49 research outputs found
Scratch Resistant Nanocomposite Coatings on Plastic Substrates by Inorganic-Organic Hybrid Sol-Gel Processing
No full textInorganic-Organic Nanocomposite Based Hard Coatings on Plastics Using In Situ Generated Nano-SiO(2) Bonded with Si-O-Si-PEO Hybrid Network
No full textInorganic-organic hybrid nanocomposite sols were prepared using tetraethyl orthosilicate (TEOS), 3-(glycidoxypropyl)trimethoxysilane (GLYMO), n-butanol, water, methanol, and catalytic amounts of HCl and Al(acac)(3). Hydrolysis-condensation reactions of TEOS at pH approximate to 1.3 generates silica nanoparticles in the sol that remain bonded with the -Si-O-Si- network and protected by the organic functionality of GLYMO. The pH of the final sol was adjusted to close to the isoelectric point of silica (pH similar to 2) to increase the shelf life of the sol. The resulting sol (obtained from the best optimized composition TEOS:GLYMO = 2.33:1) when deposited on CR-39 or related plastics yielded optically transparent and spot-free hard coatings after thermal curing at 95 degrees C. About 1.5-2 mu m thick coatings serve all international specifications required for hard coatings. Thermal curing in the presence of Al(acac)(3) ensured polymerization of GLYMO originated epoxy groups to polyethylene oxide (PEO). BET surface area measurement confirms that the cured coatings are nonporous (surface area 0.6-0.8 m(2) g(-1)) in nature. The density of the coating was measured by the X-ray reflectivity technique (XRR) and found to be 1.70 g cm(-3). TEM shows flaky plastic-like characteristics of the coatings, and small-angle X-ray scattering (SAXS) study reveals the presence SiO(2) nanoparticles of average size 5.4 nm inside the coatings. The pencil hardness value of the coatings (thickness 1.5-2 mu m) was >6H. The high hardness of these nanocomposite coatings is mainly due to the in situ generated silica nanoparticles chemically bonded with the highly cross-linked silica-PEO network
UV curable methacrlate-silica based nanocomposite sol useful for anti-scratch coating and a process thereof
No full textThe present invention provides UV curable "methacrylate-silica" hybrid nanocomposite sol derived from tetraalkoxysilane and methacryloxyalkylalkoxy silanes and acrylate polymerization photoinitiator useful for the deposition of anti-scratch coatings. This invention also provides a process for the preparation of "methacrylate-silica" hybrid nanocomposite sol having longer shelf life and is useful for the deposition of anti-scratch coatings on the substrate like PMMA and other related plastics. Conveyorised UV curing machine was used to cure the coating materials. The high hardness of the cured coatings is due to the generation of glass-like dense silica nanoparticles in situ in the sol which remain bonded with the organic-silica polymer network after UV-curing
Corrigendum to "Inorganic-organic nanocomposite based hard coatings on plastics using in situ generated nano-SiO(2) bonded with Si-O-Si-PEO hybrid network (vol 48, No.9 pp 4326-4333, 2009)"
No full textSuperhydrophobic Films on Glass Surface Derived from Trimethylsilanized Silica Gel Nanoparticles
No full textThe 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 similar to 9.4 nm in the sols. TEM studies showed presence of interconnected SiO(2) NPs of similar to 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 approximate to 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 degrees with 6 mu L of water. These superhydrophobic films were found to be stable up to about 230-240 degrees 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
Synthesis of Au nanoparticle doped SiO(2)-TiO(2) films: tuning of Au surface plasmon band position through controlling the refractive index
No full textThe position of the surface plasmon resonance (SPR) band of Au nanoparticles was tailored by controlling the refractive indices (n) of the embedding matrices, to develop different coloured coatings on glass substrates. Five sets of Au nanoparticle doped coatings were prepared from sols derived from tetraethyl orthosilicate-3-(glycidoxypropyl) trimethoxysilane-titanium tetraethoxide containing gold chloride, following a sol-gel dip-coating method. The film samples of nominal formula (SiO(2))(x)(TiO(2))(0.97-x)Au(0.03)(x = 0.97, 0.679, 0.485, 0.388 and 0.242) were prepared after heat treatment at 500 degrees C in air. The Au SPR peak, in the case of a SiO2 host ( SiO2 : TiO2 5 1 : 0, n = 1.411), observed at 542 nm, gradually red-shifted to 600 nm upon increasing the TiO(2) content (SiO(2) : TiO(2) = 1 : 3, n = 1.939). As a consequence, a systematic change of the Au SPR position yielded pink, magenta, violet, royal and blue coloured coatings on ordinary sheet glasses. The formation of Au nanoparticles in the above gel and glassy coating matrices was monitored by UV-visible and FTIR spectroscopy, X-ray diffraction and transmission electron microscopy
