查看更多>>摘要:? 2022 Elsevier B.V.In this study, electron transport mechanisms at a direct current in SiO2(Si)&FexOy(Fe) granular composite films containing Si and Fe nanoinclusions in the temperature range of 95–340 K were determined. The composite films were obtained by co-sputtering of Si and Fe targets in oxygen containing atmosphere (Ar+O2) followed by temperature annealing. It was found out that hopping conductivity with a variable-range hopping was realized at low electric fields. In the temperature range of 115<T<180 K, the electron transport could be reasonably described by the Efros-Shklovsky model taking into account the Coulomb interaction. At higher temperatures (180<T<340 K), the Mott model have been shown to be applicable. Using this model, a number of the characteristics of traps and transport process, namely the density of electron traps near the Fermi level, the activation energy of hopping, and the hopping length were determined. In the range of intermediate and high electric fields, the field enhanced thermal activation of electrons in the conduction band (Poole-Frenkel mechanism) was concluded. At this, the temperature independent current was obtained at the highest values of the electric field. This effect was explained by the influence of the energy position of electron traps taking part in the conductivity as well as the temperature dependence of a dielectric constant.
查看更多>>摘要:? 2022 Elsevier B.V.High entropy alloys (HEAs) have attracted significant interest in recent decades due to their unique microstructures and many favorable properties, including high mechanical strength, good thermal stability and excellent corrosion resistance. In the present study, three Cu-Al based medium entropy alloys (MEAs), namely CuAlAg (CAA), CuAlZn (CAZ) and CuAlV (CAV), are deposited on glass substrates using a high-vacuum sputtering system. The as-sputtered MEA films (MEAFs) are processed by Rapid Thermal Annealing (RTA) for 5 min in order to stabilize their microstructures and are then dewetted using a near infrared (NIR) fiber laser system with various repetition rates, pulse powers and scan speeds to produce nanoparticle structures. Finally, the antibacterial properties of the MEAFs and dewetted films are investigated using three bacterial strains, namely Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. It is shown that the particle size of the dewetted films decreases as the accumulated energy (AE) density increases. The smaller particle size leads to a blue shift of the localized surface plasmon resonance (LSPR) absorption peak wavelength as a result of the greater uniformity of the induced electromagnetic field. In the dewetting process, the Ag and Cu elements of the MEAFs form particles, while the Al atoms are repelled to the bottom or surrounding region of the nanoparticles, and the Zn and V atoms remain on the glass surface. The MEAFs and dewetted films show an antibacterial efficiency of 100% for all three bacterial strains after 24 h. Moreover, the bacterial growth curves indicate that the majority of the bacteria are destroyed within 4–5 h of contact. The antibacterial effect of the MEAFs and dewetted films is attributed to the production of reactive oxygen species (ROS) and the release of metal ions, which collectively destroy the cell membranes and lead to cell shrinkage and death. For all of the MEAFs, the antibacterial performance improves after dewetting as a result of the increased surface contact area provided by the nanoparticles. Overall, the present results confirm the effectiveness of MEAs and dewetted films in realizing thin-film coatings with enhanced antibacterial properties.
查看更多>>摘要:? 2022 Elsevier B.V.Coconut shell-based biomass carbon (CSBC) composites loaded with magnetic FeOx nanoparticles (FeOX/CSBC) were successfully prepared by one-step pyrolysis method using sodium chloride as an additive at 600 °C. The crystal structures, surface morphologies, saturation magnetizations, and microwave absorption properties of FeOX/CSBC composites were investigated. FeOX/CSBC composites showed broadband microwave absorption properties and insensitivity to the amount of coconut shell in a certain dosage range. When the amount of coconut shell was 2.5 g, 2.0 g, 1.5 g and 1.0 g respectively, the obtained composites of CSBC-2.5, CSBC-2.0, CSBC-1.5 and CSBC-1.2 showed that the effective absorption bandwidth (EABW, RL≤?10 dB) covered 6.5 GHz, 6.4 GHz, 6.4 GHz and 6.0 GHz with 30 wt% filler loading, respectively. Moreover, RLmin values of CSBC-2.5, CSBC-2.0, CSBC-1.5 and CSBC-1.2 composite were all lower than ? 20 dB in the thickness range of 2–4 mm. The broadband microwave absorption properties of FeOX/CSBC composites could be attributed to the superb impedance matching, multi-polarization relaxation, magnetic-dielectric synergetic effect, and multiple scattering. The insensitivity to a certain dosage range of coconut shell was beneficial to practical operation of the preparation process, and improved reproducibility of the experimental results of microwave absorption properties. This work provides a good foundation for practical application in the absorbing field because of broadband microwave absorption properties and high reproducibility of experimental results.
