Grant: Discovery Launch Supplement

The long-term objective of my research program is the successful development of novel materials for managing the waste heat produced in various industrial and technological processes. My approach is to engineer the nanostructures of such materials to address the required superconducting or insulating heat carrier characteristics of these materials. With the anticipated energy demands from population growth and the fourth industrial revolution, waste heat generation is on an upward trajectory all around the globe. In this regard, this research program will be greatly valuable for Canada in achieving sustainability. Managing thermal energy requires materials with ultrahigh and ultralow thermal conductivities, which can efficiently conduct and insulate heat. The main challenge is addressing the propagation of quantized lattice vibrations known as phonons, which are the main heat carriers in solids at moderate temperatures except for metals. As their transport mechanisms strongly depends on the frequency, understanding heat carried by phonons must be accustomed to different frequency regions. Such task is feasible in computer calculations based on interatomic potentials predicted from first-principles. However, previous experimental works focused on measuring bulk-scale thermal conductivities, which is not sufficient to distinguish frequency-dependent phononic heat conduction at small scales. This severely limits experimental access to critical information required to design materials with ultralow or ultrahigh thermal conductivities. My research program is mainly experimental and addresses frequency-dependent phononic heat transfer with novel nanostructures. Phonon scattering rate at crystal features significantly decreases at frequencies below 1THz, and destructive interference between phonons scattered at crystal features can alter the phonon band structure. These aspects are drastically amplified in structures with highly dense crystal features, and novel nanostructures can play the role of phonon frequency filters as well as phonon modifiers capable of addressing small-scale frequency dependent phononic heat conduction. There characteristics will be used to (i) establish a fundamental connection between mechanical properties associated with atomic movements and phonon transport properties to create a database equivalent to the power of interatomic potential energy in computer calculations; (ii) leverage the database to custom-design specialized nanostructures with desired phonon properties and thermal conductivities by combining appropriate interatomic potentials together using thin film stacking method; (iii) implement the resulting thermal conductivities in practical heat management applications in economically viable and scalable ways. This will pioneer a strategy for achieving ultralow/ultrahigh thermal conductivities and significantly reduce waste heat in various sectors in Canada, moving Canada closer towards achieving sustainability.