Documents disponibles écrits par cet auteur

Calorimetric and microscopic studies on the noncatalytic hydrothermolysis of ammonia borane / Junshe Zhang in Industrial & engineering chemistry research, Vol. 50 N° 18 (Septembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 18 (Septembre 2011) . - pp. 10407–10413 Titre : Calorimetric and microscopic studies on the noncatalytic hydrothermolysis of ammonia borane Type de document : texte imprimé Auteurs : Junshe Zhang, Auteur ; Yu Zhao, Auteur ; Daniel L. Akins, Auteur Année de publication : 2011 Article en page(s) : pp. 10407–10413 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Calorimetric  Microscopic  Hydrothermolysis Résumé : The hydrothermolysis of ammonia borane (AB) can release more hydrogen than AB thermolysis itself at mild temperatures. To obtain more insight into the noncatalytic hydrothermolysis, we investigated this process using a high-pressure differential scanning calorimeter and characterized the condensed residue by thermal analysis and infrared spectroscopy. For mass ratios of AB to water of 3.6, 1.44, and 0.72, the first pyrolysis step is not completed in 1 h at 85 °C. As the temperature increases from 25 to 115 at 1 °C min–1, there exist two exothermic peaks for the mass ratio of 3.6, centered around 82 and 103 °C on the heat flow curve, attributed to the hydrolysis and the first step of AB pyrolysis, respectively. For the mass ratio of 1.44, the top temperatures of these two exothermic peaks are 90 and 100 °C, respectively. However, for the mass ratio of 0.72, only the exothermic peak related to hydrolysis is observed, and its top temperature is ca. 106 °C. At temperatures up to 115 °C, the structural features associated with the product of the second pyrolysis step are absent for the mass ratios of 1.44 and 3.6. In the noncatalytic hydrothermolysis, the hydrolysis occurs much faster than the pyrolysis, and the latter is accelerated by both the heat desorbed from the hydrolysis and its product. Our findings suggest that water prefers reacting with AB rather than binding to the hydrolysis product to form hydrates and the hydrolysis itself can generate about 9 wt % of hydrogen with respect to the total mass of AB and water if sufficient AB is present. In this case, the heat of hydrolysis is 131 kJ (mol of AB)−1, and the solid hydrolysis product decomposes at temperatures about 350 °C. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200878u [article] Calorimetric and microscopic studies on the noncatalytic hydrothermolysis of ammonia borane [texte imprimé] / Junshe Zhang, Auteur ; Yu Zhao, Auteur ; Daniel L. Akins, Auteur . - 2011 . - pp. 10407–10413. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 18 (Septembre 2011) . - pp. 10407–10413 Mots-clés : Calorimetric  Microscopic  Hydrothermolysis Résumé : The hydrothermolysis of ammonia borane (AB) can release more hydrogen than AB thermolysis itself at mild temperatures. To obtain more insight into the noncatalytic hydrothermolysis, we investigated this process using a high-pressure differential scanning calorimeter and characterized the condensed residue by thermal analysis and infrared spectroscopy. For mass ratios of AB to water of 3.6, 1.44, and 0.72, the first pyrolysis step is not completed in 1 h at 85 °C. As the temperature increases from 25 to 115 at 1 °C min–1, there exist two exothermic peaks for the mass ratio of 3.6, centered around 82 and 103 °C on the heat flow curve, attributed to the hydrolysis and the first step of AB pyrolysis, respectively. For the mass ratio of 1.44, the top temperatures of these two exothermic peaks are 90 and 100 °C, respectively. However, for the mass ratio of 0.72, only the exothermic peak related to hydrolysis is observed, and its top temperature is ca. 106 °C. At temperatures up to 115 °C, the structural features associated with the product of the second pyrolysis step are absent for the mass ratios of 1.44 and 3.6. In the noncatalytic hydrothermolysis, the hydrolysis occurs much faster than the pyrolysis, and the latter is accelerated by both the heat desorbed from the hydrolysis and its product. Our findings suggest that water prefers reacting with AB rather than binding to the hydrolysis product to form hydrates and the hydrolysis itself can generate about 9 wt % of hydrogen with respect to the total mass of AB and water if sufficient AB is present. In this case, the heat of hydrolysis is 131 kJ (mol of AB)−1, and the solid hydrolysis product decomposes at temperatures about 350 °C. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200878u

