Study On The Fabrication And Properties Of Carbon Nanotubes Reinforced Mesoporouse Hydroxyapatite Nano Composites

As an important bone mineral component,hydroxyapatite?HA?has similar crystal structure and chemical composition to human bone,and good biocompatibility,biological activity and bone conductivity.Therefore,HA is considered as an ideal bone tissue replacement material.However,pure HA has poor mechanical properties and the lower strength and toughness,which restrict its application in weight-bearing bone replacement.Carbon nanotubes?CNTs?have been regarded as one of the ideal reinforcements for composites due to their excellent mechanical,electrical and thermal properties.Thus,the research on the preparation of CNTs/HA composites has been carried out using the strengthening and toughening effect of CNTs.However,there are still some deficiencies in the currently prepared CNTs/HA composites.For example,the CNT-HA interface is weak,and the mechanical properties of the composites are low;The exposed CNTs cause toxicity problems;The specific surface area and wettability are low,which are not conducive to cell adhesion,proliferation and the mineralization of bone formation.Consequently,it is of great significance to further explore the preparation technology and property of CNTs/HA composites.This thesis presents a research idea of CNTs reinforced mesoporous HA composites.Adopting the CNTs/HA composite powders in situ synthesized by chemical vapor deposition method as raw material and cetyl trimethyl ammonium bromide?CTAB?as template,mesoporous HA encapsulated CNTs composite powders?CNT@meso-HA?were fabricated by using chemical homogeneous precipitation method.The effects of process conditions on the synthesis of CNT@meso-HA were investigated.The formation mechanism of mesoporous HA was analyzed.And the microstructure,mechanical properties and biological properties of CNTs/HA composites prepared by powder metallurgy were discussed.In the study of synthesising CNT@meso-HA,firstly,the CNTs/HA in situ composite powers were chemically modified by H₂O₂/H₃PO₄ combined with ultrasonic technology,and the hydroxyl and carboxyl functional groups were successfully grafted onto the surface of CNTs.Then,the CNT@meso-HA was prepared by chemical homogeneous precipitation method,and the optimum process conditions were as follows:35°C aging for 72h.The specific surface area of the composite powder was 131.7m²/g.Increasing aging temperature and aging time,the thickness of mesoporous HA deposition layer was gradually increased,and the CNTs were encapsulated by mesoporous HA closely.The in vitro cytotoxicity test of CNT@meso-HA showed that CNTs/HA in situ composite powders had cytotoxicity and CNT@meso-HA had no cytotoxicity.The performance test of CNTs reinforced mesoporous HA composite showed that the composite had the highest flexural strength?79MPa?and fracture toughness(2.37MPa·m^1/2)with the CNT content of 3wt.%,which were improved by 52%and 216%compared to the pure HA,respectively.The main strengthening mechanisms of the composites were the pulling out and bridging of CNTs.Compared with the contrast samples,the cell morphology on the CNTs enhanced mesoporous HA composites was the best,CNT@meso-HA composites promoted cell adhesion,proliferation and had better osteogenic mineralization properties.