Promising commercial reinforcement to the nanodiamond/epoxy composite by grafting ammonium ions

A simple, economic, efficient and eco-friendly nanodiamond (ND) modifying method to reinforce the ND/epoxy composite for the industrialization of the high-performance ND/epoxy composite is always desired. In the present work, the ND was successfully modified only using aqueous ammonia through an easy-to-operate method by replacing the hydrogen atoms in the carboxyl group with ammonium ions. Ammonia, which is the only pollutant in the process, could be recycled. The modified ND/epoxy composite showed an overwhelming advantage over the neat epoxy or the ND/epoxy composite in storage modulus in their glassy state without any degradation of tensile strength, hardness and fracture toughness.