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Chemical vapor deposited diamond is a new potential biomedical material which has the advantage of chemical inertness, extreme hardness and low coefficient of friction, among others. In orthopedics and maxillofacial surgery, these properties could improve implant performance, reducing metallic corrosion, particle wear, inflammatory reactions and bone loss. In the present study, two types of chemical vapor deposition (CVD) diamonds have been analyzed: microcrystalline diamonds (MD) and nanocrystalline diamonds (ND), both produced by hot-filament chemical vapor deposition. The diamond tubes were previously characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman scattering spectroscopy (RSS). The aim of this study was to verify the interface between bone and MD and ND, surgically implanted in the femoral diaphysis of Wistar rats, after 4 and 8 weeks. The outcome was evaluated by scanning electron and optical microscopy using a semi quantitative method. The results suggest that nanocrystalline diamonds (ND) elicits a richer biological response than microcrystalline diamonds (MD) when in interaction with bone.

A hot-filament chemical vapor deposition system fed with ethanol highly diluted in hydrogen was employed to grow self-supported diamond tubes with external diameter to wall thickness aspect ratio between ∼5 and ∼60, and 30 mm in length. Tungsten wires of diameters between 238 and 586 μm were used as substrates for the deposition, and were subsequently completely removed by etching, to leave stress-free diamond tubes, as demonstrated by micro-Raman spectroscopy. Scanning electron microscopy revealed cross-sections with diamond grains growing radially, forming well-faceted top-surface grains on the tube's external surface.

In this work, we undertook a unique study of the growth kinetics of diamond in a hot-filament chemical vapor deposition (HF-CVD) reactor fed with the mixture C2H5OH+H2+Ne, varying the concentration of Ne from 0% vol. to 60% vol. Images obtained by scanning electron microscopy (SEM) show that the addition of neon influenced the grain morphology, but diamond films with well-defined crystalline facets and good Raman quality were obtained up to a concentration of 60% vol. Ne. We verified that neon changes the diamond growth mechanism in the space between the grains, probably by the minimization of the hydrogenation kinetics in these regions. There is an apparent increase in the grain size and an increase in the flaws between the grains. The presence of Ne in the feed mixture also induces a broadening of the Raman peak characteristic of diamond, and this broadening may be related to an increase in the density of vacancies within the diamond grains.

We show that the electrical properties of heavily boron-doped polycrystalline chemical vapor-deposited diamond films are modified by post-deposition thermal annealing with slow heating and cooling rates. We found that the boron effective activation energy increased after heating and cooling cycles in the temperature range of 300–673 K. The improvement also depends on the doping level. Samples with a resistivity of 6.41 mΩ·cm, 3.84 mΩ·cm and 0.826 mΩ·cm showed improvements of 6.4, 11.5 and 205%, respectively. Scanning tunneling microscopy (STM) images show that there were no exceptional changes in film morphology produced by the annealing processes, only an apparent cleaning of the surface at the nanometer scale.

Some studies about application devices that have been developed in our laboratory are presented. Some characterizations show the quality of free-standing CVD diamond film. An improvement of CVD diamond burrs will be presented, including laser cutting of diamond film, processes for soldering the film to the stainless steel tips, and statistical performance of the burrs. Basic studies were carried out in order to improve the film quality. These results gave us support for the scaling-up of a hot-filament system for the manufacturing of CVD diamond burrs.

Columnar grain structure is always observed in CVD-diamond growth and is an important parameter to identify the morphology of thin and thick films. Structure defects, aspects of onset nucleation and film growth mechanisms can also be related to columnar growth. In this work we focused our attention on the columnar structure of CVD-diamond grown on irregular surfaces. We observed that there is a relationship among curvature radius of the substrate surface, the spread of the column volume and the growth rate of the diamond film. Growth rates on spherical surfaces of around 0.5 mm curvature radius have been observed to be up to three times bigger than the growth rates on planar surfaces. Also, the grain size distribution on planar and on the corner surfaces as a function of the growth rate has been studied. Characterization with scanning electron microscopy (SEM) and Raman scattering spectroscopy (RSS) has been performed.