Structure Features and Properties of Graphene/Al2O3 Composite

[EN] Since its discovery, graphene has attracted worldwide attention in the scientific community owing to its unique combination of properties. Thus, graphene is an ideal second phase to improve the structure and properties of metal, ceramic and polymer composite materials. This work presents a comparative study of two types of alumina-graphene composites fabricated with two sizes of delta-Al2O3 powders, nanometer and submicrometer, reinforced by graphene nanoplatelets (GNPs) and consolidated with the spark plasma sintering technique. The microstructure, mechanical and tribological properties of Al2O3-GNPs composites are influenced by the grain size of the ceramic matrix. Hardness values improve notably. The maximum value reached was 27.4 GPa for a composite fabricated with nanometric alumina powders, which is about 27 % higher than that of the Al2O3 monolithic material. Also, the methodology of powder mixing has a fundamental importance in obtaining materials with high-level properties.This work has been supported by the Competitiveness Program National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russian Ministry of Education and Science No. 02. A 03.21.0005; the Russian Science Foundation No16 - 19 - 10213; the Spanish Ministry of Economy and Competitiveness project MAT2015 - 67586-C3-R. E. Klyatskina acknowledges the Valencian Government for her Post-Doc. Contract APOSTD/2014/046 and A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her contract RYC2016 - 20915.Klyatskina, E.; Borrell Tomás, MA.; Grigoriev, E.; Zholnin, A.; Salvador Moya, MD.; Stolyarov, V. (2018). Structure Features and Properties of Graphene/Al2O3 Composite. Journal of Ceramic Science and Technology. 9(3):215-223. https://doi.org/10.4416/JCST2018-00006S2152239

Handbook of physical quantities

Reliable and quickly accessible information concerning the physical phenomena and properties of various media is in great demand by many scientists in their everyday work. This extensive reference provides such information, presenting basic physical parameters and properties of substances employed in modern science and industry

Possibilities of Additive Technologies for the Manufacturing of Tooling from Corrosion-Resistant Steels in Order to Protect Parts Surfaces from Thermochemical Treatment

The structure and physical–mechanical properties of products made from powders of corrosion-resistant steel 12X18H10T by the laser-beam powder bed fusion (LB-PBF) and subsequent ion-plasma nitriding in the work were investigated. Comparative studies of the physical mechanical properties of specimens made by the LB-PBF and conventional method from steel of the same grade were carried out. The density of the specimens and the coefficient of linear thermal expansion (CLTE) after the LB-PBF are almost the same as those of the conventionally manufactured specimens. Our analysis of the obtained dilatograms in the temperature range from 20 to 600 °C showed that the CLTE of steel after the LB-PBF is within acceptable limits (18.6 × 10−6 1/°C). Their hardness, tensile strength, yield strength and elongation are higher than those of a conventionally manufactured specimen. The phase composition and structure of specimens of steel 12X18H10T made by the LB-PBF after the process of ion-plasma nitriding were investigated. The obtained results show that the mode of ion-plasma nitriding used in this case (stage 1—570 °C for 36 h; stage 2—540 °C for 12 h) does not lead to deterioration of the characteristics of the selected steel. A technological process for the manufacture of modified tooling from 12X18H10T steel by the LB-PBF was developed. It protects the surfaces that are not subject to nitriding and makes it possible to obtain a uniform high-quality nitrided layer on the working surface of the part made from spheroidal graphite iron.ISSN:2075-470

Magnetic properties of poly(p-xylylene)-Ni nanocomposites

The dependence of electrical and magnetic properties on structure of thin poly(p-xylylene) - nickel nanocomposite films with Ni concentrations from 5 to 30 vol.% was studied. It was found that metal concentration strongly affects size and oxidation state of the nanoparticles. Effect of the filler content on electrical and magnetic properties of the nanocomposites was revealed. These properties are determined by percolation phenomenon, with the percolation threshold value of about 10 vol.%. The well pronounced magnetic hysteresis as well as ferromagnetic ordering were observed at Ni content above the percolation threshold. The diagrams of magnetic properties of these composites as a function of composition and temperature were elaborated

Magnetic properties of poly(p-xylylene)-Ni nanocomposites

The dependence of electrical and magnetic properties on structure of thin poly(p-xylylene) - nickel nanocomposite films with Ni concentrations from 5 to 30 vol.% was studied. It was found that metal concentration strongly affects size and oxidation state of the nanoparticles. Effect of the filler content on electrical and magnetic properties of the nanocomposites was revealed. These properties are determined by percolation phenomenon, with the percolation threshold value of about 10 vol.%. The well pronounced magnetic hysteresis as well as ferromagnetic ordering were observed at Ni content above the percolation threshold. The diagrams of magnetic properties of these composites as a function of composition and temperature were elaborated