| The research on hard tissue replacement is one of the most attractive aspects of biomedical engineering. Mechanical property of the replacement materials are emphasized since these materials are usually used in load-bearing situation. Hydroxyapatite (HA) ceramic is a kind of bioactive material with excellent biocompatibility and osteoconductivity, but the brittleness and high modulus of HA limit its clinic application. To meet the need of hard tissue repair, many researches have been carried out through combining bioactivity of HA and toughness of polymers. However, in clinical application these composites have a low strength, modulus and poor long-term effectiveness due to low HA content, poor interfacial bonding or relatively fast dissolution or resorption rates of polymers. Therefore, the development of a biocomposite with high bioactivity, good mechanical property and long-term effectiveness will effectively improve the performance of implants.In this dissertation, the research on biomimetic composites with high bioactivity, expecting long-term effectiveness and bone-matching mechanical properties is carried out. Preparation progress of nanograde needle-like hydroxyapatite crystals (n-HA) are prepared by hydrothermal treatment under 140℃, 0.3MPa pressure and normal atmospheric pressure. n-HA/polyamides (n-HA/PA66 and n-HA/PAll) composites are made and their properties are tested by TEM, SEM, XRD, FT-IR, AFM, ICP, XPS and Laser Raman spectroscopy. The composite with porous structure isalso prepared. Human serum is used in in vitro experiment to study the changes of composite surface.1. In this research, n-HA crystals were prepared at 145-165℃ under normal atmospheric pressure and at 140℃ under 0.3MPa pressure. The effect on crystal formation was investigated and discussed.Ammonium phosphate ((NH4)3PO4) and calcium nitrate (Ca(NO3)2) were employed, and organic solvent agent (N,N-Dimethylacetamide, DMAc) was used to replace aqueous phase in n-HA preparation process. The mean size of n-HA crystal is about 18.1 X97.2nm and its aspect radio can reach to 5.4 and over. Besides temperature and concentration of reaction, the heating rate plays an important role on the size and morphology of n-HA crystals. The aspect radio of n-HA crystals prepared at a higher heating rate and at a temperature of boiling point can reach 7.0. Higher heating rate affects the growth speed of HA crystals, breaking HA crystal growth balance and causes a smaller size of n-HA. The reaction temperature at boiling point can accelerate the evaporation of solvent, improve concentration of reaction and promote HA crystallization. n-HA prepared at 145℃ and under 0.3MPa has a rod-like shape with aspect radio around 3.1. The n-HA crystals obtained both under normal atmospheric pressure and 0.3MPa have the Ca/P molar radio between 1.60 to 1.62 and contain chemical groups such as PO43-, CO32-, HPO42- and OH", similar to that of bone apatite. Moreover, these n-HA crystals have poor crystallinity, which is also similar to that of natural bone apatite. The aspect ratio of n-HA crystals prepared under normal atmospheric pressure is higher than that obtained under 0.3MPa, suggesting that the former has a higher biomimetic property.2. n-HA crystals prepared under normal atmospheric pressure was mixed with PA66 and PAH in solution to obtain n-HA/PA biocomposites with different n-HA contents (30wt%, 40wt%, 50wt%, 55wt%, 60wt%, 65wt%). As a comparison, micrometer-grade HA (μ-HA) was also used to prepare520-650cm-1, 660-770cm-1, 3454cm-1, 3482cm-1. The Raman characteristic peaks at 961.64cm-1 (PO43-) and 3571.7cm-1 (-OH) moved, suggesting the existence of hydrogen bonds between hydroxyl, phosphorous group of n-HA and polar group of polyamide. The formation of PA wrap around n-HA crystals is one of the causes of Raman-peak variation. The O1s fitting analyses of XPS spectra also support the appearance of hydrogen bonds between two phases of the biocomposite. The variation of Ca2p then shows the possible interaction betwe...
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