• Progress in Superconductivity
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• v.13 no.2
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• pp.127-132
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• 2011

Many research groups have been manufacturing coated conductor by various processes such as PLD, MOD, and MOCVD, but the methods with production cost suitable for wide and massive application of coated conductor did not develop yet. Spray pyrolysis method adopting ultrasonic atomization was tried as one of the possible option. GdBCO precursor films have been deposited on IBAD substrate by spray pyrolysis method at low temperature and converted to GdBCO by post heat treatment. Ultrasonic atomization was used to generate fine droplets from precursor solution of Gd, Ba, and Cu nitrate dissolved in water. Primary GdBCO films were deposited at $500^{\circ}C$ and oxygen partial pressure of 1 torr. After that, the films were converted at various temperatures and low oxygen partial pressures. C-Axis oriented films were obtained IBAD substrates at conversion temperature of around $870^{\circ}C$ and oxygen partial pressures of 500 mtorr ~ 1 torr in a vacuum. Thick c-axis epitaxial film with the thickness of 0.4 ~ 0.5 ${\mu}m$ was obtained on IBAD substrate. C-axis epitaxial GdBCO films were successfully prepared by ex-situ methods using nitrate precursors on IBAD metal substrate. Converted GdBCO films have very dense microstructures with good grain connectivity. EDS composition analysis of the film showed a number of Cu-rich phase in surface. The precursor solution having high copper concent with the composition of Gd : Ba : Cu = 1 : 2 : 4 showed the better grain connectivity and electrical conductivity.

• Korean Journal of Materials Research
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• v.13 no.3
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• pp.180-184
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• 2003

Ce-doped $Y_2$SiO$_{5}$ phosphor particles of spherical morphology, fine size, high crystallinity and high photoluminescence (PL) intensity were prepared by spray pyrolysis. When nitrate precursor solution is adopted, hollow particles were formed by uneven drying rate between surface and inside of droplet. Citric acid and ethylene glycol were introduced as polymeric precursor to control the morphology of particles. When polymeric solution is adopted, polymeric chain is formed by the esterification reaction between carboxyl and hydroxy groups of citric acid and ethylene glycol, and considered as controlling the drying characteristics of droplet. $Y_2$$SiO_{5}$ :Ce phosphor particles prepared from polymeric precursor solution were spherical, filled, fine size and not agglomerate before and after post heat treatment. The optimum doping concentration of cerium was 0.5 mol% of overall solution concentration. The optimum amount of TBOS of high PL intensity and pure crystallinity of X2-type $Y_2$$SiO _{5}$ was 105% of stoichiometric amount. The PL intensity of $Y_2$X$/_{5}$ :Ce phosphor particles prepared using the polymeric precursor solution was 164% of that of the nitrate precursor solution due to homogeneous composition and good morphology.y.

• Carbon letters
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• v.8 no.2
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• pp.120-126
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• 2007

The effect of cobalt precursor on the structure of Co supported multi-walled carbon nanotubes (MWCNTs) were studied by using X-ray photoelectron spectroscopy (XPS). MWCNTs were treated with a mixture of nitric and sulfuric acids and decorated with cobalt and/or cobalt oxides via aqueous impregnation solutions of cobalt nitrate or cobalt acetate followed by reduction in hydrogen. XPS was mainly used to investigate the phase of cobalt on MWCNTs after reduction with $H_2$ flow at $400^{\circ}C$ for 2 h. Higher cobalt-nanoparticle dispersion was found in the MWCNTS prepared via cobalt nitrate decomposition. A typical XPS spectrum of Co 2p showed the peaks at binding energy (BE) values equal to 781 and 797 eV, respectively. It is found that cobalt nitrate supported MWCNTs is more dispersive and have catalytic activity than that of cobalt acetate supported MWCNTs at same preparation condition such as concentration of precursor solution and reduction environment.

• Bulletin of the Korean Chemical Society
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• v.31 no.1
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• pp.47-51
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• 2010

A powder, containing 80 percent of blue cobalt aluminate $(CoAl_2O_4)$ crystallites, was synthesized at $210 ^{\circ}C$ using a (metal nitrate-malonic acid-ammonium hydroxide-ammonium nitrate) system. The optimal amount of concentrated ammonia water and initial decomposition temperature were determined for the blue $CoAl_2O_4$ crystallites preparation. Three $CoAl_2O_4$ precursor pastes, corresponding to the various amounts of concentrated ammonia water, were prepared by evaporating the initial solutions in an electric furnace fixed at $80 ^{\circ}C$ under a vacuum of 25 torr. The initial solution was used to dissolve the starting materials. The powder with the maximum content (80%) of blue $CoAl_2O_4$ crystallites was prepared when the prepared precursor was decomposed at $210 ^{\circ}C$. The blue $CoAl_2O_4$ crystallite content in the prepared sample decreased with increasing initial decomposition temperature. For 0.2 mole of the $Al^{3+}$ ion, the chemical compositions of the precursor corresponded to molar ratios of 0.4, 1.40, 2.56 and 2.00 for the $Co^{2+}$ ion, malonic acid, ammonia and ammonium nitrate per mole of the $Al^{3+}$ ion, respectively. The blue $CoAl_2O_4$ crystallite content in the sample decreased with the amount of ammonia deviated from the optimal value. The characteristics of the powders were examined using X-ray diffraction, optical microscopy, Fourier transformation infrared spectroscopy and the Brunauer-Emmett-Teller technique.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.60-60
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• 2008

