Crystallization-Induced Top-Down Wormlike Hierarchical Porous α-Fe2O3 Self-Assembly

In the first large-scale investigation we found a novel crystallization-induced fabrication of top-down wormlike hierarchical porous hematite self-assembly (WHHS). WHHS results in the crystallization of stable amorphous iron oxide microbundles at higher temperatures (400 degrees C). Oxalic acid was successfully used as both a complexing and an etching agent for the preparation; etching induced a morphological transition from microbundles to microsheets. The preparation method of the ferric oxalate complex is a crucial step for the formation of WHHS. The synthesized ferric oxalate and WHHS was characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), Raman spectra, FTIR, and nitrogen adsorption analysis. We investigated the influence of decomposition temperatures and concentration of both oxalate and iron precursors on the formation of WHHS and its surface properties as well as the magnetic and electrochemical properties of the synthesized WHHS. The WHHS showed weak ferromagnetic properties. We also examined a plausible WHHS formation mechanism.