Increasing Silica Content Research Articles

Formation and function mechanisms of nanostructured tribofilms of epoxy-based hybrid nanocomposites

The nanostructures and properties of the tribofilms of epoxy (EP) composites filled with short carbon fibers (SCF) and different volume fractions of monodisperse silica nanoparticles were investigated. When the conventional composite filled only with SCF was considered under a high pv condition, an iron oxide layer is formed on the steel counterface. The addition of even only 0.05vol% nano-silica leads to a significant change of the tribofilm’s structure and the tribological behavior of the composite. With increasing silica content, the oxidation layer on the steel surface is gradually replaced by a silica-based tribofilm. A close relationship between the tribofilms’ structure and the tribological behavior of the composites was identified. Mixing, possible reactions and tribo-sintering of silica nanoparticles with other wear products are deemed to be main mechanisms inducing the formation and the lubricity of the silica-based tribofilm.

Ultrafine nanocrystalline mesoporous NaY zeolites from fly ash and their suitability for eco-friendly corrosion protection

Fly ash, an industrial waste from coal based thermal power stations and a vast resource for silica and alumina, remains underutilized. It consists of polycyclic aromatic hydrocarbons, metals, silica etc. which are toxic in nature and silica has also been classified as a carcinogenic material. So a definite need is to make a proper use of the fly ash in order to convert it into useful materials possessing enormous functionality. Preparation of uniform nanocrystalline mesoporous NaY zeolites from fly ash without use of organic structural directing agents is reported for the first time. Different ratios of fumed silica are added to fly ash for preparation of NaY zeolites. The effect of amount of water used during the crystallization process on particle size of the zeolite is reported. Detailed characterization of the prepared zeolites is carried out using XRD, FTIR, SEM EDAX and DLS. Si/Al ratio was calculated using NMR and EDAX data. Porosity, pore size distribution and pore volume were determined using nitrogen adsorption data. The particle size of zeolites was found to be in the range of 400–670 nm whereas the crystallite size calculated from the XRD data was in 9–13.4 nm range. The synthesized zeolites are found to possess high crystallinity (90–93 %). Formation of octahedral crystals is confirmed by SEM observations. BET analysis shows high surface areas and presence of mesopores. IR and NMR spectroscopy confirms the formation of NaY with increased silica content. The prepared zeolites exhibited good ion exchange capacities which were found to decrease with increase in Si/Al ratio. Unlike the common applications of zeolites in catalysis where high purity is desirable, the fly ash based zeolites were exchanged with zinc metal ion and applied as pigment in anticorrosive paint formulations. Corrosion resistance was evaluated using electrochemical impedance spectroscopy measurements. The results indicate that metal exchanged zeolite possesses good anticorrosive property and can be used as an alternate to the conventionally used toxic, lead and chromate based anticorrosive pigments.

Chitosan–silica composite aerogels: preparation, characterization and Congo red adsorption

A series of aerogels composed of chitosan and/or silica were fabricated by tuning their feeding ratios. They were characterized by FTIR, thermogravimetric analysis, and X-ray diffraction; pore structures were analyzed by Brunauer–Emmett–Teller (BET) nitrogen sorption and scanning electron microscopy (SEM); adsorption capacities to Congo red were explored as well. The incorporation of silica enhances the thermostabilization of chitosan in gels. And as silica content increases, bulk densities of aerogels decrease gradually, while porosities, pore volumes, and surface areas obtained via BET method increase consequently; as well, porous structure becomes more regular and pore size tends to be smaller that was observed by SEM. The adsorption capacities of chitosan-containing aerogels to Congo red reach as high as about 150 mg/g, much higher than that of pure silica (17 mg/g), demonstrating their potential as a class of novel adsorbent materials. A series of chitosan- and/or silica-based aerogels were fabricated, which were named as C5S0, C4S1, C1S1, C1S4, and C0S5, with different designed CS/SiO2 mass ratios of 100/0, 80/20, 50/50, 20/80, and 0/100, respectively. Their compositions and structures as well as adsorption properties to Congo red were analyzed and compared in detail.

