Neutron Diffraction Methods Research Articles

Non-invasive characterization of ancient Indonesian Kris through neutron methods

This study focuses on a non-invasive characterization of a set of ancient kris by means of neutron imaging and diffraction methods. The kris (or keris) is an elongated dagger or short sword distinctive of Malaysia and Indonesia. Its complex structure results from the combination of several layers of iron, steel and sometimes iron–nickel alloy welded together in an intricate pattern that is brought out on the polished surface of the blade through the use of an etchant. Based on the tomographic analysis, four different structural arrangements were identified for the first time. Complementarily, the average quality of the ferrous materials used to produce the four kris was evaluated via time-of-flight neutron diffraction analysis. New details about the manufacturing process of a still little studied class of artefacts were derived from our investigation.

Neutron diffraction study of the crystal and magnetic structures of nanostructured Zn0.34Fe2.53O4 ferrite

The structure and magnetic arrangement of zinc-doped ferrite Zn0.34Fe2.53O4 in the form of spherical nanoparticles with the mean size of 14 nm, synthesized by thermal decomposition method, have been studied by means of the neutron diffraction method in wide temperature range 10–300 K. The investigation provides detailed data on lattice parameters, interatomic bond lengths and angles, and ferrimagnetically ordered moments of iron ions in A and B crystallographic sites of the spinel structure. With a help of supplementary result of Mossbauer spectroscopy, the distribution of Zn and Fe ions between A and B sites is determined to (Fe3+0.82Zn2+0.18)A[Fe3+1.44Fe2+0.27Zn2+0.16☐0.13]BO4, where the B-site vacancy ☐0.13 quantifies the cation non-stoichiometry due to partial oxidation of the ferrite. Within a collinear model of ionic spins, this distribution agrees well with the spontaneous magnetization determined by magnetometry at 5 K of 103.6 A·m2/kg (103.6 emu/g in CGSM), equivalent to 4.22 μB per f.u.

Residual Stress Distribution in Water Jet Peened Type 304 Stainless Steel

In materials with a surface treatment such as shot peening, the residual stress gradient in the surface layer is severe. When measuring the residual stress distribution near the surface with a severe stress gradient by the neutron diffraction method, the gauge volume must be removed from the measurement sample. However, when the gauge volume deviates from the sample, a pseudo peak shift occurs and accurate stress distribution cannot be evaluated. Therefore, it is necessary to evaluate the pseudo peak shift in advance under the same conditions, as in the case of actual residual stress measurement, using a sample in an unstressed state. In this study, the stress distributions in the surface layer of a type 304 stainless steel plate and bar with simulated stress-corrosion cracks which were subjected to water jet peening—giving a surface layer residual stress equivalent better than that of normal shot peening—were evaluated considering the pseudo peak shift. As a result, the residual stress distributions in the surface layer were measured in good agreement with the measurement result obtained by the sequential polishing X-ray diffraction method. It was clarified that the residual stress distribution in the near surface with steep stress gradient can be evaluated by the neutron diffraction method.

Investigation of the residual stress in UO2-Mo composites via a neutron diffraction method

UO2-Mo composites with a core-shell structure have been considered candidates for the thermal conductivity (TC)-enhanced UO2 pellets and have demonstrated commercial potential for use in novel high-level safety reactors. Nevertheless, UO2-Mo composites tend to form micro-cracks that are caused by the presence of residual stress (RS) during manufacturing. In this work, neutron diffraction measurements were employed to analyse the RS in UO2-Mo core-shell structured composites fabricated by spark plasma sintering (SPS) for the first time. It was found that in the UO2-Mo composites, the RS state present in the UO2 matrix was tensile in nature. The RS in the UO2 matrix increased with increaseing Mo content. There was a maximum value of 148 ± 15 MPa in the UO2-10 vol% Mo composite. The micro-cracks produced in the high-Mo content composites were explained by the results of the neutron diffraction measurements. These results could provide significant guidance for the manufacturing and improvement of the operational performance of UO2-Mo composites as next-generation fuels.

