In this study, the effect of ultrafine graphite and multi-walled carbon nanotube (CNT) additives on the performance of an external gear pump was investigated. Colloidal suspensions of each additive were created in ethanol with concentrations varying from 200 ppm to 1550 ppm, low enough that there was no significant change in the viscosity of the solution. These solutions were run through a hydraulic closed loop equipped with a 0.5 HP/1725 RPM external gear pump. Pressure, volumetric flow rate, temperature, and electric power consumption data were recorded for each additive concentration. An increase of up to 0.75 L/min in volumetric flow rates over the baseline ethanol case (additive concentration of 0 ppm) was observed for certain concentrations of graphite and CNTs, possibly suggesting reduced internal leakage or improved lubrication. As opposed to conventional viscosity modifiers which showed similar improvements, these nanostructrued additives had no effect on the viscosity of the working fluid. The surface morphology of the graphite and the CNTs was examined both prior to and after pumping the solutions through the gear pump by taking scanning electron microscopy (SEM) images of the additives after allowing a solution sample to evaporate on a microscope slide.

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