Effect of the modified silica Nanofiller on the Mechanical Properties of Unsaturated Polyester Resins Based on Recycled Polyethylene Terephthalate

Unsaturated polyester resin (UPe)-based nanocomposites and fumed silica Aerosil R812S, R805 and R816, and R200 modified with phenyl terminal group, R200NPh, were prepared. UPe resins were synthesized from maleic anhydride and products of glycolysis, obtained by polyethylene terephthalate depolymerization with dipropylene glycol in the presence of tetrabutyl titanate catalyst. The obtained unsaturated polyesters were characterized by acid, hydroxyl, and iodine values and by FTIR and NMR analysis. The microstructural analysis of the prepared nanocomposites, performed by using transmission electron microscopy, confirmed that silica nanoparticles formed chain-like aggregates in the polymer matrix. The presence of modified silica nanoparticles had no influence on the glass transition temperature and thermal stability of polyester matrix. The tensile modulus, stress at break, and hardness of cured products increased with increasing silica content. The impact strength of cured samples was not influenced by the silica content. POLYM. COMPOS., 38:538–554, 2017. © 2015 Society of Plastics Engineers

Effective and highly recyclable ceramic membrane based on amorphous nanosilica for dye removal from the aqueous solutions

In this study, an adsorptive ceramic membrane was prepared by a simple dry pressing of a mixture of nanosilica produced from low cost rice husk by hydrothermal technique at sub-critical water conditions, calcium phosphate, and ammonium acetate together and then calcined at 600°C in air. Optimization of the raw materials ratio was found to be necessary to avoid crack formation during sintering process. The membrane microstructure, dye removal efficiency and the permeation flux of the membranes were investigated. The membrane was tested to remove the methylene blue from aqueous solution. Results show that the removal of the dye increases as the silica content increases in the all given membranes and it decreases with an increase in the ammonium acetate. Moreover, the water flux decreases with an increase in the silica content. The methylene blue adsorbed onto the silica membrane can be removed by calcination and the membrane could be recycled several times without any obvious loss in the adsorption performance. In conclusion, this study demonstrates a convenient strategy to prepare an effective adsorptive membrane, which can be applied as a highly recyclable membrane for the adsorption of organic maters.

Adsorption of Surface-Modified Silica Nanoparticles to the Interface of Melt Poly(lactic acid) and Supercritical Carbon Dioxide.

With the purpose of fabricating polymer nanocomposite foams and preventing coalescence in foaming processes, the interfacial tension of poly(lactic acid) (PLA)-silica composites is investigated in this work. Synthesized silica nanoparticles (SNs) with a CO2-philic surface modification are used as the dispersed nanoparticles. Interfacial tension is a key parameter in processing of polymer foams since it directly affects the final foam properties, such as cell size and cell density. Interfacial tension of silica-containing PLA and supercritical carbon dioxide (CO2) is measured using axisymmetric drop shape analysis profile (ADSA-P) pendant drop method at high pressures and high temperatures. The interfacial tension between PLA and supercritical CO2 is observed to decrease as a result of the nanoparticles' adsorption to the interface. These results indicate that the reduction in interfacial tension with increasing silica content significantly deviates from a linear trend; there is a minimum at 2 wt % loading of the SNs and then the interfacial tension curve reaches a plateau. Contact angle measurements show an affinity of the SNs for the polymer-supercritical CO2 interface, and these obtained results are used to calculate the binding energy of the nanoparticles to the PLA/CO2 interface. In addition to interfacial properties, the adsorption of silica nanoparticles at the interface is also studied in detail with scanning electron microscopy.

Investigating the structure–diffusion–bioactivity relationship of strontium containing bioactive glasses using molecular dynamics based computer simulations

Molecular dynamics simulations have been used to study the effect of SrO/CaO substitution and composition on the glass structure and ionic diffusion behaviors of bioactive glasses. The glass compositions studied include three bioactive glass compositions with silica content ranging from 46 to 65mol% that covers a wide range of bioactivity. The local environments around modifier cations such as strontium, calcium and sodium and the network structures such as Qn distribution and network connectivity of these glasses were determined as a function of composition. Ionic diffusion was studied by calculating the mean square displacement (MSD) to obtain self-diffusion coefficients and studying diffusion at different temperatures to obtain diffusion energy barriers. The ionic diffusion properties, together with the glass structure features, were used to understand the difference in dissolution and bioactivities of these glasses. It was found that sodium ions had a much higher diffusion coefficient and lower diffusion energy barrier than calcium and strontium ions and the diffusion coefficient of modifier cations decreases by several orders of magnitude with increasing silica content and decreasing bioactivity. The preexponential factor was found to dominate the values of cation diffusion coefficients while diffusion energy barriers are relatively insensitive to composition change in the glasses studied.

