Jianpeng Wu

Microwave-assisted growth of WO3·0.33H2O micro/nanostructures with enhanced visible light photocatalytic properties

Various micro/nanostructured WO3·0.33H2O crystallites were successfully controlled by employing microwave heating under different conditions. By using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high resolution transmission electron microscopy, the phase and morphology of the products were identified. Comparing the as-prepared crystallites under conventional and microwave heating processes found that microwave heating may play a crucial role to initiate the oriented growth of orthorhombic WO3·0.33H2O micro/nanostructures. Moreover, these oriented structures exhibit clearly improved photocatalytic activity over the structures prepared under the conventional heating process. By applying the multi-site complexation model, the improved photocatalytic properties were found to relate to the exposure of high surface acidity orthorhombic WO3·0.33H2O crystallites, which originate from the oriented growth of microstructures prepared under the microwave heating process.

Hydrothermal electrophoretic deposition of yttrium silicate coating on SiC–C/C composites

Abstract Yttrium silicate coatings were deposited on the surfaces of SiC–C/C composites by a hydrothermal electrophoretic process using yttrium silicate nanocrystallites, isopropanol and iodine as source materials, solvent and charging agent respectively. The yttrium silicate nanocrystallites were preprepared by a sonochemical process. The influence of deposition temperatures on the microstructures and degree of crystallisation of yttrium silicate coatings were investigated. The as prepared coatings were characterised by XRD and SEM. Results show that the coatings are composed of yttrium silicate crystallites with Y2Si2O7 as the main phase and smaller amounts of Y2SiO5. The thickness and density of the coatings increase with increasing deposition temperature; but the coating process has little influence on the phase compositions of the coatings.

Synthesis and characterisation of ZnS optical thin films through cathodic electrodeposition technique

Abstract Zinc sulphide (ZnS) thin films were deposited on iridium tin oxide glass by a cathodic electrodeposition technique. The phase compositions, morphologies and optical properties of the prepared thin films were characterised. Both X‐ray diffraction and atomic force microscopy analyses show the growth of ZnS thin films is highly preferential along (200) orientation and the crystallisation of the thin films improves with increasing the solution pH values. The ultraviolet absorption spectra of the films reveal a broad absorption peak ∼300 nm and the bandgap of the as deposited films ranges from 3·42 to 3·71 eV.

Influence of pH value on PbS thin films prepared by electrodeposition

Abstract PbS thin films were prepared on indium–tin oxide transparent conductive film glass substrates using a constant voltage cathodic electrodeposition method. The as deposited thin films were characterised by XRD, AFM and Fourier transform infrared spectrometer. The influence of pH value on the phase compositions, surface morphologies and optical properties of the films has been particularly investigated. Results show that cubic PbS thin films with oriented growth along (111) and (200) direction can be obtained at pH=2·4, deposition voltage=3 V, deposition time=20 min and adding EDTA as a complexing agent. The as deposited thin films exhibit a dense surface morphology. The compressive stress and optical bandgap of the PbS thin films first decrease and then increase with increasing the pH value, and the bandgap of the thin films is calculated to be 0·38–0·39 eV.

Influence of preheating on crystalline anisotropy and particle size of BaTiCoFe10O19 sol–gel powders

Abstract Ultrafine substituted M type barium ferrite BaTiCoFe10O19 powders were synthesised by a sol–gel method. The hydroxide precursor particles were formed in gel solution containing ethanol and water at a ratio of 1:1 and NaOH was used as the co-precipitation agent. The effects of preheating the precursor on the formation and crystalline anisotropy (an indication of magnetocrystalline anisotropy) of BaTiCoFe10O19 powders were studied using X-ray diffraction (XRD) and SEM. The XRD analysis indicated that single phase BaTiCoFe10O19 powders of average particle size 40 nm were formed. Ti–Co substitution and preheating were found drastically to affect the lattice anisotropy (c/a ratio) of hexaferrite powders. Average c/a values increased from 3·9347 for BaFe12O19 powders to 3·9415 for the substituted powder with no preheating and to 3·9392 and 3·9432 with preheating for 1 h at 300 and 400°C respectively. SEM analyses revealed that the particles had plate-like morphology. The particles had higher aspect ratios after no preheating and treatment at 400°C than after treatment at 300°C.

