• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.929-935
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• 2005

In this paper, synthetic conditions of titania nanparticle was investigated to enhance its uniformity of the particle size as a child particle on organic mother particle of liquid powder type electronic paper. The physical properties are very important to improve the uniformity of electrical charging properties Concentration of titania raw material ($C_9H_{19}NO_4Ti$) in the ethanol solvent, pH, and concentration of the solution in the D.I. water were selected as parameters. As a result, ultrafine and well crystallized titania nanoparticle with good uniformity could be synthesized as the concentration of the $C_9H_{19}NO_4Ti$ in the ethanol solvent, pH of the solution, and the amount of the D.I. water were increased. Using the optimized conditions, the titania nanparoticle with uniformly ultrafime size of 10 nm could be synthesized.

• Electrical & Electronic Materials
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• v.10 no.3
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• pp.255-261
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• 1997

In this study, pore-containing barium titanate ceramics were prepared with different porosities and pore sizes, in order to better understand how porosity and pore size affect electrical breakdown of barium titanate ceramics. A granulated barium titanate powder was mixed with three grades of commercial polymer microspheres up to 11wt%. The electrical breakdown test was performed at two different temperatures of 30.deg. C(below Tc) and 150.deg. C(above Tc) for samples immersed in a silicon oil bath using a 60kV de power supply. Electrical breakdown strength of pore containing barium titanate ceramics with porosity lower than 10% decreased as pore size and porosity increased. However, above the 10% porosity region, electrical breakdown strength decreased as the pore connectivity increased. From the experimental results, an optimum electrical breakdown model is proposed in an attempt to explain the effect of pores.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.6
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• pp.550-553
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• 2005

[ $Pb(Zr_{0.2}Ti_{0.8})O_3$ ] powders, prepared by the sol-gel method, were mixed with an organic vehicle and the PZT thick films were fabricated by the screen-printing techniques on Pt/alumina substrates. The structural and dielectric properties were examined as a function of sintering temperature. The particle size distribution of the powder is bimodal with the mean particle size of about $1.2\;{\mu}m$. The average grain size of the PZT thick films sintered above $1000^{\circ}C$ was about $3.1\;{\mu}m$ and the thickness of the specimens was approximately $41\;{\mu}m$. The relative dielectric constant and dielectric loss of the thick films sintered at $1050^{\circ}C$ were 337 and $1.24\%$, respectively.

• Journal of Surface Science and Engineering
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• v.29 no.5
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• pp.330-337
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• 1996

A rf reactive sputter deposition technique was adopted to deposit ferroelectric lead zirconate titanate (PZT) thin films with high rate from a ZrTi alloy target combined with PbO pellets. Deposition characterisitics including the effects of PbO are ratio were discussed. A new deposition mode called the quasi-metallic mode was observed. Perovskite PZT films were prepared at a growth temperature as low as$ 450^{\circ}C$. However, because the target structure is unstable, weproposed a mixture target consisted of Zr, Ti and PbO. Fundamental experiments were investigated using the powder target. Perovskite PZT film could be obtained at $450^{\circ}C$ with better electrical properties also.

• Journal of Surface Science and Engineering
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• v.39 no.4
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• pp.190-197
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• 2006

The effects of blasting and acidic treatment on the corrosion characteristics of dental implant fabricated with Cp-Ti and Ti-6Al-4V alloy have been researched by using electrochemical methods. The fabricated implants were cleaned and sandblasted by $Al_2O_3$ powder and then acidic treatment was carried out in nitric acid solution. The surface morphology were observed using scanning electron microscope. The corrosion behaviors were investigated using potentiosat and EIS in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The potentio-dynamic test in 0.9% NaCl indicated that the corrosion potential of blasting and acidic treated implant was lower than that of non treated implant, but current density was higher than that of non treated implant. From the cyclic potentiodynamic test results of Ti implant, the passivation current density of blasting and acidic treated implant slightly higher than that of non treated implant. From A.C. impedance test results in 0.9% NaCl solution, polarization resistance($R_p$) value of blasting and acidic treated implant was lower than that of non treated implant. In case of blasting and acidic treated implant surface, the pits were observed in valley and crest of implant surface.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.669-675
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• 2010

