Dissertation
Mechanical and corrosion behavior of CNFs reinforced porous magnesium
Doctor of Philosophy (PhD), Washington State University
01/2016
Handle:
https://hdl.handle.net/2376/112750
Abstract
Porous magnesium is a promising biomaterial. However, the mechanical behavior of porous magnesium has not been well understood yet. Additionally, little information of the corrosion rate has been reported. The object of this study is to manufacture Carbon Nanofiber (CNFs) reinforced porous magnesium (Mg) composites and understand their mechanical and corrosion behavior. Our research provides comprehensive information on mechanical and corrosion rates of porous Mg/CNFs composites for the first time.
Magnesium powder was mixed with space holder urea and CNFs by ball milling machine and was sintered at 250°C for 4 hours and 630°C for 2 hours. The samples were characterized by compressive mechanical test, SEM, OM, vicker hardness and XRD. Powder metallurgy method is suitable for manufacturing porous magnesium composites for biomedical applications since it preserves the biocompatibility of magnesium composites.
In addition, three different ball milling times were investigated: 240, 320 and 480 minutes. The different ball milling times had a significant impact on powder mixture homogeneity, CNFs dispersion, sample morphology and composite hardness. CNFs reinforcing effect varied because the amount of fibers within the urea powders varied by batches and lost their attachment to the composite matrix after sintering.
Many empirical models were discussed to examine their suitability for predicting the elastic modulus and yield strength of the synthesized composites. Adjusted porosity corrected models for the elastic modulus had a decent agreement with the experimental results. However, the mismatch of predicted and experimental results was not acceptable. For yield strength prediction, only Rule of Matrix model had a reasonable agreement with the experiment results.
The corrosion rates of the different composites were measured. The CNFs can be considered as a defect in corrosion behavior in the composites because it increased the corrosion rates. Furthermore, high content of MgO, which was produced during sintering, weakened the matrix bonding and led to high corrosion rate or even the disintegration of the composites. Finally, high porosity led to the high corrosion rate in general because of larger and more open pores.
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Details
- Title
- Mechanical and corrosion behavior of CNFs reinforced porous magnesium
- Creators
- Huiru Xu
- Contributors
- Qizhen Li (Advisor)Qizhen Li (Committee Member)Jinwen Zhang (Committee Member)Hussein M. Zbib (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Materials Science and Engineering Program
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 220
- Identifiers
- 99900581633001842
- Language
- English
- Resource Type
- Dissertation