| dc.description.abstract | Bioceramics have been developed for implants to repair damaged tissues of the human
musculo-skeletal system. The clinical success of a bioceramic implant depends largely
on the chemical response at the implant interface in addition to the sufficiency of the
mechanical properties for the application. The present study combines the
developments in the fields of bioceramic materials and laser surface micro structuring of
materials.
Bioceramic hydroxyapatite powders (HA, Formula: CaIO(PO4)6(OH)2) have been
produced by emulsion technology and freeze-drying methods exhibiting BET specific
surface areas >148 m2 /g and particle sizes <13 nrn prior to thermal treatment. The
powder yield has been doubled using an increased reaction temperature of 25 *C from
17 *C, with a small increase (< 4nm) in the average particle size. HA discs that were
>95.5 % dense have been achieved after isostatic pressing with pressure of 0.59 MPa
and pressurelesss intering at 1200 *C for 2 hours. No chemical decomposition was
detected using X-ray Diffraction Analysis (XRD).
Methods of chemically enhanced laser-assisted etching have been developed to produce
microstructural features on the surface of bioceramic HA discs that were 78.5 % dense
(2482.95 kr
,
/M3 measured density). The use of 10 MPa SF6 at laser fluencies in the
range of 14.50-15.20 W/M2 produced a columnar topography with individual structures
featuring 10-20 pm height and 8-12 pm width as characterised by Scanning Electron
Microscopy (SEM). Chemical characterisation by X-ray microdiffraction, Energy
Dispsersive, X-ray analysis (SEM-EDS), Fourier Transformed Infrared spectroscopy
(FTIR) and Raman spectroscopy (Raman) found the microtopography to be composed
of fluorine-substituted HA (FHA). Alternatively the use of 80 MPa NH3 at laser
fluencies in the range of 17.17-18.50 kj/m 2 produced an irregular surface of scattered
porous hillocks that remained chemically unchanged in composition but exhibited four
times as many surface hydroxyl groups. In both cases the mechanical and chemical
stability of the bulk composition is maintained and the surface of increased surface area,
in addition to the presence of concavities and pores is likely to be of enhanced
osteoconductivity. | en_US |
