Structure and properties of superelastic hard carbon phase created in fullerene-metal composites by high temperature-high pressure treatment

Abstract

Treatment of a fullerene soot extract and metal (Co) powder mixture under pressure of 5 and 8 GPa at 1000 °C leads to the transformation of fullerites into superelastic hard phase (SHP) and to simultaneous sintering of the powder mixture to nonporous composite material reinforced by the SHP particles. The structure of the SHP particles reveals a topological relation to the initial fullerite crystal morphology. Upon indentation, the SHP particles demonstrate an elastic recovery of up to 96%. The universal microhardness of the SHP particles HU = 26 GPa, and their microhardness HV = 35 GPa. A high ratio between the microhardness and elastic modulus (HV/E = 0.19-0.21) of the SHP particles makes them perspective candidates for design of materials with superior wear resistance and tribological properties.

Structure and physical properties of nanoclustered graphene synthesized from C60 fullerene under high pressure and high temperature

“…factor of two. 11 With increasing synthesis pressure, the hardness H OP and Young modulus E of the NGP samples calculated by the Oliver-Pharr method 10 somewhat increase whereas the elastic recovery slightly decreases (Table II).…”

Raman and electron microscopy study of C60collapse/transformation to a nanoclustered graphene-based disordered carbon phase at high pressure/temperature

“…Raman spectrum of the “gray” particle (Fig. c) is, on the contrary, typical of a well‐developed NGP thus indicating completeness of C 60 collapse/transformation to graphene. Importantly, we observed several carbon particles which displayed an “intermediate” behavior, i.e., the scratch width change across their surface that is likely an indicative of a more complicated phase composition of these particles.…”

“…Extended studies of C 60 fullerite behavior at high pressure and high temperature (HPHT) led to synthesis of various phases – one‐ (1D), two‐ (2D), and three‐dimensional (3D) polymers, respectively, and sp 2 –sp 3 carbon‐based phases with different degree of disorder mapped on transformation p‐T diagrams . Under certain p,T conditions C 60 cages collapse and the resulting sp 2 –sp 3 carbon phase (NGP) exhibits combination of remarkable mechanical properties – high hardness , high‐elastic recovery , and low friction . First, Tatyanin et al and recently Lepoittevin et al have speculated about possibility of a pseudo‐martensitic mechanism of this structural transformation although no experimental evidence in favor of this assumption was provided to date.…”

Measurement of the hardness of superelastic carbon

“…Измерение твердости индентирования и модуля индентирования по методу У. Оливера и Дж. Фарра [3] и было использовано для оценки твердости продуктов превращения фуллеритов под давлением [4][5][6][7]. Действующий стандарт ISO 14577 [8] предусматривает также измерение твердости по Мартенсу с учетом полной деформации при максимальной нагрузке на индентор.…”