Air Permeability of Maraging Steel Cellular Parts Made by Selective Laser Melting.

Additive manufacturing, such as selective laser melting (SLM), can be used to manufacture cellular parts. In this study, cellular coupons of maraging steels are prepared through SLM by varying hatch distance. Air flow and permeability of porous maraging steel blocks are obtained for samples of different thickness based on the Darcy equation. By reducing hatch distance from 0.75 to 0.4 mm, the permeability decreases from 1.664 × 10-6 mm2 to 0.991 × 10-6 mm2 for 4 mm thick coupons. In addition, by increasing the thickness from 2 to 8 mm, the permeability increases from 0.741 × 10-6 mm2 to 1.345 × 10-6 mm2 at 16.2 J/mm3 energy density and 0.14 MPa inlet pressure. Simulation using ANSYS-Fluent is conducted to observe the pressure difference across the porous coupons and is compared with the experimental results. Surface artifacts and the actual morphology of scan lines can cause the simulated permeability to deviate from the experimental values. The measured permeability of maraging steel coupons is regression fit with both energy density and size of samples which provide a design guideline of porous mold inserts for industry applications such as injection molding.

In Vitro and In Vivo Evaluations of Mesoporous Iron Particles for Iron Bioavailability.

Chronic renal failure involving hemodialysis results in blood loss during filtration. Iron deficiency and iron deficiency anemia can result. A compensatory increase in iron dosage has many side effects including discomfort. Elemental iron is a highly-pure iron source, which reduces the frequency of dosages; the solubility decreases with increased particle size or pore size. In this study, synthesized mesoporous iron particles (MIPs) were used to relieve iron deficiency anemia. Their bioavailability was measured in vitro by a Caco-2 cell model and in vivo in iron-deficient rats. In vitro bioavailability of MIPs was examined by measuring ferritin content in the Caco-2 cell model. Iron uptake of MIPs was significantly higher than commercial iron particles, which were less porous. In vivo bioavailability of MIPs was examined by measuring body weight gain and red blood cell-related parameters, compared with the bioavailability of standard drug ferrous sulfate in iron-deficient anemic rats. Finally, average hemoglobin content and hemoglobin regeneration efficiency were significantly higher in anemic rats supplemented with commercial iron particles, compared to anemic controls. In the 28-day oral toxicity test, MIPs were not significantly toxic to rat physiology or tissue histopathology. Thus, MIPs may allow effective recovery of hemoglobin in iron deficiency anemia.