Manufacturing of reliable Zirconia toughened Alumina for joint replacement.
Peh, Wee Yang.
Date of Issue2013
School of Materials Science and Engineering
Singapore Institute of Manufacturing Technology
Zirconia toughened alumina (ZTA) composites with addition of pristine multiwalled carbon nanotubes (MWCNT) and nickel-coated multiwalled carbon nanotubes (Ni-MWCNT) ranging from 0.01 wt% to 0.20 wt% were prepared using gelcasting. Samples were densified after sintering at a temperature of 1550 °C in vacuum for 2 h and relative densities ranging from 97% to 99% were obtained. Raman spectroscopy was conducted to confirm the preservation of carbon nanotube structures after the completion of composite fabrication. Agglomeration of carbon nanotubes along grain boundaries were observed under scanning electron microscope and the agglomerate size increased with increasing carbon nanotube content. These agglomerates were found to hinder the densification of samples and led to the poorer mechanical performance as compared to pure ZTA. However, ZTA-Ni-MWCNT samples were found to possess smaller pores sizes, higher sintered relative densities, smaller carbon nanotube agglomerates as well as smaller grain sizes as compared to ZTA-MWCNT samples. These factors were found to contribute to the slightly more superior mechanical performance of ZTA-Ni-MWCNT samples in terms of hardness as well as flexural strength. No significant changes in the fracture toughness of ZTA were observed when both MWCNT and Ni-MWCNT were used. Overall, it can be concluded that the agglomeration of carbon nanotubes was the main factor limiting the mechanical performance of the samples. Hence, future work should be focused on the optimization of the ratio of polyvinylpyrrolidone to carbon nanotubes in order to enhance the dispersion of carbon nanotubes. Other factors such as types of dispersant, interfacial interactions, surface functionalization and aspect ratio of carbon nanotubes could also be considered for future studies.
Final Year Project (FYP)
Nanyang Technological University