Anti-Reflective Coatings for CRTs by Sol-Gel Process

Anti-reflective and electromagnetic shielding double-layered coatings were developed for cathode ray tubes (CRTs) by wet chemical process. An outer SiO₂ layer is formed over a porous inner tin-doped indium oxide (ITO) particle layer. ITO particles used in the inner layer lower the sheet resistance below 10³ohm/sq. and an electromagnetic shielding property is attained. To improve the abrasion wear resistance of the film, the structure of the film and hydrolysis-polymerization condition of tetraethoxy-silane (TEOS) are estimated. An outer SiO₂ layer component penetrates into the inner layer and adheres to the glass surface. As the extent of hydrolysis of TEOS proceeds and the molecular weight of hydrolyzed TEOS becomes small, the abrasion wear resistance of the film enhances. The relation between the curing condition of the film and surface resistance of the film is investigated. The surface resistance of the film lowers by curing the film in reductive atmosphere. The transmittance of the film in the near-infrared region shows that the lowering of surface resistance of the film is caused by the increase of carrier concentration of ITO particles. The double layered coatings are successfully applied to the panel glass for CRTs on an industrial-scale.     

Soft solution synthesis of a zinc oxide nano-screw superstructure and its composite with nitrogen-doped titania

Novel zinc oxide thin films with nano-screw superstructure were prepared via a soft solution route without any polymer additives. A ZnO thin film could be produced directly on the substrates. The ZnO thin film with nano-screw superstructure was prepared using visible-light-induced nitrogen-doped titania nano-particles. The ZnO nano-screw/TiO_2−x N _y composite film showed excellent photocatalytic deNO _x ability and quantum efficient.     

Dielectric properties of Al–Si composite oxide films formed on electropolished and DC-etched aluminum by electrophoretic sol-gel coating and anodizing

Highly pure aluminum specimens (99.99%) after electropolishing and DC-etching were covered with SiO₂ films by electrophoretic sol-gel coating and were anodized in neutral boric acid/borate solutions. Time-variations in cell voltage during electrophoretic sol-gel coating and in anode potential during anodizing were monitored. Structure and dielectric properties of the anodic oxide films were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), and electrochemical impedance spectroscopy (EIS). It was found that electrophoretic sol-gel coating forms uniform SiO₂ films on the surface of both electropolished and DC-etched specimens. Anodizing of specimens after electrophoretic coating lead to the formation of anodic oxide films consisting of two layers: an inner alumina layer and an outer Al–Si composite oxide layer. The anodic oxide films formed, thus, had slightly higher capacitances than those formed on aluminum without any coating. Higher heating temperatures after electrophoretic deposition caused the increase in capacitance of anodic oxide films more effectively. Anodizing in a boric acid solution after SiO₂ coating on DC-etched foil allowed the anode potential to reach a value higher than 1,000 V, resulting in 39% higher capacitances than those on specimens without SiO₂ film. Dedicated to Professor Su-Il Pyun on the occasion of his 65th birthday.     

Preparation of Cr‐doped TiO2/SiO2 Photocatalysts and their Photocatalytic Properties

Cr‐doped TiO₂/SiO₂ nanostructured materials were prepared employing a layer‐by‐layer assemblym technique. TiO₂ colloids were synthesized by a sol‐gel method using TiCl₄ as a precursor. The experimental results showed that sphere‐type TiO₂ particles on SiO₂ exhibited uniform shape and a narrow size distribution. The amount of Ti (wt %) increased as a function of the number of the coating layers. The coatingv layers was composed of anatase titania nanocrystals at 550 °C. The onset of band‐gap transition for Crdoped TiO₂/SiO₂ showed a red shift compared with that for the undoped TiO₂/SiO₂. And the photocatalytic activity of Cr‐doped TiO₂/SiO₂ was higher than that of undoped sample.     

Sol-enhanced triple-layered Ni–P–TiO2 composite coatings

A novel coating process, TiO₂ sol enhanced Ni–P electroless composite coatings on carbon steel, is presented in this paper. Transparent TiO₂ sol was added into the electroless plating Ni–P solution at a controlled rate, leading to in situ synthesis of a triple-layered Ni–P–TiO₂ composite coating, i.e. the inner, transition and outer layers. The inner layer has a thickness of ~3 μm, mainly composed of Ni and P elements. The transition layer of the coating has a relatively high content of TiO₂ with a thickness of ~500 nm and a columnar-structure. The thickness of the outer layer was ~7 μm, with almost evenly distributed Ni, P and TiO₂. The hardness and Young’s modulus of the composite coating were greatly improved to ~10 and ~200 GPa, respectively, compared to ~6 and ~110 GPa of the traditional Ni–P coating.     

