Abstract
Functionally gradient materials(FGM)were made for dental applications.Mixed powders with different ratios of metals(titanium, palladium)and ceramics(hydroxyapatite, zirconia)were packed into silicone rubber molds changing the concentration gradually from one end to the other.The specimens were compressed under a pressure of 400MPa by cold isostatic press(CIP)and sintered in an argon gas atmosphere by high frequency induction heating at a temperature of 1, 300℃.Mechanical tests were performed using the uniform composite sintered specimens.The relation of the mechanical properties with the micro structure was investigated by SEM observation.With increases in hydroxyapatite, the titanium-apatite specimens showed lower values in both flexural strength and deflection, but maximum values in both the elastic modulus and apparent density were found in specimens containing 95% titanium.There was a close corelation between apparent density and elastic modulus of titanium-zirconia specimens.The modes of fracture were brittle on both the flexural test and diametral test, in contrast with the ductile properties in the compressive test.At the same volumetric content, the titanium-apatite composite showed the same flexural strength as the titanium-zirconia composite, and higher values in elastic modulus and strain.By adding 5% palladium to titanium, sintering was improved and the strengthening effect of alloying was prominent at the higher range of apatite concentration.By inserting titanium plate or coil, a 50% increase of flexural strength and 80% increase of elastic modulus were obtained structurally.Using functionally gradient materials specimens in the shape of column, implants and rods were made gradually changing the ceramics content from pure titanium at one end to 50% ceramics at the other end.The micro-hardness numbers of these specimens were distributed gradually relative to the ceramics content.
