• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.545-551
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• 2007

HCl concentration, reaction temperature, and $Ti^{4+}$ concentration are the decisive factors in determining the structure of precipitates in the process of synthesis of $TiO_2$ particles from aqueous $TiCl_4$ solution by precipitation and the volumetric proportion of brookite phase in $TiO_2$ particles can be controlled by these factors. Pure brookite-type $TiO_2$ nanoparticles were synthesized by heating the aqueous $TiCl_4$ solution with no more than 1.0 M of $Ti^{4+}$, in which the concentration of HCl was kept in the range of about 2.53~6.41 M during reaction, at the temperature below $70^{\circ}C$ for 20 h. Also, Pure brookite was finally transformed to a rutile phase via an anatase phase through heat-treatment.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.11a
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• pp.165-169
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• 2002

BaTiO$_3$ 분말을 Ba(OH)$_2$ㆍ8$H_2O$와 아나타제형의 TiO$_2$ㆍ$\chi$$H_2O$를 이용하여 광화제 첨가 없이 열수처리에 의한 탈수(dehydration) 및 재결정화(recrystallization) 과정을 통한 수열합성법에 의해 제조하였다. Autoclave 반응기를 이용한 실험의 경우, BaTiO$_3$ 분말을 생성하기 위한 최적 반응온도 및 시간은 각각 21$0^{\circ}C$, 4시간으로 확인되었으며, 이 때 생성된 BaTiO$_3$ 분말의 크기는 0.1~0.2$mu extrm{m}$로 입도분포가 양호하였다. 그리고, 바륨과 티타늄의 농도비가 증가됨에 따라 결정화도(tetragonality)가 증가하는 경향을 나타내고 있다. 이는 반응하지 않고 남아 있는 바륨의 영향으로 생각되며, 이는 반응물의 pH와도 관련이 있다. 또한, 반응온도 및 시간도 결정화도에 커다란 영향을 미치는 변수로 주로 반응온도 및 시간이 증가함에 따라 결정화도도 함께 증가하는 추세를 나타내고 있다.

• Journal of Powder Materials
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• v.18 no.4
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• pp.359-364
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• 2011

Zr-Ti alloy powders were successfully synthesized by magnesium thermal reduction of metal chlorides. The evaporated and mixed gasses of $ZrCl_4+TiCl_4$ were injected to liquid magnesium and the chloride components were reduced by magnesium leading to the formation of $MgCl_2$. The released Zr and Ti atoms were then condensed to particle forms inside the mixture of liquid magnesium and magnesium chloride, which could be dissolved fully in post process by 1~5% HCl solution at room temperature. By the fraction-control of individually injected $ZrCl_4$ and $TiCl_4$ gasses, the final compositions of produced alloy powders were changed in the ranges of Zr-0 wt.%~20 wt.%Ti and their purity and particle size were about 99.4% and the level of several micrometers, respectively.

• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.29-35
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• 2007

Titanium was oxidized with oxygen plasma and calcinated with rapid thermal annealing for degradation of humic acid dissolved in water. Titania photocatalytic plate was produced by titanium surface oxidized with oxygen plasma by Plasma Enhanced Chemical Vapor Deposition (PECVD). RF-power and deposition condition is controlled under 100 W, 150 W, 300 W and 500 W. Treatment time was controlled by 5 min and 10 min. The film properties were evaluated by the X-ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD). From the experimental results, we found the optimal condition of titania film which exhibited good performance. Moreover photocatalytic capacity was about twice better than thermal spray titania film, and also as good as titania powder.

• Journal of Powder Materials
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• v.19 no.5
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• pp.348-355
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• 2012

Cold spray deposition using Titanium powder was carried out to investigate the effects of powder morphology and powder preheating on the coating properties such as porosity and hardness. The in-flight particle velocity of Ti powder in cold spray process was directly measured using the PIV (particle image velocimetry) equipment. Two types of powders (spherical and irregular ones) were used to manufacture cold sprayed coating layer. The results showed that the irregular morphology particle appeared higher in-flight particle velocity than that of the spherical one under the same process condition. The coating layer using irregular morphology powder represented lower porosity level and higher hardness. Two different preheating conditions (no preheating and preheating at $500^{\circ}C$) were used in the process of cold spraying. The porosity decreased and the hardness increased by conducting preheating at $500^{\circ}C$. It was found that the coating properties using different preheating conditions were dependent not on the particle velocity but on the deformation temperature of particle. The deposition mechanism of particles in cold spray process was also discussed based on the experimental results of in flight-particle velocity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.3061-3071
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• 2000

Densification behavior of titanium alloy powder was investigated under hot pressing at various pressures and temperatures. Experimental date were obtained for densification of titanium alloy powder under an instantaneous loading and subsequent creep deformation during hot pressing. The constitutive models of Fleck et al. and the modified Gurson were employed for thermo-phastic deformation under the instantaneous loading and that f Abouaf and co-workers for creep deformation of titanium alloy powder during hot pressing. By implementing these constitutive equations into a finite element program(ABAQUS), finite element results were compared with experimental data during hot pressing. To investigate the effect of friction between the power and die wall, density distributions of power compacts were measured and compared with finite element calculations. Finite element results from the models of Fleck et al. and the modified Gurson agreed reasonably good with experimental data for densification and density distribution of titanium alloy powder under the instantaneous loading during hot pressing. Finite element results from the model of Abouaf and co-workers, however, somewhat overestimate experimental data for creep deformation of power compacts during hot pressing.

