Mutsuhiro Shima

The correlation between the structure and magnetic properties of chemically synthesized Co-Ni-Al ternary alloy films is investigated with a focus on the effects of KOH treatment during the synthesis on the crystal structure and magnetization. XRD measurements prove that low-temperature heat treatment (LTHT) at 333 K, followed by KOH treatment from the metal nitrates, promotes the growth of highly (001)-oriented layered double hydroxides (LDH) precursor. Subsequent annealing of LDH at 1173 K yields its transformation to the spinel oxide. Heat treatment at 1173 K in a N ₂ :H ₂ gas atmosphere promotes phase transformation to a ternary alloy in BCC and ordered B2 structure. LTHT and KOH treatment enhance the magnetic anisotropy of films due to the change in crystallinity and crystallographic orientation in LDH, oxide, and alloy films. Controlled phase transformation from LDH to alloy provides a bottom-up pathway to attain highly oriented magnetic alloy films via a chemical route.

This study investigates the synthesis and characterization of Fe–ZnO/GO composites aimed at enhancing magnetic characteristics and improving the photocatalytic degradation of organic contaminants. Reflux condensation was used to synthesize Fe-doped ZnO, which was then mixed with graphene oxide (GO) to form a composite. Energy-dispersive X-ray spectroscopy and electron microscopy demonstrated homogeneous Fe–ZnO dispersion on GO sheets. In contrast, a structural study using X-ray diffraction confirmed the wurtzite phase of ZnO, with peak changes indicative of Fe integration. UV–visible spectroscopy demonstrated an expanded absorption range and a reduced bandgap of 2.76 eV in Fe–ZnO/GO compared to 3.06 eV in ZnO. Photoluminescence studies showed decreased electron–hole recombination due to GO’s electron-accepting properties. The Fe–ZnO/GO composite outperformed Fe–ZnO (97.46%) and ZnO (58.16%) in terms of photocatalytic degradation efficiency for Rhodamine B under UV light, achieving 99.32% degradation within 24 h. A first-order rate constant of 0.2093 h^–1, 5.80 times greater than ZnO, was found via kinetic analysis. The combined effects of GO for improved charge separation and reactive oxygen species generation, and Fe doping for enhanced light absorption, were attributed to the superior performance. Vibrating sample magnetometry confirmed the ferromagnetic behavior of Fe–ZnO/GO, with a saturation magnetization of 7.69 × 10^–4 emu/g. This indicates that the material can be easily separated using a magnetic field, which is beneficial for recycling and reuse. The enhanced photocatalytic activity, structural stability, and reusability make Fe–ZnO/GO a promising candidate for environmental remediation. However, further improvement in its visible-light response and long-term stability is needed for large-scale water treatment applications.