Coating and water permeation properties of SiO2 thin films prepared by the sol-gel method on nylon-6 substrates

Nylon-6 substrates were coated with SiO₂ thin films by the sol-gel method and their water permeability coefficient was evaluated. Methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) were used as starting materials. The addition of MTES to TEOS has enabled the formation of crack-free thin films on the substrates. The thin films strongly adhered to the substrates. The water permeability coefficients of nylon-6 substrates coated with these thin films decreased with the increase in the ratio of TEOS to the total alkoxides. The pretreatment of the nylon-6 substrates with -aminopropyltriethoxysilane was found to be effective to suppress the water permeability. The water permeability was suppressed by about 40% under the optimal condition.     

Photocatalytic Activity and Photo-Induced Wettability Conversion of TiO2 Thin Film Prepared by Sol-Gel Process on a Soda-Lime Glass

We have developed the transparent photoactive TiO₂ thin film coated on soda lime glass (SLG) by sol-gel process. Titanium dioxide thin films coated on SLG exhibit lower photocatalytic activity due to the thermal diffusion of Na ion from the SLG substrate. Thin SiO₂ film precoating is very effective to prevent the thermal diffusion of Na ion. We have evaluated the photocatalytic decomposition of gaseous acetaldehyde and the photo-induced surface wettability of TiO₂ films with and without SiO₂ precoating layer. As expected, the TiO₂ film on SiO₂/SLG is more photoactive to decompose acetaldehyde than that on SLG. However, as for wettability conversion, there was little difference in the conversion rate between TiO₂ film without SiO₂, and TiO₂ film with SiO₂. Different dependence of Na ion diffusion on two kinds of photo-induced reaction on TiO₂ is discussed based on the difference of the photo-induced reaction mechanism.     

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%.     

Characterization of a passivation layer comprising MgO?SiO2 and ZrO2

Thin films with magnesium oxide (MgO) and silicon oxide (SiO₂) compounds mixed at various mixture ratios were deposited on flexible polyether sulfone (PES) substrates by an e‐beam evaporator to investigate their potential for transparent barrier applications. In this study, as the MgO fraction increased, thin films comprising MgO and SiO₂ compounds became more amorphous, and their surface morphologies became smoother and denser. In addition, zirconium oxide (ZrO₂) was added to the above‐mentioned compound mixtures, and the properties of the compound mixture comprising Mg? Si? Zr? O were then measured. ZrO₂ made the thin mixture films more amorphous, and made the surface morphology denser and more uniform. Whole thin films of 250 ± 30 nm in thickness were formed, and their water vapor transmission rates (WVTRs) decreased rapidly. The best WVTR was obtained by depositing thin films of Mg? Si? Zr? O compound among the whole thin films. The WVTRs of the PES substrate in the bare state decreased from 47 to 0.8 g m^?2 day^?1. This Mg? Si? Zr? O compound was deposited on polyethylene terephtalate (PET) substrates again to confirm the availability of the compound mixture. Thin films on the PET substrates decreased the WVTRs remarkably from 2.96 to 0.01 g m^?2 day^?1. These results were similar to those of thin films on PES substrates. As the thin mixture films became more amorphous and surface morphology denser and more uniform, the WVTRs decreased. Therefore, the thin mixture films became more suitable for flexible organic light emitting displays (OLEDs) as transparent passivation layers against moisture in air. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of substrate on phase formation and surface morphology of sol-gel lead-free KNbO3, NaNbO3, and K0.5Na0.5NbO3 thin films

