Neutron scattering and microscopy studies of the structure and dynamics of water near a nanostructured hydrophilic copper oxide surface

Abstract

Recently, it has been shown that superhydrophilic coatings of "grass-like" cupric oxide (CuO) nanostructures can significantly improve the thermal performance of heat transfer devices known as oscillating heat pipes (OHPs). The origin of this enhanced performance is currently unknown, but it is believed to be attributed to the thin film of interfacial water supported by the nanostructures that coat the OHP's interior surface. The aim of this work is to investigate the microscopic origin of enhanced heat transfer at the CuO surface by studying the structure, morphology, freezing/melting behavior, and dynamics of the water in proximity to the CuO coating over time and length scales that span picosecond-to-seconds and angstroms-to-millimeters, respectively . ... Our results demonstrate that water near superhydrophilic CuO nanostructures exhibits low-temperature anomalies in its structure and dynamics at the molecular level-a direction of research that has both applied and fundamental interest. The significantly altered structure and dynamics of the interfacial water could affect the boundary conditions for bulk water motion inside of an OHP during its operation. To test this hypothesis, we have proposed time-resolved neutron imaging experiments to characterize the kinetics of water oscillations in CuO-coated OHPs.