Characterization of oxide coatings on glass

Some representative characteristics of oxide films deposited on glass by different techniques have been briefly described as well as several relevant methods of thin-film analysis to determine these quantities. The most powerful information obtained by some analytical techniques have been given, and some typical problems that may occur during the analysis of oxidic thin films have been discussed. With a few selected results, the potential of some modern methods has been demonstrated.     

Indium doped zinc oxide nanopowders for transparent conducting coatings on glass substrates

Crystalline indium doped zinc oxide (IZO) nanopowders were synthesized using hydrothermal treatment processing. Increasing the doping ratio of indium in the zinc oxide significantly influences the phase structure and shape of the nanopowders resulting in nanorod to nanoparticulate morphologies. As the doping profile increases, the crystallite size decreases, the band gap energy blue shifts and the specific surface area increases (measured by BET method). Additionally Raman spectroscopy exhibited shifts of several peaks, as well as revealed new peaks, confirming the substitution of indium ions within the zinc oxide lattice sites. An IZO suspension made of IZO nanoparticles (In/Zn = 3 atm.%) with a zeta potential greater than 30 mV at pH = 6 was successfully spin-coated on glass substrates for to make transparent conductive coatings evincing sheet resistances as low as 35 kΩ_□ (ρ = 4.9 × 10^?3 Ω m,) with transmission in the visible range as high as 90 %.     

Biofouling studies on nanoparticle-based metal oxide coatings on glass coupons exposed to marine environment

Titania, niobia and silica coatings, derived from their respective nanoparticle dispersions or sols and fabricated on soda lime glass substrates were subjected to field testing in marine environment for antimacrofouling applications for marine optical instruments. Settlement and enumeration of macrofouling organisms like barnacles, hydroides and oysters on these nanoparticle-based metal oxide coatings subjected to different heat treatments up to 400 °C were periodically monitored for a period of 15 days. The differences observed in the antifouling behaviour between the coated and uncoated substrates are discussed based on the solar ultraviolet light induced photocatalytic activities as well as hydrophilicities of the coatings in case of titania and niobia coatings and the inherent hydrophilicity in the case of silica coating. The effect of heat treatment on the photocatalytic activity of the coatings is also discussed.     

Characterization of electrically conductive vanadate glass containing tungsten oxide

New conductive glass with a composition of 20BaO·10Fe₂O₃·xWO₃·(70 ? x)V₂O₅ (x = 10–50) was investigated by means of Mössbauer spectroscopy. A marked decrease in quadrupole splitting (Δ) was observed after the isothermal annealing at 500 °C for 1,000 min, due to the structural relaxation of 3D-network composed of FeO₄, VO₄, and VO₅ units. After the isothermal annealing, a marked increase in the electrical conductivity (σ) was observed from 1.7 × 10^?5 to 1.0 × 10^?1 S cm^?1 when “x” was 10, whereas comparable σ values of 1.1 × 10^?4 and 2.0 × 10^?4 S cm^?1 were observed when “x” was 40. These results evidently show that structural relaxation of 3D-network structure involved with a marked increase in σ is intrinsic of “vanadate glass”. XRD pattern indicated several weak peaks due to needle-like BaFe₂O₄ and α-Fe₂O₃ when the glass sample with “x” of 20 was annealed at 500 °C for 1,000 min. SEM study proved the formation of needle-like BaFe₂O₄ just on the surface of the sample, whereas hexagonal BaFe₁₂O₁₉ were observed in the annealed sample with “x” of 40. Chemical durability of WO₃-containing vanadate glass was investigated by immersing each glass sample into 20 %-HCl solution for 72 h.     

Characterization of oxide scales on coatings for gas turbine blades by infrared reflection-absorption spectroscopy

The oxidation of chromia (Cr₂O₃) and alumina (Al₂O₃) forming alloys for the protection of gas turbine blades has been studied by Infrared Reflection Absorption Spectroscopy (IRAS). The Berreman-Effect (i. e. minimum of reflectivity of p-polarized light at oblique incidence) allows an unambiguous distinction between Al₂O₃ and Cr₂O₃ for thin scales (<0.1 m) as well as for thick scales (6 m). The position of interference fringes in the non-absorbing region of the spectrum results in simultaneous thickness determinations.     

