Browsing by Author "Davis, J"
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- ItemAqueous leachability of geopolymers containing cations Ag, Cd, and Co(The Italian Ceramic Society, 2008-06-29) Perera, DS; Aly, Z; Davis, J; Kurlapski, I; Vance, ER
- ItemAqueous leachability of metakaolin-based geopolymers with molar ratios of Si/Al=1.5-4(Elsevier, 2008-08-31) Aly, Z; Vance, ER; Perera, DS; Hanna, JV; Griffith, CS; Davis, J; Durce, DThe leachability in water of metakaolin based geopolymers with molar ratios of Na/Al = 1 and Si/Al = 1.5-4.0 has been investigated in order to optimise the composition for the immobilisation of nuclear waste. Formulations with Si/Al of around 2 are the most suitable using the ASTM/PCT leach test method. The variability of the leach results is discussed with reference to the microstructure, compressive strength and the degree of polymerisation of the geopolymers as observed here by solid state nuclear magnetic resonance, XRD and infrared measurements. © 2008, Elsevier Ltd.
- ItemAqueous leachability of metakaolin-based geopolymers with molar ratios of Si/Al=1.5-4(Materials Australia, 2007-07-04) Aly, Z; Davis, J; Vance, ER; Perera, DS; Durce, D; Hanna, JV
- ItemBiofilm-enhanced adsorption of strong and weak cations onto different microplastic sample types: use of spectroscopy, microscopy and radiotracer methods(Elsevier, 2019-07-01) Johansen, MP; Cresswell, T; Davis, J; Howard, DL; Howell, NR; Prentice, EThe adsorption of metals and other elements onto environmental plastics has been previously quantified and is known to be enhanced by surface-weathering and development of biofilms. However, further biofilm-adsorption characterisation is needed with respect to the fate of radionuclides. This study uses spectroscopy, microscopy and radiotracer methods to investigate the adsorption capacity of relatively strong and weak cations onto different microplastic sample types that were conditioned in freshwater, estuarine and marine conditions although marine data were limited. Fourier-transform infrared spectroscopy confirmed that surface oxidation chemistry changes induced by gamma irradiation were similar to those resulting from environmental exposures. Microscopy elemental mapping revealed patchy biofilm development, which contained Si, Al, and O, consistent with microbial-facilitated capture of clays. The plastics+biofilm of all sample types had measurable adsorption for Cs and Sr radiotracers, suggesting environmental plastics act broadly as a sink for the key pervasive environmental radionuclides of 137Cs and 90Sr associated with releases from nuclear activities. Adsorption onto high-density polyethylene plastic types was greater than that on polypropylene. However, in most cases, the adsorption rates of all types of plastic+biofilm were much lower than those of reference sediments and roughly consistent with their relative exchangeable surface areas. Crown Copyright © 2019 Published by Elsevier Ltd.
- ItemThe characterisation and formation of novel microstructural features in a Ti−Nb−Zr−Mo−Sn alloy manufactured by Laser Engineered Net Shaping (LENS)(Elsevier, 2021-01) Zhu, HL; Wang, ZY; Muránsky, O; Davis, J; Yu, S; Kent, D; Wang, G; Dargusch, MSNovel microstructural features were found in the Ti−Nb−Zr−Mo−Sn alloy manufactured by Laser Engineered Net Shaping (LENS). Examination of the microstructure showed that the fabricated sample exhibits a layered morphology with arced deposit boundaries. Novel distributions and morphologies of various phases including β, α, α'' and ω were detected in the LENS-manufactured part which substantially differ to conventionally processed alloy counterparts. The β grains and subgrains spread over multiple deposits and layers, aligned to the build direction, forming a complex network microstructure comprising large highly textured columnar grains aligned to β phase <001> orientations. The α precipitates have needle-like shapes and are widely distributed across a majority of the deposited layers, whereas the nanoscale ω particles were present in regions absent of α