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Tomas I.,ASCR Institute of Physics Prague | Vertesy G.,Institute of Technical Physics and Materials Science | Gillemot F.,KFKI Research Institute | Szekely R.,KFKI Research Institute
Journal of Nuclear Materials | Year: 2013

Inspection of neutron-irradiation-generated degradation of nuclear reactor pressure vessel steel (RPVS) is a very important task. In ferromagnetic materials, such as RPVS, the structural degradation is connected with a change of their magnetic properties. In this work, applicability of a novel magnetic nondestructive method (Magnetic Adaptive Testing, MAT), based on systematic measurement and evaluation of minor magnetic hysteresis loops, is shown for inspection of neutron irradiation embrittlement in RPVS. Three series of samples, made of JRQ, 15CH2MFA and 10ChMFT type steels were measured by MAT. The samples were irradiated by E > 1 MeV energy neutrons with total neutron fluence of 1.58 × 1019-11.9 × 1019 n/cm 2. Regular correlation was found between the optimally chosen MAT degradation functions and the neutron fluence in all three types of the materials. Shift of the ductile-brittle transition temperature, ΔDBTT, independently determined as a function of the neutron fluence for the 15CH2MFA material, was also evaluated. A sensitive, linear correlation was found between the ΔDBTT and values of the relevant MAT degradation function. Based on these results, MAT is shown to be a promising (at least) complimentary tool of the destructive tests within the surveillance programs, which are presently used for inspection of neutron-irradiation-generated embrittlement of RPVS. © 2012 Elsevier B.V. All rights reserved.

Tomas I.,ASCR Institute of Physics Prague | Kovarik O.,Czech Technical University | Vertesy G.,Institute of Technical Physics and Materials Science | Kadlecova J.,ASCR Institute of Physics Prague
Measurement Science and Technology | Year: 2014

A new revolutionary attitude toward investigation of fatigue damage in cyclically loaded steel samples is reported. The measurement is based on the method of magnetic adaptive testing, which - in contrast to traditional magnetic hysteresis investigations - picks up the relevant information from systematic measurement and evaluation of whole minor magnetic hysteresis loops and their derivatives. Satisfactory correlations between nondestructively measured magnetic descriptors and actual lifetime of the fatigued material were found. The presented method is able to serve as a powerful tool for indication of changes, which occur in the structure of the inspected objects during their industrial service lifetime, as long as they are manufactured from ferromagnetic materials. © 2014 IOP Publishing Ltd.

Vertesy G.,Institute of Technical Physics and Materials Science | Meszaros I.,Budapest University of Technology and Economics | Tomas I.,ASCR Institute of Physics Prague
NDT and E International | Year: 2013

Different nondestructive magnetic methods - major hysteresis loop measurement, Barkhausen noise measurement and minor hysteresis loop analysis (Magnetic Adaptive Testing) - were applied on a plastically deformed series of transformation induced plasticity (TRIP) steel samples. The results of the different methods were compared with each other. Good correlation was found between magnetic characteristics, measured in different ways. Magnetic Adaptive Testing (MAT) seems to be the most sensitive method. Good correlation was also found between magnetic parameters and with the destructively measured Vickers hardness values. MAT yields a linear correlation between Vickers hardness and magnetic descriptors, without magnetic saturation of the specimen. © 2012 Elsevier Ltd.

Vertesy G.,Institute of Technical Physics and Materials Science | Tomas I.,ASCR Institute of Physics Prague
IEEE Transactions on Magnetics | Year: 2013

Tensile tests of plastically deformed specimens were performed in order to investigate the relation between variation of magnetic characteristics and residual plastic strain. Deformed steel (CSN 12050) specimens were investigated by the method of magnetic adaptive testing (MAT), measuring and evaluating series of minor magnetic hysteresis loops. It was shown that an efficient combination of the MAT parameters yields a reliable and unambiguous correlation with residual strain of the specimens even though all relations between the strain and each of the individual MAT-parameters were nonmonotonous. © 1965-2012 IEEE.

Dobrik G.,Institute of Technical Physics and Materials Science | Tapaszto L.,Institute of Technical Physics and Materials Science | Biro L.P.,Institute of Technical Physics and Materials Science
Carbon | Year: 2013

We present an easy and fast procedure for producing graphene and few layer graphite nanostructures with edges of predefined crystallographic orientation. By annealing graphite in an oxygen containing atmosphere, of controlled composition hexagonal surface structures can be etched in a controlled way. We show that the process can be made crystallographically selective and the resulting edges are of armchair type. The dimensions of the resulting nanostructures can be well controlled by the oxidation rate, through accurately adjusting the etching parameters, such as oxygen concentration, annealing temperature and duration. The oxidation preferentially starts at defect sites either naturally present in the sample or produced on purpose, the latter holding the promise of a more accurate control over the resulting structures. © 2013 Elsevier Ltd. All rights reserved.

