MTA ME Materials Science Research Group

Miskolc, Hungary

MTA ME Materials Science Research Group

Miskolc, Hungary
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Nagy C.,MTA ME Materials Science Research Group | Fautrelle Y.,SIMAP EPM Laboratory | Budenkova O.,SIMAP EPM Laboratory | Ronafoldi A.,MTA ME Materials Science Research Group | Roosz A.,MTA ME Materials Science Research Group
Materials Science Forum | Year: 2014

A comparison of the results of RANS k-ε and LES turbulence models was done via the simulation of the electromagnetic stirring of liquid 75,5%Ga-24,5%In alloy (in a 10 mm diameter & 30 mm high crucible) using Ansys Fluent. Each velocity component, the distribution of eddies inside the melt and other flow parameters were compared respectively. The accuracy was checked with measured angular velocity data of A. Rónaföldi. The turbulent energy spectra were also produced to see the validity of the LES models. © (2014) Trans Tech Publications, Switzerland.


Vanyorek L.,University of Miskolc | Halasi G.,University of Szeged | Pekker P.,MTA ME Materials Science Research Group | Kristaly F.,University of Miskolc | Konya Z.,University of Szeged
Catalysis Letters | Year: 2016

Abstract: In our experiments, high nitrogen content N-doped multiwall carbon nanotubes (N-CNTs) were synthetized by chemical vapour deposition (CVD) method, after these nanotubes were used as dehydrogenation catalyst support. The chemical nature of the nitrogen atoms in graphitic lattice of N doped CNT was characterized with X-ray photoelectron spectroscopy (XPS) analysis, the pyridinic and graphitic nitrogen atoms were located in nanotube wall. The lattice defects of N-CNT structure were checked with Raman spectroscopy, according to which many defect were present in structure of N-CNTs, owing to the incorporated nitrogen atoms. The formed oxidized N-doped CNT samples were studied by Fourier transform infrared (FT-IR) spectroscopy, according to the test, many oxygen content surface functional groups were identified (COOH, OH and C=O). Palladium nanoparticle morphology and surface on the catalyst substrates were characterized by high resolution transmission electron microscopy (HRTEM) and X-Ray diffraction (XRD) methods. The diameters of palladium particles were slightest in case of carbon nanotube supported catalyst (2 nm), smaller than case of activated carbon, due to absence of microporosity and presence of functional groups on the N-CNT surface. The catalytic activity of the CNT supported catalysts was compared to an active carbon and norit supported samples. The dehydrogenation of C2H6 has been investigated on Pd deposited on various carbon supported catalysts at 573–973 K. On the Pd/CNT catalyst the highest selectivity was reached to ethene (85 %) at 973 K. The most active Pd/Ac achieved 64 % conversion at 973 K. Graphical Abstract: [Figure not available: see fulltext.] © 2016, European Union.


Tomolya K.,MTA ME Materials Science Research Group | Janovszky D.,MTA ME Materials Science Research Group | Sycheva A.,MTA ME Materials Science Research Group | Sveda M.,MTA ME Materials Science Research Group | And 2 more authors.
Intermetallics | Year: 2015

An amorphization process in (Cu49Zr45-xAl6+x)100-y-zNiyTiz (x = 1, y, z = 0; 5; 10) induced by ball-milling is reported in the present work. The aim was investigation of the effect of Ni and Ti addition to Cu49Zr45Al6 and Cu49Zr44Al7 based alloys as well as type of initial phases on the amorphization processes. Also the milling time sufficient for obtaining fully amorphous state was determined. The entire milling process lasted 25 h. Drastic structural changes were observed in each alloy after first 5 h of milling. In most cases, after 15 h of milling the powders had fully amorphous structure according to XRD except for those ones, where TEM revealed a few nanosized crystalline particles in the amorphous matrix. In (Cu49Zr45Al6)80Ni10Ti10 alloy the amorphization process took place after 12 h of milling and the amorphous state was stable up to 25 h of milling. In the case of (Cu49Zr44Al7)80Ni10Ti10 alloy the powders have fully amorphous structure between 12 h and 15 h of milling. © 2015 Elsevier Ltd. All rights reserved.


Benke M.,MTA ME Materials Science Research Group | Mertinger V.,University of Miskolc
Journal of Materials Engineering and Performance | Year: 2014

In situ optical microscope examinations were carried out on the thermally induced thermoelastic martensitic transformation in an untrained CuAlNi alloy and on the bainitic reaction in a CuAlNiMnFe alloy. It was found that a different martensite variant structure formed after every thermal cycle and the transformation was not accompanied with observable plastic deformation in the CuAlNi alloy. Elastic deformations were observed as the martensite plates reached grain boundaries. The growth of new martensite plates was initiated at these locations. The result are discussed and compared to results of other alloys found in the literature. The bainitic reaction was found to occur under isothermal conditions in the CuAlNiMnFe alloys. The reaction was accompanied with a relief formation much finer than that of the thermoelastic martensitic transformation. © 2014 ASM International.


Gyongyosi S.,MTA ME Materials Science Research Group | Barkoczy P.,University of Miskolc
Materials Science Forum | Year: 2013

Numerous simulation methods were developed to simulate the grain growth process in metals and alloys. The basis of these methods is the modeling of the properties and the movement of grain boundaries. From this size level in all solution could be get the microscopic nature of grain growth. One of the simulation methods is the cellular automaton. The simplest cellular automata are the one-dimensional cellular automata. In one-dimension all the properties of the grain boundaries cannot be taken into consideration. This article shows the scale and a method which makes the onedimensional cellular automaton suitable to simulate the grain coarsening process. The average grain size of a Cu18Ni20Zn alloy was measured during an isothermal heat treatment as a function of time and temperature. The results of the simulation are scaled to the measured values, and fit one to another. © (2013) Trans Tech Publications, Switzerland.


