Synthesis, characterization, and evaluation of lubrication properties of composites of ordered mesoporous carbons and luminescent CePO4:Tb nanocrystals

Having new potential applications in forging processes in mind, composites of an ordered mesoporous carbon and luminescent metal phosphate nanocrystals were synthesized for the first time. Three kinds of CMK-3/CePO₄:Tb nanocomposites were prepared by treating a mesoporous CMK-3 host with different lanthanide phosphate precursor solutions. Characterization of the obtained nanocomposites by small-angle X-ray scattering, wide-angle X-ray diffraction, transmission electron microscopy, thermogravimetry, and nitrogen physisorption analysis showed that in two cases, the nanocrystals (ca. 2–3 nm in size) were located inside the mesopores, whereas in the third case the nanocystals (ca. 6 nm in size) merely adhered to the outer surfaces of the carbon particles. The CMK-3 and the two nanocomposites had ordered hexagonal structures (space group p6mm); all the materials possessed amorphous carbon walls. After combustion of the nanocomposites, the residues upon excitation with UV light exhibited the typical green luminescence of Tb³⁺. A preliminary evaluation of the lubrication properties of the CMK-3 and one nanocomposite material was performed. The friction factors determined by means of ring upsetting tests revealed that the carbon materials were able to lower frictional forces although they were 3–4 times less efficient than a commercial graphite-based reference lubricant.