【作者】 牟书香；

【导师】 武德珍；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2010， 博士

【摘要】 聚酰亚胺(PI)是一种具有优异的机械性能、电性能、耐辐射性能和耐热性能的高性能聚合物材料,广泛应用于航空航天、微电子和通讯等高技术领域。科学技术的发展对材料提出了更高更新的要求,材料的研究在不断地朝着高性能化、多功能化和低成本化方向发展。用无机纳米粒子尤其是金属或金属氧化物纳米粒子与聚酰亚胺材料进行复合,是目前实现聚酰亚胺材料功能化的一个重要方向,这种复合材料不仅结合了PI各方面的优异性能,同时引入了金属或金属氧化纳米粒子所特有的光、电、磁以及催化等功能特性,在航空航天和微电子等许多领域都具有潜在的应用价值,成为近年来聚酰亚胺材料研究的热点之一。本文采用成品PI材料为基体,利用聚酰亚胺材料不耐水解的特性,通过基于表面改性的一系列方法制备了各种聚酰亚胺/金属或金属氧化物功能复合材料,对复合材料的表面微观形貌,热性能、机械性能以及光电磁等特性进行了表征,考察了各种制备因素对复合材料微观结构与性能的影响,并探讨了相关的机理。以均苯四酸酐/4,4’-二氨基二苯醚(PMDA/ODA)基的PI薄膜为基体,以Co(NO3)2为钴源,采用表面改性、离子交换和在空气中热处理的方法制备了具有半导体性质和磁性的PI/四氧化三钴(Co3O4)复合薄膜。通过控制表面改性和离子交换的条件,可以在PI薄膜表面生成一层完全连续的Co3O4层,Co3O4粒子的大小为15-40nm,PI/Co3O4复合薄膜的室温表面电阻可降至107Ω。考察了钴离子的载入量对最终复合薄膜的微观结构与性能的影响,讨论了连续的Co3O4层形成的机理。PI/Co3O4复合薄膜保持了PI基体优异的力学性能和热性能,表面Co3O4复合层和聚酰亚胺基体之间具有良好的粘结性。以PMDA/ODA基的PI薄膜为基体,以Zn(NO3)2为ZnO的前驱体,通过表面改性、离子交换和在空气中热处理的方法制备了PI/ZnO复合薄膜。跟踪了热处理过程中ZnO纳米粒子的形成、生长过程和复合薄膜的光致发光性能,实验结果发现,相比较其它的金属氧化物纳米粒子,氧化锌的形成和生长过程较为缓慢,只有在350℃热处理7h以上,才能在复合薄膜的光致发光光谱上出现ZnO的紫外发射峰。同时研究了碱液处理和锌离子交换条件对锌离子掺杂量、最终复合薄膜的微观结构、光致发光和热性能的影响。所有在350℃热处理7h得到的PI/ZnO复合薄膜的光致发光光谱均呈现一个比较弱的紫外发射峰和一个宽而强的可见光发射峰。PI/ZnO复合薄膜保持了母体PI优异的热稳定性。通过表面刻蚀离子交换法制备了PI/NiO复合薄膜,由于在热处理过程中有可能发生了聚酰胺酸镍盐的分解和生成的NiO纳米粒子对周围PI的催化降解作用,薄膜表面出现大量微米级的树枝状裂缝缺陷。当在离子交换和热处理过程中引入尿素沉淀处理过程时,可制得表面无明显缺陷的PI/NiO复合薄膜。研究了碱液处理、尿素沉淀处理和热处理条件对复合薄膜微观形貌以及热性能的影响。薄膜的XPS表征证明经尿素处理后在薄膜表面生成了Ni(OH)2,热处理后生成了立方晶型的氧化镍粒子,NiO纳米粒子的大小约为10nM。PI/NiO复合薄膜在室温下呈现顺磁性。聚酰亚胺/NiO复合薄膜保持了母体PI薄膜优异的热稳定性。采用稀氨水溶液在室温下对含有镍离子的PI薄膜进行沉淀处理,热处理后同样可以制得表层NiO粒子均匀分散的PI复合薄膜。以PMDA-ODA基的PI薄膜为基体,以AgNO3为银源,通过碱液处理、离子交换和在抗坏血酸溶液中室温还原的方法制备了表面银化的PI复合薄膜。考察了薄膜两面的微观形貌、导电性和反射性随碱液处理条件和还原时间的变化。PI/Ag复合薄膜的表面电阻几乎都在1Ω/口以下,薄膜两面的反射率最高可达到92.97%和83.55%。以自制的PMDA-ODA纤维为基体,分别以硝酸银和银氨溶液为银源,用相同的方法制备了表面银化的PI导电纤维。研究了表面处理条件和银盐种类对纤维表面形成连续银层的影响。研究发现,控制合适的碱液处理和离子交换条件可在PI纤维表面形成完全连续的银层,纤维的表面电阻可降到102Ω/cm左右。以银氨溶液为银源时,PI薄膜的银化效率较高,在很低的银盐浓度(0.04M)和很短的离子交换时间(5min)下即可实现纤维的有效金属化。表面银化的复合薄膜和纤维基本上分别保持了母体PI薄膜和纤维优异的机械性能,且表面银层和PI基体之间具有良好的粘结力。更多还原

