查看更多>>摘要：Researchers have been fascinated to the field of photocatalysis by the creation of innovative composite photocatalysts to enhance the performance of the catalyst. The novel magnetically recoverable La(OH)3/α-MnO2/MnFe2O4 nanocomposite have been successfully prepared via a simple wet impregnation process. The as-synthesized photocatalysts were characterized by multiple analytical techniques. The photocatalytic performance of the as-prepared materials was examined based on Rhodamine B (Rh B) dye under UV–visible light illumination. The obtained Z-scheme magnetically recoverable La(OH)3/α-MnO2/MnFe2O4 nanocomposite exhibited remarkably photocatalytic activity (94.69%), 4.04 and 2.33 times higher than the La(OH)3 and α-MnO2/MnFe2O4 nanocomposite, respectively. The ferromagnetic behavior of MnFe2O4 nanoparticles (NPs) and the high light absorption capacity of α-MnO2 nanorods improve the photocatalytic performance of La(OH)3/α-MnO2/MnFe2O4 nanocomposite. La(OH)3/α-MnO2/MnFe2O4 nanocomposite was able to help ease the recovery by its ferromagnetic behavior. This enriched photocatalytic performance could be caused by the formation of Z-scheme junctions between La(OH)3 and α-MnO2/MnFe2O4 nanocomposite, which helps effectual charge separation and keeps a high redox potential. Magnetically recoverable La(OH)3/α-MnO2/MnFe2O4 nanocomposite offers potential for photocatalysis and has probable applications in the energy and environmental sectors.
查看更多>>摘要：The Snoek limit hinders strong and wideband electromagnetic wave (EMW) absorption, and to meet this challenge, it is essential to obtain an economical and scalable microstructural solution. In this work, we used a SiO2-B2O3-RO-Fe2O3 multicomponent glass system to design microstructures using dendritic Fe3O4 crystal precipitates in the amorphous glass matrix. The flower-like Fe3O4 structures that formed in situ at the grain interface exhibited a significant strengthening effect on EMW absorption performance. The minimum reflection loss (RL) value reached ? 61.0 dB at 7.2 GHz when the sample thickness was 3.3 mm, and the effective absorption bandwidth (EAB) was 6.0 GHz (8.6–14.6 GHz), with a sample thickness of 2.4 mm. This approach not only provided a novel strategy for constructing synergistic multiple transmission-absorption mechanisms, but also provided an option for developing inexpensive high-performance EMW-absorbing materials.
查看更多>>摘要：Because carbon based supercapacitor electrode has low energy density, so birnessite electrode material has attracted more and more attention due to its low cost, environmental friendliness, high oxygen evolution potential and high theoretical specific capacitance. In this work, novel nanoneedle-like rGO/V-NaxMnO2/CC cathode material with oxygen vacancies has been prepared, where rGO and CC represent reduced graphene oxide and carbon cloth, respectively. By using surface-protection strategy and introduction of abundant oxygen vacancies, high capacitance of rGO/V-NaxMnO2/CC is obtained with 362.5 F g?1 at 1 A g?1. After the current density increases to 24 A g?1, the capacitance retention is 56.56%, presenting excellent rate performance. In addition, after 10,000 charge/discharge cycles at 5 A g?1, the capacitance retention rate is 90.17%, showing excellent cycle stability. The aqueous asymmetric supercapacitor (ASC) of ACMK-3 // rGO/V-NaxMnO2/CC has a wide potential window of 0 ~ 2.5 V. And the energy density is as high as 72.2 Wh kg?1 at 1254 W kg?1. After 10,000 charge-discharge cycles at 4 A g?1, the ASC still remains a capacitance retention rate of 88.5%. This work provides a facial method to improve electrochemical properties and shed a light on fabricating a novel cathode for aqueous supercapacitors.
