[en] Graphical abstract: (a) TEM image and (b) Polyhedral representation of ZrV_1.6Mo_0.4O_7.2; (c) Thermal expansion curves and (d) Degradation curves of ZrV_2−xW_xO_7+δ (x = 0, 0.1, 0.2, 0.3, and 0.4). - Highlights: • Novel ZrV_2−xW_xO_7+δ solid solutions were first prepared by sol–gel method. • W⁶⁺ doping has influence on the crystal structure. • ZrV_1.6W_0.4O_7.2 shows negative thermal expansion during its corresponding temperature. • W⁶⁺ doped ZrV₂O₇ exhibits superior photocatalytic active than that of pure sample. - Abstract: Tungsten-doped ZrV₂O₇ having good photoactivities under UV-light excitation for the degradation of Rhodamine B has been synthesized by sol–gel method. As-prepared samples were examined by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, UV–vis absorption and photoluminescence spectroscopy. From the structural and morphological characterization it has been stated that the presence of W⁶⁺ induces the progressive stabilization of normal phase with 1 × 1 × 1 cubic structure (centric space group Pa3^¯ (Z = 4)). ZrV_1.6W_0.4O_7.2 shows negative thermal expansion (NTE) at room temperature while ZrV_2−xW_xO_7+δ with other ratios show positive thermal expansion. Mechanism for this change in thermal expansion property was discussed. ZrV_1.6W_0.4O_7.2 also exhibits best photocatalytic performance, the reason is that the occurrence of W⁶⁺ doping ZrV₂O₇ system ZrV₂O₇ system induces the higher photocatalytic activities by promoting the separation of photo-induced electron-hole pairs. PL analysis provides clear evidence of the lower charge carrier recombination in tungsten-doped systems

[en] Graphical abstract: - Highlights: • The g-C_3N_4/V_2O_5 heterocrystals are prepared by one-pot method. • V_2O_5 nanoparticles with diameter of 5 nm intertwined with g-C_3N_4 nanosheets. • G-C_3N_4/V_2O_5 heterocrystals showed excellent photocatalytic activity. • The possible photocatalytic mechanism was discussed. - Abstract: The g-C_3N_4/V_2O_5 composites with visible light photocatalytic performance have been prepared by one-pot method. The g-C_3N_4/V_2O_5 composites were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermogravimetric analysis (TG), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, Brunauer–Emmett–Teller (BET) and X-ray photoelectron spectroscopy (XPS). The results indicated that, within the g-C_3N_4/V_2O_5 composites, V_2O_5 nanoparticles were highly crystallized and intertwined with the lamellas of sheet-like g-C_3N_4 materials, resulting in the generation of well-defined heterostructures. The photocatalytic activity of the g-C_3N_4/V_2O_5 composites was evaluated using Rhodamine B as a target organic molecule. Under visible light illumination, as-prepared g-C_3N_4/V_2O_5 hybrid materials demonstrated highly improved photocatalytic activity than g-C_3N_4 and V_2O_5 materials. The enhancement in visible-light-driven photocatalytic activity can be ascribed to the formation of heterojunctions between V_2O_5 and g-C_3N_4, which promoted faster electron–hole separation and favored more efficient charge transfer.

[en] Cubic ZrWMoO₈ powders with rod-like aggregate and thin fasciculus-like and flower-like rod cluster morphologies have been successfully fabricated with different amounts of (NH₄)₂HPO₄ as surfactant using a hydrothermal method. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry were utilized to investigate the influence of the addition of (NH₄)₂HPO₄ on the crystallization process and crystal morphology of the resulting products. The results show that the purity and the thermal expansion property of the resulting products are not influenced by the addition of (NH₄)₂HPO₄. The cubic ZrWMoO₈ powders with both rod-like aggregate and flower-like rod cluster morphologies show a positive thermal expansion property in the temperature range from room temperature to 120 C, while they show a negative thermal expansion property in the temperature range from 120 C to 700 C. The abnormal thermal expansion property of cubic ZrWMoO₈ below 120 C is caused by the presence of water molecules. Investigations also show that the essence of the different morphologies of the ZrWMoO₈ particles obtained is the result of the different aggregation modes of the nanorods, which act as nuclei, and the corresponding aggregation process is dominated by the addition of (NH₄)₂HPO₄ and its amount. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] We have developed a piezoelectric microvalve with a silicon seat for the propulsion system of a micro-satellite. The silicon seat is fabricated with narrow sealing rings to reduce internal leaks. The fatigue performance of the silicon seat is characterized. The lifetime of the silicon seat without coating is approximately 25 000 times, which cannot meet the requirement for astronautic applications. To improve its fatigue performance, the silicon seat is deposited with Cu and parylene, respectively. The two seats both meet the sealing requirement after 10"5 cycle operation. Several rings of the seats deposited with Cu fractured after the fatigue tests, whereas none of the rings of the seats deposited with parylene fractured due to the obvious reduction of the impact stress. (paper)

