4. Impregnation processes

4.1 General features of supercritical impregnation

Supercritical fluids are vectors/impregnating agents of choice because of their specific properties described above: a liquid-like density (200 to 900 kg · m ^–3 ), a gas-like viscosity (10 ^–5 to 9 × 10 ^–5  Pa · s), a diffusivity higher than in liquid phase (2 × 10 ^–8 to 7 × 10 ^–8  m ²  · s ^–1 ) and a very low interfacial tension. The transport of a solute, solubilized in a supercritical phase, inside a solid matrix is...