precipitation. Localised, massively transformed α'' phase with a very long and curved rod-like shape and substantial surface defects was identified. The formation of these novel microstructural features is investigated and discussed in the context of the characteristics of the LENS fabrication process. The microstructures are attributed to the complex thermal history in the unique deposit-by-deposit and layer-by-layer method employed during LENS additive manufacturing in conjunction with the complex precipitation behaviours exhibited by TiNb-based alloys. The characteristics and formation mechanisms of the LENS-manufactured Ti−Nb−Zr−Mo−Sn alloy microstructures revealed here provide a basis to optimize LENS and post-LENS heat treatment processes to optimize microstructures for improved performance. © 2020 Elsevier B.V
- ItemCharacterisation of anthropogenic radioactive particles from former weapon test sites in Australia(South Pacific Environmental Radioactivity Association, 2018-11-06) Young, EL; Johansen, MP; Child, DP; Hotchkis, MAC; Howell, NR; Pastuovic, Z; Howard, DL; Palmer, T; Davis, JFormer nuclear test sites on Australian territories such as those at Maralinga and the Montebello islands have been remediated to varying extents but wide-spread radioactivity still remains. Fission and neutron-activation products at the test sites have been decaying over time but long-lived radioisotopes such as uranium and plutonium persist within the environment, predominantly in the form of discrete particles. These particles vary widely in composition depending upon the detonation characteristics and local geology, and are widely dispersed around each site. Radioactive particles are the dominant form of radionuclides at the former test sites and the future distribution of radioactive contaminants in the environment at these sites is largely dependent upon their fate and behaviour. The weathering of particles in the environment and the potential release of the radioactivity they contain is influenced by a range of factors including particle morphology, elemental composition and chemical form, and the prevailing environmental conditions. Radioactive particles have been isolated from soils and sediments from Australian test sites and characterised using photostimulated luminescence (PSL)-autoradiography, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), Synchrotron X-ray fluorescence microscopy (XFM) and particle-induced X-ray emission (PIXE). The characteristics of the particles and potential implications for their long term fate will be discussed in the context of the techniques applied and the environments in which the particles were found.
- ItemCharacterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding(Materials Australian and The Australian Ceramic Society, 2015-02-09) Bhattacharyya, D; Davis, J; Drew, M; Harrison, RP; Edwards, LNickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiG welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides at some grain boundaries and triple points. The nature of the precipitates in the molten zone varied according to the local chemical composition. - Graphical abstract: Display Omitted - Highlights: • Ni-based alloy with Cr, Mo, Si, Fe and C was welded, examined with SEM, EBSD, and TEM. • Original Ni{sub 2}(Mo,Cr){sub 4}(Si,C) carbides changed from equiaxed to lamellar shape in HAZ. • Composition and crystal structure remained almost unchanged in HAZ. • Original carbides changed to lamellar Ni{sub 3}(Mo,Cr){sub 3}(Si,C) in some cases in weld metal. • Precipitates were mostly incoherent, but semi-coherent in some cases in weld metal.
- ItemCharacterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding(Elsevier B.V., 2015-07-01) Bhattacharyya, D; Davis, J; Drew, M; Harrison, RP; Edwards, LNickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiG welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides at some grain boundaries and triple points. The nature of the precipitates in the molten zone varied according to the local chemical composition. © 2015 Elsevier Inc.
