查看更多>>摘要：? 2022 Elsevier B.V.The Au nanoparticles (NPs) were formed near the surfaces of pre-synthesized sodium zinc –borate glass by an ion exchange process obtained by thermal heat treatment in an open air environment at various temperatures. The pre-heated Au doped glass samples were extensively tested by the different techniques such as optical absorption spectroscopy, Scanning Electron Microscope (SEM), X-ray photoelectron spectroscopy (XPS), Time of Flight Secondary Ion Mass Spectroscopy (TOF-SIMS), and these Au NPs were used for the antimicrobial applications. SEM confirmed the spherical shaped Au NPs with increasing thermal treatment up to 550 °C. The optical absorption findings showed that the as –synthesized Au NPs showed Localized Surface Plasmon Resonance behaviour, giving clear evidence of an Au NPs band formed in the glass matrix. The formation mechanism of the Au doped glass samples was studied theoretically from a thermodynamic point of view during heat treatment. XPS and TOF-SIMS were used to study the chemical state and the thermal stability of the pre-heated Au NPs doped glasses in an ultra-high vacuum. The effect of concentration changes in the line-shape and in binding energy as a function of thermal heat treatment suggests that the Au NPs formed near the glass surfaces and changes in the chemical composition as well as chemical structures of the Au doped glass samples occurred. Antimicrobial activity such as antibacterial as well as antifungal activity of pre-heated Au doped glass samples was tested against different strains by the disk diffusion method. The Au doped glass samples exhibited enhanced antibacterial as well as antifungal activities by the influence of thermal treatment at different temperatures. Thus, the Au doped glass sample could be efficiently explored as a medical tool in pharmaceutical industries, biotechnology industries and chemical laboratories based upon its antibacterial findings.
查看更多>>摘要：? 2022 Elsevier B.V.Controllable synthesis of hollow structure still remains a huge challenge. g-C3N4 hollow nanocubes with (002) facets exposed (c-CN) are for the first time prepared by calcining cyanuric acid-melamine in the presence of KCl. It is proposed that the c-CN growth is templated by cubic-phase KCl cage at molten state, then Oswald ripening leads to the hollowing of nanocubes. Moreover, silver is loaded on c-CN and its electrochemistry properties are investigated. It is found that at 0.05 mA/cm2, Ag/c-CN electrode shows a higher specific capacitance (10.44 mF/cm2) than that (3.79 mF/cm2) of Ag/p-CN (Ag loading on particle-like g-C3N4). The higher capacitance of Ag/c-CN is mainly attributed to the unique hollow nanocube morphology. On the one hand, c-CN has a larger BET surface area (19.8 m2/g) and a smaller electrical resistance (121.4 Ω), compared to p-CN (4.4 m2/g, 530.8 Ω). On the other hand, theory calculation indicates that the electrolyte cation (e.g., Na+, K+) is easier to desorb from (002) facet than from (100) facet. Hence, the exposed (002) facet of c-CN benefits the cation desorption, improving charging-discharging kinetic processes. Furthermore, after 2500 cycles, ~100% capacitance of Ag/c-CN is retained. It is proposed that the internal and external surfaces of hollow nanocubes can provide more accommodation sites for Ag, favoring the uniform distribution of Ag. Therefore, Ag/c-CN exhibits excellent electrochemical capacitance and cycle stability. Additionally, Ag/c-CN@CF//AC@CF asymmetric supercapacitor (ASC) displays a high energy density of 25 μWh/cm3, a high power density of 17 mW/cm3, and a long cycling lifetime (86.1% capacitance retention after 2500 charge/discharge cycles). The ASC is flexible and can be embedded into other power supply devices.
查看更多>>摘要：? 2022 Elsevier B.V.Band gap engineering by elemental doping has been widely used to adjust the photocatalytic properties of h-BN. In this work, Se-doped h-BN with varied Se doping level are first developed via a heat treatment method. Through a series of experiments and measurements, it is found that the band gap and interlayer spacing of h-BN can be decreased by the incorporation Se. The catalytic property was estimated by the photodegradation of tetracycline hydrochloride under solar light irradiation. Among the modified samples, the optimized 2Se-BN display the highest photocatalytic degradation rate of 78.86% under simulated solar irradiation, which is nearly 1.23 times that of h-BN. It also exhibited reliable recycling photocatalytic activity for the removal of tetracycline hydrochloride. Experimental and theoretical analyses revealed that the introduction of Se can effectively narrow band gap thereby further enhancing light harvesting ability and promote the charge carrier separation of h-BN. This work provides a facile route to synthesize highly efficient Se-doped h-BN photocatalysts for environmental decontamination.
