Documents disponibles écrits par cet auteur

Collective particle interactions in the sedimentation of charged colloidal suspensions / Jan Vesaratchanon in Industrial & engineering chemistry research, Vol. 48 N°1 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - p. 80-84 Titre : Collective particle interactions in the sedimentation of charged colloidal suspensions Type de document : texte imprimé Auteurs : Jan Vesaratchanon, Editeur scientifique ; Alex Nikolov, Editeur scientifique ; Darsh T. Wasan, Editeur scientifique Année de publication : 2009 Article en page(s) : p. 80-84 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Sedimentation  Monodisperse  colloidal  Microstructure  formation Résumé : The sedimentation of a similarly charged monodisperse colloidal suspension was studied to investigate the role of collective particle interactions affecting the rate of sedimentation and thereby the stability. The particle concentration profiles, microstructure formation, and the sedimentation rates were determined using a nondestructive back-light scattering technique. Stochastic particle dynamics simulations using the Beresford-Smith and Derjaguin−Landau−Verwey−Overbeek repulsive pair potentials were carried out to predict the sedimentation rates. In addition, Monte Carlo simulations were performed to reveal the particle microstructure formation. The collective particle interactions result in an oscillatory effective potential of interaction between the identically charged particles, even though the pair potential is repulsive, and lead to a more ordered microstructure formation and reduction in the sedimentation rate. The theoretical predictions, which were in good agreement with the experimental measurements, clearly showed the importance of the collective particle interaction effect in stabilizing the monodisperse suspension. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8004176 [article] Collective particle interactions in the sedimentation of charged colloidal suspensions [texte imprimé] / Jan Vesaratchanon, Editeur scientifique ; Alex Nikolov, Editeur scientifique ; Darsh T. Wasan, Editeur scientifique . - 2009 . - p. 80-84. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - p. 80-84 Mots-clés : Sedimentation  Monodisperse  colloidal  Microstructure  formation Résumé : The sedimentation of a similarly charged monodisperse colloidal suspension was studied to investigate the role of collective particle interactions affecting the rate of sedimentation and thereby the stability. The particle concentration profiles, microstructure formation, and the sedimentation rates were determined using a nondestructive back-light scattering technique. Stochastic particle dynamics simulations using the Beresford-Smith and Derjaguin−Landau−Verwey−Overbeek repulsive pair potentials were carried out to predict the sedimentation rates. In addition, Monte Carlo simulations were performed to reveal the particle microstructure formation. The collective particle interactions result in an oscillatory effective potential of interaction between the identically charged particles, even though the pair potential is repulsive, and lead to a more ordered microstructure formation and reduction in the sedimentation rate. The theoretical predictions, which were in good agreement with the experimental measurements, clearly showed the importance of the collective particle interaction effect in stabilizing the monodisperse suspension. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8004176

Emulsion stability in the presence of nonionic surfactant micelles / Youngsun Kong in Industrial & engineering chemistry research, Vol. 49 N° 11 (Juin 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5299–5303 Titre : Emulsion stability in the presence of nonionic surfactant micelles : role of micellar ordering and ostwald ripening Type de document : texte imprimé Auteurs : Youngsun Kong, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur Année de publication : 2010 Article en page(s) : pp. 5299–5303 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Emulsion  Micellar  Ordering Résumé : The phenomenon of surfactant micelle ordering (i.e., stratification) in emulsion films was investigated using the reflected-light microinterferometric technique. In thinning films formed from a nonionic micellar solution of ethoxylated alcohol (1 wt %), it was found that the small droplets (i.e., less than 5 µm) are separated by thick (>0.1 µm) stable films containing surfactant micelles in multilayers that prevent droplet flocculation and coalescence. The Ostwald ripening process governs emulsion stability over a long-term. The direct microscopic observations of the evolution of the drop size distribution over time of hexadecane drops (25 vol %) dispersed in an aqueous micellar solution (≈ 120 times critical micellar concentration) was compared with that calculated from the Ostwald ripening model. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901825c [article] Emulsion stability in the presence of nonionic surfactant micelles : role of micellar ordering and ostwald ripening [texte imprimé] / Youngsun Kong, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur . - 2010 . - pp. 5299–5303. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 11 (Juin 2010) . - pp. 5299–5303 Mots-clés : Emulsion  Micellar  Ordering Résumé : The phenomenon of surfactant micelle ordering (i.e., stratification) in emulsion films was investigated using the reflected-light microinterferometric technique. In thinning films formed from a nonionic micellar solution of ethoxylated alcohol (1 wt %), it was found that the small droplets (i.e., less than 5 µm) are separated by thick (>0.1 µm) stable films containing surfactant micelles in multilayers that prevent droplet flocculation and coalescence. The Ostwald ripening process governs emulsion stability over a long-term. The direct microscopic observations of the evolution of the drop size distribution over time of hexadecane drops (25 vol %) dispersed in an aqueous micellar solution (≈ 120 times critical micellar concentration) was compared with that calculated from the Ostwald ripening model. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901825c

