Semnan University Press Progress in Physics of Applied Materials 2783-4794 1 1 2021 12 01 The effect of liquid nitrogen-microwave treatments on the structural, optical, and tribological properties of WS2 nanoflakes 74 82 6282 10.22075/ppam.2021.24535.1015 EN Mitra Mahdavi Department of Physics, Central Tehran Branch, Islamic Azad University, Tehran, Iran Salimeh Kimiagar Nano Research lab, Physics Department, Faculty of Science, Central Tehran Branch, Islamic Azad university 0000-0002-5818-0337 Fahimeh Abrinaei Department of Physics, East Tehran Branch, Islamic Azad University, Tehran, Iran Journal Article 2021 09 13 WS<sub>2</sub> was successfully synthesized by the hydrothermal method under various liquid nitrogen and microwave treatments. X-ray diffraction (XRD) analysis showed the presence of multiple WS<sub>2</sub> phases, of which hexagonal was the dominant phase. The morphology of the samples was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and WS<sub>2</sub> exfoliation was confirmed after liquid nitrogen and microwave treatments. Fourier transform infrared spectroscopy (FTIR) confirmed WS<sub>2</sub> exfoliation during the exfoliation process. Optical bandgap calculation showed an increase in the exfoliation WS<sub>2</sub> bandwidth to 4.7 eV, which is large enough for the massive indirect bandwidth (1.3 eV) of WS<sub>2</sub>, indicating the effect of quantum confinement. Decreased photoluminescence (PL) showed the production of defects in the samples during the processes. The tribological properties of WS<sub>2</sub> nanoflakes as an additive in oil showed that the coefficient of friction and wear performance of the oil were significantly improved by adding WS<sub>2</sub> nanoflakes synthesized by the hydrothermal method under different liquid nitrogen and microwave treatments. The results show that WS<sub>2</sub> nanoflakes with an improved coefficient of friction and wear performance can be a promising additive that could open a new avenue for the large-scale production of tribological materials. Freezing heating Tribology friction coefficient Environmental friendly https://ppam.semnan.ac.ir/article_6282_c2073ffa77b5357a498057413bb09d3a.pdf