Synthesis of ZnOAl2O3 core-shell nanocomposite materials by fast and facile microwave irradiation method and investigation of their optical properties

Alumina (Al₂O₃) coated ZnO core-shell structures were synthesized by a novel, fast, and facile route utilizing microwave (MW) irradiation to control photocatalytic property of ZnO. The phase analysis and the core–shell structure development were corroborated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), X-ray fluorescence (XRF), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDX) analysis and Fourier transform infrared spectroscopy (FT-IR). The XPS results affirmed that elements on the coated surface were Al and O. Zeta potential analysis predicted the presence of Al₂O₃ layer on ZnO due to almost similar zeta potential curve for pure Al₂O₃ and Al₂O₃ coated ZnO nanoparticles. There was no significant change in band gap energy of ZnO after amorphous Al₂O₃ coating as obtained from derived data of the reflectance spectra but gradual decreasing of reflectance in the visible range, measured by UV–vis spectroscopy, of the prepared core-shell nanoparticle may be due to the coating of amorphous Al₂O₃ on ZnO. The photocatalytic efficiency of ZnO was reduced after amorphous Al₂O₃ layer as confirmed by the photodegradation of methylene blue under UV irradiation.     

溶胶-凝胶技术制备光化学杂化材料

溶胶 -凝胶技术是制备有机 -无机杂化材料的重要手段 ,在光致变色、光纤传感和发光等光化学杂化材料制备方面应用前景广阔。提高光致变色染料的稳定性、制备溶胶 -凝胶光纤及降低杂化材料羟基含量是目前的研究重点。     

Alternative method for preparation of CdS/epoxy resin nanocomposite

Hybrid composites of CdS nanoparticles embedded in epoxy resin matrixes have been prepared by co-precipitate method and characterized. Epoxy resin acted as the matrix for the formation of nano CdS particles in the reaction system and kept them from agglomerating. The resulting viscous orange liquid could be cured with normal curing agent. The result of XRD, UV and TEM analysis reveals that the CdS particles are in nano size and dispersed in epoxy resin matrix homogeneously.     

Synthesis of Ag-AgBr/Al-MCM-41 nanocomposite and its application in photocatalytic oxidative desulfurization of dibenzothiophene

A series of Ag-AgBr/Al-MCM-41 nanocomposites were synthesized by dispersion of Ag-AgBr on mesoporous silica Al-MCM-41 obtained from natural bentonite. The synthesized Ag-AgBr/Al-MCM-41 composites with Ag nanoparticles growing on the surface of Al-MCM-41 were used for photocatalytic oxidative desulfurization of dibenzothiophene. The physical properties of Ag-AgBr/Al-MCM-41 were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Ultraviolet–visible diffuse reflection spectroscopy (UV–Vis DRS), photoluminescence (PL) emission spectra, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity results showed that in the presence of 40% Ag-AgBr/Al-MCM-41 photocatalyst the oxidative desulfurization of dibenzothiophene reached the maximum efficiency at 99.22% and the photocatalytic activity still keeps high level after four cycles.     

纳米复合材料的研究进展

研制开发具有特殊性质的新型纳米复合材料具有广阔的发展前景。本文对近几年来纳米复合材料的最新研究进展进行了综合论述。按照复合方式的不同，分别对4种复合体系的纳米复合材料进行了系统介绍，包括材料的结构组成，制备技术，功能特性以及研究进展状况等，并对纳米复合材料的应用与发展前景进行了展望。     

Preparation and optical limiting properties of a POSS-containing organic-inorganic hybrid nanocomposite

A novel POSS-containing organic-inorganic hybrid nanocomposite (P) was prepared by the Pt-catalyzed hydrosilylation reaction of octahydridosilsesquioxane (T₈^H) with substituted acetylene, CH≡CCH₂O-C₆H₄-COO-C₆H₄-p-NN-C₆H₄-p-OCH₃ (M). The hybrid nanocomposite was soluble in common solvents such as CHCl₃, THF, toluene and C₂H₄Cl₂. Its structure was characterized by FT-IR, ¹H NMR, and ²⁹Si NMR, respectively. Optical limiting property was evaluated by a Q-switched Nd:YAG laser system with a wavelength of 532 nm, 4 ns pulse width and a repetition of 1 Hz. The result shows that the POSS-based organic-inorganic hybrid nanocomposite exhibits novel optical limiting property, well photo and high thermal stability (T_d, temperature for 5% weight loss, as high as 319 °C). The optical limiting property increases with the increase of solution concentration.     