One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, $TiCl_4{\cdot}YCl_3$ solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical $TiO_2$ precursor. Then, the $Li_4Ti_5O_{12}$ was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical $TiO_2$ precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which $Li_4Ti_5O_{12}$ spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at $50^{\circ}C$ for 30 minutes and at $850^{\circ}C$ for 6 hours heat treatment time were optimized. $Li_4Ti_5O_{12}$ was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.165-170
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• 2004

MLCC의 주재료인 $BaTiO_3$는 금속전극의 산화를 방지하기 위해 환원분위기에서 소결하는데 이는 비화학양론적 조성 및 전기적 성질, 결함 그리고 상의 변화를 가져온다. 본 연구에서는 상의 변화를 다양한 온도 범위에서 BaO 또는 $TiO_2$를 첨가시킨 $BaTiO_3$ powder을 가지고 급냉시킨 후 이를 X-선 회절 분석을 통하여 이들의 이차상 형성 여부 등을 조사하였다. $1320^{\circ}C$에서는 $TiO_2$의 고용도가 BaO의 고용도에 비해 상당히 큰 값을 가짐을 알 수 있었다. 이런 결과를 바탕으로 Ba/Ti 비, 산소분압 및 온도에 따른 $BaTiO_3$의 전기전도도 거동에 의하면, 고용범위내에서 BaO 첨가량이 증가할수록 전기전도도의 최소점은 낮은 산소분압쪽으로 이동함을 관찰하였으며 이는 $Ti^{4+}$빈자리에 따른 산소빈자리가 형성되는 결함 모델로 설명되어진다.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.301-307
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• 1997

Monodisperse, spherical $SiO_2/TiO_2$ composite fine powders were prepared by modified Sol-Gel process which $TiO_2$ fine Powders was used as a seed particles for condensation of TEOS (Tetraethyl Orthosilicate). The reaction was carried out under $N_2$ atmosphere at ambient temperature using $NH_3$ as a catalyst. Ethanol was used as a solvent. Drying process was carried out with vacuum trap which cooled by liquid $N_2$. The reaction variables were the concentration of TEOS, the concentration of ammonia, the size of $TiO_2$ seed and molar ratio of $SiO_2/TiO_2$. The optimum condition for the preparation of $SiO_2/TiO_2$ composite fine powders without agglomeration was [TEOS]=0.3M, [$NH_3$]=0.7M, size of $SiO_2/TiO_2$ seed = 200~300nm.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.213-216
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• 1991

In this study, PZT powder was synthesized by coprecipitation method us ing $Pb(NO_3)2$, $ZrOCl_2{\cdot}8H_2O$ and $TiCl_4$ as starting raw materials. Homogeneous and fine-grained PZT powder was obtained by the coprecipitation method. PZT powder was characterized by DTA, SEM and XRD analysis. The XRD peaks were observed at $600(^{\circ}C)$ and over.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1078-1084
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• 2002

The formation temperature for the perovskite lead zirconate titanate [Pb(Zr,Ti)O3, PZT] derived from sol-gel route was lowered by more than $100^{\circ}C$ with the addition of crystallographically suitable seed particles, such as barium titanat e (BT) or PZT. We investigated the effect of seeding on the crystallization of perovskite phase and in the microstructure of the sol-gel derived PZT powder by varying the concentration, size and chemical species of seed particles. The phase transition as a function of temperature was monitored by DTA, XRD, and Raman spectroscopy, and the interface between the seed particle and grown PZT layer was analyzed by SEM and high resolution TEM techniques. It was found that both the heterogeneous and homogeneous nucleation contributes competitively in the formation of perovskite PZT grains.