• Korean Journal of Materials Research
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• v.9 no.9
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• pp.900-904
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• 1999

The effects of Tio$_2$addition on the microstructural evolution and mechanical properties of alumina ceramics were studied. Bulk density decreased with an increase of the amount of TiO$_2$. Apparent porosity decreased with an increase of the amount of TiO$_2$ up to 7wt%. But beyond 9wt% of TiO$_2$powders, apparent porosity increased. In the compression test, the modulus increased with an increase of the amount of TiO$_2$addition. In the three point bending test, the stress at yield decreased with an increase of the amount of TiO$_2$ addition. The addition. The addition of TiO$_2$ promoted the grain growth of alumina ceramics.

• Advances in materials Research
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• v.9 no.2
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• pp.99-107
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• 2020

Reinforced aluminum alloy base composites have become increasingly popular for engineering applications, since they usually possess several desirable properties. Recently, Warm Accumulative Roll Bonding (WARB) process has been used as a new novel process to fabricate particle reinforced metal matrix composites. In the present study, TiO₂ particles are used as reinforcement in aluminum metal matrix composites fabricated through warm accumulative roll bonding process. Firstly, the raw aluminum alloy 1060 strips with TiO₂ as reinforcement particle were roll bonded to four accumulative rolling cycles by preheating for 5 min at 300℃before each cycle. The mechanical and bonding properties of composites have been studied versus different volume contents of TiO₂ particles by tensile test, peeling test and vickers micro-hardness test. Moreover, the fracture surface and peeling surface of samples after the tensile test and peeling test have been studied versus different amount of TiO₂ volume contents by scanning electron microscopy. The results indicated that the strength and the average vickers micro-hardness of composites improved by increasing the volume content of TiO₂ particles and the amount of their elongation and bonding strength decreased significantly.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1240_1241
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• 2009

In this paper, sol-gel-spin coated $Pb(ZrTi)O_3$ thin film with $ZrO_2$ buffer-layer and $PbTiO_3$ seed-layer was investigated for vibration MEMS energy harvester to scavenge power from ambient vibration via d33 piezoelectric mode. Piezoelectric thin film deposition techniques on insulating layer is the important key for $d_{33}$ mode of piezoelectric vibration energy harvester. $ZrO_2$ buff-layer was utilized as an insulating layer. $PbTIO_3$ seed-layer was applied as an inter-layer between PZT and $ZrO_2$ layer to improve the crystalline of PZT thin film. The fabricated PZT thin film had a remanent polarization of 5.3uC/$cm^2$ and the coercive field of 60kV/cm. The fabricated energy harvester using PZT thin film with PTO seed-layer generated 1.1uW of electrical power to $2.2M{\Omega}$ of load with $4.4V_{pvp}$ from vibration of 0.39g at 528Hz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.91-92
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• 2007

An anomalous positive temperature coefficient of electrical resistivity (PTCR) was investigated in a ferroelectric lead-free perovskite-type compound $(Bi_{0.5}Na_{0.5})TiO_3$ within $BaTiO_3$-based solid solution ceramics. The effect of $Nb_2O_5$ content on the electrical properties and the microstructure of (1 - x) $BaTiO_3-x\;(Bi_{0.5}Na_{0.5})TiO_3$ (BNT) ceramics made using a conventional mixed oxide process also has been studied. The Curie temperature was obviously increased with the increasing of $(Bi_{0.5}Na_{0.5})TIO_3$ content. The Nb - doped BNT ceramics (x=0.01) display low resistivity values of $10^{1{\circ}}C-10^{2{\circ}}C$ ohm.cm at room temperature and the Curie Temperature of $T_c=160^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.95.2-95.2
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• 2010

염료감응형 태양전지의 효율을 향상을 시키기 위하여, 이산화티타니아박막을 doctor-blade 방법으로 FTO 기판위에 15-16um 코팅을 한뒤, 다른 온도의 $400^{\circ}C-600^{\circ}C$ 범위에서, 소결을 하였다. 상대전극은 FTO 기판위에 5Ml의 Pt용액을 가지고, $450^{\circ}C$온도에서 제작을 하였다. 실험의 결과 이산화티타니아의 표면거칠기 및 입자사이즈의 소결의 형상에 따라 DSSC의 효율의 상관관계가 영향을 받았다. 표면의 형상은 AFM으로 측정을 하였으며, 표면의 단차가 RMS의 값이 7nm이하 일 때, 효율의 향상을 이루었다. 실험결과 $500^{\circ}C$ 이하일 때, 상대적으로 낮은 open circuit voltage를 이루었으며, 낮은 Fill-factor를 이루었다. $500^{\circ}C$이상의 온도에서는 상대적으로 높은 high circuit voltage와 높은 fill factor를 나타내었다. 실험결과 $500^{\circ}C$에서 소결된 전극을 가진 DSSC가 단락의 전압과 개방전류가 상호보완된 적정값을 가져 가장 개선된 FF와 Eff를 나타내었다. 이와 같은 특성은 이산화티타니아의 준위 모식도에서 설명이 될수 있고, 이산화티타니아의 최적의 necking 및 pore, 입자크기등이 제어될수 있음을 의미한다.

