掺杂钒和硅对TiO2薄膜超亲水性的影响

0引言 TiO2薄膜是众多氧化物半导体薄膜中研究最为广泛的一种材料．其表面的超亲水性和表面自清洁效应开辟了光催化薄膜功能材料的新的研究领域，已成为众多研究者研究的对象。但是如果薄膜仅由TiO2组成，当光照停止，水在TiO2薄膜表面的润湿角逐渐升高．并恢复原始状态。TiO2的禁带较宽，普通光线如太阳光等都不能将其激发．限制了其实际应用。因此如何使TiO2材料的光谱响应范围由紫外光反扩展到可见．光区一日如何更长时间地保持薄膜良好的亲水性是目前研究的重点。     

Chemical solution processing and characterization of Ba(Zr,Ti)O<Subscript>3</Subscript>/LaNiO<Subscript>3</Subscript> layered thin films

Ba(Zr,Ti)O₃/LaNiO₃ layered thin films have been synthesized by chemical solution deposition (CSD) using metal-organic precursor solutions. Ba(Zr,Ti)O₃ thin films with smooth surface morphology and excellent dielectric properties were prepared on Pt/TiO _x /SiO₂/Si substrates by controlling the Zr/Ti ratios in Ba(Zr,Ti)O₃. Chemically derived LaNiO₃ thin films crystallized into the perovskite single phase and their conductivity was sufficiently high as a thin-film electrode. Ba(Zr,Ti)O₃/LaNiO₃ layered thin films of single phase perovskite were fabricated on SiO₂/Si and fused silica substrates. The dielectric constant of a Ba(Zr_0.2Ti_0.8)O₃ thin film prepared at 700°C on a LaNiO₃/fused silica substrate was found to be approximately 830 with a dielectric loss of 5% at 1 kHz and room temperature. Although the Ba(Zr_0.2Ti_0.8)O₃ thin film on the LaNiO₃/fused silica substrate showed a smaller dielectric constant than the Ba(Zr_0.2Ti_0.8)O₃ thin film on Pt/TiO _x /SiO₂/Si, small temperature dependence of dielectric constant was achieved over a wide temperature range. Furthermore, the fabrication of the Ba(Zr,Ti)O₃/LaNiO₃ films in alternate thin layers similar to a multilayer capacitor structure was performed by the same solution deposition process.     

Photocatalytic Activity and Characterization of the Sol-Gel Derived Pb-Doped TiO2 Thin Films

Photocatalytically active Pb-doped TiO₂ thin films were prepared on a soda-lime glass substrate by sol-gel dip-coating technique using TiO₂ sols containing lead(II) nitrate. The thin films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), UV-VIS spectroscopy and X-ray diffraction (XRD). A shift of the UV-VIS absorption towards longer wavelengths was observed, which indicated a decrease in the band-gap of TiO₂ upon Pb doping. XRD results showed both pure and Pb-doped TiO₂ thin films were polycrystalline, anatase type, and oriented predominantly to the (101) plane. A slight shift in the d-spacing for the Pb-doped film indicated the incorporation of Pb into the TiO₂ lattice to form Pb _x Ti_1–x O₂ solid solution. AFM results showed Pb-doped TiO₂ thin films were composed of larger TiO₂ particles and had rougher surface, compared with un-doped TiO₂ thin films. XPS results showed that except for the enrichment of Pb near the surface, Pb exists in the forms of Pb _x Ti_1–x O₂ and PbO. Dimethyl-2,2-dichlorovinyl phosphate (DDVP) was efficiently degraded in the presence of the Pb-doped TiO₂ thin films by exposing the insecticide solution to sunlight. The mechanism of photocatalytic activity enhancement of the Pb-doped TiO₂ thin films was discussed.     

