查看更多>>摘要：Because the previous works on Silver Selenide (AgSe) thin films were insufficient, incomplete, and lacking in-depth, the current study explores deeper into AgSe thin films. The current study is unique in that it examines the effect of annealing temperature on the structural, optical, and thermoelectrical properties of the thermally evaporated AgSe thin film, as well as the effect of temperature on the photovoltaic characteristics of the fabricated Ni/n-AgSe/p-CdTe/Pt solar cell in the range of (298–425 K). The pristine thin film was noncrystalline, while the rest of the annealed samples showed crystalline behavior, according to the results of the X-ray patterns (XRD) and the scanning electron microscope (SEM) examinations. Structural parameters for annealed samples were calculated. On the optical side, the number, and the type of dominant optical transitions were determined. It seemed evident that an allowed direct transition was the dominant one. The optical constants, the optical parameters, the dielectric constants, the energy loss functions, the optical and electrical conductivity were also calculated. On the electrothermal side, the results confirmed that the AgSe thin layer has n-type conductivity, while the CdTe thin layer has a p-type conductivity. The photovoltaic characteristics of the fabricated Ni/n-AgSe/p-CdTe/Pt solar cell were studied in the dark and illuminated conditions and at bias voltages in the range of (?3 to 3 volt). The highest power conversion efficiency (PCE) was for the annealed AgSe layer at 425 K. Based on this, we can confirm that the thin film annealed at 425 K is the best layer in the fabricated solar cells.
查看更多>>摘要：(Co1?xNix)79.3B20.7 (x = 0, 0.25, 0.5, 0.75, 1) alloys were solidified at different undercoolings, aimed at the effect of Co/Ni atomic ratio on the metastable phase formation and stability. Substitution of Co by Ni reduces the possibility for metastable M2B (M = Co or/and Ni) phase to form as primary solid at medium undercoolings. As a result, M2B phase completely disappears from the solidification of the alloys with x = 0.5, 0.75 and 1. All the Co-Ni-B alloys investigated solidify into single metastable M23B6 phase at large undercooling. The stability of metastable M23B6 phase however becomes worse as the Ni content increases, due to which it is decomposed into α-M and M3B phases in the post-solidification cooling process when x ≥ 0.75. A vertical section of the Co-Ni-B phase diagram with a content of 20.7 at% B was drawn, including the liquidus temperatures of M3B, M2B and M23B6 phases and the eutectic temperatures of L → α-M + M3B and L → α-M + M2B.
查看更多>>摘要：VS4 with a high theoretical specific capacity is considered as a potential anode material for sodium-ion batteries. In this work, VS4 nanosheets was firstly synthesized through a simple solvothermal method using N-methyl pyrrolidone (NMP) as the solvent. The unique nanosheets structure is beneficial to the transmission of Na+/electrons and the wetting of electrolyte. Benefiting from the special structure, the prepared VS4 exhibits satisfactory sodium storage performance, especially the cycle stability at a high current density (534 mA h g-1 after 500 cycles at 1 A g-1) and excellent coulomb efficiency (about 100% since the second cycle). Most importantly, this work provides a feasible and simple method for preparing transition metal sulfides nanosheets, which can be used in energy storage devices.
查看更多>>摘要：Sr3-xCaxLa(VO4)3: Sm3+ (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5) and novel Sr2CaLa(VO4)3: ySm3+ (SCLVO: ySm3+, y = 0.01, 0.03, 0.05, 0.07, 0.09) phosphors were synthesized by the citric acid-assisted sol-combustion method. The crystal structure, morphology, concentration-dependent emission spectrum, decay time, and thermal stability of phosphors were studied. These synthesized phosphors have a hexagonal structure with a space group of R-3 m (166). High-purity Sr3-xCaxLa(VO4)3: Sm3+ phosphors were obtained when x < 2.5. The change in particle shape and unit cell parameters of the Sr3-xCaxLa(VO4)3: Sm3+ phosphors led to reduced luminescence performance when the Ca2+ concentration was x > 1. The optimal doping concentration of Sm3+ in the SCLVO host is 3 mol%. Under the excitation of 402 nm near-ultraviolet (NUV) light, all phosphors in this series emit orange–red light at 603 nm, which is attributed to the 4G5/2→6H7/2 transition of Sm3+. The SCLVO: 0.03Sm3+ phosphor exhibits a double exponential decay time of 0.872 ms, excellent thermal stability with an activation energy Ea of 0.232 eV, a chromaticity coordinate of (0.5817, 0.4136), and a high color purity of 98.48%. These experimental results demonstrate the potential application of phosphor SCLVO: 0.03Sm3+ in the red component of white light-emitting diodes (WLEDs).
查看更多>>摘要：It is necessary to boost extremely effective and sustained mixed metal oxide-supported materials that can participate in the energy storage process. Herein, TiNb2O7 nanostructure-embedded S- or N-doped graphene quantum dots (S-GQDs/TN or N-GQDs/TN) with interconnection structures are synthesized through a facile alcothermal procedure using in situ chelating and stabilizing agents composed of acetylacetone (Acac) and amines that have different lengths of carbon chains. The interconnected S/N-doped GQDs make the nanocomposites more electron-rich and have improved conductivity, and pyridinic nitrogen produces electrophilic active sites to facilitate hydrogen absorption on the material. The as-prepared nanocomposites exhibited preferable activity for hydrogen sorption. The outstanding electrochemical performance of GQDs/TN nanocomposites is principally ascribed to the contributory impacts of TiNb2O7 nanoparticles and GQDs, which can not only equip valuable effective sites, uncomplicated availability of electrolyte and spreading of hydrogen but also engage its excellent conductivity and efficient structure. Additionally, the morphology and electrolyte concentration were optimized as important parameters. The hydrogen storage capacities of pristine TN microspheres and nanoparticles are 200 and 979 mA h g?1 and increase with modification by GQDs (discharge capacities for S-GQDs/TN3 and N-GQDs/TN3 measured 1234 and 2433 m Ah g?1). In addition, by increasing the electrolyte concentration, the hydrogen storage capacity was increased.
