Enhancing Lubricant Performance under Electronic-Control Friction with Cu-BTC@Ag Nanocrystal Additives

Significance 

Electronic-control friction is a significant challenge in the maintenance and durability of electromechanical devices, where electrical currents can exacerbate wear and tear on mechanical components. Traditional lubricants often fail under these conditions due to poor electrical conductivity and inadequate lubrication properties. The search for materials that can improve the tribological performance of lubricants under electronic stress has led to the exploration of ionic liquids and nanoparticles for their conductivity and anti-wear properties. To address these challanges a new study published in ACS Applied Materials & Interfaces conducted by graduate student Yuyun Wang, associate professor Guoliang Zhang, Duo Yang, Yang Li, Wei Yin from the Tianjin University of Technology and Education alongside Yibin Weng from the CNPC Safety and Environmental Technology Research Institute Co., Ltd, the team   investigated the tribological performance of Cu-BTC@Ag nanocrystal additives in lubricants, focusing on their ability to enhance electrical conductivity and reduce wear and friction under electronic-control friction conditions. The researchers synthesized Cu-BTC@Ag nanocrystals through an in-situ generation method. This involved the preparation of silver nanoparticles (Ag NPs) and their incorporation into the Cu-BTC metal−organic framework (MOF) structure. The synthesis aimed to create a composite material where nano-Ag elements were evenly dispersed within the Cu-BTC matrix, leveraging the high surface area and porosity of MOFs to enhance the lubricant’s electrical conductivity and tribological properties. After synthesis, the Cu-BTC@Ag nanocrystals were characterized using various techniques to confirm their structure, composition, and morphology. They used transmission electron microscopy and scanning electron microscopy to visualize the distribution of Ag within the Cu-BTC matrix and to examine the mesoporous structure of the nanocrystals. Moreover, they conducted x-ray diffraction and fourier transform infrared spectroscopy analyses to verify the crystal structure and chemical composition of the nanocrystals, to ensure that the Ag incorporation did not alter the fundamental structure of the Cu-BTC MOF.

The core of the experimental work involved tribological testing to evaluate the performance of Cu-BTC@Ag as lubricant additives. The researchers dispersed the nanocrystals in EMI-BF4 ionic liquid lubricant and conducted friction and tests were performed without applied voltage and with a voltage of 20V to simulate electronic-control friction conditions. They also measured coefficient of friction (COF) and wear volume to assess the lubrication performance. These tests aimed to determine how the presence of Cu-BTC@Ag nanocrystals affected the lubricant’s ability to reduce friction and wear on mechanical components. The authors found that the addition of Cu-BTC@Ag nanocrystals significantly improved the electrical conductivity of the EMI-BF4 lubricant, an important factor for applications involving electronic-control friction. Moreover, with the inclusion of Cu-BTC@Ag nanocrystals, both the average COF and wear volume decreased markedly compared to the base lubricant without additives. This effect was more pronounced at an applied voltage of 20V, indicating the nanocrystals’ effectiveness in electronic-control conditions. Furthermore, the porous structure of the Cu-BTC@Ag nanocrystals allowed for the continuous release of EMI-BF4 into the contact zone under external load, maintaining a steady supply of lubricant and effectively reducing wear and friction. Additionally, the team investigated the mechanisms by which Cu-BTC@Ag nanocrystals improve the lubrication properties under electronic-control conditions. It is proposed that the nanocrystals not only serve as a reservoir for the lubricant, ensuring its steady supply to the friction interface but also participate in the formation of a friction-reducing film. This film is capable of self-repairing wear defects on the friction interface, attributed to the electric field-driven adsorption of Cu-BTC@Ag nanocrystals onto the metal surface, which facilitates the repair of worn areas. In a nutshell, the authors’ findings concludes that Cu-BTC@Ag nanocrystals are highly effective as lubricant additives, significantly enhancing the electrical conductivity and tribological performance of lubricants under electronic-control friction. The new study advances our understanding of MOF-based nanocomposites in tribology and also opens new avenues for the development of advanced lubricant additives capable of reducing wear and extending the lifespan of electromechanical systems. This innovative approach holds promising implications for a wide range of industrial applications, particularly in sectors where electronic-control friction is a prevalent challenge.

Enhancing Lubricant Performance under Electronic-Control Friction with Cu-BTC@Ag Nanocrystal Additives - Advances in Engineering

About the author

Guoliang Zhang is an Associate professor at the Department of mechanical engineering at Tianjin University of Technology and Education (TUTE, China). He graduated from Henan University of Technology (China), where he gained his BE degrees. He continued his graduate studies at Liaoning University of Petroleum and Chemical Technology (China), obtaining his ME.Sc. degree in 2012 under the guidance of Professor Lianhong Zhang. He then went on to China University of Petroleum (Beijing) for his PhD program. After he had finished his postdoctoral course at Tsinghua University, under the supervision of Prof. Shizhu Wen and Prof. Guoxin Xie. In 2018, he started independent work at TUTE. His research interests are in the field of nanocomposites, self-lubrication composites and current-carrying friction.

About the author

Yuyun Wang earned his BE degree in Material Forming and Control Engineering from the Tianjin University of Technology and Education (TUTE, China) in 2021. Subsequently, she relocated to Tianjin University of Technology and Education to pursue his master’s studies under the supervision of Associate Professor Guoliang Zhang. Her research focuses on composite lubricant.

About the author

Li Yang is a lecturer and master tutor of Mechanical Engineering College of Tianjin University of Technology and Education. He completed his PhD at Harbin Engineering University in 2018 studying surface coatings technology. He is mainly engaged in laser surface coating technology and tribology. He has published more than 30 academic papers and applied for more than 10 invention patents.

About the author

Wei Yin is a Associate professor in the College of Mechanical Engineering at the Tianjin University of Technology and Education. He completed his PhD at Jilin University (China) in 2014 studying the Bionic science and engineering. He worked as a postdoctoral fellow at the State Key Laboratory of Tribology, Tsinghua University, from 2014 to 2016. Dr. Yin has authored/co-authored more than 40 research publications and his primary research interests focus on industrial tribology, interface adhesion mechanics, friction and lubrication materials.

Reference

Wang Y, Zhang G, Yang D, Li Y, Yin W, Weng Y. Electronic-Control Friction Behavior of Porous Metal-Organic Framework@Ag Nanocrystals as Self-Repairing Lubricant Additive. ACS Appl Mater Interfaces. 2023;15(29):35732-35740. doi: 10.1021/acsami.3c06942.

Go to ACS Appl Mater Interfaces.

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