Graphene fiber thermal conductivity study released by ACS Material

Graphene fibers leverage the exceptional in-plane thermal conductivity of individual graphene sheets into a macroscopic, weavable form. These fibers, produced by wet-spinning graphene oxide and undergoing thermal treatment, see their axial thermal conductivity increase from tens to approximately 1290 W m⁻¹K⁻¹ after high-temperature graphitization. This enhancement is due to improved sheet alignment and defect healing. The process involves various factors such as processing state, alignment quality, and junction density, which are not fully captured in datasheets.

Individual graphene sheets exhibit remarkable in-plane heat conduction, reaching several thousand W m⁻¹K⁻¹. However, transforming these properties into a usable fiber form provides advantages such as continuous length and mechanical integrity, suitable for applications like textiles and thermal straps. The challenge lies in managing interfacial resistance as heat transfers between sheets, which significantly affects the fiber's overall conductivity.

The alignment of graphene sheets within the fiber is crucial, influencing how effectively heat is conducted along the fiber axis. Spinning and drawing protocols, including coagulation bath and draw ratio, are critical in determining this alignment. Graphitization further enhances conductivity by removing defects and growing crystalline domains, although the benefits diminish as crystallinity saturates. Interface engineering also plays a role in modulating junction conductance.

The literature frequently cites wet-spun graphene oxide fibers that reach about 1290 W m⁻¹K⁻¹ after graphitization. This value surpasses most metals in a flexible form. However, factors such as fiber geometry and anisotropy introduce uncertainty into conductivity measurements. The axial conductivity does not account for radial transport, highlighting the need for per-fiber measurement.

Graphene fibers are ideal for transient electro-thermal measurement techniques. These involve suspending the fiber across electrodes, applying heat, and measuring axial diffusivity. Protocols ensure accuracy by addressing self-heating bias, radiation effects, and residual-gas contributions. For non-conductive fibers, metallic coatings can be applied to extend measurement capabilities.

Using literature values like 1290 W m⁻¹K⁻¹ as a reference is only valid for similar processing conditions. Each fiber's unique alignment, treatment, and structure require individual measurement to determine its true conductivity. A comprehensive sampling plan is essential to account for variability within fiber batches, ensuring reliable statistics.

This article is part of the ACS thermal metrology knowledge hub, providing insights into graphene fiber thermal transport and measurement. For detailed measurement and formal quotes, contact our thermal testing team.