Photoelectrochemical Study of Anodic Oxide Films on Titanium–Cobalt Alloys

Properties of anodic oxide films as a function of the composition of Ti _x –Co (x= 0, 10, 20, 30, 50, 67, 75 at. %) alloys in solutions of a borate buffer and sodium sulfate are studied by the voltammetric technique combined with photocurrent measurements. The oxide film on the alloys is shown to contain TiO₂and Co₂O₃. In a borate buffer, the oxide film presumably comprises two layers: an outer layer of cobalt oxides and an inner layer of a mixture of cobalt and titanium oxides.     

Sol-gel thin films with anti-reflective and self-cleaning properties

Self-cleaning photocatalytic TiO₂ films are beneficial since they reduce the maintenance cost and enhance the efficiency of various optical systems, especially thermal and photovoltaic solar systems. However, the presence of a TiO₂ layer on glass reduces the transmission of incident light, which leads to a decrease in efficiency. This drawback can be overcome by applying a layer of anti-reflective coating beneath the TiO₂ layer. Generally, the anti-reflective layer is porous silica. The presence of the anti-reflective layer compensates for the loss of light transmittance caused by the photocatalytic TiO₂ top layer. This paper reviews some of the previous and the latest fundamental studies in the literature on anti-reflective, self-cleaning and multi-functional films.     

Methyltriethoxysilane-derived sol-gel coatings doped with silver metal particles

Silica sol-gel films were prepared by dipping, starting from an acid catalyzed solution of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS). Silver metal nanoparticles were produced in the silica layer by introducing in the sol-gel precursor solution AgNO₃ or AgClO₄·H₂O. The silver ions were thermally reduced in air at 800°C, giving an intense yellow coating film. The silver metal particles were observed by transmission electron microscopy and X-ray diffraction. The diameter of the silver particles was found to be about 10 nm. Absorption measurements in the UV-Vis were used to evaluate the volume fraction of silver colloids embedded in the silica layer.     

Photochromic Coatings Containing Ag(Cl1−xBrx) Microcrystals

Photochromic ormosil coatings containing Ag(Cl_1–x Br _x ) microcrystals were formed on a glass substrate via the sol-gel process. Methyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane were used as starting materials of the ormosil matrices. 3-chloropropyltrimethoxysilane and bromophenyltrimethoxysilane were added as halogen sources and silver colloidal dispersion was introduced into the precursor sol. The coated glass became transparent and photosensitive after Ag(Cl_1–x Br _x ) microcrystals were precipitated in the coatings above 300°C. Insertion of a SiO₂ buffer layer between the substrate and photochromic layer was effective in preventing Ag⁺ migration into the substrate. Photochromic performances were improved by the substitution of Cl with Br and the incorporation of a minute amount of Cu.     

TiO2 nanoparticles synthesized in an aprotic solvent and applied to prepare high-refractive-index TiO2-polyimide hybrid thin films

In this study, very small (2–5 nm) TiO₂ nanoparticles were synthesized in an aprotic solvent, N,N-dimethylacetamide, via hydrolysis and condensation of titanium alkoxide at room temperature. The synthesized TiO₂ sol showed 30 days of storage stability and could be used to prepare high-refractive-index TiO₂-polyimide hybrid thin films by an ex-situ method that involved a spin coating and multistep baking process. The field emission scanning electron microscope image showed a flat and uniform morphology of the hybrid thin film. TiO₂ domains were in the nanometer range, thus avoiding light scattering. The refractive index at 633 nm of the hybrid thin film reached 2.05, which suggested potential applications of the film to anti-reflective coatings and optical waveguides.     

Hydrophobic and Oleophobic Epoxy Surfaces Prepared by a Facile Process with Fluorosilicone Copolymer and SiO2 Nano-Particle

Hydrophobic and oleophobic surfaces with multi-scale structures were prepared on epoxy coating surfaces by using a facile process with fluorosilicone copolymer and SiO₂ nano-particles. The fluorosilicone copolymers were synthesized using perfluoroalkyl acrylate (FA), vinyltriethoxysilane (VTES) and styrene (St) as comonomers via radical emulsion polymerization. In this paper, the surface properties of epoxy coating modified by fluorosilicone copolymer and SiO₂ nano-particles were analyzed by using the contact angle measurement. The results showed that the modified epoxy coating surface exhibited not only excellent hydrophobicity but also oleophobicity, the water contact angle reached as high as 149° and the oil (atoleine) contact angle 101°, respectively.     

