Atomistic simulations for adsorption and separation of flue gas in MFI zeolite and MFI/MCM-41 micro/mesoporous composite

Adsorption of pure CO_(2) and N2 and separation of CO_(2)/N2 mixture in MFI zeolite and MFI/MCM-41 micro/mesoporous composite have been studied by using atomistic simulations.Fully atomistic models of MFI and MFI/MCM-41 are constructed and characterized.A bimodal pore size distribution is observed in MFI/MCM-41 from simulated small-and broad-angle X-ray diffrac-tion patterns.The density of MFI/MCM-41 is lower than MFI,while its free volume and specific surface area are greater than MFI due to the presence of mesopores.CO_(2) is preferentially adsorbed than N2,and thus,the loading and isosteric heat of CO_(2) are greater than N2 in both MFI and MFI/MCM-41.CO_(2) isotherm in MFI/MCM-41 is similar to that in MFI at low pressures,but resembles that in MCM-41 at high pressures.N2 shows similar amount of loading in MFI,MCM-41 and MFI/MCM-41.The selectivity of CO_(2) over N2 in the three adsorbents decreases in the order of MFI>MFI/MCM-41>MCM-41.With increasing pressure,the selectivity increases in MFI and MFI/MCM-41,but decreases in MCM-41.The self-diffusivity of CO_(2) and N2 in MFI decreases as loading increases,while in MFI/MCM-41,itfirst increases and then drops.

Hydrothermal Synthesis and Properties of Y-zeolite-containing Composite Material with Micro/mesoporous Structure

A Y-zeolite-containing composite material with micro/mesoporous structure had been synthesized from kaolin by means of the in-situ crystallization method. The obtained samples were investigated by XRD and BET methods. Evaluation of catalytic activity of both the commercial Y-zeolite and the novel Y-zeolite-containing composite material was carried out in the pulse micro-chromatography platform with two probe molecules of different molecular sizes： VGO feedstock and 1,3,5 tri-isopropyl benzene. It was found that the Y-zeolite-containing composite material was richer in external surface and meso-/macro-pores; the Y-zeolite-containing composite material demonstrated a smaller rate of deactivation compared to the commercial Y-zeolite.

Synthesis,Characterization and Catalytic Properties of Mesoporous HPMo/SiO_2 Composite

A novel mesoporous HPMo/SiO2 composite was synthesized by the sol-gel method with triblock copolymer EO20PO70EO20 as template.The properties of the product were characterized by X-ray diffraction,transmission electron microscopy,N2 adsorption-desorption isotherms,Fourier transform infrared spectrometer and inductively-coupled plasma analysis.The experimental results show that the product has a very ordered hexagonal mesostructure,and the HPMo is immobilized into the framework of silica.The final mesoporous composite shows excellent stability in polar solvents.Results of catalytic tests indicate that the composite is an effective catalyst for oxidation of dibenzothiophen,and there are few activity losses even after the third cycle of uses.The high catalytic activity and good insolubility make it a promising catalyst in oxidative desulfurization process.

Synthesis, Characterization of Mesoporous Al-Mg Composite Oxide and Catalytic Performance for Oxyethylation of Fatty Alcohol

A mesoporous Al-Mg composite oxide with a hexagonal structure was synthesized with aluminium nitrate and magnesium nitrate as the reagents and sodium dodecyl sulfate（SDS） as the template in the presence of ethylenediamine. The XRD, nitrogen adsorption-desorption and TEM studies indicate that the composite has a hexagonal framework structure and an average pore diameter of 2. 6 nm. The TG/DTA spectra indicate that the decomposition and the removal of the occluded surfactant of the sample take place in a range of 230-550 ℃. The mesoporous Al-Mg composite oxide exhibites a highly catalytic activity for the oxyethylation of fatty alcohols. Narrow-range distributed ethoxylates are formed in the presence of the mesoporous Al-Mg composite oxide catalyst. The distribution selectivity coefficient（Cx） is 24 when the mesoporous Al-Mg composite oxide was used as a catalyst for the oxyethylation of octanol and the average adduct degree of ethoxylates is 6. 4.

