Durable superhydrophobic ZnO-SiO2 films: a new approach to enhance the abrasion resistant property of trimethylsilyl functionalized SiO2 nanoparticles on glass

Although trimethylsilyl functionalized SiO2 derived films show excellent superhydrophobicity, their adhesion and abrasion resistant properties are extremely poor. In this study, a new approach has been shown to improve the adhesion and abrasion properties of such films. A neutral and relatively hydrophobic Zn(CH3OO)(2)(H2O)(2)] complex solution has been used to interact with the superhydrophobic silica gel nanoparticle dispersion. After dip-coating, the composite sol yielded films of a zinc acetate/superhydrophobic silica composite network while the hydrophilic part (bonded water) associated with Zn helps in binding the hydroxyl groups (silanols) present on the glass surface. The composite films were heat-treated at 300-400 degrees C in a nitrogen atmosphere in order to obtain transparent and superhydrophobic ZnO-SiO2 nanocomposite films. The decomposition of zinc acetate formed ZnO nanocrystallites and remained attached with the hybrid silica matrix. These films showed excellent water repellency (water contact angle, CA approximate to 158 +/- 7 degrees; hysteresis approximate to 4 degrees) with good adhesion and abrasion resistant properties. XRD, Raman and TEM studies confirm the existence of ZnO nanocrystallites in the composite films. Owing to the stability of hydrophobic methyl groups attached with silicon at relatively high temperature in a nitrogen atmosphere, these ZnO-SiO2 nanocomposite films remain superhydrophobic even after a heat-treatment at 400 degrees C

Fabrication of Germanium-on-insulator in a Ge wafer with a crystalline Ge top layer and buried GeO2 layer by Oxygen ion implantation

The paper reports fabrication of Germanium-on-Insulator (GeOI) wafer by Oxygen ion implantation of an undoped single crystalline Ge wafer of orientation (100). Oxygen ions of energy 200 keV were implanted. The implanted wafer was subjected to Rapid Thermal Annealing to 650 C. The resulting wafer has a top crystalline Ge layer of 220 nm thickness and Buried Oxide layer (BOX) layer of good quality crystalline Germanium oxide with thickness around 0.62 micron. The crystalline BOX layer has hexagonal crystal structure with lattice constants close to the standard values. Raman Spectroscopy, cross-sectional HRTEM with SAED and EDS established that the top Ge layer was recrystallized during annealing with faceted crystallites. The top layer has a small tensile strain of around +0.4\% and has estimated dislocation density of 2.7 x 10^{7}cm^{-2}. The thickness, crystallinity and electrical characteristics of the top layer and the quality of the BOX layer of GeO_{2} are such that it can be utilized for device fabrication

Inorganic-Organic Nanocomposite Based Hard Coatings on Plastics Using In Situ Generated Nano-SiO(2) Bonded with Si-O-Si-PEO Hybrid Network

Inorganic-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

The 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

Tuning of Ag-SPR band position in refractive index controlled inorganic-organic hybrid SiO(2)-PEO-TiO(2) films

Inorganic (silica-titania)-organic (polyethylene oxide) hybrid films with variable refractive index (RI) values were synthesized and Ag nanoparticles were generated in situ inside such hybrid films to develop coloured coatings specially on plastic substrates. The hybrid films and the corresponding Ag-incorporated films were prepared from sols derived from a mixture of silicon tetraethoxide (STE), 3-(glycidoxypropyl)trimethoxysilane (GPTMS), titanium tetraisopropoxide (TTIP) and silver nitrate following a sol-gel dip-coating method and cured at low temperature (90A degrees C), followed by UV treatment with an energy equivalent to 5 center dot 3 +/- 0 center dot 1 J cm(-2). The equivalent SiO(2): SiO(1 center dot 5)(CH(2))(3)OCH(2)CH(CH(2))O: TiO(2): Ag molar ratios (nominal) of the final cured films are varied in the ranges (67 center dot 9-0): 29 center dot 1: (0-67 center dot 9): 3. The refractive index values of the cured hybrid films were found to be increased systematically from 1 center dot 475 to 1 center dot 710 with increasing Ti-component. The Ag-SPR peak, in case of silica-polyethylene oxide host (RI = 1 center dot 475), observed at 419 nm, gradually red-shifted to 497 nm upon increasing the Ti-component (equivalent TiO(2) content 67 center dot 9 mol%; RI = 1 center dot 710) of the film. As a consequence, a systematic change of Ag-SPR position yielded yellow, yellowish-orange, orange, brownish-orange and orangish-brown coloured coatings

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 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

Refractive Index Controlled Plasmon Tuning of Au Nanoparticles in SiO(2)-ZrO(2) Film Matrices

Au-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

Inorganic-organic hybrid coatings on polycarbonate. Spectroscopic studies on the simultaneous polymerizations of methacrylate and silica networks

Hybrid methacrylate-silica coatings derived from 3-(methacryloxypropyl)-trimethoxy silane were deposited on polycarbonate via hydrolysis-condensation reactions followed by UV curing (lambda = 253.7 nm). The formation of -Si-O-Si- (inorganic backbone) and polymethacrylate (organic) networks leading to the generation of hybrid structure was monitored by UV and Fourier transform infrared (FTIR) spectroscopies. UV and FTIR spectra showed complete polymerization of methacrylate groups during UV curing of the coatings. The silica network was initially formed through the hydrolysis-condensation reactions of alkoxy groups in the sol as evident from the appearance of FTIR peaks due to -Si-O-Si- vibrations. Further silanol (Si-OH) condensation reactions leading to the generation of more silica network were occurred simultaneously with methacrylate polymerization during UV photo curing of the coating. (C) 2002 Elsevier Science B.V. All rights reserved