A TiO2/CNT nanohybrid photocatalyst is synthesized via sol-gel route, with titanium (IV) isopropoxide and multi-walled carbon nanotubes (MWCNTs) as the starting materials. The microstructures and phase constitution of the nanohybrid TiO2/CNT (0.005wt%) samples after calcination at 450oC, 550oC and 650oC in air are compared with those of pure TiO2 using field-emission scanning electron microscopy and X-ray diffraction, respectively. In addition, the photocatalytic activity of the nanohybrid is compared with that of pure TiO2 with regard to the degradation of methyl orange under visible light irradiation. The TiO2/CNT composite exhibits a fast grain growth and phase transformation during calcination. The nanocomposite shows enhanced photocatalytic activity under visible light irradiation in comparison to pure TiO2 owing to not only better adsorption capability of CNT but also effective electron transfer between TiO2 and CNTs. However, the high calcination temperature of 650oC, regardless of addition of CNT, causes a decrease in photocatalytic activity because of grain growth and phase transformation to rutile. These results such as fast phase transformation to rutile and effective electron transfer are related to carbon doping into TiO2.

In this study, TiO2 powders are synthesized from ammonium hexafluoride titanate (AHFT, (NH4)2TiF6) as a precursor by heat treatment. First, we evaluate the physical properties of AHFT using X-ray diffraction (XRD), particle size analysis (PSA), thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FESEM). Then, to prepare the TiO2 powders, is heat-treated at 300-1300oC for 1 h. The ratio of anatase to rutile phase in TiO2 is estimated by XRD. The anatase phase forms at 500oC and phase transformation to the rutile phase occurs at 1200oC. Increase in the particle size is observed upon increasing the reaction temperature, and the phase ratio of the rutile phase is determined from a comparison with the calculated XRD data. Thus, we show that anatase and rutile TiO2 powders could be synthesized using AHFT as a raw material, and the obtained data are utilized for developing a new process for producing high-quality TiO2 powder.

A novel nanocomposite LDPE film with UV protective properties was developed for active packaging applications. Initially, undoped and Mn-doped TiO2 nanoparticles (NPs) were synthesized by the sol-gel method and the resulting particles were characterized. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed an agglomerated nature and spherical morphology. X-ray diffraction (XRD) studies indicated that all products were crystalline and in the form of rutile. The reflectance spectrum of undoped TiO2 NPs demonstrated a characteristic sharp edge at 410 nm. Subsequently, nanocomposite (NC) LDPE samples were prepared with the NPs by solvent precipitation followed by film casting. The optical and thermal properties of the NC samples were investigated. Incremental increases in Mn concentration from 0.25 mol % to 1.00 mol % were associated with progressive decreases in light transmission in the UV region. The melting and maximum decomposition temperatures of all NCs were 107 and 442-449 °C, respectively. The UV protective LDPE-based NC films exhibited superior photostability. Absorption in the FTIR spectra at 1716 and 1734 cm-1 changed after 4-wk exposure to UV for all film samples as a consequence of photodegradation. Finally, the photooxidation of perilla oil was assessed as an example of a UV protective packaging application. After 12 days, protection with 1.00 mol% Mn-doped TiO2-LDPE was associated with a gradual increase in PV, while protection with TiO2-LDPE was associated with a significant increase and protection with the control treatment was associated with a dramatic increase in PV. Hence, a 1.00 mol% Mn-doped TiO2-LDPE NC showed promise for UV shielding packaging applications.

In order to reuse the photocatalyst and enhance the photolysis efficiency, we have used atmospheric pressure dielectric barrier discharge (APDBD) to clean and activate TiO2 powder. The photocatalytic activity of the TiO2 powder before and after APDBD treatment was evaluated by the degradation of methylene blue (MB) in aqueous solution. The apparent reaction rate constant of photolysis of the first sample of reused TiO2 cleaned by APDBD improved to a level up to 0.32h- 1 higher than the 30 % value of the initial TiO2 powder. As the number of photolysis reactions and APDBD cleanings increased, the apparent rate constants gradually decreased; however, the fourth photolysis reaction still showed a value that was greater than 10% of the initial value. In addition, APDBD treatment enhanced the process by which TiO2 effectively adsorbed MB at every photolysis stage.