Construction of SiO2-TiO2/g-C3N4 composite photocatalyst for hydrogen production and pollutant degradation: Insight into the effect of SiO2

Using low-cost precipitated silica (SiO₂) as the carrier, a ternary SiO₂-TiO₂/g-C₃N₄ composite photocatalyst was prepared via the sol-gel method associated with a wet-grinding process. The as-prepared composite exhibits photocatalytic hydrogen production and pollutant degradation performance under solar-like irradiation. The effect of SiO₂ carrier on the properties of the heterostructure between TiO₂ and g-C₃N₄ (CN) was systematically studied. It is found that SiO₂ has important effects on promoting the interaction between TiO₂ and CN. The particle size of TiO₂ and CN was obviously reduced during the calcination process due to the effects of SiO₂. Especially, the TiO₂ particles exhibit monodispersed state with particle size below 10 nm (quantum dots), resulting in the improvement of the contact area and the interaction between TiO₂ and CN, and leading to the formation of efficient TiO₂/CN Z-scheme heterostructure in SiO₂-TiO₂/CN. Besides, the introduction of SiO₂ can increase the specific surface area and light absorption of SiO₂-TiO₂/CN, further promoting the photocatalytic reaction. As expected, the optimum SiO₂-TiO₂/CN composite exhibits 12.3, 3.1 and 2.9 times higher photocatalytic hydrogen production rate than that of SiO₂-TiO₂, CN and TiO₂/CN under solar-like irradiation, while the photocatalytic active component in SiO₂-TiO₂/CN is only about 60 wt%. Moreover, the rhodamine B degradation rate of SiO₂-TiO₂/CN is also higher than that of SiO₂-TiO₂, CN and TiO₂/CN.     

The Effect of SiO2 Addition on the Grain Size and Photocatalytic Activity of TiO2 Thin Films

The uniform transparent TiO₂/SiO₂ nanometer composite thin films were prepared via sol-gel method on the soda lime glass substrates, and were characterized by X-ray photoelectron spectroscopy (XPS), FTIR spectroscopy, UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface areas. It was found that the addition of SiO₂ to TiO₂ thin films could suppress the grain growth of TiO₂ crystal and increase the hydroxyl content of the surface of TiO₂ films. The photocatalytic activity of the as-prepared TiO₂/SiO₂ composite thin films increases for SiO₂ content of less than 5 mol%.     

Topotaxial formation of titanium-rich barium titanates during solid state reactions on (110) TiO2 (rutile) and (001) BaTiO3 single crystals

The orientation relationships of Ti-rich barium titanate phases formed by solid state reactions at high temperatures were studied using (110) TiO₂ (rutile) and (001) BaTiO₃ single-crystal substrates. Well-oriented Ba₆Ti₁₇O₄₀ islands were observed after a vapor–solid reaction of a BaO quantity equivalent to a nominal BaO film thickness of 1 nm with the TiO₂ substrate, whereas a thin film consisting of well-oriented BaTiO₃ and Ba₆Ti₁₇O₄₀ grains was formed after vapor–solid reaction of a BaO quantity equivalent to a nominal BaO film thickness of 50 nm with the rutile substrate. A topotaxial orientation relationship between Ba₆Ti₁₇O₄₀ and TiO₂ was found. Topotaxy is facilitated by a certain similarity in the oxygen sublattices of TiO₂ and Ba₆Ti₁₇O₄₀. The mechanism of the reaction occurring between BaO vapor and the TiO₂ surface at high temperature is discussed. On the other hand, several well-oriented Ba₄Ti₁₃O₃₀, Ba₆Ti₁₇O₄₀ and Ba₂Ti₅O₁₂ phases were observed to be embedded in the mainly forming Ba₂TiSi₂O₈ phase after a solid–solid reaction of amorphous SiO₂ thin films with (001) BaTiO₃ substrates at temperatures above 1000 °C. They were formed by a topotaxial reaction involving the transformation of (111) planes of BaTiO₃ into (001) planes of the Ti-rich phases by removal of BaO and insertion of TiO₂. Cross-sections of the interfaces between the substrates and the various reaction products are studied by (high-resolution) transmission electron microscopy.     