Synthesis and Characterization of Worm-shaped Tubular Lanthanum Aluminum Composite Mesoporous Materials

The lanthanum aluminum mesoporous materials were synthesized using sodium dodecyl sulfate as a template agent by ultrasonic hydrothermal method.The resulting samples were characterized by low angle X-ray diffraction（XRD）,N2 adsorption-desorption studies,transmission electron microscopy（TEM）and surface morphology analysis（SEM）,surface acid（NH3-TPD）,reducibility properties（TPR）,X-ray energy dispersive spectrometer（EDS）and thermogravimetric analysis（TG/DTG）.A l/La composite mesoporous material were synthesized with n（Al）︰n（La）=70︰1.0,80°C of reaction temperature,20 h of reaction time,12 h of crystallization time,650°C of calcination temperature.The specific surface area of the sample is 273.90 m 2 ·g ？1 ,with the average diameter 5.642 nm and pore volume 0.2354 cm 3 ·g ？1 .The samples have mesoporous structure and its particles are similar to a worm-shaped tubular structure.The influence of calcination temperature on the surface physical and chemical properties of Al/La composited mesoporous materials was examined,and the results showed that the acid strength was increased but the amount of acidic sites is decreased as the calcination temperature increased.It was found that the sample calcined at 650°C had appropriate acid content,acid strength and better reducibility.

Characterization and adsorption behaviors of a novel synthesized mesoporous silica coated carbon composite

A novel mesoporous silica coated carbon composite(denoted SEG) with hierarchical pore structure has been successfully prepared in an aqueous solution that contains triblock copolymer template, aluminum chloride, siliceous source and expanded graphite. Textural property and morphology of the SEG composite were characterized by the combination of X-ray diffraction, N_2 adsorption–desorption, scanning electron microscopy,transmission electron microscopy and Fourier transform infrared measurements. Results show that mesoporous silica is steadily and uniformly grown on the surface of the graphite slices and the thickness of the silica layer can be finely tuned according to the silica/C molar ratio in the initial reaction solution. This newly synthesized SEG composite shows greatly increased adsorption capacity to methylene blue than the pristine expanded graphite in the batch tests. Both Langmuir and Frendlich models were further used to evaluate the adsorption isotherms of methylene blue over expanded graphite and SEG samples with different silica contents. Finally, pseudosecond-order model was used to describe the kinetics of methylene blue over expanded graphite and the silica-carbon composites.

Supramolecular-templated synthesis of mesoporous silica-zirconia nanocomposite

Mesoporous SiO2-ZrO7 nanocomposite was successfully prepared by using supramolecular tfiblock copolymer as the template through evaporation-induced self-assembly approach. The textural and structural properties were characterized by X-ray diffraction, nitrogen adsorption analysis, and transmission electron microscope. Comparison between pure mesoporous silica and mesoporous silica-zirconia nanocomposite was also presented in this work. The surface area, pore size, and pore volume decreased as the Zr doping in the mesoporous silica framework. But the obtained nanocomposite maintained the cubic Im3m-type mesoporous structure.

MICRO MECHANICAL ANALYSIS OF 3-D WOVEN COMPOSITES

A micro mechanical model is carried out to predict micro stresses and macro elastic properties of 3-D woven composites. A unit cell is composed of two phases. One is fiber yarn and the other is resin or fiber yarn in transverse. The additional shearing introduced by bending of fiber yarn is considered. The method to determine the microstructure is also discussed. This model is applied to the analysis of a 3-D woven graphite/epoxy composite. Micro stresses of the cell are studied, and then macro modulus is obtained by employing the average method. The predictions agree well with experimental results.

