Imbibition of Liquid Helium in Aerogels

Abstract

6 pagesInternational audienceWe report optical measurements of the imbibition of liquid helium in a sample of silica aerogel with 90 % porosity. Both direct imaging and light scattering experiments were performed to determine the dynamics and the properties of the liquid-gas interface in both the normal and superfluid phases of liquid helium. In the normal phase, a classical Lucas Washburn behavior is observed for the rise of the imbibition front while the behavior in the superfluid phase is markedly different, as the fluid invades the sample from all sides with a constant speed. In both phases, the interface is rough, leading to light scattering. In addition, condensation ahead of the imbibition front is observed at low temperature in the superfluid phase

Soft matter in hard confinement: phase transition thermodynamics, structure, texture, diffusion and flow in nanoporous media

“…The inhomogeneities result in variations in the local bulk hydraulic permeability and in the capillary pressure at the moving interface resulting in broadening of the imbibition front and thus the coexistence of empty and filled pore segments during the imbibition process. As explored for macro porous systems, this broadening displays universal scaling features on large length and time scales, which are independent of the microscopic details of the fluid and matrix [472,481,482,483,484,485,486,487,488]. This parallels the elegance of critical phenomena [480].…”

“…From a practical point of view, imbibition of fluids in bodies with nanoscale dimensions provides an elegant and effective way to propel nano flows. It can also be exploited to explore the rheology of liquids in spatial confinement and this under very high shear rates [322,324,435,468,469] or characteristics of the imbibition geometry on the nanometer scale [432,[470][471][472]. Moreover, it is now frequently employed for the synthesis of novel hybrid materials [20,458,473] or used in the functionality of nano-devices [379,380].…”

Capillary rise dynamics of liquid hydrocarbons in mesoporous silica as explored by gravimetry, optical and neutron imaging: Nano-rheology and determination of pore size distributions from the shape of imbibition fronts

“…Similarly, as observed here, the inhomogeneities result in variations in the local bulk hydraulic permeability and in the capillary pressure at the moving interface resulting in a broadening of the imbibition front and thus the coexistence of empty and filled pore segments during the imbibition process. Often this broadening displays universal scaling features on large length and time scales, which are independent of the microscopic details of the fluid and the matrix [148,149,150,151,152,153,154,155,156,157]. In the past, most imbibition front broadening studies focused on sand, packed beads and paper.…”

Formation of superfluid liquid pocket in aerogel and its solidification by cooling

“…Silica-aerogels are highly porous materials whose pore size is on a nanometer scale while at the same time being very transparent; we can thus investigate the dynamics inside the material by visual observation. There have been several reports on the imbibition process of normal fluid and superfluid 4 He in aerogel by visualization [10][11][12]; superfluid 4 He is imbibed in aerogel at a constant rate while normal fluid 4 He is imbibed following the classical Washburn law. Anomalous two-step imbibition was also found in highly porous aerogels [11].…”