Now showing 1 - 5 of 5
  • Publication
    Evaluation and comparison of hydroxyapatite coatings deposited using both thermal and non-thermal techniques
    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.
      1055Scopus© Citations 17
  • Publication
    Direct Plasma Deposition of Collagen on 96-Well Polystyrene Plates for Cell Culture
    A cold atmospheric plasma unit was used to deposit a biologic, in this case collagen, onto a surface. A collagen coating was applied to 96-well polystyrene plates at a range of powers to determine the effects of the plasma power on the coating structure and viability. Plasma characterization was carried out using voltage, current, and power measurements. Coating characterization was completed using gravimetric measurement, cell growth, water contact angle, as well as spectroscopic analysis and compared to commercial collagen-coated plates. Cell culture studies were also undertaken. The plasma coating matched the performance of the commercial plate but dramatically reduced production time and cost. This method could allow for automated inline production of collagen-coated plates for cell culture applications.
      69Scopus© Citations 2
  • Publication
    Wear resistance enhancement of the titanium alloy Ti6AI4V via a novel co-incident microblasting process
    A study was undertaken to investigate the potential of a novel surface modification process to enhance Ti6Al4V wear resistance. The process consists of co-incident particle streams of abrasive and dopant materials which impact a substrate to create a modified surface. Al2O3 was chosen as the abrasive and Teflon, SiC and B4C were investigated as dopants. Al2O3-SiC and Al2O3-B4C modified Ti6Al4V both exhibited increased surface hardness compared to the unmodified metal alloy. However, pin-on-disc tribometer measurements indicated that such hardening modifications exhibited no appreciable benefits in terms of wear resistance. On the other hand, Al2O3-Teflon modified Ti6Al4V demonstrated significantly reduced coefficients of friction and reduced wear rates under the same test conditions. Investigations suggest that although the Al2O3 abrasive is not incorporated into the coating, its presence is essential in order to achieve a wear resistant surface. Combinations of hard material (SiC or B4C) modifications with a further layer of Teflon resulted in further enhancement of wear resistance as increased surface hardness was allied with similar low coefficients of friction. In conclusion, a number of the surface modifications conducted have a beneficial affect on the wear resistance of Ti6Al4V. The process is also likely applicable to other metal/metal alloys such as CoCr, NiTi and stainless steels. Furthermore, the chemical-free nature and ambient temperature conditions concerned afford this process the potential to act as an attractive alternative to some of the more problematic high temperature approaches currently in use.
      672Scopus© Citations 15
  • Publication
    Comparison between shot peening and abrasive blasting processes as deposition methods for hydroxyapatite coatings onto a titanium alloy
    Recent studies have shown that combining a compressed air jet with entrained hydroxyapatite (HA) particles with a jet of abrasive particles can be used to deposit a well adhered crystalline HA coatings onto titanium substrates. A similar particle bombardment process utilising a flow of shot peen particles and a flow of suitable powder particles has been used to deposit a range of coatings, though the deposition of bioceramic powders have not yet been reported by this method. In this study a direct comparison between the shot peen and abrasive bombardment processes has been undertaken to determine which technique yields coatings exhibiting higher levels of adhesion on titanium alloy substrates. Both processes were shown to effectively deposit a layer of crystalline apatite onto the titanium substrates over a range of pressures and jet to substrate heights. It was observed that for both processes that an increase in particle kinetic energy producing corresponding enhancements in both deposition rate and surface roughness. The shot peen process however produced a smooth layer of laminar apatite, which was readily removed from the surface using a scratch adhesion test technique. In contrast the combination of a jet of HA and abrasive powders resulted in an increase in surface abrasion and increased mechanical interlocking of the HA into the metal surface was observed. The mechano-chemical affect achieved resulted in a better adhered HA layer. The surface morphology obtained using the two treatments was significantly different with an increase in the average roughness (Ra) of ≈ 70 and 80 % for samples treated with abrasive particles over shot peen. This difference in surface treatment is further highlighted by the removal of the HA using an acid etch. The roughness (Ra) of the underlying titanium layer after this removal is, on average, >175 % higher for the surface treated with the abrasive particles during HA deposition.
      936Scopus© Citations 33
  • Publication
    A comparison between gas and atomised liquid precursor states in the deposition of functional coatings by pin corona plasma
    This work directly compares vapour and liquid aerosol states for the deposition of perfluorocarbon coatings using an atmospheric pressure, non-thermal equilibrium plasma jet system. The objective of the study is to evaluate how the physical state of the precursor (gas or liquid), influences the fragmentation of the monomer molecules in the plasma and the subsequent coating properties. Specifically the effect of gas or liquid aerosol precursor feed on the ability to achieve a soft plasma polymerisation (SPP) is assessed with a view to producing a coating that exhibits minimal fragmentation, while being well crosslinked. The precursor (Perfluoro–1–Decene) was introduced into a helium plasma and coatings deposited at rates of up to 50 nm/min. The deposited coatings were examined using XPS, FTIR, contact angle and ellipsometric measurements. These indicated that a controlled polymerization reaction through the vinyl group of the monomer had taken place in the case of the gas deposited samples with only minor fragmentation of the functional perfluoro chain. Furthermore, a high level of cross-linking was achieved and the perfluorocarbon coatings were stable to a toluene wash. In contrast, while 2 coatings deposited using the liquid deposition technique showed good retention of monomer molecular structure, they exhibited poor stability when immersed in toluene. This is attributed to lower levels of cross-linking of the liquid precursor in the plasma, compared with coatings deposited using the gaseous precursor technique.
      264Scopus© Citations 20