국내 대기오염물질 중 도로공간에서 발생하는 오염원은 약 34.4%로 다소 많은 비중을 차지하고 있다. 이러한 대기오염을 정화하는 방법의 한 예로는 TiO2의 광촉매 작용을 이용하여 도로공간에서 발생하는 오염물질 제거방법이 있다. 현재 국내･외의 다양한 분야에서 광촉매를 활용한 연구가 활발히 진행 중이 며, 그 중 토목분야에서는 배기가스에 인한 도로 오염물질 배출을 저감하기 위한 연구가 진행되고 있다. TiO2는 빛을 이용하여 광화학 반응을 촉진시키는 물질로서 활성도가 높고 화학적으로 안정적이며, 인체 에 무해하여 대기정화, 수질정화, 셀프클리닝(self-cleaning), 초 친수성 제품 등 다양한 활용분야에 사 용되고 있다. 하지만 TiO2는 백색 분말로 이루어진 특성이 있어, 바람에 흩어지거나 물에 혼합되면 회수 가 어렵고 손실의 우려가 크다. 이에 대해 광촉매 분말의 고정화가 필요한 동시에 활성에 영향을 주는 비 표면적 확보와 바인더의 내구성 및 무해성이 요구된다. 따라서 본 연구에서는 1액형 광촉매를 도포한 아 스팔트 포장체의 광활성 거동을 파악하기 위한 기초연구를 수행하였으며, 광촉매 시료는 국내 B사의 광 촉매 물질을 수용액 중에서 마이셀화 시키는 음전하성 계면활성제와 무기질 바인더가 혼합된 1액형 TiO2 혼합물을 사용하였다. 본 실험에서는 수용성 미디움에서 표면의 광촉매 활성 시험 – 메틸렌 블루 분해법(KS L ISO 10678)과 노면의 미끄럼저항성 시험방법(KS F 2375)를 진행하였다. 메틸렌 블루 분해법을 통해 아스팔트 시편에 도포된 TiO2의 용량에 따른 광분해율의 변화를 파악 할 수 있었으며, 약 400g/m2 의 적정 도포량을 도출 하였다. 또한 광촉매 수용액이 도포된 아스팔트 표층의 미끄럼 저항성 측정 결과, 광촉매가 도포되지 않 은 시편과 비교하여 미끄럼 저항성이 1~2% 감소하는 것으로 나타났다. 이는 광촉매가 아스팔트 포장체의 미끄럼 저항성에 미치는 영향이 미비하다는 것을 의미한다.

When a single inorganic precursor is used for the synthesis of a sol-gel coating, there is a problem of cracking on the surface of coating layer. In order to solve this problem of surface cracking, we synthesized inorganic-organic coatings that have hybrid properties of inorganic and organic materials. Sols of various ratios (1:0.07, 0.2, 0.41, 0.82, 1.64, 3.26, 6.54, 13.2) of an inorganic precursor of Tetrabutylorthotitanate (Ti(OBu)4, TBOT) and an organic precursor of γ-Methacryloxy propyltrimethoxysilane (MAPTS) were prepared and coated on stainless steels (SUS316L) by dip coating method. The binding structure and the physical properties of the synthesized coatings were analyzed by FT-IR, FE-SEM, FIB (Focused Ion Beam), and a nano-indenter. Dynamic polarization testing and EIS (electrical impedance spectroscopy) were carried out to evaluate the micro-defects and the corrosion properties of the coatings. The prepared coatings show hybrid properties of inorganic oxides and organic materials. Crack free coatings were prepared when the MAPTS ratio was above a critical value. As the MAPTS ratio increased, the thickness and the corrosion resistance increased, and the hardness decreased.

선박 및 해양구조물에서의 생물학적 오손을 방지하기 위하여 나노크기의 MnOx-WO₃-TiO₂ 분말을 졸겔법으로 합성하여 특성을 제어하였고, 입자의 결정과 미세구조 등 분체특성 평가를 실시하였다. 자기마모형 방오도료의 안료에 적용하기 위하여 수지에 첨가 된 TiO₂계 나노분말 안료의 함량에 따른 표면특성 및 방오성능을 확인하였다. TiO₂계 안료의 분체특성으로 비표면적은 약 90 m²/g, 입자 크기는 약 100 ~ 150 nm을 보였다. 텅스텐 산화물은 망간산화물과 티타늄산화물과 상관관계를 통해, 삼원계 분체가 분체특성 및 표면특성이 우수하였다. 망간산화물의 첨가는 독특한 산화환원 특성으로 인하여 방오성능을 증가시키고, 텅스텐 산화물은 안료의 분체특성을 향상시킴으로, 안료와 수지의 비율을 조절하여 분산성, 표면특성 및 방오성능을 제어하였다. 그 결과로, 분산성 및 표면특성에 있어서 1, 5 wt. % 안료가 첨가된 것이 일부 우수하였으나, 5개월 동안의 해상침지시험에서는 2 wt. % 함유된 시편이 높은 방오성능을 보여 해양구조물의 방오안료 적용가능성을 확인하였다.

