Silica sol-gel coatings

H.G. Floch, J.J. Priotton I.M. Thomas, "Porous Silica Sol-Gel Coatings For Nd Glass High-Pbwer Pulsed Laser Uses", The Hiysics Technology of Amorphous Si02, edited by R. Devine, Plenum Press, 1988. 

Maggio RD, Campostrini R, Carturan G. Ageing of silica sol-gel coatings on glass sheets studied by Vickers crack nucleation. J Mater Sci Lett 1995 14 1591-3. 

Li and Ba (2008) prepared silica sol-gel coating of aluminum for corrosion protection using triethoxysilane (TES) as a precursor and characterized the materials using spectroscopic (NMR, FTIR, and Raman) and other methods. Electrochemical data have shown that the sol-gel coating significantly improves the corrosion protection properties of aluminum. The Si NMR spectra of... 

Figure 26-6. Representative AFM (height) images and diagonal cross-sectional profiles for (a) acid-catalyzed, and (b) base-catalyzed silica sol/gel coatings. Both height images are 500 nm x 500 nm, with a z-range of 10 nm. The RMS surface roughness values are 3 and 14 A for (a) and (b), respectively.

Pepe A., Aparicio M., Cere S., Duran A. (2004), Preparation and characterization of cerium doped silica sol-gel coatings on glass and aluminum substrates, J. Non-Cryst Solids, 348 162-171. 

Taylor and Fabes compared the chemophysical properties of silica sol-gel coatings after irradiation with CO2 and Nd YAG lasers with those of furnace-fired samples [67]. The laser-fired films showed a steady increase in the refractive index throughout most part of the densification process, whereas the... 

American scientists prepared the organo-silica sol-gel membranes60 and demonstrated in a single layer format for pH measurement and multiple-layer format for both C02 and NH3. The sensors used a hydroxypyrenetrisulfonic acid (HPTS) as the indicator immobilizes in a base-catalyzed sol-gel containing poly(dimethyl)siloxane, aminopropyl-triethoxysilane (APTES) and tetraethylorthosilicate (TEOS). This indicator gel was over coated with a hydrophobic sol-gel to reduce cross reactivity to pH when either carbon dioxide or ammonia were examined. 

A thin film dissolved oxygen sensor was fabricated by entrapping erythrosin B in a sol-gel matrix95. The silica sol-gel doped with the dye was deposited onto the cleaned glass slides by the spin-coating method. The sensor was linear in the most useful range of dissolved oxygen concentrations, up to 9.1 mg l 1 concentration obtained in air saturated water at 20 °C. 

With careful selection of the combination of starting alkoxides and appropriate synthesis conditions, silica-based sol-gel technology is now widely applied to the conservation of art objects and cultural heritage. For example, a hybrid sol-gel coating protects the fourteenth-century... 

Antireflective (AR) coatings are required on optics to reduce the reflective surface losses. Vitreous silica coatings in the form of porous or multilayer films are used extensively in this application. Antireflective coatings have been developed which employ colloidal fused silica sol—gel particles made from organometallic materials (253). 

Sol-gel coatings -silica gels as [SILICA - AMORPHOUS SILICA] (Vol 21)... 

Ascorbic acid Mediated oxidation at a silica sol-gel glass coated ferricyanide-doped Tosflex-modified SPCE FIA +0.3 V 46 nM to 300 nM 46 nM Zen et al. [66]... 

A common and well-known method to prepare silica membranes with molecular sieving properties is sol-gel coating [3-5], With this technique, microporous silica layers with a pore-size of about 0.5 nm are dip-coated on top of supported y-alumina membranes. The supports are porous a-alumina disks with pore diameters in the range from 100-200 nm. On top of these macroporous supports a 3 pm thick mesoporous y-alumina layer is coated, with a pore size of 3 nm. 

A sol-gel coating procedure for silica on metallic monoliths was developed by Zwinkels et al. (74), who used colloidal silica sols together with potassium waterglass. Various procedures resulted in washcoats 20-50 pm thick, with surface areas of 60-140 m /g. Coating with the colloidal silica without binder material resulted in a thickness of only a few micrometers. 

The term controlled index means that the refractive index can be made smaller than that of the bulk precursor by controlling the microstructure via the porosity. When silica is deposited, for example, the film index n can be varied over a wide range (7) from n = 1.1 to 1.5. This process control makes sol-gel coatings interesting for many optical, electronic, and sensor applications, but the evolution of the microstructure during film formation is not well understood, in spite of efforts to survey the variables (8, 9). This chapter reviews the important factors determining the microstructure of dip-coated films and explores at length two of them, evaporation and surface tension. 

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