Development of Solution-Based Diamond-Like Carbon Coatings, 18-R8177
Principal Investigators
Vasiliki Z. Poenitzsch
Kent E. Coulter
Inclusive Dates: 07/14/10 – 11/14/10
Background — Because of their excellent mechanical and tribological properties, diamond-like carbon (DLC) coatings are widely used as protective overcoats in various industries ranging from medical to automotive sectors. However, the vacuum deposition processes traditionally used to prepare DLC coatings considerably limit the realization of many applications. The limitations of these common vacuum deposition techniques include (i) high costs, (ii) slow rates of film production, (iii) limited ultimate film thickness, (iv) limited areas based on the size of the reaction chamber, (v) restricted vacuum-compatible substrate choices, and (vi) inability to combine with reinforcing materials. This project investigated an innovative non-vacuum-based process of fabricating DLC coatings that addresses these limitations.
Approach — The primary objective of this research project was to develop an atmospheric solution-based processing technology for fabricating diamond-like carbon (s-DLC) coatings. Another objective was to obtain preliminary data to convince potential clients that such a processing technology is a promising candidate for depositing DLC on components with large dimensions.
Accomplishments — This project has resulted in the proof-of-concept development of an atmospheric solution-based processing technology for fabricating DLC coatings. This method used chemical synthesis of hydrocarbon polymers possessing diamond-like structure at the atomic level and the subsequent pyrolysis and potentially photolysis to convert the polymers to diamond-like carbon. A scalable and affordable method was established to reproducibly synthesize carbon polymers possessing a diamond-like structure by reducing α-α-α-trichlorotoluene at room temperature and normal atmospheric conditions. A post-synthesis purification procedure was developed to further refine the raw polymer products. The conversion of the polymer precursor to s-DLC was investigated as a function of temperature. A deeper understanding into the process-property relationship for preparation of sDLC coatings was obtained. Finally, the chemical composition, microstructure and properties of the s-DLC coatings were examined with and compared to those of traditional DLC using FTIR and Raman spectroscopy, electron energy loss spectroscopy (EELS), scanning electron microscopy (SEM), electrical impedance and nanoindentation measurements. These resultant sDLC coatings exhibited properties akin to those of traditional vacuum-prepared DLC. This new solution-based processing route opens doors for many applications of DLC films (e.g. protective coatings, friction reduction, corrosion resistance, etc.) with substrates previously impractical due to their size, geometry or incompatibility with vacuum processes.
