• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.901-908
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• 1999

Effects of LPMOCVD process parameters on the properties of TiO2 thin film were investigated. Depositions were made in the range of temperature 300-67$0^{\circ}C$ with various TTIP(Titanium Tetraisopropoxide) concentrations by contrlling bubbler temperature(40-8$0^{\circ}C$) and/or flow rate(30-90 sccm). Post annealing treatments were carried out at 500-80$0^{\circ}C$ range in the air. Films deposited at 40$0^{\circ}C$ have denser morphology than those of films deposited at 50$0^{\circ}C$ and $600^{\circ}C$ due to slower deposition rate. Bubbler temperature can affect on the deposition rate in mass transfer controlled regime such as 50$0^{\circ}C$ or higher but not below 50$0^{\circ}C$ where surface reaction rate becomes important. On the contrary for films deposited above 50$0^{\circ}C$ flow rate can raise deposition rate but eventually saturate it at the 50 sccm and above due to retarded adhesion of decomposed species. But for films deposited at 40$0^{\circ}C$ deposition rate increases stadily with flow rate. As the film becomes more porous A(200) texture can not be developed and AnataselongrightarrowRutile transition kinetics increases.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.160-160
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• 2017

Commercially pure titanium (Cp-Ti) and Ti alloys (typically Ti-6Al-4V) display excellent corrosion resistance and biocompatibility. Although the chemical composition and topography are considered important, the mechanical properties of the material and the loading conditions in the host have, conventionally. Ti and its alloys are not bioactive. Therefore, they do not chemically bond to the bone, whereas they physically bond with bone tissue. The electrochemical deposition process provides an effective surface for biocompatibility because large surface area can be served to cell proliferation. Plasma electrolyte oxidation (PEO) enables control in the chemical composition, porous structure, and thickness of the TiO2 layer on Ti surface. Silicon (Si) in particular has been found to be essential for normal bone and cartilage growth and development. Zinc (Zn) plays very important roles in bone formation and immune system regulation, and is also the most abundant trace element in bone. The objective of this work was to study on electrochemical behaviors of PEO-treated Ti-6Al-4V Alloy in solution containing Zn and Si ions. The morphology, the chemical composition, and the microstructure analysis of the sample were examined using FE-SEM, EDS, and XRD. The potentiodynamic polarization and AC impedance tests for corrosion behaviors were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat. The promising results successfully demonstrated the immense potential of Si/Zn-TiO2 coatings in dental and biomaterials applications.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.589-594
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• 1997

Superconducting $YBa_2Cu_3O_y$ thin films were prepared at the deposition temperature of $650^{\circ}C$ under oxygen partial pressure of 0.0126 Torr on Si(111) and SrTiO3(100) substrates by chemical vapor deposition technique using $\beta$-diketonates of Y, Ba and Cu as source materials. The thin film fabricated on $SrTiO_3(100)$ had a $T_{c,onset}$ of 91K and $T_{c.0}$ of 87K. The thin film prepared on Si(111) had a $T_{c,onset}$ of 91K but didn't have a $T_{c.0}$ at liquid nitrogen boiling point(77.3K). Dense and two-dimensionally well alligned microstructure was developed for the film deposited on $SrTiO_3(100)$ substrate whereas a relatively porous and randomly distributed microstructure was developed for the film prepared on Si(111) substrate.

• Applied Chemistry for Engineering
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• v.7 no.2
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• pp.269-279
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• 1996

The porous armophous catalysts, composed of $SiO_2-TiO_2-V_2O_5$ were prepared through SOL-GEL process by differing the preparation parameters. Selected the optimum SOL-GEL catalyst which has the best NO removal activity through the screening test, and repeated coating it on the cordierite monolith which is the freely through and inert. And examined the NOx, SOx simultaneous removal effect under S. C. R. condition. In addition to its characterization performances by the DTA, TGA, BET, $NH_3$ and NO TPD, ESCA, XRD etc.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.440-441
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• 2006

Several titanate powders ($Al_2TiO_5,\;SrTiO_3$, etc.) were synthesized by an ethylene glycol solution route. Titanium isopropoxide and nitrate salts were dissolved in stoichiometric proportions in liquid-type ethylene glycol without any precipitation. The parent precursor sols were dried to porous gels, and then the gels were calcined and crystallized. All synthesized titanate powders had stable crystallization behavior at low temperature and high specific surface area after a simple ball-milling process. A three-component PZT $(Pb(Zr_{0.52}{\cdot}Ti_{0.48})O_3)$ powder was also synthesized successfully by the ethylene glycol method. In this study, the characteristics of the multi-component titanate powders by the ethylene glycol method are examined.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.1-7
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• 2012