查看更多>>摘要:? 2022 Elsevier B.V.This work reports the fabrication of flexible and biodegradable sensors for NO2 detection. The sensors were fabricated by depositing Yb doped Nickel oxides (or hydroxides) on a flexible and biodegradable support of algae-sheets/CNTs. According to the analysis by X-ray diffraction, the Ni(OH)2:Yb and the NiO:Yb employed to make the sensors presented hexagonal and cubic phases, respectively. The Ni(OH)2:Yb and the NiO:Yb were synthesized at 200 and 400 °C, therefore, they are named as NiYe200-OH and NiYe400-O, respectively. In addition, the analysis by scanning electron microscopy revealed that the Ni(OH)2:Yb and the NiO:Yb consisted in porous microparticles with sizes of 25–47 μm and 1–25 μm, respectively. Those microparticles were the sensitive material for the gas detection, since the gas detection was not possible without them. The gas detection tests for NO2 (100 ppm at room temperature) were firstly achieved in the unbent state and the sensors made with NiYe200-OH and NiYe400-O powders presented the lowest response/recovery times of 16/252 s and 19/361 s, respectively. Surprisingly, the values of response/recovery times decreased by 37%/16% and by 26%/32% for the AS-CNT/NiYe200-OH and AS-CNT/NiYe400-O sensors, respectively, after bending them (at a radius of curvature of 0.8 cm). The sensors were able to detect NO2 gas because they had on their surface oxygen vacancy defects, which acted as active sites for the adsorption of NO2 molecules. The presence of such defects was demonstrated by the XPS, absorbance and Raman measurements. Some advantages of the sensors were: 1) their capacity to operate with very low power (200–300 μW) and 2) their ability to be recovered for the next cycle of detection without the use of UV radiation or heating, which is normally used to recover the capacity of the sensor for gas detection. Hence, the results showed this work indicate that our gas sensor could be used for the detection of noxious gases and can be used in portable applications due to their compact size and light-weight. Most importantly, most of their mass (≈92%) is biodegradable, making them eco-friendly.
查看更多>>摘要:? 2022 Elsevier B.V.Transition metal phosphides (TMPs) have recently emerged as an important type of electrode materials for supercapacitors due to their intrinsically outstanding specific capacity and high conductivity. Herein, we report Mn doped Ni12P5 nanowires (Mn-Ni12P5-3) as an advanced cathode material for hybrid supercapacitors, which delivers a high specific capacity of 808 C g?1 at 1 A g?1 (560 C g?1 at 10 A g?1) and good cyclic stability (capacity retention of 87% after 1000 cycles at 10 A g?1). Meanwhile, the First-principle Calculation results reveal that the Mn-doping can form an octahedral supporting structure between Mn atoms and P atoms to enhance the structure stability. The assembled Mn-Ni12P5-3//AC hybrid device demonstrates good capacity retention of 67.3% after 5000 cycles at 2 A g?1. This research brings a new implication to the development of supercapacitors.
查看更多>>摘要:? 2022 Elsevier B.V.In this study, the highly active g-C3N4-based photocatalysts were first constructed by assembling amorphous FeOOH nanoparticles on g-C3N4 nanosheets with nitrogen defects (FeOOH NPs/Nvac-CNNS). Such photocatalysts showed 92.83% and 73.86% degradation and mineralization efficiency of the oxytetracycline hydrochloride (OTC) within 90 min, respectively. Meanwhile, Response Surface Method (RSM) predicted that under optimal conditions (electricity 18.586 A, initial pH 6.371 and dosage 0.6 g/L), OTC degradation efficiency of 94.331% can be achieved. FeOOH NPs/Nvac-CNNS exhibited the excellent reutilization and practical application potential in OTC pollution purification of high and low concentration. The synergistic effect of N vacancies and FeOOH coupling endowed CNNS with advantages, such as the carrier's fast separation, good visible-light adsorption, H2O2 fast decomposition and excellent molecular oxygen activation. Such advantages greatly contribute to OTC efficient removal in water. Based on the liquid chromatograph-mass spectrometer (LC-MS) analysis, the five possible degradation pathways of OTC were provided. Furthermore, through the quantitative structure-activity relationship (QSAR) analysis, biological toxicity prediction results of OTC and its intermediates indicated that the FeOOH NPs/Nvac-CNNS/vis system had great potential to achieve green and harmless treatment of OTC pollution.