Environmentally acceptable lead-free ferroelectric KNbO₃ (KN) or NaNbO₃ (NN) and K_0.5Na_0.5NbO₃ (KNN) thin films were prepared using a modified sol-gel method by mixing potassium acetate or sodium acetate or both with the Nb-tartrate complex, deposited on the Pt/Al₂O₃ and Pt/SiO₂/Si substrates by a spin-coating method and sintered at 650°C. X-ray diffraction (XRD) analysis indicated that the NN and KNN films on the Pt/SiO₂/Si substrate possessed a single perovskite phase, while NN and KNN films on the Pt/Al₂O₃ substrate contained a small amount of secondary pyrochlore phase, as did KN films on both substrates. Scanning electron microscopic (SEM) and atomic force microscopic (AFM) analyses confirmed that roughness R _q of the thin KNN/Pt/SiO₂/Si film (?? 7.4 nm) was significantly lower than that of the KNN/Pt/Al₂O₃ film (?? 15 nm). The heterogeneous microstructure composed of small spherical and larger needle-like or cuboidal particles were observed in the KN and NN films on both substrates. The homogeneous microstructure of the KNN thin film on the Pt/SiO₂/Si substrate was smoother and contained finer spherical particles (?? 50 nm) than on Pt/Al₂O₃ substrates (?? 100 nm). The effect of different substrates on the surface morphology of thin films was confirmed.     

Structural Changes in Sol-Gel Derived SiO2 and TiO2 Films by Exposure to Water Vapor

Structural changes in sol-gel derived thin films by exposure to water vapor were investigated using Fourier transform infrared absorption spectroscopy, ellipsometry and x-ray diffraction. We found that SiO₂ gel films were densified with a decrease in OH groups by the exposure at 60°–180°C. The shrinkage and the peak frequency of ₄ (TO) for the exposed films were comparable to those heated in a dry atmosphere at temperatures above 500°C. However, OH groups in the films were not completely removed by the water exposure. A subsequent annealing above 300°C changed the structure of the water-exposed SiO₂ films with condensation of the remaining OH groups. Although the exposed SiO₂ gel films were amorphous, TiO₂ gel films were transformed to anatase with a decrease in OH groups by the treatments at 80°–180°C.     

Dielectric and optical properties of BaTiO<Subscript>3</Subscript> thin films prepared by low-temperature process

Barium titanate (BaTiO₃) thin films have been prepared by low temperature processing on Pt/Ti/SiO₂/Si substrates using sol-gel-hydrothermal (SGHT) technique, which combined the conventional sol-gel process and hydrothermal method. X-ray diffraction analysis showed that the barium titanate thin films are polycrystalline. As-reacted barium titanate films grown on Pt(111)/Ti/SiO₂/Si(100) substrates had a dielectric constant (ε) and loss tangent (tanδ) of 80 and 0.05 at 1 MHz, respectively. The optical constants including refractive index n, extinction coefficient k, and absorption coefficient α of the barium titanate thin films in the wavelength range of 2.5–12.6 μm were obtained by infrared spectroscopic ellipsometry.     

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。     

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。     

Magnetoelectric Bi3.25Nd0.75Ti3O12–La0.6Ca0.4MnO3 composite thin films derived by SOL–GEL method

Magnetoelectric (ME) Bi_3.25Nd_0.75Ti₃O₁₂–La_0.6Ca_0.4MnO₃ (BNT–LCMO) composite thin films were deposited on Pt/Ti/SiO₂/Si(100) substrates by a simple SOL–GEL method and spin-coating process with two different deposition sequences: BNT/LCMO/Pt/Ti/SiO₂/Si(BLP) and LCMO/BNT/Pt/Ti/SiO₂/Si(LBP). Our results show the composite thin films exhibit both good ferroelectric and magnetic properties, as well as a ME effect. BLP thin films have larger maximum ME voltage coefficient values than LBP structured thin films. The deposition sequence has a notable effect on the ferroelectric and magnetic properties and ME coupling behavior of the bi-layer thin films.     

