【作者】 文风；

【导师】 谢长生；

【作者基本信息】 华中科技大学 ， 材料科学与工程， 2007， 博士

【摘要】 宫内节育器(Intrauterine Device,IUD)是一种安全、有效、经济、可逆、简便的避孕工具,也是全球使用最广泛的方法之一。IUD分为惰性和活性两大类。惰性IUD由于其避孕效果差而已经被活性IUD完全取代。活性IUD主要有两种类型:载铜IUD(Cu-IUD)和药物缓释IUD。Cu-IUD中铜的避孕效果好,因而成为当今研究最多,使用最广的IUD。铜/聚乙烯复合材料就是一种新型载铜IUD材料,因其具有多种优点而成为目前IUD研究的热点,作为一种金属/聚合物复合材料,这种新型IUD材料在实际应用之前需要对其在人体中的腐蚀问题进行系统研究。目前关于金属/聚合物复合材料的腐蚀研究中,高电阻、分散型复合材料的腐蚀研究较少。文章通过测试复合材料的体积电阻率和介电常数,发现微米铜/聚乙烯复合材料存在一个的电阻率突然降低区域,其渗流阈值大概为50wt. %铜含量。在渗流阈值前后,微米复合材料体积电阻率不随铜含量的变化而变化。纳米复合材料电阻率没有明显的突变区域,其体积电阻率随着纳米铜含量的增加而逐渐减小。两种复合材料的介电常数都是随着铜含量的增加而上升,但是微米复合材料的介电常数在渗流阈值附近有一个阶跃。对于不同铜含量的微米铜/聚乙烯复合材料,其浸泡于模拟宫腔液中的腐蚀行为与铜含量密切相关。在腐蚀稳定期,高铜含量微米复合材料的腐蚀速率大大高于低含量复合材料。当复合材料中微米铜的含量超过渗流阈值时,复合材料逐渐出现较明显的钝化现象,表面会出现大量成片状沉积物。纳米复合材料在浸泡初期的腐蚀速率变化较大,在浸泡5天后,腐蚀速率迅速趋于稳定。与纯铜电极相比,复合材料电极在模拟宫腔液中的腐蚀速率更加稳定,暴释现象和钝化现象都不如前者明显。经过一段时间浸泡后,纯铜电极表面会覆盖大量沉积物,复合材料尤其是纳米复合材料表面更为清洁。纯铜电极和两种复合材料在模拟宫腔液中都具有相似的腐蚀机理,都是分两步氧化反应,且中间产物都以Cu2O为主。对于微米复合材料,铜含量对其腐蚀机理有着一定的影响。当微米铜含量低于渗流阈值时,复合材料在腐蚀过程中只有一步还原反应,而当微米铜含量高于渗流阈值时,复合材料腐蚀过程有两步还原反应。纳米复合材料的铜含量对腐蚀机理没有影响。复合材料的铜离子转化率远远高于纯铜,而且纳米复合材料的转化率接近于100%。铜含量对微米复合材料的转化率影响较大,尤其是当铜含量超过渗流阈值时,铜离子转化率明显降低。而铜含量对纳米复合材料的转化率影响不显著。在浸泡初期,纯铜电极和微米复合材料电极的铜离子转化率都有一个明显的上升过程,纳米复合材料在浸泡过程中始终保持很高的铜离子转化率。复合材料的重量和电容都是随着浸泡时间的延长呈现上升的趋势,而且最终都趋于稳定饱和。浸泡初期,溶液在复合材料内部的扩散都符合Fick第二定律。铜离子在纯铜电极表面层的扩散系数远远高于其在复合材料内部的扩散系数。铜离子在复合材料内部的扩散系数的数量级在10-9cm2s-1左右。腐蚀稳定后,铜离子主要通过贯通复合材料内部的溶液路径向外扩散。电极在模拟宫腔液中的腐蚀过程都可以用相同的等效电路图进行解释,并且在模拟宫腔液中的腐蚀过程受到电荷传递过程和扩散过程共同控制。与纯铜相比,复合材料(尤其是纳米复合材料)具有铜离子转化率高、表面清洁等优点,更有利于作为一种新型IUD材料。另外,研究表明,电化学技术作为一种常用的腐蚀研究方法,在高电阻、分散型金属/聚合物复合材料的腐蚀行为研究中也是一个非常有力的工具。更多还原

