Conditions for forming composite carbon nanotube-diamond like carbon material that retain the good properties of both materials

Abstract

Gold nanoparticle formation in diamond-like carbon using two different methods: Gold ion implantation and codeposition of gold and carbon J. Appl. Phys. 112, 074312 (2012) Carbon nanotubes are of wide interest due to their excellent properties such as tensile strength and electrical and thermal conductivity, but are not, when placed alone on a substrate, well resistant to mechanical wear. Diamond-like carbon (DLC), on the other hand, is widely used in applications due to its very good wear resistance. Combining the two materials could provide a very durable pure carbon nanomaterial enabling to benefit from the best properties of both carbon allotropes. However, the synthesis of high-quality diamond-like carbon uses energetic plasmas, which can damage the nanotubes. From previous works it is neither clear whether the quality of the tubes remains good after DLC deposition, nor whether the DLC above the tubes retains the high sp 3 bonding fraction. In this work, we use experiments and classical molecular dynamics simulations to study the mechanisms of DLC formation on various carbon nanotube compositions. The results show that high-sp 3 -content DLC can be formed provided the deposition conditions allow for sidewards pressure to form from a substrate close beneath the tubes. Under optimal DLC formation energies of around 40-70 eV, the top two nanotube atom layers are fully destroyed by the plasma deposition, but layers below this can retain their structural integrity. V C 2015 AIP Publishing LLC.

Swift heavy ion effects on DLC-nanotube-diamond thin films

“…Meanwhile, the number of 5-and 7-membered rings notably decreased, while 9-and 10-membered rings somewhat increased in the center region of the track. As we saw in Ref [22], a structure with higher sp 3 fraction has a higher fraction of 6-membered rings. Thus, the ring analysis further supports the conclusion that the track formed by a SHI is prone to graphitization, as extra free volume is created during thermal expansion after the impact.…”

“…The two different temperatures were used to obtain the different sp 3 content of the substrate. As we showed earlier [22], the lower ambient temperature creates a higher sp 3 hybridization fraction of growing DLC films. For each bombardment within the time scale of 15 ps, Berendsen temperature scaling [23] was used to dissipate heat from the impact region to the rest of the system, by which the lateral periodic boundaries within a thickness of 7Å were immersed in a heat bath.…”

“…2 for both temperatures. In this figure, it is clearly seen that the DLC film grown at 100 K exhibits the higher content of sp 3 hybridization before the SHI impact, compared to the film grown at 300 K [22]. After SHI impact at ambient temperatures of 300 K and 100 K, respectively, the embedded MWCNTs were completely destroyed in the impact region.…”

“…The negative values of depth show the grown DLC film, and the positive values show the diamond substrate with the interface at 0Å. Before the SHI (as we have studied in Ref [22]), the atoms with sp 3 hybridization were barely observed at the depths between -25 and 0Å, where the curvature of the MWCNT did not allow for four-fold bonding. However, beyond this range, the sp 3 hybridizations increased gradually to more stable values, up to ∼ 35% in the cells grown at 300 K and ∼ 65% in the cells grown at 100 K. After 700 ps, the values of the sp 3 content over the depth did not change, only slightly shifted toward the diamond substrate.…”

“…The DLC-CNT-diamond thin films were prepared by plasma deposition in our previous work [22], where successive low energetic carbon atoms were irradiated on a diamond substrate. A box size of about 41 × 36 × 12 A 3 was used as the diamond {111} substrate with about 6 atomic layers.…”