Study on the Superhydrophilicity of the SiO2-TiO2 Thin Films Prepared by Sol-Gel Method at Room Temperature

Nanoscale SiO₂-TiO₂ composite thin films with the thickness of about 100 nm were prepared by sol-gel method at room temperature in air. The chemical states of the elements on the surface and near the surface were measured by XPS. The results showed that the Ti on/near the surface of the thin films existed not only as TiO₂ but also as Ti₂O₃. Part of the TiO₂ was changed to Ti₂O₃ after UV irradiation. The crystalline structure of the TiO₂ in the SiO₂-TiO₂ thin films was anatase with the crystallite size of 14–20 nm. It was found that the thin film prepared at room temperature in air has good superhydrophilic property and has strong adherence to the substrate.     

Preparation and femtosecond non-linear optical properties of Ag/SiO2 composite thin films

Ag nanoparticles embedded in SiO₂ thin films (Ag/SiO₂ films) were prepared by a multitarget sputtering method. In the optical absorption spectra of the Ag/SiO₂ films, the absorption peak due to the surface plasmon resonance (SPR) of Ag particle was clearly observed at the wavelength of 394–413 nm. The imaginary part of the third-order non-linear susceptibility, Im [χ⁽³⁾], of the Ag/SiO₂ film was estimated to be ?1.1×10^?8 esu measured by the femtosecond Z-scan technique near the SPR peak. The response time of the film measured from the decay of the differential transmission of the pump-probe experiment was 1.3 ps at the SPR peak.     

Microstructure and electrical properties of BaTiO<Subscript>3</Subscript> and (Ba,Sr)TiO<Subscript>3</Subscript> ferroelectric thin films on nickel electrodes

Nickel thin films have been sputtered on standard Si/SiO₂ substrates with TiO₂ as an adhesive layer. The thermal stability of these substrates was analyzed. SEM images show an increase in grain size with annealing temperature. They were found to be stable till 800°C, beyond which the nickel layer disintegrated. These substrates were used for deposition of BaTiO₃ and (Ba,Sr)TiO₃ dielectric thin films under a reducing atmosphere. The dielectric thin films were processed with various pyrolysis and annealing temperatures in order to optimize the dielectric properties. Increased pyrolysis temperatures showed an increase in the grain size. Results on these nickelised substrates were finally compared with dielectric films deposited on platinized silicon substrates under identical conditions but crystallized in an oxygen atmosphere.     

Tribological properties of multilayer nanostructure TiO2 thin film doped by SiO2

Multilayer of TiO₂ and TiO₂:SiO₂ thin films were grown on a glass substrate by sol?Cgel processes, followed by high temperature treatment at 500?°C. The fine grained TiO₂ films controlled by SiO₂ dopant showed very good wear resistance and endurance life. Energy dispersive X-ray spectroscopy was used to indicate the elements in the films. X-ray diffraction analyses indicated that TiO₂ and TiO₂:SiO₂ film contain only anatase phase. The morphologies of the original and worn surfaces of the samples were analyzed by means of scanning tunneling microscope and scanning electron microscopy. The tribological properties of TiO₂ and TiO₂:SiO₂ thin films sliding against AISI52100 steel pin were evaluated on a pin on disk friction and wear tester. The results showed that 25-layer TiO₂:SiO₂ films are superior in reducing friction and resisting wear compared with the glass substrate.     

Surface modification of thermoplastics by atomic layer deposition of Al2O3 and TiO2 thin films

Al₂O₃ and TiO₂ thin films were deposited by atomic layer deposition at 80-250 °C on various polymeric substrates such as polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE) and ethylenetetrafluoroethylene (ETFE). The films were studied with FESEM, EDX, XRD, contact angle measurements and adhesion tests. The film growth rates on the thermoplastics were close to the corresponding growth rates on Si substrates. The adhesion of the films was good on PEEK and poor on PTFE. All coated surfaces showed lower water contact angles than the uncoated thermoplastics. Furthermore, the water contact angles on all TiO₂-coated surfaces decreased upon UV illumination, most efficiently with crystalline TiO₂ coatings.     

