Abstract
Tetraalkylammonium salts have larger ions than metal ions, which can greatly change the interlayer space and energy, and then potentially tune the properties of graphite. In this work, various graphite intercalation compounds (GICs) have been synthesized by intercalating tetraoctylammonium bromide (TOAB) ions into graphite through electrochemical interactions under different reduction potentials. Different degrees of expansion between graphite layers as well as their corresponding structures and topographies have been characterized by different analytical techniques. The nanoscale friction and wear properties of these GICs have been investigated by AFM-based nanofrictional and scratch tests. The results show that electrochemical intercalation using tetraalkylammonium salts with different interaction potentials can tune the friction and wear properties of graphite. Under relatively large applied loads of AFM tips, friction increase and wear can be easier to occur with the increase of the intercalation potential. It is inferred that the increases of both the interlayer space of graphite and the number of ions on the surface give rise to puckered effect and formation of rougher surfaces. This work gives us deep insight into the friction and wear properties of GICs as composite lubrication materials, which would be of great help for material design and preparation.
Highlights
Graphite is a good choice for intercalation host and has many unique applications, such as highly conductive materials and battery electrodes [1,2,3]
The synthesized Graphite intercalation compounds (GICs) were baked for 24 h in the vacuum drying oven in order to remove the residual solvent
The sample surfaces become more uneven with the increase of intercalation potential, and obvious expansions of the edges can be observed after intercalations
Summary
Graphite is a good choice for intercalation host and has many unique applications, such as highly conductive materials and battery electrodes [1,2,3]. It shears along the direction parallel to the planes due to weak van der Waals interactions between layers, resulting in excellent lubricant properties [4,5,6]. The distance between the layers in GICs can be changed, and the interlayer force of graphite can be modified. There have been dense studies about the syntheses, compositions, and properties of GICs with various intercalate species [9,10,11]. The syntheses methods of GICs include electrochemical and chemical methods, and the GICs can be produced by oxidation or reduction reactions [12,13,14,15]
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