Catalytic Effects of Aluminum Butoxyethoxide in Sol-Gel Hybrid Hard Coatings

Hybrid inorganic-organic hard coatings on PMMA substrate were obtained by sol-gel reaction of 3-glycidoxypropyltrimethoxysilane(GPTS), tetramethyl orthosilicate(TMOS) and aluminum butoxyethoxide (Al(OEtOBu)₃). The catalytic effect of aluminum butoxyethoxide on inorganic condensation and epoxide polymerization has been studied by ¹³C, ²⁹Si nuclear magnetic resonance spectroscopy and by Fourier transformed infrared spectroscopy. Hardness of hybrid inorganic-organic materials were measured by nanoindentor and mainly influenced by the extent of epoxide polymerization and inorganic condensation of their coating catalyzed by aluminum butoxyethoxide.     

有机-无机杂化溶胶-凝胶涂层对不锈钢毛细管柱的脱活作用研究

 用甲基三乙氧基硅烷和四乙氧基硅烷水解缩合后形成的有机 无机杂化溶胶 凝胶 (sol gel)涂层对国产气相用不锈钢毛细管柱进行脱活。通过气相法研究了不同老化温度下所得脱活涂层的行为。结果表明这种涂层不但对不锈钢柱内壁活性点有很好的遮盖作用 ,而且本身具有相当的分离能力。在 2 5 0℃下老化的涂层可使碳原子数在 12以下的正构烷烃达到基线分离 ,与未用涂层的不锈钢裸柱相比 ,吸附活性大大降低 ;但随着老化温度的升高 ,涂层在缩聚老化过程中产生不均匀微孔 ,对被分离物的作用力加强。     

Industrial Application of Hybrid Sol-Gel Coatings for the Decoration of Crystal Glassware

The coloration of glass via melting techniques presents some unique problems with respect to the reproducibility, toxicology and economics of certain colors, especially if the market demands are highly variable. This is also the case for consumer products such as crystal glass and tableware. Traditionally, the decoration of crystal glasses is performed by laborious manual techniques, which are costly and do not meet modern market requirements. Alternatively, spraying of colored lacquers is a highly flexible and valuable tool for the development of new products. Sol-gel type hybrid coatings provide several advantages compared to conventional organic systems like high abrasion resistance, almost perfect adhesion, refractive index matching and sufficient stability in dishwashing procedures. The solubility of organic dyes in the hybrid matrix is sufficient for intense colors even at rather low layer thicknesses, which on the other hand convey the high brilliance of the base material. The development of transparent, translucent and opaque hybrid coatings for crystal glass has been completed in the last few years and the production of partially coated articles has started recently. The synthesis and properties of the coating material are reviewed and the industrial process and first market results are also outlined.     

Sol-Gel Processing of Organic-Inorganic Nanocomposite Protective Coatings

Organic-inorganic nanocomposite protective coatings are prepared on aluminum substrates by the spinning technique with the concept of incorporating homogeneously nanosized particles (of AlOOH, Al2O3, ZrO2, SiC) into molecular organic-inorganic hybrid matrices. The hybrid matrices are prepared from epoxysilane and bisphenol A with imidazol as catalyst. The AlOOH particles are derived from aluminum isoprooxide and introduced into the hybrid sols directly, and Al2O3, ZrO2, SiC particles are first surface-modified with Si–OH from hydrolyzed TEOS. The coatings are dense, smooth and flexible and inhibit corrosion.     

