• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 한국결정성장학회 1996년도 제11차 KACG 학술발표회 Crystalline Particle Symposium (CPS)
• /
• pp.185-217
• /
• 1996

Pb(Mg1/3Nb2/3)O3은 높은 유전율과 전기저항 및 유전율의 온도변화율이 적은 Pb계 relaxor의 대표적인 재료로서 적층 세라믹 콘덴서 재료에의 응용이 크게 기대되고 있다. 그러나 산화물 분말을 이용하는 일반적인 세라믹스 합성방법으로는 Pb(Mg1/3Nb2/3)O3의 단일상의 합성이 어렵고, 합성과정에서 저유전율상인 pyrochlore상이 합성이 어렵고, 합성과정에서 저유전율상인 pyrochlore상이 공존하여 Pb(Mg1/3Nb2/3)O3의 전기적 특성을 저하시킨다. 본연구에서는 용액을 이용하여 Pb(Mg1/3Nb2/3)O3의 단일상을 합성하고자 하였다. 출발물질로는 값싼 금속염인 Niobium Oxalate, magnesium Nitrate 및 Lead Nitrate를 선정하고 증류수에 용해하여 혼합용액을 제좋고, 합성방법으로는 초음파 분무 열분해법과 에멀젼법을 이용하였다. 초음파 분무 열분해법에서는 75$0^{\circ}C$에서 합성한 분말을 다시 75$0^{\circ}C$에서 하소하여 Pb(Mg1/3Nb2/3)O3 단일상을 합성할 수 있었으며, 에멀젼법에서는 80$0^{\circ}C$에서 Pb(Mg1/3Nb2/3)O3 단일상을 합성할 수 있었다.

• Journal of the Korean Vacuum Society
• /
• 제19권1호
• /
• pp.66-71
• /
• 2010

Spherical shape $Zn_2SiO_4:Mn$ phosphor particles with the mean particle size from submicron to micron sizes were prepared by ultrasonic spray pyrolysis method. A droplet separator was introduced to control the size distribution of the phosphor particles with spherical shape. The $Zn_2SiO_4:Mn$ phosphor particles with 2 mol% doping concentration of manganese have decay time and have photoluminescence intensities comparable with those of the latest commercial product prepared by the solid state reaction method. The size of the phosphor particles was decreased from 1 to 0.2 micrometers as the inorganic salt solution concentration was changed from 0 to 5 M. The phosphor particles prepared from the solutions above 0.5 M have photoluminescence intensities comparable with that of the latest commercial product.

• Journal of the Korean Ceramic Society
• /
• 제32권5호
• /
• pp.575-581
• /
• 1995

Zr0.94Y0.06O1.97 powder was synthesized by the ultrasonic spray pyrolysis with various concentrations of starting solution and the influence of powder characteristics on sintering behavior was investigated. Powders prepared at 75$0^{\circ}C$ were characterized as narrowly distributed submicron spherical particles, which were crystalline, nonagglomerated, and compositionally homogeneous. The changes in concentration from 0.01 to 01. mol/ι increased mean particle size from 0.24 to 0.38${\mu}{\textrm}{m}$ and decreased the specific surface area from 14.2 to 2.9$m^2$/g. The relative density of the specimen from the powders, prepared with the solution concentration of 0.01 mol/ι, was 98% after sintering for 2 hr at 1,45$0^{\circ}C$ and the monoclinic phase was observed after sintering at 1,55$0^{\circ}C$. As the concentration of starting solution was increased, the formation temperature of monoclinic phase was lowered.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• 제1권2호
• /
• pp.46-58
• /
• 1991

The synthesized ZnO powder was prepared by spray pyrolysis method using ultrasonic vibrator. The starting solutons were the aqueous solution of $Zn(NO_3)_2\cdot6H_2O$. The concentration was prepared 1M, O.5M, O.25M, and O.lM. The Nz carrier gas was 2.3cm$\cdot{sec}^{-1}$. The prepared powder from the $Zn(NO_3)_2{\cdot}6H_2O$ aqueous solution was Zine oxide with hexagonal structure. The shape of prepared powder was fine size, narrow size distribution, agglomerate-free, nearly sphere particle. Also, the particle size was about $ 0.28-0.61\mum$.

• Journal of the Korean Chemical Society
• /
• 제44권6호
• /
• pp.592-599
• /
• 2000

The fine particles of binary ceramic composite of titania-partially-stabilized zirconia(TPSZ) were synthesized by ultrasonic spray pyrolysis at the various temperatures, compositions and concentrations and the effects of process factors for synthesis on the characteristics of fine particles were discussed. The starting salt solutions were prepared to have the ionic concentrations of 0.025~0.1 M aqueous solutions. The fine particles were prepared to have the compositions of 90~97.5 wt% of $ZrO_2$ and 2.5~10 wt% of $TiO_2$. The temperatures for particle synthesis were regulated to be 400~550$^{\circ}C$ as a drying zone, 800~1100$^{\circ}C$ as a pyrolysis zone. The produced fine particles were collected by a wet process and analyzed to investigate characteristic properties after being dried. The compositions of ceramic fine particles were determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy(ICP-AES) technique and phases, morphologies and particle sizes of those were investigated by Raman Spectroscopy, X-ray diffraction(XRD), Scanning Electron Microscopy(SEM), Transmission Electron Microscopy(TEM) and Particle Size Analyzer(PSA) techniques.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• 제4권2호
• /
• pp.178-189
• /
• 1994

