Facile synthesis of ultrathin NbTe2 nanosheets for enhanced tribological properties as a lubricant additive

Graphite-like bulk NbTe2 powders were prepared by a facile solid phase synthesis process and ultrathin NbTe2 nanosheets were obtained by using wet ball milling induced delamination. The X-ray diffraction analysis illustrated that the reduction of particle size was mainly along the stacking direction of the basal planes without great influence on the short range order of NbTe2 crystals. Scanning electron microscopy, transmission electron microscopy, and atomic force microscope observations revealed that the longitudinal dimension of NbTe2 samples changed into the nanoscale from the larger micron level after mechanical exfoliation. The exfoliated NbTe2 nanosheets had better long-term dispersion stability in paraffin oil than bulk NbTe2. The tribological properties were determined on an UMT-2 ball-on-disk friction and wear tester. The results indicated that the paraffin oil with NbTe2 nanosheets exhibited better lubricating behaviors with the lower friction coefficient and wear rate in comparison with the bulk NbTe2. It was demonstrated that NbTe2 nanosheets could easily enter into a point of friction contact, and form an available tribofilm to prevent the direct contact between counterparts during the friction process. Furthermore, this work shows the potential applications of ultrathin NbTe2 nanosheets in the field of tribology.