• Journal of Environmental Science International
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• v.15 no.9
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• pp.855-864
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• 2006

This study introduces a method to eliminate formaldehyde and benzene, toluene from indoor air by means of a photocatalytic oxidation reaction. In the method introduced, for the good performance of the reaction, the effect and interactions of the $TiO_2$ catalyst and ultraviolet in photocatalytic degradation on the reaction area, dosages of catalysts, humidity and light should be precisely examined and controled. Experiments has been carried out under various intensities of UV light and initial concentrations of formaldehyde, benzene and toluene to investigate the removal efficiency of the pollutants. Reactors in the experiments consist of an annular type Pyrex glass flow reactor and an 11W germicidal lamp. Results of the experiments showed reduction of formaldehyde, benzene and toluene in ultraviolet $/TiO_2/$ activated carbon processes (photooxidation-photocatalytic oxidation-adsorption processes), from 98% to 90%, from 98% to 93% and from 99% to 97% respectively. Form the results we can get a conclusion that a ultraviolet/Tio2/activated carbon system used in the method introduced is a powerful one for th treatment of formaldehyde, benzene and toluene of indoor spaces.

• Journal of the Korean Ceramic Society
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• v.45 no.6
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• pp.324-330
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• 2008

Activated carbon/$TiO_2$ (AC/$TiO_2$) composites modified with different concentrations of Fe were prepared. The $N_2$ adsorption data showed that the composites had decreased surface area compared with the pristine activated carbon. This indicated the blocking of the micropores on the surface of AC, which was further supported by observation via SEM. XRD results showed patterns for the composites and an anatase typed titanium dioxide structure with a small part of rutile in a higher Fe concentration (> 1.0 mol/L). EDX results showed the presence of C and, O, with Ti peaks on the composites of Fe-AC/$TiO_2$ with relatively lower Ti concentration, which may be due to the higher Fe concentration incorporated into the composites. Subsequently, the photocatalytic effects on methylene blue (MB) were investigated. The improved decomposition of MB showed the combined effects of adsorptions and photodegradation. Especially, the composites modified by Fe revealed enhanced photodegradation behaviors of MB.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1990.10a
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• pp.60-64
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• 1990

In this studies, structural, dielectrical piezoelectrical properties and temperature stability of 0.05Pb(Pb($Mg_{1/3}Nb_{2/3}$)$O_3$+ 0.95Pb($Zr_{0.53}Tio_{0.47}$)$O_3$+$\alpha$[wt%] $Cr_2O_3$ piezoelectric ceramics fabricated by the Hot-Press method were investigated. And Poisson ratios of the specimens were measured in order to see that they can be used as the substrates for energy-trapped devices. The specimens of which Poisson ratio was more than 3/1 had the $\alpha$ range 0.3~0.75, and piezoelectric properties were degraded in the range $\alpha$$\geq$0.75, and temperature stability was good in the $\alpha$ range 0.5~0.75. Accordingly, the optimal point of $Cr_2O_3$ additive weight is sure to be in the vicinity of 0.5[wt%].

• Wind and Structures
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• v.26 no.1
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• pp.1-9
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• 2018

This research studies the dynamic analysis of a concrete column reinforced with titanium dioxide ($TiO_2$) nanoparticles under earthquake load. The effect of nanoparticles accumulation in a region of concrete column is examined using Mori-Tanaka model. The structure is simulated mathematically based on the theory of sinusoidal shear deformation theory (SSDT). By calculating strain-displacement and stress-strain relations, the system energies include potential energy, kinetic energy, and external works are derived. Then, using the Hamilton's principle, the governing equations for the structure are extracted. Using these equations, the response of the concrete column under earthquake load is investigated using the numerical methods of differential quadrature (DQ) and Newark. The purpose of this study is to study the effects of percentage of nanoparticles, nanoparticles agglomeration, geometric parameters and boundary conditions on the dynamic response of the structure. The results indicate that by increasing the volume percent of $TiO_2$ nanoparticles, the maximum dynamic deflection of the structure decreases.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.83-86
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• 1999

We have fabricated $_2Cu_3O_7$ step-edge junctions with different step orientations and studied their transition properties. Steps with different orientations were prepared on the substrate. Josephson junctions were made on a single substrate with step orientations ranging from 0$^{\circ}$ to 165$^{\circ}$ at 15$^{\circ}$ interval. We measured current-voltage characteristics, the critical current, and the superconducting transition temperature as a function of the angle. The critical current showed a modulation that has a maximum near 0$^{\circ}$ or 90$^{\circ}$ and a minimum near 45$^{\circ}$ and 135$^{\circ}$. We believe that the critical current modulation with the step orientation could be associated with the symmetry of high T$_c$ superconductor.