溶胶-凝胶法制备环氧/SiO2纳米杂化材料及其性能研究

以异氰酸丙基三乙氧基硅烷(IPTS)接枝环氧树脂(EP)合成出了一种新型的环氧预聚物(IEP),由IEP通过溶胶-凝胶法制备出了EP/SiO2杂化材料。通过FT-IR、AFM、TG、DMA表征和分析了杂化材料的化学结构、SiO2纳米粒子在EP基体中的分散性和无机纳米粒子的引入对EP树脂热性能和力学性能的影响。结果表明,原位生成的纳米SiO2粒子在EP基体中的分散性良好,其平均尺度约为50nm;杂化材料的热性能和力学性能相比于纯EP有了很大程度的提高。     

Tribological behavior of nanocomposite coatings based on fullerene-like structures

This paper presents a new group of nanocomposite coatings based on integrating inorganic fullerene-like material (IFLM) structures into conventional coating matrices. Such coatings have been developed within the scope of the European funded FOREMOST project (FP6-NMP3-CT-2005-515840).Regarding the synthesis of these nanocomposite coatings based on fullerene-like components, two alternative routes were explored: introducing preformed IFLMs into the coating deposition process or forming the fullerene-like components in situ during the coating deposition process. Both methods have been demonstrated to be technically feasible, depending on the nature of the coating matrix or the desired fullerene-like structure.These new materials allow some independent control of tribological properties usually known as antagonists (very high load bearing capacity with a very low friction coefficient). In the case of unidirectional movement, under dry conditions, the best coatings developed in FOREMOST displayed a coefficient of friction in air within the range 0.04-0.10, depending on the degree of humidity and the test conditions. Pure sliding laboratory tests indicate that for some industrial applications fullerene-like nanocomposite coatings can give significant reductions in wear and friction coefficient when compared to similar coatings without fullerene-like components. The lubrication mechanisms through which these fullerene-like structures improve friction and prevent wear are also discussed in this paper.     

纳米SnO2、ZnO及ZnO／SnO2复合材料的气敏性能研究

以ZnO、S如纳米颗粒及ZnO／SnO2复合纳米材料分别作为气敏基料制成旁热式气敏元件,运用扫描电镜观察产物的形貌,用静态配气法对浓度为100ppm的甲烷气体进行气敏性能的测试。结果表明,这几类元件的最佳工作温度及灵敏度差异较大,当工作温度为350℃时SnO2纳米颗粒的气敏性能最佳。此温度下,SnO2响应时间和恢复时间也比纯ZnO纳米颗粒分别缩短了2S和3S。     

Analytical solutions of the displacement and stress fields of the nanocomposite structure of biological materials

Biological materials, such as bone and nacre, are nanocomposites of protein and mineral with superior mechanical properties. The basic building blocks of these materials feature a generic nanocomposite structure with staggered alignment of mineral platelets in protein matrix. Because of the structural complexity of the generic structure, its displacement and stress fields are currently still unknown. In this study, a perturbation method was applied for analytically solving the displacement and stress fields of the nanocomposite structure under uniaxial tension. The effect of the elastic modulus, aspect ratio and volume fraction of mineral and protein on the displacement and stress fields in the nanocomposite structure was studied. A non-dimensional parameter γ was then suggested for characterizing the stress and strain fields in this nanostructure. We showed that the assumption of uniform shear stress distribution at the mineral-protein interface in the TSC model is valid when γ is less than 4 which is broadly applicable to most biological materials. The analytical solutions of displacement and stress fields obtained in this study provide a solid basis for further analyses of mechanical properties, such as the buckling and the fracture behaviors of biological materials.     

