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2091 |
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Wednesday, May 05, 2010, Hullet Room 2:40 PM Biomedical and Polymer Coatings |
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Microstructures and adhesive bonding strength analysis of plasma sprayed silica modified hydroxyapatite coatings on Ti-6Al-4V substrates |
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Jinling Xu* / Nanyang Technological University , Singapore Khiam Aik Khor/ Nanyang Technological University, Jan Cizek/ Nanyang Technological University, |
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The majority of bone consists of extracellular matrix proteins and the mineral hydroxyapatite (HA). HA coating has been well characterized chemically and mechanically as its benefits are demonstrated in both short- and long-term clinical results. However, its inferior mechanical properties, slow rate of osseointegration and relatively long remodeling time limit its the in medical applications. To enhance the relatively poor properties, research studies focus on improvement of mechanical properties and biocompatibility and bioactivity of HA as the two crucial factors for the implants long-term applications. Currently, experimental syntheses of chemically modified or ion-substituted HA have drawn great interest due to the importance of the ions in developing artificial bone. Si-substituted HA became an attractive alternative to conventional HA materials for use as bone substitute compacts. It was reported that the silicate ions embedded into HA structure improved its in-vivo bioactivity and enhanced the formation of a low-crystalline surface apatite layer on HA after immersing in simulated body fluids (SBF). Current ideas concerning the role of silicon in biological functions were related to its performance in the form of silicic acid (Si(OH)4). Various approaches have been utilized to obtain Si-substituted HA. Among these, a popular method was postulated by Gibson et al by developing an aqueous precipitation technique. Alternatively, a co-substituted HA (two ion elements, e.g. lanthanum and silicon) has been prepared using high temperature solid-state methods. In this study, a small amount of silicon dioxide (~ 2wt%) was introduced into HA slurry which was subsequently spray-dried into powder. A silicon modified HA coating was then deposited onto Ti-6Al-4V alloy substrates by atmospheric plasma spraying technology. The surface chemistry was characterized through advanced analysis methods: SEM, X-ray diffraction and X-ray photoelectron spectrometry. Additionally, the adhesive bonding strength of the as-sprayed coatings were specified measured using a universal testing system. |