Naturally Derived a-Tricalcium Phosphate Based Porous Composite Bead Production

In this study, a simple, innovative approach is applied to produce porous a-TCP-CeO2-Al2O3 composite beads via using bovine bone-derived hydroxyapatite, cerium oxide, and alumina ceramics. Bovine-bone derived hydroxyapatite was obtained via calcination of bones at 950°C for 3 hours. Hydroxyapatite is a thermally unstable biomaterial at high temperatures, and depending on its stoichiometry decomposes at 800-1200°C. Sodium alginate was successfully used as an in situ gelling templates for the production of the ceramic beads and starch, an environmentally friendly and economic pore-forming agent, is used to achieve interconnected, highly open porosity containing composite beads. Sintering of the ceramic−starch−alginate green composite beads at 1200°C for 1 hour resulted in the decomposition of the hydroxyapatite phase and formation of a-TCP. XRD analysis revealed that a-TCP-CeO2-Al2O3 composite beads were achieved. XRD analysis confirmed the formation of a-TCP phase in all composite compositions. SEM investigations of the produced composite beads revealed that bimodal pore size distribution, fine and coarse, was achieved.

Study of the relationship between hydro-mechanical soil behavior and microstructure of a structured soil

Structured soils, such as residual laterites or volcanic ashes, abound in tropical regions. The hydro-mechanical behavior of these soils is clearly related to their structure. New techniques based on microstructural studies constitute a powerful tool for investigating these soils. This work presents an experimental investigation that documents the relationships between the microstructure and the mechanical behavior of these soils. This study focuses on the microstructural behavior of Brasilia clay, a structured, highly porous tropical soil (n>50%) with a bimodal pore size distribution. The microstructure was investigated using pore size distribution analyses of different structural states and void ratios. The mercury intrusion porosimetry (MIP) technique was used to explore the pore size distribution of samples in various conditions, i.e., natural, compacted, slurry or consolidated states. Modeling of the pore size distribution curves was performed using the bimodal van Genuchten curve, which permits the linking of the pore size distribution curves (PSD) to the water retention curve. We observed that loading and compacting did not affect the micro-pores of this soil, and we conclude that the changes occurred entirely within the macro-pores.

Pt–CeO2 nanoporous spheres – an excellent catalyst for partial oxidation of methane: effect of the bimodal pore structure

Bimodal pore size distribution played the most important role for the catalyst's superior activity during POM.