We report herein the upscaled synthesis and shaping of UiO66-COOH for NH3 air purification. The synthesis of the zirconium-based MOF was carried out in a batch reactor in an aqueous suspension with a yield of 89% and a spacetime yield of 350 kg/day/m 3. Neither toxic chemicals nor organic solvents were used, allowing this MOF to be employed in individual or collective air purification devices. Freeze-granulation and extrusion shaping techniques were investigated. The NH3 air purification performances of UiO66-COOH in bead, tablet and extrudate forms were compared to those of commercial carbon based materials (type K adsorbents from3M and Norit). Testing conditions were chosen to reflect current standards for ammonia concentration (600-1200 ppm) and velocity. In addition, the breakthrough measurements were carried out at three different relative humidity levels (0%, 40% and 70%). Pellets and extrudates of UiO66-COOH outperformed commercial benchmark adsorbents in all conditions, especially in dry conditions, for which the commercial adsorbents suffered impaired ammonia uptake and shortened service life. Extrudates of UiO66-COOH also withstood attrition after intensive shaking.
The authors report on the manufacturing of mechanically stable β-tricalcium phosphate (β-TCP) structural hybrid scaffolds via the combination of additive manufacturing (CerAM VPP) and Freeze Foaming for engineering a potential bone replacement. In the first step, load bearing support structures were designed via FE simulation and 3D printed by CerAM VPP. In the second step, structures were foamed-in with a porous and degradable calcium phosphate (CaP) ceramic that mimics porous spongiosa. For this purpose, Fraunhofer IKTS used a process known as Freeze Foaming, which allows the foaming of any powdery material and the foaming-in into near-net-shape structures. Using a joint heat treatment, both structural components fused to form a structural hybrid. This bone construct had a 25-fold increased compressive strength compared to the pure CaP Freeze Foam and excellent biocompatibility with human osteoblastic MG-63 cells when compared to a bone grafting Curasan material for benchmark.
Freeze foaming is a method to manufacture cellular ceramic scaffolds with a hierarchical porous structure. These so-called freeze foams are predestined for the use as bone replacement material because of their internal bone-like structure and biocompatibility. On the one hand, they consist of macrostructural foam cells which are formed by the expansion of gas inside the starting suspension. On the other hand, a porous microstructure inside the foam struts is formed during freezing and subsequent freeze drying of the foamed suspension. The aim of this work is to investigate for the first time the formation of macrostructure and microstructure separately depending on the composition of the suspension and the pressure reduction rate, by means of appropriate characterization methods for the different pore size ranges. Moreover, the foaming behavior itself was characterized by in-situ radiographical and computed tomography (CT) evaluation. As a result, it could be shown that it is possible to tune the macro- and microstructure separately with porosities of 49–74% related to the foam cells and 10–37% inside the struts.
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