Objective. To fabricate and characterise a novel biomimetic interpenetrating phase ceramic/polymer composite material consisting of aligned honeycomb-like porous ceramic preforms infiltrated with polymer for potential orthodontic bracket material applications.
Method. Unidirectional freeze-casting with a temperature gradient was used to fabricate and control the microstructure and porosity of alumina ceramic preforms, which were subsequently infiltrated with 40 to 80% by volume UDMA-TEGDMA and PC polymers. The composite materials had a gradient structure with a more dense bottom part (ceramic-rich) while the top part was more porous (ceramic-poor). These composite materials were then subjected to characterisation, namely ceramic volume fraction, density, compression, three-point bend, fracture toughness, hardness, surface roughness, abrasivity testing and surface loss. Samples were also subjected to scanning electron microscopy and micro computerised tomography (MicroCT).
Results. Three-dimensional aligned honeycomb-like ceramic structures were produced and full interpenetration of the polymer phase was observed using MicroCT. Depending on the volume fraction of the ceramic preform, the ceramic volume fraction of the final interpenetrating composites ranged from 18.83 to 61.17%, density ranged from 1.73 to 3.36 g/cm3, compressive strength ranged from 26.31 to 253.97 MPa, flexural strength from 28.28 to 145.65 MPa, fracture toughness from 3.91 to 4.86 MPa.m½, hardness ranged from 1.46 to 1.62 GPa, surface roughness following toothbrushing from 0.99 to 1.43 µm and surface loss from 0.56 to 1.40 µm.
Significance. Freeze-casting provides a novel method to engineer composite materials with a unique aligned honeycomb-like interpenetrating structure, consisting of two continuous phases, inorganic and organic. There was a correlation between the ceramic fraction and the subsequent, density, strength, fracture toughness, hardness and abrasivity of the composite materials. These composite structures could be potentially used as a composite bracket material to compete with the current aesthetic orthodontic brackets.
|Date of Award||7 May 2019|
|Supervisor||Anthony J Ireland (Supervisor) & Bo Su (Supervisor)|