Penetration Pathways of Liquid Gallium in Wood Seen by Scanning Electron Microscopy


  • Yvonne Trenard
  • Paul Gueneau


Scanning electron microscopy, penetration of wood, liquid gallium, <i>Pinus sylvestris</i> L, <i>Abies pectinata</i> D.C, <i>Fagus sylvatica</i> L


In order to understand and to visualize which primary pathways are followed by liquid penetration, specimens of Pinus sylvestris L., Abies pectinata D.C., and Fagus sylvatica L. were impregnated with liquid gallium at a temperature of 50 C and at varying pressures. The gallium was then solidified by cooling, and its location was observed by scanning electron microscopy on specimens previously coated with carbon to prevent redistribution of the gallium.

In softwood the liquid metal penetrated first into the longitudinal tracheids and subsequently into the rays through the cross-field-pitting. The reverse did not apparently occur, however, as radial flow through the rays was negligible. In hardwood only vessels were penetrated. For all three species, penetration uniformly increased with pressure but seemed to reach a maximum at a critical pressure level, 8 bars for pine, 16 bars for fir, and much more elevated for beech. Pit dimensions are obviously important to allow flow at low pressures and in addition, when they are large as in pine, tearing of the membrane facilitates it. Some relationships of these observations to practical aspects of wood preservation are discussed.


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