查看更多>>摘要：By the exploitation of doping in semiconductor photocatalysts, the energy band structure adjustment would induce the improvement of solar absorption and photochemical performance. Here, we investigated the N/F codoped TiO_2 nanotube arrays (TiO_2 NTs) by tuning the preparation operation sequence of sol-vothermal doping and annealing treatment. The optimized Sample 1 prepared by the first solvothermal doping in ethanol and then annealing exhibited the outstanding solar absorption, low electron-hole recombination and photoelectrochemical performances. The excellent photocatalytic performances in pho-tocurrent/H_2 generation and pollutant removal were discussed and analyzed in detail. Furthermore, we explained the mechanism of N/F codoping for improved photocatalytic performances. The work gives a referable template for improved photocatalytic application fields of TiO_2 in environment and energy.
查看更多>>摘要：The composition of nanoparticles obtained by a thermal plasma process was quantitatively investigated using a Ni-Cu isomorphous alloy system. Specifically, a Ni-Cu alloy nanopowder with an average particle diameter of ~ 70 nm was prepared by the thermal plasma process and the particle composition was investigated. As the lattice constant follows the Vegard's law, a nanopowder with an average composition equivalent to the predefined composition was successfully obtained. According to the EDS analysis obtained from each particle, the standard deviation of composition distribution was 7.7 at% as a powder. The computational study indicated that each particle has a homogeneous composition because of the nanoparticle formation via nanodroplet and that a composition distribution of 1.05 at% is estimated in the powder. Further, the spatial composition distribution of the alloy powder in the reaction chamber was experimentally studied by trapping the powder at a certain location, and the results indicated that the composition distribution of the powder varied spatially.
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.
Muhammet DemirtasKonstantin V. IvanovGencaga Purcek
21页
查看更多>>摘要：Effects of high current pulsed electron beam irradiation (HCPEBI) on the surface microstructure, mechanical properties, room and high temperature tribological behavior of the Ni_3Al-15vol%TiC composite were investigated. The HCPEBI process refines the TiC particles down to nano scale and distributes them homogeneously throughout the modified layer. It also decreases grain size of the Ni_3Al down to 400 nm. Grain refinement and homogeneous distribution of the TiC nanoparticles by irradiation process increase surface hardness from 538 HV0.025 to about 728 HV0.025. The HCPEBI process increases also the wear resistance of Ni_3Al-15vol%TiC composite at both room temperature and elevated temperature of 600 °C due to the increasing hardness and roughening the surface of the sample. Adhesive wear was found to be the dominant wear mechanism for both as-received and irradiated samples at room temperature beside with the dela-mination. At the elevated temperature of 600 °C, oxidative wear and delamination of the oxide layers occur as the main wear mechanisms in the as-received sample. In the irradiated sample, on the other hand, wear starts with the abrasive wear with micro-cutting of surface hills of irradiated sample, and continues with oxidative and delamination wear mechanisms.
查看更多>>摘要：The struggle with "thermal load" is always an unavoidable challenge for photo-luminescent material. In this work, a novel red phosphor of ZnGa_2O_4: Eu~(3+) with spinel-type structure is prepared by high-temperature solid-phase method. Due to the charge imbalance during the replacement processes of Ga~(3+)→Zn~(2+) and Eu~(3+)→Zn~(2+) in mixed spinel structure, vacancy defects can be introduced into the lattice structure of ZnGa_2O_4: 0.02Eu~(3+). The results of Density Function Theory (DFT) calculation demonstrate that the existence of vacancy defects can construct defect energy levels in the energy band structure of the host crystal, which can assist enhancing the fluorescence emission intensity of the phosphor at high temperature. The strong thermal stability of its own structure combined with the assistance of defect energy levels enables the achievement of zero-thermal quenching in ZnGa_2O_4: 0.02Eu~(3+) under multi-wavelength excitation. Our results open up a new way for the exploration and utilization of zero-thermal quenching phosphors.
查看更多>>摘要：Supercritical hydrothermal synthesis is a promising technology to produce nano-ZrO_2 due to its simple craft, short reaction time and low cost. In this paper, nano-ZrO_2 particles with an average particle size of 5.66-35.43 nm were successfully prepared by supercritical hydrothermal method. Meanwhile, the influences of reaction temperature, pressure, time, precursor concentration and pH value on the particle size distributions and surface topographies of nano-ZrO_2 were investigated under different conditions. Reaction time and precursor concentration were strong influencing factors of particle sizes and distributions. The reaction mechanisms of different crystal forms were controlled by pH value of the precursor. Under acidic conditions, soluble [Zr4(OH)_8(H_2O)_(16)]~(8+) was produced due to the hydrolysis of precursors, and the appearance of abundant monoclinic nucleus was triggered subsequent condensation of [Zr_4(OH)_8(H_2O)_(16)]~(8+). In-situ crystallization dominated the crystallization process and the tetragonal phase was formed by the rearrangement of the precursor structures. The intermediate product Zr(OH)_3NO_3 was detected under high pH conditions.
