Documents disponibles écrits par cet auteur

Controlling the morphology of resorcinol−formaldehyde-based carbon xerogels by sol concentration, shearing, and surfactants / Chandra S. Sharma in Industrial & engineering chemistry research, Vol. 48 N° 17 (Septembre 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8030–8036 Titre : Controlling the morphology of resorcinol−formaldehyde-based carbon xerogels by sol concentration, shearing, and surfactants Type de document : texte imprimé Auteurs : Chandra S. Sharma, Auteur ; Devendra K. Upadhyay, Auteur ; Ashutosh Sharma, Auteur Année de publication : 2009 Article en page(s) : pp. 8030–8036 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Carbon  xerogel  microspheres  Formaldehyde  Nonionic  surfactants  Dilution  ratio  Hydrophilic−lipophilic  balance Résumé : Carbon xerogel microspheres were synthesized by inverse emulsion polymerization of resorcinol with formaldehyde, followed by pyrolysis at 900 °C under nitrogen atmosphere. We have studied the effect of various synthesis parameters, including dilution ratio and hydrophilic−lipophilic balance (HLB) of nonionic surfactants, on the size and morphology of resulting structures. The average particle size of carbon microspheres could be modulated from 1 to 28 μm by varying the dilution ratio over 3 orders of magnitude. Increase in the HLB value and the amount of surfactants produced a variety of dense carbon, but open-architecture fractal-like structures. Three different methods of stirring, namely, magnetic, mechanical, and ultrasonication were applied during the inverse emulsification to produce carbon xerogel microstructures. Formation of a wide spectrum of nonporous carbon particle morphologies, including the highly branched, hierarchical microparticles, by tuning the synthesis conditions may have potential applications in printing technology, controlled drug delivery, biosensors, and carbon-based microelectromechanical systems (C-MEMS) including bio-MEMS. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900359w [article] Controlling the morphology of resorcinol−formaldehyde-based carbon xerogels by sol concentration, shearing, and surfactants [texte imprimé] / Chandra S. Sharma, Auteur ; Devendra K. Upadhyay, Auteur ; Ashutosh Sharma, Auteur . - 2009 . - pp. 8030–8036. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8030–8036 Mots-clés : Carbon  xerogel  microspheres  Formaldehyde  Nonionic  surfactants  Dilution  ratio  Hydrophilic−lipophilic  balance Résumé : Carbon xerogel microspheres were synthesized by inverse emulsion polymerization of resorcinol with formaldehyde, followed by pyrolysis at 900 °C under nitrogen atmosphere. We have studied the effect of various synthesis parameters, including dilution ratio and hydrophilic−lipophilic balance (HLB) of nonionic surfactants, on the size and morphology of resulting structures. The average particle size of carbon microspheres could be modulated from 1 to 28 μm by varying the dilution ratio over 3 orders of magnitude. Increase in the HLB value and the amount of surfactants produced a variety of dense carbon, but open-architecture fractal-like structures. Three different methods of stirring, namely, magnetic, mechanical, and ultrasonication were applied during the inverse emulsification to produce carbon xerogel microstructures. Formation of a wide spectrum of nonporous carbon particle morphologies, including the highly branched, hierarchical microparticles, by tuning the synthesis conditions may have potential applications in printing technology, controlled drug delivery, biosensors, and carbon-based microelectromechanical systems (C-MEMS) including bio-MEMS. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie900359w

Photoresist derived electrospun carbon nanofibers with tunable morphology and surface properties / Chandra S. Sharma in Industrial & engineering chemistry research, Vol. 49 N° 6 (Mars 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 6 (Mars 2010) . - pp.2731–2739 Titre : Photoresist derived electrospun carbon nanofibers with tunable morphology and surface properties Type de document : texte imprimé Auteurs : Chandra S. Sharma, Auteur ; Rajesh Vasita, Auteur ; Devendra K. Upadhyay, Auteur Année de publication : 2010 Article en page(s) : pp.2731–2739 Note générale : Industrial Chemistry Langues : Anglais (eng) Mots-clés : Photoresist;  Derived;  Electrospun;  Carbon;  Nanofibers;  Tunable;  Morphology;  Surface;  Properties; Résumé : A new precursor, SU-8, which is a negative photoresist, was electrospun to produce ultrafine polymeric fibers with a wide range of morphology and wettability characteristics. Electrospun nanofibers of SU-8 were pyrolyzed at 1173 K in an inert atmosphere to give carbon nanofibers. A set of parameters, including electric potential, distance between source and collector, polymer flow rate, and polymer concentration, was optimized for high-viscosity SU-8 photoresist to synthesize long continuous carbon fibers having diameters in the range of 120−600 nm. However, for the same conditions, medium- and lower-viscosity SU-8 yielded beaded fibers and isolated beads, respectively. The wettability of the carbon web was significantly influenced by its surface morphology, as shown by water contact angle measurements. These SU-8-derived carbon nanostructures with tunable surface properties and morphologies could be especially suitable for integration with photoresist-based carbon-MEMS to produce multiscale hierarchal assemblies and could be of potential use in a broad range of applications. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901312j [article] Photoresist derived electrospun carbon nanofibers with tunable morphology and surface properties [texte imprimé] / Chandra S. Sharma, Auteur ; Rajesh Vasita, Auteur ; Devendra K. Upadhyay, Auteur . - 2010 . - pp.2731–2739. Industrial Chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 6 (Mars 2010) . - pp.2731–2739 Mots-clés : Photoresist;  Derived;  Electrospun;  Carbon;  Nanofibers;  Tunable;  Morphology;  Surface;  Properties; Résumé : A new precursor, SU-8, which is a negative photoresist, was electrospun to produce ultrafine polymeric fibers with a wide range of morphology and wettability characteristics. Electrospun nanofibers of SU-8 were pyrolyzed at 1173 K in an inert atmosphere to give carbon nanofibers. A set of parameters, including electric potential, distance between source and collector, polymer flow rate, and polymer concentration, was optimized for high-viscosity SU-8 photoresist to synthesize long continuous carbon fibers having diameters in the range of 120−600 nm. However, for the same conditions, medium- and lower-viscosity SU-8 yielded beaded fibers and isolated beads, respectively. The wettability of the carbon web was significantly influenced by its surface morphology, as shown by water contact angle measurements. These SU-8-derived carbon nanostructures with tunable surface properties and morphologies could be especially suitable for integration with photoresist-based carbon-MEMS to produce multiscale hierarchal assemblies and could be of potential use in a broad range of applications. Note de contenu : Bibiogr. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901312j