Coating of TiO2 thin films on particles by a plasma chemical vapor deposition process

TiO₂ thin films were experimentally coated on glass beads by means of a rotating cylindrical plasma chemical vapor deposition (PCVD) reactor. The morphologies and growth rates of the TiO₂ thin films before and after heat treatment were measured for various process conditions. The precursors for the TiO₂ films were generated from TTIP by plasma reactions, and they were deposited on the glass beads to become TiO₂ thin films. The TiO₂ thin films coated on the glass beads became more uniform by heat treatment. The TiO₂ thin films grew more quickly on the glass beads with increasing mass flow rate of TTIP, reactor pressure, or rotation speed of the reactor. As the applied electric power decreases, the thickness of the thin films on the glass beads increases. This experimental study shows that the use of a rotating cylindrical PCVD reactor can be a good method to coat high-quality TiO₂ thin films uniformly on particles.     

Simultaneous removal of SO2 and NO by wet scrubbing using aqueous chlorine dioxide solution

The present study attempts to generate chlorine dioxide (ClO(2)) gas continuously by chlorate-chloride process and to utilize it further to clean up SO(2) and NO(x) gases simultaneously from the flue gas in the lab-scale bubbling reactor. Experiments were carried out to examine the effect of various operating parameters like input SO(2) concentration, input NO concentration, pH of the reaction medium, and ClO(2) feeding rate on the SO(2) and NO(x) removal efficiencies at 45 degrees C. Complete oxidation of NO into NO(2) occurred on passing sufficient ClO(2) gas into the scrubbing solution. SO(2) removal efficiency of about 100% and NO(x) removal efficiency of 66-72% were achieved under optimized conditions. NO(x) removal efficiency decreased slightly with increasing pH and NO concentration. Input SO(2) concentration had marginal catalytic effect on NO(2) absorption. No improvement in the NO(x) removal efficiency was observed on passing excess of chlorine dioxide in the scrubbing solution.     

A dual-use of DBD plasma for simultaneous NO(x) and SO(2) removal from coal-combustion flue gas

Dielectric barrier discharge (DBD) was investigated for the simultaneous removal of NO(x) and SO(2) from flue gas in a coal-combustion power plant. The DBD equipment was used in either a mode where flue gas was directed through the discharge zone (direct oxidation), or a mode where produced ozonized air was injected in the flue gas stream (indirect oxidation). Removal efficiencies of SO(2) and NO for both methods were measured and compared. Oxidation of NO is more efficient in the indirect oxidation, while oxidation of SO(2) is more efficient in the direct oxidation. Addition of NH(3), has lead to efficient removal of SO(2), due to thermal reaction, and has also enhanced NO removal due to heterogeneous reactions on the surface of ammonium salt aerosols. In the direct oxidation, concentration of CO increased significantly, while it maintained its level in the indirect oxidation.     

Fabrication and characterization of photoelectrode thin films with different morphologies of TiO2 nanoparticles for dye-sensitized solar cells

This study deals with the fabrication of three different morphologies of TiO2 nanoparticles to fabricate two-layer photoelectrode thin film for dye-sensitized solar cells (DSSC). The four different TiO2 morphologies are titania nanotubes (Tnt), TiO2 nanoparticles (H220), TiO2 nanoparticle (SP) and commercial DP-25 nanoparticles (P-25). To prepare the thin films of the photoelectrodes, the first layer is coated by H220 TiO2 nanoparticles, and the second is coated by 3 kinds of materials optimally proportionally mixed - P25, SP and Tnt. The photoelectric conversion efficiency of DSSCs with photoelectrodes fabricated using H220 reached 6.31%. Finally, the TiO2 nanaomaterials with four different morphologies were used to prepare a two layer photoelectrode with the structure of H220/P25-Tnt-SP which was combined with a Pt counter electrode to assemble DSSCs. These DSSCs had photoelectric conversion efficiencies of as high as 7.47%.     