Microstructure and Photocatalytic Property of SiO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> Under Various Process Condition

Nanophase silica-titania particles were prepared by two different synthetic routes, namely, sol–gel and hydrothermal processing. The crystallinity and crystallographic phases, particle size and surface area of the materials were controlled by varying the calcination temperature, and/or the ratio of Si to Ti. It was determined by XRD that the crystallite sizes of SiO₂-TiO₂ prepared by sol–gel and hydrothermal processing decreased from 11 to 6 nm and 12 to 9 nm, respectively, as the mole fraction of silica was increased from 0.1 to 0.4. It is proposed that the presence of the amorphous silica suppresses the growth of anatase TiO₂ grains and their phase transformation to rutile. The photocatalytic decomposition rate of 1,4-dichlorobenzene (DCB) in aqueous solution with the sol–gel derived SiO₂-TiO₂ powder prepared at 750 °C was about 10 ± 5% higher than that observed with Degussa P25, whereas the SiO₂-TiO₂ samples prepared by hydrothermal processing at 250 °C showed a slightly lower decomposition rate than P25.     

The effect of calcination on the surface properties of the systems Al2O3-TiO2, SiO2-Al2O3, and SiO2-TiO2 prepared from metal alkoxides

Summary The effect of calcining temperature on the surface properties of the systems Al₂O₃-TiO₂, SiO₂-Al₂O₃, and SiO₂-TiO₂ prepared by co-hydrolysis of the corresponding metal alkoxide mixtures was studied from the crystal structure, the specific surface area, the heat of immersion in water and the surface acidity.Generally, the crystal growth of the systems accelerates with the rise of temperature of calcination. The specific surface area diminishes markedly with the rise of temperature of calcination, while the surface acidity remains almost constant. But the heat of immersion depends on the composition of the systems.

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Zusammenfassung Die Systeme Al₂O₃-TiO₂, SiO₂-Al₂O₃ und SiO₂-TiO₂ wurden durch die Hydrolyse der korrespondierenden Metallalkoxyde hergestellt. Von den Systemen wurden die spezifische Oberfläche, die Kristallstruktur, die Benetzungswärme in Wasser und das Oberflächen-p_H in Abhängigkeit von der Glühtemperatur gemessen.Im allgemeinen wird das Kristallwachstum mit der Erhöhung der Glühtemperatur beschleunigt und die spezifische Oberfläche vermindert. Hingegen ist der Oberflächen-p_H-Wert mit der Erhöhung der Glühtemperatur fast unveränderlich. Aber die Benetzungswärme hängt von der Komposition der Systeme ab.

     

总气压与Ar/O2流量比对直流对向靶磁控溅射TiO2薄膜光催化性能的影响

采用对向靶磁控溅射法在不同气压和Ar/O₂流量比条件下, 以氟化SnO₂ (FTO)导电玻璃为基底制备了多晶TiO₂薄膜. 台阶仪测量结果显示所制备TiO₂薄膜的平均厚度约为200 nm. 随着溅射气压的升高, TiO₂薄膜由锐钛矿与金红石混晶结构转变为纯锐钛矿结构. 分别采用场发射扫描电镜(FESEM)和原子力显微镜(AFM)分析了不同气压和Ar/O₂流量比对TiO₂薄膜表面形貌的影响, 结果显示TiO₂薄膜的表面粗糙度随溅射总气压和Ar/O₂流量比的增加而增大. 以初始浓度为100×10^-6 (体积分数)的异丙醇(IPA)气体为目标物检测所制备TiO₂薄膜的光催化性能, 并分析该气相光催化反应的机理, 在紫外照射条件下异丙醇先氧化为丙酮再被氧化为CO₂.当总溅射气压为2.0 Pa、Ar/O₂流量比为1:1时, 溅射所得TiO₂薄膜具备最优光催化活性并可在IPA降解反应中保持较高的催化活性和稳定性.     

