BACKGROUND: Carbon nanotubes (CNTs) is about 1 mm in diameter and about 1-10 μm in length cylinder-like material, and it only contains the spiral of carbon atoms arranged on the surface. Because of its unique tubular structure, lower density than that of graphite and with a high enough intensity, CNTs are expected to substitute bone.OBJECTIVE: To primarily study the influence of the content of polycarbosilane (PCS) and the sintering pressure on CNTs, look for the most optimum condition for the preparation of chunk CNTs, analyze the physical properties and biocompatibility of the material, and provide a choice for candidate implant denture material.DESIGN: The content of cement and the sintering pressure are adjusted in the experiment to make sure the most optimum condition for the preparation, and the capabilities of the material are observed and analyzed to make sure if that the material is suitable for implant denture.SETTING: Department of Stomatology, Xiangya Hospital, Central South University; Prosthodontics Staff Room, Oral Medical College of Central South University. MATERIALS: 80% pure molecules of CNT (Nano Lab Company USA), 20-40 nm in diameter, 5-20 mm in length, was provided by Nacheng Technology Development Corporation of Beijing. PCS was compounded by 502 Development Room of Defense Technology University, and the molecular weight is 1 300; Ten male white Wistar rats with 8 weeks old were provided by Animal Experiment Center of Guangxi Medical University. The treatments with the animals accorded to animal ethical standard in the experiment.METHODS: The experiment was carried out in the Experimental Center of Material College, Central South University from January to August 2005. By using the spark plasma sintering (SPS), at the sintering temperature of 1 200 ℃, the pressure from 20 MPa to 60 MPa, PCS was used as the cement to produce the new chunk multi-wall CNTs.MAIN OUTCOME MEASURES: By using Archimedes method and adsorption of gases method, Japanese MitutoyoHM-101 little burden Vickers hardness meter was used to test the apparent bulk density, specific surface area, Vickers hardness at the different contents of PCS and sintering pressures. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to observe the microstructure of the material.RESULTS: ① Microstructure: SEM and TEM indicated that the nanotube structure of the material was retained after sintered. ② Conforming phase of material: X-ray diffractometer indicated that carbon nanotubes were felt by PCS pyrolysis product of SiC; along with the PCS content and sintering pressure increased, the specific surface area was reduced, and Vickers hardness and density increased. Specific surface area decreased. ③ Histological compatibility: The inflammatory reactions of the CNTs/PCS were little more serious along with the increase of the content of PCS. The physical property of carbon nanotubes was prepared in this way, it was closed to bone tissues, it had the better biocompatibility, and it was the suitable candidate implant denture material.CONCLUSION: Appropriate to PCS for the bonding agent, through SPS, at 1 200 ℃, 20-60 MPa sintering pressure, CNTs/PCS which the material property is closed to bone tissues can be prepared, and CNTs/PCS subcutaneous implantation in rats does not show significant rejection; therefore, it is suitable candidate for dental implants material.%背景:碳纳米管是一种直径约1 nm,长1～10 μm的圆筒状物质,具有比石墨还小的密度;加上足够高的强度,碳纳米管有望用于骨替代材料.目的:初步考察聚碳硅烷含量和烧结压力对碳纳米管材料性能的影响,寻求大块碳纳米管材料的最适制备条件,并分析所制备的碳纳米管材料的物理性能和生物相容性,为临床候选牙用种植体材料提供选择依据.设计:实验通过调整结合剂的含量和烧结压力,确定材料的最适制备条件,并观察分析材料的性能,探讨材料是否合适选作口腔种植体材料.单位:中南大学湘雅医院口腔科和中南大学口腔医学院口腔修复教研室.材料:实验所用纯度为 80%的大块多壁碳纳米管为美国Nano Lab Company产品, 直径 20～40 nm,长5～20 mm.由北京纳辰科技发展有限责任公司提供;聚碳硅烷,由国防科技大学502教研室合成,相对分子质量为1 300.实验中用于评估材料组织相容性的10只8周龄的雄性Wistar大鼠由广西医科大学实验动物中心提供;实验过程中对动物的处置符合动物伦理学标准.方法:实验于2005-01/08在中南大学材料学院实验中心完成.运用放电等离子烧结方法,在烧结温度为1 200 ℃,压力从20 MPa至60 MPa的条件下,以聚碳硅烷为结合剂,制备出一种新型的大块多壁碳纳米管.主要观察指标:用阿基米德方法、气体吸附方法、显微维氏硬度测量仪分别测试不同聚碳硅烷含量和烧结压力下的松装密度、比表面积、维氏硬度.扫描电镜和透射电镜观察碳纳米管/聚碳硅烷材料的显微结构,X线衍射仪和拉曼光谱仪测定材料的组成相.苏木精-伊红染色后光镜下观察实验材料植入大鼠皮下组织后的组织相容性.结果:①显微结构:烧结后材料的纳米级结构仍被保留. ②材料的组成相:纳米管通过聚碳硅烷热解的SiC纳米结晶相互粘结;随着聚碳硅烷量及烧结压力增加,材料的密度和维氏硬度增加,比表面积减少.物理性能接近于骨组织.③组织相容性:碳纳米管/聚碳硅烷材料的炎性反应随着聚碳硅烷含量增加有轻度增加.未发现碳纳米管/聚碳硅烷材料周围有坏死等严重炎性反应.结论:以聚碳硅烷为结合剂,通过SPS方法,在1 200 ℃高温,20～ 60 MPa烧结压力下,可以制得材料特性近似于骨组织的碳纳米管/聚碳硅烷,并且植入鼠皮下组织后,未见明显排异现象,是适宜的候选牙用种植体材料.
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