Process for producing nanomaterials such as graphenes, graphene composites, magnesium oxide, magnesium hydroxides and other nanomaterials by high heat vaporization and rapid cooling. In some of the preferred embodiments, the high heat is produced by an oxidation-reduction reaction of carbon dioxide and magnesium as the primary reactants, although additional materials such as reaction catalysts, control agents, or composite materials can be included in the reaction, if desired. The reaction also produces nanomaterials from a variety of other input materials, and by varying the process parameters, the type and morphology of the carbon nanoproducts and other nanoproducts can be controlled. The reaction products include novel nanocrystals of MgO (percilase) and MgAl2O4 (spinels) as well as composites of these nanocrystals with multiple layers of graphene deposited on or intercalated with them.