Strengthening soda-lime-silica glass by a low-expansion coating applied by melt dipping

A method of strengthening glass by application of a low-expansion glass coating is described. Soda-lime-silica glass rods were dipped vertically into a low-viscosity borate glass melt at 1140 to 1200 °C and rapidly withdrawn. Uniform well-bonded coatings, 100 to 200 m in thickness, were produced. The modulus of rupture (MOR) of unabraded rods coated with a 60 ZnO-40 B₂O₃ (wt%) glass (glass 1) was 548 M Pa, compared with 225 M Pa for a control set of uncoated rods; coated rods after abrasion gave 343 M Pa compared with 110 M Pa for abraded uncoated rods. Rods coated with glass 1 fractured uniformly into small pieces in a manner similar to thermally toughened glass. Approximate calculated axial stresses, using thermal expansion and other data, were 233 M Pa (compressive) in the coating (glass 1) and 56 M Pa (tensile) in the substrate rod. The magnitude of the calculated axial compressive stress in the coating was in good agreement with the increase in average strength of the rods after melt dipping. The results indicate that the fracture origin was probably at the outer coating/air surface and not at the substrate/coating interface, and that the flaw length was less than the coating thickness. Severe flaws on the original rod surfaces were probably filled during melt dipping, rendering them inoperative.     

Crack evolution in Vickers indentation for soda-lime-silica glass

The sequence of radial and median crack formation during Vickers indentations on soda-lime-silica glass with different surface treatments has been investigated. For chemically-toughened soda-lime-silica glass no radial/median cracks were observed around indentations at loads high enough to induce cracks in annealed glasses, even though the thickness of the compressive stress layer was much smaller than the size of the deformed zone. This indicates that embryonic crack initiations at the surface are essential for the development of both median and radial cracks. The crack initiation was discussed from the point of view of the Perrott stress field model and SEM studies.     

Single-step coating of mesoporous silica on cetyltrimethyl ammonium bromide-capped nanoparticles

A generalized, single-step synthesis procedure to coat individual cetyltrimethyl ammonium bromide- (CTAB) capped nanoparticles with a thin layer of mesoporous silica is outlined. This coating method was demonstrated on CTAB-capped Au nanorods and CTAB-transferred CdSe/ZnS quantum dots with silica coatings approximately 15 nm thick containing pores approximately 4 nm in diameter. This porous silica coating can serve as a platform for further surface modification to facilitate the rapid translation of nanoparticles to a wide range of end applications.     

TiO2 coating on silica particles by deposition of sol-gel-derived nanoparticles

TiO₂ was coated on nonporous transparent silica particles of 3.2 μm diameter by deposition of sol-gel-derived TiO₂ nanoparticles. Effects of water concentration, feed rate of titanium tetraisopropoxide (TTIP) solution and amount of supplied TTIP solution on the amount of TiO₂ coated on the silica particles were examined. Scanning electron microscopy observation confirmed that TiO₂ was coated on the silica particles in the form of ‘nanoparticles’ by using this method. Because of that, even though the TiO₂ surface area decreased due to sintering after calcination at high temperature to change the crystalline phase of TiO₂ to the anatase phase, the final surface area was still much larger than that of the original silica particles. The results also showed that as the water concentration increased, the amount of coated TiO₂ decreased. On the other hand, when the amount of supplied TTIP solution increased, the amount of coated TiO₂ increased. It was also confirmed that the feed rate of TTIP solution had little effect on the amount of coated TiO₂. The photocatalytic activities of the resulting TiO₂-coated silica particles were also evaluated by the photocatalytic decomposition of 2,4-dinitrophenol as a model substance. The results showed that the photocatalytic activity of the particles is not a function of the total surface area, but of the surface area in which anatase phase TiO₂ is exposed to the reaction space. The sedimentation velocity of the TiO₂-coated silica particles becomes about 5 orders of magnitude faster than that of the primary particles of the TiO₂. This indicates that the handling of the TiO₂ was also improved considerably by coating on the silica particles.     

