Graduation Semester and Year

Spring 2024

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Materials Science and Engineering

Department

Materials Science and Engineering

First Advisor

Maria Konsta-Gdoutos

Second Advisor

Efstathios Meletis

Abstract

The development of advanced cementitious nanocomposites relies heavily on understanding the interfacial interactions between carbon-based nanomaterials and the cement matrix, which significantly influence the material’s performance. The goal of this dissertation is to investigate the effect of dispersion/exfoliation and surface functionalization of 1D multiwall carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), and 2D graphene nanoplatelets (GNPs) in aqueous suspensions on the interface interactions of nanoengineered cementitious composites. The first objective of this dissertation is to quantitatively evaluate the degree of nanomaterial dispersion for MWCNT and CNF suspensions, in a converging manner for cement-based materials applications using spectroscopic techniques, such as UV-vis spectroscopy (UV-vis) and Dynamic Light Scattering (DLS). UV-vis spectroscopy data can be used to provide quantitative information about the dispersion degree, ε (%) of the MWCNTs and CNFs at different loadings in suspensions. The removal of amorphous carbon is instrumental in exposing the more ordered crystalline regions where higher content of -COOH and -OH groups could be grafted onto the nanomaterials’ surface, which is closely correlated with a higher degree of functionalization. In the case of GNPs, dispersion translates to exfoliation. The evaluation of the exfoliation state of GNPs is quantified by examining the reduction of the number of stack GNP layers through Raman spectroscopy. The effects of different degrees of dispersion/exfoliation for 1D and 2D nanomaterials on flexural and compressive strength, Young’s modulus, and flexural toughness of reinforced cementitious nanocomposites are investigated. The effect of surface functionalization and dispersion/exfoliation on the nanomodification of concrete’s nanostructured interfaces and the properties at the nanoscale interface of the carbon-based nanomaterials that influence the properties at macroscale and overall performance of these composites were evaluated. The interface interactions between cement hydration products and the nanomaterials play a crucial role in determining the mechanical performance of 1D and 2D carbon-based reinforced nanomaterials.

Keywords

Dispersion, Functionalization, Carbon nanotubes, Carbon nanofibers, Graphene nanoplatelets, Multiscale Characterization, Multifunctional Composites, Engineered Concrete, AFM Interface interactions

Disciplines

Civil Engineering | Materials Science and Engineering | Other Materials Science and Engineering | Structural Materials

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