查看更多>>摘要：The structural, magnetic, and electrical dc transport properties of Co-doped hexagonal Mn5Si3 alloys of nominal compositions Mn5?xCoxSi3 (x = 0.1, 0.3, 0.5) have been investigated. The doped alloys were found to crystallize in hexagonal D88 type structure. The shift in the collinear to non-collinear antiferromagnetic transition temperature towards the lower temperature is found to be slow with increasing Co-concentration compare to the Ni-doped alloys. However, both Ni and Co-doping provide positive chemical pressure in the system. Slower change in the valence electron concentration (e∕a ratio) with Co-doping plays the crucial role behind such observation. Incomplete field-induced non-collinear to collinear antiferromagnetic transition in the Co-doped alloys is another critical observation of the present work. A possible explanation for such behavior has been mooted in terms of local minimas’ disappearance between parent and product phases in the free energy landscape. Besides, various vital properties of Mn5Si3 alloy like, inverted hysteresis behavior, magnetocaloric effect, and magnetoresistance are found to be significantly affected by Co-doping.
查看更多>>摘要：This work contains an extensive study on temperature dependent complex dielectric behavior over 4 Hz ≤ f ≤ 8 MHz of a promising hybrid perovskite, propylammonium lead bromide. The structural, as well as morphological property of this sol-gel derived sample have been analyzed with the help of XRD and SEM respectively. The obtained energy band gap and thermal stability study ensure the capability of this material in device fabrication. Possessing a wide band gap, this perovskite fascinatingly serves as a UV photodetector. The individual impact of grain and grain boundary over the entire resistance has been resolved by Maxwell – Wagner Cole–Cole model. This material holds an amazing property; giant dielectric constant near room temperature at low frequency limit which escalates rapidly in the influence of thermal effect. Modified cole – cole plot assures that both space and free charge conductivities ascend with temperature. The asymmetrical nature of the imaginary part of electric modulus is analyzed by Kohlrausch – Williams – Watts which confirms its non – Debye nature diminishes with rising temperature. The thermally triggered AC conductivity follows Jonscher's power law and is emphasized with the jump relaxation model. The bulk conductivity of the sample depends on temperature and is elucidated with variable range hopping of localized charge carriers. Activation energy plays a key role in the ionic conduction mechanism within the sample, described elaborately. The overall substantial studies on its application as UV detector and different dielectric properties of this sample construct the basis of appreciable acceptability of the sample in energy harvesting.
查看更多>>摘要：Oxygen vacancies can regulate the energy band structure of semiconductor photocatalytic materials, and serve as electron traps and active sites to improve the photocatalytic activity of the photocatalyst. Herein, we prepared Bi2MoO6 flower spheres with a double-layer structure by a simple solvothermal method, and achieved the controllable introduction of oxygen vacancies through subsequent air calcination at different temperatures. The double-layer structure of Bi2MoO6 improved the light absorption because of multiple reflections. Compared with the pristine Bi2MoO6, the introduction of oxygen vacancies regulated the energy band structure of Bi2MoO6, improved the separation and transfer rate of electron-hole pairs, and produced more active species such as h+ and 1O2. Among all samples prepared, BMO-350 had the best activity, which could degrade 90.6% of ciprofloxacin (10 mg/L) within 80 min under the irradiation of 6000 K visible LED light. While under ultraviolet, 3000 K, 4500 K, 6000 K visible, red Led light and xenon lamp irradiation, the CIP degradation efficiency reached 94.9%, 73.77%, 85.9%, 89%, 16.24%, and 94.7%, respectively, demonstrated that the appreciable photocatalytic activity under the low energy light source.
查看更多>>摘要：In this study, new non-equiatomic high entropy bulk metallic glass (HEBMG) Zr33Hf8Ti6Cu32Ni10Co5Al6 was developed according to the Cu47Zr47Al6 prototype BMG. Kinetic studies were performed with non-isothermal DSC for the BMG and the HEBMG, and their thermal properties were compared. Calculation of activation energies by different methods indicated that Eg is higher for the HEBMG than the BMG, while Ep is lower for the HEBMG than the BMG, and Ex is similar for both alloys. The values of structural relaxation enthalpy for the BMG and the HEBMG were 4.95 J/g and 8.19 J/g, respectively. Free volume was calculated at room temperature and Tg. By doing so, the direct correlation between fragility, structural relaxation enthalpy, diffusion, and free volume was shown. Using a compression test at room temperature, a 58% improvement in plastic strain was obtained for HEBMG, which confirmed the calculations.
查看更多>>摘要：Thermoelectric materials which exhibit high performance throughout a range of temperature is required for successful scavenging of waste heat to generate electricity. Herein, we tailor the electronic structure of SnTe by co-doping Zn with three elements namely Ag, Ca and Mg. We observe that the dopants play complementary roles and improve the thermoelectric performance throughout the studied temperature range. Zn introduces resonance level and causes hyper-convergence to increase the Seebeck at low temperatures while M (M = Ag, Ca, Mg) enlarges the band gap preventing bipolar transport and also helps in the band convergence improving the performance at higher temperatures. The enhanced thermoelectric properties predicted by theoretical calculations is supported by experimental results. For the same concentration of doping, AgZn co-doped SnTe exhibits higher performance compared to the other two with an impressive ZT of ~1.54 at 840 K and average ZT of ~0.97 between 500 K and 840 K.
