In January 2022, I started working at the Cold Regions Research and Engineering Laboratory (CRREL). While working part-time during the school year, I focused on the microstructural characterization of ice in connection with ongoing research on ice adhesion and material science. Through laboratory-based experiments, I learned procedures for growing ice specimens with variable microstructures, methods to prepare specimens for analysis, and techniques for characterizing ice microstructures in a polarized optical microscope. As I gained experience, I began my own project to hone in on optimal growth conditions for structural integrity, which was initially indicated to be a uniform columnar structure with very thin ice grains. I focused on four variables: the temperature of the mold in which ice is grown, the temperature of the water poured into the mold, the temperature gradient between the freezer and the chilled plate on which the mold rests, and the weight percentage of cellulose in the ice. This last variable has a procedural as well as substantive value because cellulose increases structural integrity of ice while minimizing thermal heat transfer. I conducted microscopy on segments of a matrix of all possible combinations, from which I extrapolated the most columnar microstructure, and then grew and tested said microstructure to confirm my findings. I presented my findings at the Dartmouth College Wetterhahn Symposium in May 2022.
While working full-time at CRREL this summer, I transitioned to optical testing with an ASD Spectroradiometer on ice samples to analyze reflection, transmission, and absorption. I was looking for maximum reflectance and minimum absorption, the combination of which decreases thermal heat transfer within ice and thus minimizes melting. To separate variables, I used Minitab to conduct a DOE and gather main effects plots and interaction plots for each variable. The analysis showed the hypothesis from the microscopy conflicted with the results of the optical data, which agreed with the initial analysis of the graphed optical data. I presented this data at the CRREL Summer 2022 Student Symposium. This school year, I am strengthening my findings by performing fatigue testing using an Instron to determine which variables affect melting and structural integrity under constant force. This added data will allow me to determine whether microstructure or optical characteristics influence melting more, and which variables have larger effects.