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Control of surface defects and agglomeration mechanism of layered double hydroxide nanoparticles / Yongshan Zhou in Industrial & engineering chemistry research, Vol. 51 N° 11 (Mars 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 11 (Mars 2012) . - pp. 4215–4221 Titre : Control of surface defects and agglomeration mechanism of layered double hydroxide nanoparticles Type de document : texte imprimé Auteurs : Yongshan Zhou, Auteur ; Xiaoming Sun, Auteur ; Kai Zhong, Auteur Année de publication : 2012 Article en page(s) : pp. 4215–4221 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Hydroxide  Nanoparticles Résumé : Agglomeration is a common problem in the production and application of nanoparticles. The degree of agglomeration of layered double hydroxide (LDH) nanoparticles is difficult to control in its industrial production. The properties of industrial scale MgAl–CO3–LDH products obtained using an aging reactor composed of a 1 m3 kettle with a water cooling jacket have been compared with MgAl–CO3–LDHs prepared using different aging times in a model laboratory scale reactor [a 500 mL flask]. The effect of varying aging times on the agglomeration of the LDH nanoparticles has been studied experimentally. The crystallinity, surface defects, and surface zeta potential of the LDHs have been studied in an effort to understand the mechanism of agglomeration of the nanoparticles. The results show that in poorly crystalline LDHs, accumulation of Al3+ cations at different points in the layers results in an increase in local charge density. Consequently, the zeta potential and the electrostatic repulsion between particles decrease, resulting in serious agglomeration of LDH nanoparticles. In contrast, for LDHs with higher crystallinity produced with extended aging times, the layer cations become uniformly distributed resulting in an increase in zeta potential and increased electrostatic repulsion between the particles. As a result, the degree of agglomeration is reduced. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202302n [article] Control of surface defects and agglomeration mechanism of layered double hydroxide nanoparticles [texte imprimé] / Yongshan Zhou, Auteur ; Xiaoming Sun, Auteur ; Kai Zhong, Auteur . - 2012 . - pp. 4215–4221. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 11 (Mars 2012) . - pp. 4215–4221 Mots-clés : Hydroxide  Nanoparticles Résumé : Agglomeration is a common problem in the production and application of nanoparticles. The degree of agglomeration of layered double hydroxide (LDH) nanoparticles is difficult to control in its industrial production. The properties of industrial scale MgAl–CO3–LDH products obtained using an aging reactor composed of a 1 m3 kettle with a water cooling jacket have been compared with MgAl–CO3–LDHs prepared using different aging times in a model laboratory scale reactor [a 500 mL flask]. The effect of varying aging times on the agglomeration of the LDH nanoparticles has been studied experimentally. The crystallinity, surface defects, and surface zeta potential of the LDHs have been studied in an effort to understand the mechanism of agglomeration of the nanoparticles. The results show that in poorly crystalline LDHs, accumulation of Al3+ cations at different points in the layers results in an increase in local charge density. Consequently, the zeta potential and the electrostatic repulsion between particles decrease, resulting in serious agglomeration of LDH nanoparticles. In contrast, for LDHs with higher crystallinity produced with extended aging times, the layer cations become uniformly distributed resulting in an increase in zeta potential and increased electrostatic repulsion between the particles. As a result, the degree of agglomeration is reduced. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie202302n

Preparation of highly dispersed nano-La2O3 particles using modified carbon black as an agglomeration inhibitor / Guirong Wang in Industrial & engineering chemistry research, Vol. 51 N° 45 (Novembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 45 (Novembre 2012) . - pp. 14692-14699 Titre : Preparation of highly dispersed nano-La2O3 particles using modified carbon black as an agglomeration inhibitor Type de document : texte imprimé Auteurs : Guirong Wang, Auteur ; Yongshan Zhou, Auteur ; David G. Evans, Auteur Année de publication : 2013 Article en page(s) : pp. 14692-14699 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Agglomeration  Carbon  black  Preparation Résumé : Nanoparticles readily agglomerate, especially during nucleation, growth, and calcination processes. In this work, modified carbon black (MCB) has been used to prevent particle agglomeration during the nucleation step in the preparation of a highly dispersed nano-La(OH), precursor by a coprecipitation reaction. The surface carboxyl groups formed on MCB after modification can adsorb and fix positively charged La3+ ions on the surface. Therefore, nano-La(OH)3 nuclei can be uniformly deposited on the MCB surface. After nucleation, La(OH)3 particles with a size of about 20 nm with a positive surface charge still interact strongly with the negatively charged MCB surface, which effectively prevents their agglomeration during the subsequent aging process. Furthermore, due to the release of CO2 over a wide temperature range from 400 to 700 °C during a subsequent calcination process, La2O3 particles obtained by calcination of the La(OH)3 precursor can be effectively isolated at high temperature and prevented from agglomerating. By using MCB as an agglomeration inhibitor in this way, highly dispersed La2O3 nanoparticles with a size of 50 nm having excellent photoluminescence ability can be prepared. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26620382 [article] Preparation of highly dispersed nano-La2O3 particles using modified carbon black as an agglomeration inhibitor [texte imprimé] / Guirong Wang, Auteur ; Yongshan Zhou, Auteur ; David G. Evans, Auteur . - 2013 . - pp. 14692-14699. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 45 (Novembre 2012) . - pp. 14692-14699 Mots-clés : Agglomeration  Carbon  black  Preparation Résumé : Nanoparticles readily agglomerate, especially during nucleation, growth, and calcination processes. In this work, modified carbon black (MCB) has been used to prevent particle agglomeration during the nucleation step in the preparation of a highly dispersed nano-La(OH), precursor by a coprecipitation reaction. The surface carboxyl groups formed on MCB after modification can adsorb and fix positively charged La3+ ions on the surface. Therefore, nano-La(OH)3 nuclei can be uniformly deposited on the MCB surface. After nucleation, La(OH)3 particles with a size of about 20 nm with a positive surface charge still interact strongly with the negatively charged MCB surface, which effectively prevents their agglomeration during the subsequent aging process. Furthermore, due to the release of CO2 over a wide temperature range from 400 to 700 °C during a subsequent calcination process, La2O3 particles obtained by calcination of the La(OH)3 precursor can be effectively isolated at high temperature and prevented from agglomerating. By using MCB as an agglomeration inhibitor in this way, highly dispersed La2O3 nanoparticles with a size of 50 nm having excellent photoluminescence ability can be prepared. ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=26620382