Reference : Towards the production of carbon xerogel monoliths by optimizing convective drying co...
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Chemistry
Physical, chemical, mathematical & earth Sciences : Physics
Engineering, computing & technology : Chemical engineering
Engineering, computing & technology : Materials science & engineering
http://hdl.handle.net/2268/7952
Towards the production of carbon xerogel monoliths by optimizing convective drying conditions
English
[fr] Vers la production de monolithes de xérogel de carbone en optimisant les conditions de séchage convectif
Job, Nathalie mailto [Université de Liège - ULg > Département de chimie appliquée > Génie chimique - Génie catalytique >]
Sabatier, Françoise [> > > >]
Pirard, Jean-Paul mailto [Université de Liège - ULg > Département de chimie appliquée > Génie chimique - Génie catalytique >]
Crine, Michel mailto [Université de Liège - ULg > Département de chimie appliquée > Génie chimique - Opérations physiques unitaires >]
Léonard, Angélique mailto [Université de Liège - ULg > Département de chimie appliquée > Génie chimique - Opérations physiques unitaires - Département de chimie appliquée >]
Oct-2006
Carbon
Pergamon-Elsevier Science Ltd
44
12
2534-2542
Yes (verified by ORBi)
International
0008-6223
Oxford
[en] carbon xerogels ; porous carbon ; heat treatment ; texture ; drying
[en] Resorcinol-formaldehyde hydrogels prepared at various resorcinol/sodium carbonate ratios, R/C, were convectively air dried. The influence of the drying operating conditions, i.e. air temperature and velocity, on the pore texture, shrinkage and cracking of the dried gels were investigated. Shrinkage was found to be isotropic. The shrinkage behaviour and the textural properties of the gels are independent of the drying operating conditions, but are completely determined by the value of the synthesis variables. The analysis of the drying kinetics shows two main drying periods. During the first phase, shrinkage occurs and the external surface of the material remains completely wet: heat and mass transfers are limited by external resistances located in a boundary layer. When shrinkage stops, the second period begins: the evaporation front recedes inside the solid and internal transfer limitations prevail. The drying time can be reduced by increasing the air temperature and/or velocity, but the temperature increase is limited when monolithicity is required, especially when the pores are small. For example, at a temperature of 160 degrees C and a velocity of 2 m/s, about 1 h is needed to dry a 2.8 cm in diameter and 1 cm in height cylinder containing macropores (pore width > 50 nm after drying). The same cylinder presenting small mesopores (pore width = 10-15 nm after drying) requires 20 h at 30 degrees C and 2 m/s to reach complete dryness without the development of cracks. (c) 2006 Elsevier Ltd. All rights reserved.
Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS
http://hdl.handle.net/2268/7952

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