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.221-227
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• 1989

To investigate the development and densification YBa2Cu3O7-x(1-2-3) superconducting phase, the 1-2-3 phase powders have been prepared by citrate and nitrate processes with changing calcination temperature. Nearly pure 1-2-3 phase peaks have been obtained by calcining the precursor in air at 90$0^{\circ}C$ for 2.5h in citrate process but at 95$0^{\circ}C$ for 2.5h in nitrate process. The sintering density of citrate derived sample calcined at 80$0^{\circ}C$ has been about 4% higher than that calcined at 90$0^{\circ}C$, although the compacting density has been lower at 80$0^{\circ}C$ calcination. This can be explained that the 1-2-3 phase particles formed at 80$0^{\circ}C$ have reactive sub-micron size which has good sinterbililty.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.50-55
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• 2008

AI-doped ZnO(AZO) thin films have been fabricated on glass substrate by sol-gel method, and the effect of Al precursors and post-annealing temperature on the characteristics of AZO thin films was investigated. The sol was prepared with zinc acetate, EtOH, MEA and Al precursors. In order to dope Al in ZnO, two types of aluminum nitrate and aluminum chloride were used as Al precursor. Zinc concentration was 0.5 mol/l and the content of Al precursor was 1 at% of Zn in the sol. The sol was spin-coated on glass substrate, and the coated films were annealed at 550ue for 2 hand were post-annealed at temperature ranges of $300{\sim}500^{\circ}C$ for 2 h in reducing atmosphere ($N_2/H_2$= 9/1). Structural, electrical and optical propertis of the fabricated AZO thin films were analyzed by XRD, FE-SEM, AFM, hall effect measurement system and UV-visible spectroscopy. Optical and electrical properties of AZO thin films prepared with aluminum nitrate as Al precursor were better than those of films prepared with aluminum chloride. The electrical resistivity and the optical transmittance of films decreased with increasing post-annealing temperatures. The minimum electrical resistivity of $2{\times}10^{-3}$ and the maximum optical transmittance of 91% were obtained for the AZO thin films post-annealed at $550^{\circ}C\;and\;300^{\circ}C$, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.5
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• pp.175-180
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• 2016

ZnO nanoparticles were synthesized by aqueous preparation routes of a precipitation and a hydrothermal process. In the processes, the powders were formed by mixing aqueous solutions of Zn-nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) with NaOH aqueous solution under controlled reaction conditions such as Zn precursor concentration, reaction pH and temperature. Single ZnO phase has been obtained under low Zn precursor concentration, high reaction pH and high temperature. The synthesized particles exhibited flakes (plates), multipods or rods morphologies and the crystallite sizes and shapes would be efficiently controllable by changing the processing parameters. The hydrothermal method showed advantageous features over the precipitation process, allowing the precipitates of single ZnO phase with higher crystallinity at relatively low temperatures below $100^{\circ}C$ under a wider pH range for the Zn precursor concentration of 0.1~1 M.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.3
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• pp.277-284
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• 2005

Catalytic oxidation of toluene in low concentrations was investigated over various supports. As the manganese oxides loading was increased, the conversion of toluene increased at a lower temperature. The 18.2 $wt\%$ $Mn/\gamma-Al_2O_3$ appeared to be the most active catalyst. Among the supports, $\gamma-Al_2O_3$ was more active than $TiO_2$ and $SiO_2$. Manganese oxide catalysts prepared from manganese nitrate precursor were better for complete oxidation of toluene than those prepared from manganese sulfate and chloride precursor because sulfate from manganese sulfate and chloride from chloride manganese remained even after the calcination by XRD (X-Ray Diffraction) analyses.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1080-1083
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• 2001

Ultrafine NiO/YSZ composite powders were prepared by using a glycine nitrate process for anode material of solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ composite powders were examined with controlling pH of a precursor solution and the content of glycine. The characteristics of synthesized composite powders were examined with X-ray diffractometer, a BET method with N$_2$absorption, scanning and transmission electron microscopy. The strongly acid precursor solution increased the specific surface area of the synthesized composite powders. This is suggested to be caused by the increased binding of metal ions and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of NH$_3$$\^$+/. After sintering and reducing treatment of NiO/YSZ composite powders synthesized by GNP, the Ni/YSZ pellet showed ideal micro-structure very fine Ni parties of 3-5${\mu}$m were distributed uniformly and fine pores around Ni metal particles were formed, thes, leading to an increase of the triple phase boundary among gas Ni and YSZ.