• Corrosion Science and Technology
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• 제22권3호
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• pp.193-200
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• 2023

Titanium alloy (grade-4) is commonly used in industrial and medical applications. To improve its corrosion resistance and biocompatibility for medical use, it is necessary to form a titanium oxide film. In this study, the morphology of the oxide film formed by anodizing Ti-grade 4 using different electrolytes was analyzed. Wetting properties before and after surface modification with SAM coating were also observed. Electrolytes used were categorized as A, B, and C. Electrolyte A consisted of 0.3 M oxalic acid and ethylene glycol. Electrolyte B consisted of 0.1 M NH₄F and 0.1 M H₂O in ethylene glycol. Electrolyte C consisted of 0.07 M NH₄F and 1 M H₂O in ethylene glycol. Samples B and C exhibited a porous structure, while sample A formed a thickest oxide film with a droplet-like structure. AFM analysis and contact angle measurements showed that sample A with the highest roughness exhibited the best hydrophilicity. After surface modification with SAM coating, it displayed superior hydrophobicity. Despite having the thickest oxide film, sample A showed the lowest insulation resistance due to its irregular structure. On the other hand, sample C with a thick and regular porous oxide film demonstrated the highest insulation resistance.

• 한국표면공학회지
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• 제34권1호
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• pp.25-32
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• 2001

$TiB_2$ ceramics were oxidized at 800, 900 and $1000^{\circ}C$ in air for 40 hr, and their oxidation property was investigated using TGA, XRD, SEM and EPMA. The oxidation resistance decreased with an increase in oxidation temperature. The scale was essentially composed of $TiO_2$ only. $B_2$$O_3$ formed during oxidation escaped from the $TiO_2$ oxide scale owing to its high vapor pressure. This made the oxide scale highly porous and thick. The oxidation reaction was mainly governed by the inward transport of oxygen.$ TiO_2$ existing at the outermost scale grew into peculiarly shaped blades, as the reaction progressed.

• 한국재료학회지
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• 제13권7호
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• pp.436-441
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• 2003

The characteristics of <112> orientation were studied for the $TiO_2$thin films, which were prepared on the glass by CVD (chemical vapor deposition) at various substrate temperatures. It was confirmed that $TiO_2$ films exhibited <112>-preferred orientation in a specific temperature range. Although $TiO_2$polycrystalline film grown deposited at relatively low temperature showed the growth of random directions, the <112>-preferred orientation was gradually developed with increasing deposition temperature. According to exhibit higher degree of <112>-preferred orientation, $TiO_2$thin film showed porous surface morphology, well-developed columnar structure, and deeper voids resulted from non-aggregation of columns were observed. In addition, transmittance was enhanced. Therefore, the growth of $TiO_2$with <112>-preferred orientation is suitable for glass coating because of predominance of photocatalytic efficiency and transmittance.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1999년도 추계학술발표강연 및 논문개요집
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• pp.183-183
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• 1999

Slurry sol(30at% anatase TiO$_2$)을 이용하여 스핀코팅으로 유리기판에 TiO$_2$박막을 제조하였다. 박막의 두께는 코팅주기의 횟수로 조절하였다. 한 코팅주기는 스핀코팅, 건조, 열처리를 포함한다. 박막의 반응성은 막 위에서의 자외선강도가 0.4mW/$\textrm{cm}^2$인 조건에서 벤젠기체의 광분해 속도를 통해 조사하였다. 박막의 두께가 증가할수록 표면적인 증가로 인해 반응성은 증가하였으며, 4$\mu\textrm{m}$정도이상의 두께에서 반응성은 더 이상 증가되지 않았다. porous한 TiO$_2$박막은 비교적 넓은 유효 표면적을 가지고 있으며, 그것은 두께증가에 따라 반응속도를 결정하는 결과를 낳았다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.230-231
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• 2006

In this paper, we examined effects by the binder in manufacturing titanium dioxide film for dye sensitized solar cell. Binder(PEG and PEO) was added the amount of 10-40wt% to commercial $TiO_2$ (P25), Respectively. All of $TiO_2$ film was showed porous structure owing to the addition of binders. But the difference of film's porosity could not be confirmed. The transmittance of $TiO_2$ film was decreased with the increase of binder's amount, generally. In case of 20wt%, however. The transmittance of $TiO_2$ films was showed the highest value.

• 공업화학
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• 제28권6호
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• pp.601-606
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• 2017

금속 표면처리의 대표적인 기술인 양극산화를 통하여 일차원 나노구조 금속 산화물을 형성할 수 있다. 여러 가지 금속 산화물 중에 기능성이 뛰어난 $TiO_2$에 대한 관심의 증대로 $TiO_2$ 나노 튜브를 이용한 연구가 많이 이루어지고 있다. 본 총설논문에서는 지금까지 연구되어 밝혀진 $TiO_2$ 나노 튜브가 형성원리에 대한 해설논문으로 전기화학적 측면에서의 양극 산화 공정에 대한 이해를 통하여 나노 튜브 형성을 위한 전기적 조건, 화학적 조건, 물리적 조건에 대하여 다루었다. 특히 $TiO_2$ 나노 튜브 성장의 핵심 요소인 산화물의 형성과 에칭의 평형관계, 다공성 구조의 형성 원인을 다루었다. 나아가 전해질 조건에 따른 $TiO_2$ 나노 튜브의 형태학적 고찰을 함으로써 향후 양극 산화를 통한 $TiO_2$ 나노 튜브 응용에 관한 연구를 하는 연구자에게 이해하기 쉽게 설명하고자 하였다.

