Current Issue : October-December Volume : 2025 Issue Number : 4 Articles : 5 Articles
We report a coherent tri-frequency microwave signal generation approach using an optoelectronic oscillator (OEO). In the previous literature, the OEO-based schemes can only generate coherent microwave signals with dual frequencies. In this work, we demonstrate that the generation of coherent tri-frequency microwave signals is also possible using an OEO loop. The key component in our scheme is a tri-passband electrical filter, which has a narrow passband in the middle and two wide passbands on both sides. The OEO loop initially oscillates at the central frequency of the narrow passband with a single-tone f 1. By injecting a microwave signal, f inj, into the OEO loop, down- and up-converted microwave signals at frequencies of f 2 = f 1 − f inj and f 3 = f 1 + f inj, respectively, are generated by frequency mixing in a microwave mixer. The two wide passbands of the electrical filter allow the oscillation of the converted signals at a wide frequency bandwidth by simply tuning the frequency of the injected signal. Moreover, the tri-frequency microwave signals are phase-locked through frequency mixing and mutual injection locking. The proposed scheme is theoretically analyzed and experimentally validated. In the experiments, coherent tri-frequency microwave signals with low phase noise are successfully generated at a fixed frequency of 14 GHz and two tunable frequency ranges from 9 to 12 GHz and from 16 to 19 GHz, respectively....
This study presents an innovative approach to processing refractory zinc-bearing clinker using microwave thermal treatment followed by acid leaching. Microwave irradiation induces phase transformations, converting sphalerite (ZnS) to zincite (ZnO), and generates microcracks that enhance clinker porosity and reactivity. These changes significantly improve zinc dissolution during sulfuric acid leaching. Key parameters—acid concentration, temperature, solid-to-liquid ratio, and leaching time—were optimized, achieving a zinc extraction of 92.5% under optimal conditions (40 g/L H2SO4, solid-to-liquid ratio 1:4, 600 ◦C, 5–7 min) compared to 39.1% without pre-treatment. Thermodynamic analysis confirms the higher reactivity of ZnO, driven by favorable Gibbs free energy and exothermic reaction characteristics. These findings demonstrate the potential of microwave processing to intensify hydrometallurgical processes, offering energy efficiency and environmental benefits for industrial zinc recovery....
This paper investigated the preparation of NiSb/NiSe nanomaterials using a microwave method and explored their electrochemical properties and potential applications in supercapacitors. The NiSb/NiSe nanomaterials were synthesized on nickel foam using microwave radiation, resulting in uniformly distributed flower-like nanostructures. This structure not only provided abundant electrochemical reaction sites, but also improved the electrical conductivity and ion diffusion, contributing to the overall performance of supercapacitors. Electrochemical tests showed that the NiSb/NiSe material exhibited a high specific capacity of 525 mAh g−1 at 1 A g−1 and maintained 65% capacity after 8000 cycles, demonstrating excellent cycling stability and battery-type charge storage capability. In addition, a hybrid supercapacitor assembled using NiSb/NiSe as the anode material and activated carbon (AC) as the cathode material achieved an energy density of 100.34 Wh kg−1 at a power density of 774.9Wkg−1, significantly enhancing energy storage efficiency. The effect of different microwave powers and reaction times on the morphology and electrochemical properties of the materials were further investigated, with the optimal preparation conditions found to be 800 W and 150 s. The NiSb/NiSe materials synthesized under this condition not only have the best electrochemical properties, but also exhibit low charge transfer impedance and excellent electrical conductivity. In summary, NiSb/NiSe flower-like nanomaterials as supercapacitor electrode materials demonstrate great potential for energy storage applications due to their high specific capacity, good cycling stability and high energy density....
In this study, a microwave-assisted sulfuric acid recovery method is proposed for the efficient recovery of high-value carbon fibers at 100–140 ◦C. The recycled carbon fibers (RCF) were characterized, and recycled carbon fiber-reinforced plastics (RCFRP) were fabricated using their fibers. The recycling process preserved the surface morphology of the carbon fibers, with the RCF maintaining the axial groove structure on the surface of the virgin carbon fiber (VCF). X-ray diffraction (XRD) and Raman spectroscopy analyses confirmed that the degree of graphitization and crystalline structure of the RCF remained largely unchanged compared to the original carbon fibers. Surface oxidation occurred during the recycling process, leading to an increase in O–C=O content on the surface of the RCF compared to that of the VCF, which facilitated interfacial chemical bonding with the resin and enhanced the wettability. Compared to virgin carbon fiber-reinforced plastics (VCFRP), RCFRP retained up to 95.25% of the tensile strength, 97.47% of the shear strength, and 96.76% of the bending stress, demonstrating excellent mechanical properties. This study provides a simple and effective approach for the low-temperature and high-efficiency recycling of carbon fiber composites....
Composite catalysts combining absorbers and active metal hold significant potential for improving the efficiency of biomass microwave-assisted pyrolysis (MAP). Compatibility optimization of composite catalysts can be facilitated through comparative analysis for the influential mechanisms of absorbers and catalysts. Therefore, decoupling experiments about the MAP of Sargassum and calculations based on density functional theory (DFT) were conducted in this research, to investigate the influential mechanisms of absorbers and active metal. The results show the introduction of both the absorbers (SiC) and active metal (MgO) increase the yields of high-value components, such as hydrogen and hydrocarbons. However, their influential mechanisms are different. The introduction of SiC enhances the heating rate within the reaction zone, shortening the duration of MAP and inhibiting the condensation of bio-oil and the interaction between bio-oil and biochar, and thereby increasing the bio-oil yield by 4%. The introduction of MgO lowers the energy barriers for macromolecular decomposition and gas generation, promoting the decomposition of bio-char and bio-oil, and thus leading to a 12% increase in the yield of biogas. This research conclusion provides a theoretical basis for the optimization and design of composite catalysts....
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