Probing interfacial interactions of nafion ionomer: Thermal expansion of nafion thin films on substrates of different hydrophilicity/hydrophobicity

Interfacial interactions of Nafion ionomer with superhydrophilic (Pt, Au), hydrophilic (SiO₂), and hydrophobic (graphene, octyltrichlorosilane [OTS]‐modified SiO₂) is investigated, using in situ thermal ellipsometry, by quantification of substrate‐ and thickness‐dependent thermal properties of the ultrathin Nafion films of nominal thickness ranging 25–135 nm. For sub‐50 nm thin Nafion films, the thermal expansion coefficient of films decreased in the order of most hydrophobic to most hydrophilic substrate: OTS > graphene > SiO₂ > Au > Pt, implying weaker interpolymer and polymer–substrate interactions for films on hydrophobic substrates. Expansion coefficient of films on SiO₂, graphene, and OTS‐modified SiO₂ decreased with thickness whereas that of films on Au and Pt substrates increased with thickness. Above ~100 nm of thickness, films on all substrates converged toward a common value representative of bulk Nafion. Thermal transition temperature was found to be higher for films on hydrophilic SiO₂ than that for films on hydrophobic graphene and OTS‐modified SiO₂ but was not discernible for films on Au and Pt substrates. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 343–352     

Surface treatment of 25‐μm Kapton film by ammonia for improvement of TiO2/SiO2 coating's adhesion

Due to a smooth hydrophobic surface of Kapton film, it is very difficult to coat an inorganic oxide coating on its surface. In this study, the surface of Kapton was treated by NH₃·H₂O and silicon coupling agent to improve the polymer surface wettability. Changes in surface hydrophilicity were studied by contact angle measurement. The samples were irradiated by atomic oxygen (AO) in a ground‐based simulation system. TiO₂/SiO₂ multi‐layer coatings were prepared on the surface of Kapton by sol–gel method to resist AO erosion. The optical transmittance and surface morphology of samples were investigated by UV–vis spectroscopy and scanning electronic microscope. The results indicated that the TiO₂/SiO₂ sol could easily form a uniform thin coating on the surface of pretreated Kapton. After AO exposure, the coatings became more compact, without peeling off. The AO erosion yield value of coated Kapton was sharply down, and the samples had good optical transparency. Copyright © 2017 John Wiley & Sons, Ltd.     

Preparation and Z-Scan nonlinear optical characterization of Au/SiO2- and Ag/SiO2-supported nanoparticles dispersed in silica sonogel films

Au/SiO₂ and Ag/SiO₂ supported metal-nanoparticles (MNPs) were implemented to fabricate SiO₂-based inorganic?Cinorganic hybrid sonogel films. Prepared Au/SiO₂- and Ag/SiO₂-MNPs exhibited low 2D-HCP crystallinity with particle diameters below 10?nm and homogeneous size distribution. The catalyst-free (CF) sonogel route was successfully implemented to produce these optically active nanocomposite films by doping the liquid sol-phase with these MNP systems and its subsequent deposition onto glass substrates via standard spin-coating procedures. The easy MNP-loading within the mesoporous dielectric sonogel network evidenced a huge chemical affinity between the silica sonogel hosting system and the guest SiO₂-supported MNPs. This fact allowed us to fabricate high quality hybrid films suitable for cubic nonlinear optical (NLO) characterizations via the Z-Scan technique. Indeed, the hosting sonogel network provided adequate thermal and mechanical stability protecting the active MNPs from environment conditions and diminished their tendency to aggregate; thus, preserving their pristine optical properties and morphology, giving rise to stable sol?Cgel hybrid films appropriate for photonic applications. Comprehensive morphological, structural, spectroscopic and nonlinear photophysical characterizations were optimally performed to the developed hybrid films. Our results have shown that the crystalline nature of the implemented MNPs, their small sizes and appropriate guest?Chost stabilizing interactions play a crucial role in the observation of improved cubic NLO-properties of these MNP structures embedded within the highly pure CF-sonogel confinement.     

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.