Effect of Nanocrystalline Diamond Films Deflection on Wear Observed in Reciprocating Sliding Tests

The present study deals with the tribological behavior of nanocrystalline diamond (NCD) films. The diamond films were deposited by microwave plasma enhanced chemical vapor deposition (MPCVD) in methane/hydrogen/air plasma on the Si(100) substrates. The tribological properties were studied by reciprocal sliding tests against Si3N4 balls. The depth profiles and surface morphology of the wear scars were investigated by means of mechanical profilometry and scanning electron microscopy (SEM). Various adaptation processes occur between contacting surfaces including asperity polishing, formation of carbonaceous tribolayer and ripple patterns on the wear scar surfaces. The film deflection is the specific form of adaptation decreasing contact pressure and, therefore, the damage (including wear) of both counter bodies. The deflection of NCD films in sliding tests can be related with the effect of fatigue

Polishing of Black and White CVD Grown Polycrystalline Diamond Coatings

Microwave plasma CVD growth can produce black and white varieties of polycrystalline diamond (PCD), depending on their as-grown purity. These two types of PCDs have been polished by mechanical and chemo-mechanical polishing respectively. It has been observed that initial roughness of 2.21μm for white PCD can be brought down to 175 nm after 70 hours of combined polishing, whereas, 85 hours of combined polishing could bring down the high initial roughness of 11.2μm for black PCD down to 546 nm at the end. Although, the material that was removed during polishing was higher for the black variety of PCD but it had lower polishing rate of 4nm/hr than white PCD (13nm/hr) during chemo-mechanical polishing. Such differential polishing rate was due to harder top polished surface of the black diamond than the white diamond. The nanoindentation study on the polished PCD surfaces revealed that the black PCD has a final nanohardness of 32.58±1 GPa whereas the white variety PCD had a polished surface nanohardness of 28.5±2 GPa. More conversion of diamond surface into harder amorphous sp3 than softer graphite during polishing action may have resulted such slow rate of anisotropic polishing for black diamond than white diamond

THE STATE OF LOCAL IMMUNITY OF THE ORAL CAVITY IN PERSONS WITH DISEASES OF MUCOUS MEMBRANE AND THE DIFFERENT DEGREE OF COLONIZATION OF THE STOMACH BY HELICOBACTER PYLORI BEFORE AND AFTER TREATMENT

The article presents the results of estimation of efficiency of complex treatment of diseases of the mucous membranes of the oral cavity in individuals with low, medium, high degrees of contamination of the stomach Helicobacter pylori structure of Helicobacter pylori-associated diseases of the mucous membranes of the oral cavity, assessment of the state of local immunity of oral cavity in this category of patients. The proposed scheme of general and local treatment of diseases of the mucous membranes of the oral cavity for these patients, the main stages of which should be: normalization of the microbial landscape of the mucous membranes of the oral cavity and mucous membranes of the gastrointestinal tract, restoration of acid-base balance of the oral cavity; prevention of reinfection of the mucous membranes of the oral cavity and gastrointestinal tract Helicobacter pylori

A comprehensive study of mechanical and chemo-mechanical polishing of CVD diamond

Generally growth surfaces of polycrystalline microwave plasma enhanced chemical vapor deposited (MPCVD) diamond are very rough in nature. So, it is necessary to planarize the surface in order to use them in different industrial applications. High quality polycrystalline diamond (PCD) has been grown by MPCVD process and afterwards the as grown surfaces of these diamonds were polished by mechanical and/or chemo mechanical techniques. The samples were characterized for roughness by non-contact profilometer, quality by Raman spectral analysis and surface morphology by SEM images. It is concluded that mechanical polishing alone can reduce the roughness if correct combination of abrasives are selected. (C) 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Functional Nano-Materials, 2016

Morphology of Diamond Layers Grown on Different Facets of Single Crystal Diamond Substrates by a Microwave Plasma CVD in CH4-H2-N2 Gas Mixtures

Epitaxial growth of diamond films on different facets of synthetic IIa-type single crystal (SC) high-pressure high temperature (HPHT) diamond substrate by a microwave plasma CVD in CH4-H2-N2 gas mixture with the high concentration (4%) of nitrogen is studied. A beveled SC diamond embraced with low-index {100}, {110}, {111}, {211}, and {311} faces was used as the substrate. Only the {100} face is found to sustain homoepitaxial growth at the present experimental parameters, while nanocrystalline diamond (NCD) films are produced on other planes. This observation is important for the choice of appropriate growth parameters, in particular, for the production of bi-layer or multilayer NCD-on-microcrystalline diamond (MCD) superhard coatings on tools when the deposition of continuous conformal NCD film on all facet is required. The development of the film morphology with growth time is examined with SEM. The structure of hillocks, with or without polycrystalline aggregates, that appear on {100} face is analyzed, and the stress field (up to 0.4 GPa) within the hillocks is evaluated based on high-resolution mapping of photoluminescence spectra of nitrogen-vacancy NV optical centers in the film

Growth of 4 `' diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

Polycrystalline diamond (PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition (MPCVD) at different process parameters, and their thermal conductivity (TC) is evaluated by a laser flash technique (LFT) in the temperature range of 230-380 K. The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon (a-C) presence in the spectra. Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples, respectively. TC, as high as 1950 +/- 230 W m(-1) K-1 at room temperature, is measured for the most perfect material. A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established

Influence of plastic deformation in processes of agglomeration of the diamond hybrid material on structure and hardness of CVD-diamond

Results of research of the "light" and "black" CVD diamond structure in hybrid material, which is the CVD diamond covered by polycrystalline diamond shell, are presented. Hardness of the initial CVD diamond and after high pressure-high temperature (HPHT) treatment is defined. Increase of hardness of the "black" CVD-diamond after HPHT-processing at 20 % was found. Electron microscopy was used to determine mechanism of the polycrystalline diamond compound shell binding with the CVD-diamond surface