查看更多>>摘要：To contribute to the wettability of bismuth vanadate (BiVO4) and indicate and improve the efficiency of 17α-ethinyl estradiol (EE2) removal, an Ag2MoO4/BiVO4 {010} composite photocatalyst was prepared in this study. By exposing the {010} crystal facet of BiVO4, its photocatalytic activity was improved. The surface of the photocatalyst was modified with hexamethyldisilazane (HMDS) to increase the surface water contact angle (WCA) of the material, indicating the relationship between the range of WCA of the photocatalyst surface and the performance of the photocatalytic degradation of EE2. The WCA of the HMDS-modified Ag2MoO4/BiVO4 {010} composite was increased from 14.2° to 47.0°, and the photocatalytic properties were significantly improved in the range of 19.1°? 44.0° for WCA. In addition, when the WCA of the Ag2MoO4/BiVO4 {010} composite reached 34.5°, the EE2 exhibited complete degradation in 40 min under the condition of visible light photocatalysis. This result obtained using the prepared composite was significantly better than those obtained using pure BiVO4 {010} (9.1%), pure Ag2MoO4 (20.9%), and unmodified Ag2MoO4/BiVO4 {010} composite (70.4%). The results showed that an effective way to improve photocatalytic performance is by controlling the WCA of the photocatalyst.
查看更多>>摘要：With excellent performance at room temperature as well as being the most mature n-type thermoelectric material in commercialization, Bi2Te2.7Se0.3 has been attracting increased attention. In this study, its carrier concentration and mobility were optimized by introducing excessive Te. When the excessive content of Te was 0.4, its power factor was the largest, and its thermal conductivity declined slightly. Based on Te excess, carbon nanodots were introduced as the dispersed nanosecond phase. The power factors were improved further due to the energy filter effect. In particular, the lattice thermal conductivity was depressed remarkably due to enhanced phonon scattering. Finally, at 423 K, the maximum ZT value of the sample reached 0.91, which was approximately 42% higher than that of the pure Bi2Te2.7Se0.3. The experimental results demonstrate that carbon nanodots dispersion acting as a nanosecond phase is an effective method to improve the thermoelectric performance of n-type Bi2Te2.7Se0.3-based materials.
查看更多>>摘要：The crystal structure and magnetic properties of Fe doped Bi2Te3 are presented. The samples were studied by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and magnetization measurements. Rietveld refinement results show a decrease in volume due to the decrease in c lattice parameter as iron is introduced. By XPS measurements, the Te 3d, Bi 4f, Bi 5d, Te 4d, and Fe 3d core levels were identified, and the XPS valence band (VB) was measured. The deconvolution process of high resolution XPS spectra in Fe 3d orbital shows that the Fe3+ ion is present in the samples. Theoretical calculations by DFT reveal that the Bi2Te3 compound is a semiconductor with a narrow energy band gap in agreement with experimental results. DOS analysis shows that the main contributions to the valence band are the Te 5p, Bi 6p, and Fe 3d states. XPS VB shows a decrease in the intensity at zero eV due to increased Fe 3d states and good correspondence with DOS calculated for Bi2Te3. Finally, magnetic susceptibility measurements on Bi2Te3 do not show a magnetic behavior; however, for the doped sample with x = 0.2, a weak ferromagnetic behavior (WFM) below 14 K is observed.
查看更多>>摘要：Development of high-loading and high-energy-density lithium-sulfur (Li-S) batteries has aroused increasing research interests recently. However, the performance of a conventional two-dimensional Al foil current collector is limited by its smooth/nonporous surface and poor flexibility, which is unfavorable for the achievement of high sulfur loading and sufficient polysulfide adsorption. Hence, a three-dimensional porous Fe-doped polypyrrole aerogel (FPA) is developed by a simple and scalable strategy combing the solution reaction with the freeze-drying technique, aiming at acting as the current collector of cathode to address these issues in Li-S batteries. This FPA possesses a conductive porous network structure with high elasticity and abundant Fe dopants, which can not only buffer the large volume change of sulfur and ensure fast ion/electron transfer, but also effectively anchor the polysulfides and lower the negative polarization effect during cycling. As a result, the FPA@S cathode delivers a high initial capacity of 1196.7 mAh g?1 at 0.2 C and a retained capacity of 829.5 mAh g?1 after 200 cycles, with stabilized Coulombic efficiency and excellent rate performance. This FPA@S cathode also achieves a high cell-level gravimetric energy density of 199.7 Wh kgcell?1 even under a high sulfur-loading (8.57 mg cm?2) and low electrolyte/sulfur ratio (6 mL g?1), demonstrating its practical potential in future advanced high-energy battery systems.
查看更多>>摘要：PbTe and PbSe are important thermoelectric compounds. Cu is commonly used as an electrode material. To provide fundamental information for the devices using these materials, the interfacial reactions in the Cu/PbTe and Cu/PbSe couples are examined. Similar interfacial reactions are observed in these two couples. No interfacial reactions are found in both kinds of couples reacted at 400 °C and 500 °C. There are very significant interfacial reactions in both kinds of couples reacted at 650 °C. The phase equilibria isothermal sections of Cu-Pb-Te and Cu-Pb-Se at 650 °C are proposed for better understanding the respective interfacial reactions. The reaction zone thickness is 160 μm in the Cu/PbTe couple reacted at 650 °C for 3 min, and its reaction path is Cu/Liquid (I)+Cu2Te/Cu2Te/Liquid (II)/PbTe. The reaction zone thickness is 155 μm in the Cu/PbSe couple reacted at 650 °C for 2 min, and its reaction path is Cu/ Liquid (I)+ (Cu)+Cu2Se/Cu2Se+Liquid (I)/Liquid (I)/PbSe. For both kinds of couples, Cu is the dominating diffusion species.
