Showing papers in "Journal of Sol-Gel Science and Technology in 1998"

Optical switching in vo2 thin films

Abstract: Vanadium dioxide thin films have been deposited from vanadium alkoxides VO(OR)3. An amorphous film is formed that transforms into crystalline VO2 upon heating at 500°C under a reducing atmosphere. Optically transparent VO2 thin films are then obtained that exhibit both electrical and optical switching around 70°C. The switching temperature together with the shape of the hysteresis loop can be modified by doping VO2 films with foreign cations. Doped MxVO2 (M = W6+, Nb5+, Ti4+, Cr3+ or Al3+) thin films have been prepared under the same conditions by mixing the vanadium alkoxide and a metal salt in an alcoholic solution. The switching temperature decreases when the film is doped with high-valent cations (W6+) and increases with low-valent cations (Al3+, Cr3+). The transition temperature first decreases and then increases when TiIV is added to the VO2 film while the width of the hysteresis loop is significantly reduced.

Sol-Gel Carrier Systems for Controlled Drug Delivery

Abstract: Embedding of the well-known coronary therapeuticum nifedipine into a modified silica matrix by the sol-gel technique allows its releasing behavior to be controlled to a high degree. The liberation rate is proportional to temperature and is increased by the addition of penetration agents such as sorbitol, but is inversely proportional to particle size and is decreased by modification of the silica matrix with methyl-triethoxysilane or polyethylene-glycol. It is presumed that the drug is dispersed in the gel matrix and that diffusion occurs through solvent-filled capillary channels. The liberation rate is governed by the relationship between the rates of dissolution and diffusion.

Aerogels—Recent Progress in Production Techniques and Novel Applications

Abstract: Aerogels are sol-gel derived nanostructured materials with extraordinary properties according to their high porosity. Though first prepared more than 60 years ago, silica aerogels became widely known only in the late 1980s when they were used in Cerenkov detectors and their potential was recognized as high performance thermal insulants. Nowadays, aerogel research has attracted many scientists from different fields, resulting in some 100 publications per year and the fifth aerogel symposium (ISA 5) in Montpellier/France in September 1997. This review will focus on recent developments in fast supercritical and ambient pressure drying processes. The state of the art with respect to structural characterization and measuring the material properties is reported including nondestructive techniques and alterations induced by invasive methods. A brief survey is given on modeling the aerogel structure and simulating properties. Special attention will be given to carbon aerogels and their organic precursors. Due to the high electrical conductivity of their graphitic backbone and the large specific inner surface areas, carbon aerogels can be considered ideal electrodes in supercapacitors and fuel cells.

Sol-gel coatings on 316l steel for clinical applications

Abstract: SiO2 and SiO2-CaO-P2O5 coatings have been prepared by dipping electropolished stainless steel 316L samples and microscope glass slides in three different sol-gel solutions Multilayered dense SiO2 coatings, and thick silica films obtained from equimolar contents of TEOS and MTES were used The latter were able to strongly reduce both the corrosion attack on the steel and the iron diffusion to the sample surface SiO2-CaO-P2O5 coatings were also obtained and applied onto the silica films, in order to provide a bioactive external surface for contact with living tissue In-vitro evaluation of these coatings and films is discussed

Influence of Precursor Chemistry on the Formation of MTiO3 (M = Ba, Sr) Ceramic Thin Films

Abstract: Thin films of BaTiO3 and SrTiO3 were prepared by a chemical solution deposition method. The impact of the precursor on the processing, on the microstructure, and on the dielectric properties has been studied by systematically varying the alkyl chain length of the used Ba- and Sr-carboxylates. In addition, the effect of stabilizing the Ti-alkoxide precursor by acetylacetone has been investigated. The decomposition process, the crystallization behavior, and the film morphology were analyzed by glancing incidence XRD, reflectance FT-IR and field emission SEM. Distinct precursor effects on the thin film morphology and properties were revealed. Part of this influence can be attributed to an intermediate complex carbonate phase which forms for selected carboxylates with short alkyl chains. The high transformation temperature of this intermediate phase to the perovskite obviously has a marked influence on the crystallization and densification process of the alkaline earth titanate thin films. We correlate the morphological differences of the films to their dielectric properties.

