Search

It is important to reduce costs and improve performance by microstructure-control of materials. The direct precipitation method and hydrothermal method were adopted to adjust the crystallinity of zinc tungstate (ZnWO4) pigments. Correlation between the crystallinity of ZnWO4 and its anti-corrosion performance is explored. The results confirm that ZnWO4 crystals prepared by hydrothermal reaction for 12 h have high crystallinity, and the corrosion resistance is enhanced by 737.0% compared with blank coating in the epoxy resin system. The improvement in corrosion inhibition is due to the enhancement of the shielding effect of the multilayer passivation film and electronic suppression effect resulted from the high ZnWO4 crystallinity. The low ZnWO4 crystallinity can weaken the corrosion resistance because of the defect-enriched effect. Advancement in anticorrosive performance by crystallinity-control meets the reduction of costs and energy consumption in the coatings industry. The correlation between the crystallinity of ZnWO4 and its anti-corrosion performance is discovered. ZnWO4 crystals prepared by hydrothermal method for 12 h have high crystallinity. The corrosion resistance is enhanced by 737.0% compared with blank coating in the epoxy resin system. The improvement in corrosion resistance originated from the enhancement of the shielding effect of the multilayer passivation film and electronic suppression effect resulting from the high ZnWO4 crystallinity. [ABSTRACT FROM AUTHOR]

The discharge of wastewater containing hexavalent chromium (Cr(VI)) would cause serious environmental pollution and endanger human health. Design of high-performance and stable photocatalysts for Cr(VI) reduction in neutral solution remain huge challenging. Herein, a novel starfish-like zinc tungstate/zinc benzoate (ZnWO 4 /Zn(Bro) 2) inorganic/organic heterojunction photocatalyst was synthesized via a facile hydrothermal method. The starfish-like zinc tungstate was decorated with uniform dispersed zinc benzoate nanosheets via a self-assembling process, The intimate interface between inorganic and organic phase significantly boosted the transport efficiency of photogenerated carriers and reduced the recombination probability of e- and h+, and enhanced the photocatalytic efficiency for Cr(VI) reduction. the optimized ZWBR-2 composite catalyst displayed conspicuous photocatalytic activity and stability towards the Cr(VI) reduction in neutral solution. This work gives a new perspective to design efficient and promising inorganic/organic heterojunction photocatalyst used in dealing with Cr(VI) in neutral solution. [Display omitted] • Novel starfish-like ZnWO 4 /Zn(Bro) 2 inorganic/organic heterojunction was synthesized by a facile hydrothermal process. • The intimate interface between ZnWO 4 and Zn(Bro) 2 profoundly boosted the transport efficiency of photogenerated carriers. • ZnWO 4 /Zn(Bro) 2 showed conspicuous photocatalytic activity and stability towards Cr(VI) reduction in a neutral environment. [ABSTRACT FROM AUTHOR]

Nanosized Zn–WO 3 and ZnWO 4 materials have been prepared by microwave irradiation method. The physico-chemical characterization of the prepared nanomaterials was carried out by X-ray diffraction (XRD) and high resolution-scanning electron microscopy (HR-SEM) techniques. The size and shape of the ZnWO 4 material can be controlled by changing the temperature. The XRD analysis revealed the formation of monoclinic phase of the calcined nanopowder. The HR-SEM images showed the sphere and plate shape particles. The electrochemical behavior of the ZnWO 4 modified electrodes was investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) techniques. The synthesized material shows the pseudocapacitance. The specific capacitance of 35.70 F/g was achieved for the Zn–WO 3 nanopowder. [ABSTRACT FROM AUTHOR]

