Material properties and structure of natural graphite sheet

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Natural graphite sheet (NGS) is a compressible, porous material with excellent electrical and thermal conductivity.
• NGS has potential applications in fuel cells, batteries, electronics cooling, supercapacitors, adsorption air conditioning, and heat exchangers.

Purpose of the Study:

• To conduct an extensive material characterization of NGS.
• To investigate the density and compression dependency of NGS properties.
• To establish relationships between NGS structure and its properties.

Main Methods:

• Material characterization of thermal conductivity, thermal diffusivity, electrical conductivity, coefficient of thermal expansion (CTE), compression strain, and emissivity.
• Microscopy for structural analysis.
• Analysis of density and compression effects on properties.

Main Results:

• All measured properties (thermal conductivity, electrical conductivity, CTE, etc.) are density-dependent and anisotropic.
• Increasing compression from 100 to 1080 kPa enhances through-plane thermal and electrical conductivities by up to 116% and 263%, respectively.
• In-plane properties follow the Wiedemann-Franz law; through-plane CTE is high and increases with density.

Conclusions:

• NGS properties are significantly influenced by compression and density.
• Negligible contact resistance in stacked NGS at relevant pressures.
• NGS exhibits unique anisotropic thermal expansion behavior, with negative in-plane CTE and high, density-dependent through-plane CTE.