Vol 39, No 6 (2017)

A critical analysis was made of the Oliver and Pharr method for determination of the hardness and elastic moduli of materials by instrumented indentations with the continuous recording of the P–hdiagrams (P is the force acting on the indenter, h is the approach of the indenter and a sample). Mistakes and insufficient justification were revealed in the basic theoretical relations of this method. In particular, this refers to an incorrect definition of the depth of the elastic contact h_c, which is the base of these relalations. New refined basic relations and formulas for the determination of hardness and elastic modulus are given, in which the above defects are eliminated and which are based only on the assumption of elastic unloading of the indenter according to the classic theories of the elastic contact. In addition to the foregoing, using the data of the P–h diagram measured in the arbitrary laboratory coordinate system, an improved method of the stable determination of the contact stiffness S = dP/dh at the P–h diagram position have been proposed in the commonly accepted theoretical coordinate system in which its basic classic model relations are recorded. These refinements have been derived without additional assumptions to hypotheses to the Oliver and Pharr method and additional experimental measurements.

Microwave attenuation in samples of a diamond micron powder based composite material structured by a nanocarbon binder vapor-deposited at subatmospheric pressure is measured at frequencies of 34.09 to 34.19 GHz in a cylindrical resonator at H₁₁₁ mode. Return losses are determined from the measurements. Volume resistivity of the samples is measured. The potential of using diamond-containing structured composite materials as microwave radiation absorbers is demonstrated.

Shungite adsorption properties to remove higher alcohols and other impurities from water–alcohol solutions is studied by the methods of nitrogen adsorption, thermogravimetric analysis, wetting, temperature-programmed desorption mass spectrometry, and FTIR spectroscopy. Shungite is shown to be able to effectively sorb impurities from water-alcohol solutions to form fairly strong adsorption systems. Heat treatment 180°C in vacuum results in almost complete decomposition of the adsorption systems, thus providing recovery and a slight increase of the specific surface and sorptive volume of shungite. The present findings demonstrate the theoretical possibility of recovery of adsorption centers on the shungite surface, which would extend its usable life as a sorbent.

A study of the mechanism of mechanical polishing of optoelectronic components made of crystalline materials has demonstrated that the removal rate in polishing decreases with increasing workpiece material’s bond energy and energy of transfer and grows with increasing thermal conductivity coefficient of the workpiece material, sliding distance of a workpiece surface element against the polishing pad surface, and Lifshitz force. The ratio between the volumetric wear coefficient and thermal diffusivity of the workpiece material is shown to depend on specific heat capacity and energy of transfer.

We would like to inform you that a sad mistake was made in one of our articles in “Journal of Superhaed Materials”, 2017, vol. 39, no. 5, pp. 299–307. The article is “Structure and Properties of Superhard Materials Based on Aluminum Dodecaboride α-AlB₁₂” by T. A. Prikhna, P. P. Barvitskyi, M. B. Karpets, V. B. Muratov, V. B. Sverdun, P. Khaber, V. V. Kartuzov, V. E. Moshchil’, S. N. Dub, M. G. Loshak, L. I. Aleksandrova,V. V. Kovylyaev, V. V. Garbuz, and A. A. Marchenko.

Thus, the author’s name P. Khaber should be replaced by R. Haber.