Application of a hybrid system comprising carbon-doped TiO2 film and a ceramic media-packed biofilter for enhanced removal of gaseous styrene

It is difficult to efficiently remove gaseous styrene using a TiO(2) film-coated photoreactor under UV light. Therefore, we used a hybrid system consisting of a carbon-doped TiO(2) (C-TiO(2)) film and a media-packed biofilter in order to enhance the removal efficiency (RE) of gaseous styrene compared to that of a pure (undoped) TiO(2) photoreactor. The C-TiO(2) was synthesized by a sol-gel combustion method, and its absorption spectrum was stronger that of pure (undoped) TiO(2) in the UV-vis range. The resultant RE of the C-TiO(2) film was 113-200% higher than that of the pure TiO(2) film. The initial RE of the photoreactor for input styrene concentrations of 630 mg m(-3), 420 mg m(-3), and 105 mg m(-3) was 20.6%, 29.8%, and 40.0%, respectively. When the biofilter was added, the RE increased to 93.3%, 97.9%, and 99.0%, respectively. Thus, application of the hybrid system consisting of both a photoreactor coated with a C-TiO(2) film and a biofilter is advantageous in terms of the removal efficiency of gaseous styrene.     

介质阻挡放电净化汽车尾气NOX和HC的应用研究

研制了一套高压脉冲电源和介质阻挡放电反应器,通过在常压下放电产生低温等离子体。结合模拟汽车排气试验,对放电电压、脉冲频率、含氧量以及初始浓度影响HC、NOx净化的规律进行了系统研究。研究表明,利用介质阻挡放电产生低温等离子体净化尾气,是一种具有发展前景的排气后处理技术,对汽车尾气NOx和HC的净化具有明显的净化效果。     

Nitrate removal by Thiobacillus denitrificans immobilized on poly(vinyl alcohol) carriers

Nitrate contamination is becoming a widespread environmental problem, and autotrophic denitrification with Thiobacillus denitrificans is a promising process considering efficiency, cost and maintenance. The denitrification efficiencies of T. denitrificans were compared in batch reactors between free cells and cells immobilized on polyvinyl alcohol (PVA) carriers made with thrice freezing/thawing and boric acid methods. The results indicated that the free cell reactor of T. denitrificans added with 10% (v/v) of PVA carrier made by thrice freezing/thawing (PVA-TFT) exhibited faster in S(2)O(3)(2-)-S consumption, SO(4)(2-) generation, and NO(3)(-)-N denitrification, with corresponding values being 165 mg (S(2)O(3)(2-)-S)/L.d, 491 mg (SO(4)(2-))/Ld, and 44 mg (NO(3)(-)-N)/Ld, which were increased by 50%, 61%, and 57% respectively compared to the control reactor with only free cells. Inhibition of denitrification by accumulated SO(4)(2-) in PVA-TFT reactor appeared at the concentration of approximately 6000 mg (SO(4)(2-))/L, and 75% of NO(3)(-)-N removal efficiency was achieved after 12d operation under the condition of initial 700 mg/L NO(3)(-)-N concentration.     

Effect of O2 on NO removal by ammonia radical injection using one-cycle sinusoidal power source

NO reduction experiment was performed by injecting ammonia radicals, which were externally generated by flowing the NH₃ gas diluted with Ar gas through a dielectric barrier discharge with a one-cycle sinusoidal-wave power source. The discharge was intermittently formed between coaxial cylindrical electrodes with a space of 1.5 mm at an applied peak-to-peak voltage of 3-25 kV. The generated radicals were injected into simulation gas (NO/O₂/N₂). The simulation gas contained 0-5.6% O₂, and the effect of O₂ on NO_x removal was discussed. The minimum reaction temperature for NO reduction was low when simulation gas contained O₂. High O₂ concentration (O₂=5.6%) in simulation gas, high repetition rate to NH₃, and high applied power to NH₃ decreased NO removal efficiency.     

