Preparation of bioactive sodium titanate ceramics

摘要

The in vitro bioactivity of sol-gel derived sodium titanates with different sodium contents was investigated. Calcined sodium titanates show bioactive behaviour when exposed to simulated body fluid (SBF). A higher sodium content entails higher bioactivity since a higher amount of sodium ions is available for the exchange with H_3O~+ ions from SBF, which results in the formation of Ti-OH groups and subsequently in the formation of an intermediate calcium titanate. The local pH increase triggers the formation of a biomimetic calcium phosphate layer on the surface. Sintering the samples leads to more crystalline sodium tri- and hexatitanate structures and a decrease of the sodium content. The amount of Na~+ ions that can be released from the sodium titanate surface decreases due to a decreasing surface area and the reduced sodium content. As a result bioactivity is lost. Bioactive behaviour can be re-achieved by a subsequent chemical treatment of sintered sodium titanate ceramics in an aqueous NaOH solution.