Determining the sintering kinetics of Fe and FexOy-Nanoparticles in a well-defined model flow reactor

A model flow reactor provides a narrow particle temperature-residence time distribution with well-defined conditions and is mandatory to measure changes of the particle structure precisely. The experimental data of iron and iron oxide agglomerates are used to determine the sintering kinetics considering the temperature-time history of the particles. Thousand particle trajectories are tracked in a validated CFD model at three different furnace temperatures each. Strongly agglomerated particles with a small primary particle size (similar to 4 nm) are synthesized by spark discharge and are size-selected (25-250 nm) before sintering. The structure development is measured simultaneously with different online instrumentations and the structure calculated by means of structure models. A simple sintering model, based on the reduction of surface energy, is numerically quantified with the experimental results. The surface of the particles is strongly dependent on the primary particle size and the agglomerate structure. The chemical phase is analyzed using the offline techniques XANES, XRD, and EELS. It is observed that the addition of hydrogen led to a reduction of iron oxide to iron nanoparticles and to changes of the sintering kinetics. The sintering exponent m = 1 was found to be optimal. For Fe, an activation energy E-a of 59.15 KJ/mol and a pre-exponential factor A(s) of 1.57 10(4) s/m were found, for Fe(3)O(4 )an activation energy E-a of 55.22 kJ/mol and a pre-exponential factor A(s) of 2.54 10(4) s/m.

Automated summary

In this study, a model flow reactor was used to measure and analyze the sintering kinetics of iron and iron oxide agglomerates using experimental data. The results showed that the addition of hydrogen led to the reduction of iron oxide to iron nanoparticles and changes in the sintering kinetics. This study is important for a deeper understanding of particle structure and sintering behavior.