Synthesis and characterization of the tellurium/calcium silicate nanocomposite

A novel tellurium/calcium silicate nanocomposite with tellurium nanorods homogeneously dispersed in the calcium silicate matrix has been successfully synthesized using corresponding tellurium nanorods, Ca(NO₃)₂·4H₂O, and Na₂SiO₃·9H₂O in ethanol/water mixed solvents at room temperature for 48 h. The new material consists of a single crystalline Te core and an amorphous calcium silicate shell. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and energy-dispersive X-ray spectroscopy (EDS). The method is simple and does not need any surfactant or template or base. Cytotoxicity experiments indicated that the tellurium/calcium silicate nanocomposites with a low concentration had good biocompatibility. This nanocomposite is a very promising candidate for the application as bioactive materials.     

Synthesis and catalytic activity of different substituted metal phthalocyanine-MWCNTs hybrid materials for selective oxidation of styrene

An efficient process for the preparation of novel [4α(OPh-t-Bu)MPc]-MWCNTs and tetranitro substituted metal phthalocyanine (MTNPc)-MWCNTs hybrid catalysts was developed via an ultrasonic impregnation method. The obtained hybrid materials were characterized comprehensively with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectra (FT-IR). The oxidation of styrene was examined using tert-Butyl hydroperoxide (TBHP) as oxidant, and using MTNPc-MWCNTs and [4α(OPh-t-Bu)MPc]-MWCNTs complexes (M: Zn and Co) as catalysts. The results indicated that cobalt phthalocyanines were more efficient catalysts in the styrene oxidation reaction as compared to zinc phthalocyanine. It was found that during reaction with tert-butyl hydroperoxide (TBHP) as the oxidant, the conversion and selectivity of all synthesized compounds in dimethylformamide (DMF) was higher than in acetonitrile (CH₃CN). Moreover, the catalytic mechanism of styrene oxidation has been proposed for the different substituted metal phthalocyanine-MWCNTs hybrid materials.     

Synthesis of stearic acid/Si02 hybrid phase change materials by ultrasound assisted

在超声波的促进作用下,以正硅酸乙酯为溶胶前驱体、硬脂酸为相变组分,经溶胶一凝胶过程制备了硬脂酸／SiO2复合定形相变储能材料。为了研究硬脂酸／SiO2复合定形相变储能材料的制备工艺,考察了不同超声功率对材料制备过程中加强两相传质作用的辅助效果的影响以及不同种类催化剂对材料制备过程中溶胶一凝胶过程的影响,最后确定出具有良好定形效果下材料的最大硬脂酸质量分数为60％。超声辅助酸碱复合催化法制备硬脂酸／SiO2材料具有无需添加助溶剂和表面活性剂、凝胶速度快、方法简便的优点。对硬脂酸／SiO2复合定形相变储能材料进行了FTIR结构表征和DSC、TG热性能及热稳定性测试,产品的相变焓值达91．46J／g,在低于175℃具有良好的热稳定性。     

A hybrid finite element method for heterogeneous materials with randomly dispersed rigid inclusions

A hybrid finite element approach is proposed for the mechanical response of two-dimensional heterogeneous materials with linearly elastic matrix and randomly dispersed rigid circular inclusions of arbitrary sizes. In conventional finite element methods, many elements must be used to represent one inclusion. In this work, each inclusion is embedded inside a polygonal element and only one element is required to represent one inclusion. In numerically approximating stress and displacement distributions around the inclusion, classical elasticity solutions for a multiply-connected region are employed. A modified hybrid functional is used as the basis of the element formulation where the displacement boundary conditions of the element are automatically considered in a variational sense. The accuracy and efficiency of the proposed method are demonstrated by two boundary value problems. In one example, the results based on the proposed method with only 64 hybrid elements (450 degrees of freedom) are shown to be almost identical to those based on the traditional method with 2928 conventional elements (5526 degrees of freedom).     

Microstructure and mechanical properties of TiZrAlN nanocomposite thin films by CFUBMS

Quaternary TiZrAlN nanocomposite thin films were deposited by Closed-Field Unbalanced Magnetron Sputtering (CFUBMS), and their microstructure and mechanical properties were examined. The grain refinement of the TiZrAlN nanocomposite thin films was controlled by adjusting the N₂ partial pressure. The hardness of the film varied with the N₂ partial pressure with a maximum value of approximately 47 GPa. A critical grain size, d_c, was found to be essential for maximizing the hardness.     

