| Summary: | 碩士 === 國立臺灣海洋大學 === 材料工程研究所 === 101 === This research aims to investigate the irradiation-induced monoclinic (M) tetragonal (T) phase transformation of pure M-phase zirconia free standing and nanocladded nano-particles, by using various ion sources and energies. The zirconia nano-particles were isolated and embedded into a non-reacting metal (silver) matrix, named nanocladding, by internal oxidation method, which were constrained by the Ag matrix and then would be sub¬jected to internal, or external hydrostatic pressure, potentially resulting in different variances from free standing zirconia nano-particles. Two separate specimens, i.e. well-prepared M-ZrO2 nano-particles with and without Ag cladded, were sequentially irradiated by using National Electrostatics Corporation 9SDH-II 3MV Tandem Accelerator with 1.5 MeV H+ and 3 MeV Fe2+in Institute of Physics Academia Sinica and High Voltage Engineering Europa 500 kV ion implanter with 100 keV H+ in National Tsing Hua University. The fluencies are from 1×1014 to 1×1016 ions/cm2. These irradiated specimens were studied and characterized by using X-Ray diffractometer (XRD) and transmission electron microscopy (TEM).
The results show that the free standing zirconia nano-particles with the size of smaller than 30 nm appear M→T phase transformation after proton implantation with 1.5 MeV and 100 keV energy at the proton doses above 3×1015 ions/cm2, while no phase transformation occurs under the grain size larger than 30 nm. Apparently, there is a size effect of irradiation-induced M→T phase transformation of the free standing M-ZrO2 nano-particles by proton implantation. However, the irradiation-induced M→T phase transformation occurs after Fe2+ ions implantation with 3 MeV energy at the fluencies just above 1×1014 ions/cm2, regardless of the size smaller and larger than 30 nm. It suggests that the heavy ions (Fe2+) transmit much more energies to zirconia nano-particles than light ions (proton), leading to an much easier phase transformation.
As for the zirconia nano-particles cladded by silver, the irradiation-induced M→T phase transformation didn’t occur by proton implantation with 1.5 MeV and 100 keV H+ energies at the fluences up to 1×1017 ions/cm2. However, it occurred M→T by Fe2+ implantation with 3 MeV energy at the fluences above 1×1016 ions/cm2. Since the mass of proton is obviously lighter than Fe2+ ion, the proton is vulnerable to deflect and scatter while encountering Ag atoms and zirconia molecules leading to the probability of colliding with zirconia molecules in the M-ZrO2 nano-particles nanocladded by Ag matrix much smaller than that in the free standing M-ZrO2 nano-particles. Moreover, in contrast to the irradiation-induced M→T phase transformation in the free standing zirconia nanoparticles by Fe2+ implantation, the needed Fe2+ dose for the irradiation-induced M→T phase transformation in the nanocladded M-ZrO2 nano-particles is much higher than that in the free standing M-ZrO2 nano-particles due to the much smaller cross-section area of colliding with M-ZrO2 nano-particles. In other words, the probability of colliding with zirconia molecules in the M-ZrO2 nano-particles nanocladded by Ag matrix is much smaller than that in the free standing M-ZrO2 nano-particles, resulting in higher Fe2+ dose needed to induce M→T phase transformation in the M-ZrO2 nano-particles nanocladded by Ag matrix.
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