Enhanced physical properties of γ-Al2O3-rGO hybrids prepared by solvothermal and hot-press processing.

Mujtaba Ikram,Jianglin Ye,Zhuchen Tao,Xuemei Sun,Jin Xu,Hafiz Adil Qayyum

doi:10.1039/c8ra00095f

Abstract

In this study, a solvothermal method was employed for the first time to fabricate hybrids composed of cross-linked γ-Al2O3 nanorods and reduced graphite oxide (rGO) platelets. After calcination and hot-press processing, monoliths of Al2O3–rGO hybrids were obtained with improved physical properties. It was found that the oxygen-containing groups on graphene oxide were beneficial for the adsorption of aluminum isopropoxide, leading to a uniform dispersion of rGO with Al2O3, which was obtained by hydrolysis of aluminum isopropoxide during the solvothermal reaction. The hybrid, which was subsequently calcinated for 3 h showed electrical conductivity of 6.7 × 101 S m−1 together with 90% higher mechanical tensile strength and 80% higher thermal conductivity as compared to the bare Al2O3. In addition, the dielectric constant of the hybrid was 12 times higher than that of the bare Al2O3. In this study, the highest values of electrical conductivity (8.2 × 101 S m−1), thermal conductivity (2.53 W m−1 K−1), dielectric constant (104) and Young's modulus (3.7 GPa) were obtained for the alumina–rGO hybrid calcinated for 1 h. XRD characterization showed that an increase in calcination temperature and further hot-press processing at 900 °C led to enhanced crystallinity in the γ-Al2O3 nanorods in the hybrid, resulting in enhanced physical properties in the hybrids.

Highlights

Due to its high thermal conductivity (5000 W mÀ1 KÀ1), high electrical conductivity (106 S mÀ1), high Young's modulus (1 TPa) and high intrinsic strength (130 GPa),[1,2] graphene is considered as an ideal candidate to improve the electrical, mechanical and thermal properties of metals, polymers and ceramics.[3]
The Thermogravimetric analysis (TGA) curves of the g-Al2O3–reduced graphite oxide (rGO) powder samples show that different calcination times led to different concentrations of rGO in the hybrids
The TGAs curves of all the hybrids show a stable weight loss between 400 C and 600 C, which is ascribed to the removal of all the carbon-related materials,[20,22] and other impurities a er heating to 800 C in air atmosphere

Summary

Introduction

Ceramics usually have a brittle attribute with low strength.[11]. Among the numerous ceramics, alumina is one of the widely used structural ceramic due to its good thermal conductivity and shape capability.[12]. Paper rGO/poly(ethylenimine) composite was used to capture carbon dioxide from ue gas.[20] In a microwave preparation of alumina– rGO composites, the grain size of the alumina matrix was reduced to 180 nm as compared to 475 nm grain size obtained from the conventional sintering process, leading to an increase in the Young's modulus of 180 GPa from 148 GPa under the same measurement conditions.[21] in most of the previous reports on alumina–rGO, there is no complete systematic study on the physical properties of Al2O3–rGO such as investigation of dielectric, mechanical, electrical, and thermal properties. It is found that with the 3 h-calcinated hybrid, the Al2O3–rGO monoliths show enhanced electrical conductivity (ranging from 5.1 Â 10À10 S mÀ1 to 6.7 Â 101 S mÀ1), mechanical tensile strength (90%), thermal conductivity (80%) and a much higher dielectric constant (12 times) than the bare Al2O3. For the Al2O3–rGO monoliths, the effect of calcination temperature on the length, diameter and aspect ratio of the alumina nanorods is discussed

Preparation of g-Al2O3–rGO hybrid powder

Characterization

Results and discussion