查看更多>>摘要：The nanostructured p-n heterojunction has been synthesized by solution method. The n-type ZnO nanowires were hydrothermally synthesized on a glass substrate; meanwhile, the p-type CuMnO2 was deposited on n-type ZnO nanowires by the sol-gel method. It is well known that solution synthesis has the advantages of large area, low cost, and high efficiency. The n-ZnO/p-CuMnO2 core-shell nanowires revealed rectification and ultralow-leakage properties. The crystalline structures of the p-CuMnO2 and n-ZnO nanowires were amorphous and single crystal, respectively. The organic gas-sensing ability of the CuMnO2/ZnO NWs is very sensitive and fast (~4 s); in addition, the photo-response to UV (365 nm), blue (445 nm), and green (520 nm) illumination was 6.3 × 105, 4.3 × 103 and 50.5, respectively. The above results prove that p-n heterojunction can improve the gas sensing and photo-response of nanomaterials.
查看更多>>摘要：Mn-Cu alloys with high Mn contents have good damping capacity but poor workability and mechanical properties. In this research, laser powder bed fusion (LPBF) was applied to fabricate the Mn-Cu alloys (Mn63Cu37, Mn73Cu27, and Mn82Cu18) based on mixed element powders. The printability, microstructure and mechanical properties of the as-fabricated Mn-Cu alloys were investigated through a series of characterization methods. The results indicate that the Mn-Cu alloys with high relative densities (99.76–99.85%) can be fabricated using the optimal processing parameters. The as-fabricated Mn-Cu alloys show higher strengths (537.5–589.6 MPa) and yield strengths (404.0–440.1 MPa) than those of commercial Mn-Cu alloys fabricated by conventional methods. The tensile strength presents an overall downward trend with increasing Mn content. Thus, LPBF can be considered as a promising method to fabricate Mn-Cu alloys with high Mn contents.
查看更多>>摘要：Lead-free 0.7BiFe1–2xZnxMnxO3–0.3BaTiO3 (BFZMx–BT) piezoceramics were prepared through the sol–gel method followed by a two-step sintering process. The crystal structure and microstructure were investigated by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy, which revealed that the addition of Zn and Mn ions resulted in a noticeable modification of the microstructure. The BF–BT modification through (Zn, Mn) equivalent codoping induces grain size variation and oxygen vacancies, resulting in an enhancement in the Curie temperature, dielectric properties, polarization magnitude, and strain response. A large remnant polarization (2Pr = 94.6 μC/cm2), low leakage current (7.94 × 10?6 A/cm2), high Curie temperature (473 °C), excellent piezoelectric constant (d33 = 271 pC/N), high unipolar strain (0.353%), and high piezoelectric actuator constant (d33* = 441 pm/V) were obtained for BFZMx–BT ceramics with x = 0.04. These results not only demonstrate the remarkable effect of (Zn, Mn) codoping on the BiFeO3-based piezoceramics, but may also shed light on the development of advanced piezoelectric materials with high performance.
查看更多>>摘要：Antiferroelectric(AFE) and Relaxor ferroelectric(FE) ceramics are most popular for energy storage applications. In our work we have selected compositions near the FE-AFE phase boundary in the quaternary phase PbTiO3(PT)-PbZrO3(PZ)-SrTiO3(ST)-SrZrO3(SZ). Bulk ceramics based on the composition (Pb1?xSrx)(Zr0.80Ti0.20)O3 [PSZT] with 0.14 ≤ x ≤ 0.20 were synthesized by mixed oxide method. XRD and Raman studies were carried out to understand the structural modifications as a function of Sr2+ concentration. Structure refinement using Rietveld method revealed a change from rhombohedral(R3c) for x = 0,to a coexistence of rhombohedral(R3c) and tetragonal(P4mm) for x = 0.15,and tetragonal(P4mm) for x > 0.15. Polarization - Electric field measurements revealed a systematic FE to AFE transition on A-site Sr2+- substitution. Weibull distribution analysis for all PSZT ceramics was carried out to obtain the Breakdown dielectric strength (BDS). Recoverable energy density and energy storage efficiency were evaluated from the P-E hysteresis and have been correlated with their microstructure for their potential energy storage applications.
查看更多>>摘要：Glancing angle deposition technique was used to grow as-deposited SnO2 and also Gallium doped SnO2 (Ga: SnO2) Nanowire (NW) arrays over Si substrate. The relative amount of Ga dopants was varied from 5% to 20% and tested for various structural and optical characteristics. A blue shift in bandgap and enhanced photo absorption was observed for Ga: SnO2 NWs as compared to the as-deposited SnO2 NWs. Photoluminescence study indicates the suppression of emission due to modification in defects after Ga doping with the least emission in case of 5% Ga: SnO2 NWs which was also supported by the X-ray photoelectron spectroscopy results. Photodetectors (PD) were fabricated using all samples and among them the based-on Au/5% Ga: SnO2 NW/Si device exhibited the lowest dark current (~2.67 nA) along with a maximum photoresponse of ~27. Furthermore, a superior transient response with a rise time and fall time of 1.3 ms and 2 ms respectively was observed for 5% Ga: SnO2 NWs PDs. Thus, large e-h pair generation and reduced defect states in case of 5% Ga: SnO2 NWs sample signifies that gallium doping level of 5% in SnO2 is the optimum concentration for enhanced optoelectronic applications.
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Elsevier