Molecular Control of Bioactivity in Sol-Gel Glasses

Abstract: Bioactive materials can be divided into: Class A bioactive glasses which exhibit rapid bonding to bone and soft connective tissue and are osteoproductive, and osteoconductive; and Class B bioactive ceramics, which bond slowly only to bone and are only osteoconductive. Bioactive sol-gel glasses composed of SiO2-CaO-P2O5 have Class A behavior in vitro and in vivo and also resorb as they enhance the proliferation of new trabecular bone.

Study of Hybrid Silica-Polyethyleneglycol Xerogels by Eu3+ Luminescence Spectroscopy

Abstract: Good optical quality Eu3+-doped silica-polyethyleneglycol hybrids were prepared by the sol-gel process. Thermomechanical analysis showed an increase of the glass transition temperature, due to the stiffness of the polymeric network, as the amount of Eu3+ increased. Europium luminescent properties were used to study structural evolution during the sol-gel transition. For lower doping concentrations dried gels present statistical distributions of Eu3+, typical of an amorphous environment, while for higher concentrations a crystalline-like environment of Eu3+ was observed. A broad emission band was observed in the visible part of the electromagnetic spectrum and assigned to the intrinsic emission from the hybrid polymeric network.

Structures, Properties and Potential Applications of Ormosils

Abstract: Ormosils are organic-inorganic hybrid solids in which the organic component may be chemically bonded to a silica matrix. Somewhat similar to inorganic silicate glasses, the structure of the silica network can be modified by the presence of organic groups. The resulting properties of the Ormosils are then governed by the type and concentration of organics used. Examples are presented in which the mechanical, electrical and optical properties of selected Ormosils can be influenced by organic groups. For instance, small amounts of polydimethylsiloxane (PDMS) added to a solution of TEOS will give an Ormosil about ten times harder than the hardest organic polymer. Larger amounts of PDMS (20%) will now yield an Ormosil which is as rubbery as organic rubber. Ormosils in which the organic and inorganic constituents are covalently bound to each other are the focus of this critical review. The potential applications of such Ormosils are discussed.

A NMR study on the hydrolysis, condensation and epoxide ring-opening reaction in sols and gels of the system glycidoxypropyltrimethoxysilane-water-titaniumtetraethoxide

Abstract: The examination of hydrolysis, homo- and hetero-condensation reactions, of the condensation degree and the extent of epoxide ring opening in the course of sol-gel process was carried out by means of liquid- and solid-state 29Si and 13C NMR in the system 3-glycidoxypropyltrimethoxysilane (GPTS)-titaniumtetraethoxide-water (molar ratio 1 : 1 : 1.5–14) which is frequently used for the synthesis of heterometal hybrid polymers. The monomeric silanol groups in the GPTS-prehydrolysate immediately co-condense with the Ti-tetraethoxide to Si–O–Ti bonds to an extent of about 50–60% which remain stable in sols and also in the corresponding gels at low amounts of free water (0.02 H2O/OR) in the sol. An increasing amount of free water in the sol (≥0.12 H2O/OR) leads to an increased hydrolytic cleavage of the heterometal bonds and to the formation of homo-condensed polysiloxanes. The condensation degree of RSiO1.5 units in the Ti-containing sols is with 30–60% relatively high in comparison to Ti-free GPTS sols (ca. 5%) whereas the condensation degree of GPTS derived gels (81%) was found to be similar to that of the Ti-containing gels (60–80%). Ti-tetraethoxide accelerates the ring opening reaction of the epoxide group in the sols in dependence on the water content. Up to 78% of the epoxide rings are opened after 24 h in the sol with the highest water content (2 H2O/OR). No epoxide rings can be detected in Ti-containing gels which derive from sols with an amount of free water of ≥0.12 H2O/OR. The results give a first insight into the different parallel reactions in this system and can contribute to more structure controlled syntheses of heterometal hybrid polymers.

