Electrical and Mechanical Properties ofC70Fullerene and Graphite under High Pressures Studied Using Designer Diamond Anvils

Abstract

We compare electrical and mechanical properties of C70 fullerene with high purity graphite to 48 GPa at room temperature using designer diamond anvils with embedded electrical microprobes. The electrical resistance of C70 shows a minimum at 20 GPa with transformation to an amorphous insulating phase complete above 35 GPa, while graphite remains conducting. Nanoindentation shows hardness values 220 times larger for the pressure quenched amorphous phase than for similarly treated graphite. Our studies establish that the amorphous carbon phase produced from C70 has unique properties not attainable from graphite.

Formation ofsp3Bonding in Nanoindented Carbon Nanotubes and Graphite

“…This result is consistent with experimental observations [10,11]. It should be noted that the 100 GPa strength of the graphite and the diamond is obtained under a nonuniform compressive condition where shear stress may play important role.…”

“…In the last decade, many high-pressure experiments have revealed the fascinating phase transformation of fullerenes into superhard polymeric and disordered-amorphous carbon phases. The hardness sometimes can approach that of single-crystal diamond [3][4][5][6][7][8], even at room temperature [9,10]. On the other hand, in graphite subjected to high pressure up to 65 GPa at room temperature, no superhardness is found after the pressure is removed [10,11].…”

“…The hardness sometimes can approach that of single-crystal diamond [3][4][5][6][7][8], even at room temperature [9,10]. On the other hand, in graphite subjected to high pressure up to 65 GPa at room temperature, no superhardness is found after the pressure is removed [10,11]. Recently, a new phase hard enough to crack diamond anvils is obtained from graphite undergoing a transition of sp 2 to sp 3 bonding at a pressure of about 17 GPa [12].…”

Superhard sp2–sp3 hybrid carbon allotropes with tunable electronic properties

“…Another little understood carbon allotrope is a transparent superhard carbon polymorph. It is observable under a high pressure range of 10-25 GPa, [15][16][17][18][19][20][21] but only quenchable at low temperatures (<100 K) and at ambient pressure. 15 This post-graphite phase has been extensively explored to identify candidate crystal structures, including sp 2 -sp 3 hybrid (3,0)/(4,0), 22 and sp 3 -hybridized M-carbon, bct-C 4 , F-carbon, X-carbon, Y-carbon, W-carbon, Z-carbon, and P-carbon.…”

Accurate measurement of sample conductivity in a diamond anvil cell with axis symmetrical electrodes and finite difference calculation

“…[1][2][3][4][5][6] But in a long time, the accurate conductivity measurements were ever hard to be taken on diamond anvil cell (DAC) due to the difficulties from sample configuration and the rigorous geometrical limitations coming from small sample and electrodes. [5][6][7][8][9][10][11][12] For solving the problem, the techniques of thin film electrodes integration and electric field analysis (EFA) were combined together in conductivity measurement by four-probe method (FPM) in DAC and the accuracy has been achieved. [13][14][15][16] These studies indicated that only if the size and the thickness of sample chamber and the geometry configuration of electrodes were carefully designed, could the conductivity be obtained by FPM configuration and EFA methods.…”