We demonstrate the electrochromic properties of TiO2 nanotubes prepared by an anodization process and investigate the effects of heat treatment and viologen incorporation on them. The morphology and crystal structure of anodized TiO2 nanotubes are investigated by scanning electron microscopy and X-ray diffraction. As-formed TiO2 nanotubes have straight tubular layers with an amorphous structure. As the annealing temperature increases, the anodized TiO2 nanotubes are converted to the anatase and rutile phases with some cracks on the tube surface and irregular morphology. Electrochemical results reveal that amorphous TiO2 nanotubes annealed at 150°C have the largest oxidation/ reduction current, which leads to the best electrochromic performance during the coloring/bleaching process. Viologenanchored TiO2 nanotubes show superior electrochromic properties compared to pristine TiO2 nanotubes, which indicates that the incorporation of a viologen can be an effective way to enhance the electrochromic properties of TiO2 nanotubes.

We prepared polymethyl methacrylate (PMMA) beads with a particle size of 80 nm to improve the energy conversion efficiency (ECE) by increasing the effective surface area and the dye absorption ability of the working electrodes (WEs) in a dye sensitized solar cell (DSSC). We prepared the TiO2 layer with PMMA beads of 0.0~1.0 wt%; then, finally, a DSSC with 0.45 cm2 active area was obtained. Optical microscopy, transmission electron microscopy, field emission scanning electron microscopy, and atomic force microscopy were used to characterize the microstructure of the TiO2 layer with PMMA. UV-VIS-NIR was used to determine the optical absorbance of the WEs with PMMA. A solar simulator and a potentiostat were used to determine the photovoltaic properties of the PMMA-added DSSC. Analysis of the microstructure showed that pores of 200 nm were formed by the decomposition of PMMA. Also, root mean square values linearly increased as more PMMA was added. The absorbance in the visible light regime was found to increase as the degree of PMMA dispersion increased. The ECE increased from 4.91% to 5.35% when the amount of PMMA beads added was increased from 0.0 to 0.4 wt%. However, the ECE decreased when more than 0.6 wt% of PMMA was added. Thus, adding a proper amount of PMMA to the TiO2 layer was determined to be an effective method for improving the ECE of a DSSC.

The morphology, crystal structure and size of aerosol nanoparticles generated by erosion of electrodes made of different materials (titanium, copper and aluminum) in a multi-spark discharge generator were investigated. The aerosol nanoparticle synthesis was carried out in air atmosphere at a capacitor stored energy of 6 J, a repetition rate of discharge of 0.5 Hz and a gas flow velocity of 5.4 m/s. The aerosol nanoparticles were generated in the form of oxides and had various morphologies: agglomerates of primary particles of TiO2 and Al2O3 or aggregates of primary particles of Cu2O. The average size of the primary nanoparticles ranged between 6.3 and 7.4 nm for the three substances studied. The average size of the agglomerates and aggregates varied in a wide interval from 24.6 nm for Cu2O to 46.1 nm for Al2O3.

TiO2 nanoparticles were synthesized by a sol-gel process using titanium tetra isopropoxide as a precursor at room temperature. Ag-doped TiO2 nanoparticles were prepared by photoreduction of AgNO3 on TiO2 under UV light irradiation and calcinated at 400 oC. Ag-doped TiO2 nanoparticles were characterized for their structural and morphological properties by Xray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The photocatalytic properties of the TiO2 and Ag-doped TiO2 nanoparticles were evaluated according to the degree of photocatalytic degradation of gaseous benzene under UV and visible light irradiation. To estimate the rate of photolysis under UV (λ = 365 nm) and visible (λ ≥ 410 nm) light, the residual concentration of benzene was monitored by gas chromatography (GC). Both undoped/doped nanoparticles showed about 80 % of photolysis of benzene under UV light. However, under visible light irradiation Ag-doped TiO2 nanoparticles exhibited a photocatalytic reaction toward the photodegradation of benzene more efficient than that of bare TiO2. The enhanced photocatalytic reaction of Ag-doped TiO2 nanoparticles is attributed to the decrease in the activation energy and to the existence of Ag in the TiO2 host lattice, which increases the absorption capacity in the visible region by acting as an electron trapper and promotes charge separation of the photoinduced electrons (e−) and holes (h+). The use of Ag-doped TiO2 nanoparticles preserved the option of an environmentally benign photocatalytic reaction using visible light; These particles can be applicable to environmental cleaning applications.

