Browsing by Author "Murphy, T"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    Human occupation of northern Australia by 65,000 years ago
    (Springer Nature, 2017-07-20) Clarkson, C; Jacobs, Z; Marwick, B; Fullager, R; Wallis, LA; Smith, MA; Roberts, RG; Hayes, E; Lowe, KM; Carah, X; Florin, SA; McNeil, J; Cox, D; Arnold, LJ; Hua, Q; Huntley, J; Brand, HEA; Manne, T; Fairbairn, AS; Shulmeister, J; Lyle, L; Salinas, M; Page, M; Connell, K; Park, GY; Norman, K; Murphy, T; Pardoe, C
    The time of arrival of people in Australia is an unresolved question. It is relevant to debates about when modern humans first dispersed out of Africa and when their descendants incorporated genetic material from Neanderthals, Denisovans and possibly other hominins. Humans have also been implicated in the extinction of Australia’s megafauna. Here we report the results of new excavations conducted at Madjedbebe, a rock shelter in northern Australia. Artefacts in primary depositional context are concentrated in three dense bands, with the stratigraphic integrity of the deposit demonstrated by artefact refits and by optical dating and other analyses of the sediments. Human occupation began around 65,000 years ago, with a distinctive stone tool assemblage including grinding stones, ground ochres, reflective additives and ground-edge hatchet heads. This evidence sets a new minimum age for the arrival of humans in Australia, the dispersal of modern humans out of Africa, and the subsequent interactions of modern humans with Neanderthals and Denisovans. © 2017 Macmillan Publishers Limited, part of Springer Nature.
  • Thumbnail Image
    Item
    Non-destructive quality evaluation of additively manufactured metal components
    (The Minerals, Metals & Materials Society, 2020-02-26) Yang, S; Prentice, L; Murphy, T; Mayo, SC; Paradowska, AM
    Additive manufacturing (AM) is particularly important for high-value applications such as aerospace. However, due to the specific conditions of the AM process, AM components often have internal microscopic structural defects such as porosity that are difficult to detect non-destructively with current off-the-shelf technology. Conventional X-ray CT (computed tomography) imaging analysis is inadequate in resolving the microscopic porosity defects in macro-sized parts. CSIRO has developed a data-constrained modelling (DCM) technology. Together with the quantitative X-ray CT capability, it allows the resolution of fine defects in AM metal components smaller than the imaging voxels (voxel partial porosity). The technology is being further developed for macro-sized AM metal components using industrial X-ray CT facilities. The ANSTO instrument Kowari allows us to non-destructively determination residual stresses and texture within the interior of bulk engineering components. Imaging beamline Dingo and IMBL are used to assessing defects and dimensional tolerance of internal features of such components.
  • No Thumbnail Available
    Item
    Precise tuning chemistry and tailoring defects of graphene oxide films by low energy ion beam irradiation
    (Elsevier, 2020-03-01) Wei, Y; Pastuovic, Z; Murphy, T; Gore, DB
    Precise tuning chemistry and tailoring nanopores of graphene oxide (GO) thin films are vital for their application for liquid and gas separation. In this work, ultra-thin GO films with thicknesses of about 150 nm were prepared and then modified by a low energy carbon ion beam with ion fluences ranging from 1 × 1015 ions·cm−2 to 1 × 1017 ions·cm−2. An ion fluence of 1 × 1016 ions·cm−2 is a threshold for the changes to the surface geometry (i.e. the chemical state and the consequent morphology) of the GO films. Moreover, X-ray photoelectron spectroscopy (XPS) reveals that oxygen loss in ion beam-induced reduction of GO films was mainly by the elimination of the unstable C[dbnd]O species. Raman spectroscopy indicates that a mass of defects with a mean defect distance of about 1.4 nm was generated in GO films by C+ irradiation. According to SRIM simulation, an average of 208 carbon vacancies were created in the GO film per impinging C+. These results suggest that low energy carbon ion beam irradiation is promising for simultaneously reducing and drilling nanoscale pores on GO surfaces in a controllable manner, which could be used for engineering GO-based separation membranes. © 2019 Published by Elsevier B.V.