Composite membranes based on sulfonated poly(ether ether ketone) and SiO2 for a vanadium redox flow battery

Organic-inorganic composite membranes were prepared with sulfonated poly(ether ether ketone) (SPEEK) and different amounts of silica to improve chemical stability and vanadium hindrance for a vanadium redox flow battery. The durability of the prepared composite membrane was verified using a self-made dummy cell system and fully charged vanadium cathode half-cell electrolyte, which contained oxidative vanadium ions (VO2+). The prepared composite membranes, with covalent crosslinking between the organic polymer and inorganic particles, resulted in reduced vanadium permeability and enhanced chemical stability. Ion exchange capacity, water uptake, proton conductivity, and vanadium permeability decreased with increasing silica content. Selectivity was defined to consider both permeability and proton conductivity and resulted in a membrane that exhibited both high proton conductivity and low ion permeability simultaneously. The prepared 1 wt% silica composite membrane showed 133-fold higher selectivity compared with that of a Nafion112 membrane. After the stability test, the composite membrane showed little change compared to the membrane before the stability test, which confirmed the commercial prospect of SPEEK/SiO2 composite membrane for a vanadium redox flow battery.

English

Cellulases were produced from fungus Humicola fuscoatra MTCC 1409 by solid state fermentation under different cultural conditions viz. pH, incubation temperature, inoculum size and days of incubation in order to optimize the conditions for maximum enzyme production. The potential of cellulase pretreatment to increase the digestibility of paddy straw was also ascertained. Maximum enzyme production was achieved at pH 6.0 of Mandel media and at temperature 45°C. Inoculum size of 1×107 spores/ml was found to be optimum for maximum enzyme production. Enzyme production increased with the increase in days of incubation from 2 to 6 days and then declined thereafter. Cellulase units at the concentration of 1, 1.5 and 2 µmole/g were exogenously added to paddy straw and change in chemical composition of paddy straw was determined after 18, 24, 30 and 36 h of treatment. With increase in enzyme concentration and incubation period, the content of neutral detergent fibre (NDF), acid detergent fibre (ADF), cellulose and hemicellulose reduced gradually with simultaneous increase in lignin and silica content. The concentrations of NDF, ADF, cellulose and hemicellulose decreased by 9.2, 5.9, 10.8 and 23.4% respectively, however lignin and silica content increased by 9.7 and 6.4% respectively as compared to control (with no cellulase added) at 2 µmole enzyme concentration after 36 h of pretreatment. These results show that the enzyme produced from cellulolytic fungus H. fuscoatra is capable of increasing paddy straw digestibility and thus enhancing the utilization of paddy straw for different purposes. Key words: Cellulase production, Humicola fuscoatra, paddy straw, paddy straw digestibility.

Applicability of Cassie–Baxter equation for superhydrophobic fluoropolymer–silica composite films

In this study, surface topographies and wettabilities of flat and composite rough films of perfluoro-styrene (TM/S) random copolymers with silica particles were investigated. The water and oil repellencies of flat TM/S copolymer and rough silica-TM/S composite surfaces were studied with varying perfluoro and silica contents. Increase in silica content resulted in an increase in water contact angle values; water contact angle values increased from 113° up to 170°, and the resultant surfaces were showing extremely superhydrophobic behavior depending on their silica contents. However a decrease in hexadecane contact angles from 61° to 25° depending on both silica %wt and perfluoro content of the TM/S copolymer was seen. Applicability of Cassie–Baxter equation was also investigated for TM/S copolymer films with silica particles. The results showed that Cassie–Baxter equation cannot be used for superhydrophobic surfaces, however, can be applied to oleophilic surfaces with caution. The oil repellencies of TM/S flat films in the terms of contact angle hysteresis was also compared with perfluoroethyl alkyl methacrylate–methyl methacrylate copolymer (TM/MMA) by using oil drops with varying surface tensions between 20.9mN/m and 26.9mN/m. The surface oleophobicities were changed according to the characteristics of the functional groups of MMA and S. The dependency of work of adhesion results of TM/S flat surfaces on wt.% of perfluoroalkyl content was also examined.

