Effect of Magnesium Addition and High Energy Processing on the Degradation Behavior of Iron Powder in Modified Hanks’ Solution for Bioabsorbable Implant Applications

This paper shows the results of applying a combination of high energy processing and magnesium (Mg) as an alloying element in a strategy for enhancing the degradation rate of iron (Fe) for applications in the field of non-permanent medical implants. For this purpose, Fe powder was milled with 5 wt% of Mg (Fe5Mg) and its microstructure and characterized degradation behavior. As-received Fe powder was also milled in order to distinguish between the effects due to high energy processing from those due to the presence of Mg. The powders were prepared by high energy planetary ball milling for 16 h. The results show that the initial crystallite size diminishes from >150 nm to 16 nm for Fe and 46 nm for Fe5Mg. Static degradation tests of loose powder particles were performed in Hanks’ solution. Visual inspection of the immersed powders and the X-ray diffraction (XRD) phase quantification indicate that Fe5Mg exhibited the highest degradation rate followed by milled Fe and as received Fe, in this order. The analysis of degradation products of Fe5Mg showed that they consist on magnesium ferrite and pyroaurite, which are known to present good biocompatibility and low toxicity. Differences in structural features and degradation behaviors of milled Fe and milled Fe5Mg suggest the effective dissolution of Mg in the Fe lattice. Based on the obtained results, it can be said that Fe5Mg powder would be a suitable candidate for non-permanent medical implants with a higher degradation rate than Fe.

Potential Bio-Fuel from Refinery Waste through Anaerobic Digestion

In this study we report biofuel potential in waste cake obtained from oil refinery. The sample was analyzed for its calorific value using auto bomb calorimeter (LECO AC-500), proximate analysis using Thermogravimetric analyzer (LECO 701) and elemental analysis using CHNS analyzer (LECO Tru-Spec). The elemental analysis of dry waste cake vs wet cake depicted the percentage composition of carbon (49.8%, 40.8%), hydrogen (7.9%, 6.0%), nitrogen (2.8%, 1.9%), Sulphur (1.9%, 0.5%) and oxygen content (37.6%, 40.4%). As for as the thermal degradation behavior of dry and wet cake in TGA is concerned, higher moisture contents (68.50%) found in wet cake and lower in dry cake (40.1%). Whereas the volatile matter in dry cake (30.9%) and low volatile in wet cake (14.3%). Similarly, %age of ash become high in dry cake (17.3%) and low in wet cake (5.11%). The results reflected that higher heating value of dry waste cake is higher (22.5 MJ/kg) than wet waste cake (20.5 MJ/kg) and commonly used sugarcane bagasse (17.88 MJ/kg).

Preliminary Investigation on Degradation Behavior and Cytocompatibility of Ca-P-Sr Coated Pure Zinc

Zinc and its alloys show a good application prospect as a new biodegradable material. However, one of the drawbacks is that Zn and its alloys would induce the release of more Zn ions, which are reported to be cytotoxic to cells. In this study, a Ca-P-Sr bioactive coating was prepared on the surface of pure zinc by the hydrothermal method to address this issue. The morphology, thickness, and composition were characterized, and the effects of the coating on the degradation, cell viability, and ALP staining were investigated. The results demonstrated that the degradation rate of pure zinc was reduced, while the cytocompatibility was significantly improved after pure zinc was treated with Ca-P-Sr coating. It is considered that the Ca-P-Sr bioactive coating prepared by the hydrothermal method has promising application in the clinic.