Radial distribution function of a new form of amorphous diamond shock induced from C60 fullerene

Mechanical characterization of reinforced vertically-aligned carbon nanotube array synthesized by shock-induced partial phase transition: insight from molecular dynamics simulations

Despite intriguing mechanical properties of carbon nanotubes (CNTs), vertically-aligned carbon nanotube (VACNT) array does not possess a high strength against compression along the CNT axis and also the loadings perpendicular to the CNT axis. Here in this study, shock compression is introduced as a means for partial phase transition (PPT) in the VACNT array to reinforce the structure against the mentioned loadings. Molecular dynamics simulations are exploited to investigate the synthesis of a novel nanostructure from a VACNT array with 10 nm long (5, 5) CNTs. Employing Hugoniostat method, shockwave pressures of 6.6 GPa and 55 GPa are extracted from Hugoniot curves as the instability limit and the PPT point, respectively. Coordination analysis reveals the nucleation of carbon atoms in sp³hybridization while preserving the dominant nature of CNT due to the high percent of sp²hybridization. Recovery of the shocked samples yields the final structure to be tested for mechanical characteristics. Tensile and compression tests on the samples reveal that for the shockwave pressures below the PPT point, an increase of the shock strength leads to higher compliance in the VACNT array. However, beyond the PPT point the novel nanostructure shows an extraordinary strong behavior against loading along all directions.

Tailoring Building Blocks and Their Boundary Interaction for the Creation of New, Potentially Superhard, Carbon Materials

A strategy for preparing hybrid carbon structures with amorphous carbon clusters as hard building blocks by compressing a series of predesigned two-component fullerides is presented. In such constructed structures the building blocks and their boundaries can be tuned by changing the starting components, providing a way for the creation of new hard/superhard materials with desirable properties.

Pathway for the transformation from highly oriented pyrolytic graphite into amorphous diamond

We report the discovery of a novel pathway for the transformation from highly oriented pyrolytic graphite foils into amorphous diamond platelets. This pathway consists of three stages of neutron irradiation, shock compression, and rapid quenching. We obtained transparent platelets which show photoluminescence but no diamond Raman peak, similar to the case of amorphous diamond synthesized from C60 fullerene. Wigner defects formed by irradiation are considered to make a high density of diamond nucleation sites under shock compression, of which growth is suppressed by rapid quenching.

Novel crystalline carbon-cage structure synthesized from laser-driven shock wave loading of graphite

We report a novel crystalline carbon-cage structure synthesized from laser-driven shock wave loading of a graphite-copper mixture to about 14+/-2 GPa and 1000 +/- 200 K. Quite unexpectedly, it can be structurally related to an extremely compressed three-dimensional C60 polymer with random displacement of C atoms around average positions equivalent to those of distorted C60 cages. Thus, the present carbon-cage structure represents a structural crossing point between graphite interlayer bridging and C60 polymerization as the two ways of forming diamond from two-dimensional and molecular carbon.

Understanding of the phase transformation from fullerite to amorphous carbon at the microscopic level

We study the shock-induced phase transformation from fullerite to a dense amorphous carbon phase by tight-binding molecular dynamics. For increasing hydrostatic pressures P, the C60 cages are found to polymerize at P<10 GPa, to break at P approximately 40 GPa, and to slowly collapse further at P>40 GPa. By contrast, in the presence of additional shear stresses, the cages are destroyed at much lower pressures (P<30 GPa). We explain this fact in terms of a continuum model, the snap-through instability of a spherical shell. Surprisingly, the relaxed high-density structures display no intermediate-range order.