查看更多>>摘要：Hybrid materials composed of inorganic magnetic cobalt-manganese mixed nanoferrites and PMMA polymeric shell have been fabricated by applying an in-situ polymerization process using pre-prepared inorganic core particles (8-9 nm). The ability of the hybrid heating under action of alternating magnetic field and laser radiation (in a separate and synergy mode) was evaluated and compared with stock nano-particles. It was found that hybrid materials show a high response to both stimulants and the highest temperature was achieved by using both AMF and laser exposure under synergic mode (twice the value for the AMF alone). The specific absorption rate of composite material was around 30 W/g for the optimized field parameters and both laser wavelengths (808 and 1122 nm). The great response of the hybrid material for contactless action of AMF and NIR radiation makes the proposed material very interesting for future biomedical and EMI shielding applications.
查看更多>>摘要：Bismuth (Bi)-doped glasses have the potential to be applied in tunable photonic devices owing to their broadband near-infrared (NIR) luminescence. However, it is still challenging to develop Bi-doped glasses with luminescence performance at desirable emission wavelength since it is hard to stabilize the specific luminescent Bi centers. In this work, a structural model describing the negatively charged local environments is proposed to stabilize the activated Bi centers by adding Ta_2O_5 and/or Al_2O_3 in Bi-doped silicate glasses. The results show that the structural model leads to great enhancement of the NIR emission, the broadening of the emission bandwidth and the blueshift of the emission peak, compared to the samples without Ta_2O_5/Al_2O_3 doping. The change in NIR emission performances could originate from the generation of active Bi~+ centers. The latter arises from oxidation of Bi° induced by the negatively charged local environments around Bi. Moreover, the intensity of the Bi NIR emission is enhanced, and this is attributed both to the suppression of phase separation by adding Ta_2O_5 and to the dispersing effect of alumina.
查看更多>>摘要：Microstructural and electrochemical investigations of tri-doped (Gd, Li and Bi) cerium oxide, with theoretical formula Ce_(0.8(1-x-y))Gd_(0.2(1-x-y))Li_xBi_yO_([1.9(1-x.y)+x/~(2+)3y/2]) (x = 0.02 or 0.03 and y = 0.03 or 0.02 and x + y = 0.05) were carried out by XRD, BET, SEM, Raman, and EIS analyses. According to the dilatometer analysis, the synergistic combination of lithium and bismuth promotes the reduction of sintering temperature down to 800-900 °C. A densification > 95% was achieved for the electrolytes sintered at 900 °C. Raman analysis, in agreement with XRD, demonstrated that the lithium and bismuth induced changes due to the growth of the topological disorder and a higher defectiveness provoked by doping. The high dopant concentration (5 moIl%) is well distributed into the lattice and forms a complex network of defects that traps the oxygen vacancies and hence mobile ions promoting the ionic transport. As compared to a single (CGO) or a bi-doped system (BiCGO and LiCGO) an improvement of total conductivity was achieved at lower sintering temperature, with a maximum value for Ce_(0.76)Gd_(0.19)Li_(0.03)Bi_(0.02)O_(1.85) of 2.6810~(-3)-1.66-10~(-1) S cm~(-1) in temperature range of 400-800 °C.
查看更多>>摘要：The photocatalytic application of CdTe quantum dots (QDs) is restricted by the charge carriers recombination and tendency to aggregate in suspended systems. Novel functionalized CdTe (F-CdTe) QDs and CoNiAl layered double hydroxide (LDH) nanocomposite have been prepared to utilize the unique advantages of CdTe QDs. The nanocomposite is prepared via in situ synthesis of LDH in the presence of as-prepared F-CdTe QDs where the QDs partially intercalated in the interlayer spaces of LDHs. As a result of the effective electronic coupling between F-CdTe QDs and CoNiAl LDH, the light-harvesting ability has been enhanced and the absorption edge expands toward the higher visible light wavelengths. Moreover, the charge carriers recombination in nanocomposite has been considerably suppressed compared to the pristine CoNiAl LDH and F-CdTe QDs. Also, the nanocomposite shows remarkable enhancing in photocatalytic degradation of Acid Red 14 (ARM) and Bisphenol A (BPA) as the sample pollutants. The photogenerated holes and hydroxyl radicals have a determining role in the degradation of ARM. The plausible mechanism is proposed based on the experimental results and theoretical calculations. The prepared nanocomposite represents superior photocatalytic activity after 5 consecutive runs. So, the CdTe QDs can be effectively utilized in photocatalytic applications through the proposed promising approach.
查看更多>>摘要：The chemical disorder in magnetic shape memory alloys it is an important parameter that impacts on its magneto-mechanical and electronic properties. In this work, Ni_2MnGa thin films were deposited on flexible glass substrates by using DC magnetron sputtering technique. The short-range order/disorder was investigated by means of Extended X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) measurements using at Mn K-edge. Polycrystalline samples of Ni_2MnGa with fixed stoichiometry exhibit 121 structure with low residual stress and similar grain sizes. A phenomenological model taking into account three chemical order parameters associated with main chemical anti-site disorders and reliable lattice tetragonal distortions extracted from X-ray diffraction analyses was used to perform systematic computational simulations. The results reveal the persistence of local tetragonal distortions of the crystal structure with L21 structure under when increasing annealing temperatures that are accompanied by a systematic decrease of the anti-site disorder between Ni and Mn atoms and substitutions between Ni and Ga atoms, with the orderly occupation of the atomic sites of Mn and Ga remaining unstable. This work also shows presents a consistent model to perform quantitative analyses of the chemical anti-site disorders through EXAFS measurements in the on Ni_2MnGa polycrystalline thin films that preserve both the stoichiometry and the L2_1 crystalline structure.
