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Surface Modification of Porous Niti Shape Memory Alloy by High Temperature Oxidation and Chemical Oxidation

Author: YangMengLei
Tutor: ZhangXinPing
School: South China University of Technology
Course: Materials Processing Engineering
Keywords: Porous NiTi shape memory alloys High-temperature oxidation Chemical oxidation Surface Modification Corrosion resistance
CLC: TG174.4
Type: Master's thesis
Year: 2010
Downloads: 80
Quote: 1
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Abstract


In this thesis, the porous NiTi shape memory alloys for high temperature oxidation, chemical oxidation and chemical oxidation and subsequent oxidation of the surface modification of the combination , using scanning electron microscopy (SEM), energy spectrum analysis (EDS) and X- ray diffraction (XRD ) and other methods of surface modification system for a porous surface structure NiTi shape memory alloy structure , and the surface-modified porous NiTi shape memory alloy in physiological saline (0.9% NaCl) was immersed ( suspension ) and electrochemical corrosion tests to characterize the change of its corrosion resistance and Ni ion release behavior . The results show that high-temperature oxidation at elevated temperatures of porous NiTi shape memory alloy sheet mask experienced by the low degree of crystallinity of Ti oxides of transition to anatase TiO2 phase transformation , while decreasing Ni content in the film . However, anatase TiO2 phase obtained at the same time , the high oxidation temperature (gt; 500 oC) resulted in an oxide film due to thermal stresses occur within the micro cracks , and the substrate / oxide interface adversely affect the bonding strength of . Corrosion test results show that compared with the structure of the oxide layer with respect to its uniformity , the corrosion resistance of alloys to improve the integrity of the key. The H2O2 HCl solution system chemical oxidation treatment of porous NiTi shape memory alloy surfaces generated with Ti -based amorphous oxide integrity and relatively poor nickel oxide layer , and thus the corrosion resistance of porous NiTi shape memory alloy was significantly improved , Ni ion release significantly reduce the rate , which is very useful to improve the biocompatibility of the alloy . Preliminary studies have shown that oxidation kinetics , chemical oxidation process that the alloy changes in the quality of the oxidation reaction process and the dissolution of the equilibrium concentration of HCl and the oxidation time by the synergistic effect. The study also showed that after treatment, the chemical oxidation of porous NiTi shape memory alloy for subsequent re- oxidation treatment, at a lower temperature (400oC) the surface of the amorphous oxide is converted to anatase TiO2 phase , although following high-temperature processing still original structure oxide layer and the substrate / oxide layer interface bonding strength of an impact, but the obtained anatase TiO2 with biological activity will be higher during the subsequent deposition of hydroxyapatite layer may be provided.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology
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