Jinlu Li,Tianyi Sui,Haolin Li,Feifei Zhao,Xuan Bao,Guochen Ning,Yuan Zhang,Jingtao Wang,Bin Lin
Serious wear during running-in period significantly limited the application of ceramics in industry. With poor activity, ceramic contact surface is hard to be protected during friction. In this study, ceramics tribological properties are significantly enhanced and ultra-low friction is achieved in short time by formation of high-strength nano surface film. Copper nanoparticles with linear and cubic morphologies were synthesized and dispersed into water-based lubricants for silicon nitride ceramic friction pairs. A 1:1 mixture of copper nanoparticles with linear and cubic morphologies exhibits the best lubrication performance at an optimal concentration of 0.2 wt%. The result shows an 87.01 % reduction in the coefficient of friction, and a wear rate of 0.18 % of that obtained in the case of deionized water. High-strength protective film is found generated on the ceramic surface, which reduces wear and promotes the forming process of ultra-smooth surface to achieve ultra-low friction. Based on the characterization results, lubrication mechanism is elucidated, quick generation of surface film with high strength is the essential for reducing wear and running-in period.
PAEs usually adsorb on indoor surfaces to form organic films, which could be more hazardous after enriching VOCs. Two typical PAEs, DnBP and DEHP, in the film phase, were chosen to explore the enrichment capacity of gaseous toluene, hexanol, and benzyl alcohol in this study. Exposed to gaseous VOCs less than 250 ppb, film-phase DnBP and DEHP could capture benzyl alcohol significantly and hexanol slightly from the air, respectively, while toluene was hardly absorbed in the films. Henry's law constants and partition coefficients ( K ) of VOCs in DnBP or DEHP films were derived, supposing films as dilute solution systems. The K value of VOC in DnBP or DEHP films was 1∼2 orders larger than the octanol-air partition coefficient ( K oa ), indicating that the surface film composition greatly influences VOC adsorption. Benzyl alcohol was the largest VOC component in surface films, agreeing well with the molecular dynamics simulation results. The hydroxyl and phenyl groups of benzyl alcohol molecules may be key factors in VOC enrichment. They form hydrogen bonds with the ester group and π-π stacking interaction with the phenyl group of DnBP or DEHP molecules, respectively. After enriching VOCs, film-phase PAEs could evoke combined exposure risks to human beings.
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