Functional coatings on glass using ORMOCER®-systems

Sol-gel derived ORMOCER^® materials (organically modified ceramics) have been developed for the functionalization of glass. The adjusted coating systems can be applied in optical quality by conventional paint technologies. Good long-term adhesion, scratch and abrasion resistance, stability against weathering and resistance towards corrosive delamination are additional outstanding advantages of such coating systems. The ORMOCER^® coatings can also carry additional functions. For example, the surface polarity of glass can be modified. Hydrophilic as well as extremely hydrophobic surfaces can be attained. The contact angles measured with water range between 10° and 110°. Furthermore, colouring of glass articles is possible with coatings containing chromophores.     

Physicochemical characterization of biological glass coatings

Metallic implants are widely used in orthopaedic surgery but metal release has been reported by several authors. High metallic ion concentration in surrounding tissues may play a major role in therapeutic failure. We have investigated in vivo and in vitro two biological glasses (BVA and BVH) used as coatings of metal implants. Physicochemical characterization was made by several complementary methods, particularly particle induced x‐ray emission (PIXE) and energy‐dispersive x‐ray spectroscopy (EDXS) associated with electronic microscopy. Analyses clearly show the differences of behaviour between both glasses. The BVA glass is bioactive, i.e. it develops a direct chemical bond between prosthesis and bone by the formation of a calcium phosphate layer at its surface. These structural and compositional modifications are caused by hydrolysis of the glass. After its dissolution BVA glass is replaced by bone, which ensures better integration of the implant in the bone site. The BVH glass is not bioactive and is used as a cement to isolate the metal implant from the biological environment, but the coating disaggregates with implantation time and glass grains migrate through the bony lacuna network. Copyright © 2003 John Wiley & Sons, Ltd.     

Electrochemical formation of cerium-containing oxide coatings on titanium

Possibility and conditions of obtaining cerium-containing oxide coatings on titanium alloys by microarc oxidation in electrolytes with tartrate and citrate cerium complexes were determined. The effect of organic cerium complexes on the kinetic parameters of the microarc oxidation of titanium alloys was studied. Porous oxides coatings containing up to 20% cerium were obtained.     

Continuous silica coatings on glass fibers via bioinspired approaches

Simple methods for producing continuous inorganic coatings on fibers have application in multiple technologies. The application of bioinspired strategies for the formation of particulate inorganic materials has been widely investigated and provides routes to inorganic materials under environmentally benign conditions. In this work, we describe the formation of stable and continuous inorganic coatings on glass fibers via the polymerization of silica in the presence of biopolymers. The formation of both organic and inorganic coatings was investigated via X-ray photoelectron spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray analysis. The simple route to silica coatings presented herein could be interesting for the development of functional hybrid fibrous materials suitable for catalytic and sensor applications, given the homogeneous nature of the silica films and the benign conditions employed for film formation.     

Corrosion and electrochemical behavior of water glass coatings embedded with graphite/titanium oxide on 2A12 aluminum alloy

Journal of Solid State Electrochemistry - Graphite/titanium oxide composite anti-corrosion coatings with five proportions of graphite were applied on the surface of aluminum alloy. The surface...     

Problems with the analysis of glass and glass ceramic surfaces and coatings

Summary The investigation of the composition of the surfaces and the spatial distributions of elements and phases within subsurface layers on glasses, coatings and interfacial layers is a most important, necessary requirement to understand and to control chemical interactions between glass and glass ceramic surfaces and adjacent materials. In general, this necessary requirement can be met only by using simultaneously a couple of surface analysis methods and the analytical electron microscopy. The application of single analysis methods can be sufficient, however, if basic results are available on the physics and chemistry of glasses to complement them in order to obtain the necessary information.Data are scarce on the free enthalpies of formation for non-crystalline materials, and, therefore, data on the free enthalpies of reaction cannot be calculated for the reactions with adjacent materials. Therefore, it is important to apply and to further develop methods to obtain data on the structures and microstructures of the crystalline and non-crystalline subsurface layer and coating materials, too. These data allow correlation of the differences in these structures with differences of the driving forces of the surface material reactions observed with adjacent phases and their reaction kinetics for the non-crystalline materials, too. Problems also arise with regard to the application of surface analysis methods, because changes of the spatial element distributions can be induced by a transfer of charge and energy to the surface during analysis. Furthermore, surface analysis methods must be improved to allow in-situ analysis.

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Analytische Probleme zu Glas- und Glaskeramik-Oberflächen und -Beschichtungen

     

Ta-containing oxide coatings on titanium for biomedical application

Bioinert, biocompatible, chemical-resistant oxide coatings containing Ta₂O₅, which are promising to be applied to titanium implants, were produced on titanium by plasma electrolytic oxidation in an aqueous electrolyte. An effect of formation conditions on the elemental and phase composition, thickness, and roughness of the coatings was researched. It was found that an addition of polyethylene glycol to electrolyte without affecting the elemental composition and the thickness causes a change in the porosity and an increase in the roughness of the formed oxide layer. Changing the surface arrangement may allow affecting an adhesion of biotissues to titanium implants with coatings and accumulating drugs by the coatings.     