Effect of composition on dehydrogenation of mesoporous silica/ammonia borane nanocomposites / Yu Zhao in Industrial & engineering chemistry research, Vol. 50 N° 17 (Septembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 10024-10028 Titre : Effect of composition on dehydrogenation of mesoporous silica/ammonia borane nanocomposites Type de document : texte imprimé Auteurs : Yu Zhao, Auteur ; Junshe Zhang, Auteur ; Daniel L. Akins, Auteur Année de publication : 2011 Article en page(s) : pp. 10024-10028 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Nanocomposite  Dehydrogenation Résumé : This paper discusses the dehydrogenation of ammonia borane (AB) and MCM-41/AB nanocomposites in which the loading level of AB (i.e., the mass ratio of AB to mesoporous silica) varies from 0.11 to 2.36. The dehydrogenation temperatures shift to low temperatures with decreasing loading levels. At loading levels of 0.11 and 0.15, only one dehydrogenation step is observed at temperatures less than 200 °C. Our results also show that 12.6 wt % of hydrogen in the incorporated AB is liberated from the nanocomposite at a loading level of 0.15 in 1 h at 89.5 °C. We deduce that AB confined within the mesopores is amorphous, while AB outside of the channels has a tetragonal structure. Furthermore, we deduce that at relative low loading levels AB coats the inner surface of mesoporous silica as a monolayer. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24483646 [article] Effect of composition on dehydrogenation of mesoporous silica/ammonia borane nanocomposites [texte imprimé] / Yu Zhao, Auteur ; Junshe Zhang, Auteur ; Daniel L. Akins, Auteur . - 2011 . - pp. 10024-10028. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 17 (Septembre 2011) . - pp. 10024-10028 Mots-clés : Nanocomposite  Dehydrogenation Résumé : This paper discusses the dehydrogenation of ammonia borane (AB) and MCM-41/AB nanocomposites in which the loading level of AB (i.e., the mass ratio of AB to mesoporous silica) varies from 0.11 to 2.36. The dehydrogenation temperatures shift to low temperatures with decreasing loading levels. At loading levels of 0.11 and 0.15, only one dehydrogenation step is observed at temperatures less than 200 °C. Our results also show that 12.6 wt % of hydrogen in the incorporated AB is liberated from the nanocomposite at a loading level of 0.15 in 1 h at 89.5 °C. We deduce that AB confined within the mesopores is amorphous, while AB outside of the channels has a tetragonal structure. Furthermore, we deduce that at relative low loading levels AB coats the inner surface of mesoporous silica as a monolayer. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=24483646

Performance enhancement study of mobile air conditioning system using microchannel heat exchangers / Zhaogang Qi in International journal of refrigeration, Vol. 33 N° 2 (Mars 2010) 

Public ISBD [article]  in International journal of refrigeration > Vol. 33 N° 2 (Mars 2010) . - pp. 301-312 Titre : Performance enhancement study of mobile air conditioning system using microchannel heat exchangers Titre original : Amélioration de la performance d'un système de conditionnement d'air automobile à l'aide d'échangeurs de chaleur à microcanaux Type de document : texte imprimé Auteurs : Zhaogang Qi, Auteur ; Yu Zhao, Auteur ; Jiangping Chen, Auteur Année de publication : 2011 Article en page(s) : pp. 301-312 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Air  conditioning  Automobile  Heat  exchanger  Microchannel  R134a  Improvement  Performance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the present paper, two retrofitted compact and high efficient microchannel heat exchangers were proposed. The new microchannel heat exchangers have advantages in compactness (17.2% and 15.1% volume reduction for evaporator and condenser, respectively), weight (2.8% and 14.9% lighter for evaporator and condenser, respectively), heat transfer characteristics compared with the currently used heat exchangers in mobile air conditioning (MAC) industry. One enhanced and one baseline R134a MAC systems were established including the new microchannel heat exchangers and the traditional MAC heat exchangers, respectively. The system performances have been experimentally carried out under variable ambient conditions in psychrometric calorimeter test bench. The optimal system refrigerant charge amounts for both systems were tested and the results showed that the enhanced system with more compact heat exchangers could reduce system charge amount and the minimum effective charge amount was less than that of the baseline system. The enhanced system could supply more cooling capacity to car compartment under all test conditions because of higher performance heat exchangers. The coefficient of performance (COP) of the enhanced system was slightly lower than that of the baseline system under idle conditions but higher under all the other test conditions. Cooling capacity and COP of the enhanced system was increased by about 5% and 8% under high vehicle speed condition. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070070900200X [article] Performance enhancement study of mobile air conditioning system using microchannel heat exchangers = Amélioration de la performance d'un système de conditionnement d'air automobile à l'aide d'échangeurs de chaleur à microcanaux [texte imprimé] / Zhaogang Qi, Auteur ; Yu Zhao, Auteur ; Jiangping Chen, Auteur . - 2011 . - pp. 301-312. Génie Mécanique Langues : Anglais (eng) in International journal of refrigeration > Vol. 33 N° 2 (Mars 2010) . - pp. 301-312 Mots-clés : Air  conditioning  Automobile  Heat  exchanger  Microchannel  R134a  Improvement  Performance Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : In the present paper, two retrofitted compact and high efficient microchannel heat exchangers were proposed. The new microchannel heat exchangers have advantages in compactness (17.2% and 15.1% volume reduction for evaporator and condenser, respectively), weight (2.8% and 14.9% lighter for evaporator and condenser, respectively), heat transfer characteristics compared with the currently used heat exchangers in mobile air conditioning (MAC) industry. One enhanced and one baseline R134a MAC systems were established including the new microchannel heat exchangers and the traditional MAC heat exchangers, respectively. The system performances have been experimentally carried out under variable ambient conditions in psychrometric calorimeter test bench. The optimal system refrigerant charge amounts for both systems were tested and the results showed that the enhanced system with more compact heat exchangers could reduce system charge amount and the minimum effective charge amount was less than that of the baseline system. The enhanced system could supply more cooling capacity to car compartment under all test conditions because of higher performance heat exchangers. The coefficient of performance (COP) of the enhanced system was slightly lower than that of the baseline system under idle conditions but higher under all the other test conditions. Cooling capacity and COP of the enhanced system was increased by about 5% and 8% under high vehicle speed condition. DEWEY : 621.5 ISSN : 0140-7007 En ligne : http://www.sciencedirect.com/science/article/pii/S014070070900200X