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201.
Surface modification of carbon fiber for improving the interfacial adhesion between carbon fiber and polymer matrix 下载免费PDF全文
In this study, the reinforcing mechanism of amine functionalized on carbon fibers (CFs) has been precisely discussed, and the differences between aliphatic and aromatic compounds have been illustrated. Polyacrylonitrile‐based CFs were functionalized with ethylenediamine, 4,4‐diaminodiphenyl sulphone, and p‐aminobenzoic acid (PAB), and CF‐reinforced epoxy composites were prepared. The structural and surface characteristics of the functionalized CFs were investigated using X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT‐IR), and scanning electron microscopy (SEM). Mechanical properties in terms of tensile and flexural strengths and moduli were studied. The FT‐IR results confirm the success in bonding amines on the CF surface. After treatment of CFs, the oxygen and nitrogen contents as well as the N/C ratio showed an increase. XPS results provided evidence of the chemical reaction during functionalization, rather than being physically coated on the CF surface. Chemical modification of CF with diamines led to considerable enhancement in compatibility of CF filaments and epoxy resin, and remarkable improvements were seen in both tensile and flexural properties of the reinforced composites. SEM micrographs also confirmed the improvement of interface adhesion between the modified CFs and epoxy matrix. Finally, it can be concluded that PAB is a promising candidate to functionalize CF in order to improve interfacial properties of CF/epoxy composites. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
202.
A photographic technique coupled with image analysis was used to measure the size and fractal dimension of asphaltene aggregates formed in toluene-heptane solvent mixtures. First, asphaltene aggregates were examined in a Couette device and the fractal-like aggregate structures were quantified using boundary fractal dimension. The evolution of the floc structure with time was monitored. The relative rates of shear-induced aggregation and fragmentation/restructuring determine the steady-state floc structure. The average floc structure became more compact or more organized as the floc size distribution attained steady state. Moreover, the higher the shear rate is, the more compact the floc structure is at steady state. Second, the fractal dimensions of asphaltene aggregates were also determined in a free-settling test. The experimentally determined terminal settling velocities and characteristic lengths of the aggregates were utilized to estimate the 2D and 3D fractal dimensions. The size-density fractal dimension (D(3)) of the asphaltene aggregates was estimated to be in the range from 1.06 to 1.41. This relatively low fractal dimension suggests that the asphaltene aggregates are highly porous and very tenuous. The aggregates have a structure with extremely low space-filling capacity. 相似文献
203.
Hamid Reza Shaterian Razieh Doostmohammadi Majid Ghashang Mashaallah Rahmani 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):3127-3135
A mild, simple, novel, and highly efficient method for the rapid protection of various primary, secondary, tertiary aliphatic alcohols, aromatic alcohols, and oximes using hexamethyldisilazane (HMDS) in the presence of silica-supported sodium hydrogen sulfate (NaHSO 4 -SiO 2 ), as an active, inexpensive, nontoxic, heterogeneous, and readily available catalyst under ambient conditions is described. Timethylsilyl ethers were prepared in high to excellent yields, with short reaction times under mild and almost neutral reaction conditions at room temperature. 相似文献
204.
Ehsan Rahmani Ali Ahmadpour Mojtaba Zebarjad 《Journal of Sol-Gel Science and Technology》2012,63(1):65-71
Multilayer of TiO2 and TiO2:SiO2 thin films were grown on a glass substrate by sol?Cgel processes, followed by high temperature treatment at 500?°C. The fine grained TiO2 films controlled by SiO2 dopant showed very good wear resistance and endurance life. Energy dispersive X-ray spectroscopy was used to indicate the elements in the films. X-ray diffraction analyses indicated that TiO2 and TiO2:SiO2 film contain only anatase phase. The morphologies of the original and worn surfaces of the samples were analyzed by means of scanning tunneling microscope and scanning electron microscopy. The tribological properties of TiO2 and TiO2:SiO2 thin films sliding against AISI52100 steel pin were evaluated on a pin on disk friction and wear tester. The results showed that 25-layer TiO2:SiO2 films are superior in reducing friction and resisting wear compared with the glass substrate. 相似文献
205.
Gholam Reza Mahdavinia Javad Hasanpour Zeinab Rahmani Shiva Karami Hossein Etemadi 《Cellulose (London, England)》2013,20(5):2591-2604
Hydrogel nanocomposites were synthesized from grafting of acrylamide onto hydroxypropyl methylcellulose using methylenebisacrylamide crosslinker and sodium montmorillonite (Na-MMt) nanoclay. The effect of nanoclay content on the swelling of nanocomposites was investigated and an optimum swelling capacity was obtained at 12.7 wt% of Na-MMt. The effect of salt solutions on the swelling of nanocomposites revealed that the degree of swelling of samples depends only slightly on the salinity. The structure of nanocomposites was characterized by XRD, SEM, FTIR, and TEM techniques. The XRD and TEM results confirmed the exfoliation of Na-MMt nanoclay in nanocomposite matrix. The morphology of the nanocomposites was characterized by SEM technique and according to the results a loose surface was observed. The nanocomposite hydrogels were evaluated to remove cationic crystal violet dye from water. The investigation of the dye adsorption capacity and rate of nanocomposite hydrogels as a function of Na-MMt content revealed that the both adsorption capacity and rate is enhanced as the nanoclay content is increased in nanocomposite composition. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The best fit to the experimental data was obtained with the Langmuir model. 相似文献
206.