查看更多>>摘要：? 2022 Elsevier B.V.Photocatalytic CO2 reduction into solar fuels has received increasing attention because it is a promising approach to tackle the environment and energy issues we are currently facing. Herein, the composite of K2Ti8O17 nanowires assembly coupled with Cu7S4 cocatalyst has been successfully prepared by an ion exchange method, in which the CuCl is employed as the copper source to convert CdS to Cu7S4. The photocatalytic performance of the integrated K2Ti8O17-Cu7S4 composite is evaluated by CO2 photoreduction, and it exhibits superior photoreduction capability than pristine K2Ti8O17 nanowires assembly. In particular, the K2Ti8O17-Cu7S4-0.2 sample displays the highest CH4 (6.02 μmol g?1 h?1) and CO (0.89 μmol g?1 h?1) yield within 4 h light irradiation, which is 3.83 and 12.71 times higher than that of K2Ti8O17 sample, respectively. Based on the photo/electrochemical test results, the anchoring of Cu7S4 cocatalyst can promote the photogenerated electron-hole pairs separation and charge transfer of the K2Ti8O17, which contributes to more photogenerated electrons participating in the process of photocatalytic CO2 reduction to CH4. This work offers a promising approach to design efficient noble-cocatalyst-free photocatalyst for CO2 photoreduction.
查看更多>>摘要：? 2022 Elsevier B.V.A new small strain multi-directional forging (MDF) with gradient cooling was proposed to tailor the microstructure and improve the mechanical properties of Mg alloys. Using MDF with a cumulative strain of 2.7, a uniform ?ne-grained microstructure with an uncommon bimodal basal texture was achieved. Influenced by the Schmid factor, the twins in the< 10–10 > type grains rotated the basal poles toward the last forging direction (LFD), whereas the twins in the< 11–20 > type grains refined the microstructure. The dominant refinement mechanisms at high temperatures were twinning segmentation (TS) and discontinuous dynamic recrystallization (DDRX). It gradually became continuous dynamic recrystallization (CDRX) as the temperature was lowered. Twinning-induced recrystallization (TDRX) also occurred at 200 ℃. The plastic deformation and DRX mechanism affected the texture evolution of the grains. With a cumulative strain of less than 0.3, {10–12} twinning was dominant and responsible for the formation of the< 0001 > //LFD texture. As the cumulative strain increased to 0.9, multiple slips began to dominate the deformation, and a relatively stable< 10–12 > –< 11–24 > //LFD bimodal basal texture was formed. In contrast, the DRXs had little effect on texture types. The yield strengths were affected by the grain sizes and textures during MDF. The fluctuations of strength in the initial stage were mainly attributed to the texture change. When the texture was stabilized, the increases in strength were owing to grain refinement. The yield strengths can be accurately estimated by an improved Hall-Petch relation that includes the texture effect.
查看更多>>摘要：? 2022 Elsevier B.V.Traditional ways to obtain homogeneous and efficient skutterudite-based thermoelectric materials usually require long processing time. In this study thermoelectric properties of Se and Te co-doped CoSb3 bulk materials fabricated using a combination of self-propagating high-temperature synthesis and pulse-plasma sintering techniques were investigated. The proposed short-term fabrication route enabled synthesis of thermoelectric materials with high chemical homogeneity. Moreover, simultaneous doping with Se and Te beneficially influenced the electrical and thermal transport properties of the materials. As a result, an ultralow lattice thermal conductivity of 0.86 W m?1 K?1 has been attained while simultaneously doping and filling the voids in the skutterudite structure. The ultralow lattice thermal conductivity could be attributed to the unique lattice dynamics, enhanced point-defect, and electron-phonon scattering. Owing to these synergetic effects, a dimensionless figure of merit of 1.1 was obtained at 723 K. The findings show that combination of self-propagating high-temperature synthesis and pulse-plasma sintering techniques allow to fabricate chemically homogeneous and efficient thermoelectric materials as well as offer numerous advantages, such as time, energy efficiency, and potential scalability, to carry out large-scale production.
