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51.
52.
Poly(N-vinyl carbazole) was sulfonated with different sulfonating agents and ion exchange capacities of the resins produced were evaluated. A maximum capacity of 4.5 meq · g?1 of dry resin was realized when sulfonation was done with 98.8% H2SO4 at 30°C for 10 h. The pH titration curves reveal the nature of a strong monofunctional cation exchanger with a pK value of 2.2. The resin exhibits a moderate rate of exchange with NaCl and is thermally stable up to ca. 250°C.  相似文献   
53.
A crosslinked polymer has been synthesized from the reaction of N-vinylcarbazole and formalin in toluene in the presence of dry HCl gas. The copolycondensate is insoluble in all common solvents for poly-N-vinylcarbazole, and exhibits higher thermal stability than the unmodified poly-N-vinylcarbazole. However, this polymer is less thermally stable than the corresponding furfural modified poly-N-vinylcarbazole. A mechanism for the overall reaction has been suggested and the factors affecting the synthesis have been discussed.  相似文献   
54.
Stripping of metal ions (i.e., Cs+ and Na+) in presence of ionophore such as dibenzo-18-crown-6, (DB18C6) from the ionic liquid phase to the aqueous nitric acid phase by molecular dynamics simulation is reported. The experimentally determined stripping percentages of Na+ (i.e., 43.4, 38.5, 34.4, and 31.9%) were found to be higher than the same for Cs+ (i.e., 32.6, 32.0, 31.3, and 30.2%). The nonbonded and the hydrogen bond energies between Na+ and water (i.e., −356.41 and −363.77 kcal/mol) were higher when compared with Cs+ (i.e., −212.43 and −221.04 kcal/mol). The spatial distribution functions further confirmed that the surfaces of Na+ were very closely distributed around the active sides of water whereas for Cs+, it was distributed very far from the water molecules. In the penultimate section, the effect of methanol to the aqueous phase was studied so as to enhance the extraction efficiency of the complex.  相似文献   
55.
The majority of research on water turbines focuses on design improvement of large-scale hydrokinetic turbines for power generation, which may have delayed the utilization of kinetic energy contained in rivers and canals. The aim of this paper is to improve the efficiency of a two bladed Savonius type cross-flow hydrokinetic turbine, which can be used as an energy converter to harness free-stream kinetic energy of water. An impinging jet duct design is presented for improving performance of the Savonius turbine in wind application as seen from literature. The performance of the modified turbine is evaluated using CFD software Fluent, and is compared with that of a simple two bladed Savonius water turbine and some of the prominent literature designs of the Savonius turbine. It is shown that the present design exhibits improved performance compared to the selected designs of the Savonius turbine.Further an insight of the improved performance of the modified turbine is also obtained from flow physics study.  相似文献   
56.
Shock recovered samples of a coarse grain (10 μm), high density (>99.9% theoretical) alumina from asymmetric impact tests conducted at 6.5 GPa (e.g. 3.2 times its Hugoniot Elastic Limit) in a single stage gas gun and characterized by X-ray diffractometry, scanning and field emission scanning electron microscopy, and transmission electron microscopy showed prolific presence of reduced crystallite size, higher average microstrain, grain localized micro/nano-scale deformations, micro-cleavages, grain-boundary microcracks, micro-wing crack formation, extensive shear induced deformations and fractures localized at grains, grain boundaries and triple grain junctions, grain localized entanglement of dislocations and their pile up impeded at grain boundaries. A new qualitative model based on micro-shear and micro-twist induced deformation and fracture in single and/or multiple planes in suitably oriented grain and/or grain assembly was developed to explain the experimentally observed damage evolution process.  相似文献   
57.
Bhattacharya S  Biswas J 《Nanoscale》2011,3(7):2924-2930
In this work, we have prepared Ag-nanorods using biscationic gemini surfactant micelles as the media by a seed-mediated wet synthesis method. Towards this end, we first synthesized Ag-nanoseeds of diameter ~7 nm stabilized by trisodium citrate (as the capping agent). Then these Ag-nanoseeds were used to synthesize Ag-nanorods of different aspect ratios. With decreasing Ag-nanoseed concentration, the aspect ratios of the Ag-nanorods stabilized by these gemini surfactants increased gradually. Various Ag-nanoseeds and Ag-nanospecies were characterized using UV-Vis spectroscopy (to know the surface plasmon bands), transmission electron microscopy (to find out their particle sizes and distribution), energy-dispersive X-ray spectroscopy and X-ray diffraction. When we used micelles derived from gemini surfactants of shorter spacer -(CH(2))(n)- (n = 2 or 4) to stabilize the Ag-nanorods, the λ(max) of the longitudinal band shifted more towards the blue region compared to that of the gemini surfactant micelles with a longer spacer -(CH(2))(n)- (n = 5, 12) at a given amount of the Ag-nanoseed solution. So, the growth of Ag-nanorods in the gemini micellar solutions depends on the spacer-chain length of gemini surfactants employed.  相似文献   
58.
59.
In this report, effect of enhanced rare earth (La2O3) concentration on substitution of TeO2 within ternary TeO2‐TiO2‐La2O3 (TTL) glass system has been studied with respect to its thermal, structural, mechanical, optical, and crystallization properties with an aim to achieve glass and glass‐ceramics having rare‐earth‐rich crystalline phase for nonlinear optical and infrared photonic applications. DSC analysis (10°C/min) demonstrates a progressive increase in glass‐transition temperature (Tg) from 359 to 452°C with the increase in La2O3 content. Continuous glass network modification with transformation of [TeO4] to [TeO3/TeO3+1] units is evidenced from Raman spectra which is corroborated with XPS studies. While mechanical properties demonstrate enhancement of cross‐linking density in the network. These glasses exhibit optical transmission window extended from 0.4 to 6 μm with calculated zero dispersion wavelength (λZDW) varying from 2.41 to 2.28 μm depending upon La2O3 content. Crystallization kinetics of TTL10 (80TeO2‐10TiO2‐10La2O3 in mol%) glass has been studied via established models. Activation energy (Ea) has been evaluated and dimensionality of crystal growth (m) suggests formation of surface crystals. Glass‐ceramic with crystalline phase of La2Te6O15 has been realized in heat‐treated TTL10 glass samples (at 450°C). As predicted from DSC analysis, FESEM study unveils the formation of surface crystallized glass‐ceramics.  相似文献   
60.
In order to develop zein fibers with improved physical properties and solvent resistance, formaldehyde was used as a crosslinking reagent before spinning. The crosslinking reaction was carried out in either acetic acid or ethanolic HCl where the amount of crosslinking reagent was between 1 and 6%. Reactions were carried out at various times and temperatures. When carried out in acetic acid, the maximum amount of formaldehyde that could be used was 1.5% as gelation occurred at higher levels. In ethanolic HCl, 6% formaldehyde could be incorporated into zein. All solutions were successfully electrospun, producing predominantly ribbon and round fibers; the morphology was strongly dependent on solvent and spinning solids. The formaldehyde‐crosslinked zein fabrics had double the tensile strength of control fabrics. SDS‐PAGE analysis clearly showed crosslinking had occurred. Electrospun fabrics from all formaldehyde‐treated zein solutions required an additional heating step in order to be resistant to dissolution in acetic acid, a known very good solvent for zein. Copyright © 2011 Society of Chemical Industry  相似文献   
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