The effect of plastic deformation process on the dissolution rate of biocompatible Mg alloys was investigated. Two biocompatible MgLi1Ca0,2Zn1 and MgLi1Ca1Zn1 alloys were selected for the study. The alloys were deformed on a 100T press at a temperature of 350°C by conventional extrusion and by the equal channel angular extrusion process (ECAE). The grain size analysis showed a high degree of the grain refinement from approximately 110 mm in the initial state to 2.8 mm after the 3rd pass of the ECAE process. Compared to as-cast state, the degree of strengthening has increased after plastic forming. The results of biodegradation tests have shown a significant increase in corrosion rate after both conventional extrusion and ECAE, although after subsequent ECAE passes, this rate was observed to slightly decrease in the MgLi1Ca1Zn1 alloy. Based on the results of macro- and microstructure examinations, the corrosion progress in samples after the extrusion process was described.
Poly(glycerol succinate) – PGSu – is one of glycerol polyesters which has focused nowadays the interest of scientists developing new biomaterials. Probably the polyester could be used as a drug carrier or as a cell scaffold in tissue engineering. Due to its potential use in medicine, it is extremely important to develop a synthesis and then optimize it to obtain a material with desired properties. In this work one flask two-step polycondensation of glycerol and succinic anhydride to PGSu is presented. Synthesis was optimized with the simplex method and also described using a second-degree equation with two variables (temperature and time) to better find the optimum conditions. PGSu was characterized by FTIR spectroscopy, NMR spectroscopy, degree of esterification was determined, and also molecular weight was calculated for each experiment using Carothers equation. A new synthesis route was developed and optimized. Temperature and time influence on molecular weight and esterification degree of obtained polyester are presented. Based on experiments conducted in this work, it was possible to obtain poly(glycerol succinate) with molecular weight of 6.7 kDa.
The purpose of this study was to investigate the mechanical properties of beta type aged Ti-4Mo-4Cr-X (X = V, Sn, Zr) quaternary alloy for use as a cardiovascular stent. Titanium (Ti) alloys were fabricated using a vacuum arc remelting furnace process. To homogenize the specimens of each composition and remove the micro segregation, all cast specimens were subjected to homogenization at 850℃ for 4 h, which was 100℃ higher than the β-transus temperature of 750℃. The tensile strength and elongation of the aged Ti-4Mo-4Cr-X (X = V, Sn, Zr) alloys were increased as compared to the homogenized alloys. In addition, many α/β interface boundaries formed after aging treatment at 450°C, which acted as inhibitors of strain and caused an increase in tensile strength. The elongation of Ti-4Mo-4Cr-X alloys consisting of α + β phases after aging treatment was improved by greater than 30%. Results of a potentiodynamic polarization test showed that the lowest current density of Ti-4Mo-4Cr-4Sn with 1.05 × 10–8 A/cm2 was obtained. The present Ti-4Mo-4Cr-X alloys showed better corrosion characteristics as compared to the 316L stainless steel and L605 (Co-Cr alloy) cardiovascular stent alloys.