Control of molecular-level ice crystallization using antifreeze protein and silane coupling agent

To obtain acceptable ice-slurry characteristics for low-temperature energy storage and transport systems, methods for preventing ice recrystallization must be developed. Antifreeze proteins (AFPs) are known to be an effective additive in ice-slurry systems, making ice slurries resistant to recrystallization, and thereby improving flowability. However, AFPs are expensive and easily degrade. Therefore, we investigated the use of silane coupling agents (SCAs) as substitutes for AFPs. To determine the SCAʹs ability to control crystallization, in this study we observed free growth of ice crystals in SCA solutions, and found that SCAs that form long-chain molecules in water are effective for crystallization control. Then we analyzed ice crystal surfaces containing AFPs and SCAs by using scanning tunneling microscopy (STM) to investigate the mechanism of crystallization control with these additives. STM observation of ice crystal surfaces showed that the AFP molecules are adsorbed onto the ice crystal surface on the {202̄1} planes along the 〈011̄2〉 directions, preventing further crystal growth from the site where the AFP molecules are adsorbed. Furthermore, we found that long-chain SCA molecules are adsorbed onto ice crystal surfaces, preventing crystal growth from the site where the long-chain SCA molecules are adsorbed.