Sintering behaviour and sinter properties of phosphorite

Phosphorite is the main raw material used in the production of phosphorus in chemical industries. Given the decrease in the supply of high-grade phosphorite lump ore, an agglomeration process must be performed for the phosphorite concentrate after beneficiation. In this study, the mineralogy, granulation and sintering of phosphorite ores from Leshan, China, were investigated. Phosphorite comprises four main phases, namely, fluorapatite, hydroxylapatite, quartz and dolomite. Results showed that an increase in the proportion of nucleation particles in the phosphorite improved the granulation test results, whereas the addition of silica was detrimental to the growth of the granule size and the permeability of the bed. The addition of 3% water to the concentrate that contained approximately 8·3% free water was optimal for the mixture without silica, whereas the addition of 4% water was optimal for the mixture with silica. The yield of strong sinter increased with the increase in carbon dosage up to 7%, but decreased with further increase in carbon dosages. The P2O5 content in the sinter also followed the same trend with the yield. The addition of silica was detrimental for both the sinter yield and the grade. Ca5(PO4)3F was identified as the main phase in the sinter. The formation of Ca2MgSi2O7 increased along with the increase in temperature and silica content. The agglomeration mechanism for phosphorite sintering should include ‘sintering’ and ‘pelletising’ processes.

Curing kinetic, thermal and adhesive properties of epoxy resin cured with cashew nut shell liquid

The curing kinetic, thermal and adhesive properties of epoxy resin cured with cashew nut shell liquid (CNSL) were investigated. The CNSL was used as a curing agent for epoxy resin. The epoxy resin cured with 10, 20 30, 40 and 50wt% of CNSL showed two-stages curing process between 165–170°C and 230–235°C. The solvent extraction experiment indicated that the CNSL content should not exceed 40wt% to avoid the presence of unreacted CNSL. The apparent activation energy (Ea) of 60/40 epoxy resin/CNSL copolymer was obtained from Friedman’s model-free method for both stages of curing process. The kinetic model and kinetic parameters were determined by Málek’s method and the reaction processes was simulated favorably by Sestak–Berggren (SB (m, n)) model. In addition, silica powder was used to improve the adhesion and thermal properties of copolymer. The epoxy resin/CNSL copolymer with 0.5wt% silica showed a substantial increase in the lap shear strength and thermal stability tended to increase with increasing silica content. The epoxy resin/CNSL composite showed a great potential for use as a high performance adhesive with good thermal stability.

Structure and Properties of Polybenzimidazole/Silica Nanocomposite Electrolyte Membrane: Influence of Organic/Inorganic Interface

Although increased number of reports in recent years on proton exchange membrane (PEM) developed from nanocomposites of polybenzimidazole (PBI) with inorganic fillers brought hope to end the saga of contradiction between proton conductivity and variety of stabilities, such as mechanical, thermal,chemical, etc.; it still remains a prime challenge to develop a highly conducting PEM with superior aforementioned stabilities. In fact the very limited understanding of the interactions especially interfacial interaction between PBI and inorganic filler leads to confusion over the choice of inorganic filler type and their surface functionalities. Taking clue from our earlier study based on poly(4,4'-diphenylether-5,5'-bibenzimidazole) (OPBI)/silica nanocomposites, where silica nanoparticles modified with short chain amine showed interfacial interaction-dependent properties, in this work we explored the possibility of enhanced interfacial interaction and control over the interface by optimizing the chemistry of the silica surface. We functionalized the surface of silica nanoparticles with a longer aliphatic chain having multiple amine groups (named as long chain amine modified silica and abbreviated as LAMS). FTIR and (13)C solid-state NMR provided proof of hydrogen bonding interactions between the amine groups of modifier and those of OPBI. LAMS nanoparticles yielded a more distinguished self-assembly extending all over the OPBI matrix with increasing concentrations. The crystalline nature of these self-assembled clusters was probed by wide-angle X-ray diffraction (WAXD) studies and the morphological features were captured by transmission electron microscope (TEM). We demonstrated the changes in storage modulus and glass transition temperature (Tg) of the membranes, the fundamental parameters that are more sensitive to interfacial structure using temperature dependent dynamic mechanical analysis (DMA). All the nanocomposite membranes displayed enhanced mechanical, thermal and chemical stability than neat OPBI. The lower water uptake and swelling ratio and volume in both acid and water reflected the more hydrophobic characteristic of the nanocomposites. All the nanocomposite membranes showed phosphoric acid (PA) values to be higher than OPBI but the levels showed decreasing trend with increasing silica content; the reason attributed to the interparticle interaction. The self-assembled clusters of LAMS nanoparticles in the matrix created more sites for proton hopping as a result of which the proton conductivity of all the nanocomposites displayed an increasing trend.

Leaf silica concentration in Serengeti grasses increases with watering but not clipping: insights from a common garden study and literature review.