溶胶-凝胶法制备有机/无机杂化材料工艺及其应用

介绍了溶胶–凝胶法制备有机/无机杂化材料的原理和基本过程,杂化材料的制备方法及对材料性能的影响,概述了杂化材料在结构材料、光学材料及其它材料中的应用研究。     

Hybrid Pigments via Sol-Gel Processing

The incorporation of organic dyes into inorganic and hybrid sol-gel derived materials is a valuable method for the fabrication of colored layers for optical applications like filters, solar energy conversion, non-linear optical devices, and active laser media. There have been clear hints for photochemical stabilization of the organic dyes, therefore, our aim was to investigate the light stability of organic dyes within hybrid solids. Besides the traditional way of doping sol-gel coatings with dyestuffs, they were also covalently attached to the hybrid matrix and pigments were produced by spray-drying processes.The resulting spherical powders were investigated with respect to their morphological, structural and photochemical properties. The results show that uniformly shaped and colored hybrid pigments can be synthesized. The spectroscopic studies demonstrate the fixation of the dye to the matrix and the high degree of crosslinking achieved in the composite. Additionally, the hybrid pigments drastically improve the resistance of the dye against bleeding from thermoplastic polymers. Furthermore, a higher photochemical stability of the dye is observed within the hybrid matrix compared to a solution, and purely organic or inorganic solid hosts.     

Synthesis and Characterization of Transparent Hydrophobic Sol-Gel Hard Coatings

It is challenging to make a transparent hydrophobic hard coating when soft hydrophobic additives are added into the coating system. Material non-homogeneity due to phase separation, non-durable hydrophobicity and deteriorated transparency are the main issues. In this paper, we describe a chemical formulation, which contains a pre-linked hydrophobic cluster and a silica hard matrix with silica hard fillers so that the hydrophobic property and hardness can be tuned separately and optimized. The transparency of the coating is found to be related to the effective modification of the reactive titanium tetraisopropoxide (TIP) precursor by ethyl acetoacetate (EacAc) and the right ratio between TIP and polydimethylsiloxane (PDMS) (≤0.5). The water contact angle is increased to a maximum of 133° when 50 Vol% of PDMS is added into the silica matrix. The hardness of coating is proportional to silica filler content and curing temperature, and inversely proportional to PDMS Vol%. 30 Vol% silica filler in silica matrix and curing temperature at 300°C result in the best hardness in this study. Hardness at 50 Vol% PDMS dropped to 0.2 GPa from 0.85 GPa of pure silica coating. The Vol% of PDMS and silica filler will be further optimized in our next stage experiments.     

The Nanocrystalline Ceria Sol-Gel Coatings for High Temperature Applications

Sol-gel technology was utilized to produce nanocrystalline thin films of CeO₂ on substrates with different oxidation resistance at high temperatures. After deposition, the coatings were composed of CeO₂ crystallites with a size of 5 nm, randomly oriented on all the substrates. The annealing of gel deposited on Pt and Si substrates was accompanied by evaporation of water and other species and followed by growth of crystallites, without formation of any evident texture. Conversely, the annealing of coatings deposited on easy oxidizing substrates of Nr, Cr, or Ni−Cr alloys resulted in incorporation of CeO₂ crystallites into growing native oxide, and in slowing the oxidation rate. Examples of the application of CeO₂ ceramics as coatings deposited on selected metals and alloys for improving their oxidation performance are presented.     

Bonding Strengths of Titania Sol-Gel Derived Coatings on Titanium

Bioactive ceramic coatings have had poor adhesion to substrate. In this study, the bond strength (tensile strength) of titania gel coating to titanium substrate was studied. In the experiments three different pretreatments were used, namely sodium hydroxide corroding, plasma cleaning and titanium nitride coating. Also the effects of heating temperature, heating in vacuum and titanium surface roughness were studied. The sol properties were altered with valeric acid addition. Samples were analysed by SEM-EDX, AES, AFM and tested by bond strength gauge. Those samples in which the titanium surface was precorroded one hour in sodium hydroxide, predeposited by titanium nitride or ground improved the bonding strengths of titania coatings to over 24 MPa. In these samples a fracture occurred at the glue-coating interface.     

Preparation of Silica-Based Inorganic-Organic Hybrid Membrane via the Sol-Gel Route

Silica-based inorganic-organic hybrid membranes have been prepared on porous -Al₂O₃ substrate (pore size, 2 m) using tetraethoxysilane (TEOS) and phenyltrimethoxysilane (PTMOS) as precursors. The effects of sol synthesis conditions on the processing and performance of deposited hybrid layers were observed. The thickness of the hybrid layers after three deposition cycles is about 2 m, estimated from their cross-section SEM micrographs. The gas permselectivity of the hybrid membrane was characterized by O₂/N₂, CO₂/N₂, and CO₂/O₂ mixing gases, which was mainly governed by the surface diffusion at lower pressures and Knudson diffusion at higher pressures. The introduction of phenyl groups can not only improve the selectivity of O₂/N₂ and CO₂/N₂, but also densify the membrane network.     

