A Direct AFM Investigation of the Local Interaction Between a Single Particle and a Growing Ice Front Within Alumina Slurries
Résumé
AFM technique is used to investigate the local interaction between a growing ice front and a single particle, to further elucidate phenomena related to shaping by ice templating and freeze-casting. For that purpose, cantilevers exhibiting spring constants of 0.58 and 0.12 N/m are functionalized (or not) with attached micrometer-sized silica spheres with diameters of 600 nm and 10 mu m. When using deionized water solutions, it appears that the lateral repulsion rate recorded on silica-free cantilevers decreases from 67 to 389 mu m/s (+/- 1%) for pH values of 3 and 6, respectively. At pH 9, an optimum is reached (35 mu m/s). The functionalization of cantilevers does not lead to significant changes. For colloidal alumina suspensions (32 vol% of solid content at natural pH of 8.7, mean size of 400 nm), the effect of deflocculation status is characterized. The more stabilized suspensions exhibit the lowest repulsion rates (from 100 to 230 mu m/s), while the less stable suspensions lead to higher repulsion rates (>= 500 mu m/s). This behavior is consistent with the establishment of a preferential growing path through the loose (open) structure of flocculated particles. AFM appears as an analytical tool of interest to study local phenomena occurring during ice templating of colloidal suspensions.