[en] Exploitation of anode materials with pronounced discharge capacity and excellent cycling stability is the underlying in guaranteeing the large-scale utilization of lithium-ion batteries (LIBs) to meet the increasing demand for high power density electric vehicles, but still a great challenge. In this work, we fabricated well-dispersed MgFe₂O₄ nanospheres (MFONS) by a facile process and followed by annealing process, then employed as anode-active electrodes for LIBs. The electrochemical performance demonstrated that our prepared MFONS exhibits high initial discharge capacity of 1038 mAh g^-1 under the current density of 500 mA g^-1 and maintained at 634 mAh g^-1 after cycling 350 times. Moreover, the reversible capacity could keep stable at * 468 mAh g^-1 even at current density up to 3.2 A g^-1 . The excellent performances of MFONS should be attributed to the high dispersion, small nanosphere size, mesoporous nanostructure and large specific surface area which provide buffer room for volume expanding during discharge/charge process. (author)

[en] Highlights: • Novel vacancy defective perovskite fluoride K_0.82Co_0.43Mn_0.57F_2.66@rGO (KCMF(1-1)@rGO) anode was introduced to boost kinetics and stability for Na-ion storage. • Ex situ techniques revealed the pseudocapacitance-dominated conversion-insertion hybrid mechanisms of KCMF(1-1)@rGO anode for Na-ion storage. • The Na-based dual-ion batteries (Na-DIBs) and capacitors (NICs) devices based on KCMF(1-1)@rGO anode showed remarkable performance. -- Abstract: Na-based dual-ion batteries (Na-DIBs) and capacitors (NICs) have received particular attention in the recent years because of the advantages of simple design, environmentally friendly, feasibility, and low cost, etc. Herein, we report a new vacancy defective perovskite fluorides K_0.82Co_0.43Mn_0.57F_2.66@reduced graphene oxide (KCMF(1-1)@rGO) nanocrystal as a promising anode material for Na-DIBs and NICs, showing the pseudocapacitance-dominated conversion-insertion hybrid mechanisms. Thanks for the synergistic effect of Co/Mn active species, the fast kinetics of pseudocapacitive behavior, the improved ion storage ability of K-ion vacancy, and the unique K_0.82Co_0.43Mn_0.57F_2.66@rGO nano-heterostructures, the KCMF(1-1)@rGO anode exhibits superior specific capacity, rate and cycling behavior (176-84 mAh g⁻¹ at 0.05-1 A g⁻¹, 67 % retention/500 cycles/0.3 A g⁻¹). Furthermore, the designed Na-DIBs and NICs with the KCMF(1-1)@rGO anode and graphite (KS6)/activated carbon (AC) as cathodes demonstrate remarkable performance, showing the 145.9 Wh kg⁻¹/0.83 kW kg⁻¹/60%/1000 cycles/5 A g⁻¹ and 66.51~29 Wh kg⁻¹/0.53~16.84 kW kg⁻¹/81%/1000 cycles/5 A g⁻¹ for the KCMF(1-1)@rGO//KS6 Na-DIBs and KCMF(1-1)@rGO//AC NICs respectively, indicating a promising application for Na-ion energy storage.

[en] Highlights: ► Cubic β-ZrMo₂O₈ film was first prepared via the sol–gel method. ► Crystalline precursor film transformed to amorphous gel film. ► The lattice parameters of the ZrMo₂O₈ film were a = b = c = 8.976 Å. ► Cubic β-ZrMo₂O₈ film shows good negative thermal expansion (CTE = −8.66 × 10⁻⁶ K⁻¹). ► Cubic β-ZrMo₂O₈ film transformed to trigonal phase at 480 °C. - Abstracts: ZrMo₂O₈ film with cubic β-ZrW₂O₈ structure was prepared on glass substrates via the sol–gel dip coating method. The structural, compositional, morphological and thermal expansion properties of the ZrMo₂O₈ film were studied using X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The bonding strength of the as-prepared films was measured by scratch testing. The results indicated that crystalline ZrMo₂O₇(OH)₂(H₂O)₂ precursor powders changed into amorphous gel as the coordination reaction of citric acid and polyvinylpyrrolidone (PVP) with metal ions. Cubic β-ZrMo₂O₈ film consisting of ball-like particles could be obtained after annealing the gel film, and the bonding strength decreased from 27.8 N (gel film) to 8.7 N (β-ZrMo₂O₈ film). The room temperature lattice parameters of resulting cubic β-ZrMo₂O₈ film are a = b = c = 8.976 Å, and this film exhibited excellent negative thermal expansion (CTE = −8.66 × 10⁻⁶ K⁻¹) property from room temperature to 430 °C.

