溶胶凝胶法制备CNT／ZnO纳米复合材料及其光催化性研究

Chemistry and Chemical Engineer School, Henan Institute of Science and Technology, Xinxiang, Henan 453003, China     

Hybrid Nonlinear Optical Materials Containing Imidazole Chromophore through the Sol‐Gel Process

A new sol‐gel hybrid film based on heterocyclic chromophore, namely 2‐[4′‐(N‐ethyl‐N‐hydroxyethyl)amino phenyl azo]‐4,5‐dicyanoimidazole (IZ), has been synthesized and characterized. The hybrid system possesses a high chromophore loading density up to 65 wt.‐% without observing a phase separation. The initial decomposition temperatures of the chromophore and hybrid material were determined to be 260 and 272 °C, respectively. Poled films show a fairly high and stable nonlinear optical (NLO) response, even at an elevated temperature.

     

Mechanical,thermal, and UV‐shielding behavior of silane surface modified ZnO‐reinforced phthalonitrile nanocomposites

In the present work, zinc oxide nanoparticles were treated with aminopropyl trimethoxy silane‐coupling agent and used as a new kind of reinforcement for a typical high performance bisphenol‐A‐based phthalonitrile resin. The resulted nanocomposites were characterized for their mechanical, thermal, and optical properties. Results from the tensile test indicated that the tensile strength and modulus as well as the toughness state of the matrix were all enhanced with the increasing of the nanoparticles amount. Thermogravimetric analysis showed that the starting decomposition temperatures and the residual weight at 800°C were highly improved upon adding the nanofillers. At 6 wt% nanoloading, the glass transition temperature and the storage modulus were considerably enhanced reaching about 359°C and 3.7 GPa, respectively. The optical tests revealed that the neat resin possesses excellent UV‐shielding properties, which were further enhanced by adding the nanofillers. Furthermore, the fractured surfaces of the nanocomposites analyzed by scanning electron microscope exhibited homogeneous and rougher surfaces compared with that of the pristine resin. Finally, the good dispersion of the reinforcing phase into the matrix was confirmed by a high resolution transmission electron microscope. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of Monolithic Ti‐incorporated Mesoporous Silica Materials via Tartaric Acid Templated Sol‐gel Process

Monolithic and transparent Ti‐incorporated mesoporous silica materials of large size (e.g. 2 mm) in dimension have been prepared with tartaric add (TA) as template via sol‐gel reactions of tetraethyl orthosilicate (TEOS) and tetrabutyl titanate (TBT). The materials are characterized by infrared (IR), nitrogen adsorption‐desorption isotherms, powder X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicate that the monolithic materials exhibit large specific surface areas (ca. 1200 mVg) and pore volumes (ca. 0.900 cm³/g).     

Non‐hydrolytic Sol‐gel Methodology to Prepare a Molecularly Imprinted,Organic‐silica Hybrid‐based Stir Bar for Recognition of Sulfonylurea Herbicides

Based on a molecularly imprinted organic‐silica hybrid‐based stir bar, a pre‐treatment methodology was developed for enrichment of nicosulfuron in aqueous samples. The molecularly imprinted organic‐silica hybrid‐based coating on the outer surface of a glass stir bar was prepared by in‐situ polymerization using nicosulfuron as a template molecule, α‐methacrylic acid as a functional monomer, methacryloxypropytrimethoxysilane as a cross‐linker in the mixture of acetonitrile and trichloromethane (V/V, 7.5:1). To achieve the selective extraction of the target analyte from aqueous samples, several main parameters, including extraction time, pH value and contents of inorganic salt in the sample matrix were investigated. Evidence was also presented by the scanning electronic microscopic images of the imprinted and non‐imprinted stir bars. Then, the extraction efficiency of the stir bar was tested with separate experiments and competitive sorption experiments. These results showed that using six sulfonylureas as substrates the molecularly imprinted organic‐silica hybrid‐based stir bar gave high selectivity for the template, nicosulfuron compared to the non‐imprinted organic‐silica hybrid‐based stir bar. This sorption extraction was coupled to liquid chromatography ultraviolet detection allowing the determination of nicosulfuron from tap water. The method showed good recoveries and precision, 96.0% (RSD 2.7%, n=3) for tap water spiked with 0.125 nmol (25.00 mL sample), suggesting that the stir bar can be successfully applied to the pre‐concentration of nicosulfuron in real aqueous samples.     

