Wyniki wyszukiwania - Biblioteka Nauki

1

Neutron diffraction study of Mn3Fe4V6O24

100%

Bezkrovnyi A. , Guskos N. , Typek J. , Ryabova N. Y. , Bosacka M. , Blonska-Tabero A. , Kurzawa M. , Rychlowska-Himmel I. , Zolnierkiewicz G.

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tom Vol. 23, No. 4

883--890

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.

2

Neutron diffraction study of porous glasses structure

80%

Naberezhnov A. , Antropova T. , Glavatsky I. , Seregin M. , Drozdova I.

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tom Vol. 42, nr 2

271-280

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.

3

Structural and magnetic properties of Sc(Fe1-xCux)2 compounds studied by means of Mössbauer effect and neutron diffraction

80%

Wiertel M. , Surowiec Z. , Budzyński M. , Sarzyński J.

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2013

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tom Vol. 58, No. 1

173-178

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.

4

The Hardening in Alloys and Composites and Its Examination with a Diffraction and Self-Consistent Model

70%

Gadalińska E. , Baczmański A. , Wroński S. , Wróbel M. , Scheffzük C.

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tom Iss. 10

31--46

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.

5

Magnetic ordering schemes in R3T4X4 compounds

60%

Wawrzyńska E. , Szytuła A.

Materials Science Poland

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2006

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tom Vol. 24, No. 3

543--549

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.

6

Magnetic properties and magnetic structure of CeLiGe2 compound

60%

Dmytriv G. S. , Pavlyuk V. V. , Szytuła A. , Penc B. , Stusser M. , Zygmunt A.

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2003

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tom Vol. 8

17--22

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.

7

DFT and neutron diffraction study of 1,6-anhydro-β-D-glucopyranose (levoglucosan)

60%

Sládkovic̆ová M. , Mach P. , Smrc̆ok L. u. , Rundlöf H.

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nr 1

55-70

EN

Geometries of 27 generated conformers of levoglucosan were optimized in vacuo at DFT level of theory combining several functionals with high quality basis sets. For the sake of comparison a reference molecular and crystal geometry obtained from 30 K single crystal neutron diffraction data was used. Analysis of the conformers’ geometries revealed that in all stable conformers intramolecular two-or three centre hydrogen bonds were formed. Relative energy of the conformer, which approximated the molecule in the crystal structure the most, was only ∼3 kcal/mol higher, than the energy of the most stable conformer in vacuo. The largest discrepancies between the geometries calculated in vacuo and experimental geometry concentrated in the vicinity of anomeric C1. These differences were reduced by involving O1 to intermolecular hydrogen bond using a simple model of the respective hydrogen bond in the crystal. [...]

8

Laser Powder Bed Fusion and Selective Laser Melted Components Investigated with Highly Penetrating Radiation

60%

Gadalińska E. , Pawliszak Ł. , Moneta G.

Fatigue of Aircraft Structures

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2021

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tom Iss. 13

81--98

EN

Methods of incremental manufacturing, i.e. 3D printing, have been experiencing significant growth in recent years, both in terms of the development of modern technologies dedicated to various applications, and in terms of optimizing the parameters of the process itself so as to ensure the desired mechanical and strength properties of the parts produced in this way. High hopes are currently being pinned on the use of highly penetrating types of radiation, i.e. synchrotron and/or neutron radiation, for quantitative identification of parameters characterizing objects produced by means of 3D printing. Thanks to diffraction methodologies, it is feasible to obtain input information to optimize 3D printing procedures not only for finished prints but also to monitor in situ printing processes. Thanks to these methodologies, it is possible to obtain information on parameters that are critical from the perspective of application of such obtained elements as stresses generated during the printing procedure itself as well as residual stresses after printing. This parameter, from the point of view of tensile strength, compression strength as well as fatigue strength, is crucial and determines the possibility of introducing elements produced by incremental methods into widespread industrial use.

9

Evaluation of residual stresses induced by fatigue cycling in AA359+20% SiCp brake drums using neutron diffraction

60%

Albertini G. , Fiori F. , Giuliani A. , Rustichelli F.

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tom R. 3, nr 7

260-264

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.

10

The effect of heat input on residual stress distribution of steel welds measured by neutron diffraction

51%

Paradowska A. M. , Price J. W. H. , Ibrahim R. , Finlayson T. R.

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tom Vol. 17, nr 1-2

385--388

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