Study On the Development of the Alumina - Rare Earth Phosphate Machinable Composites for Biomedical Applications

Abstract

Alumina, being a ceramic material, is very hard and strong, is a well-known bioinert ceramics, useful for many implant applications. But strong atomic bonding results in poor machinability in alumina, which is a useful and required property for implants as the shape and dimensional accuracy & criticality are very strict. Hence being a poorly machinable material wide applicability of alumina as implant material is restricted.
In the present work, two different grades (C and R) of commercial grade high pure alumina is studied for its machinability (drilling character) by incorporating a weak interphase material, rare earth phosphates (REP`s), namely lanthanum phosphate (LaPO4) and yttrium phosphate (YPO4). Variation of REP was studied between 10 – 50wt. % for both the aluminas. Both the phosphates were stable and found to remain inert (no reaction with alumina) on sintering upto 1600oC, making a true composite character of the alumina-REP sintered compositions. Microstructural studies showed well distributed alumina and rare earth phosphates grains after sintering. All the sintered samples were found to be drillable for all the condition. Only a threshold value of REP content was observed at 1600oC for the higher reactive alumina. Biological studies showed positive results for all the compositions studied. CAl2O3 with 30wt. % REP content sintered at 1600oC was found to be machinable with a densification of >85% and strength >150MPa.