- ItemCharge collection in SOI microdosimeters and their radiation hardness(IEEE, 2023-02-03) Pan, VA; Tran, LT; Pastuovic, Z; Hill, D; Williams, JB; Kok, A; Povoli, M; Pogossov, A; Peracchi, S; Boardman, DA; Davis, J; Guatelli, S; Petasecca, M; Lerch, MLF; Rosenfeld, ABA new batch of microdosimeters has been extensively studied for their charge collection efficiency (CCE) properties, as well as their radiation hardness for medical, space and accident applications. Silicon-on-insulator (SOI) microdosimeters with an active layer thickness of 10, 20 and 50 μm have been investigated and were characterized with a 24 MeV carbon ion beam as well as a Co-60 gamma source. A negative pulse was observed in addition to the positive pulses generated within the sensitive volumes (SVs) by incident ions which led to undesirable low energy events in the SOI microdosimeters response. To study this phenomenon, the microdosimeters were irradiated with gamma radiation from a Co-60 source with a total dose of 3 and 10 Mrad(Si). It was determined that the negative pulse was originating from the support wafer due to the displacement current phenomenon. Irradiation with the Co-60 source led to a disappearing of the negative pulse due to an increase in recombination within the support wafer while almost no changes in CCE were observed. A radiation hardness study was also performed on the 50 μm SOI microdosimeter with 16 SVs being irradiated with a fluence of ~ 10 8 12 C ions/cm 2 . A CCE deficit of approximately 2% was observed at an operation bias of 10V within the SVs. The findings of this work demonstrate that the SOI microdosimeters can be utilized in space and medical applications as they can handle typical levels of dose encountered in these applications. Additionally, evidence for SOI microdosimeter fabrication standards in terms of support wafer resistivity and buried oxide (BOX) thickness is shown. © 2023 IEEE
- ItemCultural heritage project at Australian Nuclear Science and Technology Organisation (ANSTO)(Springer Nature, 2022-01-25) Salvemini, F; White, R; Levchenko, VA; Smith, AM; Pastuovic, Z; Stopic, A; Luzin, V; Tobin, MJ; Puskar, L; Howard, DL; Davis, J; Avdeev, M; Gatenby, S; Kim, MJ; Grazzi, F; Sheedy, K; Olsen, SR; Raymond, CA; Lord, C; Richards, C; Bevitt, JJ; Popelka-Filcoff, RS; Lenehan, CE; Ives, S; Dredge, P; Yip, A; Brookhouse, MT; Austin, AGThe Australian Nuclear Science and Technology Organization (ANSTO) is the home of Australia’s most significant landmark and national infrastructure for research. ANSTO operates one of the world’s most modern nuclear research reactors, OPAL; a comprehensive suite of neutron beam instruments; the Australian Synchrotron; the Electron Microscope Facility; and the Center for Accelerator Science. Over the years, the suite of nuclear methods available across ANSTO’s campuses has been increasingly applied to study a wide range of heritage materials. Since 2015 the strategic research project on cultural heritage was initiated in order to promote access to ANSTO’s capabilities and expertise, unique in the region, by cultural institution and researchers. This chapter offers a compendium of ANSTO nuclear capabilities most frequently applied to cultural heritage research. A series of innovative, interdisciplinary, and multi-technique studies conducted in close collaboration with Australian museums, institutions, and universities is also showcased. It includes research on dating Aboriginal Australian rock art and fingerprinting the sources of ochre pigments; rediscovering the technological knowledge in the making of early coinage and ancient weapons; virtually unwrapping the content of votive mummies from ancient Egypt; and investigating and restoring the original layer of a painting that can be explored by the museum audience in a novel type of exhibition based on an immersive, interactive, and virtual environment. © 2022 Springer Nature Switzerland AG
- ItemThe effect of applied stress on the high-temperature creep behaviour and microstructure of NiMoCr Hastelloy-N® alloy(Elsevier, 2021-05) Zhu, HL; Muránsky, O; Wei, T; Davis, J; Budzakoska-Testone, E; Huang, HF; Drew, MThe high-temperature creep behaviour and microstructural evolution of Hastelloy-N® was investigated using miniaturised creep samples tested under vacuum at 973 K (700 °C) and stresses of 100 MPa and 165 MPa. The higher applied stress reduced the creep life of the alloy sevenfold, and the creep mechanism at 165 MPa was predominately dislocation-creep while the creep mechanism at 100 MPa was a combination of dislocation creep, diffusion creep and grain boundary sliding. The post-creep microstructure examination using Electron Back-Scatter Diffraction (EBSD) technique showed significantly larger number of Low-Angle Grain Boundaries (LAGBs) and Geometrically-Necessary Dislocations (GNDs) formed during creep at 165 MPa than at 100 MPa. On the other hand, the microstructure of the sample tested at 100 MPa revealed more pronounced precipitation of secondary carbides along High-Angle Grain Boundaries (HAGBs) due to the longer exposure to high temperature. The precipitation of secondary carbides along grain boundaries resulted in grain boundary embrittlement and the promotion of intergranular cracking, which then resulted in low strain-to-failure in the low-stress creep test sample. In addition, it is shown that the prolonged exposure to the elevated temperature lead to Cr depletion from the matrix, reducing solid solution strengthening during creep. © 2021 Acta Materialia Inc. Published by Elsevier B.V.
