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Nejnovější přírůstky:
2023-12-06
00:37
Analýza obsahu prvků v automobilových sklech pomocí neutronové aktivační analýzy a rentgenové fluorescenční analýzy
Kameník, Jan ; Fikrle, Marek ; Kučera, Jan
Mikrofragmenty skel nesou cenné informace o některých druzích zločinů spojených s vozidly. Metodika popisuje využití Rentgenové fluorescenční analýzy (RFA) a neutronové aktivační analýzy (NAA) pro stanovení prvkových přímesí ve střepech automobilových skel. RFA umožňuje rychlé nedestruktivní testování vzorku, které umožní výběr analytických postupů pro další analýzu. Metoda NAA je časově náročnější, má potenciál poskytovat robustní výsledky pro orgány činné v trestním řízení. Metodika zahrnuje popis obou metod a jejich uplatnění při analýze fragmentů skel. Součástí metodiky jsou výsledky analýzy více než 80 vzorků automobilových skel.

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2023-12-06
00:37
Instrumentální neutronová aktivační analýza omamných a psychotropních látek, zejména heroinu, kokainu, metamfetaminu a možných adulterantů
Kameník, Jan ; Kučera, Jan
Instrumentální neutronová aktivační analýza je založena na robustním teoretickém základu a umožňuje analýzu vzorků v pevném stavu bez nutnosti jejich převedení do roztoku. Text metodiky zahrnuje představení základů INAA a příklady postupů používaných pro kontrolu přesnosti výsledků. Uveden je popis postupu analýzy heroinu, kokainu a metamfetaminu. Aplikace pro využití INAA zahrnují odhad čistoty a použitých ředících látek a profilování vzorků drog. Metodika je založena na analýze laboratorních a reálných vzorků.

Úplný záznam
2023-03-12
00:04
Spectrometry of neutron field based on p(20)+Be source reaction
Kozic, Ján ; Štefánik, Milan
The research deals with a spectrometry of neutron field based on the p(20)+Be source reaction. The p(20)+Be interaction stands for a nuclear reaction where protons accelerated to energy of 20 MeV bombard Be target. Produced neutron field has broad energy distribution up to 18 MeV. The research was carried out at the Nuclear Physics Institute of the Czech Academy of Sciences and was motivated by extension of experimental possibilities of the NG-2 target station. To determine the neutron spectrum, the activation foil technique was used. During the experiment, ten activation foils were irradiated. Activated foils were measured using the HPGe detector to determine the reaction rates of observed reactions. The neutron field was simulated in the MCNPX code, and the simulation served as a priori information for the unfolding of the neutron spectrum in the SAND-II code. A determined neutron spectrum is essential for various experiments, e.g., material research, measurements of nuclear data, etc.

Úplný záznam
2023-03-12
00:04
The characterization of the collimated beams of fast neutrons with the CLID detecion system
Ansorge, Martin ; Novák, Jan ; Majerle, Mitja ; Kozic, Ján
A new detection device for the measurements of light ions (p, d, t, α) emitted as the products of the nuclear reactions induced by fast neutrons (5-33 MeV) was recently developed at the Nuclear Physics Institute of the Czech Academy of Sciences. The main objective of the Chamber-for-Light-Ion-Detection (CLID) is to produce new differential nuclear data of high interest for the material applications related to fusion and aerospace technologies and to potentially test and validate models of nuclear reactions. Hereby the experimental set-up for the measurements with the CLID is described in detail. The experimental characterization of the collimated fast neutron beams produced by the cyclotron-driven converter (p(35 MeV)+Be(2.5 mm)) is presented. In particular, the implementation of the Proton-Recoil-Telescope technique used for neutron energy spectra determination with the CLID is described.

Úplný záznam
2022-09-28
00:47
Strain Measurements on Samples of an 3D-printing Maraging Steel by a High-resolution Neutron Diffraction
Mikula, Pavol ; Ryukhtin, Vasil ; Michalcová, A.
In our contribution we present strain measurements on several samples related to the 3D printing material with an unconventional high-resolution neutron diffraction. This method is based on the three-axis diffractometer setting when a conventional two axis neutron diffraction scanner does not provide a relevant resolution.

