Novel, oxidation-stable, carbon-based multifibrillar fibers with exceptional mechanical properties via electrospinning

碳纤维和陶瓷纤维的机械性能主要由缺陷决定。与聚合物和金属纤维不同，脆性材料的缺陷会导致灾难性的失效。因此，理论上可能的强度值甚至不能近似达到。这是一个机会，一方面可以改善纤维的生产，避免缺陷，另一方面可以减少纤维直径。然后每个纤维长度的缺陷频率减少。当这些纳米纤维理想地彼此平行排列，并通过持续热解组合成束时，预期会有所改善。拜罗伊特大学（University of Bayreuth）的大分子化学II教授已经开发出这样一种方法，可以用静电纺丝改性PAN生产超高强度的多纤聚合物纳米纤维。由于聚丙烯腈是最常用于生产碳纤维的前驱体，因此第一个研究重点是通过静电纺丝、固化和连续碳化来生产由许多纳米原纤维制成的低缺陷碳纤维。碳纤维的缺点是在400°C时就已经开始氧化。因此，合成碳纤维的研究成果应用于实现主要项目目标：生产高强度和显著抗氧化的多纤纤维。这些研究是基于拜罗伊特大学陶瓷材料工程主席之前的工作，PAN与硅氮烷相结合。同样由静电纺丝生产的多纤碳/ SiCN纤维，经过固化和连续热解后，应该由碳和钝化的Si3N4组成，并且应该具有很高的强度值和足够的氧化稳定性。这种连续生产的纤维类型无论是碳纤维还是陶瓷纤维都是未知的。它们代表了新一代，据说超过了商用碳和SiC纤维的机械性能。拜罗伊特大学的两位研究主席提供了合成和改性相应聚合物的必要专业知识，并通过静电纺丝、固化和热解将其加工成多纤纤维，并在相应的出版物中进行了记录。这些互补的知识应该汇集在一起，并结合在拟议的项目中。最后，对多功能碳纤维在增强塑料和陶瓷方面的潜力进行了研究和评价，因为碳纤维在纺织技术方面易于加工。

The mechanical properties of carbon and ceramic fibres are determined primarily by defects. Unlike polymer and metal fibres, a defect in brittle materials leads to catastrophic failure. Therefore, the theoretically possible strength values are not even approximately reachable. An opportunity presents itself on one side to improve fibre production with regard to defect avoidance, and on the other side to decrease the fibre diameter. Then the defect frequency per fibre length diminishes. Improvement is expected when such nanofibres are aligned ideally parallel to one another and combined into bundles with continual pyrolysis. At the Chair for Macromolecular Chemistry II at the University of Bayreuth such a procedure has been developed to produce extremely high-strength, multifibrillar polymer nanofibres from electrospinning modified PAN. Since PAN is the precursor most often used to produce carbon fibres, the first research focus is the production of low-defect carbon fibres made of many nanofibrils via electrospinning, curing and, lastly, continual carbonisation. The disadvantage of carbon fibres is the beginning of oxidation already at 400 °C. Therefore, the findings from the synthesized carbon fibres should be used to achieve the main project goal: the production of a high-strength and significantly oxidation-resistant multifibrillar fibre. These investigations are based on previous works from the Chair of Ceramic Materials Engineering at the University of Bayreuth, where PAN was combined with silazanes. The multifibrillar carbon / SiCN fibers, again produced by electrospinning, should consist of carbon and passivating Si3N4 after curing and continual pyrolysis, and should have very high strength values and be sufficiently stable to oxidation. Such continuously produced fiber types are unknown for either carbon or ceramic fibers. They represent a new generation and are said to exceed the mechanical properties of commercial carbon and SiC fibers. The necessary expertise in synthesis and modification of corresponding polymers, their processing into multifibrillar fibers via electrospinning, curing and pyrolysis are available at the two research chairs involved at the University of Bayreuth and are documented in the corresponding publications. This complementary knowledge should be brought together and combined in the proposed project. Finally, the potential of the multifunctional carbon fibers, which are easy to process in terms of textile technology, for the reinforcement of plastics and that of carbon / SiCN fibers for ceramics reinforcement, are to be examined and evaluated.