查看更多>>摘要：In the present work, Na diffused CIGSe thin-film solar cells have been fabricated on the flexible stainless-steel substrate. Compared with the controlled CIGSe sample, Na diffused CIGSe layer showed the growth of the MoSe2 layer at the CIGSe/Mo interface. A 600 nm thick Mo:Na layer behaved as a source for Na diffusion throughout the CIGSe layer. Na diffusion assisted MoSe2 layer grown at CIGSe/Mo junction visualized by HR-TEM analysis. Compared with the CIGSe/Mo layer, a thin ~3–5 nm MoSe2 layer has been observed at the CIGSe/Mo interface up on Na diffusion. Additionally, the Ga grading has been confirmed from the SIMS depth profile analysis. The CIGSe/Mo junction properties are improved in terms of better adhesion at the back junction, altered junction property from Schottky to ohmic contact, and formation of the back surface field due to the presence of the MoSe2 layer and Ga grading. The overall device performance has been improved and the photo-conversion efficiency (PCE) has been increased from 5.75% to 8.73% due to Na diffusion for CIGSe solar cells as compared to CIGSe solar cells without Na diffusion. The impact of Na diffusion-assisted MoSe2 layer formation and Ga grading on junction properties has been evaluated using electrical characteristics.
查看更多>>摘要：Herein, α-NixCo(1?x)(OH)2 has been synthesized through etching ZIF-67. This work demonstrates that reaction temperature affects the morphology and composition of α-NixCo(1?x)(OH)2. Hydroxide nanocluster forms at lower reaction temperature, and hydroxide hollow nanocage can be obtained at or exceeding 100 °C. And the synthesis mechanism of α-NixCo(1?x)(OH)2 is speculated. The obtained hydroxide shows outstanding electrochemical performance. For example, the α-NixCo(1?x)(OH)2 obtained at 120 °C delivers high specific capacitance with 2329.2 and 1795.6 F g?1 at 1 and 20 A g?1, respectively. Furthermore, the versatile and simple synthesis strategy allows the recycling of organic ligand.
查看更多>>摘要：High-strength titanium alloys are necessary and essential in aviation and aerospace fields. Attempt to enhance the strength of the most widely used Ti-6Al-4V alloy is significant. However, it is hard to obtain high strength (>1300 MPa) combining with adequate ductility (elongation>12%) for this alloy. In this study, Ti-6Al-4V alloy with high yield strength (1280 MPa), excellent ultimate tensile strength (1358 MPa) and proper elongation (13.7%) was successfully prepared by an innovative strategy based on electropulsing. The strong electron flow of electropulsing induced rapid temperature rise and yielded instantaneous phase transformation, which limited alloying elements diffusing and parent β size growing, and followed by different phase transformations in Al or V solute enriched regions in one parent β grain during the cooling process. The particular microstructure evolution resulted in efficient α′ lath refinement. Then, the strength can be greatly enhanced by the decomposition of fine α' after subsequent aging. Meanwhile, the V and Al generally kept the initial microstructural partition and resulted in a novel bi-lamellar microstructure, which led to proper ductility. The results and analysis provide a novel method and new idea to improve and control the mechanical properties of Ti-6Al-4V and other titanium alloys.
查看更多>>摘要：The potential of Tm3+/Er3+/Sm3+ tri-doped TeO2-Li2O-ZnO (TLZ) glasses for temperature sensors using color emissions and for generating white light sources was investigated. The samples were successfully synthesized by melting quenching technique in air atmosphere. We have used fixed concentrations of Tm3+ (0.2 mol%) and Er3+ (0.5 mol%) ions, and three Sm3+ concentrations: 0.2, 0.5, and 1.0 mol%. Particularly, we have analyzed the fluorescence intensity ratio (FIR) corresponding to the emissions of these ions as a function of the temperature. As a result, the highest value obtained to the relative thermal sensitivity was 2.47%K?1 for the FIR related to the emissions at 530 nm and 458 nm of the sample doped with 0.5 mol% of Sm3+. In addition, white-light emission was achieved by adjusting the doping concentration of Sm3+ ions. Moreover, we obtained a CIE color coordinates changing from white, (0.308, 0.317) at 299 K, to yellow, (0.416, 0.514) at 455 K. These results showed that these TLZ glasses are promising platforms for optical temperature sensing, for example, such as safety signal in high-temperature environment.
查看更多>>摘要：La2Ce2O7 is known to be a disordered fluorite, i.e., 50% La-doped CeO2, exhibiting oxide ion conduction with contributions from protons in wet atmospheres and minority electrons under reducing conditions. Here, we report the effect of additional doping by partial substitution of La3+ with divalent alkaline earth cations A2+ (A = Ca, Sr, Ba) on the hydration behavior and electrical conductivity of La2Ce2O7. A single-phase cubic fluorite structure was obtained for La2Ce2O7, (La1-xCax)2Ce2O7-δ (x = 0–0.3), (La1-xSrx)2Ce2O7-δ (x = 0–0.2), and (La1-xBax)2Ce2O7-δ (x = 0–0.05). Substitution by A2+ enhanced the degree of hydration, which may be attributed to increased concentration of hydratable oxygen vacancies and coordination of oxide ions by A2+ in addition to La3+, while the basicity of the different A2+ seemed unimportant. The doping increased ionic conductivity slightly, while the n-type electronic conductivity under reducing atmospheres increased considerably. XPS analyses indicated that the concentration and binding energy of Ce 3d electrons decreased with increasing doping level of Ca, implying an enhanced mobility of electrons which may be attributed to an observed decrease in lattice parameter.
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