查看更多>>摘要:? 2022 Elsevier B.V.For ensuring W employed as the armor of the divertor component in International Thermonuclear Experimental Reactor, a ternary W alloy W-5 wt%V-5 wt%Ta was manufactured by mechanical alloying and spark plasma sintering. (V, Ta)-enriched fine grains and W-enriched grains were observed in W-5 wt%V-5 wt%Ta with a single-phase body centered cubic structure. W-5 wt%V-5 wt%Ta has an ultrafine grain size, and higher relative density, microhardness, and strength than the pure W. The strenghening mechanisms were estimated, and the results indicate that grain refinement, densification, and solid solution play the main, secondary and small strengthening roles, respectively. W-5 wt%V-5 wt%Ta has a good irradiation resistance. This good irradiation resistance has a relationship with the ultrafine grains as well as higher compressive and tensile strength of W-5 wt%V-5 wt%Ta. The damage of irradiation was quantitatively analyzed by the 3D laser scanning confocal microscope. This research work suggests that W-5 wt%V-5 wt%Ta can be applied as a potential plasma-facing material.
查看更多>>摘要:? 2022 Elsevier B.V.In the study, the thermodynamics and kinetics of phosphorus injected into indium melt has been investigated. The partial pressures of the phosphorus gases, P(g), P2(g) and P4(g), in equilibrium with the In-P melt with different concentrations is calculated from 1345 to 1700 K. Based on the thermodynamic analysis, the kinetic process of phosphorus injection synthesis has been studied in details, which involves the relationship among the absorption rate, synthesis efficiency, bubble diameter, rising distance of bubble, bubbling rate, injection rate, environmental pressure and melt concentration. The calculated absorption rate is in good agreement with the experimental data. Based on the kinetic analysis, 20 kg InP polycrystals are synthesized in 3 h by optimizing the synthesis parameters. It is found that local indium and phosphorus separation occurs near the bottom of the ingot during solidification from the P-rich melt. The phosphorus depositions present the radioactivity round rod, columnar polyhedron and fibrous characteristics. The formation mechanism of the separation phenomenon is analyzed. Finally, the methods of obtaining stoichiometric and P-rich polycrystals are put forward.
查看更多>>摘要:? 2022 Elsevier B.V.The AlCoCrFeNi alloy system is one of the commonly studied high-entropy alloys (HEA). The additional elements like Ti affect the properties of HEAs. In order to predict these effects on the microstructure and the properties of HEAs, a suitable phase diagram is needed. The phase diagrams can be plotted by using thermodynamic software and databases. But experimental studies should be done to control whether this phase diagram is suitable or not. The aim of this study is to propose a phase diagram suitable for the AlCoCrFeNiTiX system by using ThermoCalc software and to compare it with the experimental results. In this work, HEAs were produced by a vacuum arc melting (VAM) method followed by a heat treatment (H-T) process. The stoichiometric amount of Ti was varied-(X = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0). Its effects on the microstructure evaluations and phase transformations in HEAs were investigated. The H-T processes were realized at different temperatures and cooling conditions. The thermodynamic investigations were performed to predict the phases present within as-cast (AC) and heat-treated (HT) HEAs by using Thermo-Calc 2021a Software and its TCHEA4 database. The Calculation of Phase Diagram (CALPHAD) studies were also utilized to plot the phase diagrams for the AlCoCrFeNiTiX system under both equilibrium and non-equilibrium cooling conditions. AC and HT HEAs were characterized by various techniques: scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). The phases and the microstructures of AC HEAs were detected as similar to the theoretically obtained alloys under non-equilibrium cooling conditions. While the phases and the microstructures of HT HEAs were detected as similar to the theoretically obtained alloys under equilibrium cooling conditions. As a result, the target alloy composition and production process can be designed depending on the desired properties using the proposed phase diagrams. For example, if the Sigma phase is not desired in the structure, HEAs with Ti1.1 and above contents should be studied.
查看更多>>摘要:? 2022 Elsevier B.V.Hybrid aluminum matrix composites (HAMCs) have gotten lots of interest because of the synergy between the multiple phase. The in-situ AlN-TiC-TiN-Al3Ti/Al inoculation ribbons were prepared by powder metallurgy and melt spinning, and then introduced into the Al-Cu-Mn-Ti matrix alloy, assisted by ultrasonic vibration. SEM and TEM were used to examine the microstructures of the inoculant ribbons and Al-Cu-Mn-Ti alloy following inoculation. The test results show that the mechanical properties of the composites have been considerably improved and the grain size has been refined. The ultimate tensile strength, hardness and elongation after fracture have increased from 196 MPa, 82.1 HV and 13.6% to 220 MPa, 98.9 HV and 17.4%, respectively. This can be chiefly because of the good distribution of nano-particles AlN, TiN and TiC in the aluminum matrix and the good interface matching relationship, which has a good refining effect. In addition, Orowan strengthening, fine-grain strengthening, coefficient of thermal expansion (CTE) mismatch strengthening, and load transfer effect multiple strengthening mechanisms work together to enhance the mechanical properties of the material.