In this study, we produced biodiesel fuel from two vegetal sources, rapeseed oil and sunflower oil, by transesterification reaction. The study aims to evaluate the impact of type of alcohol, its concentration and the reaction time, while keeping constant the temperature and the catalyst on the yield and quality of the biodiesel. For alcohol, methanol and ethanol were used at a molar ratio with the oil from 3 to 24. Transesterification was performed at various reaction times; 20, 40, 60 and 90 min for each oil and defined alcohol:oil molar ratio. The influence of these parameters on the biodiesel yield and properties were investigated in terms of density, viscosity, heating value, flash point, elemental content, density and oxidative stability of the final product. The benefit of oxidation stabilizers, catechol and 4-allyl-2,6-dimethoxyphenol was investigated. Results demonstrate that for rapeseed oil, the optimum reaction conditions to obtain a higher yield and quality of biodiesel were an alcohol:oil molar ratio of 15:1, with 60-min reaction time at 50 °C; while in the case of sunflower oil, the best yield and biodiesel quality were at an 18:1 molar ratio, with a 40-min reaction time and at 50 °C. In both cases, methanol provides the highest yields of biodiesel, and the obtained products satisfy the required standards and present a similarity with mineral diesel tested in same conditions.

β-Type titanium alloys are promising materials for orthopaedic implants due to their relatively low Young’s modulus and excellent biocompatibility. However, their strength is lower than those of α- or α + β-type titanium alloys. Grain refinement by severe plastic deformation (SPD) techniques provides a unique opportunity to enhance mechanical properties to prolong the lifetime of orthopaedic implants without changing their chemical composition. In this study, β-type Ti–45Nb (wt%) biomedical alloy in the form of 30 mm rod was subjected to hydrostatic extrusion (HE) to refine the microstructure and improve its mechanical properties. HE processing was carried out at room temperature without intermediate annealing in a multi-step process, up to an accumulative true strain of 3.5. Significant microstructure refinement from a coarse-grained region to an ultrafine-grained one was observed by optical and transmission electron microscopy. Vickers hardness measurements (HV_0.2) demonstrated that the strength of the alloy increased from about 150 to 210 HV_0.2. Nevertheless, the measurements of Young’s modulus by nanoindentation showed no significant changes. This finding is substantiated by X-ray diffraction analyses which did not exhibit any phase transformation out of the bcc phase being present still before processing by HE. These results thus indicate that HE is a promising SPD method to obtain significant grain refinement and enhance strength of β-type Ti–45Nb alloy without changing its low Young’s modulus, being one prerequisite for biomedical application.