Materials Science Forum Vol. 782

Abstract: A composite material of graphite/polystyrene sulfonate was prepared by solvothermal method. The dissolution of polystyrene sulfonate in water ensures homogeneous distributions of graphite and creates composition material at room temperatures. Water removing by the drying, permit to prepare films. Structure of the film was analyzed by scanning electron microscopy. The influence of different ratio between graphite and polystyrene sulfonate is discussed.

Abstract: Copper (II) oxide graphene composite materials were prepared on the electrode surface at the solution of CuCl₂. The resulting composite material was characterized by cyclic voltammetry on surface of the glassy carbon electrode. Prepared copper (II) oxide graphene nanocomposite was scraped from the electrode surface and was measured Raman spectra by optical tweezers combined with micro Raman spectroscopy. This composite nanomaterial was used on determination of glucose and can be used to construct bio batteries too.

Abstract: The YBCO bulk single-grain superconductors were prepared by Top-Seeded Melt-Growth (TSMG) process. Y₂BaCuO₅ (Y211) fine powder was added to YBa₂Cu₃O_7-δ (Y123) nominal composition. Powder refinement was characterized by X-ray powder difractometry, laser granulometry and scanning electron microscopy. The system behaviour was characterized by thermal analysis. Microstructure of prepared samples was studied by polarized light microscopy. The influence of Y211 addition the sample microstructures are shown.

Abstract: YBCO (YBa₂Cu₃O₇/ Y₂BaCuO₅) bulk single-grain superconductors were prepared by Top-Seeded Melt-Growth (TSMG) process. CeO₂, BaCeO₃ and BaO₂ powders were added to nominal composition Y_1.5Ba₂Cu₃O_y (Y-123) with the aim to refine Y₂BaCuO₅ (Y-211) secondary particles, which provide pining. Added powders were refined by friction milling. The system behaviour was characterized by thermal analyses. Microstructure of prepared samples was studied by polarized light microscopy and the influence of additions is described.

Abstract: The main limitation of bulk metallic glasses for their application as structural materials is the large brittleness under the external loading. We analyzed the failure characteristics of Co₄₃Fe₂₀Ta_5.5B_31.5 (at.%) bulk metallic glass deformed in a compression at the room temperature and a low strain rate. Under loading the amorphous structure can store high elastic energy. During the failure this energy is released and the alloy breaks into small particles or powder exhibiting a fragmentation mode. The nanoscale fracture surface morphology respects the micromechanisms of failure of the amorphous structure. The fracture surface consists of a smooth mirror cleavage zone and a river pattern zone with the nanosized dimples arranged in lines respecting the periodic corrugation zones oriented perpendicular to the crack propagation direction.

Abstract: Metallic glasses subjected to bending loads often exhibit the significant strength through the creation of multiple shear bands. Amorphous metallic glasses in the form of thin ribbon (about 40 μm in thickness) can be bent to large curvatures without the failure. The thickness of metallic glass is also an important factor that influences the exceptional properties of these materials. The shear bend formation under bending of Fe₄₀Ni₄₀B₂₀ (at. %) amorphous ribbon was studied. There is highly localized plastic deformation in shear bands as a function of the curvature radius. The development of primary and secondary shear bands is related to the inhomogeneous plastic deformation that occurs at the room temperature. The total deformation increases with the decreasing the bending radius. Shear bands in the bent ribbons were observed using scanning electron microscopy.

Abstract: Fe-C-Ta-Cr-Ni alloy powder in diameter of 32-53 μm made by argon atomization was low-pressure plasma sprayed to produce high Cr-Ni cast iron base deposits with finely dispersed tantalum carbide particles. The as-sprayed deposit formed on a water-cooled substrate consisted of γFe, αFe and carbide. The fine precipitates of approximately 0.1 μm in the as-sprayed deposit formed on a water-cooled substrate were carbide. With increasing heat treatment temperature up to 1273 K, the carbide particles coarsened. The hardness of deposit decreases with increasing heat treatment temperature. The wear resistance of as-sprayed deposit formed on a non-cooled substrate was higher than that of the deposit heat-treated at 1273 K. The as-sprayed deposit and deposit heat-treated at 1273 K hade higher wear resistance than a commercial stainless steel.

Abstract: The 8 wt. % yttria stabilized zirconia top coat (TC) and the CoNiCrAlY bond coat (BC) were sprayed onto the surface of newly developed fine-grained cast polycrystalline nickel-based superalloy Inconel 713LC by means of atmospheric plasma spraying (APS). As-prepared samples were isothermally exposed at the temperature of 1050 °C for 200 hours in an ambient atmosphere. Structural changes in the thermal barrier coatings (TBC) system after thermal exposure were studied by means of scanning electron microscope equipped with an energy dispersive microanalyzer. Critical weak points were identified on both the substrate-bond coat and bond coat-top coat interfaces.

Abstract: The contribution deals with an analysis of thick wear-resistant coatings produced on the surface of cast iron friction bearings by means of twin wire arc spraying or by pouring, with the aim of comparing the two manufacturing technologies. In addition to a detailed analysis of the microstructure and phase composition of the two types of coating, their mechanical and adhesion properties were established (using tensile and shear stress testing methods as well as cyclic thermal shocks).

Abstract: The aerospace industry is one of the biggest consumers of advanced materials because of its unique combination of mechanical and physical properties and chemical stability. Highly alloyed stainless steel, titanium alloys and nickel based superalloys are mostly used for aerospace applications. The aim of the work is to evaluate protective Al Si coating applied by diffusion annealing on substrate, Ni base superalloy ZS6K. This superalloy is used for turbine blade production in aero jet engine DV 2. Using of protective alitize coating provides an increasing of heat resistance of superalloy surface and increases working temperature up to 800°C. However, overcrossing of working temperature range (for ZS6K turbine blades it is from 705°C to 750°C) sometimes happen and that is the reason for detailed study of protective coating degradation. The alitize coating were evaluated in starting stage and after various time of regular loading in real aero jet engines DV 2. Coating and its degradation was evaluated with help of quantitative metallography methods (metallography software NIS Elements) and colour contrast as well.