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Thermal dehydration and vibrational spectra of hydrated sodium metaborates / Amy M. Beaird in Industrial & engineering chemistry research, Vol. 50 N° 13 (Juillet 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7746–7752 Titre : Thermal dehydration and vibrational spectra of hydrated sodium metaborates Type de document : texte imprimé Auteurs : Amy M. Beaird, Auteur ; Li Peng, Auteur ; Hilary S. Marsh, Auteur Année de publication : 2011 Article en page(s) : pp. 7746–7752 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Catalysis  Reaction  kinetics  Inorganic  reaction  mechanisms Résumé : Sodium metaborate hydrates are a class of compounds represented by the stoichiometry NaBO2·xH2O. Recently, sodium metaborate has received attention as the byproduct of sodium borohydride hydrolysis, a reaction that is under consideration for hydrogen storage applications. The aim of this work was to understand the disposition of water in the crystal structure of hydrated sodium metaborates and to characterize the thermal stability and dehydration of the various hydrated species to optimize hydrogen storage efficiency as well as recyclability of the borate. Observations from a suite of analytical techniques including thermal analyses (thermogravimetric analysis/differential scanning calorimetry), X-ray diffraction, and Raman spectroscopy were correlated to characterize the dehydration mechanism of commercially available sodium metaborates, with an emphasis on the dihydrate (x = 2). A transformation from tetrahedrally coordinated boron to trigonal boron occurs when NaB(OH)4 (x = 2) is heated between 25 and 400 °C. The first dehydration to Na3[B3O5(OH)2] (x = 1/3) releases 5 mol of water between 83 and 155 °C. The final mole of water is released between 249 and 280 °C, and Na3B3O6 (x = 0) is formed. Raman spectra are reported for x = 2 and 1/3 for the first time. First-principles density functional theory was used to compute Raman spectra of the x = 1/3 and 2 material in order to assign the modes. We found reasonably good agreement between the experimentally measured and calculated vibrational frequencies. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102345j [article] Thermal dehydration and vibrational spectra of hydrated sodium metaborates [texte imprimé] / Amy M. Beaird, Auteur ; Li Peng, Auteur ; Hilary S. Marsh, Auteur . - 2011 . - pp. 7746–7752. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 13 (Juillet 2011) . - pp. 7746–7752 Mots-clés : Catalysis  Reaction  kinetics  Inorganic  reaction  mechanisms Résumé : Sodium metaborate hydrates are a class of compounds represented by the stoichiometry NaBO2·xH2O. Recently, sodium metaborate has received attention as the byproduct of sodium borohydride hydrolysis, a reaction that is under consideration for hydrogen storage applications. The aim of this work was to understand the disposition of water in the crystal structure of hydrated sodium metaborates and to characterize the thermal stability and dehydration of the various hydrated species to optimize hydrogen storage efficiency as well as recyclability of the borate. Observations from a suite of analytical techniques including thermal analyses (thermogravimetric analysis/differential scanning calorimetry), X-ray diffraction, and Raman spectroscopy were correlated to characterize the dehydration mechanism of commercially available sodium metaborates, with an emphasis on the dihydrate (x = 2). A transformation from tetrahedrally coordinated boron to trigonal boron occurs when NaB(OH)4 (x = 2) is heated between 25 and 400 °C. The first dehydration to Na3[B3O5(OH)2] (x = 1/3) releases 5 mol of water between 83 and 155 °C. The final mole of water is released between 249 and 280 °C, and Na3B3O6 (x = 0) is formed. Raman spectra are reported for x = 2 and 1/3 for the first time. First-principles density functional theory was used to compute Raman spectra of the x = 1/3 and 2 material in order to assign the modes. We found reasonably good agreement between the experimentally measured and calculated vibrational frequencies. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie102345j