Browsing by Author "Short, KT"
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- ItemCharge trapping and defect segregation in quartz(AIP Publishing, 1999-06-14) Stevens Kalceff, MA; Thorogood, GJ; Short, KTIrradiation induced charging of wide band gap materials may significantly influence the development of radiation damage and associated defect migration. Charge trapped at irradiation induced and/or pre-existing defects induces a localized electric field within the irradiated volume of specimen. The powerful combination of cathodoluminescence microanalysis and electric force microscopy allows direct monitoring of the development of the irradiation induced charge distribution and its effect on the microscopic spatial segregation of defects. These techniques have been used to demonstrate the important influence of the induced local field on the microscopic defect structure of quartz. © 1999 American Institute of Physics
- 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.
- ItemThe electronic structure of S-layer proteins from Lactobacillus brevis(IEEE, 2008-07-28) Graham, SM; Asquith, NL; Wilde, KL; Short, KT; Holden, PJ; Stampfl, APJ; Holmes, AJ; Ruys, AJ; Stojanov, P; Riley, JD; Fang, LJ; Yang, YW; Hwu, YKThe valence electronic structure of the S-layer of Lactobacillus brevis is determined using synchrotron-based photoelectron spectroscopy and soft X-ray absorption spectroscopy. Spectra are compared to experimental work on amino-acids and S-layers of Bacillus sphaericus. While it is indeed possible to identify energy levels with those of natural amino-acids, distinct energy shifts are indeed observed which cannot be reconciled using such simple comparisons. Furthermore a strong nitrogen signal observed in both the occupied and unoccupied energy levels suggests that the Lactobacillus brevis protein is amine-terminated. A discussion of the surface of this protein is given. © 2008 IEEE
- ItemEnhanced adhesion of atomic layer deposited titania on polycarbonate substrates(Elsevier, 2007-01-22) Latella, BA; Triani, G; Zhang, Z; Short, KT; Bartlett, JR; Ignat, MInterfacial adhesion of atomic layer deposited titania films on polycarbonate substrates with and without a water-plasma treatment has been studied using in situ observation during microtensile testing. Specific attention is paid to multiple tension-generated transverse cracks in the titania films when subjected to externally applied uniaxial tensile stresses. The strength, fracture toughness and interfacial adhesion of the titania film on polycarbonate were deduced from theoretical models based on experimentally determined parameters. The tensile tests were conducted in a micromechanical tester positioned under an optical microscope allowing in situ viewing of cracking damage. The strain to initiate first cracking and the crack density as a function of strain were obtained. The in situ observations indicated different interfacial behaviour between water-plasma-treated and non-treated samples. It is shown that the water plasma treatment drastically improves the adhesion of the titania film to polycarbonate. Calculations show that the fracture energy required for film debonding in the plasma-treated polycarbonate is 5.9 J/m2 compared to 2.5 J/m2 for the untreated sample. A simple chemical structure model was used to explain the observed differences. © 2007, Elsevier Ltd.
- 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.
- ItemIn situ electrochemical etching and examination by SPM of titanate ceramics(Australian Society for Electron Microscopy, 2002-02-04) Thorogood, GJ; Short, KT; Zhang, YJThe aqueous durability of titanate related ceramics is of great importance for the immobilisation of high level radioactive waste-in order to observe the reaction progress at the solid-liquid interface of these durable ceramics, we have attempted to accelerate the dissolution process via electrochemical means by using a SPM cell with electrochemical capability. The experiment involves placing a titanate ceramic disk (with flat polished surfaces) in the electrochemical cell. The cell is then set up with the ceramic acting as one electrode and another electrode being placed in the solution. In a flow through cell it is possible to select the pH and observe the change, not only in surface morphology as dissolution occurs, but also the frictional characteristics of the surface. The SPM tip plays no role in the electrochemical reaction. We will be presenting results from our work and discussing possible mechanisms for dissolution and future directions of the work. ©2002 Australian Society for Electron Microscopy Inc
- ItemIn situ micro-Raman analysis and x-ray diffraction of nickel silicide thin films on silicon.(Elsevier, 2009-01) Bhaskaran, M; Sriram, S; Perova, TS; Ermakov, V; Thorogood, GJ; Short, KT; Holland, ASThis article reports on the in situ analysis of nickel silicide (NiSi) thin films formed by thermal processing of nickel thin films deposited on silicon substrates. The in situ techniques employed for this study include micro-Raman spectroscopy (μRS) and X-ray diffraction (XRD); in both cases the variations for temperatures up to 350°C has been studied. Nickel silicide thin films formed by vacuum annealing of nickel on silicon were used as a reference for these measurements. In situ analysis was carried out on nickel thin films on silicon, while the samples were heated from room temperature to 350°C. Data was gathered at regular temperature intervals and other specific points of interest (such as 250°C, where the reaction between nickel and silicon to form Ni2Si is expected). The transformations from the metallic state, through the intermediate reaction states, until the desired metal–silicon reaction product is attained, are discussed. The evolution of nickel silicide from the nickel film can be observed from both the μRS and XRD in situ studies. Variations in the evolution of silicide from metal for different silicon substrates are discussed, and these include (1 0 0) n-type, (1 0 0) p-type, and (1 1 0) p-type silicon substrates. © 2009, Elsevier Ltd.
