Systematic Studies of Enhanced Physical Properties of Ceramics Graphene Nanostructures Assembly Prepared by Solvothermal/Hydrothermal and Hot-Pressing Process

摘要

This Ph.D.dissertation deals with the fabrication of ceramics-graphene nanostructures assembly and systematic studies on enhanced physical properties of hybrids.This Ph.D.dissertation contains two main parts.
　　In the first part,a solvothermal method is employed first time to fabricate hybrids composed of cross-linkedγ-Al2O3nanorods and reduced graphite oxide(rGO)platelets.Aftercalcination and hot-press processing,monoliths of Al2O3-rGO hybrids are obtained with improved physical properties.It is found that the oxygen-containing groups on graphene oxide benefit to the adsorption of Al-(OC3H7)3(aluminum Isopropoxide),leading to the uniform dispersion of rGO with Al2O3which is hydrolyzed from aluminum Isopropoxide in solvothermal reactions.The hybrid processed at3-h calcination time shows an electrical conductivity of6.7×101S m-1,simultaneously with90％higher mechanical tensile strength and80％higher thermal conductivity,compared to the porous Al2O3.The dielectric constant of the hybrid is12times higher than that of the porous Al2O3.In this work,highest values of electrical conductivity(8.2×101S·m-1),thermal conductivity(2.53Wm-1k-1),dielectric constant(104)and young modulus(3.7GPa)are determined for alumina-rGO hybrid which is processed at1-h calcination time.
　　In the second part of Ph.D.research work,we have extended our research methodology to another ceramics-graphene nanostructure assembly i.e.silica-rGO hybrids,by optimizing experimental conditions for the hydrothermal and hot pressing process.Hydrothermal-hot press processed monolithic SiO2spheres and reduced graphite oxide(rGO)platelets are obtained with enhanced physical properties.After calcination and hot-press treatments,monolithic spheres of SiO2and rGO platelets hybrids are achieved with improved physical properties.In this case,it is found that the oxygen-containing groups on graphene oxide benefit to the adsorption of ethyl silicate(C8H20O4Si),leading to the uniform dispersion of rGO platelets with SiO2spheres which is hydrolyzed from ethyl silicate during hydrothermal reactions.In this work,best physical properties such as high electrical conductivity(0.143S·m-1),thermal conductivity(1.612Wm-1k-1),dielectric constant(107),BET surface area(712.01m2g-1),and tensile strength(225.74MPa)are measured for SiO2-rGO hybrid which processed at1-h calcination time.With1.55wt.％rGO,the SiO2-rGO hybrid shows a significant enhancement in electrical conductivity(0.02S·m-1),simultaneously with thermal conductivity(1.439Wm-1k-1),dielectric constant(500),tensile strength(98.02MPa),and BET surface area(611.21m2g1),compared to the electrical conductivity(1.9×10-6S·m-1),thermal conductivity(1.34Wm-1k-1),dielectric constant(3.79),tensile strength(75.79MPa),and BET surface area(333.07m2g1)of the bare SiO2.XRD characterizations show that the increase in calcination temperature and further hot-press processing at750℃leads to the enhanced crystallinity of SiO2spheres and rGO platelets in the hybrid,which is a significant factor for the improved physical properties of the Si02-rGO hybrids.Further,the effect of calcination and hot pressing conditions are discussed on the crystallinity of the hybrids.
　　This research work has introduced a method of hybrids preparation(which is not reported before for ceramics-graphene assembly nanomaterials i.e.γ-Al2O3-rGO,SiO2-rGO hybrids)by the use of solvothermal/hydrothermal-hot pressing methods.Further,we have made complete systematic studies on enhanced physical properties of the hybrids.This research has a significant contribution for the applications of ceramics-graphene assembly nanomaterials which can be further applied as electrolytes,catalysts,conductive,electrochemically active,and as dielectric materials for the high-temperature applications due to enhanced physical properties.