Preparation and application of alumina- and titania- nanocrystals-dispersed thin films via sol-gel process with hot water treatment

A process to prepare nanocrystals-dispersed thin films at low temperatures using a hot water treatment of the gel films, and application of these nanocomposite thin films were demonstrated. When amorphous Al₂O₃ gel films were immersed in a hot water, we found that boehmite nanocrystals were formed on the surface of the films. In the hot water treatment of Al₂O₃-ZnO amorphous films, Zn-Al layered double hydroxide (LDH) was found to be formed on the films. When the SiO₂-TiO₂ gel films containing poly(ethylene glycol) were treated in a hot water, anatase nanocrystals were formed on the surface and inside of the films, and for the gel films without an organic polymer, the anatase nanocrystals were formed only on the surface of the films. In the hot water treatment of SiO₂-TiO₂ gel films under a vibration, titania nanosheets were found to be precipitated, instead of anatase nanocrysltals. Since formation of nanocrystals on the substrates using a hot water treatment is very mild conditions as the precipitation of crystals, we believe this process will open new application fields of nanocystals-dispersed thin films.     

稀碱溶液中水热法制备柔性TiO2纳米须薄膜的生长机制及表征

以柔性不锈钢基底上经磁控溅射沉积的钛膜为钛源, 在1 mol·L^-1的低浓度NaOH溶液中水热法制备了朝基底上方取向生长的大长径比柔性TiO₂纳米须薄膜, 考察了钛膜沉积条件对纳米须薄膜的影响, 系统研究了水热反应条件对薄膜生长过程的影响及TiO₂纳米须薄膜的形成机制. 通过场发射扫描电镜(FESEM)、X射线能谱仪(EDS)、高分辨透射电子显微镜(HRTEM)、X射线衍射仪(XRD)等对样品进行了表征. 结果表明, 与室温沉积的钛膜相比, 600 ℃下沉积的钛膜水热后得到的纳米线薄膜与基底的附着力更好. 所得TiO₂纳米须为单晶锐钛矿, 经由Na₂Ti₂O₄(OH)₂、H₂Ti₂O₅·H₂O转变而来. 纳米须形成于水热阶段, 平行于Na₂Ti₂O₄(OH)₂的(100)晶面择优取向生长, 纳米须经历了纳米片→纳米线束→纳米线的裂解生长过程. 朝基底上方取向生长的纳米须薄膜的形成是低浓度NaOH溶液与较高水热温度(220 ℃)协同作用的结果. 进一步在Na₂SO₄溶液中研究了薄膜电极的光电化学性能, 结果表明, TiO₂纳米须薄膜的光电性能明显优于零维纳米颗粒薄膜和二维纳米片薄膜, 显示了良好的应用前景.     

不同基底对TiO2和SiO2薄膜的光学性能的影响

采用溶胶-凝胶法分别在K9玻璃、单晶硅和石英玻璃基底上制备了纳米TiO₂和SiO₂薄膜。利用SEM、UV-Vis及反射式椭圆偏振光谱仪对薄膜的微观结构及光学特性进行了表征和分析。结果表明：3种基底中, 单晶硅基底上TiO₂和SiO₂薄膜折射率最大;在非晶态K9玻璃和石英玻璃基底上TiO₂薄膜折射率和透光率差异较大;SiO₂薄膜在非晶态基底上折射率、透光率相近;3种基底上薄膜的折射率和消光系数都有随波长增大而减小的趋势, 同时Cauchy模型能较好的描述单晶硅基底上两种薄膜在400~800 nm波段的光学性能。     