Inorganic−Organic Nanocomposite Based Hard Coatings on Plastics Using In Situ Generated Nano-SiO<sub>2</sub> Bonded with SiO<b></b>SiPEO Hybrid Network
No full textInorganic−organic hybrid nanocomposite sols were prepared using tetraethyl orthosilicate (TEOS), 3-(glycidoxypropyl)trimethoxysilane (GLYMO), n-butanol, water, methanol, and catalytic amounts of HCl and Al(acac)3. Hydrolysis−condensation reactions of TEOS at pH ≈ 1.3 generates silica nanoparticles in the sol that remain bonded with the −Si−O−Si− network and protected by the organic functionality of GLYMO. The pH of the final sol was adjusted to close to the isoelectric point of silica (pH ∼ 2) to increase the shelf life of the sol. The resulting sol (obtained from the best optimized composition TEOS:GLYMO = 2.33:1) when deposited on CR-39 or related plastics yielded optically transparent and spot-free hard coatings after thermal curing at 95 °C. About 1.5−2 μm thick coatings serve all international specifications required for hard coatings. Thermal curing in the presence of Al(acac)3 ensured polymerization of GLYMO originated epoxy groups to polyethylene oxide (PEO). BET surface area measurement confirms that the cured coatings are nonporous (surface area 0.6−0.8 m2 g−1) in nature. The density of the coating was measured by the X-ray reflectivity technique (XRR) and found to be 1.70 g cm−3. TEM shows flaky plastic-like characteristics of the coatings, and small-angle X-ray scattering (SAXS) study reveals the presence SiO2 nanoparticles of average size 5.4 nm inside the coatings. The pencil hardness value of the coatings (thickness 1.5−2 μm) was >6H. The high hardness of these nanocomposite coatings is mainly due to the in situ generated silica nanoparticles chemically bonded with the highly cross-linked silica−PEO network
Refractive Index Controlled Plasmon Tuning of Au Nanoparticles in SiO(2)-ZrO(2) Film Matrices
No full textAu-plasmon tuning has been accomplished by controlling the refractive index (n) of the embedding film matrix. The refractive index of the film matrices were controlled by changing the molar ratios of low (SiO(2)) and high index (ZrO(2)) components following sol-gel reactions. Thus, Au nanoparticles doped films were prepared from SiO(2)-ZrO(2) inorganic-organic hybrid sols of variable molar ratios containing HAuCl(4) following the dip-coating method. The film samples deposited on glass substrates were obtained after drying, UV-treatment, and subsequent heat-treatment at 500 C in air. The nominal mol ratios of SiO(2):ZrO(2) were 1:0, 1:1, 1:2.3, and 1:4. 3 equivalent mol% Au-97% total oxide (SiO(2)+ZrO(2)) was maintained in the final heat-treated films. FTIR studies confirmed good homogeneity of Si-Zr network in the Zr-containing films. The UV-treatment has been introduced to facilitate the decomposition of HAuCl4 in the hybrid matrix prior to the heat-treatment step. The main Au-plasmon peak, in the case of a SiO(2) host (SiO(2):ZrO(2) = 1:0, n = 1.410), observed at about 546 nm, gradually red-shifted to 592 nm upon increasing the ZrO(2) content (SiO(2):ZrO(2) = 1:4, n = 1.847). Transmission electron microscopy of the final heat-treated (500 C) films showed existence of plate-like (triangular and hexagonal) Au nanoparticles (25-50 nm) along with relatively smaller nanoparticles of about 10 nm in size. X-ray diffraction patterns reveal that the Au nanoparticles have a (111) orientation
Photocatalytic Evaluation of Anatase TiO2 Coating on Ceramic Tiles by Raman Spectroscopy
No full textThe present work reports a convenient way to evaluate the photocatalytic activity of anatase TiO2 films by monitoring the degradation of methylene blue (MB) directly on the TiO2 coated tiles under simulated solar light (1 sun condition; AM 1.5G simulator) using Raman spectroscopy. For this purpose, nanocrystalline TiO2 films of aesthetic quality (thickness similar to 80 +/- 5 nm) were deposited by the sol-gel method on the glazed tiles. XRD and Raman studies of the calcined coatings (500 degrees C/2 h in air) confirmed the formation of anatase phase of TiO2. The water contact angle (theta) value of the coated tiles was found to be 20 +/- 1 degrees (hydrophilic) and no significant change of theta was noticed after storing in ambient condition for 3 months. The MB decomposition on the TiO2 coating under 1 sun condition was monitored by recording the Raman spectra with respect to time. Using this technique, the apparent rate constant (k(app)) value of MB degradation was found to be 0.2554 min(-1). The total photo-decomposition of dye and its repeatability studies through direct Raman monitoring of the coating surface ensured the self-cleaning ability of the TiO2 coatings
Superhydrophobic Films on Glass Surface Derived from Trimethylsilanized Silica Gel Nanoparticles
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