Preparation And Properties Of Bioactive Glass Research

The system of Na₂O-CaO-P₂O₅-SiO₂ bioactive glass powder and blocks were prepared using traditional high-temperature melting method and the bioactive glass coatings on titanium alloy were fabricate using laser cladding in this paper. The microstructure, physics and chemical properties, bioactivity of bioactive glass and laser cladding coating were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and Fourier transform infrared spectroscopy (FTIR).The results show that bioactive glass display amorphous state, and the internal structure of it mainly contains three different modes of Si-0 vibration groups, such as Si-O(s) stretching vibration, Si-O(r) rocking vibration and Si-O(b) bending vibration. It is also observed that the chemical composition is acceptable for silicon, calcium and phosphorus while the loss of sodium is observed obviously. The reason can be explained by that sodium is thought to be the most volatile element. From the test of immersing in alkaline sodium hydroxide, we find that bioactive glass show more surface corrosion pits and significant corrosion grooves and cracks. And during the immersion corrosion process, it demonstrates that the corrosion rate gradually reduces, and after 50 days immersion, the mass of bioactive glass move toward stability.The significant changes have happened on the glass surface while immersed in simulated body fluid for different time. It indicates that glass surface generates silica sol-gel layer and Ca-P layer in turn during immersion. And in the top of external Ca-P layer, there exists numerous spherical granules, which have the similar atomic Ca/P ratio to that of hydroxyapatie. The Ca-P rich layer is identified as hydroxyapatite and carbonate hydroxyapatite by XRD. In addition, the researches of surface reactions on bioactive glass show that SiO₂-gel layer is produced after a serial effects of ion exchange, condensation and repolymerization, and gel layer possessing the open structure accelerates the nucleation of apathies by reducing the critical nucleus radius (r^*) and the activation energy barrier against heterogeneous nucleation(△G^*). Then under the effect of Zeta potential, the Ca, P ions in simulated body fluid are accumulated on the surface of SiO₂-gel layer. Once apatite nuclei occur on the surface of gel layer, it can grow up spontaneously because of the supersaturated apatite positive ions (IP) of SBF.In this experiment, laser cladding coating shows good quality and reveals the distinct characteristics of the ceramic. XRD spectra show that most diffraction peaks coincide seriously and close to weak, except a few peaks, it shows partly dispersion pheromone. For single bioactive glass cladding coating, it mainly consists of CaTiO₃ phase and A1P, Al₂O₃, Ti₇Al₅Si₁₂, Ti₂O₃. While mixed cladding coating consists of more Ti₂O₃ beside CaTiO₃, for the addition of titanium powder in coating. After been laser cladding, the coating form compact combine between each other and show fine metallurgical combination. The microstructure of cladding coating changes from dendrite to columnar dendrite to equiaxed crystal at the effect of temperature and composition gradient.