Unreinforced and carbon fibre reinforced hydroxyapatite: resistance against microabrasion

Hot pressing (1000–1150 °C, 25 MPa, 15 min, argon atmosphere) was used to process unreinforced and carbon short fibre reinforced hydroxyapatite (20% fibre volume fraction). Due to the selected processing parameters, a fine grained crystalline calcium hydroxyapatite matrix without any decomposition products and a close contact between the slightly curved surface of the carbon fibres and the hydroxyapatite was realized. The nano- and microstructure of the hydroxyapatite and the composites is characterized by Fourier transformed infrared spectroscopy, Raman spectroscopy, X-ray diffraction and high resolution transmission electron microscopy. Ball-crater wear tests were performed with abrasive SiC particles to assess the sensitivity against microabrasion. The reinforcement of calcium hydroxyapatite with carbon short fibres enhances the resistance against microabrasion. An additional 60 nm thick pyrolytic carbon coating on the fibres further improves the wear resistance due to prevention of the crack formation, which can be induced by thermal expansion mismatch between reinforcement and matrix.