Robust Organic/Inorganic Hybrid Porous Thin Films via Breath‐Figure Method and Gelation Process

A novel organic/inorganic hybrid honeycomb patterned porous thin film was prepared using the breath‐figure method combined with a sol‐gel process. An in situ formed gelable block copolymer, formed by mixing poly(styrene‐alt‐maleic anhydride)‐block‐polystyrene (P(St‐a‐MAn)‐b‐PS) and 3‐aminopropyltrimethoxysilane (APS), was used as the structure directing agent. The porous film produced was dipped into an acid aqueous solution to induce a sol‐gel process in the wall of film. As a result of gelation, the structure of this film transformed into a crosslinked silica oxide hybridized with PS, and this film resisted those organic solvents which were once good solvents for the copolymer precursor.

     

Characterization of Nano‐porous TiO2 Film Prepared by Sol‐gel Process and Its Application to Dye‐sensitized Solar Cell

In this paper, effects of ethylene glycol (EG) and indium tin oxide (ITO) solution on the morphology, porosity, and roughness of TiO₂ film prepared by sol‐gel process were investigated and discussed. Initially, the addition of EG were used to control the viscosity of the solution and it was found to increase the pore size of TiO₂ film. The various TiO₂ films were investigated and characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and then assembled to dye‐sensitized solar cell (DSSC) to measure the photoelectric conversion efficiency. The optimum efficiencies of 1.32% with J_sc and V_oc of 2.99 mA/cm² and 0.80 V, respectively, were obtained by the TiO₂ film prepared from a solution containing 20 wt% EG.     

Self‐reinforced composites based on commercial PP woven fabrics and a random PP copolymer modified with quartz

Self‐reinforced composites based on commercial polypropylene (PP) woven fabrics and a random PP copolymer modified with quartz were obtained by film stacking. The effect of the incorporation of quartz on the materials fracture and failure behavior was studied through uniaxial tensile tests and quasi‐static fracture experiments. Acoustic emission analysis was also performed in situ in the tensile tests. A higher consolidation quality was obtained for the composites containing quartz. In the composite with random PP modified with 5 wt% quartz, the higher consolidation and the better dispersion of quartz particles positively impacted on the materials tensile and fracture behavior. From the results of acoustic emission analysis, fiber fracture appears as the dominant failure mechanism in the investigated composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation,characterization, and properties of novolac‐type phenolic/SiO2 hybrid organic–inorganic nanocomposite materials by sol–gel method

This article describes the preparation of novolac‐type phenolic resin/silica hybrid organic–inorganic nanocomposite, with a sol–gel process. The coupling agent was used to improve the interface between the organic and inorganic phases. The effect of the structure of the nanocomposite on its physical and chemical properties is discussed. The coupling agent reacts with the resin to form covalent bonds. The structure of the modified hybrid nanocomposites was identified with a Fourier transform infrared spectroscope. The silica network was characterized by nuclear magnetic resonance imaging (²⁹Si NMR). Results revealed that Q₄ (tetrasubstituted) and T₃ (trisubstituted) are the dominant microstructures. The size of the silica in the phenolic resin was characterized with a scanning electron microscope. The size of the particles of inorganic silica in the modified system was less than 100 nm. The nanocomposite exhibited good transparency. Moreover, the thermal and mechanical properties exhibited significant improvement. The modified hybrid composite exhibited favorable thermal properties. The temperature at which a weight loss of 5% occurred increased from 281 to 350 °C. The flexural strength increased by 6–30%. The limiting oxygen index of the nanocomposite reached 37, and the Underwriters Laboratory test was 94V‐0. Consequently, these materials possess excellent flame‐retardant properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 905–913, 2003     

Investigation of irradiation dose rate on curing characteristics of carbon fiber/polymer composites by low‐energy electron beam

During in situ low‐energy electron beam (E‐Beam) curing for carbon fiber‐reinforced polymer composite, prepregs undergoes 3 sequenced curing processes, namely E‐Beam‐induced curing, postray curing after irradiation, and thermally induced curing. In this study, the irradiation dose rate (IDR) is demonstrated to be influential on the redistribution of the curing portions in the 3 curing stages and directly influences the interlaminar bonding quality of the stepwise cured laminates. Differential scanning calorimetry results showed that higher IDR resulted in higher temperature of irradiated prepregs, and hence, a higher degree of curing was induced by the E‐Beam within a dose range of 0 to 500 kGy as compared to lower IDRs, which decreased the interlaminar physical adhesive quality between layers. Analysis indicates that other than pure physical adhesion between uncured layers, postray curing can further enhance the interlaminar shear strength for cured laminates by introducing cross‐layer chemical bonding in the interlaminar zone.     