Grasses (Poaceae) lack the complex biochemical pathways and structural defenses employed by other plant families; instead they deposit microscopic silica (SiO2) granules in their leaf blades (i.e., phytoliths) as a putative defense strategy. Silica accumulation in grasses has generally been considered an inducible defense; other research suggests silica accumulation occurs by passive diffusion and should therefore be closely coupled with whole plant transpiration. We tested the hypothesis that grasses increase leaf silica concentration in response to artificial defoliation in a common garden study in the Serengeti ecosystem of East Africa. Additionally, a watering treatment tested the alternative hypothesis that leaf silica was largely driven by plant water status. Leaf silica content of two dominant C4 Serengeti grass species, Themeda triandra and Digitaria macroblephara, was quantified after a 10-month clipping × water experiment in which defoliation occurred approximately every 2 months and supplementary water was added every 2 weeks. Themeda had greater silica content than Digitaria, and Themeda also varied in foliar silica content according to collection site. Clipping had no significant effect on leaf silica in either species and watering significantly increased silica content of the dominant tall grass species, Themeda, but not the lawn species, Digitaria. Our data, and those collected as part of a supplementary literature review, suggest that silicon induction responses are contingent upon a combination of plant identity (i.e., species, genotype, life history limitations) and environmental factors (i.e., precipitation, soil nutrients, grazing intensity). Specifically, we propose that an interaction between plant functional type and water balance plays an especially important role in determining silica uptake and accumulation.

Extreme trace elements fractionation in Cenozoic nephelinites and phonolites from the Moroccan Anti-Atlas (Eastern Saghro)

article i nfo Nephelinites and phonolites from the Moroccan Anti-Atlas form a cogenetic series of volcanic rocks linked by a fractional crystallization process and showing continuous evolutionary trends for trace-elements. According to partial melting calculations, minor element data in olivine and review of published experimental studies, the most primitive nephelinites are low degree (~2%) partial melts from a carbonated LREE-rich spinel lherzolite. Sr-Nd-Pb isotopic compositions indicate the participation of both DM and HIMU end-members in the mantle source of nephelinites; the HIMU component is here interpreted as a relic of the shallow metasomatized Pan- African mantle. The phonolites show similar isotopic composition except for slightly more radiogenic Sr isotopic values. Fractional crystallization calculations were performed using trace-element mineral/bulk rock coefficients determined with new LA-ICP-MS data on minerals together with published equilibrium partition coefficients. The decrease of LREE, Sr and Ba with increasing differentiation is explained by fractionation of large amounts of apatite. Th, Nb and Zr display a behavior of very incompatible elements, reaching extreme concentration in most differentiated phonolites. Ta, Hf and MREE by contrast are characterized by a moderately incompatible to compatible behavior during differentiation. Fractionation of small amount of titanite, in which Ta, Hf and MREE are highly compatible compared to Nb, Zr and LREE (DNb/DTa: 2, DZr/DHf: 1.5 for titanite/phonolite ratios), explains the observed increase in Nb/Ta and Zr/Hf ratios with increasing silica content, from 18 and 40 in nephelinites to 70 and 80 in phonolites, respectively. Clinopyroxene also contributed to the fractionation of Hf from Zr in the very first steps of crystallization. The low values of Nb/Ta and Zr/Hf ratios observed in the two most differentiated Si-rich phonolites are probably a consequence of late stage segregation of volatile-rich agpaitic assemblages in the underlying magma chamber. Two phonolites with extreme Sr contents plot outside fractionation trends, as a result of the remelting of previously crystallized nephelinitic rocks in depth.

Polyimide-silica sol–gel membranes from a novel alkoxysilane functionalized polyimide: preparation, characterization and gas separation properties

Novel polyimide-organosilicate hybrid films were prepared by sol–gel process from a novel functionalized polyimide with alkoxysilanes as pendant groups that increase the affinity between inorganic and organic phases. The synthesis of this functionalized polyimide was carried out by an esterification reaction of a copolyimide containing carboxylic acid groups with allyl alcohol and subsequent hydrosililation. Tetraethoxysilane was used as precursor of silica in different amounts to obtain hybrid membranes with a silica content of 5, 10 and 20 %. The polymers and hybrid membranes were structural, mechanical and thermally characterized. The 29Si-NMR solid state spectroscopy confirmed that silica was covalently bonded to the polyimide. SEM pictures showed a good dispersion of the silica particles and an amorphous morphology was observed by WAXS. DSC analyses revealed an increase in rigidity with the increase in silica content. The mechanical strength of the hybrid membranes decreased with the silica amount, exhibiting a brittle behavior. The evaluation of the gas permeation properties revealed that the film with the lowest silica content showed the highest permeability coefficients for O2, N2, CH4, and CO2 with 34, 8, 6, and 128 barrers respectively, while all hybrid membranes showed similar permselectivities around 4 and 22 for O2/N2 and CO2/CH4 respectively. The fractional free volume of hybrid membranes determined by positron annihilation lifetime spectroscopy followed the same trend that permeability coefficients, confirming that the gas transport properties are mainly governed by the free volume elements.

