Microwave

In this study, the microwave heating efficiency of a water body is investigated with different shape factors. In particular, the same water volume was deposited in cylindrical containers with different diameters. Here, “shape factor” refers to the ratio between the surface fluid layer, which strongly absorbs microwave energy, and the inner layer, which is heated largely via conduction. For a liquid in a cylindrical container, the shape factor is characterised as the ratio between the depth and diameter of the air/water surface area. The heating efficiency is characterised by relating the energy absorbed in the outer fluid layer with the energy gained in the bulk and monitoring the temperature in the fluid bulk at the point that the outer layer commences boiling. A correlation equation for the uniformity of the sample heating (with stirring) provided a simple link between the physical factors and microwave (MW) parameters. It was found that a depth/diameter ratio approaching 1:1 provided the most uniform heating. The correlations between the fitting parameters and physical conditions provide a simple yet effective method to characterise the thermal homogeneity of microwave heating that can assist with practical parameterisation of the design of microwave reactors.

The editors of Microwave extend their sincere thanks to every reviewer who assessed manuscripts for the journal in 2025 [...]

In this study, we investigate the dominant electromagnetic wave absorption mechanism–ferromagnetic resonance (FMR) loss versus quarter-wave cancellation in a novel PVDF-based polymer composite embedded with carbonaceous nanostructures incorporating FeCoCr ternary alloy. The majority of the nanoparticles are embedded at the terminal ends of the carbon nanotubes, while a small fraction exists as isolated core–shell, carbon-coated spherical particles. Overall, the synthesized material predominantly exhibits a nanotubular carbon morphology. High-resolution transmission electron microscopy (HRTEM) confirms that the encapsulated nanoparticles are quasi-spherical in shape, with an average size ranging from approximately 25 to 40 nm. The polymeric composite was synthesized via solution casting, ensuring homogenous dispersion of filler constituent. Electromagnetic interference (EMI) shielding performance and reflection loss characteristics were evaluated in the X-band frequency range. Experimental results reveal a significant reflection loss exceeding −20 dB at a matching thickness of 2.5 mm, with peak absorption shifting across frequencies with thickness variation. The comparative analysis, supported by quarter-wave theory and FMR resonance conditions, indicates that the absorption mechanism transitions between magnetic resonance and interference-based cancellation depending on the material configuration and thickness. This work provides experimental validation of loss mechanism dominance in magnetic alloy/polymer composites and proposes design principles for tailoring broadband microwave absorbers.