nanocomposite Nd-Fe-B ribbon, a short-range grain boundary diffusion (SRGBD) process is employed to improve coercivity, obtaining a high coercivity of 24.27 kOe in PrCuAl-diffused nanocomposite powder, increasing by 233.0% comparing to the initial ribbon. By spark plasma sintering (SPS) technique, an isotropic magnet with high coercivity of 24.13 kOe is prepared, and meanwhile, good uniformity of coercivity is also achieved. The disappearance of the α-Fe phase and the formation of intergranular phases contribute to a huge improvement of coercivity. At last, with the help of the intergranular phase, established by SRGBD, anisotropic magnets are successfully prepared through hot deformation, which the optimum magnetic properties with Hci = 18.99 kOe, Jr = 1.08 T, and (BH)max = 215 kJ/m3 can be achieved.
NSTL
Elsevier