Crystal Structure and Cation Distribution of the X-type Hexaferrite Sr2Co2Fe28O46

The crystal structure of an X-type hexaferrite Sr2Co2Fe28O46 was investigated by the x-ray and neutron diffraction methods for a single crystal. Sr2Co2Fe28O46 has the crystal structure described as...

Magnetic and ferroelectric properties, crystal and magnetic structures of SrFe11.9In0.1O19

The structural investigations of SrFe11.9In0.1O19 compound synthesized by solid-state method have been carried by neutron diffraction method in a wide temperature range. The appearace of spontaneous polarization that coexists with ferrimagnetic ordering has been found out at room temperature in strontium hexaferrite partially substituted with In ions. In order to explaine the presence of ferroelectric properties in SrFe11.9In0.1O19 compound, its crystal structure has been refined within the framework of both centrosymmetric P63/mmc (No. 194) and non-centrosymmetric P63mc (No. 186) space groups. The analysis of refinement results allows to understand microscopic mechanism of appearance ferroelectric properties in strontium hexaferrites.

Specific Features of the Atomic Structure of Ti50Ni25Cu25 Alloy Rapidly Quenched from Melt

A complex study of the structure of Ti50Ni25Cu25 alloy obtained in the initial amorphous state by rapid quenching (melt spinning) have been performed for the first time. The investigations are carried out by methods of neutron diffraction, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and electron microdiffraction. It is found that the topological and composition short-range atomic order, corresponding to three superstructure types (B2, L21, and L12), is formed within localized nanodomains (up to 1 nm) in amorphous Ti50Ni25Cu25 alloy upon solidification. It is also demonstrated for the first time that the alloy has an amorphous–crystal structure, which contains (along with individual microspherulites that underwent thermoelastic martensitic transformation B2 ↔ B19) nanocrystalline ensembles with the B2, L21, or L12 structure up to 10 nm in size, which are localized in the amorphous matrix.

Texture Analysis on the AZ31 Magnesium Alloy Using Neutron Diffraction Method

The nature of crystalline materials depends on the individual crystal properties and the features of the polycrystalline state. The direction of crystallite orientation (texture) can undergo evolution during casting, processing, deformation, welding, and also heat treatment. Because texture plays an important role in mechanical characteristics and physical behavior, initial characterization before mechanical treatment needs to be analyzed first. The neutron diffraction method for texture analysis has advantages compared to the x-ray diffraction method, because neutrons can penetrate the material up in the order of centimeters (bulk, texture) compared to x-rays which are only on the surface of the material (surface texture). This research uses magnesium alloy, because this alloy is very light, and is widely used in industries, such as the automotive, computers, communication systems and electronics. The magnesium alloy used is AZ31 type. The AZ31 magnesium alloy is selected due to the most ductile and the most popular amongst AZ wrought alloys (Mg-Al-Zn group). Initial characterization using the neutron diffraction method was held away before the welding procedure was taken out. In this study, a texture neutron diffractometer (DN2), BATAN, set at a wavelength of 1.2799 Angstrom was used to characterize AZ31 material. The neutron source is produced by the GA Siwabessy reactor, which operates at a power of 15 MW. From the characterization of the neutron diffraction pattern, four pole figures {100}, (002}, {101} and {102} were taken. From the pole figure analysis, the crystallite orientation (texture) was obtained in the direction of {001} <110>. The highest intensity lies in the basal center (0002), also seen basal fiber {0001} and prismatic fiber {10-10}

TO THE QUESTION OF THE STANDARD OF MECHANICAL STRESSES

The results of a study of a biaxial stress-strain state using neutron diffraction, standardized in the field of stress measurement, and the Barkhausen effect method are presented. The possibility of using a device with a biaxial load as a standard of stress is evaluated. The article gives an assessment of an error in measuring voltage using strain gauges in relation to measurements made by the neutron diffraction method. The Barkhausen effect method is used as one of the non-destructive testing methods that are sensitive to the stress-strain state. The studies describe the possibility of adapting this method to the proposed stress standard.

