Floating CNx composites were prepared by pyrolysis of melamine in the presence of hollow glass microspheres (HGM) at a temperature of 550 °C. The resulting yellow cake was then extracted from the crucible, milled with a mortar and pestle, and washed by gravimetric separation in a separatory funnel to isolate the floating fraction of the composite. Synthesis conditions varying the amount of melamine (2-8 g) while maintaining a constant HGM content (2 g) were tested to assess how the yield and CNx content of the floating composite changed (Table ). Decreasing the HGM:melamine ratio introduced a composite yield vs. quality trade-off whereby loading the HGMs with more CNx resulted in a smaller fraction of the product with density low enough to float on water. By using a 1:1 ratio of HGM:melamine, 50% of the final product was useable floating composite with a CNx content of 32%, while using a 1:4 ratio of HGM:melamine produced a floating fraction of only 12% in the final product, but with a 43% CNx content. The HGM:melamine ratio was also found to have an influence on the size and morphology of the floating composite (Figure ). At an HGM:melamine ratio of 1:1, the composite appears to be primarily individual HGMs (Figure ) coated with a thin shell or small particles of CNx (Figure ). As the HGM:melamine ratio increased, so did the amount of CNx