• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.202.1-202.1
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• 2014

최근 대용량 에너지 저장장치로 사용하고자 하는 리튬-공기전지는 리튬 음극과 액체 전해질 사이의 화학적 불안정성이 문제가 되고 있다. 또한 리튬이온전지는 액체전해질의 사용으로 인해 폭발 등의 안정성 문제가 대두되고 있는 실정이다. 때문에 리튬-공기전지에서 리튬 음극을 액체 전해질로부터 보호할 수 있으며, 리튬이온전지의 액체전해질과 대체하였을 때 전극과도 안정한 고체전해질의 연구가 필요하다. 고체전해질은 구조적으로 crystalline, glassy, 폴리머로 나눌 수 있는데, 이 중 crystalline 구조의 고체전해질은 glassy 및 폴리머 고체전해질에 비해 상온에서 비교적 이온전도도가 높다고 알려져 있다 [1]. 그러나 이온전도도가 높은 황화물 및 질화물 고체전해질은 수분에 민감한 반면 [2,3], 산화물 계열의 물질은 안정할 것으로 예상된다. 본 연구에서는 이온전도도가 높은 산화물인 lithium lanthanum titanate ($Li_{0.5}La_{0.5}TiO_3$, LLTO)를 고체전해질로 선정하여 다양한 환경에서 화학적 안정성에 관해 연구하였다. LLTO와 각종 용액과의 화학적 안정성을 살펴보기 위해 고체전해질을 DI water, 1 M $LiPF_6$ Ethylene Carbonate (EC)-Dimethyl Carbonate (DMC) (50:50 vol.%), 0.57 M LiOH (pH=13), 0.1 M HCl (pH=1)에 immersion하고 무게, 표면형상, 상(phase), 이온전도도 등의 변화를 관찰하였다. 또한 LLTO와 전극간의 반응성을 알아보기 위해 LLTO 분말과 음극물질인 $Li_4Ti_5O_{12}$ 및 양극물질인 $LiCoO_2$ 분말을 혼합한 후 $300^{\circ}C{\sim}700^{\circ}C$의 온도범위에서 열처리하여 반응을 가속화 한 후 상변화 현상을 살펴보았다.

• Journal of the Korean Ceramic Society
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• v.39 no.6
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• pp.582-588
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• 2002

IrO$_2$-RuO$_2$ films were deposited on plasma sprayed TiO$_2$ buffer layer above Ti metal by sol-gel and dip-coating method. Organic vehicle (ethyl cellulose and $\alpha$-terpineol) and glass frit were added to improve adherence of the coatings. Taguchi method and L$_{18}$ (2$^1$$\times$3$^{7}$ ) orthogonal arrays were evalvated in terms of current density to determine the optimal combination of levels of factors that best satisfy the bigger is better quality characteristic. The observed conditions were as fellows: ethyl cellulose (100 cp), drying temperature and time (17$0^{\circ}C$,20 min), heat treatment temperature and time (75$0^{\circ}C$,10 min), the weight ratio of IrO$_2$-RuO/powders to glass frit (99:5), final heat treatment time (120 min) and flow rate of air (5 sccm), respectively. ANOVA analysis suggested that the influence of the factors within $\alpha$= 0.1 was significant with a 90% confidence level.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.25-29
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• 2012

$TiO_2$ nanotubes are prepared from rutile prticles via an alkaline hydrothermal synthesis and the consequent heat treatment at $300{\sim}500^{\circ}C$. The physical and electrochemical properties of the $TiO_2$ nanotubes are characterized for use as a anode material of rechargeable lithium battery. In particular, the microscale dusts as an impurity component occurred in the purification step after the hydrothermal reaction are completely removed to yield $TiO_2$ nanotube with a higher specific surface area and more obvious crystalline phases. As the annealing temperature increases, the specific surface area is slightly decreased due to some aggregation between the isotropically dispersed nanotubes. Highest initial discharge capacity of 250 mAh $g^{-1}$ is achieved for the $TiO_2$ nanotube annealed at $300^{\circ}C$, whereas the $400^{\circ}C$ $TiO_2$ nanotube shows the superior cycle performance and high-rate capability.

