Credit: © 2009 ACS

Advanced high-speed propulsion systems will require environmentally friendly fuels that offer high energy densities, short ignition times and low costs. However, rather than developing new fuels, many researchers are trying to improve the performance of existing fuels by adding low concentrations of colloids to boost performance. Now Richard Yetter, Ilhan Aksay and co-workers at Pennsylvania State University and Princeton University have shown that the combustion performance of nitromethane can be greatly enhanced by adding functionalized graphene sheets (ACS Nano doi:10.1021/nn901006w; 2009).

The Penn State–Princeton team compared the performance of neat nitromethane with samples that contained aluminium oxyhydroxide, silica nanoparticles or functionalized graphene sheets. All three additives lowered the ignition temperature and increased the burning rate, with the functionalized graphene sheets leading to the biggest increase. The change in the burning rate relative to neat nitromethane increased with the concentration of the additives and decreased with pressure. The figure shows the burn front (the diagonal line) at two-second intervals for the four fuel systems, with the neat fuel on the left and the graphene-enhanced fuel on the right.

The graphene sheets are efficient catalysts because they are easily dispersed and have large surface areas in contact with the fuel. Their high thermal and radiation conductivities might also enhance heat transfer during combustion.