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In the present work, to enhance the reflection loss and change the magnetic resonance frequency of barium ferrite sintered at low temperature, different amounts of Zr ion were introduced to BaFe12O19 to substitute the Fe ion. A series of M-type barium hexaferrite samples having the nominal composition BaZrxFe(12−x)O19 (x = 0.0, 0.3, 0.6, 0.9 and 1.2) was successfully synthesized by heat treatment at a relatively low temperature (900 °C) for 2 h. In order to study the phases, morphologies and magnetic properties of the substituted barium ferrites, X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM) were used. The XRD patterns indicated that all samples were single phase M-type ferrites. The SEM images showed that all samples were hexagonal-shaped particles and the average size was about 500 nm. Simultaneously, a potassium chloride additive can effectively reduce the sintering temperature of barium ferrites and their formation and morphology are apparently not affected. The VSM results demonstrated that the coercivity steeply decreased from 4772.43 Oe to 797.34 Oe when the Zr ion substitution amount increased from 0.0 to 1.2 but the saturation magnetization remained almost constant (Ms = 49.71–63.06 emu g−1). Furthermore, the complex electromagnetic parameters were collected by a vector network analyzer (VNA) and the microwave absorbing properties were calculated according to transmission theory. It was found that the reflection loss is enhanced with increasing x. The minimum reflection loss value of −30.2 dB at 16.75 GHz was observed and the bandwidth is about 2.46 GHz for the x = 1.2 sample. BaZrxFe(12−x)O19 might be a promising candidate for applications of LTCC (low-temperature co-fired ceramic) substrates for millimeter wave circulators and filters.

In the present work, to enhance the reflection loss and change the magnetic resonance frequency of barium ferrite sintered at low temperature, different amounts of Zr ion were introduced to BaFe

Hydrometallurgical leaching process enhanced by electric field coupled with sodium persulfate was developed to improve the leaching efficiency of vanadium. A high vanadium leaching efficiency of 95.64% was achieved under the optimal conditions, including roasting temperature at 650 °C, 5 wt% sodium persulfate, current density of 1000 A/m2, leaching temperature of 60 °C, leaching time of 30 min, liquid-solid ratio of 0.5 mL/g. X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the mechanism. Results indicated that the low-temperature roasting changed the phase of vanadium, while O2 produced in electric field promoted the chemical conversion and oxidation process. Meanwhile, electric field expedited the collision among the moving particles, therefore it facilitated the dissolution of wrapped vanadium. It also found that electric field and sodium persulfate had synergetical effect on oxidization of low-valent vanadium to high-valence, which made the leaching efficiency increased by 26.94%. A high selective extraction of vanadium was obtained by electro-oxidation leaching with the characteristic diffraction peak of the main phases disappeared in the XRD pattern, while leaving a residue composed primarily of silicon dioxide and iron oxide. These findings could provide guidance for utilization of vanadium slag.