• Journal of the Korean Ceramic Society
• /
• v.42 no.7 s.278
• /
• pp.461-468
• /
• 2005

Transparent TiO$_{2}$ sols were prepared by hydrothermal synthesis to heat Ti precursor solutions, from Ti hydroxides obtained with neutralizing aqueous TiOCl$_{2}$ solutions having various concentrations of NaCI by aqueous NaOH solution, in the autoclave at 120$^{\circ}C$ The photocatalytic abilities of glass beads coated with the sol for gaseous benzene were evaluated. As a result, it was found that due to the increase of brookite phase in TiO$_{2}$ by controlling the concentration of Na ion the optical absorption of TiO$_{2}$ increases toward long wavelength but that in the area of short wavelength becomes relatively low and consequently the photocatalytic performance of TiO$_{2}$ thin film for benzene gas rather decreases, compared to that of composite film of anatase and brookite phases. These results suggest that in order for coated TiO$_{2}$ thin film to have high dissociation performance for benzene gas it is effective to form anatase and brookite phases compositely in TiO$_{2}$.

• Journal of Environmental Science International
• /
• v.12 no.10
• /
• pp.1071-1077
• /
• 2003

The aim of this study is, firstly, to find out what kinds of inorganic species are produced in the photocatalytic oxidation of ammonium-nitrogen containing water and, secondly, to seek the influence of anion for the photocatalytic oxidation of ammonium contained compounds. The photoenergy above 3 eV(λ <415 nm) was effectively absorbed by TiO$_2$ and TiO$_2$/polymer was used to be oxidized NH$_4$-N in wastewater to NO$_3$-N. Existing the anion as Cl$\^$-/, the rate of photocatalytic oxidation decreased regardless of other condition. This result showed that the chloride ions reduced the rate of oxidation by scavenging oxidizing radical species as OH$\^$-/ and OCl$\^$-/. Some of the added ion might have blocked the active sites of the catalyst surface, thus deactivated the catalyst.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.03a
• /
• pp.207-207
• /
• 2003

최근 광촉매 재료로 각광받고 있는 TiO$_2$는 band gap 에너지가 3.0-3.2eV로 자외선 영역과 일부 가시광선 영역에서 활성을 갖는 것으로 알려져 있다. 따라서 용액 중에 결정화 및 안정화 되어있는 TiO$_2$의 band gap 에너지를 낮춘다면 가시광 영역의 광반응을 얻을 수 있다. 이에 본 연구는 G. Sato등이 제안한 방법으로 TiO$_2$ sol을 제조할 때 band gap 에너지를 낮추고자 천이 금속원소를 첨가하여 복합 및 담지된 TiO$_2$계 복합 sol을 합성하고자 하였다 출발원료는 TiC1$_4$를 가수분해하여 제조한 TiOCl$_2$에 천이금속원소인 V, Cr, Fe, Ni, Nb 등의 chloride 화합물을 첨가하여 중화 및 세척과정을 거친 후, 과산화수소수에 용해하여 전구체 용액인 titania peroxo용액을 제조하였다 제조된 전구체 용액은 온도와 시간을 변수로 각각 열처리하여 TiO$_2$계 복합 sol을 합성하였다. 제조된 시편은 X-선 회절 분석, 투과전자현미경, particle size analyzer, ζ-potential analyzer 및 UV-VIS Spectrometer 통을 이용하여 천이금속 첨가에 따른 TiO$_2$계 복합 sol의 형성과정과 특성변화를 관찰하였다.

• Journal of the Korean Ceramic Society
• /
• v.38 no.4
• /
• pp.331-336
• /
• 2001

TiOCl$_2$수용액과 암모니아수의 반응으로부터 얻은 titanium hydroxide 침전물에 대해 각각 NaOH 또한 HCl 처리를 통하여 비교적 낮은 온도에서 결정성이 우수하고, 높은 비표면적을 갖는 결정형 TiO$_2$나노분말을 제조하였다. 저온처리 조건을 변화시킴으로써 TiO$_2$분말의 결정상과 입자 모양을 제어할 수 있었는데, NaOH 처리한 다음 산처리한 분말에는 아나타제와 루틸상이 함께 형성되었으며 구형입자와 긴 스핀들 모양의 입자들로 이루어져 있었고, 비등수 처리 시에는 열처리를 통해 아나타제상의 구형 입자들을 얻을 수 있었다. Titanium hydroxide를 0.1M과 0.5M에 산처리한 분말은 모두 아나타제상을 나타내었는데, 0.1M의 분말은 구형입자로 이루어져 있었고, 0.5M의 경우는 대부분 구형입자들로 이루어져 있었지만 스핀들 모양의 입자들도 소량 관찰되었으며, 2M에 산처리한 분말은 루틸상으로서 모두 스핀들 모양의 입자들로 이루어져 있었고, 제조된 분말의 비표면적은 약 240-250$m^2$/g을 나타내었다.

• Journal of the Korean Ceramic Society
• /
• v.37 no.7
• /
• pp.700-704
• /
• 2000

Titanium hydroxide precipitate was obtained by the reaction of 0.5M TiOCl2 and 5M NH4OH solutions, then anatase TiO2 powder with nanotubes was prepared by the digestion of the heat-treated powder in 5M NaOH solution. Nanotube was formed for anatase TiO2 powder digested at 10$0^{\circ}C$ above, and the amount and length of nanotube increased with the digestion temperature. In the case of the powder digested at 15$0^{\circ}C$ for 12h, the formed nanotube was 100~150nm in length, 10~20 nm in diameter, and 2nm in width of the walls on both sides of the nanotube. The powder digested at 15$0^{\circ}C$ for 12h showed the highest specific surface area of 270$m^2$/g.