10 wt.% and 20 wt.%Li-TiO2 composite powders are synthesized by a sol-gel method using titanium isopropoxide and Li2CO3 as precursors. The as-received amorphous 10 wt.%Li-TiO2 composite powders crystallize into the anatase-type crystal structure upon calcination at 450oC, which then changes to the rutile phase at 750oC. The asreceived 20 wt%Li-TiO2 composite powders, on the other hand, crystallize into the anatase-type structure. As the calcination temperature increases, the anatase TiO2 phase gets transformed to the LiTiO2 phase. The peaks for the samples obtained after calcination at 900oC mainly exhibit the LiTiO2 and Li2TiO3 phases. For a comparison of the photocatalytic activity, 10 wt.% and 20 wt.% Li-TiO2 composite powders calcined at 450oC, 600oC, and 750oC are used. The 20 wt.%Li-TiO2 composite powders calcined at 600oC show excellent efficiency for the removal of methylorange

The potential use of UV-TiO2 photocatalytic oxidation absorbent reactor in the removal of gaseous formaldehyde was studied. This study was conducted inside a bench-type circulation reactor chamber at ambient air conditions. PCO (Photocatalytic Oxidaion) degradation test for formaldehyde was done repeatedly and the average was reported. It was evident that photocatalytic oxidation was proven to be an effective method to control indoor air pollutants, like formaldehyde in indoor air. However, by-products are produced in the case of formaldehyde degradation also CO2, CO, H2O and formic acid are produced. These by-products can inhibit the active site of the photocatalyst. Thus, addition of adsorbent succeeding the PCO-TiO2, acts as a secondary treatment wherein produced by-products from the degradation and unreacted HCHO will adhere to the surface of the adsorbent. In this study, synthetic zeolite and activated carbon pellets were used to control of by-products of formaldehyde. PCOTiO2 degradation alone achieves 86% for a period of 60 minutes. Addition of adsorbent improves the removal efficiency achieving 90% and 96% using activated carbon pellet and zeolite, respectively.

To improve photocatalytic efficiency, graphene/Ag/TiO2 nanotube catalyst was synthesized, and its surface characteristics and photocatalytic activity investigated. For deposition of Ag nanoparticles on the TiO2 nanotubes, a polymer compound containing CH3COOAg/poly(Llactide) was utilized, and the silver particles were precipitated by reducing the silver ions during the annealing process. Graphene deposition on the Ag/TiO2 nanotubes was achieved using an electrophoretic deposition process. Based on the dye degradation results, it was determined that the photocatalytic efficiency was significantly affected by deposition of silver particles and graphene on the TiO2 catalyst. Highly efficient destruction of the dye was obtained with the new graphene/Ag/TiO2 nanotube photocatalyst. This may be attributed to a synergistic effect of the graphene and Ag nanoparticles on the TiO2 nanotubes.

In this study, we demonstrate the photoelectrochromic devices composed of TiO2 and WO3 nanostructuresprepared by anodization method. The morphology and the crystal structure of anodized TiO2 nanotubes and WO3 nan-oporous layers are investigated by SEM and XRD. To fabricate a transparent photoelectrode on FTO substrate, a TiO2nanotube membrane, which has been detached from Ti substrate, is transferred to FTO substrate and annealed at 450°Cfor 1 hr. The photoelectrode of TiO2 nanotube and the counter electrode of WO3 nanoporous layer are assembled andthe inner space is filled with a liquid electrolyte containing 0.5 M LiI and 5 mM I2 as a redox mediator. The propertiesof the photoelectrochromic devices is investigated and Pt-WO3 electrode system shows better electrochromic perform-ance compared toWO3 electrode.

