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Using Bi(NO3)3·5H2O and Si(OC2H5)4 as the starting materials, citric acid and polyethylene glycol (PEG)-6000 as the complexing agents, pure Bi2SiO5 powders with good photocatalytic activity were first prepared at low temperature via Pechini sol–gel method. The effect of calcination temperature on the preparation of pure phase as well as the photocatalytic properties was investigated. The thermal analysis and X-ray diffraction results showed that the crystallization temperature of Bi2SiO5 is about 400 °C and pure sample can be obtained at 550 °C. The infrared spectra indicated the pure Bi2SiO5 samples have an Aurivillius-like structure. Furthermore, the as-prepared Bi2SiO5 exhibited efficient photocatalytic activity in the decomposition of Rhodamine B due to a synergistic effect of adsorption and photocatalysis.

Bi2SiO5 is a metastable phase compound and one of the important Bi-based Aurivillius phase oxide semiconductors. Pure Bi2SiO5 powders were synthesized successfully by Pechini sol–gel method. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, thermal analyzer, FTIR spectrometer, Raman spectrometer, fluorescence spectrophotometer and UV/Vis/NIR spectrophotometer. The mechanism of the reaction process was studied. The structure, the optical and photocatalytic properties of pure samples were investigated. The results show that citric acid, polyethylene glycol, solvents and calcination temperature have important effects on the reaction, and pure Bi2SiO5 can be obtained at 650 °C for 1 h. The as-prepared Bi2SiO5 has a typical Aurivillius-like structure and its bang gap energy is 3.5 eV. The results of degradation of Rhodamine B reveal that pure Bi2SiO5 powders prepared by Pechini sol–gel method possess a synergistic effect of adsorption and photocatalysis, which indicates that the Bi2SiO5 powders can be used as an efficient material for wastewater treatment.

In this paper, Bismuth silicate (Bi4Si3O12, BSO) powders were prepared by reaction in molten salts (NaCl and KCl) using Bi2O3 and SiO2 powders as raw materials. The effects of salt contents and excessive contents of Bi2O3 and SiO2 were characterized by X-ray diffraction and scanning electron microscopy. The properties of Bi4Si3O12 powders were analyzed via fluorescence spectroscopy. Forming mechanism of platelets was discussed. The experimental results suggest that Bi4Si3O12 powders are produced at 780 °C for 4 h with 40 wt% salts and 5 wt% excessive content of Bi2O3. The peaks of excitation spectrum and emission spectrum for BSO powders are separately located at 266 and 457.6 nm. Compared with crystal materials, the excitation spectrum and emission spectrum of Bi4Si3O12 powders indicate blue shift. Interface reacting mechanism can be used to explain the coarsening process of bismuth silicate platelets produced in molten salt synthesis. In addition, dissolution–precipitation mechanism also plays an important role in the synthesis of bismuth silicate platelets.

Highly ordered Bi4Si3O12 micro-crystals were prepared at normal atmosphere. Phase identification of the prepared crystals was accomplished by X-ray diffractometer (XRD). Domain structure and defects were characterized by environmental scanning electron microscopy (ESEM). XRD shows that the obtained micro-crystals are of eulytite structure with chemical formulation of Bi4Si3O12. A highly ordered growth pattern is confirmed due to the faster growth of the {124} faces than that of the {204} faces by ESEM. The growing process of the domain structure is of pollen parent and filial generation pattern. The filial generations of Bi4Si3O12 crystals are generated from the pollen parent. Cracks generate from the defect areas and propagate along the {124} faces due to their lower binding energy under a proper temperature gradient, contributing to the total transcrystalline fracture. It is confirmed that the generation and development of the voids in the crystal grains can be developed when unmatched dimensions of the two opposite faces are formed. And the development of the voids is dependent on the dimensions and orientations of the two opposite faces.

In the present study, diffusion bonding of a γ-TiAl alloy to a Ti–6Al–4V alloy at the different temperatures ranging from 1073 to 1173 K under an applied stress of 100 MPa for 2 h was investigated. The observation of the microstructure revealed that sound joints between the γ-TiAl Alloy and the Ti-alloy without any pores or cracks could be achieved through diffusion bonding at temperatures over 1073 K under the applied stress of 100 MPa for 2 h. The bond was composed of two zones, and its width increases with the increase of the bonding temperature. The EDS chemical composition profiles indicated that there is a diffusion flux of Al-atoms from γ-TiAl alloy towards the Ti-alloy and of Ti-atoms in the opposite direction. The microhardness of the diffusion bond was in the range of 310–450 HV, and increased monotonously from the side near the γ-TiAl alloy to the side near the Ti-alloy. In this bonding process, the diffusion flux of Ti atoms in interface is mainly controlled by grain boundary diffusion.

SiO2 colloidal spheres were synthesized by Stober method. In order to enhance surface charge of the SiO2 spheres, they were modified with succinic acid. Scanning electron microscope (SEM) shows that the average size of modified SiO2 spheres is 473 nm, and its distribution standard deviation is less than 5%; Fourier-transform infrared spectra (FT-IR) and X-ray photoelectron spectrometer (XPS) results indicate that one end of succinic acid is chemically bonded to the SiO2 spheres through esterification; Zeta potential of the modified SiO2 spheres in water solution is improved from −53.72 to −67.46 mV, and surface charge density of the modified SiO2 spheres is enhanced from 0.19 to 0.94 µC/cm2. SiO2 colloidal crystal was fabricated from aqueous colloidal solution by the vertical deposition method at 40°C and 60% relative humidity. SEM images show that the sample of SiO2 colloidal crystal is face-centered cubic (fcc) structure with its (111) planes parallel to the substrate. Transmission measurement shows the existence of photonic band gap at 1047 nm.