Úplný záznam
2021-03-28
00:00
Effect of implantation of C, Si and Cu into ZrNb nanometric multilayers
Daghbouj, N. ; Karlík, M. ; Lorinčík, J. ; Polcar, T. ; Callisti, M. ; Havránek, Vladimír
Sputter-deposited Zr/Nb nanometric multilayer films with a periodicity (L) in the range from 6 to 167 nm were subjected to carbon, silicon and copper ion irradiation with low and high fluences at room temperature. The ion profiles, mechanical proprieties, and disordering behavior have been investigated by using a variety of experimental techniques (Secondary Ion Mass Spectrometry - SIMS, nanoindentation, X-ray diffraction - XRD, and scanning transmission electron microscopy - STEM). On the STEM bright field micrographs there is damage clearly visible on the surface side of the multilayer. Deeper, the most damaged and disordered zone, located close to the maximum ion concentration, was observed. The in-depth C and Si concentration profiles obtained from SIMS were not affected by the periodicity of the nanolayers. This is in accordance with SRIM simulations. XRD and electron diffraction analyses suggest a structural evolution in relation to L. After irradiation, Zr (0002) and Nb (110) reflexions overlap for L=6 nm. For the periodicity L > 6 nm the Zr (0002) peak is shifted to higher angles and Nb (110) peak is shifted to lower angles.

Úplný záznam
2021-03-28
00:00
Investigation of deformation mechanisms in textured magnesium alloy
Dittrich, J. ; Čapek, J. ; Knapek, Michal ; Minárik, P.
Advanced in-situ and ex-situ methods were used to reveal active deformation mechanisms during deformation of magnesium alloy with a strong texture. Three sets of samples were prepared from the rolled sheet of commercial AZ31 alloy with respect to its strong basal texture - normal direction (ND), rolling direction (RD) and 45 degrees between RD and ND, and were deformed in both compression and tension. The signal of acoustic emission (AE) was measured concurrently during the deformation. Electron backscattered diffraction (EBSD) was used to study the microstructure after the selected stages of the deformation. It is shown that the extension twinning played an important role during the plastic deformation in the samples having favorably oriented basal texture component, whereas in the unfavorably oriented samples, the role of twinning was marginal. Pronounced activation of twinning only in some samples caused a considerable variation in the deformation behavior and AE response. A consistent link between the energy and amplitudes of the AE signal and the microstructure changes investigated by EBSD was established.

Úplný záznam
2021-03-28
00:00
Mechanical properties of WN43 magnesium alloy prepared by spark plasma sintering
Knapek, Michal ; Minárik, P. ; Greš, A. ; Zemková, M. ; Cinert, Jakub ; Král, R.
The spark plasma sintering (SPS) method was used to prepare bulk materials form WN43 magnesium alloy atomized powder. Compression tests were carried out in order to investigate the effect of different sintering regimes (10 min at 400, 450, or 500 degrees C) on the mechanical properties of the material. Furthermore, complementary in-situ acoustic emission (AE) recording was employed to reveal the dynamics of deformation processes during compression. It was shown that by increasing the sintering temperature, the ultimate compressive strength and ductility were significantly improved. The AE data and microstructure observations suggest that pronounced twin nucleation takes place around the yield point whereas twin growth and dislocation activity are the dominant deformation mechanisms in the later stages of deformation.

Úplný záznam
2021-03-28
00:00
Effect of aluminum content and precipitation on the corrosion behavior and acoustic emission response of AZ31 and AZ80 magnesium alloys
Veverková, E. ; Knapek, Michal ; Minárik, P.
In this study, we investigated the effect of aluminum content and precipitation on the corrosion behavior of the AZ31 and AZ80 magnesium alloys. The investigated alloys were received in the as-extruded condition in order to retain comparable grain size and texture. First, solid solution treatment was performed on the samples of both alloys. Subsequently, the samples were isothermally aged at 200 degrees C for 20 hours. The scanning electron microscopy was used to study the grain size and microstructure. The corrosion properties of samples were studied by potentiodynamic polarization measurements and the AE signal was concurrently recorded. Solution treated AZ80 and AZ31 samples exhibited similar behavior. The aged AZ80 sample showed lower corrosion rate. Also, a strong breakdown appeared in the later (compared to other samples) stage of the potentiodynamic test. The breakdown was found to be easily recognized by AE parameters.

Úplný záznam
2021-02-24
00:43
The effect of the heat treatment at 450°C on distribution of residual stresses of modified Cr-Mo steel welds
Mráz, L. ; Hervoches, Charles ; Mikula, Pavol ; Kotora, J.
The effect of low-temperature long-term heat treatment on distribution of residual stresses on the modified chromium-molybdenum steel of the type 7 CrMoVTiB10-10 and known as the T24 steel which was studied by using neutron diffraction method, is presented.

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