Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90-100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.ope

Aminofunctionalized acrylamide-maleic acid hydrogels: Adsorption of indigo carmine

Aminofunctionalized acrylamide-maleic acid hydrogels having both amine and acid groups were prepared by transamidation reaction of acrylamide-maleic acid (AAM-MA) hydrogels using ethylenediamine in non-aqueous media. Modified polymers were characterized by determination of amine value (AV), carboxylic acid group content (AGC) and FTIR spectra. The modified hydrogels obtained have the amine value of 2.81 mmol/g. Their swelling properties were changed depending upon the pH value of external medium. The modified hydrogels were used as a new sorbent for removal of indigo carmine from aqueous solution. The effects of pH, time, NaCl concentration and initial dye concentration on the adsorption capacity were investigated. Almost 70-80% of capacity was saturated within approximately 30 min and quite high adsorption capacity was observed. The adsorption capacity increased at acidic pH and also in presence of NaCl in dye solution. The adsorption isotherm models were applied to the experimental data and it was seen that the Langmuir isotherm model was the best fit for these modified AAM-MA hydrogels-indigo carmine system. (c) 2005 Elsevier B.V. All rights reserved

Modified polyacrylamide hydrogels and their application in removal of heavy metal ions

Modified crosslinked polyacrylamides having different functional groups were prepared by Mannich reaction using different an-tine compounds such as ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA) and sulfomethylation reaction. Products were characterized by determination of their basic group content (BGC), hydroxymethyl group content (HMG), equilibrium degree of swelling (EDS) and FT-IR spectra. For Mannich reactions. BGC and EDS changed with a-mount of employed an-line compounds, reaction time and temperature. Sulfomethylation reactions gave products with high BGC and very high EDS. FT-IR spectroscopic analysis confirmed that a parallel hydrolysis reaction occurred along with the expected modification reactions. The products were used for removal of Cu(II), Cd(II) and Pb(II) ion under competitive and non-competitive conditions at different pH. The metal ion removal capacities changed depending their BGC and EDS. While the Mannich products were selective towards Cu(U) ion, the sulfomethylation products were highly selective to Pb(II) ions. The polymers were used several times by regeneration without loss of adsorption capacity and changing of selectivity properties. (C) 2003 Elsevier Science Ltd. All rights reserved

Preparation of modified polyacrylamide hydrogels and application in removal of Cu(II) ion

Modified polyacrylamide hydrogels were prepared by transamidation and Hofmann reactions using different amine compounds. Products were characterized by their amine value (AV), equilibrium degree of swelling (EDS) and FT-IR spectroscopy. In case of transamidation on crosslinked polyacrylamide (CPAAm) in aqueous media, AV increased with reaction time and temperature, but EDS decreased with time, especially for reactions at higher temperatures. On the other hand, transamidation reactions on linear polyacrylamide (LPAAm) gave products with higher AV, but quite lower EDS than aqueous media products. Hofmann reactions were carried out on CPAAm with different amounts of NaOCl in the presence of amine compounds, to yield products with higher AV and EDS compared with conventional Hofmann reactions. The products were used for removal of copper (II) ion at pH = 5.5 by batch equilibrium technique. A maximum removal capacity of 2.93 mmol Cu(II)/g was obtained after a regeneration cycle. (C) 2001 Elsevier Science Ltd. All rights reserved

A new study on spin-on-silica for multilevel interconnect applications

In this study, a new method for low temperature oxide deposition is discussed. Silicon dioxide was formed on silicon from silicic acid solution by using spin-on technology. Mechanical and planarizing properties of the silicon dioxide were investigated. Using this oxide a metal-silicon dioxide-wafer (MOS) structure was manufactured. Breakdown field strength and trap density of the MOS capacitance was measured. The method discussed in this paper shows a very low carbon contamination risk and does not suffer from crack formation. It is therefore suitable for a Variety of applications in VLSI and ULSI fabrication, which require low process temperatures or where high temperatures have drawbacks. (C) 1999 Elsevier Science Ltd. All rights reserved

Effects of various polyolefin copolymers on the interfacial interaction, microstructure and physical properties of cyclic olefin copolymer(COC)/graphite composites

In this study, effects of various types of functional polyolefin copolymers (FPOCs), poly(isobutylene-alt-maleic anhydride), poly(maleic anhydride-alt-1-octadecene) and poly(ethylene-graft-maleic anhydride), on the microstructure formation, interfacial interaction and physical properties of cyclic olefin copolymer (COC)/graphite composites were investigated. The COC/graphite composites were prepared in a lab. scale twin screw extruder. Microstructural features of samples were studied in a field emission scanning electron microscopy (FESEM). Viscoelastic properties of samples, obtained from the rheology tests in melt state and the dynamic mechanical analysis in solid state were used to quantify interfacial interactions between the COC and graphite depending on the types of FPOC. The average aspect ratio (A(f)) values of graphite flakes in the COC phase were determined about 40-65 by SEM observation and image analysis study on the samples prepared with different types of FPOC. Based on the gas permeability measurements, tortuous diffusion model suggested that the A(f) values of graphite flakes varied between 40 and 80 depending on the amount of graphite. It was shown that the poly(isobutylene-alt-maleic anhydride) copolymer provided relatively higher interfacial interaction between the COC and graphite flakes than the other FPOCs