Synthesis of Fe(OH)3 Microtubes at the Gas–Solution Interface and Their Use for the Fabrication of Fe2O3 and Fe Microtubes

A straightforward and effective method is reported for obtaining microtubes of iron‐based compounds by interfacial interaction between a solution and gaseous reagents. A thin amorphous film of Fe(OH)₃ was synthesized on the surface of a mixed FeCl₂/FeCl₃/ascorbic acid aqueous solution as a result of the interaction with gaseous ammonium. When dried in air, the film was oxidized and transformed into microtubes. These Fe(OH)₃ microtubes were converted into α‐Fe₂O₃ ones by annealing in air. As a result of thermal hydrogen reduction, α‐Fe microtubes were formed. Both the annealing in air and reduction in a hydrogen flow at a temperature of 1,000 °C preserve the tubular morphology of the product. The microtubes synthesized were characterized by optical and scanning microscopy, structural and compositional analyses, and Mössbauer spectroscopy. A hypothesis is proposed about the model of microtube formation resulting from the chemical reaction at the gas–solution interface.