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Low temperature bonding of ceramics by sol-gel processing
(Kluwer Academic Publishers, 2000-12) Barbé, CJ; Cassidy, DJ; Triani, G; Latella, BA; Mitchell, DRM; Finnie, KS; Bartlett, JR; Woolfrey, JL; Collins, GA
Sol-gel bonds were produced between smooth, clean silicon or polycrystalline alumina substrates by spin-coating solutions containing partially hydrolysed silicon alkoxides onto both substrates. The two coated substrates were assembled and the resulting sandwich was fired at temperatures ranging from 300 to 600°C. The influence of the sol-gel chemistry on the film microstructure and interfacial fracture energy was investigated using a wide range of techniques, including ellipsometry, FTIR, TG-DTA, rheology, TEM and micro-indentation. For silicon wafers, an optimum water-alkoxide molar ratio of 10 and hydrolysis water pH of 2 were found. Such conditions led to relatively dense films (>90%), resulting in bonds with significantly higher fracture energy (3.5 J/m2) than those obtained using classical water bonding (typically 1.5 J/m2). Aging of the coating solution was found to decrease the bond strength. Poly-crystalline alumina substrates were similarly bonded at 600°C; the optimised silica sol-gel chemistry yielded interfaces with fracture energy of 4 J/m2. © 2000 Kluwer Academic Publishers.
Neutron diffraction study of the Cr84.7Re15.3 alloy
(AIP Publishing, 2021-01-22) Jacobs, BS; Prinsloo, ARE; Venter, AM; Sentsho, ZN; Studer, AJ; Sheppard, CJ
Measurements of the temperature dependence of electrical resistance (R) and neutron powder diffraction (NPD) of a Cr84.7Re15.3 alloy is reported. The magnetism originates from the formation of a spin-density-wave (SDW) as a result of nesting between the electron and hole sheets at the Fermi surface (FS). NPD revealed the magnetic character of the SDW to be commensurate (C) with the lattice with a Néel temperature (TN) of 560 ± 5K that correlates to TN = 585 ± 5K determined from the saddle point in the R(T) results. A power law fit Iα(1−TTN)2β of the neutron data gave β = 0.36(1), indicating that the AF ordering follows the 3D Heisenberg model. An additional antiferromagnetic magnetic contribution, associated with Cr2O3, was observed to co-exist in the alloy. Quantification analyses revealed that the Cr2O3 content was less than 2 wt.%. A β value of 0.30(1) was determined for the magnetic phase transition of Cr2O3 in correspondence with the 3D Ising model. © 2021 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license.
A comparison of the constitutive response of austenitic and ferritic steels under welding processes
(Trans Tech Publications, 2017-08) Hamelin, CJ; Muránsky, O; Smith, MC; Edwards, L
The need to accurately measure and predict weld residual stresses (WRS) has led to several examinations intent on developing best-practice guidelines in the assessment of welded structures. The present investigation examines two benchmark weld specimens; both specimens are autogenous edge-welded beams, with welds deposited using a mechanised tungsten inert gas process. However, one of the beams was made from AISI 316LN austenitic steel, while the other was made from SA508 Gr.3 Cl.1 ferritic steel. Considerable differences in the cross-weld residual stress profile were observed between the two beams, prompting a detailed examination of why such differences exist. Computational weld mechanics was used to assess both processes; model validation was achieved using previously reported WRS and micro-hardness measurements. A comparison of the numerical solutions indicates that the shape misfit resulting from a sharp weld-induced thermal gradient causes significant longitudinal tensile stresses in the heat-affected zone in both specimens. The presence of influential solid-state phase transformations in the ferritic specimen leads to the formation of compressive stresses in the weld metal, while the stresses remain tensile in the weld metal region of the austenitic specimen. The compressive stresses in the ferritic specimen serve to offset the tensile stresses in the HAZ, leading to a reduction of the self-equilibrating WRS present in the ferritic parent metal. © 2017 Trans Tech Publications Ltd
Ion beam methods to determine trace heavy metals concentrations and sources in urban airsheds
(Elsevier, 2002-05) Cohen, DD; Stelcer, E; Garton, DB
Unique data for Australia on the concentration of selected metals in fine particle ambient air pollution is presented for urban, industrial and rural sites along 300 km section of the eastern coast line of Australia around Sydney. IBA techniques were used to determine over 25 different chemical species in the air including, H, C, N, O, F, Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Br, Se and Pb. This included many trace metals at concentrations around 1 ng/m3 of air sampled. © 2002 Elsevier Science B.V.
Nuclear-related materials and technology research at ANSTO
(ASME International, 2016-12-01) Law, M; Bendeich, PJ; Muránsky, O; Payten, WM; Hamelin, CJ
Current and future nuclear technologies such as fission and fusion reactor systems depend on well characterized structural materials, underpinned by reliable material models. ANSTO is pursuing research into the nuclear power cycle on many fronts, including: modelling and measurement of weld residual stresses; simulation of radiation damage by molecular dynamics modelling; assessment of radiation, cycling and aging effects in power plant structural materials; and characterization of materials for the next generation of nuclear power plants. Several examples of past and current research activities are used to highlight the potential of ANSTO facilities, techniques and capabilities available for collaborative research in the nuclear space. © 2016 by ASME

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