Search

In this study, BiVO4/CuWO4 nanocomposites with S-scheme heterojunction structure were prepared firstly and the properties were analyzed by various techniques. The sonocatalytic activity was evaluated by the degradation of tetracycline (TET). Under the optimum experimental conditions of initial concentration of TET = 25 mg/L, composite ratio of BiVO4 and CuWO4 = 15%, catalyst addition = 1 g/L, ultrasonic time = 120 min, ultrasonic power = 500 W, pH = 7, the experiment results showed that BiVO4/CuWO4 sonocatalyst removed TET by 81.05 ± 2.92%. K2S2O8 was verified to enhance the sonocatalytic performance of BiVO4/CuWO4 efficiently, and the removal ratio of TET could reach 91.25 ± 1.95% within 120 min by using BiVO4/CuWO4 and K2S2O8. The free radical (ROS) quenching experiment and TA-PL technology proved that the main free radical of degradation was ·OH. The potential sonocatalytic mechanism showed that the enhanced catalytic efficiency was due to the construction of S-scheme heterojunctions, which improved electron–hole pair (e−–h+) separation efficiency and rapid kinetics. The speculated TET degradation route of TET included intermediate products was proposed and four reused experiments proved that BiVO4/CuWO4 had good recyclability. In conclusion, the prepared BiVO4/CuWO4 composites with S-type heterojunction mechanism have more possibilities in wastewater treatment, which provides a helpful guide for the synthesis and application of composite sonocatalysts. [ABSTRACT FROM AUTHOR]

The nanostructured Mg3Sb2 and Mg3.17Y0.03Sb1.985Te0.015 bulks were prepared using the induction melting-melt spinning (MS)-spark plasma sintering (SPS) method. The grain size of the sample prepared by this method was 50–80 nm. Mg3Sb2 materials co-doped with Y and Te effectively improved the carrier concentration and mobility. The room temperature carrier concentration was significantly increased from 1.28 × 1018 cm−3 for Mg3Sb2 to 7.12 × 1019 cm−3 for Mg3.17Y0.03Sb1.985Te0.015, and carrier mobility from 21.80 cm2V−1 s−1 for Mg3Sb2 to 67.53 cm2V−1 s−1 for Mg3.17Y0.03Sb1.985Te0.015. More carriers were introduced by the doping of the Mg site with the Y element. When Te replaced Sb in the covalent bonding layer, it weakened the polar covalent bond with Mg, thus favoring the movement of carriers. Meanwhile, the co-doping of Y and Te enhanced phonon scattering and reduced the thermal conductivity. The thermal conductivity of the nanostructured Mg3.17Y0.03Sb1.985Te0.015 is about 0.74 Wm−1 K−1, which was only 69% of the bulk counterparts. When the grain size reached the nanometer scale, the grain boundary density increased substantially. The periodic potential field within a single grain was destroyed at the grain boundary. The interface interfered with the carriers and phonon transport, which further reduced the thermal conductivity. At 773 K, the ZT peak value of the nanostructured Mg3.17Y0.03Sb1.985Te0.015 was improved to 1.28, which was significantly higher than that of the non-doped samples. [ABSTRACT FROM AUTHOR]

The effects of aging temperature on the precipitation of the γ′-Co3(Al, W) phase were studied by utilizing transmission electron microscopy, scanning electron microscopy and atom probe tomography, with the aim of exploring the continuum kinetics of the γ′ phase in the medium supersaturation Co–9Al–8W (at.%) alloy from early precipitation to later coarsening. The results showed that the γ′ phases with small size and large number density caused a rapid increase in alloy microhardness at 1073 K when the aging time was less than 136 h, implying that precipitation strengthening clearly occurred. Due to the high thermodynamic driving force and small critical radius of nucleation, the γ′ phases expeditiously precipitated within 0.08 h of aging. Additionally, the partitioning coefficients of the elements showed that the partitions of Al and W in the γ′ phase were more obvious at 1073 K. The time exponents of the average particle radius were close to the value of 1/3 predicted by the Lifshitz–Slyozov–Wagner theory. The particle size distribution of the γ′ phase was more consistent with the Brailsford–Wynblatt model in the early growth-dominated stage, whereas it matched well with the trans-interface diffusion-controlled model in the later concomitant growth and coarsening stages. This research revealed the intimate relationship among the morphology, mechanical properties and evolution kinetics of the γ′ phase in a medium supersaturation Co–Al–W alloy. [ABSTRACT FROM AUTHOR]

EP/SiO2 nanocomposites, which contained PEO flexible chain, have been prepared via epoxy resin and PEO-grafted silica particles. The PEO-silica particles were obtained by endcapping PEO-1000 with toluene 2,4-diisocyanate (TDI), followed by a reaction with silica sols. The chemical structure of the products was confirmed by IR measurements, and the mechanical properties of composites such as impact strength, flexural strength, dynamic mechanical thermal properties were investigated. The results showed that the addition of the PEO-grafted silica particles to the epoxy/DDS curing system, the impact strength is 2 times higher than that of the neat epoxy. While the storage modulus and the glass transition temperature are a little changed. The morphological structure of impact fracture surface and the surface of the hybrid materials were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM), respectively. [ABSTRACT FROM AUTHOR]