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EN
The neutron powder diffraction technique has been used for structural studies of Rb2UBr6 solid electrolyte as a function of temperature. The low-, room-, and high-temperature structures have been determined. At the temperature range of 4.2–80 K, the compound crystallizes in a monoclinic unit cell in the P21/c space group. At 80 K and 853 K, the compound crystallizes in a tetragonal unit cell in the P4/mnc space group. At 300 K, the lattice constants are a = b = 7.745(1) and c = 11.064(1) Å. At the temperature range of 853–960 K, a trigonal phase is observed in the P–3ml space group.
EN
The paper presents the results of diffraction stress measurement in Al/SiC composite and in 2124T6 aluminum alloy during the in situ tensile test. The main aim of the work is to observe the stress values for different stages of tensile test for the composite after applying two types of thermal treatment and for the alloy used as a matrix in this composite, to identify the type of hardening process. The experimental results were compared against the calculations results obtained from the self-consistent model developed by Baczmański [1] - [3] to gain the information about the micromechanical properties (critical resolved shear stress τcr and hardening parameter H) of the examined materials. This comparison allowed researchers to determine the role of reinforcement in the composite as well as the impact of the heat treatment on the hardening of the material.
EN
The investigations of iron-containing phases existing in fly ashes were performed using transmission Mössbauer spectrometry. The examined samples of fly ashes were collected from different coal combustion systems, that is, stoker-fired boiler in municipal heating plant and pulverized coal boiler in power plant. Several phases are identifi ed in the samples: iron oxides, paramagnetic aluminosilicate glass with Fe3+ ions and Al2O4- -type spinel with Fe2+ ions. It was pointed out that proportions of contents of phases strongly depend not only on the combustion temperature but also on the way of ash collection.
EN
Magnetic properties of the anion deficient cobaltites La1-xBaxCoO3-δ (x ≥ 0.5) have been studied. Magnetic field induces very large changes in resistivity accompanied by large magnetic hysteresis. It is found that an applied pressure transforms antiferromagnetic state into ferromagnetic one. It is assumed that a ground magnetic state strongly depends on unit cell volume and transition is associated with the cobalt ions spin state crossover. It is suggested that the antiferromagnetic state corresponds to high spin state of cobalt ions whereas ferromagnetic one is due to intermediate spin state of cobalt ions.
PL
Zbadano wpływ naprężenia na podstawowy antyferromagnetyczny stan w anionzubożonym La1-xBaxCoO3-δ Ustalono że tak oddziaływanie ciśnienia jak zewnętrznego pola magnetycznego indukuje przejście ze stanu antyferromagnetycznego w stan ferromagnetyczny. Obserwowana wartość momenty magnetycznego dla La0.5Ba0.5CoO2.8 przy 65 kbar jest równa 1.9μB/Co. Otrzymane wyniki są zgodne z modelem, w którym siła dynamiczna antiferromagnetyczno-ferromagnetycznego przejścia ze stanu HS w stan LS jest spowodowany przez ciśnienie lub pole magnetyczne. Oddziaływanie magnetyczne pomiędzy jonami Co w stanie HS jest ferromagnetyczne, a w stanie IS – antyferromagnetyczne. Oba typy oddziaływań mogą być związane z superoddziaływaniem z atomami tlenu.
EN
The structure and magnetic properties of ternary R-Ge-Sn systems are discussed in this article. Results obtained for these compounds should help to determine the role of p-electron atoms in the magnetic ordering.
PL
W artykule omówiono szczegółowo budowę i właściwości magnetyczne trójskładnikowych układów R-Ge-Sn. Wyniki uzyskane dla tych związków powinny pomóc określić rolę atomów p-elektronowych w oddziaływaniu magnetycznym.