【Abstract】 Being safe, effective, economic, reversible and simple, intrauterine device （IUD） is one of the most popular contraceptive methods that are used all around the world. IUD can be divided into two categories, namely, the inert and the active one. Owing to its weak effect of contraceptive, the inert IUD has been replaced gradually with the active one. The active IUD covers copper-containing IUD （Cu-IUD） and drug slow-release IUD. Recently, Cu-IUD has been widely investigated and employed due to great contraceptive effect of copper.The copper/low-density polyethylene （Cu/LDPE） composite is one kind of new IUD, because it has the many kinds of merits to become the hot spot of the present IUD research. To optimize the properties of these composite systems, it is necessary to study their corrosion behaviour in the uterine solution thoroughly. Currently on the corrosion research of the metal/polymer composite, high resistivity and dispersing type composite are less.By testing the volume resistivity and the dielectric constant of the composite, the resistivity of the microcomposite have of a sudden decreased region and the percolation threshold of the microcomposite probably is 50% copper quality percentage. Around the percolation threshold, the volume resistivity of the microcomposite does not change along with the copper content change. There are not obvious mutation region for the volume resistivity of the nanocomposite, its volume resistivity gradually reduces along with the copper content increase. The dielectric constant of two composites all are rise along with the copper content increase. The dielectric constant of the microcomposite has a leap in the vicinity of the percolation threshold.The corrosion behaviour of the microcomposite immersion in the simulated uterine solution is depended on the copper content. Corrosion in stable, the corrosion rate of the microcomposite with high copper content much high than the microcomposite with low copper content. The surface of the microcomposite appears obvious passivation phenomenon and schistose sediment when the copper content of the microcomposite was exceeding the percolation threshold. The corrosion rate of the nanocomposite was fluctuations in early immersion. Compared with bulk copper, the composite have more stable the corrosion rate, less burst release of Cu²⁺ and hardly passivation. Immersion after period time, the surface of the bulk copper is covered the massive sediment. Corresponding, the surface of the composite, especially the nanocomposite, is cleaner.The bulk copper and two kinds composite have similar corrosion mechanism in the course of corrosion in the simulated uterine solution, all is some two steps of oxidizing reaction. The intermediate products of them are mainly Cu2O. For the microcomposite, the copper content have some effect to its corrosion mechanism. When the copper content is lower than the percolation threshold, the microcomposite only has a step of reduction reaction; but when the copper content is higher than the percolation threshold, the microcomposite has two steps of reduction reaction. The copper content has not affected to the corrosion mechanism of the nanocomposite immersion in the simulated uterine solution.The copper transformation ratio of two composites is higher than the bulk copper, and the transformation ratio of the nanocomposite is close to 100%. The copper content has greater impact to the transformation ratio of the microcomposite, especially the transformation ratio reduces obviously while the copper contents exceed the percolation threshold. And the copper content is not significantly affected to the transformation ratio of the nanocomposite. Is soaking the initial period, the transformation ratio of the bulk and the microcomposite all has an obvious rise process. The nanocomposite throughout to maintain the very high the transformation ratio when immersion in the simulated uterine solution.The weight and capacitance of the composite all are along with the immersion time of the rising trend, and all tends to stable finally. Be immersed initial stage, the diffusion characteristics of the solution in the composite according to the FickⅡ. The diffusion coefficient of Cu²⁺ in the surface layer of the bulk is far high than the composite, and the diffusion coefficient of Cu²⁺ in the composite about 10-9cm2s-1. When corrosion of the composite reaches stable, Cu²⁺ generated within composite disperses through solution path to penetrate to simulated uterine solution outside the composite. The corrosion behaviour of the bulk and the composite all can be explained by the similar electrical equivalent circuits, and it was controlled by both the processes of the pervasion of Cu²⁺ and the transfer of the charge.Compared with the bulk copper, the Cu/LDPE composite have high copper transformation ratio, clean surface, single product and hardly passivation quality when immersion in the simulated uterine solution. We can conclude that the Cu/LDPE composite, especially the nanocomposite, is favorable to as the novel material of IUD. Further, the electrochemical method in this study is proved to be useful to characterize the corrosion behaviour of high resistivity and dispersing type metal/polymer composite.更多还原