Browsing by Author "Garbe, U"
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- ItemAssessing carbonation in one-part fly ash/slag geopolymer mortar: Change in pore characteristics using the state-of-the-art technique neutron tomography(Elsevier, 2020-11-01) Vu, TH; Gowripalan, N; De Silva, P; Paradowska, AM; Garbe, U; Kidd, P; Sirivivatnanon, VCarbonation has long been recognised as a durability issue attributed to corrosion of steel reinforcement in geopolymer materials. The currently available information, however, is not sufficient to gain a deep understanding of this issue, particularly the facet of the carbonation impact on the pore structure of such materials. This paper, thus, assessed the influence of carbonation on porosity and pore size characteristics of one-part fly ash/slag geopolymer mortar, by using neutron tomography. The cutting-edge thermal neutron tomography used in this study provided the prowess of non-destructive 3D analysis of exploring different regions within geopolymers. The results obtained showed that carbonation in the investigated geopolymer mortars drew their porosity down approximately 30% and shifted pore size regions to smaller pore areas. Other evaluations such as changing pH, carbonation front depth and elemental mapping by scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) were also performed in this study, in order to supplement the findings of neutron tomography. © 2020 Elsevier Ltd.
- ItemA carved ivory cylinder from Akchakhan-kala, Uzbekistan: problems of dating and provenance(Elsevier B.V., 2016-02-01) Betts, AVG; Dodson, JR; Garbe, U; Bertuch, F; Thorogood, GJExcavations at Akchakhan-kala in Uzbekistan, a region known in antiquity as Chorasmia, recovered a large, elaborately carved and heavily burned cylinder of some very solid material. Its poor condition made identification of the raw material difficult. Here we used neutron tomography to examine the internal structure in a non-destructive way, and X-ray Diffraction to determine the main chemical composition of the material which confirmed it as ivory. This was followed by preparation for stable isotope and radiocarbon analysis. The stable isotope analysis suggests a tropical or subtropical grassland source for the ivory, which is unlikely to be from Uzbekistan. The dating shows the ivory to be much earlier than the context in which it was found. Whatever its origin, the ivory travelled far to reach Chorasmia, perhaps in its raw state, and perhaps also for some time in its carved form. © 2015 Elsevier Ltd.
- ItemCuatros Amigos- the four stromatolites in a row. The first 3D image of the oldest evidence of life in the geologic record(Australian Nuclear Science and Technology Organisation, 2021-11-24) Dobson, M; Garbe, U; Campbell, KA; Van Kranendonk, MJ; Rowe, MCThe 3.48 Ga Dresser Formation, Pilbara Craton, Western Australia provides the Earth’s most convincing evidence of early life through a diverse array of biosignatures. However, identifying biosignatures in Archean rocks is difficult due to billions of years of erosion, deformation, and metamorphic alteration. Characterisation of community-accepted biosignatures also remains challenging, particularly the robustness of textural biosignatures as indicators of early life in Archean rocks. The textural biosignatures identified in the Dresser Formation are identified in surface outcrops that are weathered. Therefore, in May 2019, fresh Dresser deposits were drilled to aid in a better understanding of these ancient biosignatures and to provide validity to a biogenic origin. Three well-preserved cores of 5-30 m thickness and 8 cm in diameter were extracted from ~70 m beneath the land surface. The cores provide excellent preservation of biosignatures, including the preservation of fossilized, pyritized, stromatolites. One stromatolite horizon within the core exhibits extraordinary morphological structures. Here we present preliminary results of the 3D geometry of these fossil stromatolites. 3D structures were obtained using the neutron imaging station DINGO at ANSTO. A full tomography of a first sample has been scanned with 1896 projection with an angular step of 0.19° and an exposure time of 60 seconds per projection. The data was reconstructed using filtered backprojection technique with Pydingo (a free in-house developed python toolbox). 3D-rendering was done with VG-Studio. This horizon aids in better defining the biogenicity of these textural biosignatures. © 2021 The Authors