EN
The subject of the investigations were quasibinary Sc(Fe1-xCux)2 Laves phases in which structural and magnetic properties depend on replacement of Fe atoms by Cu atoms. Powder X-ray diffraction and neutron diffraction measurements carried out at room temperature revealed that samples were a mixture of two phases: the quasibinary Sc(Fe1-xCux)2 compounds with cubic C15 structure and ScCu2 with tetragonal structure. 57Fe Mossbauer spectroscopy revealed that the Sc(Fe1-xCux)2 compounds are ferrimagnetic up to an actual concentration xact less than 0.30. A decreasing of mean values of hyperfine magnetic fields was observed. On the basis of analysis of the neutron diffraction spectra the mean values of Fe magnetic moments were determined, considering the component connected with the quasibinary Sc(Fe1-xCux)2 phases. These moments change from 1.45(29) �ĘB in the Sc(Fe0.92Cu0.08)2 to 1.18(32)mi B in Sc(Fe0.72Cu0.28)2 phase at 8 K. From the results of independent hyperfine magnetic field on 57Fe probes and magnetic Fe moments measurements, the hyperfine coupling constant in quasibinary ferrimagnetic Sc(Fe1.xCux)2 phases is estimated as equal to 13 T/mi B at room temperature.
7
Content available remote Neutron diffraction study of porous glasses structure
EN
Microscopic structure of three types of porous glasses with the average pore diameter of 5, 7 and 140 nm obtained by chemical etching was studied by neutron diffraction. The analysis of diffraction patterns has shown that in these glasses, besides an amorphous phase forming a weakly structured background, there are microscopic crystalline inclusions of sassolite with a diffraction size of 26š3 nm and of ?-quartz with a characteristic size of 6š1 nm. Microcrystalline inclusions sizes do not depend on the average pore size diameter. It is shown that in these samples a tridymite phase does not make a significant contribution to observed scattering and a relative sassolite contribution decreases substantially with the average pore size increasing from 5 to 140 nm.
8
Content available remote Diffraction study of thermal dissociation of Ti3AlC2 in vacuum
EN
Titanium aluminum carbide exhibits a unique combination of characteristics of both metals and ceramics coupled with an unusual combination of mechanical, electrical and thermal properties. In this paper, the effect of high-vacuum annealing on the phase stability and phase transition of Ti3AlC2 at up to 1550°C was studied using in-situ neutron diffraction. The decomposition of Ti3AlC2 into TiC was observed from the change of relative phase abundances as a function of temperature. The apparent activation energies of phase decomposition was determined to be -71.9 kJ/mol. Near-surface composition depth profiling using grazing-incidence synchrotron radiation diffraction has revealed a graded phase composition in vacuum-decomposed surfaces.
PL
Węglik tytanowo-glinowy wykazuje unikalną kombinację cech metalicznych i ceramicznych sprzężonych z niezwykłą kombinacją właściwości mechanicznych, elektrycznych i cieplnych. W niniejszym artykule zbadano za pomocą dyfrakcji neutronów, zachodzącej in-situ, wpływ wygrzewania do 1550°C w wysokiej próżni na skład fazowy i przejście fazowe Ti3AlC2. Rozkład Ti3AlC2 do TiC zaobserwowano na podstawie zmiany liczebności faz w funkcji temperatury. Pozorne energie aktywacji procesu rozkładu fazowego określono na -71.9 kJ/mol. Wyznaczenie głębokościowego profilu składu przypowierzchniowego za pomocą dyfrakcji promieniowania synchrotronowego padającego pod małym kątem (GISRD) ujawniło zmieniający się stopniowo skład fazowy w próbkach rozkładanych próżniowo.
EN
Magnetic phase transitions in some rare earth compounds are discussed from the point of view of different experimental methods. The discussion concentrates on the determination of phase transitions in magnetically ordered states. The data presented in this work suggest that the "classical" method, namely the specific heat method, does not yield information on phase transitions between commensurate and incommensurate magnetic structures.