• Korean Journal of Materials Research
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• v.9 no.3
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• pp.315-321
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• 1999

Metal matrix composites have been extensively studied because of their excellent characteristics for structural application. $Al_2O_3$ and SiC have been used as a common reinforcement owing to their good mechanical properties. However the manufacturing cost of these ceramic reinforcement is expensive, so the use of the composites has been restricted to special purposes. In this study, we tested the application possibility as a reinforcement of $Al_2O_3$-TiC powder synthesized by SHS(Self-propagating High-temperature Synthesis) process to Al alloy matrix composite. Also, $Al_2O_3$ short fibers were added with the synthesized powders in order to apply to the Al matrix hybrid composites. Squeeze infiltration casting process was used to make the composite with 25vol% of reinforcement. Microstructure and crystal structure were examined by SEM, OM and XRD, also the mechanical properties were studied by the compressive test and wear test.

• Journal of the Korean Magnetics Society
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• v.10 no.5
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• pp.220-224
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• 2000

Ultra-fine $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$ferrite powders have been prepared by the sol-gel method. The crystallographic and magnetic properties of the sample have been investigated by means of x-ray diffraction, Mossbauer spetroscopy and vibrating sample magnetometry. The formation of nano crystallized particles is confirmed. The x-ray diffractions of all samples with various compositions clearly indicate the presence of spinel structure. The Mossbauer spectra could be fitted as the superposition of two sextets due to F $e^{3+}$ A-site and B-site. The IS and QS values nearly constant with substituted Co-Ti contents, whereas $H_{hf}$ of B-site decreases with increasing Co-Ti substitution in $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$. The magnetic behaviour of powders shows that the saturation magnetization and the coercivity decrease with increasing x in $Co_{1+x}$F $e_{2-}$2x/ $Ti_{x}$ $O_4$.$.X>.

• Particle and aerosol research
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• v.5 no.1
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• pp.1-7
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• 2009

Fe- and V-doped titanium dioxide nanoparticles consisting of spherical primary nanoparticles were synthesized from a mixed liquid precursor by using the flame spray pyrolysis. The effects of dopant concentration on the powder properties such as morphology, crystal structure, and light adsorption were analyzed by TEM, XRD, and UV-Vis spectrophotometer, respectively. As the V/Ti molar ratio increased, pure anatase particles were synthesized. On the contrary, rutile phase particles were synthesized as the Fe/Ti ratio increased. Photocatalytic property of as-prepared $TiO_2:Fe,V$ nanoparticles was investigated by measuring the removal efficiency for volatile organic compounds (VOCs) under the irradiation of visible light. After 2 hrs under visible light, the removal efficiencies of benzene, p-xylene, ethylbenzene, and toluene were reached to 21.9%, 21.4%, 19.8% and 17.6% respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.257-257
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• 2007

압전 액츄에이터의 효율적 작동을 위해서는 변위량이 크고 이력이 없으며 응답이 빠르고 온도특성이 좋아야 하는 등의 여러 조건들을 만족시켜야 한다. 따라서 본 실험은 압전 효율은 높이고 압전 손실은 낮추기 위하여 Pb$[(Mn_{1/3}Sb_{2/3})_{0.04}\;Zr_x\;Ti_y]O_3$, 세라믹스를 선정하였으며 Zr/Ti의 변화(x=0.47~0.5, y=0.46~0.49)에 따른 각각의 압전 특성 및 강유전 특성을 조사하였다. 일반적인 산화물 합성법을 이용하여 압전 분말을 제조하였고 EMAS standard(6001)에 근거하여 시편을 제조하였다. XRD 관찰결과 모든 조성에서 perovskite구조의 단일상만을 나타내는 소결체를 얻을 수 있었으며 FE-SEM 관찰결과 $1250^{\circ}C$의 소결시편이 $2-3{\mu}m$의 grain size를 갖는 치밀한 미세구조를 나타내었다. 가장 우수한 압전특성을 나타내는 조성은 Zr/Ti의 비가 0.485/0.475 조성이었으며 그때의 전기기계 결합계수(Kp) 값은 62.5%였고, 기계적 품질계수(Qm) 값은 1004였다.

