Insights into structural characterisation and thermal properties of compositionally equivalent vapour-condensed and melt-quenched glasses

Physical vapour deposition of Phosphate-based glasses enables their application onto load bearing implant surfaces for their potential to enhance osseointegration by leaching therapeutic ions at the bone/implant interface. Structural understanding with respect to processing parameters will prove useful in the on-going production of multi-functional coatings for antibacterial ion release and osseous tissue integration. This study highlights significant differences in short-range structural variation between vapour condensed and conventional melt-quenched phosphate glasses, via P-31 MAS-NMR, XPS, FTIR and DTA. Three coating compositions containing P2O5 - 32.5, 34 and 37 mol% showed greater bulk network polymerisation based on the presence of (23% to 45% Q(2) species) versus (9% to 32% Q(2) species) in melt-quenched glasses as determined by NMR. The proportion of P-O-P bridging oxygens as suggested by XPS on the surface of coatings remained consistent at (34% to 35%) forming (PO3) metaphosphates (Q(2)), whilst P-O-P bonding in melt-quenched glasses increased from (12% to 18%) and were found to form (PO4)(3-) orthophosphates (Q(0)) and (P2O7)(4-) pyrophosphates (Q(1)). AFM analysis of the coating surfaces showed nano-topographical changes due to etch pitting, which led to Ra increases from 19 nm to 167 nm, which correlated to an increased deposition rate and therefore bombardment energy. (C) 2016 Published by Elsevier Ltd.