Synthesis of high strength zirconia fibers by electrospinning method
Toh, Rui Hang
Date of Issue2016
School of Materials Science and Engineering
Zirconia ceramics have many attractive properties, such as high mechanical strength, outstanding fracture toughness, high temperature resistance and good chemical/corrosion resistance, which is why it had been used for a wide range of applications, such as pump seals, grinding media, fuel cell membranes, dental framework and gears, etc. Inheriting the unique properties of the zirconia ceramics, zirconia nanofibers could offer other new applications such as shape memory actuation and toughening of other brittle ceramics. In order to bring it into reality, the start will be to optimize the processing protocols to develop high strength zirconia nanofibers, which is therefore the objective of this FYP project. In this study, zirconia nanofibers doped with yttrium and/or titanium have been fabricated using electrospinning method. The different processing conditions has been explored and optimized. The nanofibers were sintered at three different temperatures, 700°C, 1100°C and 1200°C. Nanofibers without sintering were used as a comparison. Heat treatment effect on the fibers had been investigated. Finally, tensile testing has been carried out to evaluate the strength, strain and Young’s modulus of the nanofibers. Based on the data, the processing-microstructure-properties relationship would be discussed and elucidated. Results showed that feed rate of ceramic precursors and diameter of the nanofibers fabricated was positively related. The relationship of the applied voltage for spinning and the diameter of the nanofibers shared an inverse relationship. As sintering temperature increases, the diameter of the nanofibers will decrease,the grain size of zirconia increases and densification occured more significantly during sintering at 1100-1200°C. Tensile testing shown that the nanofibers that were not sintered and nanofibers sintered at 700°C exhibited elastic and plastic deformation due to the existence of polyvinylpyrrolidone. The nanofibers sintered at 1100°C and 1200°C exhibited ceramic kind of brittle behaviour due to the decomposition of polyvinylpyrrolidone at high temperature and the growth of ceramic grains. As sintering temperature increases, the strength and modulus of the nanofibers increased while the strain decreased as the nanofibers adopt ceramic behaviours. Of all, the best tensile properties were found in the fibers sintered at 1200°C of tensile strength of 45.13 MPa for yttrium-zirconia nanofibers.
Final Year Project (FYP)
Nanyang Technological University