Emulsion texture and stability / Youngsun Kong in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9108–9114 Titre : Emulsion texture and stability : role of surfactant micellar interactions in the presence of proteins Type de document : texte imprimé Auteurs : Youngsun Kong, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur Année de publication : 2009 Article en page(s) : p. 9108–9114 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Texture  and  Stability  Role  of  Surfactant  Micellar  Presence  of  Proteins Résumé : This article presents the results of our recent research on the texture and stability of oil-in-water emulsions containing sucrose ester and proteins. We used both the direct microscopic imaging and nondestructive back-light scattering (Kossel diffraction) techniques to evaluate the emulsion texture and the energy barrier between droplets for two different emulsifier compositions with and without the proteins present. The microinterferometric method employing our capillary force balance was used to study the stability of the confined thin film (containing surfactant micelles and proteins) between two droplets. In addition to the film stability, we also measured the second virial coefficient of the micellar solutions with and without protein and assessed the intermicellar interaction and related it to the stabilities of the emulsions prepared using two different emulsifier compositions. The effect of protein on the oil-in-water emulsion stability was also assessed and was found to lead to the depletion attraction between droplets, resulting in a less stable emulsion. The results offer new insight into the understanding of how the micellar interactions in the presence of proteins affect emulsion texture and stability. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8001815 [article] Emulsion texture and stability : role of surfactant micellar interactions in the presence of proteins [texte imprimé] / Youngsun Kong, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur . - 2009 . - p. 9108–9114. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9108–9114 Mots-clés : Texture  and  Stability  Role  of  Surfactant  Micellar  Presence  of  Proteins Résumé : This article presents the results of our recent research on the texture and stability of oil-in-water emulsions containing sucrose ester and proteins. We used both the direct microscopic imaging and nondestructive back-light scattering (Kossel diffraction) techniques to evaluate the emulsion texture and the energy barrier between droplets for two different emulsifier compositions with and without the proteins present. The microinterferometric method employing our capillary force balance was used to study the stability of the confined thin film (containing surfactant micelles and proteins) between two droplets. In addition to the film stability, we also measured the second virial coefficient of the micellar solutions with and without protein and assessed the intermicellar interaction and related it to the stabilities of the emulsions prepared using two different emulsifier compositions. The effect of protein on the oil-in-water emulsion stability was also assessed and was found to lead to the depletion attraction between droplets, resulting in a less stable emulsion. The results offer new insight into the understanding of how the micellar interactions in the presence of proteins affect emulsion texture and stability. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8001815

Foamability of liquid particle suspensions / Krishna Vijayaraghavan 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. 8180–8185 Titre : Foamability of liquid particle suspensions : a modeling study Type de document : texte imprimé Auteurs : Krishna Vijayaraghavan, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur Année de publication : 2009 Article en page(s) : pp. 8180–8185 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Liquid  particle  suspensions  Foamability  Monte  Carlo  simulations  Integral  equations Résumé : Recent experiments on the foamability of liquid particle suspensions (with a particle size varying from nanometers to micrometers in diameter and in the absence of any surfactants) have shown that the foamability correlates well with the degree of particle coverage at the air−liquid surface. Furthermore, these experiments have also revealed foam inhibition due to the aggregation or clustering of particles in the bulk at high particle concentrations. The present study is aimed at theoretically modeling the observed phenomena. Theoretical analyses based on Monte Carlo simulations and the integral equations of statistical mechanics are used to model the particle aggregation phenomena in the bulk. The radial distribution functions, which show the particle packing density, are analyzed to obtain the effective energy of interaction between the particles. The maximum in foaminess due to the adsorption of particles on the air−liquid surface and clustering of particles in the bulk is explained. The modeling results are in good agreement with the experimental observations on foaminess with small particles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801741q [article] Foamability of liquid particle suspensions : a modeling study [texte imprimé] / Krishna Vijayaraghavan, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur . - 2009 . - pp. 8180–8185. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 17 (Septembre 2009) . - pp. 8180–8185 Mots-clés : Liquid  particle  suspensions  Foamability  Monte  Carlo  simulations  Integral  equations Résumé : Recent experiments on the foamability of liquid particle suspensions (with a particle size varying from nanometers to micrometers in diameter and in the absence of any surfactants) have shown that the foamability correlates well with the degree of particle coverage at the air−liquid surface. Furthermore, these experiments have also revealed foam inhibition due to the aggregation or clustering of particles in the bulk at high particle concentrations. The present study is aimed at theoretically modeling the observed phenomena. Theoretical analyses based on Monte Carlo simulations and the integral equations of statistical mechanics are used to model the particle aggregation phenomena in the bulk. The radial distribution functions, which show the particle packing density, are analyzed to obtain the effective energy of interaction between the particles. The maximum in foaminess due to the adsorption of particles on the air−liquid surface and clustering of particles in the bulk is explained. The modeling results are in good agreement with the experimental observations on foaminess with small particles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801741q