查看更多>>摘要：Flexible multiwall carbon nanotubes (MWCNTs)- 10 wt% tin selenide (SnSe)/poly (3,4- ethylene diox-ythiophene): poly (styrene sulfonate) (PEDOT: PSS)/5 vol% dimethyl sulfoxide (DMSO) (MSPPD) composite films were fabricated by vacuum filtration method, and their thermoelectric properties were investigated. When the electrical conductivity (a) and Seebeck coefficient (S) of these composite films with different contents of MWCNTs were measured at different temperatures, σ had an increasing tendency with the increase of MWCNTs content while S would decrease gradually. MWCNTs would improve carrier concentration (n) and mobility (u) of SnSe/PEDOT: PSS film simultaneously because of MWCNTs with high electrical conductivity and carrier mobility. The maximum power factor PF of 59.35 μWm~(-1)K~(-2) had been obtained for MSPPD10 composite film at 393 K. The MSPPD10 composite film exhibited ex-cellent flexibility, σ decreased only to 86% of its initial stage after bending 1000 cycles using a rod with a radius of 4 mm. A flexible thermoelectric (TE) generator consisting of 5 legs MSPPD10 could generate an open-circuit voltage of 3.73 mV and maximum output power of 14.74 nW when the temperature gradient was 39 K. This research shows that MWCNTs have great potential to enhance the thermoelectric performance of flexible SnSe/PEDOT: PSS composite films for wearable devices.
查看更多>>摘要：Toxic organic pollutants have a severe impact on the environment as well as the living organisms around the world. Surface-enhanced Raman spectroscopy (SERS) is considered to be one of the advanced sensing methods for the ultrasensitive detection of organic pollutants. Herein, a novel octahedral Ag_2SO_3 micro-crystal was synthesized using the silver-ammonia complex precipitation method for the detection of herbicide (4-chlorophenol) and synthetic dyes (sunset yellow and methylene blue dye). Ag_2SO_3 microcrystal exhibits superior sensitivity with an enhancement factor (EF) in the order of ~10~8. The large surface area with a rough octahedral morphology of Ag_2SO_3 favors the formation of abundant hotspots. The as-prepared Ag_2SO_3 also possesses excellent recyclability property via light irradiation attributed to the chemical enhancement mechanism. The capability of Ag_2SO_3 for the detection of 4-CP against interference in river water and honey was also investigated. It is assumed from the results that Ag_2SO_3 microcrystal is a promising substrate for reusable SERS applications.
查看更多>>摘要：Broad emission bands in semiconducting oxides due to native defects could readily be an efficient source of white light if they are adjusted properly. In this work, Zn_2GeO_4 nanoparticles of 10 and 16 nm sizes, obtained by a precipitation method, are presented as potential white light emitter. Temperature dependence measurements have been performed to discuss the Zn_2GeO_4 luminescence, which consist of emission bands in the ultraviolet, blue and green regions. The analysis of these results provided some clues about the interplay between defect-related centres and the surface states in nanocrystalline Zn_2GeO_4. Finally, a highly efficient cold-white emission at room temperature has been achieved from this nanomaterial.
查看更多>>摘要：In this study, 15-5 precipitation hardening (PH) martensitic steel powder was successfully deposited on U75V eutectoid pearlitic steel to form structurally graded material (SGM) using directed energy deposition (DED) technology. Microstructure evolution mechanism and mechanical properties of U75V/15-5PH SGM were investigated systematically. Results show that the microstructural transition zone (MTZ) is formed above the fusion line due to the dilution effect of eutectoid pearlitic steel. The phase composition of MTZ consists of martensite, retained austenite, and carbides, which is distinct from that of directed energy deposited 15-5PH steel. MTZ possesses the highest microhardness owing to the solid solution strengthening and second phases strengthening of carbon elements provided by eutectoid pearlitic substrate. Special intrinsic thermal cycles of DED lead to the formation of heat affected zone (HAZ) below the fusion line, in which the spheroidization phenomenon of lamellar cementite occurs. The spheroidization degree of lamellar cementite in HAZ is exacerbated with increasing distance from the fusion line. Compared with wrought U75V substrate, the lower tensile strength of SGM is mainly attributed to the weak phase boundaries strengthening of granular pearlite at the bottom of HAZ.
查看更多>>摘要：In this study, α-Fe_2O_3/rGO was smoothly synthesized by a one-step method and employed to activate persulfate (PS) for the degradation of Bisphenol A (BPA) under sunlight. During the degradation experiment, the degradation rates of BPA for PS, α-Fe_2O_3/8% rGO, and α-Fe_2O_3/8% rGO/PS were 6.6%, 47.6%, and 99.1%, respectively, indicating that the introduction of α-Fe_2O_3/rGO and PS significantly enhanced the photo-catalytic efficiency because that photocatalytic process and PS activation coupling system not only inhibited the recombination of photo-induced carrier pairs, but also reduced the energy consumption of PS activation. Moreover, electron spin resonance spectroscopy (ESR) and trapping experiments were utilized to explore the active species generated during the reaction. The results showed that OH and-So_4~(2-) were the principal oxidative species in this reaction system. These results showed that Fe-loaded rGO has great potential for activating PS to decompose pollutants in water.
NSTL
Elsevier