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Scaffolds for the filling and regeneration of osteochondral defects are a current challenge in the biomaterials field, and solutions with greater functionality are still being sought. The novel approach of this work was to obtain scaffolds with biologically active additives possessing microstructural, permeability, and mechanical properties, mimicking the complexity of natural cartilage. Four types of scaffolds with a gelatin/alginate matrix modified with hydroxyapatite were obtained, and the relationship between the modifiers and substrate properties was evaluated. They differed in the type of second modifier used, which was hydrated MgCl2in two proportions, ZnO, and nanohydroxyapatite. The samples were obtained by freeze-drying by using two-stage freezing. Based on microstructural observations combined with X-ray microanalysis, the microstructure of the samples and the elemental content were assessed. Permeability and mechanical tests were also performed. The scaffolds exhibited a network of interconnected pores and complex microarchitecture, with lower porosity at the surface (15 ± 7 to 29 ± 6%) and higher porosity at the center (67 ± 8 to 75 ± 8%). The additives had varying effects on the pore sizes and permeabilities of the samples. ZnO yielded the most permeable scaffolds (5.92 × 10–11m2), whereas nanohydroxyapatite yielded the scaffold with the lowest permeability (1.18 × 10–11m2), values within the range reported for trabecular bone. The magnesium content had no statistically significant effect on the permeability. The best mechanical parameters were obtained for ZnO samples and those containing hydrated MgCl2. The scaffold’s properties meet the criteria for filling osteochondral defects. The developed scaffolds follow a biomimetic approach in terms of hierarchical microarchitecture and mechanical parameters as well as chemical composition. The obtained composite materials have the potential as biomimetic scaffolds for the regeneration of osteochondral defects.

The aim of this work is to present experimental results related to the use of calcium carbonate as pore generating agent. Four compositions containing 20 wt.% of limestone were used and characterized chemically and thermally. Each composition was homogenized in a porcelain ball mill, dried in a laboratory drier, humidified at 7 wt.%, and pressed in an uniaxial hydraulic press. Compacted samples were dried and heat treated with a suitable heating rate for the degasification of calcium carbonate and sintered at 800, 900, and 1050 oC. Sintered samples were characterized to determine the porosity, crystalline phases formed and microstructural features. The results showed that the porosity has increased with the sintering temperature of the compositions increasing due porosity generated by the calcium carbonate degasification and the material expansion.

This study aimed to examine the behavior of different filter media used in gas filtration at high pressure. Trials were carried out having phosphate concentrate as the particulate matter and compressed air as fluid. Operating conditions were evaluated at the following absolute pressures of the system: 193, 393 and 693 kPa, and the gas velocity was kept constant at 0.05 m/s. The results indicated that, for a given pressure drop at the filter, the highest absolute pressure applied to the system (693 kPa) yielded the highest powder mass deposited on the filter medium. An analysis of the porosity of dust cakes revealed that the increase in pressure resulted in cakes which were more porous and less resistant to gas flow. It was also verified that the increase in the pressure of the system provided an increase in the fractional efficiency of the filters for particles smaller than 5 μm.

The most common method to produce biodiesel is the transesterification of oils in the presence of methanol and a catalyst. Catalysts may be either homogeneous or heterogeneous, whereas the heterogeneous consume fewer resources, energy and are reusable, being considered an environmentally attractive approach. This research presents the production of a heterogeneous catalysis system for biodiesel synthesis, consisting of alumina foam with a thin coating of SrO. The support, obtained by direct foaming of suspensions, presented approximately 90% vol. of highly connected pores. The SrO film was obtained by soaking the ceramic foam into either a Pechini resin with SrO precursors or an aqueous solution of strontium nitrate, followed by heating to 1400°C for 2 hours. The density and permeability of samples were evaluated and microstructure was characterized by EDS and SEM. The results show that the use of ceramic foams as catalyst support is feasible using the proposed route.