- ItemDirect, time-resolved in-situ observation of dynamic recyrstallization and related phenomena in the bulk of zirconium alloy(Australian Institute of Physics, 2009-02-04) Liss, KD; Garbe, U; Schambron, T; Almer, JD; Li, HJ; Yan, K; Dippenaar, RJNot available
- ItemEffect of texture heterogeneities on the shape memory properties of rolled Fe-Mn-Si SMA(Oldenbourg Verlag, 2009-09) Druker, AV; Sobrero, C; Malarria, J; Garbe, U; Brokmeier, HG; Bolmaro, REWe have investigated an Fe-30Mn-4Si shape memory alloy to clarify the effect, on the bulk texture, of the shear layers resulting from two different thermo-mechanical treatments. XR analysis has shown the existence of texture heterogeneity through the rolled sheet's thickness, due to the effect of friction between sheet and rolls. Neutron diffraction revealed that textured layers on the sheet's surface affect the whole volume. The texture found on the surface of the sheet rolled at 600 degrees C is the most favourable for the γ ->epsilon martensitic transformation which is the origin of the shape memory effect. Comparing these results with those obtained on sheets rolled at room temperature, we found that shear deformation gradients produce changes in the bulk material texture. Tensile tests initially induce the martensitic transformation in those grains favourably oriented. As a result, these favourable orientations disappear in the remnant austenite. © 2009, Oldenbourg Verlag
- ItemForce chains in monodisperse spherical particle assemblies: three-dimensional measurements using neutrons(American Physical Society, 2014-10-03) Wensrich, CM; Kisi, EH; Luzin, V; Garbe, U; Kirstein, O; Smith, AL; Zhang, JFThe full triaxial stress state within individual particles in a monodisperse spherical granular assembly has been measured. This was made possible by neutron imaging and computed tomography combined with neutron diffraction strain measurement techniques and associated stress reconstruction. The assembly in question consists of 549 precision steel ball bearings under an applied axial load of 85 MPa in a cylindrical die. Clear evidence of force chains was observed in terms of both the shape of the probability distribution function for normal stresses and the network formed by highly loaded particles. An extensive analysis of the source and magnitude of uncertainty in these measurements is also presented.©2014 American Physical Society.
- ItemFrom single grains to texture(Wiley-VCH Verlag GmbH & Co. KGaA, 2009-10) Yan, K; Liss, KD; Garbe, U; Daniels, JE; Kirstein, O; Li, HJ; Dippenaar, RJStructural materials, such as metals, ceramics, and their composites are most often polycrystalline. The nature, morphology, and composition of their microstructure determine in large measure the mechanical properties of the final product, and the art to design novel materials is to find particular arrangements which make them harder, more shock absorbing, heat resistant, or self-recovering upon damage and aging. The understanding of the basic processes and their interplay in a polycrystalline structure are most important for improved simulation of plastic deformation and to predict their thermo-mechanical behavior. © 2009, Wiley-VCH Verlag GmbH & Co. KGaA
- ItemHydride precipitation and its influence on mechanical properties of notched and unnotched Zircaloy-4 plates(Elevier Science BV., 2013-05-01) Wang, Z; Garbe, U; Li, HJ; Harrison, RP; Toppler, K; Studer, AJ; Palmer, T; Planchenault, GThe hydride formation and its influence on the mechanical performance of hydrided Zircaloy-4 plates containing different hydrogen contents were studied at room temperature. For the unnotched plate samples with the hydrogen contents ranging from 25 to 850 wt. ppm, the hydrides exerted an insignificant effect on the tensile strength, while the ductility was severely degraded with increasing hydrogen content. The fracture mode and degree of embrittlement were strongly related to the hydrogen content. When the hydrogen content reached a level of 850 wt. ppm, the plate exhibited negligible ductility, resulting in almost completely brittle behavior. For the hydrided notched plate, the tensile stress concentration associated with the notch tip facilitated the hydride accumulation at the region near the notch tip and the premature crack propagation through the hydride fracture during hydriding. The final brittle through-thickness failure for this notched sample was mainly attributed to the formation of a continuous hydride network on the thickness section and the obtained very high hydrogen concentration (estimated to be 1965 wt. ppm). © 2013, Elsevier Ltd.
