Thermal expansion of Cu(II)O nano- and micro-particles and composites at cryogenic temperatures

A systematic study of the thermal expansion of copper oxide (CuO) nanoparticles and copper oxide-based composites, prepared by a range of techniques, was performed at cryogenic temperatures in the effort to reproduce recently reported giant negative coefficient of thermal expansion (CTE) of CuO nanoparticles. Chemically synthesized CuO nanoparticles, nanoparticles formed by ball milling of CuO material, CuO nanoparticles with differing surface functionalization, particles subjected to post-treatments such as electron irradiation, and embedded into various resins or compacted at high pressures were studied by dilatometry and X-ray diffraction (XRD) at temperatures between 20 and 300 K. None of the samples exhibited large negative CTE in the examined temperature range.