Monoclinic ytterbium-lithium codoped zinc monotungstate crystal (Yb3+,Li+:ZnWO 4) is a promising material for laser opertation at ~1.06 μm. Absorption, σ abs , and stimulated-emission, σ SE , cross-sections are determined for light polarized along the optical indicatrix axes, E || N p , N m and N g. At room temperature, the maximum σ SE amounts to 2.81 × 10−20 cm2 at 1055.6 nm (for E || N p) and the gain bandwidth reaches ~22 nm (for E || N g). The radiative lifetime of the upper laser level is 0.37 ms. The Stark splitting of Yb3+ multiplets is resolved with low-temperature (6 K) spectroscopy revealing a relatively large total splitting of the ground-state, Δ E (2F 7/2) = 804 cm−1, being remarkably high as compared to other Yb3+-doped tungstate crystals. A notable inhomogeneous broadening of the zero-phonon line is detected at 6 K. A continuous-wave diode-pumped 1.8 at.% Yb3+,Li+:ZnWO 4 laser generated a maximum output power of 2.90 W at ~1059 nm with a slope efficiency of 57.9% and a linearly polarized output ( E || N p). Yb3+,Li+:ZnWO 4 is attractive for broadly tunable and mode-locked oscillators. • Monoclinic ytterbium-lithium codoped zinc monotungstate crystal (Yb3+,Li+:ZnWO 4). • Absorption and stimulated-emission cross-emission cross-sections for polarized light. • The maximum σ SE is 2.81 × 10−20 cm2 at 1055.6 nm and the gain bandwidth reaches ~22 nm. • The Stark splitting of Yb3+ multiplets resolved with low-temperature spectroscopy. • Diode-pumped laser generated 2.90 W at ~1059 nm with a slope efficiency of 57.9%. [ABSTRACT FROM AUTHOR]

Zinc tungstate is an inorganic material which shows immense potential in diverse areas such as photoluminescence, sodium-ion batteries, and catalysis. Thus, the synthesis and characterization of ZnWO 4 by ultrasonic spray pyrolysis using different heat treatments (between 750 °C and 1000 °C) is reported herein. X-ray diffraction and Raman spectroscopy were used to confirm the formation of the ZnWO 4 with wolframite-type monoclinic structure. Scanning electron microscopy images revealed that the ZnWO 4 particles have a microsphere-like morphology formed by the junction of different nanocrystals and its surface changed by heat treatment. The bandgap energies had a small variation among the samples (3.88 eV–3.98 eV). The photoluminescence emission of the samples showed a broadband spectrum with white light, in which structural alterations occurred with the increase in the heat treatment, which also increased the emission intensity and broadband. The samples synthesized at 950 °C and 1000 °C showed to be promising warm- and neutral-white light emission sources. • ZnWO 4 samples were obtained with success by ultrasonic spray pyrolysis. • Heat treatment modifications provoked structural and morphological alterations. • Photoluminescence spectra were influenced by change structural. [ABSTRACT FROM AUTHOR]

• ZnWO 4 was used as a sonocatalyst to degrade meloxicam for the first time. • The degradation ratio had reached 75.7% under experimental condition. • Effects of key parameters on sonocatalytic degradation of meloxicam were studied. • Meloxicam degradation pathways and reaction mechanism in the system were proposed. Zinc tungstate (ZnWO 4) was previously used as a photocatalyst. In this paper, for the first time as an sonocatalyst, the performance of ZnWO 4 for sonocatalytic degradation of meloxicam (MEL) under ultrasonic irradiation were studied. Firstly, ZnWO 4 nanomaterials were synthesized at different acidity (pH = 5, 6, 7, 8, 9) via the hydrothermal method. Utilizing SEM, XRD and EDS techniques to characterize composition and morphology of each product, the same crystal forms, but different morphologies (nano-sheet, nano-microspheres or nano-rod) of ZnWO 4 could be obtained. Secondly, the sonocatalytic activities of ZnWO 4 on degradation of MEL were studied. It was found that the degradation ratio varied with the synthetic pH values, with ZnWO 4 under synthetic pH = 6 exhibiting the best sonocatalytic performance (75.7%). While being synthesized at this pH value, ZnWO 4 nano-microspheres had the largest BET surface area (27.068 m2/g), the smallest particle size (40–60 nm) so as to provide more active sites on its surface, which were able to produce more reactive oxygen species (ROS) and holes under ultrasonic irradiation. These ROS and holes had a positive effect on the degradation of MEL into CO 2 , H 2 O and inorganic. Thirdly, various influential factors including ultrasonic power intensity, ultrasonic time, catalyst addition dosage, initial concentration of MEL solution and reusability of catalyst were also explored. Under the condition of 10 mg/L MEL concentration, 20 mg catalyst dosage, 120 min irradiation time, 0.278 W/cm2 ultrasonic power intensity, the degradation ratio on MEL reached 75.7%. Finally, the presence of hydroxyl radical (OH) and singlet molecular oxygen (1O 2) in the reaction was confirmed by adding ROS scavenger. The experimental results suggested that ZnWO 4 nanoparticle could be used not only as an effective photocatalyst, but also, under the condition of ultrasonic irradiation, a promising sonocatalyst for degradation of organic pollutants in aqueous media. [ABSTRACT FROM AUTHOR]