An ultrahigh thermal conductive graphene flexible paper

Abstract

Graphene nanosheets (GNSs) possess outstanding conductivity, good thermal and chemical stabilities and desirable mechanical strengths. However, the unfunctionalized GNSs are hydrophobic and insoluble in water, which limits their application in many technological areas. Herein, we report a design strategy to exfoliate few-layered aqueous dispersible graphene by a simple ball-milling technique. The modifier of sodium lignosulfonate (LS) enables to synthesize LS-decorated GNSs from natural graphite based on the strong π-π interaction, greatly improving GNSs dispersion in water. The resultant GNSs exhibit a high production yield (∼100%), high dispersion concentration and excellent film formation ability. The electrical and thermal conductivities of the as-prepared graphene paper were up to 2385 S cm and 1324 W m K, respectively, superior to those of most previously reported graphene materials. This graphene paper with the superb electrical and thermal conduction properties also exhibits excellent mechanical flexibility and structure intensity during bending, which has potential usages in electronic packaging and high power thermal management.

Production and Patterning of Liquid Phase–Exfoliated 2D Sheets for Applications in Optoelectronics

“…The lateral size, morphology, shape, and thickness of the 2D nanosheets are usually determined via microscopic characterization by high‐resolution transmission electron microscopy (HR‐TEM) and atomic force microscopy (AFM) (see examples in Figure ). While the former allows the estimation of the number of layers of exfoliated ( N L ) sheets by counting the number of sheet's edges and by using electron diffraction patterns, the latter enables the estimation of N L by measuring the height of the flakes and dividing it by the corresponding interlayer distance . Yet, it is important to note that the estimation of SL flakes height via AFM varies with the nature of the substrate (e.g., roughness, hydrophobicity, or hydrophilicity) and depends on the magnitude of the force applied by the tip to the sample as well as the experimental conditions such as relative humidity .…”

“…Copyright 2017, American Chemical Society; c) AFM images represent SL and FL graphene. Reproduced with permission . Copyright 2017, Royal Society of Chemistry; d) AFM images of EE h‐BN nanosheets.…”

“…Noncovalent interaction assisted ball milling, especially π‐π interaction between aromatic molecules (melamine, triazines, and pyrene) and the surface of graphite, led to the faster exfoliation and production high‐quality graphene. [20,65b,118] Ding et al developed an effective method to formation an ultrahigh thermal conductive graphene flexible paper by ball milling technique in the presence of sodium lignosulfonate, which enabled to exfoliate SL and FL graphene from natural graphite (Figure d). As a result, high concentrated graphene dispersion exhibited excellent film formation ability.…”

A water-based green approach to large-scale production of aqueous compatible graphene nanoplatelets

“…The thickness of the film could be adjusted in the range 3~50 μm along with the different volume and concentration of graphene dispersion, and the conductivities of these films were further measured. These films were found to exhibit mean conductivity of 2.1 ± 0.1 × 10 4 S m −1 before annealing and can be further improved to 4.8 × 10 4 S m −1 after annealing at 500 °C for 2 h, which is much higher than the most of graphene films prepared by similar solution exfoliation 13 – 18 , 26 – 29 , 35 , 36 . Because the films were produced through a slow process, the annealing would be more ordered and decrease the content of oxygen-containing groups on graphene surface, which would result in the electrical conductivity enhancement.…”

“…3a–c ). The SAED pattern images reveal the isolated single-layer GNPs with the typical hexagonal symmetry 29 – 31 . GNPs were further analyzed through high-resolution TEM (HR-TEM) and these images were listed in Fig.…”