查看更多>>摘要：In this research, a thin film of silica modified with HMDS and PDMS was deposited on the glass substrates by a spraying method. The thin film characterization was performed using X-ray diffraction, UV–VIS–NIR spectrophotometer, field emission scanning electron microscopy and infrared fourier transform spectroscopy methods. Self-cleaning, thermal shock, anti-dust and pencil hardness tests were performed on the samples. The results showed that the average transmittance of the glass coated sample in the wavelength range of 400–1000 nm was 96%, which increased as 5.4% in comparison to the uncoated glass. The modified silica thin film has a uniform distribution of the silica nanoparticles with different sizes between 10 and 70 nm on the surface, which has a water contact angle and a slip angle of 96° and 5°, respectively. In the self-cleaning test, it was observed that water droplets slipped on the surface and carried contaminants while for the uncoated sample, this property is not observed. In the simulated anti-dust test, it was observed that for coated glass, less dust particles are deposited on the surface than in the uncoated sample. Also, in thermal shock test, temperature cycles of ?10 and 60 °C were performed at 10 times and it was observed that after eighth cycle, the coated sample lost its hydrophobic properties.
查看更多>>摘要：A layered α/β Ti alloy was developed by cold rolling and subsequent aging heat treatment of a metastable β Ti-12Mo alloy. The microstructure consisted of coarse equiaxed β grains containing a large number of deformation twins. After aging, α phase was found to preferentially precipitate at twin boundaries following a fixed crystallographic orientation relationship with respect to both the twin and the matrix. Finely dispersed α precipitate were also observed in the matrix and inside some thick twins and were inferred to be due to the presence of parallel nano-sized α” martensite inside thick twins and ω phase formed during cold rolling. The deformation behavior of aged sample was finally characterized by a combination of digital image correlation (DIC) and electron backscatter diffraction (EBSD) analyses. An increase in yield strength was noted when compared with the solution treated sample. It was found that plastic deformation was highly heterogeneous and mostly located in the α layer at the interface between the matrix and thick twins. This heterogeneity was finally discussed based on an elastic stiffness analysis and the specific crystallographic configuration at this interface.
查看更多>>摘要：Tourmaline, as an important mineral, has received intensive interest, since it is not only a valuable gemstone, but also is a piezoelectric or pyroelectric material, due to the polar structural configuration. However, its nonlinear optical (NLO) properties were not explored so far, because a transparent crystal with high transmittance is scarce, being essential to optical functional materials. Here, we report a novel ultraviolet (UV) NLO tourmaline crystal with chemical composition NaAl9(BO3)3Si6O21OH for the first time by combining first-principles analysis and experimental measurements. It exhibits a short UV absorption edge, considerable second harmonic generation effect and moderate birefringence, thereby facilitating its phase-matching coherent beam output in the range from visible to UV regions.
查看更多>>摘要：Hydrogen (H2) gas sensing properties of platinum (Pt) - nickel (Ni) alloy thin films deposited on a glass substrate by sputter technique are investigated depending on alloy composition, temperature and H2 concentration. The structural properties of Pt-Ni alloy thin films are characterized by XRD, SEM and EDS techniques. The amount of Ni atom in the alloy thin films is increased from 0% up to 60% and the H2 sensing properties of the alloy thin film sensors are examined in the concentration range of 25–1000 ppm H2. The results revealed that the H2 sensing mechanism of the same thickness pure Pt and Pt-Ni alloy thin films could be explained with surface scattering phenomenon, and the Pt79-Ni21 alloy thin film exhibited the best sensing performance to H2 at all measured temperature ranges. The limit of detection for Pt and Pt-Ni alloy thin films is calculated as lower than 1 ppm, and the response times of the films are decreased with rising H2 concentration and temperature.
查看更多>>摘要：Hybrid materials based on montmorillonite functionalized with LaMnO3 perovskitic structures were obtained for the first time by ultrasonic method with sonotrode immersed in the reaction medium, followed by heat treatment at a temperature of 600 °C. The clay mineral montmorillonite (Mmt), sodium montmorillonite (Mmt-Na+) and functionalized material (Mmt-LMO) were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM/Edx) techniques. The XRD patterns of Mmt-LMO composites show both the presence of the perovskitic phase with orthorhombic structure, and a mixture of aluminosilicates, corresponding to the montmorillonite clay minerals. The (Mmt), (Mmt-Na+) minerals and (Mmt-LMO) hybrid material were used to manufacture modified electrodes whose catalytic properties for the oxygen and hydrogen evolution reactions were investigated in alkaline medium. Based on electrochemical experimental results, some of these electrodes are catalytically active toward the hydrogen evolution reaction and the more performant ones were investigated further and it was found that the electrode modified with the composition containing 6 mg LaMnO3 functionalized montmorillonite and 10 μL Nafion solutions have the best electrocatalytic properties. At the current density of ?10 mA/cm2 the electrode exhibits an over potentialfor hydrogen evolution of ?0.48 V and its Tafel slope was measured to be 70 mV/dec. This study complements the extant scientific knowledge relevant to the water splitting domain.
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Elsevier