木质纳米纤维素/石墨烯电热膜电热效应的调控及其构效机理

Graphene electrothermal film was of high electric heating response rate and could meet these requirements such as melting snow and ice on aerospace device, materials thermal analysis and defrosting and demisting, but still existing some questions such as poor flexibility, low controllability, uniformity and stability in electrical heating effect, which was restricted with popularization and application. This project would use wooden nanofibrillated cellulose (NFC) as skeleton to prepare a kind of new-type electrothermal film by composite with graphene. The electrothermal film possessed excellent flexibility, thermal stability and adjustable-uniform-stable electrothermal effect, which benefited from facile couplet of NFC self and good insertion and dispersion between NFC and graphene. It was focused on that how modulation parameters impacted resistance, electrical-heating property and mechanical strength, heat/pressure effect was analyzed and electrothermal effect regulation law was established. Through characterization of building way of NFC-graphene network, temperature distribution model was built to make quantitative characterization of distribution uniformity of the network system, revealing regulatory mechanism. Through systematical analysis of electrothermal characteristics and its evolution law and characterization of combining ways of NFC-graphene, microstructure of the network system, change of phase structure and chemical properties in electrothermal process, structure-activity mechanism of electrical heating effect evolution would be revealed and mechanism for NFC improving toughness and electrothermal effect would be clarified, provide theoretical reference for improving working performance and precision, attaching NFC and graphene higher use value.

石墨烯电热膜具有较高的电热响应速率，在航空航天器件融雪除冰、材料热分析及除霜除雾等领域有重要需求。但存在柔韧性不足，电热效应的可控性不高及均匀稳定性欠佳等问题，制约其推广应用。本项目采用天然木质纳米纤丝纤维素（NFC）为骨架基体与石墨烯复合创制新型电热膜，利用NFC自交联成膜及其与石墨烯相互嵌插增固和互促均匀分散的作用，协同增强其柔韧性、热稳定性及电热效应可控、均匀稳定性；研究调制参数对电阻、电热性能及机械强度的影响，结合热/力阻效应分析，建立电热效应调控规律，通过阐明NFC-石墨烯结合程度的演变，构建温度分布模型量化表征网络体系分布均匀性，揭示调控机制；系统分析电热特性及其演变规律，表征电热作用过程NFC-石墨烯结合方式、微观形貌、物相结构及化学性质的变化，解析电热效应演变的构效机理，阐明NFC改善韧性和电热效应的机制，为改进工作性能和精度提供理论参考，推进纳米纤维素和石墨烯高值化利用。

为改善石墨烯电热膜存在的柔韧性不足及电热效应的可控性和均匀稳定性欠佳等问题，本项目采用纳米纤丝纤维素（NFC）组装石墨烯优化制备了一种柔性均匀的新型电热膜，探讨了超声分散参数、石墨烯含量、克重（厚度）对电热膜结构性质、导电性能、电热性能的影响规律，分析了热/力-阻效应、电热特性及热辐射性能，研究了电热耦合作用下的构效关系等。研究表明通过优化超声分散参数，发挥超声波空穴效应引起的剪切作用，结合一维NFC作为分散体及其相互间的静电斥力，能分散石墨烯片层形成均匀稳定的体系，并使NFC嵌插于片层之间组装成柔性均匀的电热膜。NFC自身及其与石墨烯之间通过界面结合力组装成稳固的叠层结构，赋予电热膜良好的力学性能和柔韧性，反复弯折过程表面温度均匀性未见显著变化。电热膜两电极间电阻具有规律的热敏性和力敏性。电热膜电阻与石墨烯含量和克重均呈指数函数递减关系，通电时温升先指数函数曲线上升而后趋于稳定；一定功率密度下随着石墨烯含量或克重的增加，平衡温升呈增大趋势；随着功率密度增加，平衡温升线性升高，电阻下降率增大，实际加载功率高于设定功率；随着循环通断电次数增多，电阻先下降后趋于稳定，电热性能呈规律性和可控性。电-热辐射转换效率高于50%，法向全发射率高于0.85、相对辐射能谱主要分布于3-25μm范围内，具有良好的电热辐射特性。电热效应主要发生于石墨烯片层之间的搭接点，该接触点的分布影响表面温度均匀性，据此通过红外热成像和图像处理可直观评价石墨烯的分散性。电热膜电阻在通电时迅速下降，之后趋于平稳，断电冷却后大多数存在一定的电阻下降率，这归咎于其中界面电阻的降低以及表面含氧基团的减少，但其结构未见明显变化；电阻随着温升增大而减小，而后几乎同时趋向稳定，两者存在相关性。研究成果将为该类生物质基电热膜的应用提供直接理论支撑，且可为分析导电单元在基体中的分散性和复合材料的热/力敏特性提供借鉴。