- ItemThe influence of fly ash morphology and phase distribution on collection in an electrostatic precipitator(Australian Institute of Physics, 2006-12-08) Metcalfe, R; Connor, J; Druskovich, D; Blackford, MG; Short, KTFly Ash is the unburned portion of fuels which is carried away as solid particles in the hot gas stream of a furnace. It is of concern as a medium for the transport of heavy metal and other pollutants into the atmosphere, but has found application in cement manufacture and elsewhere. About 99% of the fly ash produced in a typical power station is removed by electrostatic precipitators or baghouse filters at the base of the emission stack. Precipitator efficiency is dependent on the charging properties of the fly ash particles and the adhesive forces between them. These forces in turn depend on the size, morphology, chemical constitution and phase distribution of the fly ash. X-ray diffraction (XRD) results indicate that about two thirds of the material from a typical Central Queensland power station is non-crystalline, mostly alumino-silicate glassy spheres; the remainder crystalline, mostly mullite, quartz, and iron oxides. Electron Microscopy shows fewer crystalline particles than expected from XRD and it is hypothesized that the crystalline material is largely embedded in the larger particles. Larger particles are usually found as aggregates held together by bridging material which may be small glassy particles, graphite sheets, or a mixture of amorphous material and small crystallites. Scanning probe microscopy gives indication of the nature and magnitude of the forces between particles, which is critical in forming the aggregates mentioned above, and in adhesion of the fly ash particles to the collector plates of the precipitator, and to one-another, and essential to the collection process.
- ItemInvestigation and modeling of electric field gradients by electric force microscopy (EFM)(CRC Press, 2000-07-08) Thorogood, GJ; Short, KT; Stevens Kalceff, MAElectric Force Microscopy (EFM) is a relatively new and and powerful method of Scanning Probe Microscopy. It can be used to study electric field gradients on a microscopic scale e.g. trapped charge in quartz [1]. EFM images are generated by monitoring the changes in the phase of a vibrating metal coated cantilever interacting with the local electric field at the sample surface. Qualitatively the phase shift is related to the strength of the field and its ability to dampen the vibration of the cantilever. Quantification of the observed phase shift due to the magnitude of the field depends on resonance properties such as spring constant and the coating for each individual tip. In an attempt to better understand the relationship between the static charge in the surface and the probe work has been performed with an electric field standard. [2] The standard was composed of a patterned metal layer on a flat alumina substrate with an alumina film of thickness approximately 1 μm applied over the metal layer. This was to ensure the metal layer was insulated and conduction between them and the probe could not occur, which would lead to loss of charge. A wire was attached to an uncoated area on the metal layers to allow them to be positively charged. The charge was supplied by a power which was capable of generating different wave functions at different frequencies and voltages. EFM images where then collected in the area immediately above the metal layers and away from the metal layers to view the effect of vertical and horizontal separation on the interaction between tip and sample. The standard performed relatively well but its surface was very rough, which affected the phase images. A second standard has been made using silicon oxide as the substrate to allow the conducting layers on the surface to be produced using electron beam lithography. By removing the interaction of the surface with the tip and by using a standard with known properties we can investigate the interaction between the cantilever and the electric field. References [1] Stevens Kalceff M A, Thorogood G J and Short K T., 1999 J App Phys. [2] Thorogood G J, Short, K T and Stevens Kalceff M A, 2000 Proc 16th Australian Conf. on Electron Microscopy p121 © 2000 Informa UK Limited
