Investigation of the influence of processing parameters on the properties of bioceramic materials based on calcium hydroxyapatite and calcium phosphate obtained by different sintering technique

Kalcijum-fosfatni biokeramički materiali na bazi kalcijum-hidroksiapatita (HAP) i trikalcijum-fosfata (TCP), zahvaljujući hemijskom sastavu, biokompatibilnosti, bioaktivnosti i osteokonduktivnosti imaju značajnu ulogu pri izradi koštanih implanta. Guste nanostrukturne i kontrolisano porozne forme biokeramičkih materijala na bazi hidroksiapatita i kalcijum-fosfata imaju veliku primenu u maksiofacialnoj, dentalnoj i ortopedskoj praksi. Pažljiva kontrola faznog sastava, veličine zrna, oblika i dimenzija pora, kao i mehaničkih svojstava sinterovanih biokeramičkih materijala jesu ključni faktori za dobijanje implanata optimalnih svojstava. Danas je ogroman broj istraživanja baziran upravo na definisanju optimalnih uslova procesiranja sa ciljem da se dobiju gusti i kontrolisano porozni biokeramički monofazni kalcijum-hidroksiapatitni i bifazni materijali na bazi HAP i TCP, pogodni za ugradnju u ljudski organizam. Cilj ove doktorske disertacije bio je proučavanje procesa formiranja gustih nanostrukturnih biokeramičkih materijala na bazi kalcijum-hidroksiapatita i kalcijum-fosfata mikrotalasnim sinterovanjem, spark plazma sinterovanjem i toplim presovanjem, polazeći od stehiometrijskih i kalcijum deficitarnih nanočestičnih prahova kalcijum-hidroksiapatita dobijenih modifikovanim precipitacionim sintezama. Ispitan je uticaj svojstava polaznih prahova HAP i parametara procesiranja na mikrostukturne i fazne karakteristike, kao i na mehanička svojstva dobijenih gustih sinterovanih biokeramičkih materijala. Definisan je uticaj mikrostrukturnih parametara na žilavost i tvrdoću dobijenih monofaznih i bifaznih biokeramičkih materijala. Nanoindentacijom je utvrđen uticaj veličine zrna i faznog sastava na nanomehaničke karakteristike gustih mikro i nanostrukturnih materijala na bazi HAP i HAP/β-TCP. Svojstva materijala dobijenih mikrotalasnim sinterovanjem, spark plazma sinterovanjem i toplim presovanjem upoređeni su sa svojstvima materijala dobijenih konvencionalnim sinterovanjem.Calcium phosphate bioceramics materials based on hydroxyapatite (HAP) and tricalcium phosphate (TCP), due to their chemical composition, excellent biocompatibility, bioactivity and osteoconduction have received considerable attention as suitable bioceramics for the manufacture of osseous implants. Dense nanostructured and controlled porous forms of hydroxyapatite and calcium phosphate are often used as reparation material in maxillofacial, dental and orthopedic surgery. Careful control of phase composition, grain size and shape and size of pores of sintered bioceramic materials in accordance with good mechanical properties can be key issue for a successful implant. A large number of studies were focused on determining the optimal conditions required to obtain dense or controlled porous HAP and HAP/TCP form suitable for incorporation in living bone. The aim of this PhD thesis was to investigate the processing of dense nanostructured pure hydroxyapatite and biphasic HAP/TCP bioceramics by microwave sintering, spark plasma sintering and hot pressing, starting from stoichiometric and calcium deficient nanosized HAP powders, obtained by two modified chemical precipitation syntheses. The effects of the processing conditions on the microstructure, phase composition and mechanical properties of the obtained materials based on HAP and TCP were investigated. The influence of microstructure and phase composition on the fracture toughness and hardness of sintered HAP and HAP/TCP bioceramics was also defined. The influence of the grain size and phase composition on the nanomechanical behaviour of dense nano and microstructured HAP and biphasic HAP/β-TCP bioceramic materials by nanoindentation was also investigated. The results obtained by microwave sintering, spark plasma sintering and hot pressing were compared with those obtained by conventional sintering methods..