Neutron diffraction structural study of CO2 binding in mixed-metal CPM-200 metal-organic frameworks.

Metal-organic frameworks featuring open metal coordination sites have been widely studied for the separation of gas mixtures. For CO2/N2 separations, these materials have shown considerable promise. Herein, we report the characterization of a subset of the well-known PCN-250 class of frameworks upon CO2 adsorption via powder neutron diffraction methods. Noteably, in contrast to previously reported data, they display only moderate CO2 adsorption enthalpies, based on metal cation-CO2 interactions. Further, we show charge balance in these materials is likely achieved via ligand vacancies rather than the presence of μ3-OH groups in the trimetallic cluster that comprises them.

Residual stresses of box and I-shaped columns fabricated from S960 ultra-high-strength steel

Ultra-high-strength steel (UHSS) with a nominal yield stress of 960 MPa is of significant interest for the design of heavily loaded compressive members, such as high-rise buildings, long-span bridges and large-scale infrastructure. However, the residual stresses induced by the fabrication process can be detrimental to the structural members. In particular, compressive residual stresses can result in premature buckling and the ultimate strength of fabricated columns will be reduced. To date, research pertaining to the distribution of the residual stresses for UHSS column is limited. An experimental program about the measurements of residual stress distributions for UHSS box and I-shaped columns is therefore presented herein. Measurements of residual stress were undertaken on two box and two I-shaped columns having various width-to-thickness ratios by using the non-destructive neutron diffraction method. The distributions of residual stress in three orthogonal directions for each specimen was measured. The influences of column width-to-thickness ratio on residual stress distributions were investigated and discussed. In addition, simplified analytical models for the box and I-shaped column were established to facilitate the buckling analysis for such UHSS columns. Comparisons of the residual stress distributions between the experimental results and analytical model demonstrated a good agreement and this model can be safely used for the fabricated high-strength-steel (HSS) and UHSS column.

Residual stresses in welded high-strength steel I-Beams

This study investigates a unified residual stress model applicable for welded high-strength steel (HSS) I-beams. In the experimental program, the homogeneous specimens including two prismatic I-beam samples and a web-tapered I-beam fabricated from Australian BISPLATE-80 and BISPLATE-100 steel plates having nominal yield stresses of 690 MPa and 890 MPa respectively were inspected to determine their residual stress distribution using a non-destructive neutron diffraction technique. Details of this neutron diffraction method for measuring residual stresses are presented. It is shown that the technique can achieve high spatial resolution of the residual stresses as well as capturing the high stress gradient in the heat-affected zone, as a consequence of the deep penetration of the neutron particles into the material. The pattern of residual stresses in the specimens reveals that the tensile stresses peak at the flange-web junctions at an average of 70% of the parent material yield stresses, and that the compressive residual stresses have an approximately uniform distribution that dominates large regions of the flange and web. The test results reconfirm the compressive residual stresses being related to the geometry of the cross-section and independent of the steel grade. The interaction of the residual stresses in the flanges and web was found to be negligible for both prismatic and web-tapered beams. A residual stress model applicable for welded thin-walled I-section members for steel grades between 460 MPa and 1000 MPa is proposed by fitting the test results and collective data available in the literature. This representation was incorporated into a detailed finite element (FE) model and it is shown that the FE predictions are in good agreement with the results of experiments conducted on a wide range of HSS I-section beams tested to failure caused by buckling and/or yielding.

Crystal structure of a high-pressure phase of magnesium chloride hexahydrate determined by in-situ X-ray and neutron diffraction methods.

