RESUMO
Disperse Multiwall carbon nanotubes (MWCNTs) are incorporated aqueous N-hydroxy methyl acrylamide, which is subjected to crosslinking to develop a transparent conductive composite free standing film. The effects of the concentration of MWCNTs and temperature on optical and electrical properties of nano-composites are investigated. Interestingly, only 0.06 mg/ml of MWCNTs is sufficient to reach the percolation threshold (Phi) for transition in electrical conductivity up to 10(-4) S/cm, with a visible transmittance over 85%, which is well above the reported for such a low level of MWCNTs loading. The electrical conductivity of the composite was measured at 120 degrees C. It has been observed that electrical conductivity increases significantly with the increase in temperature, signifying the semiconducting nature of nano-composites. Finally, current-voltage (I-V) characteristics show liner behaviour, confirms Ohmic nature of nano-composites and metal contact.
RESUMO
The electrokinetic and adsorption characteristics of alumina suspensions in the presence of Darvan C as dispersant have been investigated. The interaction of Darvan C with alumina has been interpreted in terms of electrokinetic and adsorption measurements. The adsorption density of Darvan C increases greatly with decreasing pH. The isoelectric point (iep) of the sample under investigation is found to be located at pH 9.1. For pH values near and below the point of zero charge, there is an added electrostatic attractive potential for adsorption, which results in high-affinity adsorption behavior. Possible mechanisms of interaction between alumina and Darvan C are described and discussed.
RESUMO
Additive interactions and their effects on electrokinetic properties of colloidal alumina suspension are presented in this study. Dibasic ammonium citrate (DAC), natural egg albumin, and octanol-2 are chosen as additives. The surface charge behavior of a 5% (w/v) colloidal alumina suspension in the presence of these additives has been studied in detail. The optimum dosage of DAC to have a stable suspension is found to be 3 mg/g of alumina whereas it is 105 and 164 mg/g of alumina for albumin and octanol-2, respectively. Albumin was found to be a better dispersant than DAC and interacts more strongly than DAC with the surface of alumina, while octanol-2 shows physisorbing characteristics. Turbidity measurements indicate that albumin and DAC interact. When the DAC : albumin molar ratio exceeds 10, the turbidity of the solution is higher than the turbidity of pure albumin, indicating the formation of complexes.
Assuntos
Óxido de Alumínio/química , Albuminas/química , Ácido Cítrico/análogos & derivados , Ácido Cítrico/química , Coloides/química , Eletroquímica , Concentração de Íons de Hidrogênio , Cinética , Nefelometria e Turbidimetria , Octanóis/química , Compostos de Amônio Quaternário/química , Suspensões/química , TermodinâmicaRESUMO
A facile and green approach for the synthesis of highly electroactive branched Pt nanostructures well dispersed on graphene has been developed by in situ reduction of graphene oxides and Pt(iv) ions in an aqueous medium. The as-synthesized branched Pt and graphene hybrid nanomaterials (GR-BPtNs) were thoroughly characterized using Transmission Electron Microscope (TEM), UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and Raman spectroscopy. This report clearly exploits the decisive role of the graphene support, the pH of the solution and the stabiliser on shaping the branched morphology of the Pt nanostructures well dispersed on graphene. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS) measurements were employed to investigate the electrocatalytic performance and durability of GR-BPtNs towards methanol oxidation and oxygen reduction. The results reveal that the synergetic effect of the graphene support and the branched morphology triggers electrocatalytic performance and robust tolerance to surface poisoning of GR-BPtNs.