Materials Science, Testing and Informatics III

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Authors: Zoltán Mezey, Tibor Czigány
Abstract: Mechanical properties of hemp fiber reinforced polypropylene were investigated. Hemp fibers were carded together with polypropylene fibers, and needle punched. Composites were prepared by hot pressing of the PP/hemp mats. Hemp content was varied between 0 and 50 % by weight, in 10% steps. A treatment with two different maleic anhydride grafted polypropylenes was applied in order to increase the fiber/matrix surface adhesion. Tensile, three-point bending and Charpy tests were carried out on the treated and untreated composites.
Authors: Annamaria Mikó, Márton Takács, M. Lakatos-Varsányi, L.K. Varga
Abstract: Amorphous and partly nanocrystalline amorphous iron-phosphorus (Fe-P) layers have been deposited by pulse electrochemical technique. X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) have been used to characterize the structure in the layers. Depending on the pulse parameters, the structure of Fe-P layers changed from mostly amorphous to partly nanocrystalline amorphous. The magnetic coercivity and the frequency limit of the samples are discussed in terms of the structure of the Fe-P layers. The frequency limit as determined from the permeability spectra is above 10 MHz, which makes these layers suitable for high frequency inductive element applications.
Authors: A. Paszternák, Ilona Felhősi, Z. Keresztes, Erika Kálmán
Abstract: Phosphonate layer formation on passive iron surface has been investigated by electrochemical and atomic force microscopy techniques. It was found that phosphonate groups bond more strongly to oxide surface, while metallic iron surface is disadvantageous for phosphonate layer formation in aqueous solutions. The rate of anodic dissolution is continually decreasing due to the time-dependent formation of protective phosphonate layer. The kinetics of phosphonate layer formation on passive iron is determined by the potential applied for preceding passive film formation. The size and shape of iron oxide grains depends slightly on the potential of passivation. Changes in morphology due to the phosphonate layer formation have been recorded by AFM.
Authors: Ioana Rotariu, Graziella L. Turdean, Fiammetta Kormos, Dan Macarovici, Gyula Tolnai, Ilona Felhősi, Péter M. Nagy, László Trif, Erika Kálmán
Abstract: The ZrO2 coatings were deposited by sol-gel techniques on copper and steel. The film morphology has been investigated by AFM technique. The performance of ZrO2 films as protective layers was investigated by electrochemical techniques and optical microscopy. Firstly, the electrochemical behaviour of the uncoated copper and steel substrates was investigated by cyclic voltammetry in HCl (1 M) and NaOH (0.4 M) solutions having various pH values. Secondly, the anticorrosion protective effect of sol-gel ZrO2 coatings was evaluated by potentiodynamic measurements in degrading media in which substrates were immersed for 1-90 days. The comparisons of electrochemical parameters allow an explanation of the role of the ZrO2 coatings in the increased resistance of steel and copper against corrosion in moderately aggressive environments..
Authors: A. Tóth, I. Bertóti, M. Mohai, T. Ujvári
Abstract: Ultra-high molecular weight polyethylene (UHMWPE) was surface treated by nitrogen plasma immersion ion implantation (PIII), with the main aim of improving its wear resistance. Accelerating voltages (U) between 15 and 30 kV, fluences (F) between 1×1017 and 3×1017 cm-2 and fluence rates (FR) between 3×1013 and 7×1013 cm-2 s-1 have been applied. XPS was used to characterise the surface chemical composition and structure. Changes induced in the surface mechanical properties like hardness (H), reduced modulus (E) and in the tribological property of volume loss upon uniform wear test (V) were studied by nanoindentation and multipass wear measurements. The evolution of surface topography was followed by measuring the mean roughness (Ra). The macroscopic temperature (T) developed during the PIII-treatment was also studied. Incorporation of N and O took place into the surface layer. With the increase of U the surface N-content tended to decrease. The bulk plasmon loss energy of the C 1s peak increased from 20 eV up to about 25 eV, suggesting densification and the formation of amorphous hydrogenated carbon nitride-like layer. H, T and Ra increased, and V decreased upon PIII treatment, while E either decreased or increased depending on the actual process parameter set applied. In the parameter range studied Hmax, Emax and Ra,max values have been observed at Umax, Fmax and FRmin. Vmin and Tmax have been observed at Umax, Fmin and FRmax, suggesting that the thermal effect is a dominant factor in determining the extent of reduction in the wear rate.
