Subcooling in plastic crystalscharacterization, understanding and mitigation

Résumé

Plastic Crystals are pointed out as potential solid-solid based Phase Change Materials for low-medium temperature applications. Their main drawback, the subcooling, has been assessed in this thesis in terms of basics understanding and approaches for its mitigation. The plastic phase of these materials consists of a highly orientationally disordered solid phase, in which the molecules are fixed inside the unit cell. The high freedom of motion of protons in such a solid phase, prevent the plastic crystals from reorganize the hydrogen bonds and undergo the plastic-to-crystalline phase transition. Processing of the materials, dispersion of dopant agents and application of pressure were the three approaches separately tested in order to minimize the subcooling, reaching a reduction up to a 69% for the material processing by ball milling.