Synthesis of density-controlled ZnO nanoneedle arrays on a flexible substrate by addition of Al salts and use of microwave irradiation

We synthesized density-controlled ZnO nanoneedle arrays on a flexible substrate (Teflon) by the addition of aluminum chloride to the growth solution and application of microwave irradiation at 95 °C for 30 min. The density of ZnO nanoneedles on the substrate could be controlled by adjusting the concentration of aluminum chloride added to the reaction solution. After the reaction, the only species observed in the bulk solution were zinc aluminum layered double hydroxides (ZnAl:LDHs); these ZnAl:LDHs played a critical role in controlling the ZnO density on the substrate. On the basis of our results, we propose a mechanism for the density-controlled growth of ZnO nanoneedles.     

Synthesis of TTCP by using inverse micelle method

Tetracalcium phosphate (TTCP, Ca₄(PO₄)₂O) is one of the major powder components of self-setting orthopedic and dental cements. Traditionally, TTCP powders are produced by a solid-state reaction of Ca- and P-containing precursors between 1350 and 1500 °C. Such procedures require expensive high-temperature furnaces and subsequent grinding of sintered particles. Grinding not only leads to the contamination but also alters the structure of TTCP, thereby reducing its bioactivity. The present paper offers an innovative approach to the inverse micelle method of TTCP synthesis, with a subsequent thermal treatment to obtain purer TTCP phase. The obtained powder was a mixture of TTCP and octacalcium phosphate (OCP) phases for thermally untreated sample, while for the sample thermally treated at 800 °C it was a mixture of TTCP and β-TCP phases. The TTCP phase was prevailing phase in both cases. A typical shape of TTCP nanoparticles was needle-like. Somewhere, needles are joined together forming platelet-like structures. Investigations of the obtained phases were made by XRD and TEM. The mechanism of chemical synthesis and structural arrangements of the obtained phases were particularly investigated.     

Single-step synthesis of MWCNT/ZnO nanocomposite using co-chemical vapor deposition method

Single-step synthesis of MWCNT and ZnO nanocomposite was conducted by co-chemical vapor deposition method. Electron microscopic analysis revealed that the fabricated nanostructures consisted of MWCNTs with a diameter of 60-70 nm which were coated with ZnO nanoparticles with an average size of 20-30 nm. The growth of ZnO nanoparticles took place after the formation of MWCNTs. EDS and XRD analyses could confirm the high crystallinity of ZnO deposited on the MWCNT surface. In comparison with pristine MWCNTs and ZnO nanoparticles, the UV absorption of MWCNT/ZnO nanocomposite was changed through modification with ZnO nanoparticles.     

超声辅助溶胶凝胶法制备硬脂酸/SiO2定形相变储能材料

在超声波的促进作用下, 以正硅酸乙酯为溶胶前驱体、 硬脂酸为相变组分, 经溶胶-凝胶过程制备了硬脂酸/SiO₂复合定形相变储能材料。为了研究硬脂酸/SiO₂复合定形相变储能材料的制备工艺, 考察了不同超声功率对材料制备过程中加强两相传质作用的辅助效果的影响以及不同种类催化剂对材料制备过程中溶胶-凝胶过程的影响, 最后确定出具有良好定形效果下材料的最大硬脂酸质量分数为60%。超声辅助酸碱复合催化法制备硬脂酸/SiO₂材料具有无需添加助溶剂和表面活性剂、 凝胶速度快、 方法简便的优点。对硬脂酸/SiO₂复合定形相变储能材料进行了FTIR结构表征和DSC、 TG热性能及热稳定性测试, 产品的相变焓值达91.46 J/g, 在低于175℃具有良好的热稳定性。      

Fabrication of photonic crystals on several kinds of semiconductor materials by using focused-ion beam method

In this paper, we introduced the fabrication of photonic crystals on several kinds of semiconductor materials by using focused-ion beam machine, it shows that the method of focused-ion beam can fabricate two-dimensional photonic crystal and photonic crystal device efficiently, and the quality of the fabricated photonic crystal is high. Using the focused-ion beam method, we fabricate photonic crystal wavelength division multiplexer, and its characteristics are analyzed.