Surface structure of the TiO2 thin film photocatalyst

Control of the surface structure of titanium dioxide thin film photocatalysts was successfully carried out by a polymer-doped dip-coating process. The thin films prepared were either transparent or opaque, depending on the molecular weight of the polymer doped. All the thin film photocatalysts had anatase form with similar crystallinity. The surface of the transparent thin films looked plain consisting of uniformly aggregated nanometer-size TiO2 particles, while the opaque thin films were formed of cubic crystalline TiO2 at the micrometer level. Both the transparent and opaque films showed catalytic activity for the elimination of NOx in air. The specific surface area and photocatalytic activity of the transparent thin film was almost the same as that of the opaque one. The activity of the thin films was almost equal to the commercial photocatalyst P25. Decrease in the film thickness led to a decrease of the elimination of NO in air by the thin films. The thin films were porous and the surface area was dependent on the film thickness. Adsorbed NO was photooxidized to NO2 by the thin films, while the NO2 formed was re-photooxidized to HNO3 before the desorption of NO2 from the film surface.     

Electrospinning processed nanofibrous TiO(2) membranes for photovoltaic applications

We have recently fabricated dye-sensitized solar cells (DSSCs) comprising nanofibrous TiO(2) membranes as electrode materials. A thin TiO(2) film was pre-deposited on fluorine doped tin oxide (FTO) coated conducting glass substrate by immersion in TiF(4) aqueous solution to reduce the electron back-transfer from FTO to the electrolyte. The composite polyvinyl acetate (PVac)/titania nanofibrous membranes can be deposited on the pre-deposited thin TiO(2) film coated FTO by electrospinning of a mixture of PVac and titanium isopropoxide in N,N-dimethylformamide (DMF). The nanofibrous TiO(2) membranes were obtained by calcining the electrospun composite nanofibres of PVac/titania as the precursor. Spectral sensitization of the nanofibrous TiO(2) membranes was carried out with a ruthenium (II) complex, cis-dithiocyanate-N,N(')-bis(2,2(')-bipyridyl-4,4(')-dicarboxylic acid) ruthenium (II) dihydrate. The results indicated that the photocurrent and conversion efficiency of electrodes can be increased with the addition of the pre-deposited TiO(2) film and the adhesion treatment using DMF. Additionally, the dye loading, photocurrent, and efficiency of the electrodes were gradually increased by increasing the average thickness of the nanofibrous TiO(2) membranes. The efficiency of the fibrous TiO(2) photoelectrode with the average membrane thickness of 3.9?μm has a maximum value of 4.14%.     

改性TiO2自洁净玻璃的制备与表征

用溶胶-凝胶法制备了表面镀有La—TiO2光催化薄膜的自洁净玻璃,并利用XRD,UV—Vis,SF等手段对La—TiO2光催化薄膜进行检测。结果表明：镧离子掺杂可以减少电子-空穴对的复合几率,提高量子效率,从而有助于光催化活性的增强。     

Photocatalytic degradation of methyl orange: influence of H2O2 in the TiO2-based system

The purpose of this study was to investigate the photocatalytic oxidation of a reactive azo dye. The photocatalytic activity of the TiO2 was studied using a reactor equipped with UV-A sources, with maximum emission at 365 nm. The photocatalytic activity of the TiO2 powder (99.9% anatase) and thin films has been measured through the decomposition of methyl orange solutions. The thin film was prepared by doctor blade and spray pyrolysis deposition (SPD). The TiO2 suspensions were prepared at 1 g/L concentration, and the initial methyl orange concentration was fixed at 7.8125 mg/L. The influence of the TiO2 (powder or thin films) and/or O2 and H2O2 on the photobleaching rate, was tested under different experiments, at pH = 5. Thin films (doctor blade) of TiO2 formed of mezo-sized aggregates formed of nanosized anatase crystallites show better photobleaching efficiency than thin film (SPD) due to their large internal surface. The rate is even higher in H2O2 compared to oxygen environment.     

Development of enhanced sulphidogenesis process for the treatment of wastewater having low COD/SO(4)(2-) ratio