Optical Properties of Sol-Gel Coatings on Plastic Foils Embossed with Surface-Relief Gratings

A novel technique has been developed to fabricate surface-relief gratings using sol-gel derived porous coating on plastic foil substrates. Organically modified TiO₂ sol was prepared by roll-coating on OPP foil substrates. The plastic films coated with TiO₂ nano-particles were embossed to form surface-relief gratings with micro-structures. The morphology of the porous coatings and the micro-structures were investigated using electron scanning microscopy (SEM). Optical transmission of the films was measured using UV-VIS and IR spectroscopy. The diffraction efficiency of the gratings on the coated plastic foil was examined in terms of fabrication conditions. It was shown that special figures could be seen in the films when the angle of view was changed. The final products of the composite films are transparent and suitable for industry manufacture and applications.     

Hybrid Organic-Inorganic Sol-Gel Materials Based on Epoxy-Amine Systems

Understanding the synthesis-structure-properties relationship of hybrid organic-inorganic materials is an important and fundamental task to develop a new generation of highly performing systems for the new needs of nanotechnologies. This issue is, also, important to improve the properties of hybrids when used in applications where nanoscale control is not a fundamental request. In this article, a short overview of epoxy amine sol-gel hybrids is reported. The synthesis of these materials has a large flexibility to allow the fabrication of a wide group of hybrids with different structures and properties, whose applications are ranging from non-linear optics to adhesive and protective coatings.     

Thickness, Morphology and Structure of Sol-Gel Hybrid Films: I—The Role of the Precursor Solution's Ageing

The physical properties of inorganic-organic sol-gel hybrid films are determined by a large number of processing parameters, as the initial recipe, the catalysis conditions and the film deposition technique. This work focuses on the influence of the precursor solution's ageing on the quality and structure of hybrid silica-polytetrahydrofuran films, prepared by spin coating. The inorganic precursor, tetraethylorthosilicate, was hydrolysed under acid catalysis and using ethanol as co-solvent. The hydrolysis molar ratio (R) was fixed at 4. Different polymer concentrations of two average molecular weights (M _n = 650 and 2900) were added to the initial colloidal solutions. Ageing took place in open containers. The thickness and surface texture parameters of the films were determined by profilometry, and their structures studied by FTIR. It is shown that the films' thickness increases with the ageing of the precursor solution, more steeply for the hybrid films with higher polymer content and higher M _n. The best films obtained, which present the highest thickness and the lowest relative roughness, are those prepared from the most aged solutions. The FTIR results show that the films' porosity increases with the ageing of the precursor solution, and that the distribution of oligomeric species in solution is maintained upon film deposition. Therefore, the structure of the film is essentially determined by the extension of the condensation reactions until the spinning moment.     

Modification of Thermo-Optic Characteristics of Sol-Gel Inorganic-Organic Hybrid Materials

The effect of the inorganic oxide network on the variation of thermo-optic characteristics (dn/dT) in inorganic-organic hybrid material prepared through the sol-gel process was investigated. The dn/dT values were negative for all samples, and decreased in magnitude with the increasing concentration of the inorganic oxide or heterometallic oxide network. The dn/dT also became less negative with the increase in the degree of inorganic condensation in sol-gel reaction. A negative dn/dT value is consistent with thermal expansion of the material, and it is believed that the value of the dn/dT in our inorganic-organic hybrid materials was principally sensitive to variations in expansion term.     

Optical Nonlinearity of Hybrid and Nanocomposite Materials Prepared by the Sol-Gel Method

In this paper the nonlinear refractive index, optical limiting effect, photoinduced and electroinduced second harmonic generation of dye-doped hybrid and nanoparticle-doped composite materials prepared by the sol-gel process have been reported. The origin of these nonlinear optical effects has been discussed.     