- ItemHydrogen-induced microstructure, texture and mechanical property evolutions in a high-pressure torsion processed zirconium alloy(Elsevier Ltd., 2012-11-01) Wang, Z; Garbe, U; Li, HJ; Studer, AJ; Harrison, RP; Callaghan, MD; Wang, Y; Liao, XZThe gaseous hydriding-induced evolutions of the microstructure, texture and mechanical properties of Zircaloy-4 processed by high-pressure torsion (HPT) were assessed. Much delta-ZrH(1.66) precipitation at 15 atm (21%) incurred significant hardening of vacuum-annealed HPT samples, and pure epsilon-ZrH(2) obtained at 20 atm showed a superior microhardness of 470 HV(0.3) and a low fracture toughness of 0.63 MPa m(1/2). The delta-hydrides presented strong (1 1 1) texture and followed the (0 0 0 1)(alpha-Zr)//{1 1 1}(delta-ZrH1.66) orientation relationship with the alpha-Zr matrix. During hydriding, alpha-Zr recrystallization texture was developed from the initial deformation texture. Copyright © 2012 Acta Materialia Inc.
- ItemIn situ observation of dynamic recrystallization in the bulk of zirconium alloy(Wiley-VCH Verlag Berlin, 2009-08) Liss, KD; Garbe, U; Li, HJ; Schambron, T; Almer, JD; Yan, KDynamic recrystallization and related effects have been followed in situ and in real time while a metal undergoes rapid thermo-mechanical processing. Statistics and orientation correlations of embedded/bulk material grains were deduced from two-dimensional X-ray diffraction patterns and give deep insight into the formation of the microstructure. Applications are relevant in materials design, simulation, and in geological systems. © 2009, Wiley-VCH Verlag Berlin
- ItemIndustrial application experiments on the neutron imaging instrument DINGO(Elsevier, 2017-01-01) Garbe, U; Ahuja, Y; Ibrahim, R; Li, HJ; Aldridge, LP; Salvemini, F; Paradowska, AMThe new neutron radiography / tomography / imaging instrument DINGO is operational since October 2014 to support the area of neutron imaging research at ANSTO. The instrument is designed for a diverse community in areas like defense, industrial, cultural heritage and archaeology applications. In the field of industrial application it provides a useful tool for studying cracking and defects in concrete or other structural material. Since being operational we gathered experience with industrial applications and commercial customers demanding beam time on DINGO. The instrument is a high flux facility with is 5.3 × 107 [n/(cm2s)] (confirmed by gold foil activation) for an L/D of approximately 500 at HB-2. A special feature of DINGO is the in-pile collimator position in front of the main shutter at HB-2. The collimator offers two pinholes with a possible L/D of 500 and 1000. A secondary collimator separates the two beams by blocking one and positions another aperture for the other beam. The neutron beam size can be adjusted to the sample size from 50 × 50 mm2 to 200 × 200 mm2 with a resulting pixel size from 27 μm to ∼100 μm. The whole instrument operates in two different positions, one for high resolution and one for high speed. We would like to present our first experience with commercial customers, scientific proposals with industrial applications and how to be customer ready. © 2017 The Author(s). Published by Elsevier B.V.
- ItemKowari - OPAL's new stress diffractometer for the engineering community: capabilities and first results(Trans Tech Publications, 2009-11-10) Kirstein, O; Garbe, U; Luzin, VKowari is a neutron diffractometer at ANSTO’s research reactor OPAL. The instrument is dedicated to investigate residual strains and stresses in engineering samples or new materials. Besides its usage in engineering/strain-scanning it is more and more frequently being used for obtaining texture information related to materials science applications. In particular the possibility of using the gauge volume defining slit systems allows extracting local information from the diffraction peak, i.e. position, intensity, and width, without the need to cut the sample specimen. The instrument obtained its operating license in August 2008 to briefly describe the instruments parameters and capabilities, and give examples of two typical applications since it went from commissioning into user mode. © 2020 by Trans Tech Publications Ltd
- ItemMicrostructural evolution during gaseous hydrogen charging of Zircaloy-4 processed by high-pressure torsion: a comparative study(Elsevier B.V., 2012-02-01) Wang, ZY; Li, HJ; Garbe, U; Callaghan, MD; Wang, Y; Liao, XZThe original and high-pressure torsion (HPT) processed Zircaloy-4 materials were hydrided using gaseous hydrogen charging at different hydrogen pressures (10, 15 and 20 atm). The phase and microstructural evolutions of the samples during hydriding were characterized. It showed that when hydriding at the identical conditions, more hydrides tended to form in the HPT samples compared to that of the original ones. At a hydrogen pressure of 20 atm, the HPT sample was completely converted to epsilon-ZrH2 while some delta-ZrH1.66 hydrides (volume fraction similar to 5.73%) were present in the material without HPT preprocessing. The HPT samples exhibited high potential for the hydride precipitation, and the large concentration of lattice defects induced by HPT was considered to be responsible for this enhanced susceptibility. © 2011 Elsevier B.V.