Influence of YSZ buffer layer on the electric properties of compositionally graded (Ba,Sr)TiO<Subscript>3</Subscript> thin film

Compositionally graded Ba_1−x Sr _x TiO₃ (BST) (0 ≤ x ≤ 0.4) thin films were fabricated on Pt/Ti/SiO₂/Si and YSZ/Pt/Ti/SiO₂/Si substrates by a modified sol–gel technique. The YSZ buffer layer was prepared by RF magnetron sputtering. The microstructure of the graded BST films was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results showed that all the films have uniform and crack-free surface with a perovskite structure. The graded BST film with an YSZ buffer layer has larger dielectric constant and lower dielectric loss. The leakage current density of the graded BST film with an YSZ buffer layer lowers two orders than the film without buffer layer. The improved electric properties of the graded films with an YSZ buffer layer was attributed to the YSZ buffer layer act as an excellent seeding layer to enhance the graded BST film growth.     

X-ray spectroscopic study of the electronic structure of boron carbonitride films obtained by chemical vapor deposition on Co/Si and CoO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/Si substrates

Boron carbonitride films are synthesized by chemical vapor deposition from a mixture of triethylamine borane and ammonia on a metallic or oxidized cobalt sublayer sprayed over Si(100) substrates. Scanning electron microscopy shows that the surface of a BC _x N _y /Co/Si sample has a homogeneous fine-grained structure; filamentous entities are found on the surface of the BC _x N _y /CoO _x /Si sample. The electronic structure of the films is investigated by X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). An analysis of the spectra shows that BC _x N _y films are composed of graphite and hexagonal boron nitride (h-BN) regions and complex BC _x N _y O _z components with B-C, N-C, B-O, N-O, and C-O bonds. The deposition of the BC _x N _y film on the oxidized Co sublayer results in an increase in the number of C-O, N-O, B-O, and C-N bonds and a decrease of the graphite and h-BN components and in the number of C-B bonds. The XPS data are used to estimate the surface elemental composition of the BC _x N _y /CoO _x /Si sample. It is found that the film consists of 66 at.% graphite component and 3 at.% h-BN; the proportion of complex C_0.46B_0.11N_0.05O_0.38 components is 31 at.%.     

Preparation of lead and tin oxide thin films by spin coating and their application on the electrodegradation of organic pollutants

In this work, lead and tin oxide films (Pb _x O _y /SnO₂) were prepared, using the spin coating technique. The influence of the temperature and duration of the thermal treatment on the final film composition were analysed. The metallic oxide films that were prepared, Pb _x O _y /SnO₂, were characterized by means of XRD, SEM/EDS and cyclic voltammetry. When different experimental preparation conditions were used different lead oxide phases were obtained. The electrochemical studies show that the films are stable and can be used as electrodes. Finally the films were tested as electrodes for the electrochemical degradation of a CHCl₃ aqueous solution.     

Correlation of SiO x layer thickness and properties of BOPP/SiO x composite films with spin coating process parameters

The effects of the spin coating process parameters on the thickness of the SiOx layer of the BOPP/SiOx composite film were investigated. When the concentration of tetraethoxysilane (TEOS) increased from 12.5 vol% to 55% vol%, the SiOx thickness increased from about 80 nm to 470 nm. In the sol time range of 1.5 h to 5 h the SiOx layer thickness reached a maximum at about 4 h and the change of the thickness roughly matched the change of the silica colloidal sphere sizes in sol. When the spin-coating speed of the dispensing stage increased from 450 r/min to 500 r/min, the SiOx layer thickness drastically decreased from about 1.67 μm to 400 nm. While the spin-coating speed of the thinning and drying stage went up to 1200 r/min, the SiOx layer thickness was in the range of 330 nm to 390 nm. It was also found that the SiOx layer thickness was almost increased linearly from about 500 nm to 1.02 μm with the ratio of the commercial silica colloidal to the TEOS from 0.2 to 1.0. The water contact angles decreased to about 23.0° for the BOPP/Si-Sol composite film with 1.67 μm SiOx layer and about 4.0° for the BOPP/mixing Si-Sol composite film with 1.02 μm SiOx layer. Compared to BOPP, the light transparency of the BOPP/Si-Sol composite films decreased by about 5.5% with the SiOx layer from about 80 nm to 1.67 μm and by 7.0% for the BOPP/mixing Si-Sol composite film with the SiOx layer from about 350 nm to 1.02 μm respectively.     