Microwave-assisted silica coating and photocatalytic activities of ZnO nanoparticles

A new and rapid method for silica coating of ZnO nanoparticles by the simple microwave irradiation technique is reported. Silica-coated ZnO nanoparticles were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), high-resolution transmission electron microscopy (HR-TEM), CHN elemental analysis and zeta potential measurements. The FT-IR spectra and XPS clearly confirmed the silica coating on ZnO nanoparticles. The results of XPS analysis showed that the elements in the coating at the surface of the ZnO nanoparticles were Zn, O and Si. HR-TEM micrographs revealed a continuous and uniform dense silica coating layer of about 3 nm in thickness on the surface of ZnO nanoparticles. In addition, the silica coating on the ZnO nanoparticles was confirmed by the agreement in the zeta potential of the silica-coated ZnO nanoparticles with that of SiO₂. The results of the photocatalytic degradation of methylene blue (MB) in aqueous solution showed that silica coating effectively reduced the photocatalytic activity of ZnO nanoparticles. Silica-coated ZnO nanoparticles showed excellent UV shielding ability and visible light transparency.     

Superhydrophobic films on glass surface derived from trimethylsilanized silica gel nanoparticles

The paper deals with the fabrication of sol-gel-derived superhydrophobic films on glass based on the macroscopic silica network with surface modification. The fabricated transparent films were composed of a hybrid -Si(CH(3))(3)-functionalized SiO(2) nanospheres exhibiting the desired micro/nanostructure, water repellency, and antireflection (AR) property. The wavelength selective AR property can be tuned by controlling the physical thickness of the films. Small-angle X-ray scattering (SAXS) studies revealed the existence of SiO(2) nanoparticles of average size ～9.4 nm in the sols. TEM studies showed presence of interconnected SiO(2) NPs of ～10 nm in size. The films were formed with uniformly packed SiO(2) aggregates as observed by FESEM of film surface. FTIR of the films confirmed presence of glasslike Si-O-Si bonding and methyl functionalization. The hydrophobicity of the surface was depended on the thickness of the deposited films. A critical film thickness (>115 nm) was necessary to obtain the air push effect for superhydrophobicity. Trimethylsilyl functionalization of SiO(2) and the surface roughness (rms ≈30 nm as observed by AFM) of the films were also contributed toward the high water contact angle (WCA). The coated glass surface showed WCA value of the droplet as high as 168 ± 3° with 6 μL of water. These superhydrophobic films were found to be stable up to about 230-240 °C as confirmed by TG/DTA studies, and WCA measurements of the films with respect to the heat-treatment temperatures. These high water repellant films can be deposited on relatively large glass surfaces to remove water droplets immediately without any mechanical assistance.     

High-aperture optical waveguides based on fluorine-doped silica glass

The dependence of fluorine incorporation into silica glass on conditions of the optical waveguide blank manufacture using the method of modified chemical vapor deposition (MCVD) is studied. The degree of fluorine incorporation at constant consumption of a fluoridizer (SiF₄) is shown to increase with an increase in the volume of deposited material. Samples of multimode optical waveguides with a core from pure silica glass and a reflective coating made of fluorine-doped silica glass with a numerical aperture of ∼0.18 are obtained. Optical losses in such optical waveguides reach 0.5 dB/km in the long-wavelength region of the spectrum. Original Russian Text ? A.N. Guryanov, M.Yu. Salganskii, V.F. Khopin, A.F. Kosolapov, S.L. Semenov, 2009, published in Neorganicheskie Materialy, 2009, Vol. 45, No. 7, pp. 887–891.     

Strengthening and toughening of soda-lime glass by a reinforced coating

The strength and toughness of soda-lime (container) glass have been enhanced by factors of 2 and 40, respectively, by a 0.1 mm coating of polyurethane containing 6–9 wt% silicon carbide whiskers in random orientation. The strength measurements were made using a standardized procedure and a biaxial ring-on-ring flexure rig. The toughness enhancement has been shown to be due to crack-branching and fibre pull-out mechanisms in the coating, which bridges any strength-limiting flaws in the underlying glass.     

Superhydrophobic surfaces on cotton textiles by complex coating of silica nanoparticles and hydrophobization

By the complex coating of amino- and epoxy-functionalized silica nanoparticles on epoxy-functionalized cotton textiles to generate a dual-size surface roughness, followed by hydrophobization with stearic acid, 1H,1H,2H,2H-perfluorodecyltrichlorosilane, or their combination, superhydrophobic surfaces were prepared. The static water contact angle of the most superhydrophobic sample as prepared reaches 170° for a 5 μL droplet. The wettability and morphology were investigated by contact angle measurement and scanning electron microscopy. Characterizations by Fourier transformation infrared spectroscopy, and thermal gravimetric analysis were also conducted.     

