Achieving macroscale superlubricity with ultra-short running-in period by using polyethylene glycol-tannic acid complex green lubricant

Abstract

Superlubricating materials can greatly reduce the energy consumed and economic losses by unnecessary friction. However, a long pre-running-in period is indispensable for achieving superlubricity; this leads to severe wear on the surface of friction pairs and has become one of the important factors in the wear of superlubricating materials. In this study, a polyethylene glycol-tannic acid complex green liquid lubricant (PEG10000-TA) was designed to achieve macroscale superlubricity with an ultrashort running-in period of 9 s under a contact pressure of up to 410 MPa, and the wear rate was only 1.19 × 10−8 mm3·N−1·m−1. This is the shortest running-in time required to achieve superlubricity in Si3N4/glass (SiO2). The results show that the strong hydrogen bonds between PEG and TA molecules can significantly reduce the time required for the tribochemical reaction, allowing the lubricating material to reach the state of superlubrication rapidly. Furthermore, the strong hydrogen bond can share a large load while fixing free water molecules in the contact zone to reduce shear interaction. These findings will help advance the use of liquid superlubricity technology in industrial and biomedical.

Macroscale Superlubricity with Ultralow Wear and Ultrashort Running-In Period (∼1 s) through Phytic Acid-Based Complex Green Liquid Lubricants

“…Compared with the initial state, the PA molecules in the lubricant can quickly adsorb to the surface of the friction pair in a running-in period, which may be one of the critical factors for PEG–PA lubricant to achieve superlubrication after an ultrashort running-in time in this study. And the time-consuming tribochemical reaction may not be the main reason for the superlubrication achieved in this study. , Therefore, under the combined action of the above-mentioned hydrogen bond network structure and the immobilized water molecule layer, the lubricant can realize liquid superlubrication with a very short running-in period. This unique design promises to resolve the conflicting issues between low friction and high load bearing in liquid superlubricants.…”

“…And the time-consuming tribochemical reaction may not be the main reason for the superlubrication achieved in this study. 18,57 Therefore, under the combined action of the above-mentioned hydrogen bond network structure and the immobilized water molecule layer, the lubricant can realize liquid superlubrication with a very short running-in period. This unique design promises to resolve the conflicting issues between low friction and high load bearing in liquid superlubricants.…”

Macroscale Superlubricity of Hydrated Anions in the Boundary Lubrication Regime

“…Different to “hard-on-hard” friction pairs such as Si 3 N 4 /sapphire and steel/steel, ,− polymer/sapphire forms a “hard-on-soft” or “soft-on-hard” friction pair, which will cause significant elastic deformation or even plastic deformation of “soft” polymers. , To evaluate the effect of this deformation on hydration lubrication, the friction materials of the ball and the disk were swapped with each other to compare the lubrication performance between the “soft” ball on the “hard” disk and the “hard” ball on the “soft” disk under the lubrication of acidic Na 2 SO 4 solution. Figure C,D shows the comparison of velocity-dependent COF for polymer/sapphire and polymer/silica interfaces, respectively.…”

Competition-Induced Macroscopic Superlubricity of Ionic Liquid Analogues by Hydroxyl Ligands Revealed by in Situ Raman

“…The COF of ILA 1:20 shows anomalous pattern due to the lower viscosity (i.e., poor hydrodynamic effect and weak load-bearing capacity during friction), as shown in Figure S2. 34,35 The optimized ILA 1:2 can achieve stable superlubricity under applied loads of 2−3 N (i.e., 288− 360 MPa, Figure 2b), indicating a relatively high load-bearing capacity for ILA 1:2 at low humidity. The dependence of the sliding velocity against average COF at a load of 2 N is displayed in Figure 2c for ILA 1:2 .…”