Nanoburl Graphites

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(3) 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 degrees 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.

Automated summary

The study introduces a nanoburl mechanism to enhance the strength of graphite by embedding nanodiamond particles converted into graphite onions in the graphite lattice planes. By building covalent bonds and forming positive/negative charge domains at the interface between graphite onions and flakes, the bonding between them is strengthened, leading to a consolidation of loose compaction of graphite powder. The proposed mechanism has shown its potential by increasing the strength of graphite five times compared to conventional methods, and may have implications for enhancing the properties of other layered materials.