Fine $BaTiO_3$ powder was synthesized from the various starting solution with 0.05 M by ultrasonic spray pyrolysis method. The conditions of synthesis were fixed on flow rate was 0.5 cm/sec, low temperature furnace was $300^{\circ}C$, and high temperatures furnace was $700^{\circ}C$. The formation procedure was investigated directly by SEM with the collected particle from the each reaction step. Also, the trace of particle in reaction tube was researched theoretically. Fine $BaTiO_3$ was synthesized only in the case of nitrate aqueous solution. The synthesized $BaTiO_3$ powder was porous and spherical which was consist of primary particle at the size of 19.1 nm. The formation procedure was as follows : the particle size decreased in drying step and then increased in initial thermal decomposition step. Finally, particle size was decreased to $0.42 {mu}m$. The trace of particle in reaction tube was also theoretically simulated and discussed.

• Journal of the Korean Ceramic Society
• /
• 제35권6호
• /
• pp.529-534
• /
• 1998

Agglomeration-free indium oxide particles were produced by ultrasonic pyrolysis of indium nitrate(3 hy-drate) solution. Th mean size of particles was increased from 3 $\mu\textrm{m}$ to 11$\mu\textrm{m}$ with increasing intial con-centrations of indium nitrate from 0.05mol% to 4.83 mol% When the input rate of indium nitrate solution was increased from 0.1 cm3/min to 0.8cm3/min the size of particles remained same and only the pro-duction rate of particles was increased. At 300$^{\circ}C$ the particles were white color with low crystallinity. But the color turned into yellow with increasing reaction temperature. The change of particle size was not ob-served with increasing temperatuer up to 700$^{\circ}C$ IR spectrum and TGA analysis confirmed that the purity of indium oxide was increased with temperature of reaction.

• Journal of Sensor Science and Technology
• /
• 제13권1호
• /
• pp.66-71
• /
• 2004

Pt-doped zinc oxide (ZnO:Pt) films were deposited by ultrasonic spray pyrolysis. Resistivity variation with Pt concentration was measured. The Pt distribution in ZnO:Pt films was studied through Auger Electron Spectroscopy (AES). The ZnO:Pt films were annealed in the ambient of air, water vapor and ozone, respectively. The variation in crystallographic properties and surface morphologies with respect to the annealing condition was observed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The resistivity variation of the films with the annealing condition was measured. Finally, Atomic Force Microscopy (AFM) measurements were carried out to study the effects of the annealing on the roughness of ZnO:Pt films.

• Membrane Journal
• /
• 제15권4호
• /
• pp.330-337
• /
• 2005

Water selective silica membranes were prepared fur use as membrane reactor for synthesis of dimethyl ether (DME) by methanol dehydration. Silica membranes formed on a Porous SUS tube by ultrasonic spray Pyrolysis (USP) and chemical vapor deposition (CVD) using tetraethoxysilane (TEOS) as precursor. The CVD-derived membranes formed higher level of trade-off line between water permeance and water/methanol selectivity than that of the USP-derived membranes. The membrane reactor possessing water permeance of $1.2\times10^{-7}\;mol\;{\cdot}\;m^{-2}\;{\cdot}\;S^{-1}\;{\cdot}\;Pa^{-1}$ and water/methanol selectivity of 10 exhibited increase in methanol conversion of about $20\%$ comparing to conventional reactor system. These findings led us to conclude that the dehydration membrane reactor simultaneously separating the water vapour produced in the reaction zone was effective in increasing the reaction conversion.

• Journal of Powder Materials
• /
• 제26권3호
• /
• pp.237-242
• /
• 2019

In this study, ultrasonic spray pyrolysis combined with salt-assisted decomposition, a process that adds sodium nitrate ($NaNO_3$) into a titanium precursor solution, is used to synthesize nanosized titanium dioxide ($TiO_2$) particles. The added $NaNO_3$ prevents the agglomeration of the primary nanoparticles in the pyrolysis process. The nanoparticles are obtained after a washing process, removing $NaNO_3$ and NaF from the secondary particles, which consist of the salts and $TiO_2$ nanoparticles. The effects of pyrolysis temperature on the size, crystallographic characteristics, and bandgap energy of the synthesized nanoparticles are systematically investigated. The synthesized $TiO_2$ nanoparticles have a size of approximately 2-10 nm a bandgap energy of 3.1-3.25 eV, depending on the synthetic temperature. These differences in properties affect the photocatalytic activities of the synthesized $TiO_2$ nanoparticles.