الفهرس 
Introduction and literature reviewOnly 14 pages are availabe for public view
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Abstract
Magnesium (Mg) and its alloys are one of a new kind of biodegradable metallic implants which attracted much essential research to improve it as orthopedic implants in clinical application. Mg implants, combine multiple interesting and useful properties such as biocompatibility and associative properties, low density, elastic modulus and compressive yield strength close to natural bones and the elimination of surgery for implant removal. Nevertheless, it has some limitations to use it in biomedical applications. As it degrades rapidly in the early period after implantation, thus lead to some problems such as fast loss of mechanical properties at an early period, aggregation of hydrogen bubble and gap formation between the implants and the tissue.
The aim of the present work is to prepare Mg-based alloys as a biodegradable alloys followed by studying the effect of several alloying elements on its mechanical properties. Enhancing the bio-compatibility of the prepared alloy will take place by coating its surface with calcium phosphate (Ca-P) layer. On the other hand, calcium phosphate (Ca-P) coatings have been suggested as a means to control corrosion rates. Measuring the degradation rate will be performed in vitro by using Simulated body fluids (SBF) before and after coating.
In this study, the effects of adding 0.5 wt% of each Sb, Sn and Bi as alloying elements on the microstructure, mechanical properties and
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Abstract
degradation behavior of as- cast Mg-4wt% Zn alloy are studied . The evaluation process was achieved using optical and scanning electron microscopy, X-ray diffraction, tensile and compression tests, in addition to a corrosion study by immersing in simulated body fluid (SBF). Results showed that the grain size of the base alloy is refined to 50% after Sb addition. This addition also enhances both the mechanical properties and degradation rate as well. These were due to the formation of the secondary phase of Mg3Sb2. The Sn-added alloy sample shows the best rate of degradation, but it shows no significant effect on mechanical properties. On the other hand, the Bi- added alloy sample shows the poorest corrosion resistance.
In order to enhance the degradation rate of the alloys under investigation, the alloy samples are coated with Ca-P using autocatalytic technique. The results demonstrated that coated Mg-4wt% Zn-0.5wt% Sb has the best corrosion resistance .
Hence, the Sb –add alloy sample is ideal as a biodegradable medical application. As it shows good rate of degradation before coating and the best corrosion resistance after coating, and the Sb addition improves the mechanical properties of Mg-4Zn alloys, however, it needs further research to study the toxic effect of Sb in biological environments.