| Owing to excellent biocompatibility and bioactivity, calcium phosphate has been widely used as bone substitute, scaffold for drug delivery and matrix for bone tissue engineering. When used as bone substitute, CaP implants are able to form the chemical bonding between implants and biological bone. It has been discovered recently that porous β-TCP/HA biphasic ceramic with proper phase composition and porous structure are not only osteoconductie, but also osteoinductive, so it has attracted great attentions of biologists and clinicians. The mechanism of CaP bioactivity is widely accepted as: the Ca2+ and PO43- dissolve from CaP implant under influence of body fluid, subsequently deposit as bone-like apatite layer on the surface of the CaP implant. However, a problem of bioceramics preparation is that sintering in conventional furnace couldn't improve the mechanical properties and bioactivities simultaneously. An important idea to optimized designing of material itself and innovating the preparation technique by microwave sintering and carbonate containing of CaP ceramic was brought forward. It may give CaP ceramics high mechanical performance and high activity simultaneously and is of great importance for bone substitute materials preparing. So in this paper, carbonate contained β -TCP/HA biphasic powder was synthesized by a modified neutralization method, and porous body with proper porosity and porous structure was prepared by addingpore-forming agents. The sintering property of porous materials under conventional furnace and microwave system has been discussed respectively. The material factors on the solubility in brine and bone-like apatite formation in SBF bas been researched also.On the basis of thermodynamic analysis of Ca(OH)2- H3PO4 system, Ca(OH)2, CaCO3, H3PO4 were firstly used as starting materials to prepare carbonate-containing biphasic ceramic powder by a modified neutralization method. The reaction mechanism was proposed based on the analysis. The reaction temperature, the pH value, the addition manipulation and the addition rate of the reactant were different from routine conditions. It has been demonstrated by XRD, SEM and FT-IR that the product sintered by precursor participated from the solid-liquid system was pure β -TCP/HA powder and without other phases. The average grain size of powder was 100~200nm. The carbonate substitution model in this product was Type-B, that means CO32- substituted PO43-.It will make the composition of powder approach to natural bone, and may improve the bioactivity of porous CaP ceramics.To prepare porous body of carbonate contained β-TCP/HA biphasic ceramic, stearic acid ball and PVB powder was added as pore-forming agents and porous material with good macropore and micropore structure was obtained. When sintered in a conventional furnace, the sintering temperature and sintering curve was optimized to acquire proper phase composition, microstructure and better mechanical properties.Microwave sintering may solve the conflict of mechanical properties and bioactivities of bioceramics. At present there was no report about microwave sintering of porous biphasic ceramics and carbonate contained CaP ceramics. In this paper, porous β-TCP/HA biphasic ceramic was firstly sintered in a self-developed microwave sintering system and self-designed insulator, and it provides a new approach to the application of microwave sintering technology on bioactivity ceramics. The porous ceramic with good porosity and pore structure has been sintered successively. Compared with conventional furnace sintering, the sintering temperature of microwave sintering has been decreased by 100 centigrade, and theholding time was only 20% of conventional method. The average grain size was 300-400nm, finer than the conventional sintered specimens of 1 μ m. Fine grain size may improve the mechanical properties and bioactivities of bioceramics.From an application point of view the success of biphasic ceramic as bone substitute lies in the combination of a higher solubility of β-TCP and the superior... |
PDF Full Text Request