Microstructure Dictating Performance: Assembly of Graphene-Based Macroscopic Structures
Microstructure Dictating Performance: Assembly of Graphene-Based Macroscopic Structures
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DOI：
10.1021/accountsmr.0c00053
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发表时间：
2021-01-22
影响因子：
14.6
通讯作者：
Lian, Jie
中科院分区：
文献类型：
--
作者：
Li, Mingxin;Lian, Jie
在过去的几十年里，由于单层石墨烯的有利特性，包括其破纪录的导热性、载流子迁移率、断裂强度和杨氏模量，在电子、光子学、纳米复合材料等领域取得了广泛的突破性进展。然而，实现宏观石墨烯组件的潜力仍然具有挑战性。难点主要在于控制石墨烯片的有序分子间取向和控制石墨畴的宏观有序。控制石墨烯宏观结构的形成，消除纳米和微观尺度上的缺陷，同时优化性能并非易事。为了解决宏观石墨烯组件中的这些微观结构问题，已经开发了多种化学，热学和机械方法，目标是提高整体性能。因此，在这篇文章中，我们简要回顾了我们在宏观尺度石墨烯组件的微观结构工程方面的贡献，重点是石墨烯纤维（GFs）、石墨烯纸（GPs）和其他以氧化石墨烯胶体为前体的石墨烯基组件。基于湿化学在将单个氧化石墨烯片组装成宏观结构方面的发展，我们成功地将大氧化石墨烯片与小氧化石墨烯片嵌入，这增加了湿法纺丝石墨烯的致密性，同时又不影响大氧化石墨烯片的取向和排列。在湿式装配过程中，增加氧化石墨烯的致密性，可以增加导热性和导电性，以及单冲程GFs的机械强度。石墨烯片与丰富的sp(2)碳原子的高度排列对于实现石墨烯组件的高导热性和导电性也是必要的。通过流体流动通道的形状和尺寸限制，证明了湿纺丝装配过程中氧化石墨烯片的对准和取向的精细控制。利用这种剪切应力诱导的自对准策略，解决了GFs的核-壳非均匀性问题。此外，还建立了湿纺丝过程中氧化石墨烯的流变特性和流动模式与GF组件微观结构之间的相关性。除了石墨烯片的取向外，石墨烯组件内的晶粒尺寸和宏观有序度也对其性能起着重要作用。更大的和高度定向的石墨晶体域允许更高的导热性和导电性。通过高温石墨化来控制晶域的大小和排列，可以显著提高GFs的电导率、导热系数和杨氏模量。精细的温度控制还可以帮助保留相邻石墨烯片之间的剩余共价交联，满足平衡拉伸强度、导热性和导电性的需要。通过优化石墨烯片的密实度和排列方式以及石墨烯晶域的取向来增强GF的机械、热学和电学性能，显著提高了GF的工程性能。这种改进在很大程度上有利于柔性电子的研究，并在多功能复合材料中显示出巨大的潜力。类似的策略也被模拟在相关的石墨烯基材料上，如石墨烯纸（GPs）和石墨烯纤维网（GFMs），产生独特而有利的性能和性能。
A wide range of groundbreaking advancements in electronics, photonics, nanocomposites, etc., have been achieved in the past decades due to the favorable attributes of single-layer graphene, including its record-breaking thermal conductivity, charge carrier mobility, fracture strength, and Young's modulus. However, the realization of the potentials of macroscale graphene assemblies has remained challenging. The difficulties mainly lie within manipulating graphene sheets into an orderly intermolecular orientation and controlling the macroscopic ordering of the graphitic domains. Controlling the formation of graphene macroscopic structures and eliminating defects on both the nano- and microscales meanwhile optimizing performance is no easy feat. To address these microstructural issues in macroscopic graphene assemblies, multiple chemical, thermal, and mechanical approaches have been developed with a goal of overall performance enhancement. Therefore, in this Account we provide a brief review of our contributions in the microstructure engineering of macroscale graphene assemblies with the focus on graphene fibers (GFs), graphene papers (GPs), and other graphene-based assemblies with graphene oxide (GO) colloids as precursors.Building upon the developments in wet chemistry on assembling individual GO sheets into macroscopic structures, we successfully intercalated large GO sheets with small GO sheets, which increased compactness for wet-spun GFs without disturbing the sheet orientation and alignment of the large GO sheets. Increasing GO compactness during wet assembly allows for the increase of thermal and electrical conductivities as well as the mechanical strength of GFs at a single stroke. A high degree of alignment of graphene sheets with abundant sp(2) carbon atoms is also necessary for achieving high thermal and electrical conductivities in graphene assemblies. Fine control of GO sheet alignment and orientation during the wet-spinning assembly is demonstrated through the shape and size confinement of fluidic flow channels. Utilizing this shear-stress-induced self-alignment strategy, the core-shell nonuniformity problem of GFs is addressed. Also, a correlation between the rheological properties and flow patterns of GO during wet-spinning and the microstructure of the GF assemblies is established.In addition to the orientation of graphene sheets, the crystallite size and macroscopic ordering within graphene assemblies also play important roles in determining their performances. Larger and highly oriented graphitic crystalline domains allow for higher thermal and electrical conductivities. By manipulating crystallite domain size and arrangement through high temperature graphitization, the electrical and thermal conductivities and Young's modulus of GFs can be significantly enhanced. Fine temperature control can also help retain residual covalent cross-links between neighboring graphene sheets, meeting the need for balancing tensile strength, and thermal and electrical conductivities.The enhancement of GF mechanical, thermal, and electrical properties through optimizing the compactness and alignment of graphene sheets and the orientation of graphene crystallite domains have significantly improved the engineering capability of GFs. Such an improvement has been largely beneficial to flexible electronics research and has shown great potential in multifunctional composite materials. Similar strategies have also been emulated on related graphene-based materials such as graphene papers (GPs) and graphene fiber meshes (GFMs), yielding unique and favorable properties and performances.