- ItemMicrostructure and texture analysis of δ-hydride precipitation in Zircaloy-4 materials by electron microscopy and neutron diffraction(International Union of Crystallography, 2014-01-01) Wang, ZY; Garbe, U; Li, HJ; Wang, YB; Studer, AJ; Sun, GG; Harrison, RP; Liao, XZ; Vicente Alvarez, MA; Santisteban, JR; Kong, CThis work presents a detailed microstructure and texture study of various hydrided Zircaloy-4 materials by neutron diffraction and microscopy. The results show that the precipitated δ-ZrH1.66 generally follows the δ (111)//α(0001) and δ [110]//α[1120] orientation relationship with the α -Zr matrix. The δ-hydride displays a weak texture that is determined by the texture of the α-Zr matrix, and this dependence essentially originates from the observed orientation correlation between α-Zr and δ-hydride. Neutron diffraction line profile analysis and high-resolution transmission electron microscopy observations reveal a significant number of dislocations present in the δ-hydride, with an estimated average density one order of magnitude higher than that in the α-Zr matrix, which contributes to the accommodation of the substantial misfit strains associated with hydride precipitation in the α -Zr matrix. The present observations provide an insight into the behaviour of δ-hydride precipitation in zirconium alloys and may help with understanding the induced embrittling effect of hydrides.© 2014 International Union of Crystallography.
- ItemA Monte Carlo model of the Dingo thermal neutron imaging beamline(Springer Nature, 2023-12-01) Jakubowski, K; Charcon, A; Tran, LT; Stopic, A; Garbe, U; Bevitt, JJ; Olsen, SR; Franklin, DR; Rosenfeld, AB; Guatelli, S; Safavi-Naeini, MIn this study, we present a validated Geant4 Monte Carlo simulation model of the Dingo thermal neutron imaging beamline at the Australian Centre for Neutron Scattering. The model, constructed using CAD drawings of the entire beam transport path and shielding structures, is designed to precisely predict the in-beam neutron field at the position at the sample irradiation stage. The model’s performance was assessed by comparing simulation results to various experimental measurements, including planar thermal neutron distribution obtained in-beam using gold foil activation and BC-coated microdosimeters and the out-of-beam neutron spectra measured with Bonner spheres. The simulation results demonstrated that the predicted neutron fluence at the field’s centre is within 8.1% and 2.1% of the gold foil and BC-coated microdosimeter measurements, respectively. The logarithms of the ratios of average simulated to experimental fluences in the thermal (E 0.414 eV), epithermal (0.414 eV < E 11.7 keV) and fast (E 11.7 keV) spectral regions were approximately − 0.03 to + 0.1, − 0.2 to + 0.15, and − 0.4 to + 0.2, respectively. Furthermore, the predicted thermal, epithermal and fast neutron components in-beam at the sample stage position constituted approximately 18%, 64% and 18% of the total neutron fluence. © The Authors - Open Access Open Access This article is licensed under a Creative Commons Attribution 4.0 International.
- ItemNeutron imaging applications on DINGO at OPAL(International Conference on Neutron Scattering, 2017-07-07) Garbe, U; Paradowska, AM; Salvemini, FThe new neutron radiography / tomography / imaging instrument DINGO is operational since October 2014 to support research at ANSTO. It is designed for a broad national and international scientific user community and for routine quality control for defence, industrial, cultural heritage and archaeology applications. In the field of industrial application it provides a useful tool for studying cracking and defects in concrete or other structural material. Since being operational we gathered experience in various scientific areas, with industrial applications and commercial customers demanding beam time on DINGO. The measured flux (using gold foil) for an L/D of approximately 500 at HB-2 is 5.3 x 10 [n/cm2s], which is in a similar range to other facilities. A special feature of DINGO is the in-pile collimator position in front of the main shutter at HB-2. The collimator offers two pinholes with a possible L/D of 500 and 1000. A secondary collimator separates the two beams by blocking one and positions another aperture for the other beam. The neutron beam size can be adjusted to the sample size from 50 x 50 mm to 200 x 200 mm2 with a resulting pixel size from 27μm to ~100μm. The whole instrument operates in two different positions, one for high resolution and one for high speed. We would like to present our first experience with scientific proposals and commercial customers with industrial applications.