• Journal of Powder Materials
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• v.17 no.5
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• pp.385-389
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• 2010

Titanium powders have been usually produced by de-hydrogenating treatment in vacuum with titanium hydride ($TiH_2$) powders prepared by milling of hydrogenated sponge titanium, $TiH_x$. The higher stoichiometry of x in $TiH_x$, whose maximum value is 2, is achieved, crushing behavior is easier. $TiH_x$ powder can be, therefore, easy to manufactured leading to obtain higher recovery factor of it. In addition, contamination of the powder can also minimized by the decrease of milling time. In this study, the hydrogenation behavior of sponge titanium was studied to find the maximum stoichiometry. The maximum stoichiometry in hydride formation of sponge titanium could be obtained at $750^{\circ}C$ for 2 hrs leading to the formation of $TiH_{{\sim}1.99}$ and the treating temperatures lower or higher than $750^{\circ}C$ caused the poor stoichiometries by the low hydrogen diffusivity and un-stability of $TiH_x$, respectively. Such experimental behavior was compared with thermodynamically calculated one. The hydrogenated $TiH_{1.99}$ sponge was fully ball-milled under -325 Mesh and the purity of pure titanium powders obtained by de-hydrogenation was about 99.6%.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.56.2-56.2
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• 2011

고효율 염료감응 태양전지를 제작하기 위해 Sol-gel법을 사용하여 $TiO_2$ 분말을 제조하였다. 제조 과정 중 다양한 양의 nitric acid를 첨가하여 pH를 조절하였다. Sol-gel법을 위한 출발 물질로 titanium (IV) isopropoxide(TTIP)와 DI water를 사용하였으며 nitric acid은 0, 0.05, 0.1, 0.15의 몰비(nitric acid/TTIP)로 첨가하였다. 첨가한 결과 pH는 $22^{\circ}C$에서 각각 5.52, 2.26, 1.68, 1.38이었다. 얻어진 $TiO_2$ 콜로이드 용액은 결정성 있는 분말로 제조 후 $5{\times}5[mm^2]$ 크기의 염료감응 태양전지를 제작하는데 사용 되였다. $TiO_2$의 결정구조 및 형태는 cell의 XRD와 FE-SEM으로 분석되었고 전기화학적 특성을 분석하기 위해 irradiation of AM 1.5 ($100mW/cm^2$) simulatedsunlight에서 I-V 곡선을 측정하였다. 측정 결과 몰비(nitric acid/TTIP) 0.05, pH가 2.26일 때 가장 우수한 효율 특성을 보였다.

• Laser Solutions
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• v.18 no.3
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• pp.1-5
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• 2015

A 3D printer based on laser powder deposition (LPD), also known as DED (direct energy deposition), has been developed for fabricating metal parts. The printer uses a ytterbium fiber laser (1070nm, 1kW) and is equipped with an Ar purge chamber, a three-dimensional translation stage and a powder feeding system composed of a powder chamber and delivery nozzles. To demonstrate the performance of the printer, a tapered cylinder of 320mm in height has been fabricated successfully using Ti-6Al-4V powders. The process parameters including the laser output power, the scan speed, and the powder feeding rate have been optimized. A 3D printed test specimen shows mechanical properties (yield strength, ultimate tensile strength, and elongation) exceeding the criteria to employed in a variety of Ti alloy applications.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.11a
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• pp.55-55
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• 2011

국내의 등산용 아웃도어 제품의 경우, 기능성인 투습도와 내수압만을 증대시키려는 연구가 주류를 이루고 있었다. 하지만, 실제 등산용 아웃도어의 경우 산악지형인 고지대에서 사용시간이 많으므로, 이에 따른 장시간의 직접적인 태양광 노출로 인한 인체에 치명적인 영향을 야기시키고 있지만, 인체 보호용 헬스케어 아웃도어 제품에 대한 연구는 미흡한 실정이다. 태양광은 자외선 2.5%, 가시광선 51.5%, 적외선 46.0%의 광량 비율을 가지고 있으며, 이 중 자외선은 광량은 적지만 에너지적으로 높아 유기물 분해 및 열화를 일으킨다. 이러한 자외선을 차단하기위해 아웃도어 의류에서는 유무기하이브리드 소재를 표면에 코팅시키게 되며, 기능성 코팅액내에 함유되어 있는 나노분말의 경우 이산화티타늄($TiO_2$), 산화세륨(CeO), 산화아연(ZnO), 삼산화텅스텐($WO_3$), 산화마그네슘(MgO) 등이 주로 사용되어 진다. 본 연구에서는 자외선 흡수소재로 나노산화아연분말을 이용하여, 그 입도 및 코팅용 희석 용매내의 분산성을 확인하고, 함유량을 달리한 코팅 수지를 제조하여, 코팅시편 제조 후 그 특성을 비교/분석하여 자외선 차단 효과를 확인하고자 한다.