Revealing the Essential Effect Mechanism of Carbon Nanotubes on The Thermal Conductivity of Graphene Film

The addition of CNTs leads to the formation of covalent bonds, defects, lattice distortion and phonon energy localization. The introduction of CNTs reduces the IP-TC and the elastic modulus of graphene films, while it increases the OP-TC.


Supporting information
λ: wavelength (532nm) of laser in Raman testing

Raw Materials
Single-walled CNTs (TNST, 5-30 μm length, diameter<2 nm, Purity>95 wt%) were obtained from Chengdu Organic Chemicals Co. Ltd., Chinese Academy of Sciences without further purification.Graphene oxide (GO) was created by modified Hummer's method in our prior reports.

The calculation of thermal conductivity
The thermal conductivity of the film was calculated using the equation (E1): where κ, α, C p, and ρ represent thermal conductivity, thermal diffusivity, specific heat, and sample density.The C p of all samples is 850 J/ (Kg•K).The laser flash technique (LFA 447 NanoFlash and LFA 467 NanoFlash, Germany) was employed to determine the thermal diffusivity.The density of the film was explored by assessing the mass, thickness and radius of the film

X-ray photoelectron spectroscopy peak fitting process:
Firstly, the test data is imported into the XPS analysis software (XPS peak).Then, we set the background between 282 eV and 297 eV and the background type is set to Shirley.The FWHM of all samples is 0.79 (284.7 eV) and 2.26 (285.4 eV), respectively.
The FWHM of all samples is formed by fitting at the binding energy of 290.3 eV.
Furthermore, the Lorentzian-Gaussian at different binding energies is set to 20%.The final fitting results of the XPS C1s spectrum are obtained after optimization.

Fig. S3 .
Fig. S3.AFM images of the initial GO sheets

Table S1 .
The mass of GO and CNTs contained in the samples