Materials Science Forum Vol. 729

Abstract: The preparation and modelling of single, binary and ternary ion exchanged zeolites that express antimicrobial efficiency is discussed. As experimental material A type zeolite was used and different variations of Ag, Cu and Zn ions were incorporated into the crystal structure. Antimicrobial efficiency is based on the ion concentration and ion release of the zeolite, therefore the maximum cation-exchange capacities (CEC) were determined for each of the single ions. After the determination of CEC the preparation of binary and ternary ion-exchanged zeolite samples were prepared by the mixture of silver, copper and zinc nitrate solutions and the composition of the samples was determined by atomic absorption spectroscopy (AAS). To verify the bioactive effect, the minimum inhibitory concentration (MIC) of single, binary and ternary ion-exchanged zeolite A was determined for bacteria strains.

Abstract: The present study focus on the chemical etching of shape memory nickel-titanium (nitinol) alloy stents made by laser cutting. Application of nitinol stents widely spread in case of atherosclerosis of peripheral vessels. This type of stent has to have appropriate surface quality, flexibility and strength. The aim of chemical etching is removing the burr, which arises during the laser cutting. Etching is one step of the production of stents. The appropriate parameters allow the laser burned surface and most of protruding material removing without significant damage of stent shape. During these experiments etching time was changed. After etching the cross section area was determined by metallographic examinations. The results of the examinations show the relationship between the etching time and the cross-section area. The analysis of measurement data revealed the change of etching velocity. Before and after etching the samples was examined by scanning electron microscopy (SEM). The different surfaces also were compared and the findings were discussed.

Abstract: The geometry and mechanical properties of solid and hollow carbon fibres were investigated by light-and scanning electron microscopy, and by single fibre tensile tests. The hollowness factor of fibres was determined by their external and internal diameter. The tensile strength was determined by single fibre tensile break tests. It was shown that the bigger the diameter of the fibres the lower the mechanical properties is. It was found that the hollow carbon fibres are suitable for preparation of a self-repairing composite with the advantage over other solutions because of their geometrical and mechanical properties.

Abstract: As graphene nanomaterials present exceptional mechanical, thermal and electric properties therefore it can be an excellent reinforcement material for ceramic composites. The research of ceramic composites incorporated with carbon-based fillers has focused on carbon nanotubes until now. In this work silicon nitride-based nanocomposites have been prepared with different ammount (1 and 3 wt%) of multilayer graphene (MLG) made by mechanical milling-based method as well as exfoliated graphite nanoplatelets (xGnP) and nanographene platelets (Angstron) in comparison. The morphology and microstructure of the sintered samples were studied by scanning electron microscope and transmission electron microscope. Phase compositions were determined by X-ray diffractometer. The bending strength and elastic modulus of MLG-silicon nitride composites showed enhanced values compared to the other graphene reinforced silicon nitride ceramic composites.

Abstract: Investigation of conductive polymer composites have been carried out using polypropylene (PP) and polyphenylene sulfonate (PPS) for matrix compound and graphite, carbon black and multi walled carbon nanotubes (MWCNT) for fillers. The comparison of these matrix materials with respect to the resulting electrical conductivity were investigated in depth. The effect of quantity of nanotubes and their dispersion on electrical conductivity and formability was also investigated. It has been found that PPS composites show much higher conductivity, however the high temperature needed for forming, and high viscosity in case of high filler content (50 wt% <) make the processing difficult, therefore the injection molding of the resulting material is currently not possible. Furthermore in contradiction to the literature the addition of MWCNT did not raise the conductivity significantly, therefore the focus have been kept on filler content instead.

Abstract: There are no data about the equilibrium phases in the Cu-Hf-Ti system, in the Cu-rich corner which is a glass former region. Phases and solidifying microstructures were examined in the master alloy (cooling rate: ~150 K/s) and in slowly cooled (5 K/min) samples in case of different compositions. Unknown ternary phases were found by SEM and XRD analysis and one of them with the highest Ti content could be identified by TEM study.

Abstract: This paper reports laser remelting of crystalline Cu based alloys in order to produce amorphous layer on the surface. The as prepared Cu based master alloy ingots were imbedded in a metallic sinking with Wood metal to assure the good thermal conductivity during the laser treatment. The laser remelting of a thin surface layer and a subsequent rapid cooling of it was performed using impulse and continuous mode of Nd:YAG laser. In respectively the impulse mode the laser power and the interaction time were 1.5; 2 kW and 20÷100 ms. In the continuous mode the laser power was 2 kW, and the laser scan speed was 80÷120 mm/s. The characterization of the microstructure of surface layer was performed by XRD, scanning electron microscopy and microhardness measurements.

Abstract: Investigation methods of self-compacting concrete (SCC) in fresh state in virtue of the new Hungarian standard are summarized. The referenced testing methods of former technological guidance were finally replaced by the MSZ EN 12350:2010 standards, part 8, 9, 10, 11 and 12, however momentarily these are only available in English. Besides testing methods, the requirements of MSZ EN 206-9:2010 Additional rules for self-compacting concrete reference titled standard are precedent. Neither of the currently used and standardized testing methods is suitable for collective evaluation of each special feature of SCC, thus these should be used coinstantaneously. Results of recent research work regarding change of SCC features by adding different amount of sand aggregate are presented in this article, too.

Abstract: Mechanical properties, micro structure and crack propagation behaviour of different fabric reinforced mono and hybrid composites for materials of wind turbines have been investigated. Mechanical properties of different fabrics (glass, basalt and carbon) reinforced mono and hybrid composites with epoxy resin matrix have been compared. For characterization of materials tensile, three-point bending and single-edge notched tensile (SEN-T) tests with acoustic emission study were used and scanning electron microscope (SEM) pictures have been taken of the fracture surfaces of composite specimens. Similar behaviour of glass and basalt fibre reinforced composites was revealed by tensile and three-point bending tests. The satisfactory adhesion between fibre and matrix was shown by scanning electron microscope. The fibre-break was proven by the taken pictures to be the main failure mechanism. Results of mechanical tests were also confirmed by acoustic emission study. The crack propagation method of glass and basalt fabric reinforced composites is similar.

Abstract: Two different models have been developed under laboratory conditions based on the experiences of smelting experiments carried out in bloomery furnaces patterned on some excavated 10-12^th century ones. Using Rudabánya iron ore, experiments were conducted in a closed pot and in a small open shaft furnace. During the experiments the air supply, the temperature and the weight of the iron ore and the charcoal were measured. SEM-EDX analyses were performed on bloom pieces obtained from the experiments. The results of the modelling may be correlated with the results of the previous smelting experiments. The model is sufficient for investigating some adequate parameters of the medieval bloomery technology, e.g. the iron yield.