An upflow hybrid sulphidogenesis reactor of 1.75 L volume was developed (at oxidation-reduction potential (ORP)=-225+/-25 mV) using flocculent extended aeration process sludge (selected based on screening study at COD/SO(4)(2-) ratio=1) for enhanced sulphidogenesis and COD removal. The reactor was subjected to various loading rate studies at a hydraulic retention time (HRT) of 1 day with COD/SO(4)(2-) ratio of 1.3. At loading rate of 2.5 kg COD/(m(3)day), excellent performance with more than 97% removal of sulphate was achieved within bottom 40% volume of the reactor. At a higher loading rate of 3.75 kg COD/(m(3)day), there was a decrease in both sulphate (70-75%) and COD (50%) removal efficiencies. A controlled and continuous air injection (0.19 L/(L min)) given at 40% volume of the reactor affected sulphide oxidation inside the reactor and enhanced the sulphate reduction in the reactor. The specific sulphate reduction capacity of mixed culture drawn from the bottom part of the reactor was 0.35 kg SO(4)(2-)/(kg VSS day). The results of this study showed that enhanced sulphidogenesis with sulphide inhibition control can maintain sulphate-reducing bacteria (SRB) in anaerobic reactor at low COD/SO(4)(2-) ratios between 1 and 2, with efficient simultaneous removal of COD and SO(4)(2-). The sulphide generated in the system can be recovered as elemental sulphur and/or oxidized back to sulphate.     

Preparation and characterization of TiO2 coated Fe nanofibers for electromagnetic wave absorber

Recently, electromagnetic interference (EMI) and electromagnetic compatibility (EMC) have become serious problems due to the growth of electronic device and next generation telecommunication. It is necessary to develop new electromagnetic wave absorbing material to overcome the limitation of electromagnetic wave shielding materials. The EMI attenuation is normally related to magnetic loss and dielectric loss. Therefore, magnetic material coating dielectric materials are required in this reason. In this study, TiO2 coated Fe nanofibers were prepared to improve their properties for electromagnetic wave absorption. Poly(vinylpyrrolidone) (PVP) and Iron (III) nitrate nonahydrate (Fe(NO3)3 x 9H2O) were used as starting materials for the synthesis of Fe oxide nanofibers. Fe oxide nanofibers were prepared by electrospinning in an electric field and heat treatment. TiO2 layer was coated on the surface of Fe oxide nanofibers using sol-gel process. After the reduction of TiO2 coated Fe oxide nanofibers, Fe nanofibers with a TiO2 coating layer of about 10 nm were successfully obtained. The morphology and structure of fibers were characterized by SEM, TEM, and XRD. In addition, the absorption properties of TiO2 coated Fe nanofibers were measured by network analyzer.     

Photocatalytic TiO(2) deposition by chemical vapor deposition

Dip-coating, spray-coating or spin-coating methods for crystalline thin film deposition require post-annealing process at high temperature. Since chemical vapor deposition (CVD) process is capable of depositing high-quality thin films without post-annealing process for crystallization, CVD method was employed for the deposition of TiO(2) films on window glass substrates. Post-annealing at high temperature required for other deposition methods causes sodium ion diffusion into TiO(2) film from window glass, resulting in the degradation of photocatalytic efficiency. Anatase-structured TiO(2) thin films were deposited on window glass by CVD, and the photocatalytic dissociation rates of benzene with CVD-grown TiO(2) under UV exposure were characterized. As the TiO(2) film deposition temperature was increased, the (112)-preferred orientations were observed in the film. The (112)-preferred orientation of TiO(2) thin film resulted in a columnar structure with a larger surface area for benzene dissociation. Obviously, benzene dissociation rate was maximum when the degree of the (112) preferential orientation was maximum. It is clear that the thin film TiO(2) should be controlled to exhibit the preferred orientation for the optimum photocatalytic reaction rate. CVD method is an alternative for the deposition of photocatalytic TiO(2).     

掺氮TiO_(2-x)N_x薄膜托槽的制备及其性能研究

利用射频磁控溅射制备了氮掺杂TiO2-xNx薄膜托槽,通过X射线衍射(XRD)、扫描电镜(SEM)等测试手段表征了托槽表面薄膜的结构、形貌,并通过原子力显微镜(AFM)、多功能材料表面试验仪等研究了TiO2-xNx薄膜与基底托槽的附着力、TiO2-xNx薄膜托槽的表面粗糙度以及表面摩擦系数。结果表明制备的托槽表面为均一的锐钛矿相结构TiO2-xNx薄膜,晶粒粒径为30nm,纳米TiO2-xNx薄膜托槽表面致密、平整,薄膜与托槽衬底结合紧密、附着性好,托槽表面粗糙度降低,摩擦系数变小,改善了托槽表面性能,为抗菌性研究奠定了基础。     

