Abstract: In the general framework of studies on nanomaterials for micro-sensors, cerium dioxide nanopowders (CeO2-z) and nanocomposites systems of copper doped ceria (CuOx-CeO2-z) were prepared and characterized. The aim of this specific study is to try to connect catalytic activity of such nanopowders with microstructure, additional phases and/or doping effect. The nanopowders of pure and doped cerium oxide were elaborated from various “Sol-Gel” chemical routes. Microstructural analysis was first carried out by X-ray diffraction (XRD). The specific areas were
determined from BET adsorption techniques and the results were correlated to the size determinations obtained from XRD. The catalytic activity of such nanopowders in presence of methane gas CH4 was analyzed making use of FTIR spectrometry and a homemade device. For a better understanding of such catalytic responses, we proposed a modeling approach of solid gas interactions that takes into account a typical temperature dependent Avrami's model.
Abstract: Investigation of the microstructure, properties and biocompatibility of the Ti-6Al-4V
alloy nitrided under glow discharge was performed. The microstructural analyses were carried out using light microscopy, X-ray diffraction, analytical scanning and transmission electron microscopy. Phase identifications and chemical composition of
the layer and bulk material (substrate) were determined by electron diffraction and energy dispersive X-ray spectrometry. Atomic force microscopy was applied for layer surface topography measurements. Microhardness and Young’s modulus measurements as well as frictional wear resistance and corrosion resistance tests were performed. The investigation revealed a clear correlation between the micro/nanostructure and surface topography of the layer with its micromechanical,
tribological and corrosion properties. In-vitro examinations of biofilm and cell
behaviour show that the nitrided Ti-6Al-4V alloy exhibits good biocompatibility.
Abstract: The results obtained in the present study reveal the effect of equal channel angular
extrusion (ECAE) on the grain size and mechanical properties of Al-Li alloys. During 8 passes of ECAE process, coarse grain microstructure in the initial state transforms into ultrafine grained. The
final grain size depends on both total strain applied and Li content in the alloy. Due to the grain refinement the microhardness and yield stress increase by 100%. During compression deformation, the coarse grain alloys exhibit continuous hardening, whereas in the ultrafine-grained alloys, a stagnation of work hardening at the beginning of compression deformation is observed. This behaviour is related to the dynamic recovery of the severely deformed microstructure.
Abstract: The aim of the study was to obtain a ferritic-austenitic stainless steel through sintering of the mixture of austenitic steel AISI 316L powders with silicon in the amount ranging from 1 to 7%. The pressed mixtures were sintered at 1240oC for 60 minutes under hydrogen atmosphere. The results of the silicon admixture on the density, porosity, microstructure and mechanical properties of the sintered specimens are discussed.
Abstract: The paper presents the results of research concerning the influence of hot deformation parameters on the structure and substructure as well as the plastic properties of a Fe–Ni austenitic alloy. The research was performed on a torsion plastometer in the range of temperatures of 900÷1150°C, at a strain rate 0.1 and 1.0 s-1. Plastic flow curves have been drawn up and the interrelations have been determined between the process parameters and the recrystallized grain
size, inhomogeneity and shape. Functional relations between the Zener-Hollomon parameter and the mean grain size after dynamic recrystallization have been developed and the hot deformation activation energy has been estimated. The examination of substructure on TEM allowed the calculation of structural parameters: the average subgrain area and the mean dislocation density. A
detailed investigation has shown that the substructure is inhomogeneous, consists of dense dislocation walls, subgrains and recrystallized regions.
Abstract: The process of induction heating followed by forced cooling of large-scale castings is
considered. The main goal of this study is to develop a reliable design methodology of surface heat treatment process to provide high quality of the treated component. It is assured by determination of the material constants and convection coefficient during heating and cooling experiments carried out on the specimens made of material adequate to the considered large-scale casting. The main part
of the investigations was preceded by wide analyses of the mechanical and chemical properties of the tested specimens. The presented global design methodology of large-scale castings gives a possibility to predict the temperature distribution on the hardened surface during induction heating and forced cooling. This allows to select the most adequate parameters and apply them in a real
specific process. The obtained results have been analyzed and discussed.
Abstract: Selection of proper technological surface layer well resistant to cyclic external loads
superposed onto residual stresses is presented in this paper, with a gear wheel taken as an example. The computer simulations of external loads were carried out by means of the FEM method (Finite Element Method) with the use of the ANSYS package. Residual stresses were measured by means of the Waisman-Philips and modified X-ray sin2Ψ method. The results of the stress superposition were verified experimental by with use of a circulating power stand. The applied low pressure
nitiriding method NITROVAC demonstrated a high ability to increase the durability and reliability of the discussed toothed wheel in comparison with the convencional treatment applied so far.
Abstract: The influence of a tribological process in the polymer/metal system on changes in
microhardness (H) and Young’s modulus (E) of the surface under friction and UHMWPE volume has been studied. Twelve samples of polyethylene characterized by a different degree of initial plastic deformation and different electron irradiation dose were analyzed. For four of the samples a decrease by 5÷10 times in polyethylene degradation has been found. This result is promising in that a prolonged durability can be expected in case of application for endoprostheses
acetabular cups. It has been found also that a polyethylene material irradiated after initial prestraining only once shows enhanced micromechanical properties after friction. It has been found that this result was due to reorientation of lamellas on the friction surface taking place during deformation which accompanies the tribological process. It has been proved that the increase of H and E values in the layers situated at a depth of 1.5 mm÷7.5 mm is due to a decrease of the free
volume centers in the UHMWPE polyethylene and to an increase of the degree of spatial arrangement of the structure (absorption in crystallinity band of FTIR spectrum).
Abstract: The current work focuses on the materials science aspects of the growth phenomena of titanium-based coatings TiN, (Ti,Al)N and (Ti,Al)(C,N) with face-centered cubic lattice structure, deposited by the industrially-styled Pulsed Laser Deposition (PLD) technique at room temperature. hese coating materials are widely spread in mechanical, tribological and decorative applications
due to their exceptional physical and chemical properties. Recently, the trend of using temperaturesensitive materials like polymers and tool steels of the highest hardness demands new lowtemperature coating techniques for protective surface finishing as well as for functionalization of the surfaces. These titanium-based compounds can fulfill a wide range of these demands, but up to now there is a lack of industrially designed vacuum coating techniques operating at temperatures
lower than 50 °C necessary for these materials. The PLD process is known as one of the most promising candidates for such coating demands. But up to now PLD is only a well-established laboratory coating technology and has not become a standard industrial coating technique despite its outstanding process features. The missing of PLD coating systems, which fulfill the requirements for industrial applications like high-rate deposition and adequate sizes of deposition chambers, is
considered as one of the main obstacles for a breakthrough of the PLD technique. To overcome this problem an industrially designed PLD coating system has been developed and built at the Laser Center Leoben of JOANNEUM Research Forschungsgesellschaft mbH.