Sousa M.P.,European Institute of Excellence on Tissue Engineering and Regenerative Medicine |
Sousa M.P.,ICVS 3Bs PT Government Assocs Laboratory |
Sousa M.P.,University of Aveiro |
Cleymand F.,Ecole des Mines de Nancy |
And 4 more authors.
Biomedical Materials (Bristol) | Year: 2016
Freestanding multilayered films were obtained using layer-by-layer (LbL) technology from the assembly of natural polyelectrolytes, namely chitosan (CHT) and chondroitin sulfate (CS). The morphology and the transparency of the membranes were evaluated. The influence of genipin (1 and 2 mg ml-1), a naturally-derived crosslinker agent, was also investigated in the control of the mechanical properties of the CHT/CS membranes. The water uptake ability can be tailored by changing the crosslinker concentration that also controls the Young's modulus and ultimate tensile strength. The maximum extension tends to decrease upon crosslinking with the highest genipin concentration, compromising the elastic properties of CHT/CS membranes: nevertheless, when using a lower genipin concentration, the ultimate tensile stress is similar to the non-crosslinked one, but exhibits a significantly higher modulus. Moreover, the crosslinked multilayer membranes exhibited shape memory properties, through a simple hydration action. The in vitro biological assays showed better L929 cell adhesion and proliferation when using the crosslinked membranes and confirmed the non-cytotoxicity of the developed CHT/CS membranes. Within this research work, we were able to construct freestanding biomimetic multilayer structures with tailored swelling, mechanical and biological properties that could find applicability in a variety of biomedical applications. © 2016 IOP Publishing Ltd.
Henein H.,University of Alberta |
Buchoud V.,Ecole des Mines de Nancy |
Schmidt R.-R.,IWT - Foundation Institute of Materials Engineering |
Watt C.,University of Alberta |
And 4 more authors.
Canadian Metallurgical Quarterly | Year: 2010
Al-0.61wt%Fe and Al-1.9wt%Fe alloys were atomized in helium and nitrogen atmospheres, using impulse atomization. The microstructure of the droplets atomized in helium and nitrogen were characterized using a number of techniques including X-ray diffraction, micro-tomography and scanning electron microscopy (SEM). In both alloys, a fully dendritic microstructure with α-Al present as the primary phase and lamellar interdendritic regions were found. The volume fraction of eutectic was measured as a function of particle size, atomized gas and Fe content. These measurements clearly indicate that a significant amount of microsegregation and metastability occurs for both alloys. Measurements of the volume fraction of eutectic were used to estimate the degree of eutectic undercooling. It is found that assuming that the eutectic is composed of α-Al and Al4Fe phases, the undercooling is about 10°C and 17°C for the 0.61 and the 1.9 wt% Fe alloys. The maximum solubility of Fe in the primary α-Al phase is 0.068 wt% and 0.12 wt% in the 0.61 and 1.9 wt% Fe alloys and the eutectic is found at 3.1 and 5.5 wt% Fe for these two alloys, respectively. Calculated cooling rates using the metastable values of the phase diagram for each alloy showed that the cooling rates ranged from 20 to 10,000 K/s. The measured cell spacing λ, was linked to the cooling rate CR according to the equation λ = B × CR-n where B and n are constants, depending on the composition of the alloy. Good agreement was found between the experimentally determined coefficients B and n and those calculated from the coarsening model proposed by Kurz and Fisher . © Canadian Institute of Mining, Metallurgy and Petroleum.
Pessey D.,University of Strasbourg |
Bahlouli N.,University of Strasbourg |
Raveyre C.,Jean Monnet University |
Guillet J.,Jean Monnet University |
And 3 more authors.
Polymer Engineering and Science | Year: 2010
In this work, contamination effects are studied on two polypropylene-based materials. These effects were identified on the molecular weight and on rheological and mechanical properties. Model contaminants chosen in this study were ethylene glycol and engine oil. They were added during the extrusion process to simulate the degradation due to contaminants. To quantify contamination effects and to correlate them with the microstructure evolution, scanning electron microscope (SEM) analyses were also conducted. The analysis of the different obtained results led to a better understanding of the mechanisms involved in the contamination process. Contaminants slightly affect the rheological properties, whereas mechanical properties are more influenced. These observations are confirmed by the modification of the fractured surfaces of the materials due to the presence of contaminants observed on SEM micrographs. © 2009 Society of Piastics Engineers.