Drying structures of marine clay in the deionized aqueous suspension

Drying dissipative patterns during drying of marine colloidal (MC) clays were observed in the deionized aqueous suspension on a cover glass, a watch glass, and a Petri glass dish. Two kinds of broad rings (BR), i.e., BR of small particles at the outside edge and BR of large particles at the inner area from the edge, were observed. The size of the outside BR was the same as that of the initial suspension irrespective of colloidal concentration, whereas the size of the inner BR increased as colloidal concentration increased. Highly distorted multi-rings, i.e., branch-like or net-like patterns, appeared. Furthermore, no spoke lines formed except the areas at the outside edge of the dried film. These observations support the circular stacking of the anisotropic-shaped MC particles during the convectional flow process. The B type of solutes was deduced for MC from the drying patterns, where strong solute-substrate affinity especially for the small particles and weak inter-solute affinity coexist.