Nanoparticles bring diamond properties to coatings New coatings embedded with nanodiamonds promise to increase engine efficiency while reducing harmful emissions. Small loadings of nano-scale diamond can improve wear resistance, coefficient of friction and thermal conductivity of engine components. Industrial Technologies © Lars Pleth Nielsen Internal combustion engines convert the chemical energy in fuels into kinetic energy to move parts under high temperatures and pressures and rapid cycling conditions. Inefficiency increases fuel consumption and associated emissions. A European consortium developed super-lubricating and wear-resistant coatings based on nano-structured diamond within the project ADEC (Advanced low friction engine coating). The new technology covered development of functionalised diamond nanoparticles and their dispersion in a metal matrix, novel electroplating processes, plasma electrolytic oxidation, metal doped diamond-like carbon coatings (DLC) and appropriate materials for the pistons and piston rings. Researchers successfully functionalised nanodiamonds with hydrogen atoms. These functional groups represent attachment points between the nanoparticles and the material. With strong zeta potential, they formed stable dispersions of nanodiamond particles in a slightly acidic pH region. The development included both surface re-functionalisation of existing commercial nanodiamond grades and further processing steps to introduce nanodiamond particles into an aqueous dispersion form. After treating nanodiamonds with hydrogen, researchers deposited them into nickel platings. Nanodiamond addition into this metal plating outperformed the state of the art due to tailoring the purity and size distribution of the nanoparticles. Except for nanodiamonds, researchers also experimented with other dispersion elements into nickel platings such as hexagonal boron nitride, calcium fluoride and silicon carbide. Tests of dispersion coatings on a cylinder wall demonstrated promising results. The team then experimented with doping diamond-like carbon coatings with silicon and wolfram, thereby obtaining coatings that can tolerate higher temperatures. Tests on pistons and piston rings revealed reduced friction and wear of the engine, also allowing significant reduction of the cylinder operating temperature. ADEC's super-lubricating, highly wear-resistant diamond nanoparticle-based coatings for use in combustion engines will enhance component lifetimes while reducing pollutants such as carbon dioxide. The technology is promising and will significantly increase the competitive position of the small and medium-sized enterprises involved in the project while simultaneously supporting EU objectives on fuel economy and emissions. Keywords Nanoparticles, coatings, nanodiamonds, engine, super-lubricating, wear-resistant, ADEC
