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Fabrication and Biocharacter of Composite Coating on Mg-Zn Based Alloy

Author: ChenJuan
Tutor: GuanShaoKang
School: Zhengzhou University
Course: Materials Processing Engineering
Keywords: Magnesium alloy Composite coating Micro-arc oxidation Biocompatibility Biodegradable characteristics
CLC: TG174.4
Type: Master's thesis
Year: 2009
Downloads: 70
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Abstract


With the development of society and the progress of medicine, biodegradable implant materials gradually become one of the hot spots of the biomedical materials sector research. Magnesium alloy for its excellent bio-security, bio-mechanical compatibility and biodegradable absorption characteristics become increasingly favored by people of great potential for development of novel biodegradable metal hard tissue replacement materials. However degradation too fast, hinder the corrosion resistance and biocompatibility in vivo applications, through surface modification to improve the magnesium alloy has been studied extensively in the physiological environment of magnesium alloy in the presence of Cl - . But already modified method also exists the problem of the coating and the substrate bond strength and corrosion resistance is not enough. Therefore, seeking having good biological activity, the anti-stripping, the corrosion protection ability of new biological coating material system and its new preparation method has important significance. This article aims to micro-arc oxidation combined with a two-step method of electrodeposition has a strong resistance to corrosion, high bond strength and excellent biocompatibility of calcium and phosphorus salt / magnesium oxide bio-composite coating prepared in Mg-Zn-Ca alloy surface . In this study, the preparation and biological properties of the material, and micro-arc oxidation and electro-deposition process parameters were optimized. Analytical tools such as XRD, SEM, EDS, FTIR analysis of the coating microstructure, while the surface of the coating bond strength and wettability test. Vitro (Vitro) and in vivo (Vivo) test the corrosion resistance of the material to degradation and induction characteristics and biocompatibility. Is optimized micro-arc oxidation and electrodeposition parameters can be successful preparation of the magnesium alloy surface containing HA (Ca 10 (PO 4 ) 6 (OH) 2 ), OCP (Ca 8 H 2 (PO 4 ) 6 < / sub> · 5H 2 O), Mg 3 (as PO in 4 ) 2 and MgO composite coating The electrodeposition width approximately 2.5μm slice of calcium and phosphorus salt crystals uniformly deposited on the micro-arc oxidation surface micropores, both to improve the biocompatibility of the entire coating play a semi-sealing enhanced the entire coating corrosion resistance; coating radicals the PO 4 3 - and OH - ; composite coating thickness of about micro-arc oxidation coating thickness of about 26μm, 10μm. By the scratch test and the shear tensile test, to test the bonding strength of the composite coating. The scratch test results show that the bonding strength of 0, shear tensile test results showed that the coating bond strength ≥ 30MPa, are in line with the implantation conditions. Coating wettability tests show the two steps prepared by coating wettability good solid - liquid interface can be small, is conducive to the formation of an ideal biological binding interface between implantable bone material and bone tissue. Use of the corrosion electrochemical system testing coatings in simulated body fluid (SBF), the protective effect of the matrix, the results showed that: the two-step method composite coating corrosion resistance is superior to the one-step preparation of the coating. Compared with the matrix material, the corrosion potential of the composite coatings in simulated body fluid increased 150mV, corrosion current densities from 1.174 × 10 -4 A / cm 2 reduced to 9.131 × 10 -7 A / cm 2 , composite coatings with higher stability, better able to protect the substrate. Corrosion weight loss test results showed that the pH value of the SBF magnesium alloy specimens increased with time, soak, which lower the magnitude and speed of the elevated pH value of the two-step method composite coating. Weight loss results and the pH and the degradation rate of 1.2mg / (cm 2 · d). Vivo specimens weightlessness its in vivo 8 weeks before the average degradation rate of 0.16mg / (cm 2 · d). Vitro SBF the soaked sample SEM and EDS analysis and body remove the sample macro, morphology and EDS analysis shows excellent induction composite coating of calcium and phosphorus salts. Vitro (vitro) hemolysis test showed that: the composite coatings in the diluted blood is able to effectively protect the substrate. Without the surface treatment of the magnesium alloy hemolysis rate reached 56.27%, a modified magnesium alloy hemolysis rate was 2.49%, less than the allowable standard (5%) of the implanted, can be used for in vivo implantation. The tests include: X-ray images observed in vivo (Vivo), remove the bone in tissue samples macroscopic observation, the ion concentration of serum and urine tests, bone tissue and vital organs histopathology analysis. Eight weeks before animal experiments show that the composite coating in the body to improve the interface of the implant and the surrounding bone tissue, new bone trabeculae formation around the implant, new bone on a neatly osteoblasts, no found serious meat tooth swelling and inflammation, while the matrix material degradation in vivo, the material surrounding bone tissue disorder, foreign body giant cells and inflammatory;, the ion concentrations in serum and urine were within normal range, material degradation magnesium ion normal metabolism; important organs, heart, liver, kidney, spleen no abnormal lesions.

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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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