Analysis of the electron transport properties in dye-sensitized solar cells using highly ordered TiO2 nanotubes and TiO2 nanoparticles

This study uses TiO2 nanoparticles and highly ordered anatase TiO2 nanotubes (AOTnt) as thin film photoanodes for dye-sensitized solar cells (DSSCs). DSSCs are assembled by single-layer and double-layer films of photoanodes and their electron transfer performance is compared. TiO2 nanoparticles were fabricated by the sol-gel method, and AOTnts were grown on titanium foil. This study uses TiO2 nanoparticles or AOTnts to prepare single-layer photoanodes and TiO2 nanoparticles coated on an AOTnt film to fabricate double-layer photoanodes. These three different photoanodes are soaked in dye and assembled into DSSCs, and their open-loop voltage recession, electrochemical impedance, lifetime, life cycle, and effective diffusion coefficient are measured. Electron transfer efficiency of the photoanodes and light harvesting efficiency are further analyzed. The results show that the electron transfer efficiency, open-loop voltage recession, lifetime, life cycle, and effective diffusion coefficient of the DSSCs assembled using double-layer photoanodes (AOTnt-TiO2) are superior to those of single-layer photoanodes (TiO2 or AOTnt).     

柱状晶形貌TiO2膜厚对FTO/TiO2镀膜玻璃光催化活性影响

采用溶胶凝胶法,在FTO(SnO2:F)低辐射镀膜玻璃衬底上制备了柱状晶体结构的TiO2薄膜,获得双层结构FTO/TiO2镀膜玻璃样品.研究了TiO2薄膜厚度对FTO/TiO2镀膜玻璃样品的光催化活性、低辐射性能以及透光性能的影响.结果表明,FTO/TiO2镀膜玻璃样品光催化活性随着TiO2薄膜厚度的增加先升高后下降,在TiO2薄膜厚度为300 nm时光催化活性最佳;低辐射性能随着TiO2薄膜厚度的增加而下降,但TiO2薄膜厚度为300 nm时仍然具备一定的低辐射性能;透光性能与TiO2薄膜膜厚的关系不大,可见光透射比保持在72%左右;表面平均粗糙度约为1 nm,表面光滑,不易沾染油污灰尘.该镀膜玻璃在保证低辐射建筑节能和透光的前提下,兼具光催化自清洁功能,具有很好的应用前景.     

TiO_2包覆对不同粒径羰基铁粉吸波性能的影响

本文采用溶胶-凝胶法,分别在粒径为6μm和1μm的羰基铁粉表面成功包覆了一层二氧化钛薄膜;利用矢量网络分析仪测量了羰基铁粉和石蜡所制成的复合材料的电磁参数,对比分析了二氧化钛包覆前后羰基铁粉复合材料在微波频段的复介电常数、复磁导率和微波吸收性能的变化。实验结果表明:二氧化钛包覆层能有效地增大粒径为1μm的羰基铁粉的复磁导率和复介电常数,改善小粒径羰基铁粉的微波吸收性能。通过分析认为二氧化钛包覆层能有效地阻隔颗粒间涡流的形成,由此能很好地解释二氧化钛包覆层对1μm羰基铁粉微波吸收性能的增强效果。     

Photocatalytic activity of nanosized TiO2 thin film prepared by magnetron sputtering method

Nanosized TiO2 thin film on the substrate such as stainless steel plate and slide glass film were prepared by magnetron sputtering method, and these TiO2 thin films were characterized by field emission-scanning electron microscopy (FE-SEM). Photocatalytic activity for Methyl-ethyl-ketone (MEK) and acetaldehyde were measured using a closed circulating reaction system through the various ultra violet (UV) sources. From the results of SEM images, nanosized TiO2 thin film was uniformly coated on slide glass, ranging from 360 nm to 370 nm. Photocatalytic activity of MEK over TiO2 thin film on stainless steel plate did not occur by UV-A irradiation, but was efficiently decomposed by UV-B and UV-C. Also, acetaldehyde could be decomposed than MEK. The effect of sputtering conditions on their structure and photocatalytic activities were investigated in detail.