- ItemElectrical conductivity and defect disorder of tantalum‐doped TiO2(John Wiley & Sons, 2017-05-02) Alim, MA; Bak, T; Atanacio, AJ; Du Plessis, J; Zhou, MF; Davis, J; Nowotny, JThe present work reports the electrical properties of polycrystalline Ta‐doped TiO2 (0.39 at.% Ta) determined in situ at elevated temperatures (1173‐1323 K) in the gas phase of controlled oxygen activity (10−12 Pa to 105 Pa). The effect of oxygen activity on the electrical conductivity and thermoelectric power of TiO2 is discussed in terms of defect disorder, including (1) the intrinsic electronic disorder that is governed by electronic compensation in the strongly reducing regime, (2) the extrinsic electronic disorder that is governed by electronic charge compensation in the reducing regime, and (3) the extrinsic ionic disorder that is governed by ionic compensation in the oxidizing regime. It is shown that tantalum ions are incorporated into the titanium sublattice of TiO2 leading to the formation of donor‐type energy levels. The Arrhenius‐type plot of the electrical conductivity data leads to the determination of the formation enthalpy terms. The obtained results are considered in terms of the effect of tantalum and oxygen activity on the defect disorder and the associated key performance‐related properties in the light‐induced partial water oxidation. © 2017 The American Ceramic Society
- ItemElectron backscatter diffraction characterization of plasma immersion ion implantation effects in stainless steel(Elsevier, 2013-01-15) Davis, J; Short, KT; Wuhrer, R; Phillips, MR; Lumpkin, GR; Whittle, KRIn these experiments plasma immersion ion implantation is utilised to simulate some of the radiation effects in a nuclear reactor environment. Scanning electron microscopy using the angular selective backscatter detector has revealed observable changes in crystallographic contrast after irradiation with helium ions. Further studies using electron backscatter diffraction in both plan and cross section view allow us to visualize the extent and depth of damage and observe differences in the behavior of different crystalline phases present in several grades of stainless steel. © 2012, Elsevier B.V.
- ItemFeasibility of incorporating cations and anions expected in radioactive waste streams in metakaolin-based geopolymers.(Electrical Components International, 2007-03-25) Perera, DS; Vance, ER; Aly, Z; Fuchs, A; Kiyama, S; Davis, J; Smith, SV
- ItemHe and Au ion radiation damage in sodalite, Na4Al3Si3O12Cl(Elsevier, 2014-10) Vance, ER; Gregg, DJ; Davis, J; Ionescu, MSodalite, a candidate ceramic for the immobilisation of pyroprocessing nuclear waste, showed no observable lattice dilatation in grazing incidence X-ray diffraction when irradiated with up to 1017 5 MeV He ions/cm2. However micro-Raman scattering showed considerable spectral broadening characteristic of radiation damage near the end of the ∼22 μm He range. Partial amorphism plus nepheline formation was observed in grazing incidence X-ray diffraction when sodalite was irradiated by 1016 12 MeV Au ions/cm2. Nepheline appeared less susceptible to 12 MeV Au ion damage than sodalite, with ∼25% less amorphous fraction at 1016 ions/cm2. © 2014, Elsevier B.V.
- ItemHigh-temperature corrosion of helium ion-irradiated Ni-based alloy in fluoride molten salt(Elsevier, 2015-02-01) Zhu, HL; Holmes, R; Hanley, TL; Davis, J; Short, KT; Edwards, LA comparison of the effect of helium-ion-radiation damage on a Ni–Mo–Cr–Fe alloy exposed to high-temperature (750 °C) corrosion in eutectic LiF–NaF–KF molten salt has been made. Microstructural examination showed that both the corroded-only and irradiated and corroded samples exhibit the characteristics of intergranular corrosion. However, helium ion irradiation introduces defects such as helium bubbles and cavities into the microstructure, greatly increasing intragranular corrosion of the irradiated sample. The thickness of the remaining corrosion zone for the irradiated sample was much greater than that for the unirradiated sample. © 2014 Elsevier Ltd.