Authors: Sara Tóth, M. Füle, M. Veres, I. Pócsik, Margit Koós
Abstract: Electrodes for electric double layer supercapacitors (EDLS) usually made of a mixture of carbon black and binder material. However the binding mixture causes loss in the capacitance because after the polymerization it obstructs the pores of the carbon black, thus decreasing the active surface of the capacitor. The capacitance of the electrode can be increased by use of additive materials, which improve the electrochemical performance of the active material. The effect of amorphous carbon nano-particles, added to the carbon black on the performance of the supercapacitor electrodes was studied earlier. It was found that maximal value was obtained for the composition of 30 wt.% of amorphous carbon nano-particles and 70 wt.% of carbon black [1]. In this work test-piece supercapacitors (TPS) fabricated with non-aqueous Li-based electrolyte were studied to analyze the influence of the size of the TPS to the specific capacitance. These systems were examined by impedance, charge-discharge measurements and cyclic voltammetry. The working potential window of the capacitor was found to be the 0-1 V region. Increasing the area of the electrode by using Al foils of larger size resulted in proportional increase of the capacitance.
Authors: János Vad, Bálint Morlin
Abstract: A fluid mechanical model was elaborated for the formation of mineral wool in the Junkers production technology. The model is based on an analytical approach. The future aim of the model is to establish guidelines for the following improvement in mineral wool quality: reduction of the diameter of mineral wool fibers, improvement of the homogeneity of fiber diameter distribution, and reduction of gravel size. The mineral wool is considered herein as reinforcing material for polymer composites, and such modifications result in the quality improvement of the composites. The quality improvement can be carried out by modifications of the technological settings. The parameters of the model were approximated on the basis of electron-microscopic measurements on a mineral wool reference specimen.
Authors: M. Veres, Sara Tóth, M. Füle, János Dobránszky, László Major, Margit Koós
Abstract: The structure of diamond-like carbon thin films prepared by radio frequency chemical vapor deposition onto the surface of different corrosion resistant alloys (304, 316L and Iconel 617) used for coronary stent fabrication was investigated by Raman spectroscopy excited by visible (488 nm) and near-infrared (785 nm) light. The effect of electrochemical polishing of the alloy surface and that of Ar+ ion pre-treatment on the structure of the forming film was also studied in case of substrate made of 316L material. It was found that in spite of simultaneous preparation the character of the formed amorphous carbon films depends on the type of the alloy. The layer developed on the surface of Fe-rich stainless steels (316L and 304) showed the most diamond-like character, while the Ni-rich Inconel alloy promoted the formation of layer with high graphitic sp2 cluster content. The Ar+ pre-treatment enhanced the adhesion and the diamond-like properties of the film while the electrochemical polishing was found to be unfavorable concerning the diamond-like character of the layer.
Authors: D. Aranyi, Péter M. Nagy, Zs. Oláh, Erika Kálmán
Abstract: Radical reduction of sulphur content in diesel fuel from the mid 90’s had disastrous impact on diesel fuel’s lubricity. Due to the desulphurization process the lubricity of diesel fuel dropped significantly and got crucial nowadays. The lubricity performance of the diesel fuel is evaluated by the HFRR test in Europe. The HFRR value is determined by measuring the equivalent wear scar diameter occurred on the steel ball specimen during the test. The topographies of these wear scars were investigated by AFM and correlation between the morphology of the worn surfaces and the different HFRR values has been found.
Authors: Z. Balogh, Lajos Daróczi, Z. Erdélyi, S. Szabó, R. Juhász, Dezső L. Beke
Abstract: Barkhausen noise properties of amorphous and nanocrystallized FINEMET type soft magnetic materials are investigated. It is obtained that the amorphous-nanocrystalline tranformation has a well observable effect on both the root main square, RMS, values and the critical exponents of the probability distributions of peak heights and durations.

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