Influence of Cation-Exchanged Copper on the Adsorption of Phenol onto Zeolite Beta

The aim of this research was to examine the effect of copper cation-exchanged zeolites on the adsorption uptake of organic pollutants. Two beta zeolites with silica-to-alumina ratios of 25:1 and 150:1 were modified by copper cation exchange and their potential for the removal of phenol from aqueous solutions was investigated. It was found that copper loading could be increased by increasing the pH of the exchange to 7. The exchanged copper was found to be relatively resistant to leaching between 5 and 11. An increase in copper loading or silica content resulted in an increase in the adsorption capacity of the zeolite for phenol. Overall, it was found that the adsorption showed best fit to the generalized Langmuir-Freundlich isotherm model. The adsorption process was exothermic and yielded thermodynamic parameters that were contiguous with phenol adsorption.

Y3Al5O12–SiO2 Glasses: Structure and Polyamorphism

Aerodynamic levitation and CO2 laser melting have been used to synthesize the yttrium aluminosilicate glasses zY2O3–yAl2O3–xSiO2 with z/y = 3/5 corresponding to the YAG (Y3Al5O12) composition and x between ~5 and ~45 mol%. The low‐ and high‐density (LDA inclusion and HDA matrix) polyamorphic phases in glasses with less than ~14 mol% SiO2 were identified with backscattering electron imaging. Polarized and depolarized Raman spectra show the formation of various Qn SiO4 species whose relative populations change smoothly as the SiO2 content is altered. The AlOs (s = 4–6) and YOz (z = 6–9) polyhedra formed in the YAG glass are preserved upon silica additions while the terminal oxygens of the Q2AlO4 tetrahedra are gradually bridged to the Qn‐SiO4 species. The low‐frequency Boson Peak overlaps with the vibrational spectrum and its maximum is redshifted with increasing silica content. Micro‐Raman spectra measured for the LDA and HDA amorphous phases are found to be similar to the spectra of the bulk glass indicating common structural characteristics. The stability of the LDA phase against crystallization appears to be lower than that of the HDA phase. The crystallinity on certain inclusions consisted of YAG microcrystals and a new unidentified microcrystalline phase within Y4Al2(1−x)Si2xO(9+x) solid solution.

Liquid crystalline phase behavior of silica nanorods in dimethyl sulfoxide and water.

We report lyotropic smectic liquid crystalline phase behavior of silica nanorods dispersed in binary mixtures of dimethyl sulfoxide (DMSO) and water (H2O). The phase behavior is affected by nanorod size polydispersity and DMSO concentration in the binary solvent. The isotropic to biphasic transition is strongly affected by the relative amount of DMSO in the solvent, but the solvent has little effect on the biphasic to liquid crystal transition above 40/60 DMSO/H2O by volume. At less than 40% DMSO, increasing silica nanorod concentration initially results in the formation of liquid crystalline domains, but further increasing silica concentration results in crystal solvate formation. The morphology of the liquid crystalline phase is strongly affected by the size polydispersity, with lower polydispersity leading to a more uniform structure. As in other lyotropic nanocylinder systems, the microstructure of continuous solid films produced from the dispersions was affected by both the initial microstructure and the applied shear.

Development and characterization of novel organic–inorganic hybrid sol–gel films

Organic–inorganic hybrid films were fabricated by reacting 3-glycidoxypropyltrimethoxysilane with 4,4′-diaminodiphenylether by hydrolysis and condensation reaction with acid catalysis. The chemical bonding between the organic and inorganic phases provides reinforcement to the films, and tetraethoxysilane was added in such a way that silica contents varied from 1 wt% to 3 wt% in the films. Structural characterization of the hybrid films was performed using Fourier transform infrared and nuclear magnetic resonance spectroscopic techniques. The thermal properties studied using thermogravimetric analysis, indicate an improved thermal stability for the films according to the percentage concentration of silica present in them. The water absorption was also found to be reduced for the films with increased silica content. The surface morphology was investigated by means of x-ray diffraction and scanning electron microscopic techniques. The films transparency and homogeneity seem to have been affected severely when the silica content kept on increasing and ultimately led to opaqueness in film.