• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.9
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• pp.1175-1182
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• 2001

Chemical compositions of polydisperse SiO$_2$/TiO$_2$multicomponent aggregates were measured for different heights from the burner surface and different mobility diameters of aggregates. SiO$_2$/TiO$_2$multicomponent particles were generated in a hydrogen/oxygen coflow diffusion flame from two sets of precursors: TTIP(titanium tetraisopropoxide), TEOS(tetraethylorthosilicate). To maintain 1:1 mole ratio of TTIP:TEOS vapor, flow rate of carrier gas $N_2$was fixed at 0.6lpm for TTIP, at 0.1lpm for TEOS. In-situ sampling probe was used to supply particles into DMA(differential mobility analyzer) which was calibrated with using commercial DMA(TSI, model 3071A) and classifying monodisperse multicomponent particles. Classified monodisperse particles were collected with electrophoretic collector. The distributions of composition from particles to particle were determined using EDS(energy dispersive spectrometry) coupled with TEM(transmission electron microscope). The chemical(atomic) compositions of classified monodisperse particle were obtained for different heights; z=40mm, 60mm, 80mm. The results suggested that the chemical(atomic) composition of SiO$_2$decreased with the height from burner surface and the composition of SiO$_2$and TiO$_2$approached to the value of 1 to 1 fat downstream. It is also found that the composition of SiO$_2$decreases as the mobility diameter of aggregate increases.

• Journal of the Korean Applied Science and Technology
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• v.24 no.3
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• pp.246-252
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• 2007

$BaTiO_3$ powders were prepared by sol-gel method from different concentration of KOH aqueous solution and Ba/Ti molar ratio. Particle shape, size and crystal structure of prepared $BaTiO_3$ powders were analyzed by SEM, XRD, and FT-IR. As the result of KOH concentration changing, spherical particles were obtained by condition more than 3 M and particle size decreased as concentration increasing. Different appearance showed between dried and sintered powders against changing of Ba/Ti molar ratio. In case of dried powders, the crystallinity decreased as molar ratio increasing. On the other hand, increased as molar ratio increasing in case of sintered powders.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.185-185
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• 2009

Polypropylene beads (PP) coated with $TiO_2$ thin films were prepared by a rotating cylindrical plasma chemical vapor deposition (PCVD) reactor and were used to remove phenol in aqueous solution. The $TiO_2$ thin films of 416 nm thickness were coated on the PP particles uniformly. As the number of $TiO_2$-coated PP beads increases, the phenol is degraded faster, because of larger total surface area of photocatalysts for photodegradation. This study shows that a rotating cylindrical PCVD reactor can be a good method to prepare the particles coated with high-quality $TiO_2$ thin films, which can be applied to the pollutant removal by a photodegradation reaction of $TiO_2$ with high efficiency.

• Journal of Welding and Joining
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• v.15 no.6
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• pp.96-104
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• 1997

The present study was aimed to correlate the microstructure and the hardness as well as the wear resistance of the metal-ceramic particulated composite layer on the pure Al plate. The composite layers were constructed by the addition of TiC particles on the surface of Al-Cu alloyed layers by PTA overlaying process. Initially, the Al-Cu alloyed layers were achieved by the deposition of Al-(25 ~ 48%) Cu alloys on the pure Al plate by TIG process. It was revealed that TiC particles were uniformly dispersed without any reaction with matrix in the composite layer. The volume fraction of TiC particles (TiC V F) increased from 12% to 55% with increasing the number of pass of composite layer. Hardnesses of (Al-48%Cu + TiC (3&4layers)) composite layer were Hv450 and Hv560, respectively, due to the increase of TiC V/F. Hardnesses of (Al-Cu + TiC) composite layers decreased gradually with insreasing temperature from 100$^{\circ}$C to 400$^{\circ}$C, and hardnesses at 400$^{\circ}$C were then reached to 1/5 - 1/10 of room temperature hardness depending on the construction of composite layers. The Specific wear of (Al + Tic) layer and Al-48%Cu alloyed layer decreased to 1/10 of the of pure Al, while the specific wear of (Al-48%Cu + TiC (4 layers)) composite layer exhibited 1/15 of that of steel such as SS400 and STS304.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.544-548
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• 2008

The formation of $TiB_2-SiC$ ceramics from $TiB_2$-Polycarbosilane (PCS) mixtures was investigated. The powder mixture of $TiB_2$ with PCS was pressed at $300^{\circ}C$ with 200 MPa and sintered at $1700{\sim}2000^{\circ}C$ for 1 h in a flowing Ar atmosphere. The sintered density of $TiB_2$ with PCS is 93.7% after sintering at $2000^{\circ}C$ for 1 h, which is slightly smaller than that of the specimen without PCS. The microstructure of $TiB_2$ with PCS consists of small and uniform $TiB_2$ particles with well dispersed SiC particles derived from PCS. It is believed that the addition of PCS was effective to suppress the grain growth of $TiB_2$.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.217-221
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• 2002

In the coarse grain HAZ adjacent to the fusion line, most of the TiN particles in conventional Ti added steel are dissolved and austenite grain growth is easily occupied during welding process. To avoid this difficulty, thermal stability of TiN particle is improved by increasing the nitrogen content in steel. In this study, the effect of high nitrogen TiN particle on preventing austenite grain growth in HAZ was investigated. Increased thermal stability of TiN particle is helpful for preventing the austenite grain growth by pinning effect. High nitrogen TiN particle in simulated HAZ were not dissolved even at high temperature such as 1400 C and prevented the austenite grain growth in simulated HAZ. Owing to small austenite grain size in HAZ the width of coarse grain HAZ in high nitrogen TiN steel was decreased to 1/10 of conventional TiN steel. Even high heat input welding, the microstructure of coarse grain HAZ consisted of fine polygonal ferrite and pearlite and toughness of coarse grain HAZ was significantly improved.