【Abstract】 Polyimide (PI) is an important high-performance polymer widely used in aerospace, microelectronics, communication fields and so on for their marked thermal-stability, excellent mechanical, electrical and radiation-resistance properties. With the development of science and technology, new requirements for the material such as high performance, multi-functional and low cost are raised. Combining inorganic nanoparticles especially metal or metal oxide nanoparticles with polyimide is an important approach to realize the functionalization of the polyimide materials. The prepared polyimide composite materials not only have the excellent performances of polyimide but also possess the unique optical, electrical, magnetic or catalytic functional properties of metal or metal oxide nanoparticles, and they have great potential applications in microelectronic, aerospace and other fields. In this thesis, based on the hydrolysis characteristics of polyimide matrix in alkali, various polyimide/metal or metal oxide functional composites were prepared via different surface modification methods utilizing polyimide films or fibers as matrix and inorganic metal salts as metal source. Factors influencing the surface morphology, thermal, mechanical and functional properties such as electric, magnetic and optical properties of the composites were studied and the related mechanisms were also investigated.Semiconductive PI/cobalt oxide (Co3O4) magnetic composite films were prepared by surface modification, ion exchange and thermal treatment in air atmosphere using commercial pyromellitic dianhydride/4,4’-oxydianiline (PMDA/ODA)-based polyimide films as the substrate and cobalt nitrate as the cobalt source. Continuous cobalt oxide layers could be obtained on the PI surface layer by controlling appropriate preparation conditions and the room temperature surface resistance of the composite film was in the range of 107Ω The particle size of cobalt oxide was in the range of 15-40 nm. The effect of cobalt ion loading on the morphology and properties of the composite films were investigated and the possible formation mechanism of continuous cobalt oxide layer was also proposed. The PI/Co3O4 composite films maintained the excellent thermal and mechanical properties of the bare polyimide film. The adhesion between surface cobalt oxide composite layer and the PI matrix was acceptable.PI/ZnO nanocomposite films were prepared by the surface modification and ion exchange technique using PMDA/ODA-based PI films as the substrates and zinc nitrate as the precursor of ZnO. The formation and growth process of ZnO nanoparticles and the photoluminescence (PL) properties of the composite films during thermal treatment were tracked. The results revealed that the formation and growth of ZnO nanoparticles were a slower process compared with other metal oxides and the ultraviolet emission band of ZnO would not appear on the PL spectrum of the composite film unless the thermal treatment time at 350℃is extended to 7 h. In addition, the effect of alkali treatment and ion exchange conditions were investigated in relating to the amount of zinc ion loading, surface morphology, photoluminescence and thermal property of the PI/ZnO composite films. The PL spectra of all the PI/ZnO nanocomposite films obtained at 350℃/7 h possessed a weak ultraviolet emission peak and a broad and strong visible emission band. The composite film kept the excellent thermal properties of the host PI film.PI/NiO composite films were prepared by the surface modification and ion exchange method. The formation and aggregation of NiO nanoparticles during thermal treatment may be accompanied by the decomposition of nickel polyamate and oxidative degradation of surrounding PI matrix catalyzed by newly generated NiO nanoparticles. Therefore, many large micron-wide cracks with dentritic shape occurred on the PI film surface. When the urea deposition process was introduced between ion exchange and thermal treatment, PI/NiO composite films without evident defects can be obtained. The effects of alkali treatment, urea treatment and thermal treatment conditions on the morphology and thermal properties of the composite films were investigated. XPS characterization demonstrated that nickel hydroxide particles were formed on the PI film surface after urea deposition process and converted to cubic nickel oxide nanoparticles with an average size of about 10-15 nm after thermal treatment in air atmosphere. The PI/NiO composite film presents ferromagnetic properties at room temperature. The composite films kept the excellent thermal stability of host polyimide film. When the deposition process of nickel ion-doped polyimide film was performed in dilute ammonia solution at room temperature, polyimide composite films with nickel NiO nanoparticles homogenously dispersed on both surface layers can also be obtained.Surface silvered PI films were prepared at room temperature by surface modification, ion exchange and reduction in ascorbic acid solution utilizing 1 PMDA/ODA-based PI films as the substrate and silver nitrate as the silver precursor. The morphology, conductivity and reflectivity of the both surfaces of the PI/Ag composite film were investigated in relating to alkali treatment time and reduction time. Film with maximum surface resistance of less than 1Ω/□and maximum reflectivity of 92.97% and 83.55% could be achieved. Surface silvered polyimide fibers were fabricated by the same method using polyimide fibers prepared in our laboratory as substrate and silver nitrate and silver ammonia complex cation as the silver source respectively. The effect of alkali treatment conditions and ion exchange conditions on fiber surface morphology, conductivity and mechanical properties were studied. Continuous silver layer can be formed on polyimide fiber surface and the surface resistances of the composite fibers could be reached to 102 Q/cm. Compared with silver nitrate, silver ammonia complex cation has higher efficiency for polyimide silver metallization which can be achieved by employing very dilute silver ion solution (0.04 M) and very short ion exchange time (5 min). The surface silvered polyimide films and fibers essentially maintained the mechanical properties of host polyimide films and fibers and the surface silver layers were well adhered to the polyimide substrates.更多还原