• Korean Chemical Engineering Research
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• v.51 no.3
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• pp.313-318
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• 2013

In order to investigate the effect of $V_2O_5$ loading of $V_2O_5-WO_3/TiO_2$ catalyst on the NO reduction and the formation of $N_2O$, the experimental study was carried out in a differential reactor using the powder catalyst. The NO reduction and the ammonia oxidation were, respectively, investigated over the catalysts compose of $V_2O_5$ content (1~8 wt%) based on the fixed composition of $WO_3$ (9 wt%) on $TiO_2$ powder. $V_2O_5-WO_3/TiO_2$ catalysts had the NO reduction activity even under the temperature of $200^{\circ}C$. However, the lowest temperature for NO reduction activity more than 99.9% to treat NO concentration of 700 ppm appeared at 340 with very limited temperature window in the case of 1 wt% $V_2O_5$ catalyst. And the temperature shifted to lower one as well as the temperature window was widen as the $V_2O_5$ content of the catalyst increased, and finally reached at the activation temperature ranged $220{\sim}340^{\circ}C$ in the case of 6 wt% $V_2O_5$ catalyst. The catalyst of 8 wt% $V_2O_5$ content presented lower activity than that of 8 wt% $V_2O_5$ content over the full temperature range. NO reduction activity decreased as the $V_2O_5$ content of the catalyst increased above $340^{\circ}C$. The active site for NO reduction over $V_2O_5-WO_3/TiO_2$ catalysts was mainly related with $V_2O_5$ particles sustained as the bare surface with relevant size which should be not so large to stimulate $N_2O$ formation at high temperature over $320^{\circ}C$ according to the ammonia oxidation. Currently, $V_2O_5-WO_3/TiO_2$ catalysts were operated in the temperature ranged $350{\sim}450^{\circ}C$ to treat NOx in the effluent gas of industrial plants. However, in order to save the energy and to reduce the secondary pollutant $N_2O$ in the high temperature process, the using of $V_2O_5-WO_3/TiO_2$ catalyst of content $V_2O_5$ was recommended as the low temperature catalyst which was suitable for low temperature operation ranged $250{\sim}320^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.136.2-136.2
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• 2010

고전도성 세라믹 연결재용 $La_{0.8}Sr_{0.2}Cr_{1-x}Ti_xO_3$ (X=0.1 and 0.2) 연결재 재료의 소결도와 전기전도도에 대해서 연구하였다. 이러한 목적으로 $LaCrO_3$, $La_{0.8}Sr_{0.2}Cr_{0.8}Ti_{0.2}O_3$ (LSCT82), $La_{0.8}Sr_{0.2}Cr_{0.9}Ti_{0.1}O_3$ (LSCT91) 분말들을 공침법을 통해 합성하였으며, 결정구조는 X-ray Diffraction(XRD)를 통해 확인하였다. 소결 특성은 주사 전자현미경을 통해 분석하였고 전기 전도도는 직렬 4-단자 법으로 측정하였다. 상대 밀도 분석으로부터 도핑된 $LaCrO_3$는 $LaCrO_3$보다 더 높은 소결성을 나타내었고, 입자 크기가 작을수록 소결성이 향상하는 것을 확인 할 수 있었다. 다양한 소결온도에서 얻은 LSC, LSTC 시편들의 XRD 결과는 LSC와 LSTC의 소결성이 2차상의 상전이와 밀접한 관련이 있다는 사실을 나타내었다. 다시 말해, LSTC는 $1300^{\circ}$이상 LSC는 $1400^{\circ}C$ 이상에서 2차상이 융해됨으로써 소결성을 현저하게 향상시킨다는 것을 알 수 있었다. 그리고 비슷한 상대밀도를 가진 LSC와 LSTC의 전기 전도도를 비교 측정한 결과, LSTC가 LSC보다 더 높은 전기 전도도를 나타낸다는 것을 알 수 있었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.2
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• pp.292-300
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• 1997

PSZT powders having the particle size of 0.5~5 $\mu\textrm{m}$ with cubic shapes, were prepared by a hydrothermal reaction in the temperature range of 150~$^{\190circ}C$ for a 2 h reaction. Experimental results showed that as the reaction temperature increased, the nucleation and crystal growth were accelerated and the the particle size became larger. However, the particle size became smaller with its narrow distribution as the concentration of a mineralizer (KOH) increased. It was possible to reduce the reaction temperature by increasing mineralizer concentrations. With increase in Zr/Ti ratio, the major crystal phase of synthetic PSZT powders was seen to change from tetragonal phase to rhombohedral phase.