In this article, I will introduce recent developments of environmental-friendly materials fabricated using atomic layer deposition (ALD). Advantages of ALD include fine control of the thin film thickness and formation of a homogeneous thin fim on complex-structured three-dimensional substrates. Such advantages of ALD can be exploited for fabricating environmental-friendly materials. Porous membranes such as anodic aluminum oxide (AAO) can be used as a substrate for $TiO_2$ coating with a thickness of about 10 nm, and the $TiO_2$-coated AAO can be used as filter of volatile organic compound such as toluene. The unique structural property of AAO in combination with a high adsorption capacity of amorphous $TiO_2$ can be exploited in this case. $TiO_2$ can be also deposited on nanodiamonds and Ni powder, which can be used as photocatalyst for degradation of toluene, and $CO_2$ reforming of methane catalyst, respectively. One can produce structures, in which the substrates are only partially covered by $TiO_2$ domains, and these structures turns out to be catalytically more active than bare substrates, or complete core-shell structures. We show that the ALD can be widely used not only in the semiconductor industry, but also environmental science.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.50-54
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• 2013

In this work, the effects of blocking layer and optimally fabricated electrolyte were investigated with respect to impedance and conversion efficiency of the cells.A layer of $TiO_2$ less than ~200nm in thickness, as a blocking layer, was deposited by rf sputtering onto the F:$SnO_2$ (FTO) glass to be isolated from the electrolyte in dye-sensitized solar cells (DSCs). Also, optimum condition of electrolytes preparation for DSCs was investigated. 3-methoxyppropionitrie and redox pairs with LiI and $I_2$ were used as solvents for fabrication of electrolyte. The electrochemical impedances of DSCs using this photo-anode were $R_1$: 13.8, $R_2$: 15.1, $R_3$: 11.9 and $R_h$: $8.3{\Omega}$, respectively. The $R_2$ impedance related by electron transportation from porous $TiO_2$ to FTO showed lower than that of normal DSCs. The photo-conversion efficiency of prepared DSCs was 6.4% and approximately 1.3% higher than general one.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.467-471
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• 2009

Effects of boron and carbon on the densification and thermal decomposition of an AlN-SiC-$TiB_2$ system were investigated. $SiO_2$ was mostly removed by the addition of carbon, while $Al_2O_3$ formed $Al_4O_4C$ and promoted the densification of the systems above $1850^{\circ}C$. Rather porous specimens were obtained without the additives after hot pressing at $2100^{\circ}C$, while densification was mostly completed at $2000^{\circ}C$ by using the additives. The sintering temperature decreased further to $1950^{\circ}C$ by applying spark plasma sintering. The additives promoted the shrinkage of AlN by forming a liquid phase which was originated from the carbo- and boro-thermal reduction of $Al_2O_3$ and AlN.

• Korean Journal of Materials Research
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• v.23 no.4
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• pp.240-245
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• 2013

Electrochemical surface treatment is commonly used to form a thin, rough, and porous oxidation layer on the surface of titanium. The purpose of this study was to investigate the formation of nanotubular titanium oxide arrays during short anodization processing. The specimen used in this study was 99.9% pure cp-Ti (ASTM Grade II) in the form of a disc with diameter of 15 mm and a thickness of 1 mm. A DC power supplier was used with the anodizing apparatus, and the titanium specimen and the platinum plate ($3mm{\times}4mm{\times}0.1mm$) were connected to an anode and cathode, respectively. The progressive formation of $TiO_2$ nanotubes was observed with FE-SEM (Field Emission Scanning Electron Microscopy). Highly ordered $TiO_2$ nanotubes were formed at a potential of 20 V in a solution of 1M $H_3PO_4$ + 1.5 wt.% HF for 10 minutes, corresponding with steady state processing. The diameters and the closed ends of $TiO_2$ nanotubes measured at a value of 50 cumulative percent were 100 nm and 120 nm, respectively. The $TiO_2$ nanotubes had lengths of 500 nm. As the anodization processing reached 10 minutes, the frequency distribution for the diameters and the closed ends of the $TiO_2$ nanotubes was gradually reduced. Short anodization processing for $TiO_2$ nanotubes of within 10 minutes was established.

• Korean Journal of Materials Research
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• v.34 no.1
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• pp.34-43
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• 2024

New piezoelectric and triboelectric materials for energy harvesting are being widely researched to reduce their processing cost and complexity and to improve their energy conversion efficiency. In this study, BaTiO₃ films of various thickness were deposited on Ni foams by R.F. magnetron sputtering to study the piezoelectric and triboelectric properties of the porous spongy structure materials. Then piezoelectric nanogenerators (PENGs) were prepared with spongy structured BaTiO₃ and PDMS composite. The output performance exhibited a positive dependence on the thickness of the BaTiO₃ film, pushing load, and poling. The PENG output voltage and current were 4.4 V and 0.453 ㎂ at an applied stress of 120 N when poled with a 300 kV/cm electric field. The electrical properties of the fabricated PENG were stable even after 5,000 cycles of durability testing. The triboelectric nanogenerators (TENGs) were fabricated using spongy structured BaTiO₃ and various polymer films as dielectrics and operated in a vertical contact separation mode. The maximum peak to peak voltage and current of the composite film-based triboelectric nanogenerator were 63.2 V and 6 ㎂, respectively. This study offers new insights into the design and fabrication of high output nanogenerators using spongy structured materials.