Structure design of double-pore silica and its application to hplc

Abstract: Utilizing the concurrence of polymerization-induced phase separation and sol-gel transition in the hydrolytic polycondensation of alkoxysilanes, a well-defined macroporous structure is formed in a monolithic wet gel. By exchanging the fluid phase of the wet gel with an appropriate external solution, the nanometer-range structure of the wet gel can be reorganized into structures with larger median pore size essentially without affecting the macroporous framework. The double-pore structure thus prepared is characterized by open pores distributed in discrete size ranges of micrometers and nanometers. A new type of chromatographic column (silica rod) has been developed using monolithic double-pore silica instead of packed spherical gel particles. Typical silica rod columns had significantly reduced pressure drops and improved analytical efficiencies which do not deteriorate even at higher sample flow rates, both arising from a greater macropore volume than particle packed columns.

Inorganic-Organic Polymers with Barrier Properties for Water Vapor, Oxygen and Flavors

Abstract: With a new kind of barrier coating material, inorganic-organic polymers, it is possible to obtain high-barrier properties with respect to the permeation rates of oxygen, water vapor and volatile organic compounds.

Sol-Gel Science and Technology: Current State and Future Prospects

Abstract: This paper addresses the current state and future prospects of sol-gel processing. It summarizes responses to a questionnaire received from more than four dozen leaders of the sol-gel community. Overall, the respondents remain quite sanguine about the future prospects for the field, and with numerous areas where sol-gel processing can provide unique capabilities and novel materials. The present authors acknowledge this potential, but argue that its achievement will depend upon greatly increased involvement of the sol-gel community with applications, and carrying out a much larger fraction of sol-gel research in the context of applications.

Effects of Poly(ethylene glycol) Doping on the Behavior of Pyrene, Rhodamine 6G, and Acrylodan-Labeled Bovine Serum Albumin Sequestered within Tetramethylorthosilane-Derived Sol-Gel-Processed Composites

Abstract: We investigate the effects of controlled poly(ethylene glycol) (PEG) doping on the behavior of pyrene, rhodamine 6G (R6G), and acrylodan-labeled bovine serum albumin (BSA-Ac) sequestered within tetramethylorthosilicate (TMOS)-derived sol-gel-processed materials. To probe the dipolarity of the local environment within the composite we performed static fluorescence measurements on pyrene as the composites aged. We found that small levels of PEG loading effected significant enhancements in the local dipolarity surrounding the average pyrene molecule. Time-resolved fluorescence anisotropy measurements were used to follow the rotational reorientation dynamics of R6G as the composites aged. As the PEG loading increased, the R6G reorientational mobility increased. Nitrogen adsorption techniques were used to quantify the effects of PEG doping level on the surface area and final xerogel pore features. A large reduction in surface area was observed with PEG doping, but no detectable change in pore size was noted. The effects of PEG doping on a biomolecule were probed by following the time-resolved fluorescence anisotropy decay of BSA-Ac. These results showed that PEG doping resulted in increased biomolecule dynamics relative to that found for a neat, undoped TMOS-derived composites. Together these results show that PEG doping can be used to tune the sol-gel-processed composite dipolarity, alter the mobility of dopants sequestered within the composite, control analyte acessibility to the sensing chemistry, and modulate the internal dynamics within a biodopant.

The Sol-gel process for nano-technologies : new nanocomposites with interesting optical and mechanical properties

Abstract: Various nanocomposite systems have been synthesized by sol-gel routes. For this reason, prefabricated nanoparticles (SiO2 sols or boehmite powder) have been dispersed after surface modification in sol-gel-derived organically modified or polymeric ligand matrices. In all cases, a significant effect on dispersibility by surface modification could be observed. After curing, the mechanical or optical properties depend strongly on the dispersion and surface modification. Using these results, composites to be used in chip coupling and as hard coatings on polycarbonate and CR 39 have been developed.

Sol-Gel Preparation of α-Fe2O3 Thin Films: Structural Characterization by XAFS and Raman

Abstract: Films of Fe2O3 have been prepared by two different sol-gel syntheses, starting from inorganic salts as precursors, Fe(NO3)3 · 9H2O or FeCl3 · 6H2O. Differences in the local order between the two preparations are investigated by XAFS (X-Ray Absorption Fine Structure) and Raman measurements.