A high-pressure phase of magnesium chloride hexahydrate (MgCl2·6H2O-II) and its deuterated counterpart (MgCl2·6D2O-II) have been identified for the first time by in-situ single-crystal X-ray and powder neutron diffraction. The crystal structure was analyzed by the Rietveld method for the neutron diffraction pattern based on the initial structure determined by single-crystal X-ray diffraction. This high-pressure phase has a similar framework to that in the known ambient-pressure phase, but exhibits some structural changes with symmetry reduction caused by a subtle modification in the hydrogen-bond network around the Mg(H2O)6 octahedra. These structural features reflect the strain in the high-pressure phases of MgCl2 hydrates.

Smart Neutrons for in-Situ and Operando Characterization of Battery Components and Cells

In the last years, a huge demand emerged to follow electrochemical processes in situ or operando to understand in detail the mechanisms of energy storage systems. Neutrons were identified as a highly suitable probe thanks to their special properties, such as large penetration depths in materials, the non-destructive interaction due to meV energy transfer, the high sensitivity for light elements as especially Li and H in the presence of heavy elements and the easy distinction of neighbor elements or various isotopes of a single element. Besides the well-established method of neutron diffraction using the LiCx peaks to study the intercalation or de-intercalation of Li in the graphite anode [1], other techniques became available to study other phenomena in battery research. Using the imaging techniques, the visualization of electrolyte filling [2], gassing [3] or the Na liquid level of a ZEBRA cell in operation [4] could be examined. Small-angle neutron scattering with the method of scattering-contrast variation (protonated and deuterated labelled samples to vary the sensitivity for example of the electrolyte) open another kind of application to receive further information on shell structures of electrode materials [5]. Further techniques as neutron reflectivity [6], grazing incidence small-angle neutron scattering [7], positron annihilation spectroscopy using neutrons converted into positrons [8] or prompt gamma activation analysis [9] have been successful used. This contribution focuses on the new neutron depth profiling facility [10] of Research Neutron Source Heinz Maier-Leibnitz (FRM II) at Technical University of Munich. The method can be applied for surface studies of the upper 50 μm of a sample. The method is suitable e.g. for Li concentration profiles, as the 6Li nucleus and the incoming neutron form an α particle and a triton leaving the reaction location with 180° direction to each other. Both particles are charged and therefore are easily detectable. The precise reaction depth can be determined due to the fact that the α particle and the triton lose energy passing through the sample. A good depth resolution of about ten nanometers is possible with α particles emitted from <15 μm. With a somewhat worse resolution, a depth down to 50 μm (depending on the sample composition) can be reached with triton particles. Examples of first test measurements including reference samples [11] and the distribution of electrolyte decomposition products in silicon-graphite electrodes [12] will be presented. [1] V. Zinth, C. von Lüders, M Hofmann, J. Hattendorff, I. Buchberger, S. Erhard, J. Rebelo-Kornmeier, A. Jossen, R. Gilles, Journal of Power Sources (2014), 271, 152. [2] T. Knoche, V. Zinth, M. Schulz, J. Schnell, R. Gilles, G. Reinhart, Journal of Power Sources (2016), 331, 267. [3] B. Starke, S. Seidlmayer, M. Schulz, A. Dinter, Z. Revay, R. Gilles, K.H. Pettinger, Journal of the Electrochemical Society (2017), 164(14), A3943. [4] V. Zinth, M. Schulz, S. Seidlmayer, N. Zanon, R. Gilles, M. Hofmann, Journal of the Electrochemical Society (2016), 163(6), A838. [5] C.A. Bridges, X.G. Sun, J. Zhao, M.P. Paranthaman, S. Dai, J. Phys. Chem. C (2012), 116, 7701. [6] E. Hueger, J. Stahn, H. Schmidt, Journal of the Electrochemical Society (2015), 162 (13) A7104. [7] N. Paul, J. Brumbarov, A. Paul, Y. Chen, J.-F. Moulin, P. Müller-Buschbaum, J. Kunze-Liebhäuser,, R. Gilles, J. Appl. Cryst. (2015), 48, 444. [8] S. Seidlmayer, I. Buchberger, M. Reiner, T. Gigl, R. Gilles, H.A. Gasteiger, C. Hugenschmidt, Journal of Power Sources (2016), 335, 224. [9] I. Buchberger, S. Seidlmayer, A. Pokharel, M. Piana, J. Hattendorff, P. Kudejova, Gilles, H.A. Gasteiger, Journal of the Electrochemical Society (2015), 162(14), A2737. [10] L. Werner, M. Trunk, R. Gernhäuser, R. Gilles, B. Märkisch, Z. Revay, Nucl. Instruments and Methods in Physics research (2018), A 911, 30. [11] M. Trunk, L. Werner, R. Gernhäuser, B. Märkisch, Z. Revay, H. Gasteiger, M. Wetjen, Gilles, Materials Characterization (2018), 146, 127. [12] M. Wetjen, M. Trunk, L. Werner, R. Gernhäuser, B. Märkisch, Z. Revay, R. Gilles, A. Gasteiger, Journal of the Electrochemical Society (2018), 165 (10) A2340.

