Optical characterization of poly (ethylene oxide)/zinc oxide thin films

The optical characterization of poly (ethylene oxide)/zinc oxide thin films has been done by analyzing the absorption spectra in the spectral wavelength region 380–800 nm using a ultraviolet-spectrophotometer at room temperature. Thin film polymer composites made of poly (ethylene oxide) (PEO) containing zinc oxide (ZnO) filler concentrations (0%, 2%, 6%, 10%, and 14%) by weight were used in this study. The optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The optical energy gap and other basic optical constants such as dielectric constants and optical conductivity were investigated and showed a clear dependence on the ZnO filler concentration. It was found that the optical energy gap for the composite films is less than that for the neat PEO, and that it decreases as the ZnO concentration increases. Enhancement of the optical conductivity was observed with increase in the ZnO concentration. Dispersion of refractive index was analyzed using the Wemple–DiDomenico single oscillator model. The refractive index (n), extinction coefficient (k), and dispersion parameters (E_o, E_d) were calculated for the investigated films.     

改性钢渣-矿粉复合橡胶填料补强-阻燃机理的光谱学分析

钢渣作为炼钢过程中产生的固体废弃物,矿渣作为高炉炼铁过程中的副产品,其存在难以利用与附加值的问题。面对上述问题,利用钢渣与矿渣开发一种价格低廉的复合橡胶填料用于橡胶领域。采用磁选热闷渣、未磁选热闷渣、矿粉和助磨-改性复合剂制备改性钢渣-矿粉复合橡胶填料,并且用于复合橡胶体系。研究磁选热闷渣用量、未磁选热闷渣用量、矿粉用量和助磨-改性复合剂用量对改性钢渣-矿粉基橡胶复合材料性能的影响,并且分析其影响机理。结果表明,以磁选热闷渣用量150 g、未磁选热闷渣用量150 g、矿粉用量150 g和助磨-改性复合剂用量9 g制备的改性钢渣-矿粉复合橡胶填料补强-阻燃性能最优。按改性钢渣-矿粉复合橡胶填料∶炭黑质量比20∶30制备的改性钢渣-矿粉基橡胶复合材料,其拉伸强度为21.83 MPa、撕裂强度为46.23 kN·m-1、邵尔A硬度为62、磨耗量为159 mm3、极限氧指数为19.8%与燃尽时间为187 s。助磨-改性复合剂不仅降低粒径尺寸、提高粒径均匀性,而且改善钢渣-矿粉复合橡胶填料的表面结构与性质,有利于改性钢渣-矿粉复合橡胶填料在复合橡胶体系中均匀分散,提高相容性。钢渣与矿粉在助磨-改性复合剂的作用下发生化学反应,改变了钢渣与矿粉的物相组成,提高补强性能与阻燃性能。     

Effects of Rice Husk Derived Amorphous Silica on the Thermal-Mechanical Properties of Unsaturated Polyester Composites

Rice husk is rich in amorphous silica which has found various applications as a filler in rubbers and plastics. In the research described here silica was extracted from rice husk ash in the form of sodium silicate which was used to produced amorphous precipitated silica (PS) and silica aerogel (SA) using a sol – gel process and supercritical drying. These materials were then physically mixed with unsaturated polyester (UP) resin and cured at room temperature to form polymer composites. The experimental results showed that the UP composites with 30% (volume percent) of SA filler had lower density and better thermal insulation than the composites with the same amount of PS. Thermogravimetric analysis (TGA) results showed that the T_onset of the PS and SA composites were slightly delayed by 15 and 10°C, respectively. The tensile stress-strain curves showed that addition of the fillers reduced the tensile strength, but increased the elastic moduli of the UP matrix. PS filled UP composites exhibit higher moduli (higher stiffness) than that of SA filled UP composites. This was due to agglomeration and poor adhesion of the SA particles to the UP matrix while better dispersion was observed for the PS filled composite.     

Fused silica as a composite nanostructured material

A method for calculating the refractive index of optical fused silica by applying the model of effective permittivity of composite homogeneous media is proposed and realized. The calculation was performed using the tabular data of the refractive index of crystalline α quartz and the ratio of the quartz glass and α quartz densities. It was suggested that fused silica contains nanosized pores with a glass filling number q immersed in a matrix with a density differing from the α quartz density by a factor of κ, where κ is slightly less than unity. It was established that the Maxwell-Garnett model makes it possible to calculate the refractive index of quartz glass and its dispersion in the transparency range (404 nm ≤ λ ≤ 671 nm) with a deviation less than 0.0002 from the tabular values. The calculated and experimental values coincide at q = 0.155 and κ = 0.986.     

