Cowley, A.

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Cowley, A.
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Cowley, A.

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  • Publication
    Evaluation and comparison of hydroxyapatite coatings deposited using both thermal and non-thermal techniques
    (Elsevier, 2013-07)
    Barry, James N. 
    ;
    Twomey, Barry 
    ;
    Cowley, A. 
    ;
    O'Neill, Liam 
    ;
    McNally, Patrick J. 
    ;
    Dowling, Denis P. 
    This paper compares the properties of hydroxyapatite (HA) coatings, obtained using two different deposition technologies on Ti–6Al–4V substrates. The deposition techniques evaluated were: atmospheric plasma spray (APS, thermal treatment) and a novel micro-blasting technique known as CoBlast (non-thermal treatment). The HA coatings were examined with respect to their morphology, crystallinity and adhesion, while the phase concentration of the metallic substrates was also analysed. In vitro cell proliferation and cell morphology studies using MG-63 osteoblastic cells were carried out on the HA coated substrates obtained using the two deposition techniques, with untreated titanium grade 5 (Ti–6Al–4V) substrates utilised as a control. XRD analysis of the CoBlast deposited HA coatings demonstrated that it was comprised of the same crystalline HA as the precursor powder. For the APS HA coatings however, additional calcium phosphate phases were observed, and these were attributed to phase changes caused by the high plasma deposition temperatures. The APS treated samples also exhibited evidence of substrate modification, with substrate conversion to a β-rich surface at the HA/substrate interface observed in the XRD analysis. CoBlast HA coatings, with an average thickness of approx. 2.5 μm, were found to have higher tensile adhesion values (33.6 and 35.7 MPa), when compared with the 5 MPa obtained for the approx. 26.9 μm thick APS coatings using a modified tensile adhesion test. This lower adhesion tensile value is most likely due to the increased residual stress generated in the HA coating during thermal plasma processing. The cell response studies on the four surfaces tested indicate that the HA surfaces exhibited higher levels of cell proliferation than the untreated titanium after 5 days, with the CoBlast surfaces displaying statically significant increases in cell proliferation.
      1125Scopus© Citations 20
  • Publication
    Influence of substrate metal alloy type on the properties of hydroxyapatite coatings deposited using a novel ambient temperature deposition technique
    (Wiley Blackwell (John Wiley & Sons), 2014-03)
    Barry, James N. 
    ;
    Cowley, A. 
    ;
    McNally, Patrick J. 
    ;
    et al. 
    Hydroxyapatite (HA) coatings are applied widely to enhance the level of osteointegration onto orthopedic implants. Atmospheric plasma spray (APS) is typically used for the deposition of these coatings; however, HA crystalline changes regularly occur during this high-thermal process. This article reports on the evaluation of a novel low-temperature (<47°C) HA deposition technique, called CoBlast, for the application of crystalline HA coatings. To-date, reports on the CoBlast technique have been limited to titanium alloy substrates. This study addresses the suitability of the CoBlast technique for the deposition of HA coatings on a number of alternative metal alloys utilized in the fabrication of orthopedic devices. In addition to titanium grade 5, both cobalt chromium and stainless steel 316 were investigated. In this study, HA coatings were deposited using both the CoBlast and the plasma sprayed techniques, and the resultant HA coating and substrate properties were evaluated and compared. The CoBlast-deposited HA coatings were found to present similar surface morphologies, interfacial properties, and composition irrespective of the substrate alloy type. Coating thickness however displayed some variation with the substrate alloy, ranging from 2.0 to 3.0 μm. This perhaps is associated with the electronegativity of the metal alloys. The APS-treated samples exhibited evidence of both coating, and significantly, substrate phase alterations for two metal alloys; titanium grade 5 and cobalt chrome. Conversely, the CoBlast-processed samples exhibited no phase changes in the substrates after depositions. The APS alterations were attributed to the brief, but high-intensity temperatures experienced during processing. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2013.
      690Scopus© Citations 12