Dynamics of Sorption Processes at Physical Synthesis of Iron Nanoparticles

Abstract

Scanning and transmission electron microscopy, powder X-ray diffraction and thermogravimetric analyses were used to study the dynamics of the sorption processes of ligand-free iron nanoparticles produced by highly efficient physical synthesis, namely, the molecular beam method. The structure, chemical and phase composition of Fe-NaCl condensates with different iron contents, crystallite dimensions (nanoparticles) and nanoparticle surface areas depending on the condensation temperature, which characterize the sorption capacity, primarily for moisture and oxygen, were studied. Finally, the gravimetric analysis method was used to investigate the kinetics of the relative change in the weight of porous Fe–NaCl condensates with different iron contents, depending on the condensation temperature. With increasing synthesis temperature, the nanoparticle size increases, and the specific surface area decreases. Therefore, by changing the size of the nanoparticles at the same volume, we can regulate the ratio of the nanoparticle surface to the nanoparticle volume, i.e., change the properties of the reaction surface and, in this way, the contribution of the excess surface energy to the total free energy of the system. The mass fraction of physically adsorbed and bound oxygen (moisture) correlates with the size (area, surface) of the nanoparticles.

Graphical Abstract

Sorption of oxygen and water by EB PVD ligand-free Fe@Fe₃O₄ nanoparticle in open matrix nanopore