10
Content available remote Magnetic ordering schemes in R3T4X4 compounds
EN
This work is an attempt of a systematization of the magnetic structures of the R3T4X4 (R - a rare earth atom, T - a transition metal, X - a p-electron element) compounds investigated by means of neutron diffraction in the course of a broader research programme . The experiments were performed for twenty samples containing Pr, Nd, Tb, Dy, Ho and Er. Although the determined structures display a huge variety, some regularities were found for them. The authors try to use different approaches in order to elucidate the observed behaviors and come to some conclusions concerning the factors responsible for the found magnetic ordering schemes.
EN
Purpose: of this paper is to investigate the effect of increase in the value of heat input due to change in the welding speed and its influence on residual stress distribution in steel weldments. Design/methodology/approach: The use of the neutron diffraction (ND) technique for residual stress measurements is described. Fully restrained, single-bead-on-plate specimens have been examined. Detailed measurements within a small gauge volume were taken 1.5 mm below the surface, across the sample. In addition, studies of macrostructure and hardness were conducted. Findings: Residual stresses in restrained welds and weld repairs are very complex. The heat input affects the value and distribution of residual stress in the specimen. This peak stress in all three samples occurred not at the toe, but in the middle of the weld bead, where the yield stress is higher. The transverse residual stresses of around half the maximum value of longitudinal stress have been observed. Research limitations/implications: Measurements of residual stress can be very expensive and time consuming. The ND technique is capable of non-destructive investigation in a relatively small gauge volume in depth of the material. However, a number of important issues still remain puzzling, including the uncertainties in the measurement, reliability and interpretation of the results, particularly in regards to the sampling volume and generally in the lack of an engineering standard procedure. The results may be used to calibrate finite element modelling of the welding process. Practical implications: The findings have important consequences with respect to design of welding procedures and fitness-for-purpose assessments. Originality/value: The authors have used ND assessment of residual stresses to follow in detail the changes due to heat input in a small gauge volume. This paper could be an interesting source of information for engineers and researchers who work with welded structures
12
Content available remote Neutron diffraction study of Mn3Fe4V6O24
EN
Mn3Fe4V6O24 compound was prepared using the solid-state reaction method. The magnetic and crystal structural studies were carried out by using neutron diffraction methods at the temperatures of 10 and 290 K. Down to 10 K no long-range magnetic order was observed. Essential differences in the positions of metal ions were observed as compared to similar systems (ß-Cu3Fe4V6O24 and Zn3Fe4V6O24) investigated by X-ray and neutron diffraction methods. In this system, a disordering process involving iron and manganese atoms in M(2), M(3), M(4) cation sites was found, which could be responsible for the significant differences in the physical properties observed for this type of compound.
EN
X-ray and neutron diffraction as well as magnetic measurements have been performed on CeLiGe2 compound. This compound crystallizes in the orthorhombic CaLiSi2 structure type (Pnma space group). Crystal structure parameters have been refined on the basis of the X-ray data at 293 K and neutron diffraction data at 20 and 1.5 K. Below Tc=9.8(2) K Ce-magnetic moment equal 2.32(6) μB and form ferromagnetic structure with the moments parallel to the b-axis.
EN
Neutron diffraction experiments for the evaluation of residual stresses induced by fatigue cycling in metal-matrix composite (MMC) automotive components are presented. The studied components are three brake drums, manufactured by Teksid a/Centro Ricerche FIAT. One of them was used to study the residual stress state in the as-cast condition. The other two brake drums were submitted to fatigue cycling (,,bench tests"), respectively not-leading and leading to failure. The macro- and micro-stress components are evaluated and compared for the three studied components.
PL
Przedstawiono próby wykorzystania dyfrakcji neutronowej do oszacowania naprężeń wewnętrznych wywołanych cyklicznym obciążeniem zmęczeniowym w elementach dla przemysłu motoryzacyjnego wykonanych z kompozytu o osnowie metalowej (MMC). Badanymi elementami są trzy bębny hamulcowe, wyprodukowane przez Teksid/Centro Ricerche FIAT. Jeden z nich był wykorzystany do zbadania stanu naprężeń wewnętrznych w stanie lanym. Pozostałe dwa bębny hamulcowe zostały poddane laboratoryjnej próbie zmęczeniowej pod cyklicznym obciążeniem, w jednym przypadku prowadzącym, a w drugim nieprowadzącym do zniszczenia. Oszacowano i porównano składowe makro- i mikronapreżeń dla tych trzech badanych elementów.
