• Korean Journal of Materials Research
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• v.11 no.11
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• pp.953-959
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• 2001

Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution of ammonium $metatungstate(NH_4)_6(H_2W_{12}O_{40}){\cdot}4H_2O,\; AMT)$ and cobalt nitrate $hexahydrate(Co(NO_3)_2{\cdot}6H_2O)$. The thermal decomposition process of spray dried W-Co salt powders was studied by TG, XRD, SEM, TEM and FT-IR. Spray dried W-Co salt powders were calcined for 1 hour in the temperature from$ 350^{\circ}C$ to $800^{\circ}C$ in atmosphere of air. At the temperatures over $600^{\circ}C$, spherical $CoWO_4/WO_3$ composite oxide powders were obtained. The primary particle size of W/Co composite oxide powders increased with increasing thermal decomposition temperature due to the particle growth. The observed crystallite size by TEM was in the range of 60nm and that of $CoWO_4$ calculated by Scherrer's formula at $800^{\circ}C$ was smaller than 55nm. The crystallite site was identified by XRD and TEM.

• Clean Technology
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• v.19 no.3
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• pp.342-346
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• 2013

Several types of mesoporous silica-alumina adsorbents with varied $SiO_2/Al_2O_3$ ratios were prepared by spray pyrolysis and were used for the purification of the anticancer agent paclitaxel. When $S_{0.5}A_{0.5}$ (Silica/Alumina molar ratio = 0.5/0.5) was used, the highest purity (~27%) and yield (~63%) of paclitaxel were obtained from adsorbent treatment and hexane precipitation. Removal of impurities was confirmed by TGA analysis of the organic substances that were adsorbed to the adsorbent.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.385-391
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• 2014

A control system for ultrasonic spray pyrolysis deposition was developed that can coat a large size glass panel with a transparent conductive oxide. It consists of several ultrasonic atomizer devices to cover a large area and a host computer for individually controlling the devices. The sub-controller in an ultrasonic atomizer device can adjust the flow rate of the atomized conductive oxide gas by setting the flow rate of the solution and regulating the level of the solution in the tank. To construct a feedback control loop for level regulation, a level sensor that utilized an infrared distance sensor and an electric circuit for adjusting the ultrasonic oscillator were developed. The host program was also developed, which can monitor and control the sub-controllers. A proportional-integral controller was developed for a simplified model, and its operation was verified through an experiment.

• KSBB Journal
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• v.28 no.3
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• pp.208-212
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• 2013

Four types of mesoporous spherical silica adsorbents with different physical properties were prepared by spray pyrolysis and were used for the purification of the anticancer agent paclitaxel from plant cell cultures. Pore size had a greater effect on the removal of plant-derived impurities during the pre-purification of paclitaxel compared with surface area and pore volume. An appropriate pore diameter (~9.07 nm) was required to achieve the highest purity (~46.1%) and yield (~82.3%) of paclitaxel. These results were confirmed by HPLC analysis of the absorbent after treatment and Thermogravimetric analysis of the organic substances bonded to the adsorbent.

• Progress in Superconductivity
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• v.12 no.1
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• pp.68-73
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• 2010

Y123 films have been deposited on $LaAlO_3$ (100) single-crystal and IBAD substrates by spray pyrolysis method using nitrate precursors. Ultrasonic atomization was adopted to decrease the droplet size, spraying angle and its moving velocity toward substrate for introducing the preheating tube furnace in appropriate location. A small preheating tube furnace was installed between spraying nozzle and substrate for fast drying and enhanced decomposition of precursors. C-axis oriented films were obtained on both LAO and IBAD substrates at deposition temperature of around $710{\sim}750^{\circ}C$ and working pressures of 10~15 torr. Thick c-axis epitaxial film with the thickness of $0.3{\sim}0.6\;{\mu}m$ was obtained on LAO single-crystal by 10 min deposition. But the XRD results of the film deposited on IBAD template at same deposition condition showed that the buffer layers of the IBAD metal substrate was affected by long residence of metal substrate at high temperature for YBCO deposition.

• Journal of Powder Materials
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• v.23 no.4
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• pp.307-310
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• 2016

$TiOF_2$, which has remarkable electrochemical and optical properties, is used in various applications such as Li-ion batteries, electrochemical displays, and photocatalysts. In addition, it is possible to utilize the template which is allowed to synthesize fluorine doped $TiO_2$ powders with hollow or faceted structures. However, common synthesis methods of $TiOF_2$ powders have some disadvantages such as the use of expensive and harmful precursors and batchtype processes with a limited production scale. In this study, we report a synthetic route for preparing $TiOF_2$ powders by using an inexpensive and harmless precursor and a continuous ultrasonic spray pyrolysis process under a controlled atmosphere to address the aforementioned problems. The synthesized powder has an average size of $1{\mu}m$, a spherical shape, a pure $TiOF_2$ phase, and exhibits a band-gap energy of 3.2 eV.