Sol-Gel Derived Coatings for Outdoor Bronze Conservation

A new conservation treatment for outdoor bronze sculptures based on inorganic-organic copolymers (ORMOCER^®s) was designed which meets the special requirements defined for this field of conservation. Following a systematic research strategy, a great variety of starting compounds (main components: 3-glycidoxypropyltrimethoxysilane or γ-methacryloxypropyltrimethoxysilane), curing conditions, hardeners and additives were considered for modifying the sol-gel materials. The characterization of the lacquers included IR, GPC and viscosity measurements as well as water and epoxy titrations. Screening was carried out by evaluation of the protective effect on bronze substrates. The material properties of the coatings were adjusted to optimize adhesion and resistance against weathering. Particular emphasis was given to curing the sol-gel polymer at ambient temperatures while retaining reversibility even after aging.     

Polyaniline/Silica Hybrid Composite Gels Prepared by the Sol-Gel Process

The preparation of polyaniline/silica hybrid gel was studied by chemical polymerization of aniline with sodium dodecyl sulfate (SDS) during the sol-gel processing. As a typical procedure, aqueous solutions of SDS, aniline, HCl, and tetramethoxysilane (TMOS) were mixed. Then ammonium peroxodisulfate (APS) in an acidic aqueous solution was added as initiator oxidant into the sol-gel systems at different sol-gel stages: (A) just after mixing (sol), (B) after gelation (wet gel), and (C) after 7 d (dried gel). As for the condition (A), several green areas and several tens of dark green spots with absorption peaks at 343, 422, and 802 nm were seen in the xerogel, indicating that emeraldine salt type polyaniline is aggregated in the silica xerogel. Polymerization of aniline little occurred in the dried gel (C), possibly because APS could not soak the silica pores and/or aniline could not polymerize in the gel. The xerogel from (B) showed a homogeneously green color with peaks at 339, 425, and 769 nm, showing that emeraldine salt type polyaniline can be uniformly dispersed in sol-gel silica.     

Basic Catalyzed Synthesis of Hybrid Sol-Gel Materials Based on 3-Glycidoxypropyltrimethoxysilane

Hybrid organic-inorganic materials derived from 3-glycidoxypropyltrimethoxysilane have been synthesised using 3-aminoethylaminopropyltriethoxysilane as basic catalyst of epoxy polymerisation and modifier of the structure.Different amounts of aminoethylaminopropyltriethoxysilane have been used to prepare films and bulk samples, from 17 to 48 mol% with respect to the alkoxide content. The materials have been characterised by Fourier Transform Infrared, Raman and multinuclear solid-state Nuclear Magnetic Resonance spectroscopy.Complete opening of epoxy rings in 3-glycidoxypropyltrimethoxysilane has been obtained and the different amounts of catalysts employed directly affected the degree of inorganic cross-linking.     

Fluorescence of Pyranine in Sol-Gel Based Silica and Hybrid Thin Films

The sensitivity of the pyranine fluorescence to protonation/deprotonation is used to follow modifications in cured sol-gel thin films. The acid concentration in the sol-gel solution is varied for TEOS-based coatings and a series of organically modified silanes Si(OR)₃R’ are added to the TEOS solution. The concentration of the organically modified silane is varied as well as the chain length of the alkylgroup (R’). The stationary fluorescence measurements show that the equilibrium between the protonated and the deprotonated form of pyranine changes depending on the type of silica matrix. The deprotonated form is dominant in the cured SiO₂ films and the protonation/deprotonation ratio of pyranine is constant for the different acid concentrations used. The protonated form becomes dominant as the concentration of Si(OR)₃R’ is increased and as the alkyl chain length (R’) of the organically modified silanes is augmented. Emission anisotropy measurements of pyranine in the same coatings show that the rotational freedom of the molecule changes due to modifications in the cages for the TEOS-based coatings. These modifications are produced by the acid concentration used to prepare the coatings. An increase in the rotational freedom of pyranine is observed in the TEOS-Si(OR)₃R’ systems.