Abstract: Fine yttrium stearate powder was produced at a relatively low temperature using yttrium nitrate hexahydrate, ammonia and stearic acid as the raw materials. Dispersed Y2O3 nanopowder was synthesized by calcining the yttrium stearate. The formation mechanism of the precursor and the Y2O3 nanopowder was studied by means of XRD, TG-DTA, FT-IR, BET, FE-SEM and HR-TEM. Pure and dispersed Y2O3 nanopowder with an average particle size of 30 nm was produced by calcining the precursor at 600 °C. The particle size increases to about 60 nm with the increase of the calcination temperature to 1000 °C. In the preparation of Y2O3 from yttrium stearate, no water medium is involved, thus capillarity force and bridging of adjacent particles by hydrogen bonds can be avoided, resulting in good dispersion of the particles. The dispersed Y2O3 nanopowder prepared in this work has potential application in phosphors and transparent ceramic materials.
Abstract: Gd2Zr2O7 nanocrystals with cubic structure were prepared via the citric acid chelating agent method using zirconium oxychloride and gadolinium oxide as starting materials. The samples was characterized using thermal gravimetric-differential thermal analysis, X-ray diffraction technique, Fourier transform infrared methods, transmission electron microscopy technique, and laser particle size analyzer instrument. The effect of the heat treatment temperature on the Gd2Zr2O7 nanocrystal grain size was also analyzed. The results show that citric acid and ethylene glycol underwent esterification, and the metal ions were wrapped in an organic network, resulting in molecular-level dispersion. A single Gd2Zr2O7 phase was formed at 600 °C, and the crystal size of the nanocrystals increased with increasing thermal treatment temperature. Gd2Zr2O7 with an excellent defective fluorite structure, which belongs to the space group, was prepared after treatment at 900 °C for 2 h. The Gd2Zr2O7 crystallites consist of 50 nm to 60 nm spherical particles with agglomerated structures. In addition, the d111 and d222 interplanar distances were 0.310 and 0.152 nm, respectively, which were measured from high resolution transmission electron microscopy images.
Abstract: The homogeneous precipitation pathway was explored to synthesize ultrafine powders of Al(OH)3. In the experiment, the scrap aluminum were used as raw material . The effects of reaction time, reaction temperature, stirring speed, concentration of sulphuric acid and dispersant on the preparation process were investigated. The results showed that ultrafine Al(OH)3 powders can be yielded and well-controlled under the following optimal conditions: the concentration of sulphuric acid 3.0 mol•L-1, reaction temperature 0-4 °C, stirring speed 900 r.min-1 and reaction time 15 min. The diameter less than 100nm of sphericity Al(OH)3 particles with the narrow distribution were successfully obtained. The Al(OH)3 powders was analyzed with scanning electron microscopy , infrared spectrometer. The Al(OH)3 powders have good dispersancy and purity is more than 90%. The operation of the experiment was very simple, and the particles were separated easily.
Abstract: Nanocrystalline LaFeO3 with particle size of about 50 nm was directly synthesized by sol–gel auto-combustion method at room temperature. The overall process involves three steps: formation of homogeneous sol; formation of dried gel; and combustion of the dried gel. Single phase nanocrystalline LaFeO3 powders were successfully synthesized by the sol–gel self-propagation combustion method using glycin (C2H5NO2) as the chelating agent. Discuss the synthesis products by DTA/TG, XRD and SEM. The experiment results show that the LaFeO3 nano-powder was got from dried gel of G/M=1:1 at 300°C ignition temperature and then holding 2h at 800°C.The LaFeO3 nano-powder is about 50nm with excellent dispersibility. The hysteretic loop show LaFeO3 nanopowders have the character of ferromagnetism, the coercivity of the nanocrystalline LaFeO3 is 99G, while the saturation is only 2.8 emug-1.
Abstract: Selecting graphene oxide (GO) and the Degussa P25 TiO2 (80% anatase and 20% rutile) as raw materials, the composites of graphene/TiO2 nano-tubes were simply and quickly prepared under the conditions of a concentrated solution of sodium hydroxide. The as-obtained composites’ phase structure was analyzed and characterized by powder X-ray diffraction (XRD), their morphologies were also observed and cross-confirmed under the Transmission Electron Microscopy (TEM). The measurements showed that the composites prepared in this work have a remarkable structure, and compared to the seperate TiO2 nano-tubes, the agglomeration of TiO2 nano-tubes covered on the surface of the graphene is apparently not so serious. In view of this, we preliminary tested the composites’ photo-catalytic performance with the visible light irradiation, and also made a comparison with TiO2 nano-tubes.
Abstract: Aluminium titanate - based hollow balls were prepared by using aluminum titanate, mullite and magnesia aluminate spinel as starting materials followed by the rolling-ball method. The effect of different pore-making agents (namely the amylum, flour, millet and urea) on the forming properties and the apparent qualities of the precursors of the hollow balls were investigated. The results show that the precursors of the hollow balls own both good forming properties and apparent qualities when using the amylum as pore-making agent; an appropriate heat treatment was carried out on the above precursors, and the obtained hollow balls have particle size of 5 mm, aperture diameter of 3 mm and wall thickness of 1 mm; the average compressive strength of the hollow balls reaches 15.0 N. Since this method is very simple and effective for preparation of the hollow balls, it may provide a new approach for preparation of high performance heat insulation-porous materials.
Abstract: In order to obtain the porous silicon, amorphous silica was prepared from serpentine by leaching experiment The XRF results shows that the leach residues almost compose of amorphous silica, the content is 92.37%, via magnesiothermic reduction, The XRD results shows the amorphous silica was reduced to porous crystal silicon successfully and The SEM results shows they have similar morphology. One of the most important properties of porous silicon was characterized by PL and with an excitation at 365 nm. an emission centered in the blue region.
Abstract: Zirconia precursor was prepared by an alcohol-aqueous coprecipitation process from raw materials of ZrOC12•8H2O and ammonia ,the zirconia powders were subsequently obtained by calcination of the precursor at 600°C and ball milling. The properties of zirconia powder prepared by alcohol-aqueous method after ball-milling had been researched by BET,XRD,TEM and laser granularity instrument.The results show that by using ball-milling the agglomerate size can be effectively decreased but the primary particle size is hardly affected .The surface area of powder after calcinated can be markedly increased and narrowed size distribution can be gained by ball-milling, but the phase structure of the powder had not been changed.
Abstract: Alumina from sericite phyllite was extracted by the way of limestone self-pulverization sintering technique. The key technical processes, including self-pulverization sintering, clinker leaching reaction and the carbonation decomposition, were investigated systematically. The results showed that the main phases of pulverized clinker consisted of γ-C2S and C12A7, and the self-pulverization rate was 95% . The dissolution rate of Al2O3 clinker could reach 86.7% when the concentration of Na2CO3 solution was 7% and the solid-liquid ratio was 1:3. The Al(OH)3 prepared at 80°C carbonation temperature and pH=10.5 was relatively pure, with hexagonal plate-like crystals. The α-alumina could be acquired by calcination at 1200°C with the content of 99.71% Al2O3 and 0.02% Na2O. This work provided optimal technological parameters for effectively extracting alumina from the sericite and other inexpensive non-bauxite mineral resources with A/S ratio lower than 1.