Neutron diffraction study of the crystal structure of TlInSe2 at high pressure

We have investigated the crystal structure of strongly anisotropic semiconductor TlInSe2 by neutron diffraction method under high pressure upto P = 3.3 GPa. It was shown that the tetragonal phase of TlInSe2 crystal (the space group I4/mcm) is stable in the whole investigated range of pressure. The lattice parameters dependence of the pressure and the unit cell volume are obtained, the linear coefficients of compressibility and the bulk moduli are calculated. At the low pressure, obtained value of compressibility for the lattice parameter a is k[Formula: see text] = 14.23 × 10[Formula: see text] GPa[Formula: see text] and for c is k[Formula: see text] = 5.93 × 10[Formula: see text] GPa[Formula: see text]. Obtained values for bulk modulus B0 and its pressure derivative B[Formula: see text] in tetragonal phase are 30(7) GPa and 4(1), respectively.

Structure of the Intermediate Phase Glasses GeSe3 and GeSe4: The Deployment of Neutron Diffraction With Isotope Substitution

The method of neutron diffraction with isotope substitution was used to measure the full set of partial pair-correlation functions for each of the network-forming glasses GeSe$_3$ and GeSe$_4$, which lie at the boundaries of the so-called intermediate phase in the Ge-Se system. The results show the formation of chemically ordered networks, where selenium chains are cross-linked by Ge(Se$_4$)$_{1/2}$ tetrahedra, in contrast to glassy GeSe$_2$ where the chemical order is broken. In all of these materials, the Ge-centered structural motifs are distributed unevenly on an intermediate length scale, as indicated by the appearance of a first-sharp diffraction peak in the Bhatia-Thornton concentration-concentration partial structure factor. The new experimental work provides benchmark results for guiding in the development of realistic structural models, which can be used to explore the network rigidity and other structure-related properties of the glass. In this context, there are discrepancies between experiment and the predictions of first-principles molecular dynamics simulations that are particularly marked in respect of the Ge-Ge correlation functions, which are sensitive to the connectivity of the Ge-centered structural motifs.

Evaluation of residual stresses induced by cold spraying of Ti-6Al-4V on Ti-6Al-4V substrates