Hydrogen Production by Water Dissociation in Surface‐Modified BaCoxFeyZr1−x−yO3−δ Hollow‐Fiber Membrane Reactor with Improved Oxygen Permeation

A porous perovskite BaCo_xFe_yZr_0.9?x?yPd_0.1O_3?δ (BCFZ‐Pd) coating was deposited onto the outer surface of a BaCo_xFe_yZr_1?x?yO_3?δ (BCFZ) perovskite hollow‐fiber membrane. The surface morphology of the modified BCFZ fiber was characterized by scanning electron microscopy (SEM), indicating the formation of a BCFZ‐Pd porous layer on the outer surface of a dense BCFZ hollow‐fiber membrane. The oxygen permeation flux of the BCFZ membrane with a BCFZ‐Pd porous layer increased 3.5 times more than that of the blank BCFZ membrane when feeding reactive CH₄ onto the permeation side of the membrane. The blank BCFZ membrane and surface‐modified BCFZ membrane were used as reactors to shift the equilibrium of thermal water dissociation for hydrogen production because they allow the selective removal of the produced oxygen from the water dissociation system. It was found that the hydrogen production rate increased from 0.7 to 2.1 mL H₂ min^?1 cm^?2 at 950 °C after depositing a BCFZ‐Pd porous layer onto the BCFZ membrane.     

Spectral properties and microstructure of sputtered WOx films for solar conversion applications

Tungsten oxides (WO_x) films have gained promising attention in terms of selective solar absorption due to its high intrinsic absorption properties. We fabricated a series of single-layer WO_x films on aluminum substrates by a magnetron sputtering system. The optical absorption properties of the film were investigated by spectrophotometer and ellipsometry. We found that the optical properties of the film were very sensitive to the change of the thickness. The result showed the highest α value can reach up 0.82 with the thickness of 26 nm at 0.6 Pa or 70 nm at 1.5 Pa, and both ε values was around 0.05, indicating the high spectral selectivity properties. The different reflectance evolutions presented a wide range of color appearances, such as yellow, reddish, cyan, and blue. Moreover, the surface morphologies and phase structures of single-layer WO_x films were investigated by SEM, XRD, and Raman. A WO_x/SiO₂ solar selective absorber coating indicated that the as-obtained WO_x film was a promising application in solar-thermal conversion.     

TiO<Subscript>2</Subscript>/TiO<Subscript>2−<Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> nanocomposite and its acetaldehyde photodecomposition ability

Nitrogen-doped titania was coupled with the commercial titania nanoparticles by mechanical milling in liquid medium. The as-prepared nanocomposites (TiO₂/TiO_2−x N _y ) were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area, UV–Vis spectroscopy, chemiluminescence, and acetaldehyde decomposition activity techniques. When a small amount of nitrogen-doped titania was added into the commercial titania, higher intensity and longer lifetime of ¹O₂ was observed, and the photocatalytic activity was efficiently improved. The TiO_2−x N _y acts as the acceptor of photoinduced holes. The recombination of the electron-hole was effectively depressed by the heterogeneous electron transfer. This could be an effective way to obtain highly active photocatalysts.     

Matrix-Inducing Synthesis of SrxY10?x(SiO4)y(PO4)6?yO2: Eu3+ Micron Crystalline Coral Like Phosphors by Sol-Gel Composition of Hybrid Precursors

In the context, Sr_xY_10−x(SiO₄)_y(PO₄)_6−yO₂ doped with 1 mol%Eu³⁺ (x = 2, y = 6; x = 4, y = 4; x = 5, y = 3; x = 8, y = 0) were synthesized by using 3-aminopropyl-triethoxysilane (APES) as the sources of the silicate network. X-ray diagrams confirm that Sr_xY_10−x(SiO₄) _y(PO₄)_6−yO₂: Eu³⁺ solid solutions are formed as a pure apatitic phase. The SEM picture shows that there exist some novel unexpected coral like morphological structures. The luminescent intensity is the strongest for the host composition of Sr₄Y₆(SiO₄)₄(PO₄)₂O₂ although the effect of the composition on the luminescent intensity is little.     

Physico-chemical characterisation of zirconium-based self-bonded ETS-4 pellets

This paper reports a study of ETS-4 based self-bonded pellets, with several amounts of Zr moles in initial gel. The following gel composition is used: xNa₂O–0.6KF–1.28xHCl–yZrO₂–0.2TiO₂–1.49SiO₂–39.5H₂O with 0.5 ≤ x ≤ 2.5 and 0.015 ≤ y ≤ 0.12. The characterisation of obtained samples is carried out by XRD, thermal analysis, EDX and SEM. The results point out the possibility to synthesise ETS-4 zeotype with Zr in self-bonded pellets form. The importance of the amount and composition of the amorphous phase is underlined as binder of the ETS-4 crystals. Its amount is bigger at the outer face of the pellets, showing that the crystallisation occurred from the inner to the external face. Zirconium replaces titanium in the structure and its presence reinforces the mechanical resistance of the pellets.