Micro Mechanical Model of 3D Woven Composites

A combined beam model representing the periodicity of the microstructure and micro deformation of 3D woven composites is developed for predicting mechanical properties. The model considers the effects of off axial tension/compression and bending/shearing couplings as well as the mutual reactions of fiber yarns. The method determining microstructure by using woven parameters is described for a typical 3D woven composite material. An analytical cell, constructed by a minimum periodic section of yarn and interlayer matrix, is adopted. Micro stresses in the cell under in-plane tensile loading are obtained by using the proposed beam model and macro modulus is then obtained by the averaging method. Material tests and a 2D micro FEM analysis are made to evaluate this model. Analyses reveal that micro stress caused by tensile/bending coupling effect is not negligible in the stress analysis.

PLASTIC LIMIT ANALYSIS OF DUCTILE COMPOSITE STRUCTURES FROM MICRO-TO MACRO-MECHANICAL ANALYSIS

The load-bearing capacity of ductile composite structures comprised of periodic composites is studied by a combined micro/macromechanicai approach. Firstly, on the microscopic level, a representative volume element （RVE） is selected to reflect the microstructures of the composite materials and the constituents are assumed to be elastic perfectly-plastic. Based on the homogenization theory and the static limit theorem, an optimization formulation to directly calculate the macroscopic strength domain of the RVE is obtained. The finite element modeling of the static limit analysis is formulated as a nonlinear mathematical programming and solved by the sequential quadratic programming method, where the temperature parameter method is used to construct the self-stress field. Secondly, Hill＇s yield criterion is adopted to connect the micromechanicai and macromechanical analyses. And the limit loads of composite structures are worked out on the macroscopic scale. Finally, some examples and comparisons are shown.

Micro Model of Carbon Fiber/Cyanate Ester Composites and Analysis of Machining Damage Mechanism

Machining damage occurs on the surface of carbon fiber reinforced polymer (CFRP) composites during processing. In the current simulation model of CFRP, the initial defects on the carbon fiber and the periodic random distribution of the reinforcement phase in the matrix are not considered in detail, which makes the characteristics of the cutting model significantly different from the actual processing conditions. In this paper, a novel three-phase model of carbon fiber/cyanate ester composites is proposed to simulate the machining damage of the composites. The periodic random distribution of the carbon fiber reinforced phase in the matrix was realized using a double perturbation algorithm. To achieve the stochastic distribution of the strength of a single carbon fiber, a novel method that combines the Weibull intensity distribution theory with the Monte Carlo method is presented. The mechanical properties of the cyanate matrix were characterized by fitting the stress-strain curves, and the cohesive zone model was employed to simulate the interface. Based on the model, the machining damage mechanism of the composites was revealed using finite element simulations and by conducting a theoretical analysis. Furthermore, the milling surfaces of the composites were observed using a scanning electron microscope, to verify the accuracy of the simulation results. In this study, the simulations and theoretical analysis of the carbon fiber/cyanate ester composite processing were carried out based on a novel three-phase model, which revealed the material failure and machining damage mechanism more accurately.

Erosion Wear Behaviour of Kenaf/Glass Hybrid Polymer Composites

The awareness amongst the researchers to develop an environment friendly sustainable material leads to explore new class of plant-based fiber for making composites. Hybridization of such plant-based fiber with inclusion of engineered fiber is one of the promising methods to not only enhanced the mechanical performance but also suppressed the drawbacks that associate with such plant-based fiber to some extent. A usual hand lay-up method was taken-up in this work to fabricate four layered of hybrid kenaf(K)/glass(G)polyester laminates with different stacking order such as KKKK,KGKG,KGGK,GKKG and GGGG. The erosive character of the laminates was examined under three distinct particle velocities(48m/s, 70m/s,82m/s)and four different impact angles(30°, 45°, 60°, 90°). All fabricated laminates exhibited a semiductile character at lower velocities(48m/s and70m/s)as peak wear rate was observed at45° impact angle. However,they showed a semi-brittle character at high velocity(82m/s)as maximum rate of erosion was noticed at60° impact angle. Again,the influence of stacking order of piles on erosion wear was also clearly noticed. Moreover,the semi-brittle/semi-ductile characterization was also evidenced in accordance to the range of erosion efficiencies. The micro-structures of worn surfaces were inspected thoroughly from the images of scanning electron microscope(SEM)to evident the mechanism of erosion.

