Vol 40, No 1 (2018)

Using the activated HPHT-sintering of diamond powders with addition of n-layered graphene of the N002-PDR grade, was produced a novel superhard composite polycrystalline material that does not contain free silicon and has a strength by 35% higher and wear-resistance by 7 times higher than samples produced without addition of graphene.

The comparison of the formation processes of volatile products at heating mixtures of detonation nanodiamonds with perfluorochemical alcohol and nanodiamonds subjected to directed chemical modification with perfluorochemical alcohol was made using the thermodesorption mass-spectrometry. A change of the destruction mechanism and increase of the thermostability of perfluorochemical alcohol by ~ 100°C as a result of a directional chemical modification was revealed, the most possible models of functionalization through hydrogen and covalent bonds of the hydroxyl group of fluorine radicals with carboxyl groups of surfaces of nanodiamond particles are suggested, the degrees of the functionalization and energy of the desorption activation of the products of the destruction functionalized molecules are assessed.

In the present study, HFCVD nanocrystalline, microcrystalline and boron-doped nanocrystalline diamond coatings have been deposited on titanium alloy. The effect of boron doping on coefficient of friction and residual stresses of diamond coatings have been studied. The tribological characteristics of the aforementioned three coatings on Ti–6Al–4V substrates were studied using ball on disc micro-tribometer, the thickness of the coatings being 3 μm. The coated Ti–6Al–4V discs were slid against alumina (Al₂O₃) balls with normal load ranging from 1 to 10 N. The boron-doped NCD coated sample disc was found to possess the lowest average coefficient of friction ~ 0.0804 while the undoped NCD and MCD coated sample discs were found to possess the average coefficients of friction of ~ 0.143 and ~ 0.283, respectively. Raman spectroscopy studies revealed that the residual stresses in boron-doped nanocrystalline coatings were tensile in nature, while the residual stresses in undoped NCD and MCD were found to be of compressive nature.

In this work Sn and Bi were added to Cu–Sn–P–Ce for improving its microstructures and properties. Structures of the three matrices were investigated by XRD, SEM and EDS. The Cu₄₁Sn₁₁ became the main microstructure with some pores, the grinding ratio increased, and the grinding efficiency improved slightly with the addition of Sn to Cu–Sn–P–Ce. Bi was distributed in the form of simple substance, the grinding ratio increased, and the grinding efficiency greatly reduced with the addition of Bi to Cu–Sn–P–Ce.

The investigation of the mechanism of mechanical polishing of optoelectronic components made of crystalline materials has demonstrated that the machined surface roughness parameters grow linearly with increasing most probable values of debris particle size and surface area, unit cell volume, and surface area of the crystal plane machined. The surface roughness parameters are shown to be inversely proportional to the energy spent for the debris particle formation. The relative surface roughness of the polished silicon carbide, gallium nitride, aluminum nitride, and sapphire workpieces is represented by the following ratio: 0.68: 0.67: 0.63: 1.00.

The influence of the percentage content and dispersion of natural diamond powders used as fillers on the properties of a tin- and copper-based composite material for abrasive applications has been studied. It has been experimentally found out that adding these fillers in certain amounts to the composite has a beneficial effect on the physical-mechanical properties and performance of the resulting material.

It is reported that a new chemical compound of an extra elongated shape has been found in the conventional granular structure of T5K10 hard alloy produced by pressureless sintering in vacuum at 1500°C followed by annealing in vacuum at 1200°C and isothermal holding for 7 h.