• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.208-208
• /
• 2003

저온균일침전법(HPPLT)으로 제조된 TiO$_2$나노분말은 10$0^{\circ}C$이하의 온도에서 rutile상을 얻을 수 있다. 또한, rutile에서 anatase로의 상변화는 합성시간, 가열속도, 반응온도 그리고 음이온 첨가에 의해 일어난다고 보고되어졌지만, 금속양이온들에 의한 상변화는 알려진 바가 없다. 따라서, 다양한 양이온을 첨가하여 저온균일침전법에서 TiO$_2$의 상변화가 어떻게 일어나는지를 조사하였다. 출발원료인 TIC1$_4$를 사용하여 가수분해하여 0.67M의 TiOCl$_2$을 얻었다. 얻어진 TiOCl$_2$ 수용액에 각각 0.01M의 금속염화물(ZrOCl$_2$, NiCl$_2$, CuCl$_2$, FeCl$_3$, AlCl$_3$ 그리고 NbCl$_{5}$)을 첨가한 후 반응기에 넣고 10$0^{\circ}C$에서 4시간동안 가열하였다 가열한 후 얻어진 침전물에 NaOH 수용액을 이용하여 PH 7-8로 중화한 후 증류수로 Cl$^{-}$이온이 제거될 때까지 충분히 세척하였다. 세척된 침전물을 105$^{\circ}C$에서 24h동안 건조하여 분말을 얻었고, rutile에서 anatase로의 상변화특성을 관찰하기 위하여 XRD, SEM, TEM, ICP 분석을 실시하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.18 no.4
• /
• pp.165-168
• /
• 2008

Ta-doped thin films were deposited on quartz and indium-tin oxide glass substrates using a co-sputtering method. The Ta-doped films formed a solid solution that induced structural changes from rutile to anatase phase. The anodic photocurrents of the Ta-doped $TiO_2$ electrodes were observed not only in UV but also in the visible light range. The photocurrent response in visible light on Ta-doped $TiO_2$ films are due to bandgap reduction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.677-680
• /
• 2003

The effect of $B_2O_3$ addition on the sintering behavior and microwave dielectric properties of $(Zn_{0.8}Mg_{0.2})TiO_3$ ceramic system were investigated. Highly dense samples were obtained at the sintering temperatures below $900^{\circ}C$. Temperature coefficient of resonance frequency(${\tau}_f$) changes to a positive value with increasing the amount of $B_2O_3$ because of the increased amount of rutile phase. The $Q{\times}f_o$ values were determined by the microstructures and sintering shrinkages which are affected by the rutile or second phase. When 6.19 mol.% of $B_2O_3$ added and sintered at $900^{\circ}C$ for 5h, it exhibits ${\epsilon}_r$ =23.5, $Q{\times}f_o$= 67,500 GHz, and ${\tau}f=-1.42ppm/^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.274-274
• /
• 2010

안료의 색상은 출발원료의 조성, 입자크기 및 소결온도에 의한 결정구조 등에 의존한다. 본 연구에서는 Rutile구조를 갖는 세라믹안료인 $TiO_2-WO_3$-NiO의 합성에서 소결온도를 결정하기 위해 소결전 출발원료를 습식법에 의하여 Jar Mill에서 0.7-0.9um로 혼합분쇄한 후 $100^{\circ}C$에서 24시간 건조하였다. 건조후 $1100-1280^{\circ}C$에서 5구간을 선정하여 소결한 시료를 Jar Mill에서 0.8-1um로 분쇄한 후, 다시 $100^{\circ}C$에서 24시간 건조하였다. 이렇게 얻어진 시료를 XRD로 상합성 정도를 조사하고, 색상 및 착색력을 spectrophotometer를 분석하였다. 색상은 1150와 $1250^{\circ}C$에서 가장 좋은 Yellow 색상이 관찰되었으며, XRD에 의한 결정성의 분석결과와 비교적 일치하고 있다. Rutile구조를 갖는 세라믹안료의 색상은 소결시의 결정화도에 따라 민감하게 변화되고 있음을 알 수 있다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.466.1-466.1
• /
• 2014

$TiO_2$는 저렴한 가격, 적절한 bandgap, 열적, 화학적, 생물학적 안정성 등으로 촉망받는 광촉매 물질이다. $TiO_2$는 rutile (tetragonal, space group: P42/mnm), anatse (tetragonal, space group: I41/amd), and brookite (orthorhombic, space group: Pbca )의 3가지 대표적인 결정구조를 가지고 있다. Rutile과 anatase는 1972년 Fujishima와 Honda가 $TiO_2$의 광촉매 특성을 발견 한 후로 아주 많은 연구가 되어왔다. 반면 brookite의 경우는 자연에 거의 존재하지 않으며, 합성방법도 어려워서 rutile과 anatase에 비해 많은 연구가 되지 않았다. 본 연구에서는 brookite를 포함한 다양한 $TiO_2$ 나노구조를 간단한 수열합성법으로 티타늄 호일 위에 합성하였다. 합성된 $TiO_2$는 반응 온도와 시간, additive의 농도에 따라서 sheet, tube, wire, pyramidal 의 4가지 morphologies를 가졌다. 이 다양한 morphologies은 SEM과 TEM으로 분석되었으며, 각 물질의 결정 구조는 XRD분석과 TEM의 SAED pattern 분석으로 sheet, tube, wire은 anatase, pyramidal 구조는 brookite라는 것이 확인 되었다. 위의 방법으로 합성된 각각의 $TiO_2$ 물질들을 working 전극으로, Pt와 Ag/AgCl을 reference와 counter 전극으로 만들어서 photoelectrochemical 특성을 측정해서 비교를 해보았을 때, brookite 물질이 anatase보다 더 좋은 photoelectrochemical 특성을 나타내는 것을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.131-131
• /
• 2012