目录

声明

ABSTRACT

Table Of Contents

List of Figures

List of Tables

List of Abbreviations

Chapter 1．Introduction

1．1．1．Background and Motivation

1．2．Objectives

1．3．Thesis Organization

Reference

Chapter 2．Experimental Setup and Characterization Tools

2．1．EXperimental Setup／Fabrication Route fbr this Research Work

2．2．Characterization Tools for this Research Work

2．2．3．For Physical Properties Study of γ-Al2O3-rGO and SiO2-rGO

2．2．4．For Statistical Analysis of Nano Structures

Chapter 3．Synthesis，Characterization and Physical Properties of γ-Al2O3 Nanorods and rGO Platelets Hybrids

3．1．Introduction

3．2．Experimental Setup

3．2．1．Preparation of γ-Al2O3-rGO Hybrid Powder

3．2．2．Hot press processing of γ-Al2O3-rGo hybrids

3．2．3．Characterization Tools

3．3．Results and Discussions

3．3．2．Morphological Analysis of γ-Al2O3-rGO

3．3．3．Calcination Effect in Physical Color Change of γ-Al2O3-rGO

3．3．4．StructuraI Study of γ-Al2O3-rGO using X-ray diffraction (XRD)

3．3．5．Structural Analysis of γ-Al2O3-rGo by Raman Spectroscopy

3．3．6．Structural study of γ-Al2O3-rGo by Brunauer-Emmett-Teller (BET) Curves

3．3．7．Effect of Calcination Conditions on Crystallinity of γ-Al2O3-rGO Hybrids

3．3．8．Calcination Temperature Effect on Average Diameter of Alumina Nanorods

3．3．9．Calcination Temperature Effect on Average Length of Alumina Nano Rods

3．3．10．Study of Hot Pressing Experimental Conditions Between Alumina and Reduced Graphene Oxide

3．3．11．Study of Hot Pressing Effect on γ-Al2O3-rGO Hybrid using SEM，Raman，and XRD

3．3．12．Electrical Conductivity Measurements of γ-Al2O3 and γ-Al2O3-rGO Hybrids

3．3．13．Thermal Conductivity Measurements of γ-Al2O3 and γ-Al2O3-rGO Hybrids and Effect of Temperature on Thermal Conductivity

3．3．14．Dielectric Properties Measurements of γ-Al2O3 and γ-Al2O3-rGO Hybrids and Effect of rGO Content on Dielectric Properties

3．3．15．Compressive／Tensile Stress-Strain Curves，Young’s Modulus Study of γ-Al2O3 and γ-Al2O3-rGO Hybrids and Effect of rGO Content on Mechanical Properties

3．3．16．Comparison of Physical Properties of Hot-Press Processed Alumina-rGO Hybrids with Previous Reports

3．4．Summary

Reference

Chapter 4．Synthesis，Characterization and Physical Properties of Solvothermal-Hot Press Processed SiO2 Nano-Spheres-rGO platelets hybrids

4．1．Introduction

4．2．Experimental Setup

4．2．2．Hotpress processing of SiO2-rGO hybrid powder

4．3．Results and Discussion

4．3．2．Thermogravimetric Analysis (TGA) of SiO2-rGO Powder

4．3．3．Morphological Study of SiO2-rGO Hybrids using SEM，TEM，and SAED

4．3．4．Structural Characterization of SiO2-rGO Hybrids by X-ray Diffraction

4．3．5．Structural Analysis of SiO2-rGO using Raman Spectroscopy

4．3．6．Structural Analysis of SiO2-rGO hybrids using FTIR Spectroscopy

4．3．7．Chemical Composition and Elemental State Study of SiO2-rGO hybrids using XPS Curves

4．3．8．BET surface area，Mesoporous volume ％ Study of SiO2-rGO hybrids

4．3．9．Effect of Calcination Temperature on Crystallinity of SiO2-rGO hybrid

4．3．10．Effect of Hot Pressing on quality of graphene in SiO2-rGO hybrids

4．3．11．Study of Limited Chemical Reaction between SiO2 and rGO in Hot-Press Processing

4．3．12．Electrical Conductivity Measurements of SiO2-rGO hybrid and Effect of rGO Content on SiO2-rGO hybrids

4．3．13．Thermal Conductivity Measurement of SiO2-rGO Hybrids and Effect of rGO ％

4．3．14．Dielectric Measurements and Effect of ％ rGO Content in SiO2-rGO hybrids

4．3．15．Tensile Strength and Young’s Modulus of SiO2-rGO Hybrids and Effect of ％ rGO Content

4．3．16．Comparison of Hot-Press Processed SiO2-rGO hybrids with Previously Published Work

4．4．Summary

References

Chapter 5．Conclusions

Acknowledgment

List of Publications