- ItemA neutron tomographic analysis of plated silver coins from ancient Greece official or illegal?(Materials Research Forum LLC, 2020-05-01) Olsen, SR; Silvemini, F; Luzin, V; Garbe, U; Avdeev, M; Davis, J; Sheedy, KThis study focuses on a neutron tomographic analysis conducted on a set of plated silver coins minted in the city-state of Athens and in the Greek colonies of Kroton and Metapontum (South Italy or Magna Graecia) during the 6th and 5th centuries BC. The investigation aims to define the plating method by characterising the morphological and structural features of the specimens, i.e. the volume fraction of metallic and non-metallic components, and thickness maps of the plating and porosity. The status of these coins is uncertain: were they official issues authorized by state-authorities during periods of trouble (and silver shortages in the public treasury) or the product of ancient or modern counterfeiters? © 2020 by the author(s). Creative Commons 3.0
- ItemNeutron tomographic analysis: Material characterization of silver and electrum coins from the 6th and 5th centuries BCE(Elsevier B.V., 2016-08-01) Salvemini, F; Olsen, SR; Luzin, V; Garbe, U; Davis, J; Knowles, T; Sheedy, KNeutron tomography was applied to study a set of Greek silver coins and a single Lydian electrum coin minted in the 6 and 5th centuries BCE. The investigation was conducted at the new neutron imaging station DINGO at ANSTO in order to demonstrate capabilities and to explore limits of this non-invasive method in characterizing numismatic materials. From the reconstructed volume of each sample, the morphology, porosity, inclusions, and presence of composite structures can be revealed and evaluated. This information can be used to elucidate ancient minting technology and to prove authenticity. Moreover, the state of conservation, corrosion processes and attempts to repair the coins can be determined. © 2016 Elsevier Inc.
- ItemNeutrons for structural integrity applications of engineering components(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Paradowska, AM; Garbe, U; Reid, M; Bendeich, PJ; Law, MThe Australian Nuclear Science and Technology Organisation (ANSTO) at Lucas Heights, have two neutron instruments: KOWARI and DINGO that can be useful tool in modern welding assessment. Both instruments provide non-destructive characterisation techniques for modern materials, engineering and structural integrity investigations. The primary function of the KOWARI instrument is the determination of residual stresses within the interior of bulk engineering components and test samples, in particular for the development of modern engineering welding processes as well as post processing (e.g. post weld heat treatment, peening) and variety of structural integrity investigations. DINGO is a neutron radiography and imaging beamline used to assessing defects and dimensional tolerance of internal features engineering components well suited for thick and complex’s weldments. In this paper an overview of possibilities and recent developments on both instruments are presented.
- ItemNew developments in neutron imaging at DINGO(Australian Nuclear Science and Technology Organisation, 2021-11-25) Garbe, U; Bevitt, JJ; Salvemini, FThe neutron radiography / tomography / imaging instrument DINGO is operational since October 2014 to support research at ANSTO. DINGO provides a useful tool to give a different insight into objects. A major part of applications from research and industrial users was demanding high resolution setup and fast scans on DINGO. The neutron beam size can be adjusted to the sample size from 25 x 25 mm 2 to 200 x 200 mm 2 with a resulting pixel size from 12μm to ~100μm. Depending on the sample composition a full tomography has been taken in 10 minute – 36 hours. During the recent OPAL long shutdown, a new sapphire filter has been installed to reduce the amount of epithermal and fast neutrons at the sample position. These high energy neutrons do not contribute to the image, only as noise, and increasing the radiation levels around the CMOS camera. This update will improve the image quality as well as the reliability of the whole instrument. In addition, we implement a new type of neutron tomography scan to address long samples like in drill cores. These samples can now be scanned horizontal up two 1.2 meter in length. For small core sizes we can run up to three cores in one scan, which makes DINGO a very competitive instrument for fast high throughput imaging. A new software package for 3D reconstruction has been developed as well. It is an open source package based on the python toolbox “tomopy” with a GUI custom made for DINGO to enable users to run the reconstruction on their own computing environment. © 2021 The Authors