We present our recent temperature-programmed desorption (TPD) study on catalytic reductions of $NO_x$ such as NO, $NO_2$, and $N_2O$ over rutile $TiO_2$(110) surfaces. Our results indicate that $NO_2$/NO readily reacts to give NO/$N_2O$ desorption at the substrate temperature as low as 100 K/70 K. Interestingly, $N_2O$, however, does not dissociate into $N_2$ and $O_{BBO}$ over the oxygen vacancy on the $TiO_2$(110) surface. Successive reduction of NO and $NO_2$ into $N_2O$ and NO, respectively, leaves oxygen atoms on the $TiO_2$(110) surface in a form of $O_{ad}$, which can induce additional reductive channels of NO and $NO_2$ at higher temperatures up to 400 K. During the repeated TPD cycles of $NO_x$, our x-ray photoelectron spectroscopy (XPS) analysis indicates that no N atom accumulates on the $TiO_2$ surface.

• Journal of the Mineralogical Society of Korea
• /
• v.12 no.2
• /
• pp.66-76
• /
• 1999

Intergrowth texture of biotite and chlorite crystals within an amphibolitic schist of the northwestern Okchon metamorphic belt was investigated using back-scattered electron (BSE) imaging and high-resolution transmission electron microscopy (HRTEM). BSE images show that thin chlorite and biotite packets are mixed along (001) plane to result in intergrowth texture. In addition, rutile particles of submicron size occur exclusively at the boundaries between biotite and chlorite stacks. HRTEM investigation and remnant biotite layers are closely associated with such boundaries, suggestinga possibility that chlorite layers were formed from biotite during retrograde metamorphic reaction. Such intepretation of the origin of intergrowth texture can be further supported biotite is approximately 2 w%, and that of chlorite usually lower than 0.2 wt%. Ti was apparently leached out during the alteratin of biotite to precipitate rutile particles at the such rutile particles could be an important indicator showing that the intergrowth texture of chlorite and biotite is originated by a retrograde metamorphism rather than by incomplete chlorite-to-biotite reaction during prograde metamorphism. Biotite crystals contain intercalated chlorite layers will result in somewhat high Mg and Al, and the use of such inhomogeneous biotite will result in impreciese geothermobarometric calculations.

• Journal of the Korean Society for Heat Treatment
• /
• v.6 no.4
• /
• pp.204-212
• /
• 1993

The preparation of $TiO_2$ fine particles from $TiCl_4$ and oxygen by the vapor-phasereaction was investigated at $850^{\circ}C$ with an emphasis on the effect of its experimental conditions on the crystal type of the products. Anatase $TiO_2$ particles prepared by experiment were used to study anatase-rutile transition by calcination temperature, the additives and gas atmosphere. The results were as follows. The kinetics of anatase-rutile transition was well agreed with A vrami equation, and the activation energy of transition was 35kcal/mol. The addition of CuO in anatase $TiO_2$ particles accelerated the anatase-rutile transition, and its transition was retarded in vaccum.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.7
• /
• pp.349-353
• /
• 2006

[ $TiO_2-Nb_2O_5$ ] sol was prepared using sol-gel method. Crystalline properties of gel powder changed from rutile phase to anatase phase with increasing $Nb_2O_5$ additives at $800^{\circ}C$, while they retained rutile phase regardless of $Nb_2O_5$ additives at $900^{\circ}C,\;1,000^{\circ}C$. They retained amorphous phase from $50^{\circ}C\;to\;400^{\circ}C$, retained anatase phase from $500^{\circ}C\;to\;600^{\circ}C$ and had rutile phase over $700^{\circ}C$ at 1mole% $Nb_2O_5$ additive. After $TiO_2-Nb_2O_5$ sol retained low viscosity with normal chain structure for a long time, its viscosity increased fast with network structure. DTA properties of gel powder had endothermic reaction due to evaporation of propanol and water about $78^{\circ}C$, had exothermic reaction due to propanol combustion about $290^{\circ}C$ and had exothermic reaction due to changing of $TiO_2$ phase about $640^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.36 no.11
• /
• pp.1211-1216
• /
• 1999

TiO2 thin films were prepared by reactive magnetron sputtering on glass substrate and subjected into investigation about their hydrophilic properties. Varing Ar/O2 ration and post annealing at 50$0^{\circ}C$ for 12h anatase and rutile phases of TiO2 films were obtained. Hydrophilic properties were evaluated by determination of contact angle of water droplet on TiO2 surface. On as-annealed TiO2 films water droplet spreaded widely with ~0$^{\circ}$contact angle. Sonication(60 Hz, 28kHz 40kHz) and following dark room treatments turned these hydrophilic TiO2 films into hydrophobic state. All of hydrophobic films were converted recersibly into their original state after UV illumination. Hydrophobic states of anatase films were saturated after sonication and remain same during dark room treatment. But it was found that the conversion into hydrophobic state of rutile films progressed. further after sonication. Therefore it was concluded that Ti3+/Ti+4 ratio is the key to determine hydrophilicity of TiO2 surface so that different surface structure of polymorphs could lead to unique characteristics.