Tribological properties of Cetyltrimethyl ammonium bromide modified CS as lubrication additive

The coal indirect liquefied diesel soot (Coal-to-liquids diesel soot, CS) was collected by a self-made soot trapper. CS was modified with cetyltrimethyl ammonium bromide (CTAB) and named as CS-CTAB. The tribological properties of CS and CS-CTAB in 10^#white oil(10^#WO) were tested on a WTM-2E controlled atmosphere miniature friction and wear testing machine. The morphology, composition, and tribological mechanism of CS and modified CS-CTAB were studied by using TEM, XPS, XRD, Raman, and other instruments. The results showed that CS modified by CTAB is wrapped and entangled in long chains. Their main structure components are all amorphous carbon with a small amount of graphite crystallites. The addition of CS-CTAB (0.8 wt%) significantly reduces both AFC and wear rate, with reductions of 32.9% for AFC, and 65.6% for wear rate compared to no additive. The anti-friction and anti-wear effect of CS is greatly improved after being modified by CTAB. Mechanism analysis shows that CS as a lubricant additive, acts as a micro-bearing in the friction process and falls off under the action of shear force to generate an independent graphite sheet, thus forming a graphite protective film on the surface of 304 stainless steel plate. However, CS has the defects of low graphitization degree, large particle size, and easy agglomeration. During friction, uneven adsorption of CS on the surface can worsen wear. However, CTAB modification can improve dispersion stability in 10^#WO and effectively reduce wear on the friction surface.