Papers by Keyword: Homogeneous Precipitation Method

Abstract: Preparation conditions of titanium oxide (TiO₂) powders were examined by the hydrolysis of titanium potassium oxalate (K₂TiO(C₂O₄)₂), through the homogeneous precipitation method (80oC for 24 h) and hydrothermal treatment (160 or 170oC for 1 h). According to the Rietveld analysis, almost a single phase of anatase TiO₂ could be obtained by the hydrothermal treatment at 160oC for 1 h, followed by the heating at 900oC for 10 min in air. The molar ratio of anatase to rutile TiO₂ was found to be controlled by optimizing the hydrothermal conditions in the solution and the heating conditions in air for the photocatalytic activity.

Abstract: The porous basic magnesium carbonate (Mg₅(CO₃)₄(OH)₂^.4H₂O) crystal crystallographic materials with flower-like structure were prepared successfully by homogeneous precipitation method. Magnesium chloride hexahydrate (MgCl₂^.6H₂O) and urea (CO(NH₂)₂) were used as reaction materials. The experimental equipment was held at 100°C for 8 h. Phase and morphology of the product were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The formation mechanism of the product was investigated. It was found that the CO₂ bubbles acted as porous templates. The growth and gathering of the CO₂ bubbles induced the growth of the MgCO₃^.3H₂O columnar crystals. Then the dissolution of the MgCO₃^.3H₂O and the deposition of Mg₅(CO₃)₄(OH)₂^.4H₂O happened simultaneously. Finally the disappearance of MgCO₃^.3H₂O brought about the formation of the porous structure.

Abstract: The nanometric mixed crystals of rutile and anatase TiO₂ also could be prepared by homogeneous precipitation method using both TiCl₄ and TiCl₃ as titanium source. The effects of hard point, the ratio of TiCl₄ to TiCl₃and reaction time on the ratio of nanometer TiO₂ mix-crystals and photo catalysis were studied. The prepared samples were also characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and laser diffraction particle size analyzer. The results show that nanometer TiO₂ mix-crystal with good photo catalytic activity and storage stability can be obtained under the reaction conditions: The ratio of TiCl₄ to TiCl₃ is 4 to 1, pH=0.5, normal pressure, 95°C for 6 hours. The prepared nanometer TiO₂ mix-crystal consisting of anatase of 63.9 wt.% and rutile of 36.1 wt.% is circle with an average size of 25 nm.

Abstract: For the purpose of developing an effective Fe₂O₃-doped nickel-based catalysts to be used in biomass gasification, Fe₂O₃ nanoparticles were prepared by homogeneous precipitation method involving an aqueous solution of Fe (NO₃)₃·9H₂O and urea as precipitator. Different approaches, such as XRD and SEM, were used to characterize the products. Meanwhile, the effects of various technical parameters in preparation process on the yield of products were investigated, and optimal conditions for preparing Fe₂O₃ nanoparticles were found as follows: the molar ratio of urea to Fe (NO₃)₃·9H₂O for 5:1, temperature of precipitation reaction for 125°C, concentration of iron salt for 0.20mol/L. The Fe₂O₃ nanoparticles prepared under the optimal conditions were spherical in shape and well dispersed; they had high purity and a fine crystal phase of cubic syngony with a mean particle size of about 28nm.

Abstract: nanoAl₂O₃ has been synthesized by homogeneous precipitation method using dodecyl trimethyl ammonium bromide (DTAB) as surfactant. The as-prepared powder was characterized by FT-IR, XRD, TEM and SEM. The results indicate the surfactant existence in the precursors but disappeared in the products. This is mainly due to the combination of precursor and surfactant, which results in particles of nanosize. The nucleation and growth rate during the precipitation has also been controlled by the addition of surfactant. During the calcination process, the surfactant has decomposed and volatilized into air. The XRD characterization shows the calcined powders were γ-Al₂O₃ particles with mean size of 27 nm, which was in accordance with TEM characterization. The morphology of the prepared alumina particles has also been investigated by SEM and showed that the powder has a spherical morphology with a uniform particle size.