Styrene-butadiene-glycidyl methacrylate terpolymer/silica composites: dispersion of silica particles and dynamic mechanical properties

Styrene-butadiene-glycidyl methacrylate terpolymer (GMA-SBR) was synthesized by emulsion polymerization for the fuel efficient tire tread composite. The chemical structure of the GMA-SBR was analyzed using infrared spectroscopy, ¹H NMR, gel permeation chromatography, and differential scanning calorimetry. The GMA-SBR/silica composite is the first instance introduced covalent bonds between silica filler and rubber molecules by in-chain modification of styrene-butadiene molecules. After compounding, the curing characteristics, the mechanical and dynamic mechanical properties of the composites were analyzed. The GMA-SBR/silica composite exhibited higher wear resistance of 32.9% and lower rolling resistance of 25.7% than the styrene-butadiene rubber 1721/silica composite. These results are due to the improvement of silica dispersion in the composite as the covalent bonding increased the filler–rubber interaction and the countervailing effects of less filler flocculation. The proposed approach assists in finding a solution to improve the performances of tires for fuel efficiency and the reduction of greenhouse gases from the vehicles.     

Fracture of polystyrene- and molecular silica sol-based nanocomposites during fast compression

Polystyrene-based composites containing hybrid molecular silica sol nanoparticles with a core-shell structure are studied during fast compression. Polystyrene and the related composites are found to fail instantaneously at a certain critical pressure, which is accompanied by the emission of electromagnetic and acoustic waves. The composite composition changes the critical pressure during explosion and the frequency characteristics of the generated electromagnetic and acoustic waves. The charge density transfer mechanism in a composite with a filler concentration higher than 10 wt % is shown to differ from that in composites with a lower filler content.     

Preparation and Mechanical Properties of Composites Based on Rigid Polyvinyl Chloride Filled with Organic Modified Illite Powder

Illite powder, modified by an aluminate coupling agent, was used as a filler to strengthen polyvinyl chloride (PVC) resin with mechanical properties of rigid PVC/modified illite composite being tested. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied for the structural characterization of the raw materials. SEM and Fourier transform infrared spectroscopy (FTIR) measurements were used for demonstrating the effect of modification of the illite powder. Results from tests of mechanical properties showed that, when the dosage of modified illite powder was 2 parts per hundred parts by weight, there was an obvious toughening effect on rigid PVC material; the notched impact strength was increased by 59% in comparison to neat rigid PVC, but the elongation of the composites decreased slightly.     

Resonant nonlinear optics of backward waves in negative-index metamaterials

The extraordinary properties of resonant four-wave mixing of backward and ordinary electromagnetic waves in doped negative-index materials are investigated. The feasibility of independent engineering of the negative refractive index and the nonlinear optical response as well as quantum control of the nonlinear propagation process in such composites is shown due to the coherent energy transfer from a control field to a signal field. Laser-induced transparency, quantum switching, frequency-tunable narrow-band filtering, amplification, and realizing a miniature mirrorless optical parametric generator of the entangled backward and ordinary waves are among the possible applications of the investigated processes.     

Intense photoluminescence at 2.7 μm in transparent Er 3+:CaF2-fluorophosphate glass microcomposite

Er3+ doped CaF2-fluorophosphate (FP) glass microcomposites were produced by heat-treating the mixture of Er3+:CaF2 precipitate and FP glass powder above the melting temperature of the FP glass. The appearance of CaF2 crystallites in the resulting composites was confirmed by x ray diffraction. Despite the fact that the average diameter of the crystallites was around 10 μm as revealed by the micromorphology study, a transparent composite was obtained by matching the refractive index of FP glass to that of CaF2. Intense IR fluorescence at around 2.7 μm was observed in the composite, implying the composite would be a promising candidate for IR lasers and amplifiers.     

Silica doped tin oxide composite anodes for lithium-ion batteries

Silica doped tin oxide composites prepared by a sol gel method have been studied as negative electrode materials for lithium-ion batteries. The composite powders fired at 500 °C were analysed by means of XRD and SEM and showed that the composite consists of a blend of crystalline and amorphous structure with different particle size distribution. The electrochemical properties of this anode material were examined by charge-discharge measurements and cyclic voltammetry. The silica doped tin oxide composite anode, which was cycled between 0.1 to 2.0 V, showed a reversible capacity of 270 mAh/g. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Dynamical anisotropic magnetoelectric effects at ferroelectric/ferromagnetic insulator interfaces

The interfacial magnetoelectric interaction originating from multi-orbital hopping processes with ferroelectricassociated vector potential is theoretically investigated for complex-oxide composite structures.Large mismatch in the electrical permittivity of the ferroelectric and ferromagnetic materials gives rise to giant anisotropic magnetoelectric effects at their interface.Our study reveals a strong linear dynamic magnetoelectric coupling which genuinely results in electric control of magnetic susceptibility.The constitutive conditions for negative refractive index of multiferroic composites are determined by the analysis of light propagation.     