- ItemIBIC microscopy – the powerful tool for testing micron – sized sensitive volumes in segmented radiation detectors used in synchrotron microbeam radiation and hadron therapies(Elsevier B. V., 2019-11-01) Pastuovic, Z; Davis, J; Tran, LT; Paino, JR; Dipuglia, A; James, B; Povoli, M; Kok, A; Perevertaylo, VL; Siegele, R; Prokopovich, DA; Lerch, MLF; Petasecca, M; Rosenfeld, AB; Cohen, DDIon Beam Induced Charge (IBIC) microscopy performed using highly tuned microbeams of accelerated ions with energies in the MeV range is the powerful tool for analysis of charge carrier transport properties in semiconductor devices based on semiconductor hetero-junction, metal-on-semiconductor and semiconductor-on-insulator configurations. Here we present two cases of recent applications of the IBIC microscopy in the field of medical radiation physics. The reduced-rate ion microbeams with energies in the MeV range and sub-micrometer spot-sizes have been used for the investigations of the charge collection efficiency (CCE) in sensitive volumes of segmented radiation detectors in order to measure the spatial distribution and uniformity of CCE in different polarization conditions. This information allows the determination of the charge carrier transport properties in selected substructures of a particular device and to quantify its ability to accurately determine the energy deposited by incident ionizing radiation - two fundamental requirements of any microdosimeter or detector of ionizing radiation. © 2019 Elsevier B.V.
- ItemImpact of pre-existing crystal lattice defects on the accumulation of irradiation-induced damage in a C/C composite(Elsevier, 2022-06) Wang, ZY; Muránsky, O; Zhu, HL; Wei, T; Zhang, Z; Ionescu, M; Yang, C; Davis, J; Hu, G; Monroe, P; Windes, WA carbon-fibre reinforced carbon-matrix (C/C) composite was irradiated with 30 MeV C6+ ions to a peak damage of ∼25 dpa. Ion irradiation-induced microstructural changes were mainly studied using Raman spectroscopy. The irradiation-induced crystal lattice defect accumulation in the C/C composite was compared with a reference of PCIB graphite (nuclear-grade). It shows that a high concentration of pre-existing crystal lattice defects in the studied C/C composite have a significant impact on the unexpectedly high disordering of the crystal lattice observed along the entire ion range. In comparison, PCIB graphite with much less pre-existing crystal lattice defects behaves in a more predictable manner with the irradiation damage accumulated in a narrow high dpa region. We rationalised that a large number of pre-existing crystal lattice defects in the C/C composite lead to a stronger electron-phonon coupling and play an important role on the formation of stable crystal lattice defects due to electronic energy loss during ion irradiation. The present results have implications for the development of C/C composites for radiation-tolerant applications, in terms of the crystal lattice defect elimination in the as-manufactured microstructure. Additionally, this investigation identifies a fundamental knowledge gap in the electronic energy loss effect on the irradiation damage produced in carbon-based materials at intermediate ion energies. © 2022 Elsevier B.V.
- ItemIn situ micro tensile testing of He+ ion irradiated single crystal nickel film(Australian Microscopy and Microanalysis Society, 2015-11-01) Bhattacharyya, D; Reichardt, A; Ionescu, M; Davis, J; Hosemann, P; Harrison, RP; Edwards, LIntroduction : Radiation damage can cause increase in strength and decrease in ductility, thus reducing the service life of structural parts in reactors. Ion beam irradiation has been a method of choice to simulate the effects of neutron irradiation in a reactor for some time now [1], since it enables the attainment of reasonable doses within hours, instead of years inside a reactor. A major problem in this method is that the damaged region is very shallow, and mechanical testing of such thin layers is extremely difficult. In this study, we have used in situ micro-tensile testing in the scanning electron microscope (SEM) to understand the effects of high energy ion beam irradiation on the mechanical properties of a single crystal nickel thin film. Experiments Single crystal Nickel foils, ~12.8-13.1 μm thick, were irradiated with 6 MeV He+ ions in the Tandetron “STAR” accelerator at ANSTO. The samples were irradiated to two different fluences – (i) 2 x 1017 ions/cm2 (peak damage of ~ 10 displacements per atom or dpa), and (ii) 3.8 x 10 17 ions/cm2 (peak damage of ~19 dpa). Damage profiles