Koorosy G.,MTA ME Materials Science Research Group | Tomolya K.,MTA ME Materials Science Research Group | Janovszky D.,MTA ME Materials Science Research Group | Solyom J.,MTA ME Materials Science Research Group
Materials Science Forum | Year: 2013

Amorphous/nanocrystalline alloys were prepared by centrifugal casting and mechanical milling and the amorphous fraction was analysed. Amorphous alloys have a typical X-ray Diffraction (XRD) pattern, because in these systems the degree of regularity of atomic positions is very small. Liquids and glasses generate only one ore more broad diffuse halos. In order to calculate the amorphous fraction value, the difference between the crystalline and the amorphous part of the parts needs to be realized. Furthermore, the measured values need to be smoothed before the determination of the degree of the amorphous fraction. A software developed by us, called GerKiDo can separate and calculate the amorphous fraction from the XRD pattern. These calculated values are compared to the results calculated by the software settled in the X-ray equipment and amorphous fraction measured by Differential Scanning Calorimetry (DSC). The evaluation of X-Ray diffractograms is often time-consuming and difficult. The motivation of this paper was to develop a cost effective, fast and useable method to define the amorphous fraction of samples produced by different technologies. © (2013) Trans Tech Publications, Switzerland.


Tomolya K.,MTA ME Materials Science Research Group | Janovszky D.,MTA ME Materials Science Research Group | Sycheva A.,MTA ME Materials Science Research Group
Materials Science Forum | Year: 2014

The effect of nickel addition was studied in the CuZr system creating alloys with near eutectic composition. Nickel and aluminum have been regarded as useful elements to improve the plasticity, thermal stability of the CuZr-based amorphous alloys. Cu49Zr45Al6 and (Cu49Zr45Al6)95Ni5 were selected because of the good glass-forming ability. After 15 h of milling the structure of the powders was amorphous based on the XRD analysis. By adding nickel, the crystallization temperature (Tx) shifted to higher temperatures compared to CuZrAl alloy. The value of supercooled liquid region was 64 K, which means CuZrAl has a comparatively high glass forming ability. © (2014) Trans Tech Publications, Switzerland.


Nagy C.,MTA ME Materials Science Research Group | Ronafoldi A.,MTA ME Materials Science Research Group | Roosz A.,MTA ME Materials Science Research Group
Materials Science Forum | Year: 2013

A measurement of the angular velocity/revolution number of magnetically stirred liquid gallium-indium alloy was realized with newly developed angular velocity measuring equipment. To get additional information about the flow of the melt, a numerical simulation model was performed with ANSYS FLUENT 13.0 with a single phase 2D k-ε turbulence solver. The aim was to reproduce the flow as accurate as possible, so the measured and computed angular velocity data was compared, to see if the system can be modeled fairly well. © (2013) Trans Tech Publications, Switzerland.


Ronto V.,MTA ME Materials Science Research Group | Sycheva A.,MTA ME Materials Science Research Group | Solyom J.,MTA ME Materials Science Research Group | Pekker P.,MTA ME Materials Science Research Group | And 2 more authors.
Materials Science Forum | Year: 2014

Ti60(NixCu40-x)40 x = 5 - 40 at% ternary alloys were prepared by arc-melting followed by a centrifugal casting into a wedge-shaped copper mould in order to examine glass forming of these compositions. Microstructure of the master alloys and wedge-shaped samples were studied. Among the master alloys, which solidified under non-equilibrium conditions, the sample with 15 at% Ni content displayed clear eutectic structure and its wedge-shaped sample had the finest structure but still crystalline. Microstructure of the other compositions was far from amorphous state. © (2014) Trans Tech Publications, Switzerland.


Kovacs J.,MTA ME Materials Science Research Group | Ronafoldi A.,MTA ME Materials Science Research Group | Roosz A.,MTA ME Materials Science Research Group
Materials Science Forum | Year: 2014

Cylindrical Pb-Sn alloy samples (diameter: 8 mm, length: 120 mm) of different compositions (30, 40 and 50 wt.% of Sn) were prepared from high pure (4N) components. The unidirectional solidification experiments have been performed according to the upward vertical Bridgman-method by using a rotating magnetic field (RMF) with a magnetic induction (B) of 150 mT and with a frequency (f) of 50 Hz. The sample-movement velocity (v) was constant (0.05 mm/s) and the temperature gradient (G) changed from 7 to 3 K/mm during the solidification process. The first half of samples was solidified without using the magnetic field and the second half was solidified by using the magnetic field. Under the influence of this strong flow induced by the magnetic field, the columnar microstructure of the first part decomposed and a characteristic Christmas tree- like macrosegregated structure with equiaxed Pb-dendrites was developed. The secondary dendrite arm spacing (SDAS) and the volume percent of primary Pb-phase (dendrite) were measured by an automatic image analyser on the longitudinal polished sections along the whole length of the samples. The effect of the forced melt flow on the micro- and macrostructure was studied in case of the different sample compositions. © (2014) Trans Tech Publications, Switzerland.

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