不同基底对TiO2和SiO2薄膜的光学性能的影响

采用溶胶-凝胶法分别在K9玻璃、单晶硅和石英玻璃基底上制备了纳米TiO₂和SiO₂薄膜。利用SEM、UV-Vis及反射式椭圆偏振光谱仪对薄膜的微观结构及光学特性进行了表征和分析。结果表明:3种基底中, 单晶硅基底上TiO₂和SiO₂薄膜折射率最大;在非晶态K9玻璃和石英玻璃基底上TiO₂薄膜折射率和透光率差异较大;SiO₂薄膜在非晶态基底上折射率、透光率相近;3种基底上薄膜的折射率和消光系数都有随波长增大而减小的趋势, 同时Cauchy模型能较好的描述单晶硅基底上两种薄膜在400~800 nm波段的光学性能。     

Electrochemical Production of Si without Generation of CO2 Based on the Use of a Dimensionally Stable Anode in Molten CaCl2

The current Si production process is based on the high‐temperature (1700 °C) reduction of SiO₂ with carbon that produces large amounts of CO₂. We report an alternative low‐temperature (850 °C) process based on the reduction of SiO₂ in molten CaCl₂ that does not produce CO₂. It utilizes an anode material (Ti₄O₇) capable of sustained oxygen evolution. Two types of this anode material, dense Ti₄O₇ and porous Ti₄O₇, were tested. The dense anode showed a better performance. The anode stability is attributed to the formation of a protective TiO₂ layer on its surface. In situ periodic current reversal and ex situ H₂ reduction could be used for extending the lifetime of the anodes. The findings show that this material can be applied as a recyclable anode in molten CaCl₂. Si wires, films, and particles were deposited with this anode under different cathodic current densities. The prepared Si film exhibited ≈30–40 % of the photocurrent response of a commercial p‐type Si wafer, indicating potential use in photovoltaic cells.     

Effect of biphase on dielectric properties of Bi-doped lead strontium titanate thin films

Pb_0.4Sr_0.6TiO₃ (PST) thin films doped with various concentration of Bi were prepared by a sol-gel method. The phase status, surface morphology and dielectric properties of these thin films were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance analyzer, respectively. Results showed that the thin films with the maximum dielectric constant and minimum dielectric loss were obtained for x=0.15. For x<0.15, only pure PST perovskite phase were in the thin films. For 0.2<x<0.4, the PST/Bi₂Ti₂O₇ biphase were obtained. The thin films with pure Bi₂Ti₂O₇ pyrochlore phase were obtained for x=0.67. The biphase thin films had high tunability and high figure of merit (FOM). The FOM of PST/Bi₂Ti₂O₇ biphase thin film was about 6 times higher than that thin films formed with pure perovskite phase or pure pyrochlore phase.     

Preparation and properties of SiO2-TiO2 thin films from silicic acid and titanium tetrachloride

The preparation of SiO₂-TiO₂ thin films by the sol-gel method using silicic acid and titanium tetrachloride as starting materials was studied. The homogeneous sols were obtained by the condensation reaction of silicic acid with titanium tetrachloride in methanol-tetrahydrofuran. The dipcoating of slide glasses and silicon wafers followed by heat treatment gave oxide thin films of 88–93% transmittance, 3000–4500 Å thickness, and 1.45–1.80 refractive index, depending on heat-treatment temperature and TiO₂ content. FT-IR measurement showed that the Si-O-Ti bond is formed even in the sol and films. The variations of film thickness and refractive index on transformation from the gels into the oxides were found to be quite low.     

Co-continuous porosity formation on thin oxide films: transition metal oxides (TiO2 and Nb2O5) versus SiO2

In this study the role of different types of metal alkoxides, as well as the roles of acetyl acetone (ACAC) and polyethylene glycol (PEG) on co-continuous porosity formation in thin oxide films (TiO₂, Nb₂O₅, SiO₂ and TiO₂–SiO₂ mixed oxide) is investigated. The films are produced by the spin coating method and the resulting morphologies are characterized from the scanning electron microscope images of the surface and of the focused ion beam machined cross-sections. Results show that the porous, co-continuous morphology forms only in transition metal oxide films, TiO₂ and Nb₂O₅, and that it does not form in the semimetal SiO₂ film. The effect of interfacial activity of ACAC modified Ti- and Nb-alkoxides together with the effect of PEG reaction with the metal oxide oligomers are found to cause co-continuous porosity formation in TiO₂ and Nb₂O₅ films. Moreover, it appears that both of these effects are more pronounced during formation of Nb₂O₅ than TiO₂ films.     

