Tailoring the nanostructure and graphitization of soot by metal nanoparticles in continuous nanofluid fuel pyrolysis

Nanofluid fuel has great potential application value in the field of internal combustion engines and aerospace ramjet due to its high energy density, but the roles of metal nanoparticles in governing carbonaceous product nanostructures during the application of nanofluid fuels were still poorly unclear. In this work, the central objective was to elucidate how different metal nanoparticles actively modulate the nanostructure and graphitization of pyrolytic soot. The correlations between metal nanoparticle and soot characteristic parameters were established by integrating detailed analysis. The results indicated that different metal nanoparticles can serve as sites for soot nucleation and growth, thereby leading to varying degrees of enhancement in nanostructure ordering and graphitization degree. With the exception of the Al nanoparticle condition, soot morphology, nanostructure, and graphitization degree exhibited a positive correlation with the concentration of metal nanoparticles addition. Moreover, heterogeneous nucleation induced by the metal nanoparticles improved the uniformity of primary soot particle size. Although the addition of metal nanoparticles increased soot graphitization degree, the catalytic effects arising from the incorporation of Al, Cu, and CuO also significantly accelerated the oxidation rate of the pyrolysis products. Overall, this work was of great significance for optimizing advanced fuel systems and managing carbonaceous emissions.