The annual Ashton Cary Lecture series features distinguished scholars in fields of significance to chemical engineering. The visiting lecturers, in addition to presenting seminars on recent engineering advances, participate in informal discussions with Georgia Tech faculty and students.

The 27th Annual Ashton Cary Lecturer, Dr. William B. Russel, is the A.W. Marks ’19 Professor in the Department of Chemical Engineering and Dean of the Graduate School at Princeton University. He presents Collapsing Colloidal Gels: How and When? as the 27th Annual Ashton Cary lecturer.

Collapsing Colloidal Gels: How and When?
Colloidal dispersions with weakly attractive, and generally short-range, interparticle forces often form gels instead of separating into two equilibrium phases. These gels represent a non-equilibrium and non-ergodic state that has attracted considerable attention in the field over the past 5-10 years. An interesting facet of some systems is the propensity to suddenly collapse after left standing for some time under normal gravity. This delayed collapse seems to be controlled by thermally activated creep, which produces a time scale that increases roughly exponentially with the strength of attraction. The driving force must be a combination of the gravitational load and thermodynamic forces seeking to drive a gas-liquid or gas-crystal phase separation. The collapse takes several forms, ranging from a rapid homogenous disintegration of the gel to opening of fissures that are quickly widened by fluid flow. While a correlation of some collapse times has been constructed, no theory or model exists capable of anticipating the phenomena.