| Calcium phosphate cement is a new type of self-setting cement. It is perfect material for bone substitution and repair, which shows excellent biocompatibility, osconductibility, biodegradability, plasticity and less reaction thermal. But in the studies before, the problems of low strength and mechanics were not solved. It is used to non-bearing bone and hard tissue repair because of its brittleness. To solve the problem many research were carried out. The first was solid powder, including the arrangement in-group for different calcium phosphate and the additive. Second several kinds of liquid, including citric acid, malic acid and phosphate natrium, were used. Another crystal whisker, organic material, chopped fiber were used to strengthen the material. We could see the higher strength, especially treated in the third method. But the whole effect was not good.It is of significance to search new thought and strengthening material in order to increase the mechanics for its application and competition.Following the structure of cortex bone, we replaced the collagen fiber by carbon continuous fiber and obtained the calcium phosphate strengthened by fibers, which was a class of biomaterial with better performance because of high strength and toughness of carbon fibers. Carbon nanotubes possess unique properties such as its small measure, high strength, the grate modulus of elasticity and specific surface area, and mechanics. It is believed to be an ideal toughening material and can obtain an composite with better mechanics. We use the two materials and prepare the calcium phosphate composite strengthened by CF/CNTs. We designed CF/CPC, CNTs/CPC, CF/CNTs/CPC composite, and investigated the preparation procedure, microcosmic structure, mechanics and strengthening effect. This study includes as follows:At first, we compared the different solid powder, a-tricalcium phosphate, tetracalcium phosphate, new type of α_H-tricalcium phosphate and β - tricalcium phosphate included, and test their microcosmic structures and mechanics, and then choose the α-tricalcium phosphate as the matrix. We optimized the preparation procedure of a-tricalcium phosphate by experiments of sintering parameters. Theproduction had high purity and stable performance. During the process of tetracalcium phosphate, two-step sintering was used and the purity was improved. We prepared aH-tricalcium phosphate by means of additive and analyzed the effect of the additive and the forming process of the production. During the comparing experiments of liquid we got the bone cement of 3 - tricalcium phosphate that P - tricalcium phosphate appeared adhesive bone cement slurry after adding the citric acid. We did a little work on CNTs/ 3 - tricalcium composite and found the CNT cluster with a shape of basket from the SEM graph of fracture surface.Secondly, the preparation procedure, microcosmic structures, mechanics and the strengthening effect of CF/CPC composite were investigated. The CF was oxidized in order to increase the combining strength of interface. We investigated CF surface after treated by IR and SEM and determined the best treatment procedure, that is, the CF was oxidized at 90°C for 2h by nitric acid. The composite contained 0.6% CF, its rupture strength was 10.14MPa increased by 53.1%, and its compressive strength was 20.81 MPa, increased by 6.66%, the porosity was 43.03%. CF was surrounded by the matrix and even formed crystal with the shape of lotus leaf affected by the Van der waals and hydrogen bond. As a result, the affinity between CF and the solid and the combination of the interface were improved. The debonding, pulling out and the fracture of fibers made composite mechanics improved. We calculated the strength in the theory of the composite strengthened by successive carbon fiber and found the composite could be improved ulteriorly.Thirdly, We researched the preparation procedure, microcosmic structures, mechanics and the effect of strengthening of CNTs/CPC, CF/CNTs/CPC and built the crystal growth model of the HA on CNT to set forth the existence form in the bone cement. In the study we found the "Hadley grain" in the bone cement for the first time. CNTs and the powder were milled at 300r/min for 4h, and then observed by SEM and TEM. The optimum percent of CNTs in the composite was 0.6%, whose rupture strength was 10.48MPa increased by 58.3%, compressive strength was 31.22MPa increased by 60.02%, and the porosity was 42.12%. The affection by adsorption of CNTs pore was analyzed. We set forth the procedure of the strengthening byanalyzing the surface and the properties of CNTs, and explained the existence the physical adsorption and chemical bond. As a result the combination was intense .The mechanics of composite was improved because of the fracture of the HA/CNT composite body and the turnaround of the crack. The calculated value of CNTs strengthening effect was greater than the experimental value, which showed the CNT has potential in strengthening materials. We prepared the CF/CNTs/CPC with the optimum percent of CF and CNTs, whose rupture strength and compressive strength were 40.5 IMPa and 15.78MPa, increased by 107.6% and 138.37% respectively. We can see that the cooperation of the two materials was better. We observed the microcosmic structures of the cements and the composite and found the "Hadley grain", 1 u m in wall, empty or with unreacted bone cement grains. The existence of the pores could affect the strength of the cements.The fourth, biocompatibility experiments of in vitro and in vivo were made to the bone cement material. The blood compatibility experiment in vitro indicated that good chemical property of the composite, physical and chemical microcosmic multiphase structure in 0.1-0.2 u m formed by hydrated matrix caused it wholly appeared no affinity with platelets, and possessed the property of anti-cruor. When we planted the material in the gluteus of white rat, it was found from histological observation that no large area of infection and putrescence of circumambient tissues was caused in the striated muscle, only normal inflammation. The composite showed no toxicity, and had good biocompatibility. After the New Zealand big white rabbit's skull plantation, it was indicated by the bone conductibility experiment that 12 weeks after the composite was planted, blood vessels and bone tissues of surrounding organisms grew well towards the composite, the relate data of the composite obtained from CT already were in the scale of the normal bone structure, PWI and tissues observation had the same result. These evidences indicated that the composite had good osconductibility, which could provide the good support for new bone growth, and then it would be the potential material for bone tissue engineering.The study reported the CF/CPC strengthened by the long carbon fibers following the structure of the bone, CNTs/CPC strengthened by the carbon nanotubes withexcellent properties and CF/CNTs/CPC strengthened by the carbon fibers and the carbon nanotubes for the first time, and then researched the preparation procedure, microcosmic structures, mechanics and the effect of strengthening. It can be used to repair the defection of bone and substitute for the unbearing bone because of its high rupture strength.Besides the above three kinds of new composite improved the bone cement mechanical properties, we had several innovations and discovery. Firstly, we prepared the new type of ciH-tricalcium phosphate, analyzed its procedure and tested the mechanics and the microcosmic structures of the cements. Secondly, we found the novel existence form of CNTs in the composite that HA grew on CNT and formed HA/CNT by the physical adsorption and chemical bond. Thirdly, we found the "Hadley grain" by observed the microcosmic structures of the matrix after hydration, and pointed out the existence of the pores could affect the strength of the cements. Above reports could enrich the investigation and application of bone cement. So far, we have declared the national patent and explored along with several medical corporation.
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