Stress and buckling analysis of a thick-walled micro sandwich panel with a flexible foam core and carbon nanotube reinforced composite (CNTRC) face sheets

In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order shear deformation theory(HSDT)and the modified couple stress theory(MCST).The governing equations of equi-librium are obtained based on the total potential energy principle.The effects of various parameters such as the aspect ratio,elastic foundation,temperature changes,and volume fraction of the canbon nanotubes(CNTs)on the critical buckling loads,normal stress,shear stress,and deflection of the thick-walled micro cylindrical sandwich panel consider-ing different distributions of CNTs are examined.The results are compared and validated with other studies,and showing an excellent compatibility.CNTs have become very use-ful and common candidates in sandwich structures,and they have been extensively used in many applications including nanotechnology,aerospace,and micro-structures.This paper also extends further applications of reinforced sandwich panels by providing the modified equations and formulae.

Preparation and corrosion resistance of the micro-arc oxidation coating on Al_2O_3f/ZL109 composites

A ceramic layer was prepared on the surface of Al2O3f/ZL109 composites by means of micro-arc oxidation （MAO） technique. The surface morphology and phase constituent of the ceramic layer were analyzed using scanning electron microscope and X-ray diffraction. The polarization curves of the composites before and after MAO treatment were measured and analyzed. The results showed that after Al2O3f/ZL109 composites were treated using MAO technique in silicate solution, the ceramic layer formed, and it was composed of Al, Si, and mullite phase. Al and Si came from Al alloy matrix of the composites, and the mullite phase formed in process of MAO. Al2O3 fiber in the composites affects the electric conductivity of the composites, the MAO reaction is promoted, and the cera- mic layer forming on the composite material side is slightly thicker than that on the Al alloy side. After Al2O3f/ZL109 composites were treated using MAO technique, the corro- sion resistance of the composites is significantly improved.

CORROSION AND MECHANICAL BEHAVIOR OF COPPER-NIOBIUM NANO-FILAMENTARY MICRO-COMPOSITES FOR HIGH PERFORMANCE ELECTRICAL CONDUCTOR WIRE

Corrosion behavior of heavily drawn bundled Copper-niobium filamentarymicro-composite was studied as a function of niobium content to develop the relationship betweenmicrostructure and corrosion behavior in aqueous 30 percent HCl-FeCl_3 solution. TEM observationrevealed that niobium filaments were distributed regularly in copper matrix along the sides of atriangular unit cell in the transverse section and more sub-grain boundaries were absorbed atcopper/niobium phase boundaries with increasing niobium content. The corrosion potential and rate inaqueous 30 percent HCl-10 percent FeCl_3 was-680.3m V_(SHE) and 1.179 X 10^(-5)A/cm^2. Thecorrosion potential and rate decreased as increasing niobium content and FeCl_3. The yield stresscan be described as the sum of the substructure strengthening component due to elongated grains,subgrains and/or cells, the phase boundary strengthening term associated with the Hall-Petch typeinteraction between dislocations and phase boundaries and precipitate strengthening component.

Comparative Study of Micro and Nano Size WO3/E44 Epoxy Composite as Gamma Radiation Shielding Using MCNP and Experiment

The radiation shielding characteristics of 50wt% WO3/E44 epoxy composite in various gamma energies from 80 keV to 1.33 MeV are investigated via the MCNP code. Thus two scales are considered for WOa filler particles： micro and nano with sizes of i #m and 5Onto, respectively. The simulation results show that W03 nano particles exhibit a larger increase in linear attenuation coefficient in comparison with micro size particles. Finally, validation of simulation results with the published experimental data shows a good agreement.

