Controlling heterogeneous ice nucleation with chemical impurities and electrical charge

A fundamental understanding of the nucleation of ice crystals is of importance in a wide range of fields: cryopreservation of biological samples relies in the control of ice nucleation, avoiding ice formation on aircraft and wind turbines is key to their efficient and safe operation, and ice nucleation in clouds is very important for the planet’s climate. However, we have very limited knowledge of why certain materials trigger the formation of ice, while others do not. 

It is thought that specific sites on surfaces which are perhaps just 10’s of nanometers in size are responsible for nucleation, but these sites can occupy only 10^-10 % of the surface. Hence, they are incredibly difficult to identify and characterise and our understanding of them remains extremely poor. What makes effective active sites is a key topic

There is evidence that impurities such as lead and iodine may promote nucleation and there are also mechanisms where charge and electric fields can promote ice nucleation. Our hypothesis is that nucleation occurring at specific active sites is related to impurities and/or charge at these sites.

Objectives

i)            Experimentally investigate the role of electrical charge in nucleating ice – this may offer novel means to control ice nucleation and may offer explanations for unexplained high temperature nucleation in clouds;

ii)           investigate the role of minor chemical contaminants in promoting ice nucleation in various materials – there is evidence that suggests the inclusion of elements like lead, strontium and iodine promote nucleation in otherwise inert materials.

iii) apply the knowledge to firstly design materials which might be used in cryopreservation applications and secondly to identify natural materials and situations where enhanced nucleation may occur in the atmosphere.