查看更多>>摘要：LiFePO_4/C (LFP/C)-coated LiNi_(0.8)Co_(0.1)Mn_(0.1)(NCM811) was prepared by a simple ball milling method (400 rpm for 4 h), and the influence of different coating amounts of LFP/C on the electrochemical performance of NCM811 was studied in detail. When the LFP/C coating amount was 1 wt%, the material maintained good electrochemical cycling stability and rate performance. The capacity retention of NCM811 @ 1 LFP/C after 300 cycles was 61.6% at 25 °C, which was significantly better than the corresponding value of 48.63% of NCM811. Simultaneously, the high temperature (55 °C) and high pressure (2.8-4.5 V) cycling stability performance of NCM811 @ 1 LFP/C was also better than for uncoated materials. The EIS results showed that the 1 LFP/C modification effectively reduced R_(SEI) (from 46.37 to 32.13 Ω) and Rct (from 155.9 to 113.5 Ω), which was beneficial for the interface charge transfer of electrons and Li~+ ions, consistent with the CV analysis. The XRD, XPS, and FESEM results indicated that the coating layer suppressed the changes in the NCM811 particle macro-volume and reduced the side reactions, improving the electrochemical performance of Nickel-rich layered materials.
查看更多>>摘要：The application of NiCo_2O_4 as electrode materials for supercapacitors has attracted widespread attention. However, pristine NiCo_2O_4 always suffer from poor electrical conductivity and rate performance that limit their electrochemical performance in supercapacitors. In order to overcome the deficiencies of NiCo_2O_4, in this study, we successfully synthesized KCu_7S_4@NiCo_2O_4 core-shell structure in-situ grown on Ni foam with good electrochemical performance. The morphologies of KCu_7S_4@NiCo_2O_4 composite could be controlled by electrochemical deposition time. According to the electrochemical testing results, an optimal composite was obtained with the deposition time of 10 min, and the corresponding KCu_7S_4@NiCo_2O_4 composite possessed the high specific capacitance of 18.4 F cm~(-2) (2008 F g~(-1)) at a current density of 3 mA cm~(-2) and good cycling stability (80% capacitance retention after 4000 cycles at a current density of 40 mA cm~(-2)). Moreover, the investigation demonstrates the great potential application of KCu_7S_4 @NiCo_2O_4 in supercapacitor. The asymmetric supercapacitor fabricated with KCu_7S_4@NiCo_2O_4 and activated carbon delivers a high energy density of 125.56 Wh kg~(-1) at the power density of 105.5 W kg~(-1).
查看更多>>摘要：The high-entropy effect suggests the possibility of unusual thermal transport properties that may be favorable for thermoelectrics. Novel perovskite-type high-entropy (Ca_(0.25)Sr_(0.25)Ba_(0.25)La_(0.25))TiO_3 (4La) and (Ca_(0.25)Sr_(0.25)Ba_(0.25)Ce_(0.25))TiO_3 (4Ce) ceramics were successfully prepared through a conventional solid-state reaction method. XRD, SEM-EDS, and HRTEM were performed to confirm that the chosen multi-component cations can be introduced into A-site to form a single cubic phase with Pm-3m space group. Introduce high-entropy engineering, constituent elements competing inter into the A-site creating lattice distortion and strain fields, which results in extensive structural defects including dislocations which contributed to the phonons scattering of mid wavelength. Grain boundaries and intrinsic oxygen vacancies respectively scatter phonons of high and low wavelengths. The enhanced effective scattering of phonons through the multi-scale defects gives rise to a low lattice thermal conductivity of 2.5 W-m~(-1)-K~(-1) at 1073 K for the 4La ceramics, much lower than that of SrTiO_3-based perovskite thermoelectric ceramics. The high-entropy 4La ceramics possess the maximum power factor of 420 μW-m~(-1)K~(-2). This work provides a strategy of compositional design for thermoelectric oxides with decreased intrinsic thermal conductivity for thermoelectric applications.
查看更多>>摘要：Substantial attention for dielectric ceramic capacitors toward lead-free has been driven by the enhanced awareness of environmental protection. However, the unsatisfying breakdown strength (E_b) and comparatively low efficiency (η) becomes an obstacle for their widespread application. Here, environment-friendly lead-free relaxor ferroelectric (1-x) (0.67BiFeO_3-0.33Ba_(0.8)Sr_(0.2)TiO_3) -xSr_(0.7)La_(0.2)TiO_3 + 0.1 wt% MnO_2 (BFO-BST-SLT) ceramic is reported as an efficient route to possess excellent E_b and high r\ simultaneously. The doping of SLT can significantly suppress the grain growth, improve the relaxation behavior, and thus increasing the E_b and η of the ceramics. Consequently, the corresponding ceramics with x = 0.3 achieves good discharged energy density of -2.55 J/cm~3 and ultrahigh η of -92%. Notably, it presents outstanding charging/discharging performances with fast charging/discharging time (-0.0266 μs), power density (-28.11 MW/cm~3) along with current density (-468.5 A/cm~2). Together with great temperature stability, frequency stability and cycle stability, this contributes provides a crucial way to prepare lead-free dielectrics for next-generation pulsed power capacitor applications.
NSTL
Elsevier