Study On Preparation Process And Application Of Calcium Silicate-based Materials

Calcium silicate?Ca Si O₃?is known for its various excellent properties and is widely used in different materials such as thermal insulation,adsorption,construction,oil well engineering and other technological fields.In addition to industrial applications,calcium silicate has also been exploited in biomedical engineering like repair of hard tissue materials due to its good biocompatibility,degradability,and bone conductivity.The ideal bone repair material needs to meet the requirements of its degradation rate to match the rate of new bone formation,mechanical properties close to natural bone,and controllable porosity.However,the limitation of calcium silicate biomaterials is its poor mechanical properties and fast degradation rate.In recent years,some related studies have reported that doping with alkaline earth metal ions such as sodium ions improves the performance of biological materials.Sodium containing bio-glass and bio-ceramics have been commercialized and successfully used in clinics.Based on the above background,cheap natural limestone?Ca CO₃?,water glass?containing 26.5%Si O₂,8.3%Na₂O?were used as raw materials to prepare calcium sodium silicate precursor by chemical precipitation method.The reactions were carried out in the muffle furnace by mixing the sintered powder with an appropriate amount of polyvinyl alcohol?PVA?to make a ceramic green body.The static pressure was attained before keeping the samples in a muffle furnace and calcined at high temperature to obtain sodium calcium silicate ceramic.The effect of Na⁺concentration during preparation,sintering temperature and holding time during sintering on the crystal phase,powder particle size,powder morphology and ceramic properties of the powder were studied.In-vitro biological activity test was performed on the prepared ceramic samples.The samples were characterized by using thermal-thermogravimetric analysis?TG-DSC?,X-ray diffraction?XRD?and scanning electron microscope?SEM?in order to determine sintering temperature,crystal type and microstructure respectively.Further the absorption properties,degradability and biological activity was checked by immersing the ceramic piece in deionized water,Tris-HCl and simulated body fluid?SBF?.The results show that different added amount of Na₂O have a greater impact on the crystal phase and morphology of the sodium silicate powder.When added Na₂O to calcium silicate,the resulting ceramic is polycrystalline,including Na₂Ca₂Si₃O₉,Na₄Ca₄Si₆O₁₈,Na₂Ca Si₃O₈.The particles are spherical in shape having average diameter of 0.5?m with uniform dispersion.The particle size can be controlled and the particle size distribution follows the normal distribution.Different calcination temperature and holding time affect the crystallinity of the powder and the mechanical properties of the ceramic.The powder has the highest crystallinity at 1100?for 8hours and the ceramic has the best mechanical properties.Its compressive strength reaches 151 MPa,similar to human bone compressive strength.The in-vitro activity of calcium sodium silicate ceramic tablets was determined after soaking them in deionized water for 48 hours.The results show that the water absorption rate has been enhanced up to 24.1%which indicates that sodium calcium silicate ceramics have fast and efficient water absorption performance.The degradability was detected after soaking them in Tris-HCl solution for 84 days where weight loss rate of the ceramic sheet reached 38.8 wt%,indicating that the sodium calcium silicate ceramic is an excellent biodegradable biomaterial and it can induce the formation of hydroxyapatite after soaking in SBF for 3 days.Hence,sodium calcium silicate ceramic has promising biological activity and can be used as a potential bone repair material.