Encapsulation of Microbial Cells into Silica Gel

Abstract: This work deals with changes in microbial phenol degradation and cell proliferation caused by immobilization into silica gel. Mixed microbial culture and the yeast Candida tropicalis were immobilized in silica layers and pieces prepared by mixing of prepolymerized tetraethoxysilane with cell suspension. The phenol degradation rate of cells entrapped in silica gel was compared with those immobilized into an organic polymer-polyurethane. The phenol degradation efficiency decreased in the following order: free cell suspension > cells entrapped into polyurethane foam > cells entrapped into prepolymerized TEOS. Inside the silica there was no growth observed by optical microscope. The immobilization of bacterium Pseudomonas species 2 into silica gel, cells which co-metabolize PCBs with biphenyl, did not result in substantial change of intermediate concentration.

Polymerized Complex Route to the Synthesis of Pure SrTiO3 at Reduced Temperatures: Implication for Formation of Sr-Ti Heterometallic Citric Acid Complex

Abstract: Powders of SrTiO3 were prepared by the Pechini-type polymerized complex technique, wherein a mixed solution of citric acid (CA), ethylene glycol (EG), Sr and Ti ions with a molar ratio of CA/EG/Sr/Ti = 10/40/1/1 was polymerized at 130°C to produce a yellowish transparent polyester-type resin without undergoing precipitation, which after decomposition on heating at 350°C was used as a powder precursor for SrTiO3. The formation of pure perovskite SrTiO3 practically free from carbonates occurred when the powder precursor was heat treated at temperatures higher than 500°C in static air. No X-ray diffraction and Raman spectroscopic evidence for phase separation of crystalline SrCO3 and TiO2 as distinct intermediates has been obtained during the thermal decomposition of the powder precursor, suggesting the molecular-scale mixing of cations in the Sr-Ti powder precursor. 13C-NMR spectroscopic measurements have indicated that unusual alkoxylation of CA occurred exclusively when both strontium and titanium ions in equal amounts coexist in CA/EG solutions, the phenomenon of which was discussed in connection with possible formation of a Sr-Ti heterometallic CA complex. The number of CA participating in formation of (Sr, Ti)-CAn was estimated to be n ∼ 3 from the variation of 13C-NMR spectra with relative concentrations of metal ions and CA. This heterometallic complex was thermally stable in CA/EG solutions upon heating at 130°C, implying that the molecular-level homogeneity achieved in the Sr/Ti precursor solution was preserved throughout the polymerization process.

Refractive Microlens Fabrication by Ink-Jet Process

Abstract: Microlenses made of hybrid organic-inorganic materials have been fabricated on glass substrates using a commercial drop-on-demand ink-jet printing system with a 50 μm diameter nozzle driven by a piezoelectric device. After deposition the drops have been polymerized by UV light irradiation. Viscosity, solvent evaporation, drop-substrate wetting condition and drop and substrate temperatures are the main parameters which govern the production of reproducible lens shapes. The shape and surface roughness of the lenses have been characterized by atomic force microscopy and profilometry. Their optical properties have been determined by light microscopy and spectrophotometric techniques. The printing technique can produce plano-convex spherical microlenses with diameters varying from 50 to 300 μm, focal lengths from 70 μm to 3 mm and f-numbers as low as 0.6.

UV Curable Hard Transparent Hybrid Coating Materials on Polycarbonate Prepared by the Sol-Gel Method

Abstract: UV curable, hard, transparent inorganic/organic composites with covalent links between the inorganic and the organic networks were prepared by the sol-gel method. These hybrid coating materials were synthesized using a commercially available, acrylate end-capped polyester or polyurethane oligomeric resin (EBC80, EBC284), hexanedioldiacrylate (HDDA) as a reactive solvent, 3-(trimethoxysilyl)propoxymethacrylate (TMSPM) as a coupling agent between the organic and inorganic phase, and a metal alkoxide, tetraethylorthosilicate (TEOS). The materials were applied on primer or oxygen plasma pretreated polycarbonate sheets and UV cured, followed by a thermal treatment to give a transparent coating with a good adhesion and abrasion resistance. The high transmission and the thermogravimetric behavior indicate the presence of a nanoscale hybrid composite, as is confirmed by SAXS and TEM measurements. In a Taber Abrasion Test, uncoated polycarbonate sheets exhibit a 48% decrease in light transmittance at 600 nm after 300 wear cycles, whereas the EBC80 hybrid coating system containing 9 wt% SiO2 (EBC80/25Si) shows only 28% decrease in light transmittance. A maximal improvement of the abrasion resistance is achieved when 23 wt% SiO2 is incorporated (EBC80/60Si, EBC284/60Si) with only 20% decrease in light transmittance. The abrasion resistance of glass is not yet encountered. For optimal results, it is essential that the rate of condensation of the silanol groups is sufficiently high to form a dense three-dimensional network.