PL
Przedstawiono badania dyfrakcji neutronowej wykonane w celu określenia rozwoju naprężeń residualnych w kompozytach metalowych. Badania przeprowadzono zarówno dla próbek kompozytowych, jak i komponentów, przy uwzględnieniu różnych warunków eksploatacyjnych, jak i zabiegów cieplno-mechanicznych. Podano zwięzły opis fundamentalnej teorii na­prężeń residualnych w kompozytach metalowych oraz skomentowano niektóre techniki eksperymentalne (rys. 1). Badania przeprowadzono dla tarcz hamulcowych wykonanych z kompozytów na osnowie aluminiowej (AA359) umacnianej 20% SiC. Analizowano materiał w stanie pierwotnym oraz naprężenia residualne określone po testach rozciągania i pełzania. Ostatecznie badania na finalnym elemencie w postaci tarczy hamulcowej przeprowadzono zarówno przed, jak i po testach hamowania (rys. rys. 2 i 3). Z danych doświadczalnych oszacowano różne rozkłady obliczonego naprężenia, a mianowicie makronapreżenia oraz sprężyste i niedopasowanie mikronapreżeń cieplnych. Wszystkie wyniki uzyskane z analiz porównano z obliczaniami wykonanymi metodą elementów skończonych. Określono, że po procesie zmęczenia naprężenia cząstkowe w krytycznych punktach bębna hamulcowego dążyły do zaniku. W odlewanych próbkach kompozytowych AA359+20%SiC nie obserwowano żadnych makronapreżeń, natomiast makronapreżenia obecne w bębnie hamulcowym pochodziły prawdopodobnie z samego procesu wytwarzania. W dolnej części bębna makronapreżenia były prawie takie same zarówno przed, jak i po testach, natomiast wzrosły na ściance i zmalały w uszkodzonych częściach po zakończonych testach hamowania. Niedopasowanie mikronapreżeń cieplnych w bębnie hamulcowym było natomiast takie samo jak w materiale w stanie pierwotnym.
EN
Neutron diffraction experiments are presented, for the evaluation of residual stresses in metal matrix composites (MMC) samples and components, induced by different thermo-mechanical treatments and operating conditions. After a brief description of fundamental theory of residual stresses in MMCs, and some remarks on the experimental technique, results are presented concerning experiments on tensile and fatigued specimens as well as on real components. From experimental data, the different contributions to the measured stress, namely macrostresses and elastic and thermal mismatch microstresses, were evaluated. Finally, experimental results are compared to finite element calculations.
EN
The crystal structure of cobalt iodate tetrahydrate Co(IO(3)(2)-4H(2)O (space group P21/c, Z=2, a=836.8(5) pm, b=656.2(3) pm, c=850.2(5) pm, and Beta=100.12°, final Rl = 0.0349 (I>i mniejszości 2 sigma(I) for 1031 unique reflections) was redetermined by single-crystal neutron diffraction studies. The structure is built up by layers parallel (100) connected by interionic O(3)I(-..'OIO(-)(2) bonds. Unequivocal interpretation of the four differently strong OH(...) OIO(-3) hydrogen bonds of the two crystallographic different hydrate H(2)O molecules of the isostructural series M(IO3)(2)-4H(2)O (M = Mg, Co, Ni) on the basis of the observed hydrogen-bond distances and assignment to the uncoupled OD stretching modes of matrix isolated HDO molecules is only possible if weak hydrogen bonds to the iodine lone-pairs of adjacent IO-(3) ions are additionally considered. The potential strength of H(...)I(V)O-(3) hydrogen bonds with respect to H(...) I distances and H(...)IO(-)(3) angles is discussed. A bond-valence concept for estimating the strength of H(...I)I(V)O(-)(3) hydrogen bonds is given.
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