查看更多>>摘要：? 2022 Elsevier B.V.By virtue of their complete spin polarization at the Fermi level, two-dimensional (2D) magnetic half-metallic materials are emerging as one of the latest wonder building blocks for spintronic applications. Using first-principles calculations, we explored how vacancy defects affect the electronic structure and magnetic properties of CrSI semiconductor monolayer. Our results indicate that the magnetic semiconductor monolayer becomes metallic with the presence of single Cr vacancies, VCr, or paired vacancies made up of Cr and nearby S atoms, VCr-S, while by introducing VS, VI, VCr-I and VS-I vacancies, the monolayer becomes a half-metallic ferromagnet with Curie temperature TC above room temperature. Compared with the pristine case that exhibits an intrinsic in-plane magnetic anisotropy with an easy axis along the [100] direction, the six types of vacancies considered in this study either enhance the in-plane anisotropy or switch it to out-of-plane. Our work implies that vacancy engineering could be a viable approach for achieving both half-metallicity and perpendicular magnetic anisotropy in structurally similar magnetic semiconductor monolayers as well as in relevant designer van der Waals heterostructures for 2D spintronic applications.
查看更多>>摘要：? 2022 Elsevier B.V.Pure copper (Cu) and copper-carbon nanotube (Cu-CNTs) alloys were fabricated using laser powder bed fusion additive manufacturing (LPBF-AM) with a relatively high density. Their location-dependent (i.e., distance from build plate) microstructure and nanomechanical properties at room temperature were investigated. The microstructure of the as-build Cu showed ~40% lower porosity as compared to the AM Cu-CNTs. The amount of porosity was dependent on location for Cu sample with the bottom surface had ~61% lower porosity as compared to the top surface, however the change in porosity was negligible for as-build Cu-CNTs depending on the distance from the build plate. With the addition of 0.5 wt% CNTs, the mechanical properties of the composite were decreased slightly may be due to porosity, weak interfacial bonding of Cu and CNTs, CNT agglomeration, and degraded CNTs. Nanoindentation tests showed that the average modulus value and hardness of the composites were in the range of 40–80 GPa and 0.7–1.1 GPa, respectively depending on the strain rates and distance from the build plate; 18% and 25% decreases were achieved compared with pure copper, respectively. Creep displacement also increased for as-build Cu-CNTs as compared to the pure Cu. Further, for each system, increase in porosity led to increase in strain rate sensitivity and decrease in maximum creep displacement.
查看更多>>摘要：? 2022 Elsevier B.V.Er3+ and Sm3+ ions were co-doped in Sr2SnO4:xEr3+/Sm3+ ceramics to achieve the integration of photo-stimulated luminescence (PSL), thermal-stimulated luminescence (TSL) and photochromism (PC) in one single material. The effect of doped Er3+ content on the microstructure, PC, PSL and TSL of the ceramcis has been investigated. It is found that moderate Er3+ content (x ≤ 0.003) could enhance PC, photoluminescence and TSL performance of the ceramics. The PSL and TSL are greatly depressed when x ≥ 0.005. This variation is caused by the change of kinds of formed defects. In addition, we have proposed a new method for optical information storage using the PSL as the optical signal, in which up-conversion luminescence from Er3+ is the reference signal. This strategy could prevent the occurring of error signal. A simple mechanism on the luminescence modulation, PC, PSL and TSL is proposed basing on the defect chemistry. The application demonstration shows the ceramics’ potential in optical devices due to their multi-functional optical properties.
查看更多>>摘要：? 2022 Elsevier B.V.This work attempted to strengthen the interfacial strength and mechanical properties of alumina whisker and graphene co-reinforced copper matrix composites by Cr matrix micro-alloying. Cr elements are observed to: (i) aggregate to form large particles rather than disperse uniformly in Cu matrix; (ii) disperse at interfaces between Cu matrix and reinforcements. The relative density, tensile strength, shear strength and compressive strength of the Cu-Cr composites were in direct proportional to Cr micro-alloying amount from 0 to 1.5 wt%. Increased Cr micro-alloying amount, on the one hand, can strengthen interfacial bonding between Cu matrix and reinforcements and thereby enhance the load transfer efficiency at interfaces; on the other hand, can yield obvious grain refinement, and thereby achieving grain boundary strengthening as well as twin boundary strengthening, which were considered as the dominant strengthening mechanisms of Cu-Cr composites. Besides, dislocation strengthening and solid-solution strengthening were also additional strengthening mechanisms of Cu-Cr composites.
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