Tribological properties of vacuum arc Cr-O-N coatings in macro- and microscale

In this paper the tribological properties of Cr-O-N coatings deposited using vacuum arc plasma flux in macro- (sphere-on-disc test) and microscale (AFM-atomic force microscopy) are investigated. It was found that the specific wear rate determined in AFM measurements (micro scale) is approximately 2 orders higher than the macroscale. This is probably due to much higher Hertzian contact stress.Исследовались трибологические свойства Cr-O-N-покрытий, осаждённых из потока вакуумно-дуговой плазмы на макро- (тест сфера-на-диске) и микроуровне (AСM-атомно-силовая микроскопия). Было установлено, что удельная скорость износа в измерениях AСM (микроуровень) примерно на 2 порядка выше, чем в макромасштабе. Это, вероятно, связано с гораздо более высокими контактными напряжениями.Досліджувалися трибологічні властивості Cr-O-N-покриттів, осаджених з потоку вакуумно-дугової плазми на макро- (тест сфера-на-диску) і мікрорівні (AСM-атомно-силова мікроскопія). Було встановлено, що питома швидкість зносу у вимірюваннях AСM (мікрорівень) приблизно на 2 порядки вище, ніж в макромасштабі. Це, ймовірно, пов'язано з набагато більш високими контактними напруженнями

Structure and magnetic properties of the spinel-polymer composites

The development of the functional magnetic composites with determined properties is important task for modern material sciences. Control of magnetic and electrodynamic properties realized by the ceramic/polymer composites preparation. Conduction of the investigations of the correlation between chemical composition of the fillers (magnetic powders) and their concentration in the polymer matrix is the best way for solving this task. Two- and tree-component spinel-polymer composites were produced by thermal pressing. As spinels, CoFe2O4 (CF) and Ni0.4Cu0.2Zn0.4Fe2O4 (NCZFO) were used. As a polymer, FEP was used. The concentration of the spinels in the polymer matrix was fixed at 20 mass.%. Investigation of the structural features and magnetic properties were carried out. The impact of the chemical composition and phase ratio of the composites on crystal structure, microstructure, and magnetic properties were established. Magnetic measurements were performed at 300 and 10 K in the fields up to 70 kOe. It was demonstrated that the synergetic effect of ceramic composites violates of the principle of additivity in two-phase ceramic composites. The impact of the polymer matrix on magnetic properties was demonstrated. It opens new perspectives for practical applications of such kind of materials

Development and study of lightweight recycled composite materials based on linear low-density polyethylene and W for radiation application

Composite materials based on a polymer matrix of linear low-density polyethylene (LLDPE) and W were produced by thermal pressing. The content of W in the samples varied from 0 to 70 %. The recycling properties of LLDPE are demonstrated in this study, which significantly helped to reduce the defects. The microstructure of the composites consists of well-defined W grains covered by elastic LLDPE fibers. A homogeneous distribution of tungsten in the polymer matrix was observed for sample W70. The EDX analysis showed the presence of tungsten and carbon (from the polymer component). The XRD analysis confirms the increase in W content in the samples. The FTIR spectra of the composites showed an increase in the content of terminal methyl groups, a decrease in the molecular weight, and a decrease in the degree of crystallinity of the polyethylene matrix with an increase in the W content in the composite. The sample with 70 % W content has the highest effective density (2.61 g/cm3). The sample relative density ranges from 93.3 to 97.7 %. The porosity of LLDPE-W composites does not exceed 7 %. Gamma radiation shielding efficiency parameters such as LAC, HVL, and MFP were calculated using Phy-X/PSD. The radiation source was Co60, with an emission range of 0.8–2.5 MeV. As the gamma energy increases, it is observed that the values of all the parameters deteriorate. However, the sample with a maximum W content of 70 % has the best values of LAC, HVL, and MFP among the other samples