Influence of the bilayer thickness of nanostructured multilayer MoN/CrN coating on its microstructure,hardness, and elemental composition

Multilayer nanostructured coatings consisting of alternating MoN and CrN layers were obtained by vacuum cathode evaporation under various conditions of deposition. The transition from micron sizes of bilayers to the nanometer scale in the coatings under investigation leads to an increase in hardness from 15 to 35.5 GPa (with a layer thickness of about 35 nm). At the same time, when the number of bilayers in the coating decreases, the average Vickers hardness increases from 1267 HV_0.05 to 3307 HV_0.05. An increase in the value of the potential supplied to the substrate from–20 to–150 V leads to the formation of growth textures in coating layers with the [100] axis, and to an increase in the intensity of reflections with increasing bilayer thickness. Elemental analysis carried out with the help of Rutherford backscattering, secondary ion mass spectrometry and energy dispersion spectra showed a good separation of the MoN and CrN layers near the surface of the coatings.     

Recrystallization and formation of spheroidal gold particles in amorphous-like AlN–TiB<Subscript>2</Subscript>–TiSi<Subscript>2</Subscript> coatings after annealing and subsequent implantation

The recrystallization of the structure of an X-ray amorphous AlN–TiB₂–TiSi₂ coating containing short-range order regions with characteristic sizes of 0.8–1.0 nm has been performed using a negative gold ion (Au^–) beam and high-temperature annealing. Direct measurements using methods of high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectral (EDXS) microanalysis have demonstrated that thermal annealing at a temperature of 1300°C in air results in the formation of nanoscale (10–15 nm) phases AlN, AlB₂, Al₃O₃, and TiO₂, whereas the ion implantation of negative ions Au^– leads to a fragmentation (decrease in the size) of nanograins to 2–5 nm with the formation of spheroidal gold nanocrystallites a few nanometers in size, as well as to the formation of an amorphous oxide film in the depth (near-surface layer) of the coating due to ballistic ion mixing and collision cascades.     

Hole Localization in Thallium Nitrate (I)

Russian Physics Journal - Using the EPR method, an identification of paramagnetic centers formed in TlNO3 under γ-irradiation at 77 and 300 K is performed. Their spectral characteristics,...     

Effect of electron irradiation on the mechanical and thermal properties of some polymer materials

The effect of electron irradiation on the mechanical properties (deformability) of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyimide (PI), and Fenilon (Fe) films, as well as the thermal properties (heat conductivity and capacity) of PTFE is studied experimentally. The thickness of the films was 40–50 m. Mechanical tests showed that polyimide films were more resistant to radiation than the other films. The investigation of the changes in the thermal properties of PTFE due to electron irradiation revealed that the phase transitions observed at temperatures of 293 and 303 K in unirradiated PTFE were shifted to lower temperature regions.Abai Alma-Ata State University, Kazakhstan. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 683–689, 1998.     

Effect of the deposition parameters on the structure and physicochemical properties of protective Al2O3 coatings

Three series of Al₂O₃ coating samples are fabricated by microarc oxidation under various deposition conditions and are studied by scanning electron microscopy (SEM) in combination with energy-dispersive x-ray spectroscopy (EDXS), Rutherford backscattering, and X-ray diffraction. Defects and pores in the coatings are analyzed by positron annihilation spectroscopy at room temperature without vacuum. No nanometer pores are detected in the coatings. When changing the electrolyte-plasma oxidation conditions, one can change the concentration and the ratio of the types of vacancy defects in these Al₂O₃ coatings.     

Microstructure and Mechanical Properties of Multilayer α-AlN/α-BCN Coating as Functions of the Current Density during Sputtering of a B<Subscript>4</Subscript>C Target

Multilayer AlN/BCN coating of nanometer scale have been prepared by magnetron sputtering of Al and B₄C targets in an argon–nitrogen atmosphere during deposition on a Si substrate. These coating have an X-ray amorphous structure and the maximum Knoop hardness of 27 GPa (at the current density 100 mA). The first-principle molecular dynamics calculations show that the B4–BN layer is dynamically unstable; thus, it will not be epitaxial and will be amorphous or have a structure different from the B4–BN structure. The thermal vacuum annealing from 600 to 800°C of samples with multilayer nanosized coating leads to the decrease in the Knoop hardness to 18 GPa; however, the coating structure is retained X-ray amorphous.     

Effect of electron irradiation on the physicochemical processes in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6+<Emphasis Type="Italic">x</Emphasis></Subscript> high-temperature ceramics

The influence of irradiation by 2-MeV electrons at integral doses of 0.1, 0.3, 1.5, and 3.0 MGy on the physicochemical processes in YBa₂Cu₃O_6+x polycrystalline samples is investigated. At different stages of irradiation, processes occurring in the samples exert an opposing effect on the matrix and near-surface regions of the material. Irradiation with doses D<1.5 MGy strengthens bonds in the intergranular spacer, which weaken because of a reduction in the potential surface barrier for oxygen migration to vacant sites. This results in ordering of the oxygen sublattice in near-surface regions. Irradiation with doses D>1.5 MGy causes damage on the grain surface, which enhances oxygen diffusion from the bulk and, thus, leads to material degradation.