[en] ZrW₂O₈ powders were prepared by hydrothermal thermal method using sodium dodecyl benzene sulfonate (SDBS) as surfactant. The products were investigated by X-ray diffraction (XRD) method, scanning electron microscopy (SEM), thermogravimetric and differential scanning calorimetry (TG-DSC) and Fourier transform infrared (FTIR) absorption spectra. Results indicate that the resulting powders are single cubic phase with high crystallinity. With increasing the amount of SDBS, morphology and particle size change from rod-like with an average dimension of 1.2 μm x 1.2 μm x 10 μm to layered column with an average diameter of 0.4 μm. ZrW₂O₈ powders exhibit negative thermal expansion property. And the amount of SDBS is not influence on the average thermal expansion coefficients. The thermal expansion coefficients are about similar with an average value of -5.8 x 10^-6 deg. C^-1 from room temperature to 500 deg. C. However, the morphology has some effect on the thermal expansion coefficient of α-ZrW₂O₈.

[en] Hexagonal Zn₃(OH)₂V₂O₇·2H₂O nanoplates have been successfully synthesized via a facile and template-free hydrothermal method. The nanocrystals have a hexagonal shape with 650–750 nm in diameter and 120–140 nm in thickness. The possible mechanism of forming such hexagonal Zn₃(OH)₂V₂O₇·2H₂O nanoplates may be due to its inherent anisotropic crystal structure. Magnetic hysteresis measurement indicates that the as-synthesized hexagonal Zn₃(OH)₂V₂O₇·2H₂O nanoplates have weak ferromagnetic property at room temperature. Compared to the floriated-like nanostructured Zn₃V₂O₇(OH)₂(H₂O)₂ synthesized by a hydrothermal route, the as-prepared hexagonal Zn₃(OH)₂V₂O₇·2H₂O nanoplates exhibited a significant increase in the methylene blue (MB) photodegradation rate under UV irradiation. Highlights: • Hexagonal Zn₃(OH)₂V₂O₇·2H₂O nanoplates was synthesized via a hydrothermal method. • Magnetic study indicates that the nanoplates are of weak ferromagnetic property at room temperature. • The nanoplates exhibit greatly enhanced activity in the UV-light photocatalytic degradation of methylene blue

[en] Novel ZrV₂O₇ microfibers with diameters about 1–3 μm were synthesized using a sol–gel technique. For comparison, ZrV₂O₇ powders were prepared by the same method. The resultant structures were studied by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy. The results indicated that both the pure ZrV₂O₇ microfibers and powders could be synthesized by the sol–gel technique. The thermal expansion property of the as-prepared ZrV₂O₇ microfibers and powders was characterized by a thermal mechanical analyzer, both the fibers with cylindrical morphology and irregular powders with average size between 100 and 200 nm showed negative thermal expansion between 150 °C and 600 °C. The photocatalytic activity of the microfibers was compared to that of powders under UV radiations. The band gap of ZrV₂O₇ microfibers decreased and its absorption edge exhibited red shift. The microfibers also had a higher surface area compared with the powders, resulting in considerably higher photocatalytic characteristics. The large surface area and the enhanced photocatalytic activity of the ZrV₂O₇ microfibers also offer potential applications in sensors and inorganic ion exchangers. - Graphical abstract: (a and c) SEM photos of ZrV₂O₇ powders and fibers. (b and d) TEM images of ZrV₂O₇ powders and fibers. (e) Thermal expansion curves of ZrV₂O₇ powders and fibers. (f) Degradation curves of ZrV₂O₇ powders and ZrV₂O₇ fibers. - Highlights: • Novel ZrV₂O₇ fibers could be synthesized using sol–gel technique. • ZrV₂O₇ powders with irregular shape are also prepared for comparison. • Both ZrV₂O₇ microfibers and powders exhibit negative thermal expansion property. • ZrV₂O₇ microfibers show outstanding photocatalytic activity under UV irradiation. • This synthesis technique can be easily extended to many other functional fibers