查看更多>>摘要：The microstructural evolution, crystallographic texture and mechanical behaviour of an Al-Mg-Sc-Zr (AA5024) alloy subjected to severe plastic deformation through high pressure torsion (HPT) were investigated. Post HPT at ambient condition, the alloy showed coarse elongated grain structure, both in as-received and heat-treated conditions (grain size, d ~1–2 μm) near top region, while fine equiaxed ultrafine grains (d ~130–380 nm) were observed from edge to centre of the disc. Processing the alloy by HPT at elevated temperatures (473 K and 623 K) resulted in texture weakening and a more homogeneous microstructure (d ~300–800 nm); the lower the processing temperature, the finer is the grain size. The samples processed at lower temperatures exhibited higher hardness (~2.0 GPa) and significant mechanical strengthening (~800 MPa) at the expense of ductility. The mechanical response of the alloy processed by HPT at a higher temperature of 623 K was similar to that of the as-received alloy. The ductility was also restored at reduced strength. Additionally, the as-received and heat-treated alloy specimens displayed noticeable differences of in-plane tensile anisotropy and orientation-dependent mode of dynamic strain ageing with respect to the initial rolling direction. Thus, this study clearly elucidates that the ultrahigh strengths can be achieved in AA5024 alloy by grain refinement through HPT with negligible influence of prior processing history and reduced local heterogeneity in microstructure by HPT at elevated temperatures.
查看更多>>摘要：In high entropy alloys (HEAs), the nanoscale precipitations and short-range orders affected the material's mechanical properties and brought about changes in the thermal physical properties. As-cast Al0.3CoCrFeNi was prepared, and an ideal random disorder HEA model was established by molecular dynamics (MD). The resistivity, thermal conductivity, specific heat capacity and linear expansion coefficient at 300–1100 K were obtained and discussed by experiments and simulations. The intracrystalline segregation was observed in the as-cast HEA. At about 600–800 K, the resistivity growth stagnated, and two exothermic and one downward heat capacity peaks were found in DSC and specific heat, respectively. The metastable structure of as-cast HEA was ordered and a small amount of nano-phase precipitated. When above 800 K, the resistivity increased rapidly, DSC and specific heat appeared endothermic peak and extensive range upward heat capacity peak respectively. The alloy underwent an order-disorder transition accompanied by a small amount of phase decomposition. Phonons were the main force of heat conduction. Thermal conductivity and lattice thermal conductivity show the weak temperature dependence of T?0.66 and T?0.48, respectively. The experimental results, affected by intragranular segregation and ordering, differed from the simulation results at lower temperatures while agreed well with the simulation results at higher temperatures. The order degree on thermodynamic parameters of as-cast HEA during the heating process should be considered in subsequent studies.
查看更多>>摘要：Rare-earth ion Eu3+ was doped into SrTiO3 ceramic to improve its dielectric energy storage properties and act as luminescence centres. Typically, SrTiO3 ceramics doped with 0.2% Eu3+ exhibit high breakdown strength up to 354 kV/cm and a relatively high recoverable energy density of 2.13 J/cm3. Compared to those of the undoped sample, the doped ceramic breakdown strength and recoverable energy density are enhanced by about 22% and 58%, respectively. The doping effect can be explained by the inhibition of the long-range movement of carriers. Moreover, the europium doped SrTiO3 ceramic capacitor exhibits an excellent power density of 37 MW/cm3 in an ultrafast discharge time of 25 nanoseconds at 200 kV/cm. Meanwhile, the Eu3+ doped sample exhibits characteristic red photoluminescence. The bifunctional ceramics offer an excellent prospect for energy storage and optical applications.
查看更多>>摘要：Tuning the morphology and structure at micro/nanoscale has become essential for the advancement of electrode materials for supercapacitors. Here, Ni-Co prussian blue analogue (PBA) is used as precursor and template to synthesize 3D hollow submicroboxes coated with 2D MoS2 nanosheets (MoS2 @Ni/Co-S) by one-pot solvothermal process. The study shows that the cubic voids in Ni-Co PBA submicrocubes become larger with the prolonging of solvothermal time owing to the etching reactions for Ni-Co PBA submicrocubes. MoS2 @Ni/Co-S synthesized at 200 ℃ for 20 h possesses typical hollow structure, which is a multi-component active material composed of MoS2, CoS, NiS, Co and Ni, and exhibits high specific capacity of 109.8 mAh g?1 at 1 A g?1 and superior rate capability with 75.4% capacity retention at 20 A g?1, the energy density of the assembled asymmetric supercapacitor is as high as 38.5 Wh kg?1 and the device shows excellent cycling stability of 85.4% after 5000 cycles. More importantly, this work not only offers an attractive strategy to combine Ni-Co PBA and classical solvothermal process, but also provides a new insight into the design of PBAs for advanced energy materials.
