The physics of water transfers in softwood
post-doc: Dang-Mao NGUYEN
team:Philippe Coussot, Sabine Caré Daniel Grande, Olivier Pitois, Estelle Renard
Wood is a material of construction of choice as it exhibits remarkable mechanical and thermal properties. Moreover it contributes to the comfort of the occupant of a house by regulating the ambient relative humidity. However water transfers may also lead to wood or structure degradation (loss of mechanical properties or fungi attacks). In this context a better knowledge of the mechanisms of water transfers will be useful in order to favor the use of wood in building industry or for a better prediction of its properties in time, or to develop appropriate techniques of preservation.
Actually the mechanisms of water transfers (imbibition, drying, filtration), which depend on the hierarchical and multiscale structure of wood, are not so well-known. Our recent results on hardwood showed from Magnetic Resonance Imaging (MRI) experiments that, in contrast with simple porous media, water absorption is about three orders of magnitude slower than expected from standard Washburn imbibition process because it is fundamentally driven by bound water penetration and diffusion in cell walls in link with the swelling of the material. These results confirm that the “water absorbent” properties of wood are very specific.
The present post-doc project will focus on the water transfer mechanisms in softwoods, which have a structure significantly different than hardwood, which might be at the origin of significantly different mechanisms. For the study we will select a few softwoods which will serve as reference. The post-doc researcher will carry out tests of imbibition and drying, starting from samples in different initial conditions. He/She will rely on the use our MRI set up to distinguish bound and free water transfer dynamics, and X-Ray microtomography, optical microscopy or Scanning Electronic Microscopy to get information on the structure. The project is granted by Labex MMCD (Université Paris-Est), within the frame of a project involving several researchers from Institut de Chimie des Matériaux de Paris-Est (ICMPE (CNRS-UPEC)) and Laboratoire Navier (ENPC-IFSTTAR-CNRS).