• Journal of Powder Materials
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• v.24 no.4
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• pp.326-331
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• 2017

The structural formation of inorganic nanoparticles dispersed in polymer matrices is a key technology for producing advanced nanocomposites with a unique combination of optical, electrical, and mechanical properties. Barium titanate ($BaTiO_3$) nanoparticles are attractive for increasing the refractive index and dielectric constant of polymer nanocomposites. Current synthesis processes for $BaTiO_3$ nanoparticles require expensive precursors or organic solvents, complicated steps, and long reaction times. In this study, we demonstrate a simple and continuous approach for synthesizing $BaTiO_3$ nanoparticles based on a salt-assisted ultrasonic spray pyrolysis method. This process allows the synthesis of $BaTiO_3$ nanoparticles with diameters of 20-50 nm and a highly crystalline tetragonal structure. The optical properties and photocatalytic activities of the nanoparticles show that they are suitable for use as fillers in various nanocomposites.

• Journal of Powder Materials
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• v.17 no.3
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• pp.209-215
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• 2010

Mesoporous alumina particles were prepared by spray pyrolysis using cetyltrimethyl-ammonium bromide (CTAB) as a structure directing agent and the effect of Al precursor types on the texture properties was studied using $N_2$ adsorption isotherms, small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The surface area and the microstructure of alumina particles were significantly influenced by the Al precursor type. The largest BET surface area was obtained when Al chloride was used, whereas alumina particles prepared from Al acetate had the largest pore volume. According to small-angle X-ray scattering (SAXS) analysis, the alumina powders prepared using nitrate and acetate precursors had a clear single SAXS peak around $2{\theta}=1.0{\sim}1.5^{\circ}$, indicating that regular mesopores with sponge-like structure were produced. On the basis of TEM, SAXS, and $N_2$ isotherm results, the chloride precursor was most profitable to obtain the largest surface area ($265\;m^2/g$), whereas, the nitrate precursor is useful for the preparation of non-hollow mesoporous alumina with regular pore size, maintaining high surface area (${\sim}233\;m^2/g$).

• Journal of Powder Materials
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• v.19 no.3
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• pp.220-225
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• 2012

YAG:Ce yellow phosphor particles were synthesized by spray pyrolysis with changing the solution properties and their luminous properties, crystal structure, and morphological changes were studied by using PL measurement, XRD, and SEM analysis. It was clear that the solution properties significantly affected the crystal phase, crystallite size, the PL intensity, and the morphology of YAG:Ce particles. At low calcination temperature, the addition of urea only to the spray solution was helpful to form a pure YAG phase without any impurity phases, as the result, the highest luminescence intensity was achieved at the calcination temperature of $900^{\circ}C$. When the calcination temperatures were larger than $1300^{\circ}C$, however, the YAG particles prepared without any additive showed the highest luminescent intensity. Regardless of the solution conditions, the emission intensity of YAG:Ce particles prepared by spray pyrolysis showed a linear relation with the crystallite size. In terms of the morphology of YAG:Ce particles, the addition of both DCCA and $NH_4OH$ to the spray solution was effective to prepare a spherical and dense structured YAG particles.

• Journal of Powder Materials
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• v.25 no.6
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• pp.482-486
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• 2018

Despite numerous advances in the preparation and use of GaN, and many leading-edge applications in lighting technologies, the preparation of high-quality GaN powder remains a challenge. Ammonolytic preparations of polycrystalline GaN have been studied using various precursors, but all were time-consuming and required high temperatures. In this study, an efficient and low-temperature method to synthesize high-purity hexagonal GaN powder is developed using sub-micron $Ga_2O_3$ powder as a starting material. The sub-micron $Ga_2O_3$ powder was prepared by an ultrasonic spray pyrolysis process. The GaN powder is synthesized from the sub-micron $Ga_2O_3$ powder through a nitridation treatment in an $NH_3$ flow at $800^{\circ}C$. The characteristics of the synthesized powder are systematically examined by X-ray diffraction, scanning and transmission electron microscopy, and UV-vis spectrophotometer.