Synthesis of Ultrathin WS2 Nanosheets and Their Tribological Properties as Lubricant Additives

Abstract

In this paper, ultrathin WS2 nanosheets with thickness of about 5 nm were successfully prepared by a facile solid phase reaction method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). On the basis of experimental results obtained under different reaction durations, a possible formation mechanism of WS2 nanosheets is proposed. The tribological performance of ultrathin WS2 nanosheets as additives in the 500SN base oil was tested by an UMT-2 ball-on-disc tribotester, and the worn surface of the steel disc was investigated by a non-contact optical profile testing instrument and SEM. The results showed that the friction coefficient and anti-wear property of base oil can be improved strikingly by adding ultrathin WS2 nanosheets. Especially, when the concentration of WS2 nanosheets was 1.0 wt.%, the corresponding lubricating oil exhibited the best tribological properties. Moreover, according to the investigation of the wear scar, an anti-friction and anti-wear mechanism is proposed. It is believed that the reduction of friction and wear must come from the addition of ultrathin WS2 nanosheets which can penetrate and enter the friction interface and form a continuous tribofilm on the rubbing face.

Tribology Properties of Synthesized Multiscale Lamellar WS2 and Their Synergistic Effect with Anti-Wear Agent ZDDP

“…In recent years, the preparation methods of MoS 2 /WS 2 nanoparticles have been extensively studied. The researchers have successfully prepared MoS 2 /WS 2 nanoparticles through various synthetic methods and discussed their tribological properties under different experimental environments [5][6][7]. Among them, inorganic fullerene-like (IF) MoS 2 /WS 2 nanoparticles seem to be the most widely explored ones, probably because of their low surface energy, fine chemical stability, and spherical shape, which allow them to play an active role in a variety of tribological applications [8][9][10].…”

Cold‐Sprayed Metal Coatings with Nanostructure

“…It also possesses excellent solid lubrication properties due to the 2D layered structure and easy interlayer sliding. In addition, the special structure of WS 2 allows it to be usable in high temperature, high pressure, high vacuum, high load, and with radiation and corrosive media environments [35,36]. Moreover, because WS 2 has an excellent adsorption capacity on the metal surface, it can be used as reinforcements in MMCs to improve the lubrication performance [77].…”

“…irdly, using nanomaterials to reinforce MMC coatings can also make the coating to present nanostructure [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]. Up till now, a large number of studies have been done to study the cold sprayed coatings with nanostructure.…”

Synthesis of Tribological WS2 Powder from WO3 Prepared by Ultrasonic Spray Pyrolysis (USP)

“…Figure 1b shows the lubrication mechanism of WS 2 single sheets. So far, various methods of producing WS 2 of different size and morphology using WO 3 as precursor have been established, such as: gas-solid phase reaction [6][7][8], chemical vapor deposition (CVD) [9][10][11], hydrothermal method [12][13][14], mechanochemical activation method [15], and solid-solid phase reaction [16][17][18].…”

“…Regarding solid-solid phase reaction, the synthesis of WS 2 powder was carried out by sulfurization of the WO 3 powder with thiourea in a N 2 atmosphere at 850 • C for 1 h in a horizontal tube furnace [16][17][18].…”