Optical properties of composites with nanodimensional oxide coatings versus the properties of film-forming sols. I. The influence of sol’s oxide composition

The influence of the aging period (duration) and the aging-related rheological characteristics of film-forming solutions (sols) on the refractive index and thickness of coatings, light reflection and light transmission coefficients, and optical losses in glass substrate-nanodimensional oxide (CuO-TiO₂) composites is considered. It has been shown that the increase in the CuO concentration in the coating and the extension of the sol aging period favor crystallization and change the form of inclusions in the coating from pseudospherical to dendritic with a different degree of branching. The refractive index of the film and its related coefficient of mirror reflection of the composite are functions of the density of packing sol disperse-phase particles into a nanodimensional layer. The packing density of dendritic particles drops decreases with the degree of their branching and transverse size of fragments. In every case, an optimal sol aging period should be found to obtain glass composites with nanodimensional coatings offering desired optical properties.     

Influence of filler type on wet skid resistance of SSBR/BR composites: Effects from roughness and micro-hardness of rubber surface

The wet skid resistance (WSR) of SSBR/BR(solution styrene-butadiene rubber/butadiene rubber) composites filled with carbon black, silica, and nano-diamond partly replacing carbon black or silica, respectively, was measured with a portable British Pendulum Skid Tester (BPST). A dynamic mechanical thermal analyzer was used to obtain the viscoelasticity of the composites. A 3D scanning white-light interfering profilometer was used and the scratch test performed to characterize surface roughness and micro-roughness, respectively, of the composites. WSR of the silica-filled composite was better than that of the carbon black-filled one, and further enhancement of WSR was obtained by replacing silica with nano-diamond. Tan δ of the composites at 0 °C, 10 Hz, and tensile strain of 2% did not show good correlation with WSR. The surface roughness of the composites had effects on WSR. The scratch test indicated that the higher the hardness of the filler in the composite, the higher the micro-hardness and the better the WSR. Therefore, the surface micro-hardness of the composites is an important factor affecting WSR, besides viscoelasticity and surface roughness.     

Superior refractive index tailoring properties in composite ZrO2/SiO2 thin film systems achieved through reactive electron beam codeposition process

Composite optical thin-film materials have received a significant amount of interest in order to relieve the material constraints on refractive indices as well as reducing the number of layers required in optical coating design. Amongst others binary zirconia-silica composite thin films have attracted considerable attentions due to their several favorable opto-mechanical properties. In the present studies such a composite system under certain compositional mixings displayed both refractive index and band gap supremacy over pure zirconia films violating the most popular Moss rule. This unexpected evolution has several practical applications one of which can be directly employed in extending the range of tunability of the refractive index. Besides, the probing of such a novel evolution through the analysis of ellipsometric refractive index modeling and morphological correlation functions has revealed several novel as well as superior microstructural properties in the composite thin film systems. All these characterization and analysis techniques distinctly indicate a strong interrelation between the microstructural ordering and superior optical properties of the present zirconia-silica codeposited composites.     

Polymer-precursor-derived (am-) SiC/TiC composites for resistive heaters in large volume multi-anvil high pressure/high-temperature apparatus

(Amorphous-)SiC/TiC composites for resistive tubular heaters in HP/HT experiments were obtained via a polymer-precursor process. A slurry consisting of a commercial SiC-precursor polymer (allylhydridopolycarbosilane, AHPCS) and TiC powder as conductive filler was applied to the inner walls of zirconia insulation tubes, using a centrifugation-casting method. Resistive coatings with homogeneous thickness of ～200 μm were obtained. The heaters were tested in octahedral multi-anvil assemblies at ～10 GPa with simultaneous recording of heating voltage and current. Up to a maximum temperature of ～1800°C they showed temperature vs. power characteristics reproducible from batch to batch, with resistance decreasing from 0.08 to 0.02 Ω during heating. Microstructural characterization using SEM/EDX was carried out on the recovered SiC/TiC composite material, as well as on pristine resistive heaters directly after coating and curing to 230°C, and after additional pyrolysis at 900°C in argon. In all cases, a stable composite microstructure of an interpenetrating network of TiC particles with either silicon carbide polymer precursor or an amorphous SiC phase were found. The composites were characterized by XRD and thermogravimetry. Further improvement of coating procedure and materials combination (precursor/filler/insulator substrate) may result in advanced coatings, operational well beyond 2000°C.     

