RESUMO
Hydroxyapatite and bioactive glass particles were added to pure magnesium and an AZ91 magnesium alloy and then consolidated into disc-shaped samples at room temperature using high-pressure torsion (HPT). The bioactive particles appeared well-dispersed in the metal matrix after multiple turns of HPT. Full consolidation was attained using pure magnesium, but the center of the AZ91 disc failed to fully consolidate even after 50 turns. The magnesium-hydroxyapatite composite displayed an ultimate tensile strength above 150 MPa, high cell viability, and a decreasing rate of corrosion during immersion in Hank's solution. The composites produced with bioactive glass particles exhibited the formation of calcium phosphate after 2 h of immersion in Hank's solution and there was rapid corrosion in these materials.
RESUMO
Innovative solutions have been designed to meet the global demand for energy and environmental sustainability, such as enhanced hydrocarbon recovery and geo-sequestration of CO2. These processes involve the movement of immiscible fluids through permeable rocks, which is affected by the interfacial properties of rocks at the pore scale. Overcoming major challenges in these processes relies on a deeper understanding about the fundamental factors that control the rock wettability. In particular, the efficiency of oil recovery strategies depends largely on the 3D wetting pattern of reservoir rocks, which is in turn affected by the adsorption and deposition of 'contaminant' molecules on the pores' surface. Here, we combined high-resolution neutron tomography (NT) and synchrotron X-ray tomography (XRT) to probe the previously unobserved 3D distribution of molecular and mineralogical heterogeneity of oil reservoir rocks at the pore scale. Retrieving the distribution of neutron attenuation coefficients by Monte Carlo simulations, 3D molecular chemical mappings with micrometer dimensions could be provided. This approach allows us to identify co-localization of mineral phases with chemically distinct hydrogen-containing molecules, providing a solid foundation for the understanding of the interfacial phenomena involved in multiphase fluid flow in permeable media.
RESUMO
Hydrogels have been studied as promising materials in different biomedical applications such as cell culture in tissue engineering or in wound healing. In this work, we synthesized different nanocellulose-alginate hydrogels containing cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals (CNCTs), cellulose nanofibers or TEMPO-oxidized cellulose nanofibers (CNFTs). The hydrogels were freeze-dried and named as gels. The nanocelluloses and the gels were characterized by different techniques such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA), while the biological features were characterized by cytotoxicity and cell growth assays. The addition of CNCTs or CNFTs in alginate gels contributed to the formation of porous structure (diameter of pores in the range between 40 and 150 µm). TEMPO-oxidized cellulose nanofibers have proven to play a crucial role in improving the dimensional stability of the samples when compared to the pure alginate gels, mainly after a thermal post-treatment of these gels containing 50 wt % of CNFT, which significantly increased the Ca2+ crosslinking density in the gel structure. The morphological characteristics, the mechanical properties, and the non-cytotoxic behavior of the CNFT-alginate gels improved bioadhesion, growth, and proliferation of the cells onto the gels. Thus, the alginate-nanocellulose gels might find applications in tissue engineering field, as for instance, in tissue repair or wound healing applications.