• Korean Chemical Engineering Research
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• 제57권2호
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• pp.185-197
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• 2019

Deactivation of porous photocatalytic materials was studied using three types of microstructured particles: macroporous titania particles, titania microspheres, and porous silica microspheres containing CNTs and $TiO_2$ nanoparticles. All particles were synthesized by emulsion-assisted self-assembly using micron-sized droplets as micro-reactors. During repeated cycles of the photocatalytic decomposition reaction, the non-dimensionalized initial rate constants (a) were estimated as a function of UV irradiation time (t) from experimental kinetics data, and the results were plotted for a regression according to the exponentially decaying equation, $a=a_0\;{\exp}(-k_dt)$. The retardation constant ($k_d$) was then compared for macroporous titania microparticles with different pore diameters to examine the effect of pore size on photocatalytic deactivation. Nonporous or larger macropores resulted in smaller values of the deactivation constant, indicating that the adsorption of organic materials during the photocatalytic decomposition reaction hinders the generation of active radicals from the titania surface. A similar approach was adopted to evaluate the activation constant of porous silica particles containing CNT and $TiO_2$ nanoparticles to compare the deactivation during recycling of the photocatalyst. As the amount of CNTs increased, the deactivation constant decreased, indicating that the conductive CNTs enhanced the generation of active radicals in the aqueous medium during photocatalytic oxidation.

• 한국재료학회지
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• 제20권7호
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• pp.345-350
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• 2010

For the present paper, we prepared MgO/MWCNT/$TiO_2$ photocatalyst by using multi-walled carbon nanotubes (MWCNTs) pre-oxidized by m-chlorperbenzoic acid (MCPBA) with magnesium acetate tetrahydrate $(Mg(CH_2COO)_2\cdot4H_2O)$ and titanium n-butoxide $(Ti\{OC(CH_3)_3\}_4)$ as magnesium and titanium precursors. The prepared photocatalyst was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. The decomposition of methylene blue (MB) solution was determined under irradiation of ultraviolet (UV) light. The XRD results show that the MgO/MWCNT/$TiO_2$ photocatalyst have cubic MgO structure and anatase $TiO_2$ structure. The porous structure and the $TiO_2$ agglomerate coated on the MgO/MWCNT composite can be observed in SEM images. The Mg, O, Ti and C elements can be also observed in MgO/MWCNT/$TiO_2$ photocatalyst from EDX results. The results of photodegradation of MB solution under UV light show that the concentration of MB solution decreased with an increase of UV irradiation time for all of the samples. Also, the MgO/MWCNT/$TiO_2$ photocatalyst has the best photocatalytic activity among these samples. It can be considered that the MgO/MWCNT/$TiO_2$ photocatalyst had a combined effect, the effect of MWCNT, which could absorb UV light to create photoinduced electrons $(e^-)$, and the electron trapping effect of MgO, which resulted in an increase of the photocatalytic activity of $TiO_2$.

• Korean Membrane Journal
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• 제3권1호
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• pp.69-74
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• 2001

Films of TiO$_2$/SiO$_2$ were deposited on the inner surface of the porous glass support tubes by decomposition of tetraisopropyl titanate (TIPT) and tetraethyl orthosilicate (TEOS) at atmospheric pressure. Dense and hydrogen -permselective membranes were formed at 400-600$\^{C}$. The permeation rates of H$_2$ through the membrane at 600$\^{C}$ were 0.2-0.4 ㎤(STP)/min-㎠ atm and H$_2$:N$_2$permeation ratios were above 1000. The permeation properties of the membranes were investigated at various deposition temperatures and TIPT/TEOS concentrations. Decomposition of TIPT alone at temperatures above 400$\^{C}$ produced porous crystalline TiO$_2$ films and they were not H7-selective. Decomposition of TEOS produced H$_2$-permeable SiO$_2$ films at 400-600$\^{C}$ but film deposition rate was very low. Addition of TIFT to the TEOS stream significantly accelerated the deposition rate and produced highly H$_2$-selective films. Increasing the TIPT/TEOS concentration ratio increased the deposition rate. The TiO$_2$/SiO$_2$ membranes formed at 600 $\^{C}$ have the permeation properties comparable to those of SiO$_2$ membranes produced from TEOS.

• 한국세라믹학회지
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• 제29권9호
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• pp.739-749
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• 1992

The sols prepared by dialyzing solutions, in which the hydrolyzed precipitates of TEOT or directly Ti(OC3H7)4 were resolved, were the nanoparticulate sol with the average particle size less than 7 nm and the anatase crystal phase. In the pH range of 1.5 to 2.9, the particle size of the nanoparticulate TiO2 sols (0.09 mol/ι) increased gradually upto 15 nm~26nm with the increase of pH in the initial aging state but the sols were transparent all the time, and stable without growin any more after 30 days. When the slipcasted porous alumina tubes were coated by the sol-gel dipping method, the minimum particle size and the aging time for forming the coated gel layer at the given pH were optimized. For obtaining the very thin crack-free and reproducible membrane coating, the use of a nanoparticulate TiO2 sol (0.09 mol/ι) aged for about 30 dyas at pH=2.0 was found to be the best.