The microscopic contact morphology of ice crystal on substrate and its effect on heterogeneous nucleation/icing

•The morphology of the ice tip on different surfaces were recorded with microscope.•Contact angles of ice on substrate are obtuse and decrease with temperature as Sigmoid function•Surface energy can affect substrate icing by altering the ice tip and heat transfer•The ice contact angle is found to be pretty closed to the ice nucleus contact angle As one of the long-standing crucial theoretical assumptions of the heterogeneous nucleation and substrate icing theory, the tiny shape of an ice tip on the substrate commands further detailed experimental observation. In this paper, the morphology and growth processes of ice on different near-thermal insulation surfaces at a low supercooling degree were observed by microscope. Experimental results show that the contact angles of the dendritic ice tip on the substrates are all obtuse under a lower supercooling degree, and decrease with temperature as a Sigmoid function. Moreover, the analysis of ice growth on different substrates reveals that the surface property can affect substrate icing by altering the ice tip; that is, as the ice contact angle increases, the radius will increase and the influence of the thermal conduction of substrate on the ice tip will decrease, ultimately leading to a slower growth rate. Significantly, heterogeneous nucleation experiments illustrate that the obtained ice contact angle is close to the ice nucleus contact angle. Consequently, compared with previous theories, the temperature-dependent ice contact angle could be used to accurately predict the nucleation rate and ice growth.