calculated using the SRIM software [2], showed that there is a long, low tail of the profile beginning at the entry face and extending to approximately 9-10 μm depth, after which the damage rises sharply (Fig. 1(a)). Micro-tensile samples of approximate dimensions 25-30 μm (l) x 10 μm (w) x 12-13 μm (h) were fabricated using a Zeiss® Auriga 60™ Cross-Beam™ instrument. The free end of the sample was milled to obtain a rectangular hole which was used as a grip. The end of the tensile device, shaped as an L shaped hook, was inserted into the aforementioned rectangular hole. The sample was then subjected to tension by applying a voltage to a piezo-electric device attached to the tensile head, causing it to move at a rate of ~20 nm/sec. SEM images were taken at regular intervals, and the strain measured using two fiducial markers, one on each side of the gauge length. Results : An image of a typical tensile sample used in these tests is shown in Figure 1(b), before the start of the test. The SEM image in Figure 1(c) shows the unirradiated sample after a tensile strain of e ~ 56%. The sample had a Y.S. of ~70- 100 MPa, and an U.T.S. of ~240 MPa (see Fig. 2). There was significant strain hardening up to the U.T.S., and subsequently it underwent plastic strain with large slip bands passing on two major sets of planes in an alternate manner. The formation of these slip bands was accompanied by small drops in the stress and increases in strain. A post- test SEM image of a sample irradiated with 6 MeV He+ ions to a fluence of ~2e17 ions/ cm2 and a peak damage of ~ 10 dpa is presented in Fig. 1(d), showing slip bands passing through the whole thickness of the sample and fracture at the lower surface, which in this case is the “exit surface” of the ions. This sample had a Y.S. of ~ 195-230 MPa, and a peak strength of ~358 MPa before first rupture at the surface near peak damage, at a strain of about 1.9% (Fig. 2). A post-test SEM image of the sample fabricated from the foil irradiated with He+ ions to a total fluence of 3.8e17 ions/ cm2 and a peak damage of ~ 19 dpa is shown in Figure 1(e). This sample showed a Y.S. of ~ 400 MPa and a peak strength of ~ 500 MPa before first rupture at the exit surface of the ions, which is the top surface in this case. Conclusions: The effect of He+ ion irradiation on the tensile strength of Ni single crystals was measured successfully by in situ micro- tensile testing of FIB-fabricated samples which included the damaged layers. The results showed increase in average strength of up to ~118 MPa for a total fluence of 2e17 ions/ cm2 and ~260 MPa for a peak damage of ~3.8e17 ions/cm2. Brittle fracture was observed in the irradiated samples at the surface nearer to the peak damage layer.
- ItemIn situ micro tensile testing of He+2 ion irradiated and implanted single crystal nickel film(Elsevier B.V., 2015-11-01) Reichardt, A; Ionescu, M; Davis, J; Edwards, L; Harrison, RP; Hosemann, P; Bhattacharyya, DThe effect of ion irradiation on the tensile properties of pure Ni single crystals was investigated using an in situ micro-mechanical testing device inside a scanning electron microscope. A 12.8 μm-thick Ni film with {0 0 1} plane normal was irradiated with 6 MeV He+2 ions to peak damage of 10 and 19 displacements per atom (dpa). Micro-tensile samples were fabricated from the specimens parallel to the plane of the film using a focused ion beam (FIB) instrument, and tested in tension along [1 0 0] direction, up to fracture. The peak strength increased from ∼230 MPa for the unirradiated material to about 370 MPa and 500 MPa for the 10 dpa and 19 dpa samples respectively, while the ductility decreased with increasing dose. The surface near the peak damage regions fractured in a brittle manner, while the regions with smaller dose underwent significant plastic deformation. Slip bands extended to the peak-damage zone in the sample with a dose of 19 dpa, but did not propagate further. Transmission electron microscopy confirmed the stopping of the slip bands at the peak-damage region, just before the high He concentration region with voids or bubbles. By removing the peak damage region and the He bubble region with FIB, it was possible to attain propagation of slip bands through the entire remaining thickness of the sample. This material removal also made it possible to calculate the irradiation hardening in the region with peak hardness – thus enabling the separation of hardening effects in the high and low damage regions. © 2015 Elsevier Ltd.
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