- ItemIon beam irradiation effects in strontium zirconium phosphate with NZP-structure type(Elsevier Science BV, 2014-03-01) Gregg, DJ; Karatchevtseva, I; Thorogood, GJ; Davis, J; Bell, BDC; Jackson, M; Dayal, P; Ionescu, M; Triani, G; Short, KT; Lumpkin, GR; Vance, ERCeramics with the sodium zirconium phosphate or NZP type structure have potential as nuclear waste form and inert matrix materials. For both applications the material will be subjected to self-radiation damage from alpha-decay of the incorporated actinides. In this study, ion-beam irradiation using Au- and He-ions has been used to simulate the consequences of a-decay and the effects of irradiation on the structural and macroscopic properties (density and hardness) have been investigated. Irradiation by Au-ions resulted in a significant volume contraction of similar to 7%, a reduction in hardness of similar to 30% and a loss in long-range order at fluences above 10(14) Au-ions/cm(2). In contrast, little effect on the material properties was noted for samples irradiated with He-ions up to a fluence of 10(17) ions/cm(2). Thermal annealing was investigated for the highest fluence Au-ion irradiated sample and significant decomposition was observed. © 2014, Elsevier Ltd.
- ItemIrradiation behaviour of α2 and γ phases in He ion implanted titanium aluminide alloy(Elsevier, 2014-07-01) Zhu, HL; Wei, T; Blackford, MG; Short, KT; Carr, DG; Harrison, RP; Edwards, L; Seo, DY; Maruyama, KA Ti–45Al–2Nb–2Mn + 0.8 vol.% TiB2 (at.%) alloy with fully lamellar microstructure consisting of hexagonal-close-packed (hcp) α2 and face-centred-tetragonal (fct) γ phases was irradiated by implanting helium ions to different fluences. Microstructural examination showed that helium cavities are formed in both the α2 and γ phases after He-ion irradiation. However, the helium cavities and their size change with fluence are much larger in the α2 phase than those in the γ phase, indicating that the γ phase exhibits better tolerance to the He-ion irradiation than the α2 phase. Since α2 and γ phases have different crystal structures, they possess differences in helium solubility and interstitial migration. These differences are responsible for the variation in radiation damage behaviour between the two phases. © 2014, Elsevier Ltd.
- ItemMicrostructural and compositional analysis of strontium-doped lead zirconate titanate thin films on gold-coated silicon substrates(Cambridge University Press, 2009-02) Sriram, S; Bhaskaran, M; Mitchell, DRG; Short, KT; Holland, AS; Mitchell, AThis article discusses the results of transmission electron microscopy (TEM)-based characterization of strontium-doped lead zirconate titanate (PSZT) thin films. The thin films were deposited by radio frequency magnetron sputtering at 300°C on gold-coated silicon substrates, which used a 15 nm titanium adhesion layer between the 150 nm thick gold film and (100) silicon. The TEM analysis was carried out using a combination of high-resolution imaging, energy filtered imaging, energy dispersive X-ray (EDX) analysis, and hollow cone illumination. At the interface between the PSZT films and gold, an amorphous silicon-rich layer (about 4 nm thick) was observed, with the film composition remaining uniform otherwise. The films were found to be polycrystalline with a columnar structure perpendicular to the substrate. Interdiffusion between the bottom metal layers and silicon was observed and was confirmed using secondary ion mass spectrometry. This occurs due to the temperature of deposition (300°C) being close to the eutectic point of gold and silicon (363°C). The diffused regions in silicon were composed primarily of gold (analyzed by EDX) and were bounded by (111) silicon planes, highlighted by the triangular diffused regions observed in the two-dimensional TEM image. © 2009, Cambridge University Press
- ItemModification of surface and barrier properties of polyethylene terepthalate and polycarbonate plastics by ion implantation(Australian Institute of Physics, 2005-02-04) Doolan, KR; Evans, PJ; Short, KTPET is used to produce a wide range of packaging for foods and beverages. Because oxygen can diffuse through it[1, 2, 3], PET is not suitable for fabrication of bottles for the storage of beer and red wine which are both degraded by oxygen. To store oxygen degradable foods for extended periods of time in PET packaging, oxygen diffusion through the PET must be prevented by incorporating a barrier layer or barrier polymer[1] into the PET matrix. We have begun a study of diffusion of light gases through samples of PET film that have been ion-implanted with aluminium and silicon ions to determine how dose level of these ions affects diffusion rate of helium and other gases through PET film. Polycarbonate (PC) is used to produce plastic products that have high toughness, high optical clarity and good resistance to UV degradation. However, PC sheet scratches easily because it is relatively soft. If PC sheet can be surface hardened to achieve scratch resistance similar to that of Perspex, it could be used to replace products, such as aircraft windows, currently fabricated from Perspex with tougher products fabricated from PC. Ion-implantation is one method that can be used to increase surface hardness and decrease surface wear rate [4]. © 2005 Australian Institute of Physics.
