Materials Science Forum Vol. 729

Abstract: Carbon-based nanocomposite thin films have large application potential because they possess unique mechanical properties, especially high hardness, high elasticity, and a low widely adjustable friction coefficient. In this work, relatively easy preparation of the nanocomposite Ti and C system with good mechanical properties and bioactivity was showed. Formation of physical and mechanical processes, relationship between the evolving structure and other properties of TiC films were studied. The films were deposited on oxidized silicon substrates by dc magnetron sputtering of Ti and C targets in argon and nitrogen at different temperatures between 25°C and 800°C. The composite films consisted of metallic nanocrystalls embedded in a carbon matrix. Highest hardness ~ 18 GPa and reduced modulus of elasticity ~ 205 GPa were obtained when the crystalline nanoparticles were separated by 2-3 nm thin carbon matrix consisting of amorphous and graphite-like carbon phases. In these films the H/E ratio in the both cases is ~ 0,1. Bioactivity studies were carried out on human osteoblast-like cell line MG-63. The number of initially adhering cells on day 7 after seeding was significantly higher on the TiC surface than on the control culture dishes. Good biocompatibility and bioadhesion of these surfaces are attained by a favourable combination of surface roughness and chemistry.

Abstract: In this paper tensile and creep tests were performed on polypropylene (PP) and its glass fiber reinforced composites. The tensile tests were carried out on 6 different glass fiber content reinforced PP composites (0, 5, 10, 20, 30 and 40%) while the creep tests were performed on the unreinforced and 30% and 40% fiber reinforced ones of industrial importance. 50 N/s constant force rate was used until the specimen failed (tensile test) or the preset load level was reached (creep test). The applied load levels for the creep experiments were determined as given ratios of the average breaking force. The tensile breaking strain and tensile strength versus fiber content relationship were analyzed and described by empirical formulas based on the correction and averaging procedure developed.

Abstract: Surface rolling is a cold-working technology for hardening the surface of components made from steel or ductile cast iron. This process is able to increase the hardness of surfaces and to improve fatigue properties, so it is usually used on the axles (shafts) of railway-car wheels. In this paper the influence of surface strengthening technology on the microstructure of the material of railway car wheel axles is studied by Vickers microindentation hardness test, optical microscopy, scanning electron microscopy (SEM) automated EBSD (Electron Backscatter Diffraction) and non-destructive magnetic evaluation.

Abstract: The present paper, as a first step summarizes briefly the master curve construction methods applying the stress relaxation and DMTA based approach. Then, authors make recommendation to increase the covered time (frequency) domain of relaxation modulus master curve coming from standard tensile tests-performed at wide temperature range-by utilizing the time-temperature superposition principle. The proposed approach is used for natural rubber, whose tensile tests, for the sake of simplicity, are replaced by calculated engineering stress-strain curves. All in all, the proposed method gives fast and reliable way for engineers to identify the parameters of spring-dashpot models.

Abstract: Composites of ceramic particle reinforcement (such as alumina) have potential for high temperature structural applications. In contrast to conventional processing methods (e.g. mechanical alloying), in situ processing techniques can be inexpensive and can also lead to unique microstructures, such as very fine dispersions of the reinforcements or interconnecting phases. The feasibility of processing Fe/Al₂O₃ composites layer by an in situ displacement reaction between Fe₂O₃ and Al by using laser beam pre-experiments were carried out and the results are presented in this paper.

Abstract: During the research, scanning electron microscopy, compression, tensile and frequency analysis were performed on silicone rubbers filled with conductive particles , in order to understand the electrical conduction mechanism. The distribution of the conductive nanoparticles and its relationship with the substrate was examined with scanning electron microscopy (SEM). During the SEM studies, the conductive elastomers were investigated in their deformed and original state too. The connection between the deformation and the resistivity was examined with compression and tensile tests. The impedance of the material was examined on a wide range of frequency. The correctness of the lumped parameter model that is mentioned in the literature , was examined and its parameters were determined. The dependence of the resistivity on the aspect ratio of the specimens was also investigated. The aim of this research is to make this construction material intelligent, and to use it to produce hyperelastic mechanical sensors (for strain, force, torque, ect. measuring).

Abstract: Three ultrahigh molecular weight polyethylene (UHMWPE) composites of differing composition, reinforced with multiwalled carbon nanotubes (MWCNT) were prepared. The homogeneous distribution of MWCNT has been attempted by two dry blending methods and one melt-mixing process. The efficiency of the various methods was characterized by their effects on the quasi-static and dynamic physical properties of the composites. In the case of composites manufactured by ball milling the effects of various adhesion promoter additives (compatibilizers) has also been studied by analyzing the tensile, flexural, Charpy impact and wear properties of the composites.

Abstract: The aim of the research work was to analyze the operation of cleaning pigs, in natural gas transportation pipelines from point of view of risk-informed in-service inspection. During the analysis, the main factors considered were the stresses (mechanical, thermal and environmental) and loads, which have effect on cleaning pigs during its operation. The possible damage mechanisms were analyzed which can occur due to their consequences and qualitative probability analysis was performed on the basis of the available information.

Abstract: The aim of the present research work is to examine the influence of mineral composition and grain size distribution on the properties of limestone and dolomite mineral fillers used in Hungarian road construction. Since these properties fundamentally define the features of asphalt pavements, our research goals were assigned accordingly. Different fractions of two mineral fillers (limestone from Alsózsolca and dolomite from Pilisvörösvár) were compared. We have observed deviations in the grain size distribution of some fractions of fillers that were free of contaminations. While limestone consists of a great amount of fines and a relatively small amount of coarse grains, in case of dolomite it is the opposite, that is, small amount of fines and greater amount of coarse grains. The decrease of the grain size of fractions resulted in a slight increase of specific surface area of fillers. We have observed that by the decrease of the grain size of fillers, the hydrophilic coefficient has also decreased. The increasing presence of fines however, resulted in the decrease of the hydrophilic coefficient.

Abstract: On the basis of several years experiments in investigation of hetero-modulus material structures and using natural biomaterials and high purity quartz powders the authors successfully developed new high porosity low density SiC ceramic cellulars and foams. For the development of new silicon-carbide and carbon-silicon-carbide (C/SiC) cellular ceramic composites and foams the author used high purity SiO₂ powders mined in Fehervarcsurgo (Hungary) and a biomaterial reagents made from renewable vegetable under trade-name IG-R1. These low density high porosity silicon-carbides probably can be successfully applied in development of light weight ceramic reinforced metal alloy composites in the future. The structure and X-ray diffraction (XRD) analysis of used raw materials and the achieved by authors new SiC and C/SiC ceramic composites and foams are described and shown in present work.