1. Dispersion of Carbon Nanotubes in Alumina using a Novel Mixing Technique and Spark Plasma Sintering of the Nanocomposites with Improved Fracture Toughness
Nabi Bakhsh1,a*, Fazal Ahmad Khalid1,b, Abbas Saeed, Hakeem2,c, Tahar Laoui2,3,
1. Faculty of Materials Science and Engineering, GIK I, Topi, Swabi, KPK, Pakistan
2. Centre of Excellence in Nanotechnology, KFUPM, Dhahran 31261, Kingdom of Saudi Arabia
3. Mechanical Engineering Department, KFUPM, Dhahran 31261, Kingdom of Saudi Arabia
ABSTRACT
METHODS
The present study emphasizes on the fabrication of carbon nanotubes (CNTs) reinforced alumina nanocomposites for structural applications. A new technique for the mixing and dispersion of CNTs in alumina powder was employed. Spark plasma sintering (SPS) technique was used for the fabrication of nanocomposites with varying amounts of as-received CNTs (1, 2 and 3 weight %) in alumina matrix. Densification behavior, hardness and fracture toughness of the nanocomposites were studied. A comparison of mechanical properties of the desired nanocomposites was presented. An improvement in fracture toughness of approximately 14% at 1 wt% CNT-alumina nanocomposite over monolithic alumina compacts was observed due to better dispersion of CNTs in alumina matrix that ultimately helped in grain growth suppression to provide finer grain in the nanocomposites. The fractured surfaces also revealed the presence of CNTs bridging and pull out that aided in the improvement of mechanical properties. The synthesized samples were characterized using field emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, densification, Vickers hardness testing and fracture toughness measurements.
Gas Purging Sonication
INTRODUCTION
The discovery of CNTs has opened up a new era in the field of nanotechnology. Current research is mainly focused on the synthesis and characterization of CNT-reinforced polymers, metals, or ceramic matrix nanocomposites. Uniform dispersion of CNTs in the matrix is indispensable for predictable properties and optimal performance of nanocomposites. Different chemical and/or physical approaches have been employed to de-agglomerate the CNTs that are bonded with strong Van der Waal’s forces.
RESULTS
Morphology of CNT and Alumina
Morphology of CNT/Al2O3 composites after GPS
OBJECTIVES
Dispersion of CNTs in alumina employing Gas Purging Sonication (GPS).
Fabrication of 1, 2 and 3 wt% CNT-reinforced alumina nanocomposites using spark plasma sintering at 1400°C.
Characterization and comparison of CNT-alumina nanocomposites with monolithic alumina.
FESEM image (a) as-received CNTs (b) alumina powder
SEM images of (a) 1 wt% CNT/Al2O3,(b) 3 wt% CNT/Al2O3
Mechanical Properties of Nanocomposites
Graphs showing (a) Densification and hardness, (b) Fracture toughness of nanocomposites.
Structural Properties of Nanocomposites
CONCLUSIONS
The effect of GPS and sintering parameters on the behavior of CNT/Al2O3 nanocomposites has been investigated.
It is found that CNT/Al2O3 nanocomposites can be sintered to near full density using SPS without damaging the structure of CNTs. At 1 wt% CNT-alumina, the fracture toughness is improved by 14% due to good dispersion of CNTs within the alumina grains.
Fig. (a) Raman spectrum of sintered CNT/Al2O3;XRD scans of sintered (b) Monolithic Al2O3, (c) 1 wt% CNT/Al2O3, (d) 2 wt% CNT/Al2O3, (e) 3 wt% CNT/Al2O3 nanocomposites.
FRACTOGRAPHY
ACKNOWLEDGEMENT
Higher Education Commission (HEC) of Pakistan is acknowledged for the financial support and scholarship to Nabi Bakhsh.
Authors acknowledge the support of the Center of Excellence in Nanotechnology & Center for Engineering Research, Research Institute, KFUPM.
FESEM Fractographs of : (a) Monolithic Al2O3, (b) 1 wt% CNT/Al2O3, (c) 2 wt% CNT/Al2O3, (d) 3 wt% CNT/Al2O3 nanocomposites.