Copper Oxide Nanoparticle Modified Sol–Gel‐Derived Carbon Ceramic by Microwave Irradiation,and Its Application for Determination of Adenine at Very Low Potential

In this work the copper oxide nanoparticles simultaneous with sol–gel‐derived carbon ceramic production were synthesized and doped in ceramic by microwave irradiation in a few minutes without using any catalyst and organic solvent. The ceramic composition was characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and Fourier transforms infrared (FT‐IR), and its surface morphology was investigated by scanning electron microscopy (SEM). The proposed ceramic with detection limit of 0.1 µM, was used for electrocatalytic determination of adenine at potential about 700 mV lower than its usual oxidation potential.     

Sequential interpenetrating poly(ethylene glycol) hydrogels prepared by UV‐initiated thiol–ene coupling chemistry

Poly(ethylene glycol) (PEG)‐diallyls, ranging from 2 to 8 kDa, were successfully reacted with a trifunctional thiol crosslinker via thiol–ene coupling reaction to construct four different primary PEG hydrogels. These systems were used as scaffolds for the preparation of a library of sequential interpenetrating networks (SeqIPNs). The solid content of the secondary networks varied between 21 and 34% and was dependent on the length of the absorbing PEGs. The gel fractions for the IPNs were above 85%. Additionally, the lowest degree of swelling was found for the IPN based on 2‐kDa PEG (315%), whereas the 8‐kDa PEG IPN exhibited a value of 810%. The SeqIPN strategy facilitated hydrogel systems that cover a larger domain of tensile modulus (192–889 kPa) when compared with single hydrogel networks (175–555 kPa). © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Properties of an organosilicon nanophase generated in a poly(amide imide) matrix by the sol‐gel technique

Poly(amide imide) (PAI) nanocomposites prepared by the in situ generation of crosslinked organosilicon nanophase (ON) through the sol‐gel process were characterized by wide‐angle and small‐angle X‐ray diffraction, thermogravimetric analysis, dynamic mechanical analysis and kinetics of water uptake. It was concluded that the polymer nanocomposite (PNC) were likely to possess a complex morphology on the nanoscale characterized by co‐existence of two mixed nanophases of different compositions. At low methyl triethoxysilane (MTS) contents the fractal‐like organization of paracrystalline nano‐domains of PAI chain fragments is destroyed by the randomly distributed ON particles, whereas on the increase of MTS content the spatial correlations between ON particles become stronger, giving rise to their own fractal‐like structure. The higher values of small‐angle X‐ray scattering (SAXS) invariant, apparent water diffusivity and limiting water uptake for the PNC compared to the pristine PAI were assumed to reflect the loose inner structures of PAI‐rich and ON‐rich nanophases, respectively. Copyright © 2005 John Wiley & Sons, Ltd.     

Nanostructured organic–inorganic hybrid films prepared by the sol–gel method from self‐assemblies of PS‐b‐paptes‐b‐PS triblock copolymers

ABA‐based triblock copolymers of styrene as block ends and gelable 3‐acryloxypropyltriethoxysilane (APTES) as the middle block were successfully prepared through nitroxide‐mediated polymerization (NMP). The copolymers were bulk self‐assembled into films and the degree of phase separation between the two blocks was evaluated by differential scanning calorimetry (DSC). Their morphology was examined through small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM), whereas the mechanical properties of the corresponding cross‐linked self‐assembled nanostructures were characterized by dynamic mechanical analysis (DMA). Acidic treatment of the triblock copolymers favored the hydrolysis and condensation reactions of the APTES‐rich nanophase, and induced a mechanical reinforcement evidenced by the increase of storage modulus values and the shift of the glass transition temperature to higher temperatures due to confinement effects. In addition, the lamellar structure of the hybrid films was retained after the removal of the organic part by calcination. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011