• Clean Technology
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• v.29 no.2
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• pp.118-125
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• 2023

Once a site is contaminated with polychlorinated biphenyls (PCBs), serious environmental and human health risks are inevitable. Therefore, innovative but economical in situ remediation technologies must be immediately applied to the contaminated site. Recently, nanoscale zero-valent iron (nano-ZVI) particles have successfully been applied for the dechlorination of various chlorinated organic compounds like TCE, PCE and DDT, and they are considered to be environmentally safe due to the high abundance of iron in the earth's crust. Nano-ZVIs are much more reactive than granular ones, but tend to agglomerate due to their high surface energy and magnetic properties. In order to prevent them from being agglomerated toward larger particles, TiO₂ was used as a support to immobilize the nano-ZVI particles as much as possible. 10wt% ZVI/TiO₂ was prepared by adding NaBH₄ slowly into an FeSO₄/TiO₂ aqueous slurry. In spite of their non-uniformity in size, the nano-ZVI particles were quite successfully dispersed onto the exterior surface of a non-porous TiO₂ powder. The ZVI/TiO₂ was then employed to degrade Aroclor 1242, a kind of PCBs standard, in spiked soil, and its reactivity towards the degradation of Aroclor 1242 was investigated. The fabricated ZVI/TiO₂ degraded Aroclor 1242 in soil quite effectively, but the creation of remaining dechlorinated compounds, possibly high molecular weight hydrocarbons, in the soil was unavoidable.

• Journal of Powder Materials
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• v.11 no.4
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• pp.322-327
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• 2004

Ultrafine titanium carbide particles were synthesized by the reaction of liquid-magnesium and vaporized TiCl$_{4}$+C$_{x}$Cl$_{4}$(x = 1 and 2) solution. Fine titanium carbide particles with about 50 nm were successfully produced by combining Ti and C atoms released by chloride reduction of magnesium, and vacuum was then used to remove the residual phases of MgCl$_{2}$ and excess Mg. Small amounts of impurities such as O, Fe, Mg and Cl were detected in the product, but such problem can be solved by more precise process control. The lattice parameter of the product was 0.43267 nm, near the standard value. With respect to the reaction kinetics, the activation energy for the reactions of TiCl$_{4}$+C$_{2}$Cl$_{4}$and Mg was found to 69 kJ/mole, which was about half value against the use of TiCl$_{4}$+CCl$_{4}$, and such higher reactivity of the former contributed to increase the stoichiometry until the level of TiC$_{0.96}$ and decrease the free carbon content below 0.3 wt.%.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1301-1305
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• 2005

The performance of OTFT with $PVP-TiO_2$ composite, as a gate insulator, is reported, including the effect of surfactant for synthesizing the composite material. According to our investigation results, it was one of critical issues to prevent the aggregation of $PVP-TiO_2$ particles during the synthesis process. From this point of view, $PVP-TiO_2$ particles were treated using Tween80, as a surfactant, and we could reduce the aggregated $PVP-TiO_2$ clusters. As a result, the OTFT with the composite insulator showed the threshold voltage of about -8.3 V and the subthreshold slope of about 1.5 V/decade, which are the optimized properties compared to those of OTFTs with bare PVP, in this study. It is thought that these characteristic improvements are originated from the increase in the dielectric constant of the PVP-based insulator by compositing with high-k particles.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.28 no.1
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• pp.214-224
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• 2002

High concentrated $TiO_2$ nano colloids were synthesized by sol-gel method. Reactions were performed in $TiCl_4$/HCl/$H_2O$ aqueous solution and the conditions of particles such as shape, size and aggregation, etc. were controlled by polymerization and adsorption of acrylamide in surface of $TiO_2$ nano particles. And also, aminopropyltriethoxysilane was added instead of acrylamide and compared each other. The prepared colloids were well dispersed and showed the strong absorption peaks at 350nm-370nm which is blue shifted to 20-30nm, compared to macro particles. The obtained techniques from $TiO_2$ nato colloids synthesis were utilized in coating on boron nitride powders which are nonpolar and isoelectronic materials of carbon. Their surface morphology, structure, thermal stability and U. V absorption chracteristics were examined by SEM(Scanning Electron Microscopy), XRD(X-ray diffraction), TG/DTA(Thermogravimetric and Differential Thermal Analysis), UV-VIS(Ultraviolet-Visible Spectroscopy).