Rearrangement and elimination of ordered surface layers of crystalline bubble structures due to gas diffusion

Abstract

We describe a hitherto unknown self-organising effect in wet crystalline bubble structures exposed to air. Due to the escape of gas from the bubbles in the top surface layer, bubbles shrink and create space for the bubbles of the lower layers to interpose themselves at the top. This occurs irregularly, but finally a newly ordered bidisperse top layer is formed. This process can be followed for several episodes of elimination of surface layers. The crystalline orientation influences the speed of shrinkage and formation of the bidisperse top layer. Compared with diffusion of a single bubble or monodisperse monolayer on top of a liquid pool, the diffusion is much faster. This may be accounted for by the extra buoyancy force leading to a larger exposure of the bubbles at the surface.

Analysis of the internal structure of monodisperse liquid foams by X-ray tomography

“…The fcc structure is evident, confirming the provisional conclusion of the earlier work. 9 A quantitative analysis of the mCT data was undertaken using the image processing software MAVI. 22 Through the use of filtering routines, it is possible to reduce image noise and structural defectssuch as merged cells-produced during the image step.…”

“…Ordering at a 3d wet foam surface was first reported by Bragg and Nye. 6 Van der Net et al, [7][8][9] conducted detailed investigations of the surface structures of ordered samples, and used ray tracing techniques to deduce the structure of the first three to four layers. This, together with viewing of the underside of floating samples, was highly suggestive of extensive crystallisation within the interior, predominantly in the fcc structure.…”

Short‐Range Ordered Aluminum Foams

“…Monodisperse aqueous foam has been verified to be in an ordered dense packing after gas injection and before its self-organization. [22,23] Although liquid cells of aluminum foam should also be densely and ordered packed just after gas injection if the influence of the rotating needle is not considered, due to drainage previous to solidification it is not easy for the final aluminum foam structure to be ordered. The main difficulty for obtaining ordered aluminum foam is controlling the cell size, size uniformity, and cell shape during preparation.…”

“…studies about ordered stackings of monosized bubbles are based on aqueous foams. [21][22][23] Bubbles can anneal to polydisperse or bidisperse states from the monodisperse system via a selforganizing effect. [22,24] It was also demonstrated that the closepacked FCC structure formed by monosized spherical bubbles transforms into a body-centered cubic (BCC) Kelvin structure with tetrakaidecahedron-shaped bubbles as the liquid fraction decreases.…”

“…[21][22][23] Bubbles can anneal to polydisperse or bidisperse states from the monodisperse system via a selforganizing effect. [22,24] It was also demonstrated that the closepacked FCC structure formed by monosized spherical bubbles transforms into a body-centered cubic (BCC) Kelvin structure with tetrakaidecahedron-shaped bubbles as the liquid fraction decreases. [23] García-Moreno et al disclosed that the meniscus shape caused by the surface tension of columnar aqueous foam will also lead to a deviation from an ideal structure.…”