용액-확산 메커니즘에 의해 결정되는 기존의 고분자에서와는 달리, 촉진수송은 투과도와 선택도를 동시에 향상시킬 수 있는 기술이다. 본 연구에서는 은 나노입자, 폴리비닐피롤리돈, 7,7,8,8-테트라시야노퀴노디메탄으로 구성된 촉진수송 올레핀 분리막에 있어서, 메조기공 티타늄산화물(m-TiO2)에 대한 영향을 연구하였다. 특히 메조기공 티타늄산화물은 폴리비닐클로라이 드-g-폴리옥시에틸렌 메타크릴레이트 가지형 공중합체를 템플레이트로 하여 쉽고 대량 생산이 가능한 방법으로 제조하였다. 엑 스레이 회절분석에 따르면, 제조된 메조기공 티타늄산화물은 아나타제와 루타일 상의 혼합으로 구성되어 있으며, 결정의 크기가 약 16 nm 정도 되었다. 메조기공 티타늄산화물을 첨가하였을 때, 분리막의 확산도가 증가하여 혼합기체 투과도가 1.6에서 16 GPU로 증가하였고 선택도는 45에서 37로 약간 감소하였다. 메조기공 티타늄산화물이 첨가되지 않은 분리막은 장시간 성능이 유지되었으나, 메조기공 티타늄산화물이 첨가된 분리막의 경우 시간이 지남에 따라 투과도와 선택도가 감소하였다. 이는 티타늄 산화물과 은 사이의 화학적 상호작용으로 은 나노입자의 올레핀 운반체로써의 활성을 감소시키기 때문으로 사료된다.

TiO2 nanowires were grown by thermal oxidation of TiO powder in an oxygen and nitrogen gas environment at 1000 oC. The ratio of O2 to N2 in an ambient gas was changed to investigate the effect of the gas ratio on the growth of TiO2 nanowires. The oxidation process was carried out at different O2/N2 ratios of 0/100, 25/75, 50/50 and 100/0. No nanowires were formed at O2/N2 ratios of less than 25/75. When the O2/N2 ratio was 50/50, nanowires started to form. As the gas ratio increased to 100/0, the diameter and length of the nanowires increased. The X-ray diffraction pattern showed that the nanowires were TiO2 with a rutile crystallographic structure. In the XRD pattern, no peaks from the anatase and brookite structures of TiO2 were observed. The diameter of the nanowires decreased along the growth direction, and no catalytic particles were detected at the tips of the nanowires which suggests that the nanowires were grown with a vapor-solid growth mechanism.

SnS-TiO2 nanocomposites are synthesized using simple, cheap, and less toxic SnCl2 as the tin (II) precursor. The prepared nanoparticles are characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-Vis diffuse reflectance spectra (DRS). The XRD and TEM results indicate that the prepared product has SnS nanoparticles and a grain diameter of 30 nm. The DRS demonstrate that SnS-TiO2 possesses the absorption profile across the entire visible light region. The generation of reactive oxygen species is detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and photocatalytic effect increase with the modified SnS. Excellent catalytic degradation of Texbrite BA-L (TBA) solution is observed using the SnS-TiO2 composites under visible light irradiation. It is proposed that both the strong visible light absorption and the multiple exciton excitations contribute to the high visible light photocatalytic activity.

스크린 인쇄 방식을 통해 ZnS기반의 AC 분산형 EL 소자를 제작하였다. 유전체층 재료로 BaTiO3를 사용하였다. 소자의 경우는 쉽게 변수를 조정할 수 있는 수동 스크린 인쇄 방식을 사용하여 최적의 조건으로 제작하였다. TiO2는 내산성, 내알칼리성이 좋아 인체에 무해하기 때문에 광촉매제로 많이사용되고 있다. 기판은 투명전극인 ITO glass와 유연한 ITO PET film의 두가지 방식으로 제작하였다. 본연구에서는 형광체층에 TiO2의 첨가량을 변화시킨 EL소자를 SEM과 XRD를 통하여 구조를 분석하고, 발광 스펙트럼을 통하여 분석하였다. 그리고 TiO2의 첨가량이 증가할수록, 발광효율이 증가하는 것을 알 수 있었다.

In this study, flat-type photocatalytic reaction system is applied to reduce toxic hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) in aqueous solution under UV irradiation. To overcome the limitation of conventional photocatalysis, a novel approach toward photocatalytic system for reduction of hexavalent chromium including nanotubular TiO2 (NTT) on two kinds of titanium substrates (foil and mesh) were established. In addition, modified Ti substrates were prepared by bending treatment to increase reaction efficiency of Cr(VI) in the flat-type photocatalytic reactor. For the fabrication of NTT on Ti substrates, Ti foil and mesh was anodized with mixed electrolytes (NH4F-H2O-C2H6O2) and then annealed in ambient oxygen. The prepared NTT arrays were uniformly grown on two Ti substrates and surface property measurements were performed through SEM and XRD. Hydraulic retention time(HRT) and substrate type were significantly affected the Cr(VI) reduction. Hence, the photocatalytic Cr(VI) reduction was observed to be highest up to 95% at bended(modified) Ti mesh and lowest HRT. Especially, Ti mesh was more effective as NTT substrate in this research.