Preparation of Silica Microspheres Containing Ag Nanoparticles

Abstract: Two sol-gel fabrication processes were investigated to make silica spheres containing Ag nanoparticles: (1) a modified Stober method for silica spheres below 1 μm size, and (2) a SiO2-film formation method on spheres of 3–;7 μm size. The spheres were designed to incorporate silver nanoparticles of high χ(3) in a spherical optical cavity structure for the resonance effect. For the incorporation, interaction between [Ag(NH3)2]+ ion and Si-OH was important. In the Stober method, the size of the silica spheres was determined by a charge balance of plus and minus ions on the silica surface. In the film formation method, the capture of Ag complex ion on the silica surface depended on whether the surface was covered with OH groups or not. After doping [Ag(NH3)2]+ into silica particles or SiO2 films on the spheres, these ions w ere reduced by NaBH4 to form silver nanoparticles. From plasma absorption at around 420 nm wavelength and TEM photographs of nanometer-sized silver particles, their formation inside the spherical cavity structures was confirmed.

Sol-gel derived calcium phosphate coatings for biomedical applications

Abstract: Hydroxyapatite (HA) coatings have received considerable attention because they exhibit bone bonding capabilities. Unfortunately the common forms of coating production result in cracking and degradation of HA due to the thickness of the coatings and the elevated temperatures employed. This study demonstrates the production of sub-micron, crack-free calcium phosphate coatings on quartz glass substrates using a sol-gel dip-coating technique and firing temperatures below 1000°C. Coatings fired at 1000°C comprised a mixture of hydroxyapatite (HA) and tricalcium phosphate (TCP). XPS analysis of the coating surface showed that the Ca/P ratio lay in the range 1.5–1.67, and that there was a contribution from carbon in the form of carbonate. It is proposed that the sol-gel coatings comprising a resorbable (TCP) and an insoluble (HA) phase have potential benefits in certain implant applications.

Sol-Gel Physical and Covalent Entrapment of Three Methyl Red Indicators: A Comparative Study

Abstract: We report the results of a comparative study of the properties of three azo dyes from the methyl red indicator family, which were coentrapped with the surfactant cetyltrimethylammonium bromide within tetramethoxysilane-derived silica sol-gel matrices. Characteristic parameters studied were spectral shifts, shifts in indicating ranges and in pKi values, isosbestic-point behavior, changes in the titration curves and stability to leaching. Physical entrapment of methyl red and para-methyl red (pMR) is compared to the covalent entrapment of a trialkoxysilane derivative of methyl red. High stability for leaching was found for all three entrapped indicators. The pKi change in entrapped pMR is interpreted in terms of intracage motion induced by pH changes.

Preparation of Inorganic Oxides via a Non-Hydrolytic Sol-Gel Route

Abstract: Inorganic oxides have been synthesized successfully under mild reaction conditions using a solvent-free non-hydrolytic sol-gel process based on the condensation reaction of “metal” chlorides with oxygen donors such as alkoxides, aldehydes and ethers. Iron(III) chloride was found to be an effective catalyst for the reactions. The order of reactivity of the halides was generally titanium > aluminium > silicon, but in some cases reaction was halted by premature gelation of intermediate species. Silica, alumina and titania were all prepared and characterized by various methods. Calcination studies on the silicas showed these materials to be amorphous up to at least 700°C, but devitrification occurred at 1000°C. Crystallization was studied by X-ray powder diffraction.

Alcoholic Solvent Effect on Silica Synthesis—NMR and DLS Investigation

Abstract: The solvent effect on the synthesis of silica particles has been elucidated through the examination of hydrolysis rate and particle growth by 29Si NMR and Dynamic Light Scattering studies, respectively, in various alcoholic solvents. Kinetic data obtained from the NMR experiments indicate that the rate of hydrolysis is fastest in 1-butanol and the rates follow an unusual order of 1-butanol > methanol > ethanol > 2-propanol > 1-propanol. This order of the rates of hydrolysis is rationalized with two opposing factors, steric hindrance reducing the rate and decrease of hydrogen bonding enhancing the rate. The final particle size increases as the alcohol molecular weight increases. This might be due to decrease in polarity of the alcohols.

