Preparation Of Functional Nano-powders By Novel Ultrasonic Atomization Precipitation Method

In this paper, a novel metod named ultrasonic atomization precipitation method was employed to synthesize the HAP nanopowders and YAG phosphor powders at room temperature and normal atmospheric pressure. The effects of the reaction time, the sintering temperature on the crystal morphology of HAP and homogeneity were investigated and the effect of the different surfactants on the synthesis and characteristic of HAP was discussed. Moreover, the influence of the rare earth doping concentration on the luminescence and excitation spectra of the as-prepared powders was studied. The results and development are as follows:1. At room temperature and normal atmospheric pressure, the hydroxyapatite nano-powders were prepared by ultrasonic atomization precipitation method and with Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄ as raw materials. The obtained powders were homogenous and in size of 30⁴0 nm. The effects of the reaction time, the sintering temperature on the crystal morphology of HAP and homogeneity were investigated. The obtained HAP powders were compared with those synthesized by the conventional ultrasonic method and traditional chemical precipitation method under the same conditions. The results revealed that the method taken in the experiment can shorten reaction time to make HAP nano-powders, enhance the synthetic efficiency effectively and crystallinity of HAP nanopowders in a relatively short reaction period, moreover, the obtained nano-particles were more homogenous.2. In the normal temperature and pressure, nano-hydroxyapatite was synthesized by ultrasonic atomization process with Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄ as the calcium and phosphorus precursors respectively. The effect of four different surfactants on the synthesis and characteristic of hydroxyapatite (HAP) was discussed. The phase of the samples with addition of the same quantity surfactant have no significant change showed in the XRD patterns, therefore, we can consider that the surfactant presence or absence did not to have an affect on crystallization. Scanning electron microphotographs shows that the different additives affect the size and morphology of HAP nanoparticles. The glycine had a positive effect on promoting homogeneity and separation of HAP nanoparticle, and the D-Glucose and TX-10 shows little effect on HAP morphology, whereas Citric acid induced into heavy degree of particle agglomeration. The Author was explored and explained the effect of four different surfactants on the synthesis and characteristic of hydroxyapatite (HAP) from the basic principles of physical chemistry. These results will be provided an effective means of technology to synthesized nano-hydroxyapatite and other ultrafine powders.3. The Y(NO₃)₃, Al(NO₃)₃ and Ce(NO₃)₃ mixed solution was transferred into the NH₄HCO₃ and NH₃·H₂O mixed solution via the ultrasonic atomizer,then the powder was calcined at different temperature. Finally, the homogenous and separate YAG:Ce powders in size of 50-70 nm were obtained. X-ray diffraction, Scanning electron microscopy were used to characterize the phase and morphology of the obtained phosphor powders. The influence of Ce concentration on the luminescence and excitation spectra of the as-prepared powders was studied. The results showed that the ultrasonic atomization and co-precipitation method for preparation of YAG:Ce nano-phosphor have advantages of traditional one in homogeneity and separation of nano-powders. The emission intensity of YAG:Ce reached to the maximum as the Ce-doping concentration to 6-7 mol%. The concentration quenching was obviously higher than that prepared by co-precipitation method, which was only 4.8 mol%. The present studies show that ultrasonic atomization and co-precipitation precipitation method is a promising approach to obtain homogenous YAG:Ce phosphor powders. This method can be employed as a new route for synthesizing analogous phosphor materials.4. Eu-doped Y3Al5O12 (YAG:Eu) phosphor ultrafine powders were synthesized by the Ultrasonic atomization and Co-precipitationmethod using the mixture solution of ammonium hydroxide(NH₃·H₂O) and ammonium hydrogen carbonate(NH₄HCO₃) as precipitant.Fluorescence spectrometer,X-ray diffraction,Scanning electron microscopy were used to characterize the phosphor powders and the influence of Eu concentration on the luminescence of the as-prepared powders was studied.The obtained powders were homogenous and in size of 50⁷0 nm, and were compared with those synthesized by the sol-gel method and other method shows some advantages.When the calcination temperature was increased, the width of the diffraction peaks decreased and the intensity increased.