L.V. Santos

Very adherent CVD diamond film on modified molybdenum surface

In this work, studies have been carried out on surface modification on a pure molybdenum surface to enhance CVD diamond adherence. Pure molybdenum exhibits a phase transformation temperature close to that of diamond growth, but it is possible to obtain a surface modification by ion sub-implantation at an appropriate lower temperature without phase transformation. In this study, it was possible to create an appropriate interface by using appropriate ion compounds and impact energy on the substrate surface at a very narrow window of working temperature. This interface efficiently avoided carbon diffusion during diamond growth and also improved the chemical bond density between atoms from the interface and carbon from the onset of diamond nucleation. Diamond films from a few micrometers up to millimeters have been obtained with very good adherence. Characterization by XPS and small angle X-ray diffraction of this interface prior to diamond growth and after diamond nucleation reveals different compound contributions to the chemical bonds. Indentation and SEM analyses were also carried out.

Structural characterization by NMR of rifabutinol, a derivative of rifabutin.

Rifabutin, a naphthalenic ansamycin, is a specific inhibitor of bacterial DNA‐directed RNA polymerase and inhibits in vitro the replication of HIV‐1. The synthesis of rifabutinol by PtO2–NaBH4 reduction of rifabutin in ethanol is described. Full assignments in CDCl3 are presented of the 1H and 13C NMR resonance signals using two‐dimensional homonuclear and heteronuclear correlation techniques and selective proton decoupling methods. The three‐dimensional structure of the ansa‐chain of rifabutinol was calculated from NOE contacts and vicinal coupling constants, using a simulated annealing protocol starting from random coordinates. Measurements of the 13C T1 relaxation times of rifabutin in solution are consistent with a rigid ansa‐chain. Copyright

Studies of molybdenum surface modification for growth of adherent CVD diamond film

Surfaces with very poor mechanical and frictional properties can be improved, or even, acquire new properties similar to diamond if good adherent CVD diamond film is obtained on it. In this work, nitrogen ions were sub-implanted on pure molybdenum as a means to enhance CVD diamond film adherence. Deposition time from 2 up to 60 h were used for deposition of 10 to 400 µm thick CVD diamond films with very good adherence on sub-implanted molybdenum substrate. Characterizations were carried out by XPS, X-ray diffraction and nano indentation on prepared surfaces prior to diamond growth and after the onset nucleation. The ionic sub-implantation with nitrogen possibly assists in adhesion, with the creation of a thin layer of nitrates and complexes.

Plasma-assisted techniques for growing hard nanostructured coatings: An overview

Nano-structured coatings have recently attracted increasing interest because of the possibilities of synthesizing materials with unique properties, such as high hardness, toughness, wear resistance, optical transparency, making them technologically attractive for different applications from the industrial to biomedical. In the field of hard coatings, these materials can be grouped in two main classes: (1) hard multilayer and (2) hard nanocomposite coatings. The most common nano-structured coatings employed in hardness applications are based on carbides, nitrides, borides, and oxides of transition metals and of group III and IV elements. These coatings are frequently synthesized by plasma-assisted techniques due to their versatility, which enables the tailoring of nanocoating properties, the use of a variety of substrates, and ensures a high reproducibility of deposition conditions. This chapter presents an overview of the hard nanocoatings and the main plasma-assisted techniques for their synthesis. Among these techniques are highlighted plasma enhanced chemical vapor deposition, atomic layer deposition, and magnetron sputtering deposition. Characteristics of some hard coatings obtained by these techniques are described.