Lin Kunpeng, Fang Hailiang, Gao Ang, Yu Hui, Wang Lianjun, Yu Qian, Gu Lin, Zhang Qinghua, Li Jianlin, Jiang Wan
School of Materials Science and Engineering, Hainan University, Haikou, 570228, China.
State Key Laboratory for Modification of Chemical Fibres and Polymer Materials, School of Materials Science and Engineering, Donghua University, Shanghai, 201620, China.
Adv Mater. 2021 Apr;33(17):e2007513. doi: 10.1002/adma.202007513. Epub 2021 Mar 18.
A critical challenge for the application of graphite is low strength, which originates from the easy cleavage of graphite (0002) planes. Inspired by the burl strengthening mechanism observed in tree trunks, nanodiamond particles converted into graphite onions are used as "nanoburls" embedded in graphite (0002) lattice planes to eliminate the graphite (0002) plane cleavage of bulk graphites prepared by spark plasma sintering from graphite powders. Covalent bonds are built between carbon atoms by sp hybridization at the interface between the graphite onions and flakes, which triggers an electron redistribution to form positive/negative charge domains within. Thus, pairs of pseudo-Schottky junctions are created by the hybridization, which further enhances the bonding between the graphite onions and flakes. With these bonding mechanisms, and with voids between the graphite powders filled in by the volume expansion associated with the change of nanodiamonds to the graphite onions, the loose compaction of graphite powder becomes consolidated at 1700 °C. The proposed nanoburl mechanism shows its potential and bestows the nanoburl graphites with strength five times that of conventional graphites prepared from graphite powders. The concept of nanoburl strengthening can be important in the microstructural design and property enhancement of other layered materials.
石墨应用面临的一个关键挑战是强度低，这源于石墨（0002）平面易于解理。受树干中瘤状物强化机制的启发，转化为石墨洋葱的纳米金刚石颗粒被用作嵌入石墨（0002）晶格平面的“纳米瘤”，以消除通过火花等离子烧结由石墨粉末制备的块状石墨的石墨（0002）平面解理。在石墨洋葱与薄片之间的界面处，通过sp杂化在碳原子之间建立共价键，这引发电子重新分布，从而在内部形成正/负电荷域。因此，通过杂化形成了成对的伪肖特基结，进一步增强了石墨洋葱与薄片之间的结合。通过这些结合机制，以及纳米金刚石转变为石墨洋葱所伴随的体积膨胀填充了石墨粉末之间的空隙，石墨粉末的松散压实状态在1700℃时得以巩固。所提出的纳米瘤机制显示出其潜力，并赋予纳米瘤石墨的强度是由石墨粉末制备的传统石墨的五倍。纳米瘤强化概念在其他层状材料的微观结构设计和性能增强方面可能具有重要意义。