Interface effect in the silicone rubber/mineral powder composites

Silicone rubber/mineral powder composites have been prepared by surface modification and ultrafinecrashing of mineral powder, mixing and vulcanizing with silicone rubber resin. The surface and interface energy for mineral filler and silicone rubber matrix were investigated. It was found that there is a correlation between W _a/σ_SL (interfacial adhesive work/interfacial tension) and the tensile strength of the corresponding composite, especially for unmodified ultrafine mineral filler. On the other hand, the chemical modification of the surface changes the surface group on the mineral filler and results in improvement of the interfacial interaction between silicone rubber matrix and mineral filler, consequently, altering the reinforcing effect of the mineral filler.     

基于石墨烯超表面的宽带电磁诱导透明研究

提出了一种新的基于石墨烯超表面的复合结构,该结构由带有空气槽的石墨烯条、氮化镓、二氧化硅和二氧化钛组成.通过时域有限差分法研究了该结构的电磁特性,研究结果表明,该结构具有更宽频带的电磁诱导透明特性.从结构参数、电磁场分布等方面研究了电磁诱导透明的物理机理.在该结构中,石墨烯条作为明模存在,耦合作为暗模的空气槽和氮化镓侧板,即存在两种明暗模耦合的现象,因此产生宽带的电磁诱导透明现象.从研究结果发现该结构可以产生多个频点的慢光效应和传感效应,因此在光存储、红外波段的传感器设计中具有一定的指导意义和潜在的应用.     

Effect of particles size on the optical constants of iron/polystyrene composites via UV-radiation

The present study deals with the optical characteristics of polystyrene (PS) composites containing iron particles of different sizes: 5, 40, 110, and 250 μm. The optical absorption spectra were collected in the wavelength range 300–800 nm using a UV-spectrophotometer. The optical results obtained were analyzed in terms of the absorption formula for non-crystalline materials. The optical energy gap and other basic optical constants such as refractive index, dielectric constants, and optical conductivity were investigated and showed a clear dependence on the iron particles size. It was found that the optical energy gap for the iron-filled composites is less than that for the neat PS, and it decreases as the iron particle size decreases. The refractive index of the prepared composites was determined from the collected transmittance and reflectance spectra. It was found that the calculated dielectric constant and refractive index of the composites increase when the iron particles size decreases. The optical dispersion behavior of the composites was described by the single-oscillator model. Enhancement in the optical conductivity was observed with decreasing the iron particles size.     

Effect of Polyethylene Functionalization on Mechanical Properties and Morphology of PE/SiO2 Composites

In this study composites of high density polyethylene (HDPE) with various SiO₂ content were prepared by melt compounding using maleic anhydride grafted polyethylene (PE-g-MAH) as a compatibilizer. The composites containing 2, 4 and 6% by weight of SiO₂ particles were melt-blended in a co-rotating twin screw extruder. In all composites, polyethylene-graft-maleic anhydride copolymer (PE-g-MAH, with 0.85% maleic anhydride content) was added as a compatibilizer in the amount of 2% by weight. Morphology of inorganic silica filler precipitated from emulsion media was investigated. Mechanical properties and composite microstructure were determined by tensile tests and scanning electron microscopy technique (SEM). Tensile strength, yield stress, Young's modulus and elongation at break of PE/SiO₂ composites were mainly discussed against the properties of PE/PE-g-MAH/SiO₂ composites. The most pronounced increase in mechanical parameters was observed in Young's modulus for composites with polyethylene grafted with maleic anhydride. The increase in the E-modulus of PE/PE-g-MAH/SiO₂composites was associated with the compatibility and improvement of interfacial adhesion between the polyethylene matrix and the nanoparticles, leading to an increased degree of particle dispersion. This finding was verified on the basis of SEM micrographs for composites of PE/PE-g-MAH/4% by weight of SiO₂. The micrographs clearly documented that addition of only 2 wt% of the compatibilizer changed the composite morphology by reducing filler aggregates size as well as their number. Increased adhesion between the PE matrix and SiO₂ particles was interpreted to be a result of interactions taking place between the polar groups of maleic anhydride and silanol groups on the silica surface. These interactions are responsible for reduction of the size of silica aggregates, leading to improved mechanical properties.     

Fermat原理在左手媒质中的推广

 在考虑左、右手媒质定义对比基础上，定义了广义折射率，并对Fermat原理的表述进行了推广。从电磁理论出发，得到了折射率的具体表示。广义的折射率可以通过媒质电参数有效地表现理想及人工复合左、右手媒质中折射的负正特性。以此所得理论可以有效描述由左、右手媒质所共同构成的折射率可变的混合稳态电磁或光学传输系统。讨论了折射率的高频形式，并对负折射现象进行了讨论。