Amongst the different elements constituting the universe, carbon has a preferential position. Indeed, this element is not only observed within the composition of all living species, but it has also a great importance for many industrial outlets. One of the most important applications, is the use of a particular structure of amorphous carbon (i.e. diamond-like carbon) as super-hard and wear resistant coating of various substrates (i.e. drill bits, hard-disk platters and hard-disk read heads, parts of motorcycles engines…). Last years, numerous studies were driven in order to develop new materials with superlative mechanical properties. In particular, the synthesis of the elusive beta-C3N4 phase has been extensively investigated since the prediction of its highly interesting physical properties by Liu and Cohen in 1989. Despites the numerous elaborate techniques attempted to date, mixed phase layers are quite often obtained and the fully crystallineBeta-C3N4 phase remains very difficult to achieve. However, even amorphous carbon nitride compounds may have suitable physical properties for the use in many tribological applications. In this work, we have studied the possibility of using the simultaneous implantation of carbon and nitrogen in copper in order to synthesise carbon nitride compounds. This method seemed to be a good solution for the following reasons: carbon and nitrogen have to form precipitates at high fluence due to their very low solubility inside copper; the interaction between carbon and nitrogen atoms during the implantation process was enhanced due to their simultaneous arrival inside copper; the high compressive stress applied by the host matrix on the precipitates favoured compact growing structures; and implantation at medium energies (typically 600 keV) allowed to deeply burry the atoms (typically 600 nm) in copper matrix in order to avoid the nitrogen migration and surface release processes. The influence of temperature on the carbon nitride structures formed during the implantation process was studied. For that purpose we performed several implantations at 25, 250, 350 or 450°C with a fluence fixed at 1 × 1E18 at/cm². The implanted samples were characterised by NRA, XPS, TEM and nano-indentation in order to study the carbon and nitrogen depth profiles, C−N type bonds, structure of carbon nitride compounds and mechanical properties, respectively. Experimental results are presented and discussed in this manuscript. Then we give some conclusions and perspectives about this work. Note that this thesis has been completed in a laboratory of nuclear reaction analysis. Special attention was consequently given to the development of a NRA method allowing to simultaneously depth profile all light elements contained in a sample. The experimental setup of acquisition and the method of data processing are described in this work.
|Date of Award||15 Oct 2009|
|Supervisor||Guy Terwagne (Supervisor), Stephen DONNELLY (Jury), Nathalie Moncoffre (Jury), Pierre Louette (Jury) & Stephane Lucas (President)|