Molnar G.,Institute of Technical Physics and Materials Science
Journal of Materials Research | Year: 2013

A special type of epitaxial growth appears during solid-phase thin film reactions, wher. The reaction product grows epitaxially o. The substrate. Some metal silicide layers and nanostructures are known to develop such epitaxial structures. In this study, iron silicide was used to stud. The effect o. The growth mode o. The epitaxial growth. Strain-induced, self-assembled iron silicide nanostructures were grown on Si(001) substrates by electron gun evaporation of 1.0 nm iron and subsequent annealing at 500-850 °C for 60 min. The growth processes were checked by reflection high-energy electron diffraction, an. The formed structures were characterized by scanning electron microscopy and optical microscopy. The iron silicide nanostructures were oriented in square directions epitaxially fitting t. The surface of Si(001). The shape and size o. The nanostructures depended o. The annealing temperature. In some cases. The nanoparticles were arranged in circles. This might b. The direct consequence of a nucleation-controlled type transition of iron monosilicide to iron disilicide phase at nanoscale. © 2013 Materials Research Society.

Piszter G.,Institute of Technical Physics and Materials Science | Kertesz K.,Institute of Technical Physics and Materials Science | Vertesy Z.,Institute of Technical Physics and Materials Science | Balint Z.,Hungarian Natural History Museum | Biro L.P.,Institute of Technical Physics and Materials Science
Optics Express | Year: 2014

Butterfly wing scales containing photonic nanoarchitectures act as chemically selective sensors due to their color change when mixing vapors in the atmosphere. Based on butterfly vision, we built a model for efficient characterization of the spectral changes in different atmospheres. The spectral shift is vapor specific and proportional with the vapor concentration. Results were compared to standard principal component analysis. The modification of the chemical properties of the scale surface by the deposition of 5 nm of Al2O3significantly alters the character of the optical response. This is proof of the possibility to purposefully tune the selectivity of such sensors. ©2014 Optical Society of America.

Biro L.P.,Institute of Technical Physics and Materials Science | Lambin P.,University of Namur
New Journal of Physics | Year: 2013

The scientific literature on grain boundaries (GBs) in graphene was reviewed. The review focuses mainly on the experimental findings on graphene grown by chemical vapor deposition (CVD) under a very wide range of experimental conditions (temperature, pressure hydrogen/hydrocarbon ratio, gas flow velocity and substrates). Differences were found in the GBs depending on the origin of graphene: in micro-mechanically cleaved graphene (produced using graphite originating from high-temperature, high-pressure synthesis), rows of non-hexagonal rings separating two perfect graphene crystallites are found more frequently, while in graphene produced by CVD - despite the very wide range of growth conditions used in different laboratories - GBs with more pronounced disorder are more frequent. In connection with the observed disorder, the stability of two-dimensional amorphous carbon is discussed and the growth conditions that may impact on the structure of the GBs are reviewed. The most frequently used methods for the atomic scale characterization of the GB structures, their possibilities and limitations and the alterations of the GBs in CVD graphene during the investigation (e.g. under e-beam irradiation) are discussed. The effects of GB disorder on electric and thermal transport are reviewed and the relatively scarce data available on the chemical properties of the GBs are summarized. GBs are complex enough nanoobjects so that it may be unlikely that two experimentally produced GBs of several microns in length could be completely identical in all of their atomic scale details. Despite this, certain generalized conclusions may be formulated, which may be helpful for experimentalists in interpreting the results and in planning new experiments, leading to a more systematic picture of GBs in CVD graphene. © IOP Publishing and Deutsche Physikalische Gesellschaft.

Furjes P.,Institute of Technical Physics and Materials Science
Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS, DTIP 2016 | Year: 2016

This work is intended to demonstrate a significant improvement regarding reliability and reproducibility of the Focused Ion Beam (FIB) milling for nanofabrication solid state nanopore arrays to achieve precise and prognosticatable nanopore geometries fitted to the targeted molecule conformation to be recognised. The statistical geometric parameters of the fabricated nanopores were recorded and studied as the function of the fabrication parameters. The resulted geometries of the nanopores were analysed in details by high resolution SEM and TEM imaging also. To improve the reproducibility of the nanopores regarding its geometrical parameters an additional metallization step was applied in the fabrication process to keep the sensor structure neutralised during the Focused Ion Beam milling considering the complex material composition of the sensor structure. The work proved that the conformity of the pore geometry and the reliability of the fabrication process could be significantly improved by the advanced nanofabrication process. © 2016 IEEE.

Kertesz K.,Institute of Technical Physics and Materials Science | Piszter G.,Institute of Technical Physics and Materials Science | Jakab E.,Institute of Materials and Environmental Chemistry | Balint Z.,Hungarian Natural History Museum | And 2 more authors.
Applied Surface Science | Year: 2013

Photonic crystals are periodic dielectric nanocomposites, which have photonic band gaps that forbid the propagation of light within certain frequency ranges. The optical response of such nanoarchitectures on chemical changes in the environment is determined by the spectral change of the reflected light, and depends on the composition of the ambient atmosphere and on the nanostructure characteristics. We carried out reflectance measurements on closely related Blue lycaenid butterfly males possessing so-called "pepper-pot" type photonic nanoarchitecture in their scales covering their dorsal wing surfaces. Experiments were carried out changing the concentration and nature of test vapors while monitoring the spectral variations in time. All the tests were done with the sample temperature set at, and below the room temperature. The spectral changes were found to be linear with the increasing of concentration and the signal amplitude is higher at lower temperatures. The mechanism of reflectance spectra modification is based on capillary condensation of the vapors penetrating in the nanostructure. These structures of natural origin may serve as cheap, environmentally free and biodegradable sensor elements. The study of these nanoarchitectures of biologic origin could be the source of various new bioinspired systems. © 2013 Elsevier B.V.

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