Sol-Gel Preparation of Coating Films Containing Noble Metal Colloids

Abstract: Coating films containing Au, Ag, Pt and Pd metal colloids have been prepared by sol-gel processing. It is shown that for oxide films the temperature where the metal particles are precipitated by heating in air depends on metal species: 200°C for Au, 600°C for Ag, 800°C for Pt and 1000°C for Pd. The use of reducing atmosphere lowers the temperature for formation of noble metal colloids. This procedure can be used for direct formation of metal colloids from metal ions in the film as well as reduction of oxide particles to metal particles in the film. For an organic-inorganic matrix, noble metal colloids are precipitated by thermal reduction or photo-reduction. Thermal reduction occurs as a result of reduction by decomposing organic matter. Photo-reduction occurs as a result of UV irradiation.

Preparation of the TiO2 Thin Film Photocatalyst by the Dip-Coating Process

Abstract: Titanium dioxide (TiO2) coated glass-plate thin film photocatalysts for elimination of air pollutants, were prepared by the dip-coating process with titanium alkoxide including polyethylene glycol (PEG) The surface structure of these thin films changed drastically with the size of the PEG They were either transparent or opaque Nitrogen oxides (NOx), one of the most hazardous of air pollutants, were found to be efficiently eliminated by the thin film photocatalyst The photocatalytic activities of the transparent and opaque thin films were found to be almost equal This may be due to the two films having the same surface area The highest activity was obtained for thin films around 1 μm

Ceramic foams from a preceramic polymer and polyurethanes : preparation and morphological investigations

Abstract: Open-cell ceramic foams were obtained from a preceramic polymer (silicone resin) and blown polyurethanes. The preceramic polymer, which is crosslinked by condensation of silanol groups, was dissolved in CH2Cl2 and added to a liquid polyol containing the surfactant and the amine catalyst. Isocyanate was then added to the mixture and the foam was obtained through a twofold blowing mechanism (physical and chemical blowing). The morphology of the expanded polyurethane, which can be flexible or semirigid, characterized the final structure of the ceramic foam. The materials obtained were pyrolyzed in a nitrogen flux at temperatures of 1000–1200°C, thus allowing for the polymer-to-ceramic transformation to occur in the preceramic polymer. The ceramic foams produced in this way consisted of an amorphous silicon oxycarbide ceramic (SiOC). They presented a density ranging from 0.1 to 0.3 g/cm3. The average pore diameter ranged from 200 to 400 μm and they possessed 80 to 90% open porosity.

Photocurable Sol-Gel Coatings: Channel Waveguides for Use at 1.55 μm

Abstract: The development and characterization of channel waveguides using wet-process, low temperature sol-gel chemistry is described. Two structures have been developed. The first one is a one-layer structure, composed of a sol-gel solution which is a mixture of photopolymerizable organosilicate and organozirconate precursors. The other is a multilayer structure with a buffer under the guide and a protective coating. The layers are deposited by the dipping technique. The devices are obtained by UV light exposure of the coating through a predefined mask (channel waveguides). The refractive index increase is sufficient enough to allow the use of waveguides in the 1.55 μm telecommunication window.

All Sol-Gel Electrochromic Devices with Li+ Ionic Conductor, WO3 Electrochromic Films and SnO2 Counter-Electrode Films

Abstract: This paper reports on the development of all sol-gel EC devices, having the configuration WO3/ormolyte/SnO2:Mo, WO3/ormolyte/SnO2:Sb and WO3/ormolyte/SnO2:Sb:Mo, where all three internal layers, including the ionically conductive inorganic-organic hybrid (ormolyte), are prepared via the sol-gel route. The electrochemical and optical properties of EC devices are presented and their cycling stability and reversibility of their optical modulation assessed. The transmission modulation of the devices depends on the thickness of the active electrochromic, counter-electrode and ormolyte layer. The electrochemical and optical properties of individual films and the structural properties of the ormolyte are described and correlated with the stability of the all sol-gel EC devices.

Sol-Gel Processing of Organic-Inorganic Nanocomposite Protective Coatings

Abstract: 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.