Influence of deposition voltage on phases and microstructure of hydroxyapatite coatings prepared on C–C composites by hydrothermal electrodeposition

Abstract Hydroxyapatite (HAp) coatings were prepared on the surfaces of carbon–carbon (C–C) composites by a novel hydrothermal electrodeposition method. The as prepared HAp coatings were characterised by X-ray diffraction and scanning electron microscopy. The degree of crystallinity, density and homogeneity of the HAp coatings were found to increase with increasing deposition voltage. The deposition rate also increased with increasing deposition voltage.

Preparation of SnO2 nanocrystallites by hydrothermal liquid–solid–solution process

Abstract SnO2 nanocrystallites with regular shape have been successfully prepared by the liquid–solid–solution (LSS) process under hydrothermal conditions. The influences of hydrothermal reaction temperature and [Sn4+] concentrations on the phase composition and particle size of SnO2 crystallites have been particularly investigated. The as obtained crystallites were characterise by X-ray diffraction (XRD), nanoparticle size analyses (NSA) and field beaming scanning electron microscopy (SEM). Results show that the size of the as prepared sphericity SnO2 crystallite is about 9–11 nm. The agglutination of SnO2 nanocrystallites has been observed and the average grain size of the conglomeration was ∼300 nm. The size of as obtained SnO2 nanocrystallites increases with the increase in hydrothermal reaction temperature and [Sn4+] concentrations.

Influence of hydrothermal treatment on the microstructure and oxidation resistance of a Zn4B2O7·H2O (4ZnO·B2O3·H2O) coating for C/C composites

Antioxidant modification for C/C composites by in situ hydrothermal synthesise at 140 °C of a 4ZnO·B2O3·H2O crystallite coating has been successfully achieved. The influence of hydrothermal time on the phase composition, microstructure of the as-prepared Zn4B2O7·H2O (4ZnO·B2O3·H2O), and its antioxidant modification for C/C composites were investigated. Samples were characterised by XRD, SEM, isothermal oxidation test and TG-DSC. Results show that, 4ZnO·B2O3·H2O crystalline coating is achieved on the surface of C/C composites after the hydrothermal treatment at 140 °C for time in the range of 2–12 h. A smooth and crack-free 4ZnO·B2O3·H2O layer can be obtained when the hydrothermal time reaches 8 h. Isothermal oxidation test demonstrates that the oxidation resistance of C/C composites is improved. The as-modified composites exhibit only 1.52 g·cm−2 weight loss after oxidation at 600 °C for 15 h, while the non-modified one shows a 6.57 g·cm−2 weight loss after only 10 h oxidation. For the uncoated C/C composite the oxidation rate is approximately linear with time (non-protective oxidation), thus at 15 h exposure one can estimate the mass loss to be 6.57 g·cm−2 after 10 h for direct comparison with the coated samples.

Synthesis and characterisation of oriented Bi2S3 thin films by novel ultrasonic assisted cathodic electrodeposition route

Abstract A novel ultrasonic assisted cathodic electrodeposition route without using any surfactant, template or toxic/hazardous materials has been applied for the synthesis of Bi2S3 thin films on indium tin oxide (ITO) glass at room temperature. The as deposited thin films were characterised by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and photoluminescence spectrum (PL). Results show that uniform rectangular parallelepiped‐like Bi2S3 thin films with different kinds of orientation growth can be obtained with a solution containing Bi(NO3)3, Na2S2O3 and Na3C6H5O7 at different concentration ratios. (240) oriented film can be obtained at the concentration ratio 1∶5∶1 and (021) oriented film can be obtained at the concentration ratio 1∶9∶1. The obtained (240) orientation growth Bi2S3 thin films exhibit stronger blue green photoluminescence properties under the ultraviolet light excitation at room temperature than (021) orientation growth thin films.

Influence of ultrasonic irradiation power on ZnS nanocrystallites prepared by sonochemical process

Abstract ZnS nanocrystallites have been successfully prepared by a sonochemical process. The influence of ultrasonic irradiation power on the crystallites size and synthesis rate of ZnS nanoparticles during the process was investigated. The as prepared ZnS nanocrystallites were characterised by X-ray diffraction and transmission electron microscopy. Results show that ZnS nanoparticles can be obtained by sonochemical process using zinc chloride and thiacetamide as raw materials. It is found that the as prepared ZnS nanoparticles are hexagonal phase with spherical or spherical-like morphologies. The crystallites size decreases, while the synthesis rate of ZnS nanoparticles increases with the increase of ultrasonic irradiation power in relatively short reaction time (<110 min). There is an extreme point of reaction rate at the ultrasonic irradiation power of 300 W after 110 min reaction.