- ItemNew duplex process for corrosion protection by PI3.(Elsevier, 2008-06-30) Short, KT; Zhang, Z; Finnie, KS; Collins, GA; Figueroa, CAIn this work, we report a study of a novel duplex process for corrosion protection using a CNx coating on a nitrided martensitic stainless steel by plasma immersion ion implantation (PI3). The morphology, chemical composition and electronic properties of the coating and the interface between the coating and nitrided metal were studied by SEM, EDS, Raman and XPS techniques. The corrosion behaviour of the samples was studied by electrodynamics measurements. The degradation of the corrosion resistance introduced by the PI3 plasma nitriding treatment of commercial metal alloy AISI 420 is reverted by coating the surface with an additional CNx film. © 2008, Elsevier Ltd.
- ItemRadiation damage in anatase and rutile with impurities(Australian Institute of Physics, 2009-02-04) Bertinshaw, J; Aughterson, RD; Thorogood, GJ; Short, KT; Whittle, KRNot available
- ItemRelationship between damage and hardness profiles in ion irradiated SS316 using nanoindentation–experiments and modelling(Elsevier, 2016-11) Saleh, M; Zaidi, Z; Hurt, C; Ionescu, M; Short, KT; Daniels, JE; Bhattacharyya, D; Munroe, P; Edwards, LIn this work, the authors apply the “top-down” nanoindentation testing method to assess the mechanical property changes in ion-irradiated metallic alloys for three different ion energies in order to understand the relationship between ion energy, damage peak depth and hardness peak depth. The samples were irradiated with He+2 ions having 1, 2 and 3 MeV beam energies respectively. The curves for ΔH (radiation induced hardness) have been obtained by calculating the difference of the irradiated and unirradiated hardness curves after these were corrected for indentation size effect. Three-dimensional analytical and numerical models have been developed to obtain greater insight into the mechanisms involved in the nanoindentation processes, the nature of the plastic zone, and how these affect the hardness results, including the full hardness profiles with respect to depth. This is particularly valuable in situations where the damage profile is non-uniform, as in the present case, and provides the means to predict expected hardness peak positions and values for a given irradiation dose. Copyright © 2017 Elsevier B.V.
- ItemSearch for an anomalous near-surface yield deficit in Rutherford backscattering spectra from implanted germanium and silicon(Australian Atomic Energy Commission, 1983-09) Lawson, EM; Williams, JS; Chivers, DJ; Short, KT; Appleton, BRRutherford backscattering and channelling analysis of high-dose room-temperature ion-implanted germanium has revealed an anomalous near-surface yield deficit. Implant dose and species dependencies and the effect of annealing have been examined. A marked loss of implanted impurity was also noted. The yield deficit is attributed to the absorption of oxygen and other light mass contaminants into a highly porous implanted layer upon exposure to air. Loss of implant species is attributed to enhanced sputtering effects.