查看更多>>摘要：Realizing the effective encapsulation of eutectic Al-Si melt is of paramount significance for developing the Al matrix phase change materials in the high-temperature heat storage field. In this paper, a carbon fiber reinforced Al matrix composite phase change material with a Si-rich◎Si-poor cladding structure ([Cf×Si-rich]◎EAl-Si cPCM) was prepared by controlling the precipitation behavior of primary Si under electromagnetic stirring, which can realize the self-encapsulation of eutectic Al-Si alloy. The thermal and structural properties in steady state and non-steady state of the [Cf×Si-rich]◎EAl-Si cPCMs were systematically investigated. The results show that the [Cf×Si-rich] shell has a high thermal conductivity of 53.3–100.7 W/m·K at 200 °C~500 °C. With the increase of Si content in initial Al-Si melt, the high-temperature damage tolerance of the [Cf×Si-rich]◎EAl-Si40 cPCM prepared by Al-40Si is 62.8% higher than that of the [Cf×Si-rich]◎EAl-Si25 cPCM prepared by Al-25Si, but the heat storage capacity is decreased by 22.7%. The [Cf×Si-rich]◎EAl-Si30 cPCM prepared by Al-30Si melt is considered to have the best comprehensive property. Under the non-steady working condition, the [Cf×Si-rich]◎EAl-Si30 cPCM exhibited excellent structural stability and great phase change characteristics (0.3% fluctuation of the melting latent heat and 1.4% fluctuation of the phase change temperature). This work offers new self-encapsulation strategy for extending the application process of Al matrix PCM to the field of high-temperature thermal energy storage.
查看更多>>摘要：Medical titanium alloy has attracted wide attention because of its low elastic modulus (close to bone tissue) and low toxicity. Surface modification treatment by micro-arc oxidation (MAO) on the near-β non-toxic Ti-3Zr-2Sn-3Mo-25 Nb (TLM) titanium alloy was conducted, graphene oxide (GO) was used as modified additive to improve the comprehensive performances especially the ability of inducing hydroxyapatite. The influence of GO particles on the structure, composition and performance were measured and analyzed. Results showed that, GO was successfully participated in the coating formation process, some micropores and cracks were sealed and diminished, reduced the surface roughness. Even though the thickness was decreased, the density was significantly increased. In addition, the critical load strength increased 34%, and lowered the friction coefficient 50%. The electrochemical measurements proved that GO has gain effect on the corrosion resistance of the MAO coating. After immersed in SBF, more HA phase was formed on GO-MAO coating, showing more promising biocompatibility.
查看更多>>摘要：Black TiO2 is identified as a promising photocatalyst because it makes up for the low visible light absorption performance, insufficient solar-light utilization, and slow carrier separation of TiO2. Nevertheless, the shortage of efficient and facile modification methods restricts the improvement of photocatalytic degradation ability. Hence, we proposed a convenient method to prepare Au-loaded black TiO2 nanotubes. During in situ electrochemical reductions, TiO2 nanotubes were transformed into black TiO2 nanotubes, meanwhile, Au was facilely modified on black TiO2 nanotubes. After loading Au, the electron density outstandingly increased to 6 times that of Au-unloaded TiO2 nanotubes because Au efficiently transferred electrons and promoted carrier separation. Consequently, the Au-loaded black TiO2 nanotubes had preferable visible-light photocatalytic performance. 82% RhB was degraded in 60 min and the AQY was 0.85%, which was approximately 2 times and 4 times larger than Au-unloaded TiO2 nanotubes, respectively. Such an in-situ Au modification design provided convenient routes for synthesizing Au-loaded black TiO2 nanotubes with enhanced visible light catalytic performance and further expanding their application potential in the field of photocatalysis.
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Elsevier