Revealing the linear relationship between electrical, thermal, mechanical and structural properties of carbon nanocoils

Abstract

The special helical morphologies and polycrystalline–amorphous internal structures differ carbon nanocoils (CNCs) from carbon nanotubes or carbon nanofibers, but bring difficulties in illuminating the correlations between physical and structural properties. In this paper, we measure the electrical conductivity (σ), thermal diffusivity (α) and Young's modulus (E) of single CNCs at the same time, using a transient electrothermal technique and an electromechanical vibration technique. Based on the statistical results of 8 single CNC samples, a linear correlation between the three parameters is uncovered, expressed as σ = 0.052(α − 2.5) × 10⁴ S m⁻¹, E = (−10.38σ + 14.04) GPa and E = (−0.59α + 16.08) GPa, where the unit of α is 10⁻⁷ m² s⁻¹. Concise proportional relations between the three parameters and average graphite grain size (l_d) are deduced, expressed as σ = Al_d(C₁ − T)⁻¹, α = Bl_d(C₂ + T)⁻¹ and E = −Dl_d + E₀. The proportional relation between physical parameters and l_d demonstrates the confinement originated from the nano-grain system.