Browsing by Author "Ruys, AJ"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Analysis of compositionally ungraded FGM analogues: Neutron diffraction measurements of residual stress and mechanical testing of pressure sintered Mo-Y2O3 and Mo-Al2O3
    (Karlsruhe Institute of Technology, 2015-05) Saleh, M; Chavara, D; Toppler, K; Alexander, J; Ruys, AJ; Kaveh, K; Luzin, V
    Functionally graded materials (FGMs) are a type of naturally inspired composite materials whose properties (e.g. microstructure, chemical or phase composition) vary over one or more dimensions. The FGMs were first proposed as an advanced engineering material in 1972 and research into application for Biomaterials, Aerospace, Chemical Plants, Mining, and Building material commodities[1, 2] is ever present. Within the nuclear industry FGMs can be engineered to effectively resist corrosion, radiation and are a potential choice for nuclear reactor components e.g. first wall for fusion reactors and fuel pellets. Additionally FGM’s have been proposed as potential plasma facing components (PFC) whereby the PFC would gradually vary from a refractory material (tungsten, plasma face) to a heat sink material (copper, coolant side). In the case of a metal-ceramic FGM, the composite mates the strength and ductility of a metal with the hardness and toughness of a ceramic [3-5]. The authors have sought to elucidate the development of residual stress in FGMs using neutron measurements on the Kowari Strain Scanner, ANSTO for the Mo-Y2O3 and Mo-Al2O3 system. Due to their extreme gradients FGM’s are not optimal for fast neutron measurements due to the high spatial resolution requirements and long measurement times. An alternative approach was employed to examine compositionally ungraded analogues of varying metal-ceramic ratios. All sample were manufactured using constituent powders, mixed and subsequently sintered using a hot press with close monitoring of the sintering curve. Optical microscopy and scanning electron microscopy were used to look at the resultant samples to observe the grain growth and the defect-like cracks attributable to the thermally induced stresses. Relaxation due to micro cracking and micro-fracturing are evaluated in light of the neutron residual stress measurements and mechanical strength measurements of : (a) bending stiffness using a three point bend tests, (b) bulk modulus through GrindoSonic techniques and (c) statistically averaged micro-hardness. Further evaluation of the residual stress is done through comparison between established analytical models, neutron diffraction and preliminary FEA. The major contribution of residual stress are further realised and evaluated in light of the interfacial instabilities present and the appropriate ways to optimise the thermal protection characteristics of a compositional gradient.
  • No Thumbnail Available
    Item
    DLC coatings: effects of physical and chemical properties on biological response
    (Elsevier, 2007-03) Ma, WJ; Ruys, AJ; Mason, RS; Martin, PJ; Bendavid, A; Liu, ZW; Zreiqat, H; Ionescu, M
    Recent trials on diamond-like carbon (DLC) coated medical devices have indicated promise for blood interfacing applications. The literature is sparse regarding structural and compositional effects of DLC on cellular response. An important goal in optimizing blood-interfacing implants is minimal macrophage attachment, and maximal albumin:fibrinogen adsorption ratio. DLC coatings deposited by PACVD and FAD, were analysed with respect to sp(3) content (EELS), hydrogen content (ERDA), surface composition (XPS), surface roughness (AFM), surface energy, albumin: fibrinogen adsorption ratio, and macrophage viability and attachment. We found that increasing surface roughness and surface energy enhanced the macrophage viability and the albumin: fibrinogen adsorption ratio. We also found that the higher the hydrogen content for a-C:Hs deposited by PACVD, the lower the albumin:fibrinogen adsorption ratio, and macrophage attachment. This suggests that hydrogen content may be an important factor for influencing the biological response of DLC surfaces. Macrophage cells spread well on all DLC surfaces, and the surface results indicated the non-toxic nature of the surfaces on the cells at the time points tested. © 2007, Elsevier Ltd.
  • No Thumbnail Available
    Item
    The 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, YK
    The 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
  • Thumbnail Image
    Item
    Neutron diffraction measurements of residual stress and mechanical testing of pressure sintered metal-ceramic composite systems
    (Materials Research Forum LLC., 2016-12-22) Toppler, K; Luzin, V; Saleh, M; Ruys, AJ; Kabir, K; Chavara, DT
    Abstract. Functionally graded materials (FGMs) are composite materials which vary in phase composition, microstructure and properties over one or more dimensions. They are a good potential choice for nuclear reactor components as they can be engineered to effectively resist corrosion and radiation damage. In the case of a metal-ceramic FGM, they can mate the strength and ductility of a metal with the hardness and toughness of a ceramic. A series of composite samples of variable metal-ceramic ratios was manufactured by hot uniaxial pressing in cylinders. Bulk uniform samples of a certain composition were manufactured as a more efficient way of studying FGMs without the extreme gradient required in practical applications. Thermally and mechanically generated stresses, inherent in composites, frequently create conditions for micro-cracking development, depending on the material’s micro-structural characteristics and the thermo-mechanical processing route. Bulk stress measurements in the prepared samples were carried out on the Kowari diffractometer on the OPAL reactor at ANSTO. Both phases – metal matrix and ceramic inclusions – were measured in both axial and lateral directions for full characterisation of the composite stress state. When compared against analytical evaluation, experimental results, for some samples, demonstrated significant stress relaxation with micro-cracking being the main suspect. Copyright © 2016 by the author(s)