Qinqin Liu

Synthesis and characterization of sol–gel derived ZrV2O7 fibers with negative thermal expansion property

Novel ZrV2O7 fibers with negative thermal expansion were prepared via combination of sol–gel process and thermal decomposition. The as-prepared fibers were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy and Raman spectroscopy. The results showed that the synthetic pH value had little influence on the crystal structure of products while showed significant effect on morphology. The fibers obtained at pHxa0=xa09 exhibited cylindrical morphology and its mean diameter was about 1xa0μm. The thermal expansion property of the as-prepared fibers was investigated by in situ XRD and thermal mechanical analyzer. All of the as-prepared fibers showed positive thermal expansion first and then negative thermal expansion, resulting from a phase transition from 3xa0×xa03xa0×xa03 superstructure to 1xa0×xa01xa0×xa01 cubic structure. The macro thermal expansion coefficients of ZrV2O7 ceramic rods increased with decreasing of fiber diameter. The mechanism of the phase transition was also discussed.

Insights Into Highly Improved Solar-Driven Photocatalytic Oxygen Evolution Over Integrated Ag3PO4/MoS2 Heterostructures

Oxygen evolution has been considered as the rate-determining step in photocatalytic water splitting due to its sluggish four-electron half-reaction rate, the development of oxygen-evolving photocatalysts with well-defined morphologies and superior interfacial contact is highly important for achieving high-performance solar water splitting. Herein, we report the fabrication of Ag3PO4/MoS2 nanocomposites and, for the first time, their use in photocatalytic water splitting into oxygen under LED light illumination. Ag3PO4 nanoparticles were found to be anchored evenly on the surface of MoS2 nanosheets, confirming an efficient hybridization of two semiconductor materials. A maximum oxygen-generating rate of 201.6 μmol · L−1 · g−1 · h−1 was determined when 200 mg MoS2 nanosheets were incorporated into Ag3PO4 nanoparticles, which is around 5 times higher than that of bulk Ag3PO4. Obvious enhancements in light-harvesting property, as well as electron-hole separation and charge transportation are revealed by the combination of different characterizations. ESR analysis verified that more active oxygen-containing radicals generate over illuminated Ag3PO4/MoS2 composite photocatalysts rather than irradiated Ag3PO4. The improvement in oxygen evolution performance of Ag3PO4/MoS2 composite photocatalysts is ascribed to wide spectra response in the visible-light region, more efficient charge separation, and enhanced oxidation capacity in the valence band (VB). This study provides new insights into the design and development of novel composite photocatalytic materials for solar-to-fuel conversion.

Synthesis, photocatalytic performance and negative thermal expansion property of nanorods ZrMo2−xVxO8−x/2 with cubic structure

AbstractnCubic ZrMo2−xVxO8−x/2 (0xa0≤xa0xxa0≤xa00.5) compounds, with well-defined nanorods morphology, were synthesized by a facile sol–gel process without using any surfactant or template. The resulting products were characterized by the X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal mechanical analyzer and UV–vis diffuse reflectance spectra (UV–vis DRS). The results indicated that V-doping did not influence the crystal structure and negative thermal expansion (NTE) property, but made rods size increase. Narrowed band gap was observed in V-doped ZrMo2O8. The resultant V-doped ZrMo2O8 samples, as compared with pure ZrMo2O8, exhibited improved UV-light photocatalytic activity, during the photocatalytic degradation of rhodamine B. The mechanism was supposed that the V-doping gave rise to the formation of oxygen vacancies which could enhance photocatalytic performance by reducing the recombination of electrons and holes. In addition, cubic ZrMo2−xVxO8−x/2 also displayed reliable recycling photocatalytic performance and satisfying UV-light catalytic activity for the organic pollutant. Furthermore, all of the resulting cubic ZrMo2−xVxO8−x/2 showed excellent NTE property from 25 to 450xa0°C.Graphical AbstractTEM images of (a) pure ZrMo2O8 and (b) ZrMo1.7V0.3O7.85; (c) RhB degradation under UV-light illumination for 180xa0min in the presence of cubic ZrMo2−xVxO8−x/2 (xxa0=xa00, 0.1, 0.2, 0.3, 0.4 and 0.5) photocatalysts.

Preparation and Thermal Expansion Property of ZrWMoO8/Cu Composite

Abstract High-purity ZrWMoO8 powder was prepared by a precursor decomposition method. To prepare ZrWMoO8/Cu composite, the blended powder of Cu and ZrWMoO8 as well as the copper-coated ZrWMoO8 powder with m(ZrWMoO8):m(Cu)=1:1 were obtained by ball-milling and chemical plating method, respectively. And then the two sorts of the powders were pressed into green specimens which were sintered in argon atmosphere at 500 °C for 3 h to get ZrWMoO8/Cu composites. The thermal expansion properties of the composites were studied, and it is found that the coated-powder is much more suitable for the preparation of ZrWMoO8/Cu material. Results show that after sintering, a part of the ZrWMoO8 is decomposed and reacted with copper in the composite obtained by the blended-powder. While the decomposition of ZrWMoO8 is not detected in the composite obtained with copper-coated ZrWMoO8 powder as raw materials and the composite displays an average thermal expansion coefficient of 3.3774×10−6 °C−1 between 25∼250 °C and the relative density is as high as 90.6%.