Solar control coating on glass

One of the various solar control glasses, a silver-based multilayer film formed by sputtering is becoming increasingly important because of its excellent and versatile performance. Recently major progress has been made in the sputtering process by several manufacturers, which has enabled both a stable and high rate of deposition. Efforts to improve the durability of sputter coating have been maintained seeking a flexible production process and expanded applications.     

Titanium-base coating on plane silica substrates

Plane silica substrates were coated with a titanium-based deposit by gaseous cementation at temperatures ranging from 600 to 800 ° C, over 1 h to several tens of hours. The cement consisted of hydrogen chloride and titanium. The bilayer structure of the coating was established by X-ray diffraction, X-ray electron microprobe analysis, scanning electron microscopy, low-energy electron-induced X-ray spectroscopy. X-ray photoelectron spectroscopy, optical microscopy and X-ray fluorescence spectroscopy. Thin coatings were amorphous and the composition of the outer zone was close to TiO. Thicker coatings ranging from 2 to 30 m were crystalline. In this case, the outer layer, designated -Ti(O) or TiO _x with 0.44 × 0.49, corresponded to an ordered solid solution of oxygen in a close-packed hexagonal titanium. The inner layer in contact with the substrate was Ti₅Si₃. At fixed temperatures (600, 650, 700, and 800 ° C), the thickness of the coating increased according to a parabolic law. Activation energy and diffusion coefficient were calculated. Thermodynamic considerations concerning the interactions between the gaseous phase of cementation and the silica substrate, are presented from theoretical calculations and from Ti-Si-O phase diagrams experimentally constructed at 800, 1000 and 1300 ° C.     

Dual-luminophore-doped silica nanoparticles for multiplexed signaling

We have synthesized dual-luminophore-doped silica nanoparticles for multiplexed signaling in bioanalysis. Two luminophores, Tris(2,2'-bipyridyl)osmium(II)bis(hexafluorophosphate) (OsBpy) and Tris(2,2'-bipyridyl)dichlororuthenium(II)hexahydrate (RuBpy), were simultaneously entrapped inside silica nanoparticles at precisely controlled ratios, with desirable sizes and required surface functionality. Single-wavelength excitation with dual emission endows the nanoparticles with optical encoding capability for rapid and high-throughput multiplexed detection. The nanoparticles can be prepared with sizes ranging from a few nanometers to a few hundred nanometers, with specific ratios of luminescence intensities at two well-resolved wavelengths and with excellent reproducibility. These nanoparticles also possess unique properties of high signal amplification, excellent photostability, and easy surface bioconjugation for highly sensitive measurements when used as signaling markers. A simplified ligand binding system using avidin-biotin and an application extension to immunoassays have been explored, demonstrating the potential use of these easily obtainable bioconjugated nanoparticles for multiplexed signaling and bioassays.     

Antireflective coating for ITO films deposited on glass substrate

The refractive index n of radio-frequency (r.f.) magnetron sputtered indium tin oxide (ITO) films varies with sputtering parameters, such as sputtering power and oxygen percentage in the sputtering ambient. In this study, the feasibility to fabricate multilayer antireflective (AR) coating with a single ITO target by controlling the sputtering conditions is explored. Reduction in the reflectance can be achieved by using a one-quarter-wavelength inner layer ITO with a refractive index n = 1.87 and a one-quarter-wavelength outer layer ITO with n = 2.17. Hence, a single ITO target suffices in the preparation of multilayer AR coating. This simplifies the deposition processes and equipment for the fabrication of AR coating. Surface corrugation, another approach to the reduction of reflectance, is also discussed.     

Fluorescent detection of ATP based on signaling DNA aptamer attached silica nanoparticles

Novel methods for rapid, sensitive and low-cost biomolecule detection have attracted particular interest because of their wide use in medical diagnostics, food inspection and biomedical research applications. In this work, we report a simple and efficient silica nanoparticle (NP)-based fluorescent assay for ATP detection. It takes advantage of the washing and separation properties of NPs and the structure-switch property of DNA aptamers, resulting in fluorescence change of the supernatant in the presence of targets. A linear response for ATP detection was observed from 0 to 6?mM with a detection limit of ～34?μM. This detection strategy could be generalized to other aptamer-based detection systems.