Title

Advanced Multifunctional Graphene-Based Paper for Thermal Management and De-icing Applications

Date of Award

1-1-2021

Degree Name

Ph.D. in Chemical and Materials Engineering

Department

Department of Chemical and Materials Engineering

Advisor/Chair

Khalid Lafdi

Abstract

Macroscopic assembly of graphene into 2D films or paper is a new form of graphene which utilizes its exceptional properties. In this effort several fabrication processes of graphene-based paper were studied, and the mechanisms of thermal management and deicing were investigated. The details of these techniques were studied and their effect on the structure, quality, and in-plane thermal conductivity of graphene-based paper was evaluated. The techniques used to prepare graphene-based paper were chemical vapor deposition (CVD), hot pressing of graphene slurry, and evaporation induced self-assembly (EISA). The thermal and electrical conductivities of the resulting papers were measured, and various structural characterizations were made, including scanning electron microscopy (SEM), Raman spectroscopy, X- ray diffraction (XRD), small angle X-ray scattering (SAXS), and optical microscopy. SEM images showed the morphology of graphene-based paper made by the different techniques. XRD patterns had a sharp peak at 26.5° to show that the matching of crystallinity for graphene paper prepared via different techniques. SAXS patterns showed high directionality for CVD graphene-based paper. In-plane thermal conductivity measurement was performed using custom-built steady state in-plane thermal conductivity device. According to the measurements of in-plane thermal conductivity, CVD graphene-based paper has highest thermal conductivity than hot pressing and EISA techniques because of long phonon mean path, absence of defects and highly orientation of CVD graphene-based paper. This was important because heat spreaders made from high thermal conductivity materials are one of the most effective techniques used to dissipate heat generated in microelectronic devices, thereby enhancing the performance and reliability of electronics. A graphene-based paper composite panel was fabricated using a wet layup / vacuum bagging technique to study the mechanism of graphene-based paper for deicing applications. An infrared (IR) thermal camera was used to show the thermal distribution during the deicing process. The efficiency of the composite panel containing the CVD-produced graphene paper was the highest due to lower phonons dispersion which led to high in-plane thermal conductivity. COMSOL Multiphysics 5 was used to simulate the electrochemical exfoliation of graphite, as well as the temperature gradient through graphene based paper when being used as a heat spreader. This exercise enhanced the fundamental understanding of the electrochemical exfoliation of graphite and the thermal distribution through graphene paper. Using this model-based numerical approach, we revealed insight into the mechanisms of the intercalation and exfoliation processes of exfoliated graphite. The predicted results showed that the concentration of intercalated sulfate anions through graphite rod was in the range (9.77x10-7 - 4.58x10-5) mol/m3. Also, the stresses applied to exfoliate graphite were in the range (3.43x10-8 - 5.77x10-7) N/m2 to overcome the van der Waals forces between graphene layers. Thermal distribution through graphene-based paper was studied numerically using conductive heat transport in solid phase in order to predict the thermal distribution for graphene paper. The simulation showed that the temperature gradient through graphene- based paper.

Keywords

Materials Science, Graphene-based paper, electrochemical exfoliation of graphite, COMSOL Multiphysics, chemical vapor deposition, evaporation induced self-assembly, In-plane thermal conductivity.

Rights Statement

Copyright 2021, author.

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