Fabrication and photocatalytic activity of TiO2/SiO2 composite nanotubes

TiO₂/SiO₂ composite nanotube photocatalysts supported on Al substrates were prepared by the anodic aluminum oxide (AAO) liquid-phase deposition method for degradation of 100 mg/L methyl blue (MB). AAO templates were prepared in H₃PO₄ acidic electrolytes through the two-step anodic oxidation method. The photocatalysts were characterized by field-emission scanning electron microscopy, thermal analysis (TG-DTA), and Fourier-transform infrared, x-ray photoelectron, and UV?CVis diffuse spectroscopies. The results showed that the presence of SiO₂ in TiO₂ inhibited the crystal phase transformation temperature effectively, with a greater wall thickness of 80?C100 nm. It was found that Ti?CO?CSi bonds were formed on the surface and the surface hydroxyl concentration was increased, resulting in enhanced photocatalytic activity, being about 20% higher than for pure TiO₂ films. The calculated band structure for TiO₂/SiO₂ was investigated using first-principle calculations. The TiO₂/SiO₂ composite exhibited a wider conduction band which would effectively prohibit recombination of photogenerated electrons and holes.     

Preparation and characterization of poly(l-lactic acid)/TiO2 nanoparticle nanocomposite films with high transparency and efficient photodegradability

Poly(l-lactic acid)-TiO₂ nanoparticle nanocomposite films were prepared by incorporating surface modified TiO₂ nanoparticles into polymer matrices. In the process of preparing the nanocomposite films, severe aggregation of TiO₂ nanoparticles could be reduced by surface modification by using carboxylic acid and long-chain alkyl amine. As a result, the nanocomposite films with high transparency, similar to pure PLA films, were obtained without depending on the amount of added TiO₂ nanoparticles. A TEM micrograph of the nanocomposite films suggests that the TiO₂ nanoparticles of 3-6 nm in diameter were uniformly dispersed in polymer matrices. Photodegradation of PLA-TiO₂ nanoparticle nanocomposite films was also investigated. The results showed that nanocomposite films could be efficiently photodegraded by UV irradiation in comparison with pure PLA.     

一种简单的提高无定形TiO2光催化活性的方法及其在增透膜中的应用

通过简单的溶胶-凝胶法制备得到了小粒径的无定形TiO_2粒子,并将其沉积在多孔SiO_2膜层表面,多孔SiO_2膜层大的表面积有助于无定形TiO_2的良好分散,高度分散的无定形TiO_2粒子对膜层的光学性能影响较小,通过匹配合适的低折射率的SiO_2膜层,制备得到的SiO_2无定形TiO_2(SiO_2amorphous-TiO_2)膜层表现出和理想单层增透膜相似的光学性能。同时SiO_2amorphous-TiO_2的光催化性能显著提高,明显高于单层无定形TiO_2。而且SiO_2无定形TiO_2膜层甚至表现出比相应的负载锐钛矿型TiO_2的膜层,即SiO_2锐钛矿TiO_2,更高的光催化活性,这一反常现象的原因是,无定型TiO_2膜层表面丰富的羟基有助于减少空穴-电子对的复合,其相对疏松的结构能够加快光生电子-空穴的转移速率,而这些因素的影响超过了晶型结构对光催化活性的影响。同时SiO_2膜层的孔隙结构在浸渍-提拉镀制过程中,自发形成并不需要后续热处理过程,因此,整个SiO_2无定形TiO_2膜层的制备均可在室温下完成,能够实现其在不耐热基片上的应用。