Abstract: The aim of the present investigation was to examine Si release from the silicon-containing apatite fiber scaffold (Si-AFS) and the biocompatibility of the Si-AFS. We have successfully synthesized silicon-containing apatite fibers (Si-AF) by a homogenous precipitation method. Three-dimensional Si-AFS were fabricated using these Si-AFs. The concentrations of Si in the starting solution were 0 (AF) and 0.8 (0.8Si-AF) mass%. The 0.8Si-AFS1000 were fabricated by firing Si-AF slurry compacts (carbon/Si-AF [w/ ratio: 10/1) at 1300 °C for 5 h. Solubility experiments were carried out in 0.05 mol/dm³ Tris-HCl buffer solutions at pH 7.30 using 0.8Si-AFS1000 (porosity: ~98%), together with Si-free AFS1000 (~98%) for 21 days. The Ca²⁺, PO₄^3- and SiO₄^4- concentrations in the solution were determined by inductively-coupled plasma atomic emission spectrometry (ICP-AES). The biocompatibility of the Si-AFS was examined in vitro using osteoblastic cell, MC3T3-E1 for 21 days. The results of the ICP-AES analysis indicated that the amount of SiO₄^4- ions released from 0.8Si-AFS1000 rapidly increased at 1 day, and then the released SiO₄^4- ions remained constant over a period for 21 days. The cells seeded on/in the 0.8Si-AFS1000 well-proliferated as compared to those on/in the AFS1000. Consequently, we can conclude that the 0.8Si-AFS offers as a potential novel scaffold material, creating a three-dimensional cell culture environment.

Abstract: We focused on the investigation of the influence of carboxylic acid additives on the morphology of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAp) particles synthesized by a homogeneous precipitation method. Three types of carboxylic acids with different number of carboxyl groups, that is, acetic acid, succinic acid and citric acid, were used as additives to control the nucleation, growth and alignment of HAp crystals. The powder properties of resulting particles were examined by powder X-ray diffractometry, fourier-transform infrared spectroscopy, and scanning electron microscopy. All resulting particles were identified to be single-phase carbonate-containing calcium-deficient HAp. The resulting particles synthesized by using acetic acid as an additive were strip-like morphology. In the case of succinic acid addition, the resulting particles exhibited irregular plate-like or spherical morphology. Wheileas, in the case of citric acid addition, the obtained particles became regular spherical shape. These results indicate the numbers of carboxyl groups of carboxylic acid give an influence of the morphology of the HAp particles.

Abstract: The preparation of tin dioxide coated with zinc oxide nanometer powder by factional homogeneous precipitation method is reported in this paper. The diameter of prepared nanometer powder is 32nm. UV shielding , XRD, SEM and EDS of prepared nanometer powder have been investigated. The results show that tin dioxide coated with zinc oxide nanometer powder has excellent UV-shielding performance , and the UV shielding characteristic is better than single tin dioxide or zinc oxide used.

Abstract: Hexagonal prismatic hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAP) was successfully prepared by a homogeneous precipitation method. The products were characterized by X-ray diffraction, Fourier transform infrared spectrum, and scanning electron microscope. The growth process of the hexagonal prism was surveyed in detail based on the effects of the reaction time on the phase composition and the crystal morphology.

Abstract: ZnO is a direct wide band-gap Ⅱ-Ⅵ semiconductor material. For decades, ZnO has gained more and more attention as a wide band semiconductor. This paper introduced a modified homogeneous precipitation method to prepare sheet Ni-doped ZnO crystal. The preparation process was studied and the mechanism of this method was discussed. The properties of the sheet Ni-doped ZnO crystal and the effects of growth parameters on the quality of sheet Ni-doped ZnO crystal were studied using XTJ30-micro image manipulation system, thermal analysis system, X-ray diffraction. etc.