Cold spray (CS) is a solid-state additive material deposition technique, which has gained attention in the aerospace industry as a potentially viable technology for structural repair of high-value parts made of high-strength alloys such as Ti-6Al-4V (Ti-64). Residual stresses build up in the substrate and deposited materials resulting from the CS process can influence the integrity of a coating or repair. However, the nature, magnitude and distribution of residual stresses in Ti-64/Ti-64 CS repairs are currently unknown. This study aims to evaluate the effects of geometrical variables (i.e. the number of CS layers, CS layer thickness, and substrate thickness) and track pattern on the magnitude and distribution of residual stresses in CS deposit-substrate assemblies. Through-thickness stress distributions were measured experimentally by neutron diffraction and contour method. Furthermore, a comparison among different residual stress build-up mechanisms induced by CS processes has been discussed for different combinations of substrate and deposit assemblies. An analytical model based on the force and moment equilibrium requirements was used to interpret the experimental stress profiles and to predict the residual stress distribution. It was found that residual stresses are highly tensile near the free surface of the Ti-64 deposits as well as towards the bottom of the substrate, and compressive near the interface region. Although all the specimens showed similar stress distribution, the magnitudes were found to be higher in one or more of the following cases: specimens with a higher number of CS layers, lower substrate thickness, higher layer thickness (i.e. at lower scanning speed), and deposited with a horizontal track pattern.

Correlation of localized residual stresses with ductile fracture toughness using in situ neutron diffraction and finite element modelling

Localized residual stresses were correlated to ductile fracture toughness quantitatively in steel and aluminium alloys using in situ neutron diffraction method coupled with elastic-plastic finite element modelling. Local out-of-plane compression (LOPC) method generated compressive and tensile residual stresses in the vicinity of the fatigue pre-crack front in two compact tension (CT) specimens, respectively, and the evolution of the stress fields was simultaneously measured using in situ neutron diffraction technique under mode-I fracture loading. The results clearly showed that the localized tensile residual stress apparently accelerated stress transfer at the mid-thickness of the CT specimen compared to the specimen having compressive residual stress. The coupled quasi-static ductile fracture simulations and neutron diffraction results revealed a clear correspondence of fracture initiation toughness with localized residual stresses in both steel and aluminium alloys. In the aluminium case, tensile residual stress of 208 MPa was obviously detrimental to the fracture toughness resulting in a 43% reduction while compression of −220 MPa increases by up to 14%. On the other hand, localized residual stress in steel hardly affected fracture initiation toughness due to high plastic dissipation energy. This experiment-simulation coupled study quantitatively elucidates the distinctive role of plastic deformation and stress triaxiality in ductile fracture initiation between steel and aluminium alloy.

Structure of ice confined in carbon and silica nanopores

In this work, water confined in silica and carbon nanopores has been examined. The purpose of this study is to describe the melting behaviour and structure of ice confined in silica nanopores, KIT-6 and ordered carbon nanopores, CMK-3, having pore diameters of 5.9 and 5.2 nm, respectively. To determine the melting temperature of ice inside the nanopores, we performed differential scanning calorimetry measurements of the systems studied. We found that the melting temperature of confined ice is reduced relative to the bulk melting point and this shift is 16 K for water confined in KIT-6 and 21 K for water confined in CMK-3. The structural properties of water at the interfaces were analysed by using the neutron diffraction method (ND). The ND measurements for all the systems studied, showed the features of both hexagonal ice, $$I_\mathrm{h}$$, and cubic ice, $$I_\mathrm{c}$$. However, we show that the ice confined in nanopores does not have a structure corresponding to the typical hexagonal form or the metastable cubic form. The ice confined in nanopores has a structure made up of cubic sequences interlaced with hexagonal sequences, which produce the stacking disordered ice (ice $$I_\mathrm{sd})$$.

Nanocrystalline Features of Structure and Luminescent Properties of (Y1−xLax)3(Al1−yGay)5O12:Ce3+ Garnets

The compounds of (Y[Formula: see text]Lax)3(Al[Formula: see text]Gay)5O[Formula: see text]:Ce[Formula: see text] compositions with partial substitution of Y[Formula: see text] and Al[Formula: see text] by La[Formula: see text] and Ga[Formula: see text], respectively, were fabricated by the co-precipitation method using different precipitants. Detailed investigations of the crystalline structure were made using the neutron diffraction method. The influence of the precipitant, quantity and type of the substituted ions on the structural and luminescent properties of the compounds was established. Distortion of the oxygen dodecahedron in the crystals has the strongest impact on their luminescent properties.