Magnetic functionalization of brushite microplatelets and rheological analysis of slurries

Natural ceramics such as bone and teeth possess complex microstructures comprising inorganic minerals oriented in various directions, allowing them to perform biological and mechanical functions. Among the various processes developed to mimic natural microstructural arrangement, magnetically assisted slip casting (MASC), a process that locally orients magnetically functionalized ceramic microplatelets suspended in a slurry while the solvent is slowly sucked out, is deemed promising. However, MASC has not yet been applied to bioceramic materials due to the lack of recipes for functionalized bioceramic microplatelets and for slurries. This study therefore explores the magnetic functionalization of synthesized brushite microplatelets with various sizes and their magnetic response. After coating with superparamagnetic iron oxide nanoparticles, brushite microplatelets synthesized at 2 and 22°C exhibited a diameter of 10 μm and an alignment time of less than 12 s. Aqueous slurries with 12 vol% brushite were prepared, and their rheological properties and stabilities were measured. It was found that all slurries exhibited a solid-like nature and low stability, which may be exacerbated by the presence of iron oxide at the surface of brushite. Further approaches to slurry preparation are discussed to guide future development of calcium phosphate-based slurries in view of future microstructured bioceramics and biocomposites produced using MASC.