Documents disponibles écrits par cet auteur

Cryogels / Ashok Kumar in Materials today, Vol. 13 N° 11 (Novembre 2010) 

Public ISBD [article]  in Materials today > Vol. 13 N° 11 (Novembre 2010) . - pp. 42-44 Titre : Cryogels : freezing unveiled by thawing Type de document : texte imprimé Auteurs : Ashok Kumar, Auteur ; Ruchi Mishra, Auteur ; Yvonne Reinwald, Auteur Année de publication : 2011 Article en page(s) : pp. 42-44 Note générale : Ingénierie Langues : Anglais (eng) Mots-clés : Cryogels  Ice-crystal  formation  Polymerization  Gel  materials Index. décimale : 620 Essais des matériaux. Matériaux commerciaux. Station génératrice d'énergie. Economie de l'énergie Résumé : Cryogels are interconnected supermacroporous gels prepared at sub-zero temperatures having applications in various research fields. The process of cryogelation is ideally thought to take place via following steps: phase separation with ice-crystal formation, cross-linking and polymerization followed by thawing of ice-crystals to form an interconnected porous cryogel network. This phenomenon mostly thought as a theoretical concept has now been revealed here in practical terms via data generated by micro-computed tomography (Micro CT). Micro CT is mainly used for characterizing the gel materials in terms of their physical properties like pore size, porosity, strut size, etc., whereas this work has pioneered its role in elucidating the process of cryogel formation. DEWEY : 620 ISSN : 1369-7021 En ligne : http://www.sciencedirect.com/science/article/pii/S1369702110702029 [article] Cryogels : freezing unveiled by thawing [texte imprimé] / Ashok Kumar, Auteur ; Ruchi Mishra, Auteur ; Yvonne Reinwald, Auteur . - 2011 . - pp. 42-44. Ingénierie Langues : Anglais (eng) in Materials today > Vol. 13 N° 11 (Novembre 2010) . - pp. 42-44 Mots-clés : Cryogels  Ice-crystal  formation  Polymerization  Gel  materials Index. décimale : 620 Essais des matériaux. Matériaux commerciaux. Station génératrice d'énergie. Economie de l'énergie Résumé : Cryogels are interconnected supermacroporous gels prepared at sub-zero temperatures having applications in various research fields. The process of cryogelation is ideally thought to take place via following steps: phase separation with ice-crystal formation, cross-linking and polymerization followed by thawing of ice-crystals to form an interconnected porous cryogel network. This phenomenon mostly thought as a theoretical concept has now been revealed here in practical terms via data generated by micro-computed tomography (Micro CT). Micro CT is mainly used for characterizing the gel materials in terms of their physical properties like pore size, porosity, strut size, etc., whereas this work has pioneered its role in elucidating the process of cryogel formation. DEWEY : 620 ISSN : 1369-7021 En ligne : http://www.sciencedirect.com/science/article/pii/S1369702110702029

Estimation of Effective diffusivity of stored NOx in the barium phase of Pt / BaO / Al2O3 catalysts using TAP / Ashok Kumar in Industrial & engineering chemistry research, Vol. 49 N° 21 (Novembre 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10334-10340 Titre : Estimation of Effective diffusivity of stored NOx in the barium phase of Pt / BaO / Al2O3 catalysts using TAP Type de document : texte imprimé Auteurs : Ashok Kumar, Auteur ; Michael P. Harold, Auteur ; Vemuri Balakotaiah, Auteur Année de publication : 2011 Article en page(s) : pp. 10334-10340 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Catalyst  Diffusion  coefficient Résumé : A systematic study over Pt/BaO/Al2O3 powder catalyst is carried out using Temporal Analysis of Products (TAP) to estimate the effective diffusivity of stored NO, in the barium phase. The prenitration of PtBaO/ Al2O3 using sequential pulses of NO, followed by reduction with H2 results in the evolution of N2 and NH3. The reduction is carried out in the NOx transport limited regime in which diffusion of the stored NO, from BaO storage phase to Pt/BaO interface was determined to be the rate controlling process. The effluent profiles of N containing species (2N2 + NH3) were used to estimate stored NO, diffusivity in barium phase and the apparent activation energy. The activation energy (74-81 kJ/mol) is in good agreement with the estimated value of 75 kJ/mol from a recent NO, trap modeling study.1. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447924 [article] Estimation of Effective diffusivity of stored NOx in the barium phase of Pt / BaO / Al2O3 catalysts using TAP [texte imprimé] / Ashok Kumar, Auteur ; Michael P. Harold, Auteur ; Vemuri Balakotaiah, Auteur . - 2011 . - pp. 10334-10340. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 21 (Novembre 2010) . - pp. 10334-10340 Mots-clés : Catalyst  Diffusion  coefficient Résumé : A systematic study over Pt/BaO/Al2O3 powder catalyst is carried out using Temporal Analysis of Products (TAP) to estimate the effective diffusivity of stored NO, in the barium phase. The prenitration of PtBaO/ Al2O3 using sequential pulses of NO, followed by reduction with H2 results in the evolution of N2 and NH3. The reduction is carried out in the NOx transport limited regime in which diffusion of the stored NO, from BaO storage phase to Pt/BaO interface was determined to be the rate controlling process. The effluent profiles of N containing species (2N2 + NH3) were used to estimate stored NO, diffusivity in barium phase and the apparent activation energy. The activation energy (74-81 kJ/mol) is in good agreement with the estimated value of 75 kJ/mol from a recent NO, trap modeling study.1. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=23447924