The importance of oscillatory structural forces in the sedimentation of a binary hard-sphere colloidal suspension / Jan Sudaporn Vesaratchanon in Industrial & engineering chemistry research, Vol. 48 N° 14 (Juillet 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N° 14 (Juillet 2009) . - pp. 6641–6651 Titre : The importance of oscillatory structural forces in the sedimentation of a binary hard-sphere colloidal suspension Type de document : texte imprimé Auteurs : Jan Sudaporn Vesaratchanon, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur Année de publication : 2009 Article en page(s) : pp. 6641–6651 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Colloidal  dispersions  Hard-sphere  suspension  Oscillatory  structural  forces  Monte  Carlo  simulations  Stochastic  particle  dynamics  methods  Sedimentation  experiments Résumé : Concentrated colloidal dispersions are complex systems comprised of colloidal particles of various sizes. This paper summarizes recent experimental and theoretical findings on understanding the interactions between microspheres in the presence of submicrometer particles; the submicrometer particles can be solvent molecules, surfactant micelles, or other nanometer-sized particles. In a hard-sphere suspension containing microspheres in the presence of submicrometer particles, oscillatory structural (entropic) forces between large particles, caused by small particles, arise as a result of the collective particle−particle interactions. The magnitude of the oscillatory structural forces is theoretically estimated based on the statistical mechanics approach, Monte Carlo simulations, and stochastic particle dynamics methods. Also, sedimentation experiments using spherical low-charged, binary hard-sphere particle suspensions with a large size ratio are presented to elucidate the importance of the oscillatory structural forces (i.e., attractive depletion and repulsive structural forces) in particle dispersion stability. Micronmeter-sized, low-charge latex particle concentration profiles in the presence of nanoparticles (nonionic micelles) were monitored using a nondestructive Kossel diffraction technique. To rationalize the experimental observations, the particle settling dynamics were simulated by considering the hydrodynamic interactions, structural forces, and Brownian motion in a gravity field. The theoretical predictions were determined to be in satisfactory agreement with the experimental observations. The effect of the particle size ratio (i.e., micrometer to submicrometer) on interparticle interaction energy is highlighted. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8019856 [article] The importance of oscillatory structural forces in the sedimentation of a binary hard-sphere colloidal suspension [texte imprimé] / Jan Sudaporn Vesaratchanon, Auteur ; Alex Nikolov, Auteur ; Darsh Wasan, Auteur . - 2009 . - pp. 6641–6651. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N° 14 (Juillet 2009) . - pp. 6641–6651 Mots-clés : Colloidal  dispersions  Hard-sphere  suspension  Oscillatory  structural  forces  Monte  Carlo  simulations  Stochastic  particle  dynamics  methods  Sedimentation  experiments Résumé : Concentrated colloidal dispersions are complex systems comprised of colloidal particles of various sizes. This paper summarizes recent experimental and theoretical findings on understanding the interactions between microspheres in the presence of submicrometer particles; the submicrometer particles can be solvent molecules, surfactant micelles, or other nanometer-sized particles. In a hard-sphere suspension containing microspheres in the presence of submicrometer particles, oscillatory structural (entropic) forces between large particles, caused by small particles, arise as a result of the collective particle−particle interactions. The magnitude of the oscillatory structural forces is theoretically estimated based on the statistical mechanics approach, Monte Carlo simulations, and stochastic particle dynamics methods. Also, sedimentation experiments using spherical low-charged, binary hard-sphere particle suspensions with a large size ratio are presented to elucidate the importance of the oscillatory structural forces (i.e., attractive depletion and repulsive structural forces) in particle dispersion stability. Micronmeter-sized, low-charge latex particle concentration profiles in the presence of nanoparticles (nonionic micelles) were monitored using a nondestructive Kossel diffraction technique. To rationalize the experimental observations, the particle settling dynamics were simulated by considering the hydrodynamic interactions, structural forces, and Brownian motion in a gravity field. The theoretical predictions were determined to be in satisfactory agreement with the experimental observations. The effect of the particle size ratio (i.e., micrometer to submicrometer) on interparticle interaction energy is highlighted. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8019856