Characterization of SiO2 protective coatings on polycarbonate

SiO₂ protective coatings have been deposited on polycarbonate substrates by plasma ion assisted deposition. The influence of ion energy on the water permeability and the surface topography of the coatings was studied by infrared spectroscopy and atomic force microscopy. Coatings deposited at sufficiently high ion energies show a barrier effect against moisture uptake and considerably reduced film roughness. Both effects are attributed to an increase of the packing densities of the coatings.     

Catalytic properties of complex oxide coatings on foamed nickel

Effect of the Ni/NiO composite support on the properties of catalytic systems based on cerium oxide and lanthanum manganite with various dopants was studied.     

The impact of Mn oxide coatings on Zn distribution

Zinc sorption to hydrous manganese oxide (HMO)-coated clay was investigated macroscopically, kinetically, and spectroscopically. Adsorption edges and isotherms revealed that the affinity and capacity of the HMO-coated montmorillonite was greater than that of montmorillonite, and when normalized to the oxide present, the coatings behaved similarly to the discrete Mn oxide. Over two pH conditions, 5 and 6, a linear relationship was observed for the isotherms; further analysis with X-ray absorption spectroscopy (XAS) resulted in one type of sorption configuration as a function of loading and ionic strength at pH 5. However, at a surface loading of 10(-3) mol(Zn) g(HMO-coatedclay)(-1) when the pH increased from 5 to 7, the first shell distance decreased slightly, while the atoms and coordination numbers remained the same; this change may be attributed to an increase in electrostatic interactions. After a contact time of 4 months where an additional 60% of the sites become occupied, the slower sorption process was modeled as intraparticle surface diffusion. Best fit diffusivities ranged from 10(-18) to 10(-17) cm2/s, where a slower process was observed for the coated surface as compared to the discrete oxide. Interestingly, the porosity of the Mn oxide coating appears to be influenced by the substrate during its growth, as its increase and shift to a smaller pore size distribution resulted in a diffusivity between that observed for discrete HMO and montmorillonite.     

Deposition of antireflection coatings onto silicate glass from a silicon dioxide sol containing a nonionogenic surfactant and oligoester based on propylene oxide

Possibility of obtaining low-refractive-index antireflection coatings composed of mesoporous silicon dioxide by simultaneous introduction of two organic compounds, oligoester based on propylene oxide and a nonionogenic surfactant, into a silicon dioxide sol was studied.     

Ion-beam-induced reduction of iron oxide supported on porous glass

When ferric oxide supported on porous glass was irradiated by 40 keV He⁺ ions, the reduction of Fe³⁺ to Fe²⁺ species occurred. The yield of Fe²⁺ species, which was monitored by the Mössbauer spectroscopic measurement, increased with increasing total dose, and went up to ca. 80%. This unexpectedly large yield meant that the effect was exerted beyond the range of the incident He⁺ ions. Clear dose rate dependence of the Fe²⁺ yield was also observed. We examined the possibility that the reduction of the Fe³⁺ species was caused by some type of gaseous reductant produced by radiolysis of surface chemical species such as physisorbed water molecules and surface hydroxyls.     

Surface analysis of sol-gel coatings on glass by secondary neutral mass spectrometry

Secondary neutral mass spectrometry (SNMS) has been used to profile coatings of the systems SiO₂ and 65SiO₂.20TiO₂.15ZrO₂ (STZ). The coatings have been deposited on float glass and heat insulating glass by dip coating from alkoxide solutions. The microporous gel coatings have been densified by heat treatment. The SBM method (separate bombardment mode) has been applied to characterize the systems and the HFM method (high frequency mode) to check for matrix effects in the SBM depth profiles. Both methods show sodium diffusion from the float glass substrate into the STZ coating and no significant sodium diffusion into the SiO₂ coating. Measurements of the coatings on the heat insulating glass indicate that the SnO₂ interlayer acts as a diffusion barrier. The diffusion of sodium from the float glass substrate into the STZ coating during consolidation has been analyzed by SBM-SNMS. The sputtering rate decreases with increasing consolidation. Due to large differences between sputtering rates of the substrate and of the microporous coatings, the calibration of sodium intensities from time to depth at the interface has not been possible. However, a correlation between the final temperature of heat treatment and the depth of the Na₂O depletion in the substrate surface under the coating can be obtained.