• Journal of the Korean Ceramic Society
• /
• v.39 no.11
• /
• pp.1017-1022
• /
• 2002

$(Ba_{1-x}Ca_x)(Ti_{1-y}Zr_y)O_3(BCTZ)$ powders for the Ni-electrode Multilayer Ceramic Capacitor(MLCC) were synthesized via hydrothermal treatment using mixed aqueous solutions of $BaCl_2{\cdot}2H_2O,\Ca(NO_3)2{\cdot}4H_2O,\ ZrOCl_2{\cdot}8H_2O$ and $TiCl_4$. Two component and three component systems were also extensively studied for basic data. BT, CT and BZ powders were crystalline but CZ was determined to be amorphous under the same synthetic condition. In BTZ system, Zr and Ti were completely soluble and Ca would be substituted for Ba up to ∼6 mol% in BCT. The submicron-sized $(Ba_{0.95}Ca_{0.05})(Ti_{0.80}Zr_{0.20})O_3$ powder of the target composition was successfully synthesized at $150{\circ}$ for 12h.

• Journal of the Korean Ceramic Society
• /
• v.53 no.3
• /
• pp.325-331
• /
• 2016

Anatase particles of titanium dioxide were prepared from $TiCl_4$ aqueous solution by using an electro-dialysis [ED] process. For the preparation of an aqueous solution of $TiCl_4$ precipitates, $TiCl_4$ liquid frozen in ice was transferred to a neck flask and then hydrolyzed using deionized [DI] $H_2O$. During the hydrolysis of the $TiCl_4$ solution at $0^{\circ}C$, a slurry solution of $TiOCl_2$ was obtained and the color changed from red to orange. The ED process was applied for the removal of chlorine content in the slurry solution. Two kinds of hydrolyzed slurry solution with lower [$Ti^{4+}$] and higher [$Ti^{4+}$] were sampled and the ED process was applied for the samples according to the removal time of [$Cl^-$]. With de-chlorination, the solution status changed from sol to gel and the color quickly changed to blue. Finally, white crystalline powders were formed and the phase was confirmed by XRD to be anatase crystallites. The morphology of the hydrous titania particles in the solution was observed by FE-SEM. The hydrous titania particles were nano-crystalline, and easily coagulated with drying.

• Restorative Dentistry and Endodontics
• /
• v.42 no.1
• /
• pp.54-59
• /
• 2017

Objectives: The purpose of this study was to compare the antibacterial activity of urushiol against Enterococcus faecalis (E. faecalis) to that of NaOCl. Materials and Methods: The canals of thirty two single rooted human teeth were instrumented with Ni-Ti files (ProTaper Next X1, X2, X3, Dentsply). A pure culture of E. faecalis ATCC 19433 was prepared in sterile brain heart infusion (BHI) broth. The teeth were submerged in the suspension of E. faecalis and were incubated at $37^{\circ}C$ for 7 days to allow biofilm formation. The teeth were randomly divided into three experimental groups according to the irrigant used, and a negative control group where no irrigant was used (n = 8). Group 1 used physiologic normal saline, group 2 used 6% NaOCl, and group 3 used 10 wt% urushiol solution. After canal irrigation, each sample was collected by the sequential placement of 2 sterile paper points (ProTaper NEXT paper points, size X3, Dentsply). Ten-fold serial dilutions on each vials, and 100 µL were cultured on a BHI agar plate for 8 hours, and colony forming unit (CFU) analysis was done. The data were statistically analyzed using Kruskal-Wallis and Mann-whitney U tests. Results: Saline group exhibited no difference in the CFU counts with control group, while NaOCl and urushiol groups showed significantly less CFU counts than saline and control groups (p < 0.05). Conclusions: The result of this study suggests 10% urushiol and 6% NaOCl solution had powerful antibacterial activity against E. faecalis when they were used as root canal irrigants.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.360-363
• /
• 2009

In order to improve the overall power conversion efficiency, it is very important to reduce the interface resistance of dye-sensitized solar cells (DSSCs). In this approach, tiny $TiO_2$ nanoparticles with the primary size of 10~20nm were synthesized and deposited between FTO glass and preformed $TiO_2$ layer by $TiOCl_2$ treatment, and also Pt catalysts were deposited on the counter electrode by both ion-sputter and thermal deposition to reduce the electrolyte-counter electrode interface resistance. The influence of these processes on the performace of DSSCs were discussed in terms of fill factor, short circuit current, and conversion efficiency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2006.12a
• /
• pp.123-125
• /
• 2006

The $TiO_2$ sol was prepared hydrothermally in an autoclave from aqueous $TiOCl_2$ solutions as a starting precursor. Hollow fibers were obtained when the sol-gel-derived $TiO_2$ sol was treated chemically with a NaOH solution and subsequently heated in the autoclave under various conditions. A systematic analysis of the influence of different NaOH concentrations on the formation of nanotubes was carried out. The details of the nanotubular structure were investigated by using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). From the TEM images, the outer and the inner diameters of the tubes were measured to be about 8 and 4 nm, respectively, the lengths were measured to be several hundreds of nanometers.