- ItemSEM and EBSD studies of ion implanted stainless steel(Committee of Asia-Pacific Societies of Microscopy, 2012-02-07) Davis, J; Short, KT; Wuhrer, R; Phillips, MR; Lumpkin, GR; Whittle, KRResearch is currently in progress to determine the effect ion irradiation at varying energy and fluence has on the microstructure of several grades of stainless steel. Plasma Immersion Ion Implantation (PI3) and the Small Tandem for Applied Research (STAR) accelerator have been employed in this research to simulate some of the effects from a neutron irradiation environment using helium ions. The overall aim of the research is to eventually investigate other unique materials that have applications in both GenIV and fusion reactor programs and the Advanced Fuel Cycle Initiative (AFCI), e.g., inert matrix fuels, reactor core liners, and structural materials within the reactor (ODS materials). The main focus of this work will be to study the microstructure and understand grain boundary interactions, and how they relate to the tolerance of materials to damage.
- ItemStudies of high dpa ion beam irradiation effects on fcc AA-6061 and fcc-bcc duplex steel 2205: micromechanical modelling and nano-indentation examination of hardness variations(Karlsruhe Institute of Technology, 2015-05-10) Saleh, M; Munroe, P; Short, KT; Edwards, LThe irradiation effects of high dpa and the ramification on the engineering assessment of reactor components in GEN IV systems is of considerable interest. Most polycrystalline metallic materials derive their strengths from the interactions of dislocations with defects such as solid solution alloying elements, interstitial elements, other dislocations, grain boundaries and sub-microscopic precipitates. Irradiation of metals and alloys at temperatures below those that anneal their defects typically produces pronounced radiation hardening, this is investigated herein to better understand the application of complex alloys in future reactor systems. . The current study focuses on ion beam irradiation of AA6061 and Duplex steel 2205, utilising the ANATRES Accelerator at ANSTO with 12 MeV Au+5 ions used as the irradiating ions. To induce a 100 dpa damage, often cited as the operating level of GEN IV reactor, heavy Au+5 ions are necessary as self-ion irradiation would fail to induce the required damage. The main attribute of ion irradiation is the rapid accumulation of end of life doses over a short duration.. Conversley, neutron irradiation experiments in thermal test reactors may accumulate damage at a rate of 3–5 dpa year, e.g. the ANSTO OPAL reactor with 20 MW is capable of 100 MeV with reactor face neutron thermal flux of 4.0E10 n/cm2/s thus resulting in a less than optimal 2 dpa per year. A key question still exits between the complementarity of neutron and ion irradiation with respect to the nature of damage, size, density and distribution of dislocation loops; black dots; and the extent of the dislocation networks. Although the same number of displacements can be produced using ion irradiation, there are differences in spatial defect distribution between thes e teh two. The post-irradiation measurements in effect quantify the final state of damage and the neutron-ion equivalence without an evaluation of the damage path. The simulation code Stopping and Range of Ions in Materials (SRIM) is used to model the irradiation process and compute the initial required experimental flux. Post irradiation studies of the micromechanical behaviour are done through nano-indentation (to a depth of 300 nm) using a diamond Berkovich tip. This allows for estimates of moduli and relative estimates of the strengths and hardening of individual phases and individual grains within a multiphase alloy. The results show a marked increase in the hardening of AA 6061 with a more modest increase in the Duplex steel 2205. Coupling these results to micromechanical FEA and crystal plasticity modelling, the authors hope to better describe the role of multi-scale modelling in complementing micromechanical testing and the extrapolation of results for engineering assessment.
- ItemTheoretical and experimental Raman spectroscopic studies of synthetic thorutite (ThTi2O6)(Elsevier, 2014-03-01) Zhang, YJ; Čejka, J; Karatchevtseva, I; Qin, MJ; Kong, L; Short, KT; Lumpkin, GR; Middleburgh, SCRaman spectra of synthetic non-substituted and U/Np/Pu- substituted thorutite (ThTi2O6) samples were collected. Factor group analysis was used to analyse the possible vibration modes. Theoretical simulations based on density functional theory (DFT) were performed on both CeTi2O6 and ThTi2O6. All possible vibrational modes for thorutite have been identified and assigned to the measured spectra. The presence and the effect of higher valence of U in thorutite has been discussed and the U–O bond lengths have been calculated by using the measured wavenumbers of ν1 (UO2)2+ symmetric stretching vibrations. The presence of U6+ in uranyl form can be inferred from the wavenumbers of U–O vibrations. Corresponding Np–O and Pu–O vibrations were not observed in the Raman spectra. Thus the presence of Np6+ and Pu6+ in the studied samples was not established. © 2016 Elsevier B.V.