Preparation and Mechanical Properties of Micro- and Nano-sized SiC/Fluoroelastomer Composites

Microand nano-sized SiC/fluoroelastomer （FKM） composites were prepared by a mechanical mixing method. These composites were first characterized by a rotorless rheometer. Then the effects of micro- and nano-sized SiC on hardness, static and dynamic mechanical properties of the composites were investigated. The increasing amount of the SiC filler increased the curing efficiency of the biphenyl curing system, which was evident from the rheometric properties of the resulting composites. The tensile properties of composite increased with the increasing of micro- and nano-sized SiC content. When the micro- and nano-sized SiC content was higher than 20 phr, the composites showed almost unchanged tensile properties. The increasing of the tensile property was mainly attributed to the well dispersed micro- and nano-sized SiC particles characterized by SEM images. Compared to pure FKM, the composites exhibited a higher glass transition temperature and lower tan peak value.

Al_2O_3-Y_2O_3 Nano- and Micro-Composite Coatings on Fe-9Cr-Mo Alloy

Al2O3-Y2O3 nano- and micro-composite coatings were deposited on Fe-9Cr-Mo substrates by using sol-gel composite coating technology. The processing includes dipping samples in a sol-gel solution dispersed with fine ceramic powders, which are prepared by high-energy ball milling. High-resolution microscopy （FE-SEM） analyses show that the coating is composed of composite particle clusters with an average diameter of 1μm, and the coating is relatively dense without cracking during drying and sintering stages. XRD analyses show that the oxide coating is mainly composed of α-Al2O3 and γ-Al2O3. The oxidation tests performed at 600℃ in air show that the coatings are provided with much improved resistance against high temperature oxidation and scale spallation. It is indicated that nano-structured composite particles and reactive elements are integrated into the coatings, which plays an important role in preventing agglomeration of nano-particles and initiation of cracks.

Magneto-rheological elastomer (MRE) based composite structures for micro-vibration control

Magneto-rheological elastomers （MILEs） are used to construct composite structures for micro-vibration control of equipment under stochastic support-motion excitations. The dynamic behavior of MREs as a smart viscoelastic material is characterized by a complex modulus dependent on vibration frequency and controllable by external magnetic fields. Frequency-domain solution methods for stochastic micro-vibration response analysis of the MRE-based structural systems are developed to derive the system frequency-response function matrices and the expressions of the velocity response spectrum. With these equations, the root-mean-square （RMS） velocity responses in terms of the one-third octave frequency band spectrum can be calculated. Further, the optimization problem of the complex moduli of the MRE cores is defined by minimizing the velocity response spectra and the RMS velocity responses through altering the applied magnetic fields. Simulation results illustrate the influences of MRE parameters on the RMS velocity responses and the high response reduction capacities of the MRE-based structures. In addition, the developed frequency-domain analysis methods are applicable to sandwich beam structures with arbitrary cores characterized by complex shear moduli under stochastic excitations described by power spectral density functions, and are valid for a wide frequency range.

Preparation of narrow band gap V_2O_5/TiO_2 composite films by micro-arc oxidation

V2Os/TiO2 composite films were prepared on pure titanium substmtes via micro-arc oxidation （MAO） in electrolytes consisting of NaVO3. Their morphology and dements were characterized by scanning electron microscopy （SEM） and energy-dispersive X-ray （EDX） analysis. Phase composition and valence states of species in the films were characterized by X-ray diffraction （XRD） and X-ray photoelec- tron spectroscopy （XPS）. Ultraviolet-visible diffuse reflectance spectra （UV-Vis DRS） were also employed to evaluate the photophysical property of the films. The VEOs/TiO2 composite films show a sheet-like morphology. Not only V205 phase appears in the films when the NaVO3 concentration of the electrolyte is higher than 6,10 g/L and is loaded at the surface of anatase, but also V4＋ is incorporated into the crystal lattice of anatase. In comparison with pure TiO2 films the V2Os/TiO2 composite films exhibit significantly narrow band gap energy. The film prepared in an electrolyte consisting of NaVO3 with a concentration of 8.54 g/L exhibits the narrowest band gap energy, which is approximately 1.89 eV. The V2Os/TiO2 composite films also have the significantly enhanced visible light photocatalytic activity. The film prepared in an electrolyte consisting of NaVO3 with a concentration of 8.54 g/L exhibits the best photocatalytic activity and about 93% of rhodamine is degraded after 14 h visible light radiation.