Search

Metastable Bi2SiO5 phase powders were synthesized successfully by Pechini sol-gel method using a simple starting hydro-alcoholic solution consisting of Bi(NO3)3 · 5H2O, TEOS, citric acid, and PEG-6000. The effects of Bi/Si molar ratio, citric acid, and PEG-6000 on the properties of pure Bi2SiO5 powders were investigated. The crystalline phase and fluorescence properties were characterized. The process of Pechini sol-gel method and the effect of purity on fluorescence properties were studied in this paper. X-ray diffraction results illustrate that single phase of Bi2SiO5 can be obtained at 650°C for 1 h. Furthermore, the maximum fluorescence emission wavelength of the powders is located at 355 nm, which represents the band gap of Bi2SiO5 powders is 3.49 eV.

In this article, Bi2SiO5 powders were prepared by molten salt method. Via uniform experiment, the effects of various technological parameters (sintering temperature, holding time, excessive contents of Bi2O3 by weight, and ratios of salts) on synthesis of Bi2SiO5 powders were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal analysis. Forming mechanism of sheets was discussed. According to the analysis of XRD and SEM, the sample mainly contains Bi2SiO5 phase when the temperature is 650°C, holding time is 2.5 h, excessive content of Bi2O3 is 5 wt%, and the ratio of salts is 50 wt%. Interface reacting mechanism can be used to explain the coarsening process of bismuth silicate sheets produced in molten salt synthesis. In addition, dissolution–precipitation mechanism also plays an important role in the synthesis of bismuth silicate sheets.

The bismuth silicate powders were prepared by reaction of Bi2O3 and SiO2 as raw materials in KCl-K2CO3, NaCl-Na2CO3, K2CO3-Na2CO3, KCl-NaCl, NaCl-Na2SO4, and KCl-K2SO4 molten salts. Pure Bi12SiO20 powders were synthesized in KCl-K2CO3 flux at 635°C for 1 h, which was lower than that of conventional solid state reaction. X-ray diffraction reveals that the phases of the samples are different in various molten salts. Only Bi12SiO20 phase can be observed in the molten salts with ions. However, a mixture of Bi12SiO20, Bi2SiO5, and Bi4Si3O12 phase are observed in the molten salts without ions. Therefore, the carbonates are not only used as the flux and reaction medium, but also inhibit the formation of other bismuth silicates in the synthesis of Bi12SiO20 powders by molten salt synthesis. The scanning electronic microscopy image indicates that the mechanism of molten salt synthesis in the case of KCl-K2CO3 and NaCl-Na2CO3 are “dissolution-precipitation mechanism.” UV-Vis spectra reveals the absorption edge for ...

In this work, barium titanate (BaTiO3) powders were synthesized via two Pechini sol-gel processes using citric acid and polyethylene glycol-6000 as chelating agents. Attempts had been made to understand the thermal behavior of the polymeric intermediates with the help of thermogravimetry-differential scanning calorimetry (TG-DTG-DSC) thermograms. The structural coordination of as-prepared polymeric intermediates was investigated by Fourier transform infrared (FTIR) analysis. The phase and structure of the powders calcined at different temperatures were characterized by X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM). Preparation of the polymeric precursors can influence the mechanism of the BaTiO3 synthesis. The formed intermediate phase BaCO3 appears in gel-2 system, and BaCO3 phase does not disappear at 720°C. The formed intermediate phases of gel-1 differ from that of gel-2. The intermediate phases of gel-1 are anatase TiO2 and rutile TiO2, and the intermediate phase Ba...

In this article, Ni0.5Zn0.5Fe2O4 ferrite powders were prepared by a reaction between Fe2O3, NiO, and ZnO powders in a molten salt. This article investigated the effects of firing temperature and holding time on the properties and microstructure of Ni-Zn ferrite powder via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermal analysis. The synthesis mechanism is discussed. At 900°C, the grain contained pure spinel Ni0.5Zn0.5Fe2O4 and the grain size was smaller, so that Ni0.5Zn0.5Fe2O4 ferrite ceramic was easier to sinter. FESEM images illustrate that the average grain size increased as the sintereing temperature increased from 900 to 1050°C. The grain shapes changed from triangular patterns to cubic structures with the increase of temperature. The respective solubilities of NiO, ZnO, and Fe2O3 in flux controlled the synthesis mechanism.

HA-Bioglass-Al2O3 composites were successfully fabricated by mixing HA, synthesized by wet chemical method between precursor materials H3PO4 and Ca(OH)2, with 25 wt% Al2O3 and different content of bioglass (5, 25, 45, and 65 wt%), respectively, with a mole fraction of 53.9%SiO2, 22.6%Na2O, 21.8%CaO, and 1.7 wt%P2O5, sintered in air at relative low temperature (750–950°C) for 2 h. It can be seen that when the content of bioglass is above 45 wt% in the composite, the decomposition of HA to β-TCP, considerable thermal reaction and phase degradation are suppressed, and the main phases in this case are Al2O3, HA, and a small amount of DCP (CaHPO4) and β-TCP, which almost have the same chemical composition, forming ternary-glass phase, and have better bioactive than pure HA. It can also be found that the exposed HA particles increase with the increasing of the bioglass content in the mixture. A large number of HA particles stacked together are subjected to form roughened surface, wherein microcracks, voids, and...