Liquid-phase Deposition Of Ultrahard Carbon Films By Electrochemical Route

Diamond-like carbon films have received considerable interests owing to their unique mechanical, chemical, electronic and optical properties, such as low friction coefficient, chemical inertness, high electrical insulation, low electron affinity, high optical transparency in the infrared region, elevated thermal conductivity and high refractive index et al. ,Therefore, they can be applied as various protective coatings of optical windows, magnetic storage disks, car parts, biomedical coatings and micro-electromechaical devices. The characteristics of DLC films strongly depend on the deposition methods and conditions. The known methods are chemical vapor deposition and physical vapor deposition, such as ion-beam sputtering, filtered cathodic vacuum arc, mass-selected ion beam deposition, pulsed-laser deposition, plasma enhanced chemical vapor deposition ,electron cyclotron resonance chemical vapor deposition. All these methods have need for vacuum equipment. The complexity of the vapor deposition systems limits their using areas. The DLC films and diamond films have been applied in some fields, but there are still some technical problems to be solved, including adhesive strength between DLC films and substrates, uniform deposition of the films on three-dimensional shape substrates or with large deposition area and growth rate, and tribological properties of the DLC films which depend on the environments et al. On this reason, we attempt to solve these problems by adopting a liquid-phase electrochemical deposition technique in this study.Ultrehard carbon films were deposited on silicon and stainless steel substrates at atmospheric pressure and low temperature (60℃) by electrolysis in pure methanol, or with additive solution using a direct current pulsed power supply. The morphology,microstructure and friction and wear behavior of the deposited DLC films were analyzed using atomic force microscopy (AFM),scanning electron microscopy (SEM),transmission electron microscopy (TEM),transmission electron diffraction (TED),Raman spectroscopy,Fourier transformation infrared Spectrometry (FTIR) and the CERT test system. The main conclusions are summarized as followings:(1) For silicon substrate, because of introducing de-ionized water, the current density is rapidly enhanced, resulting in an increase of deposition rate up to 0.5μm/h. When the ratio of methanol to de-ionized water is 1:5, the deposited film is smooth and compact and composed of spherical grains with 200～400 nm in diameter by SEM observation. Raman D-line is...