Preparation and Coefficient of Friction of YBa2Cu3O7-δ/Graphene Oxide Composites

Introduction

Compounds Ceramic materials have outstanding properties, such as low density, lower coefficient of friction (COF), low thermal expansion, high corrosion resistance and high hardness over a wide range of temperature. Because of these advantages of ceramic materials, their usages are increasing in wide applications. Thus they are promising candidates for wear-resistant components, especially under severe conditions. Many applications using the superconductor ceramic materials have been realized: magnetic applications such as levitation (flywheel) and transport applications (current transport and fault current limiter) (Ding, 2008). The superconducting transition temperature of pure metal is very low (in liquid helium), therefore, there is no utility value. The superconducting transition temperature of high temperature superconducting compounds YBa₂Cu₃O_7-δ (YBCO) is above 90 K, which can be realized at liquid nitrogen temperature. Therefore, it has strong theory and utility value to study the tribological property of high temperature superconducting ceramics (Yue, 1993). The solid lubricating materials should work long term effectively in a wide temperature range. YBCO belongs to oxide ceramics and has good tribological property at high temperatures above 600°C, but its ceramic brittleness and tribological property need to improve at room temperature (Grossin, 2005).

One of the merging self-lubrication materials is graphene, which has received significant attention due to its combination of remarkable mechanical, thermal, chemical, electrical, and recently, graphene has also shown great promise in tribological applications (Penkov, 2014; Berman, 2013). Weak van der Waal force between the 2D layers results into easy inter-layer sliding in multilayer graphene, leading to reduction in coefficient of friction (COF). This unique feature has motivated researchers to evaluate the potential of graphene in tribological applications. Also, the lubrication behavior of graphene is retained in harsh environment exposed to space irradiation, making it suitable for applications in out space (Harshal, 2014; Shah, 2015; Yi, 2013; Peng, 2013). Graphene nanoplatelets (GNPs) are excellent nanofiller for enhancing the tribological performance of ceramics. Under high contact pressures, GNPs is able to reduce friction and increase the wear resistance (Belmonte, 2013; Fan, 2010; Jan, 2014; Harshit 2014; Seiner, 2013; Hvizdo, 2013). As derivatives of graphene and possessing the same lamellar structure as graphene, Graphene oxide (GO) has also been investigated with respect to their tribological properties (Kim, 2015; Hang, 2015; Geetha, 2014). Wang et al. (Wang, 2012) have investigated the atomic-scale friction in GO using density functional theory calculation including dispersion corrections and revealed a strong dependence of friction on the interfacial interactions between GO layers, which can be tuned by structural and chemical modifications. Graphene-based materials with controllable friction could potentially find wide applications in nanolubrication in micro- and nanoelectromechanical systems (Yang, 2015).