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Optimization of components and micromorphology regulation are shown to be effective in boosting electromagnetic wave absorption (EMWA). One approach to achieve this enhancement is by utilizing the polarization effects of heterogeneous interfaces. Herein, NiSe2‐CoSe2@C@MoSe2 composites derived from NiCo‐MOF‐74 are fabricated via a facile selenization reaction and subsequent hydrothermal method. By varying the mass ratios of NiSe2‐CoSe2@C and MoSe2, a series of NiSe2‐CoSe2@C@MoSe2 composites with hierarchical flower‐like core–shell structures are obtained. The EMWA properties of the composites display a trend of initially increasing and then decreasing with the increasing content of MoSe2. Interestingly, when the mass ratio of NiSe2‐CoSe2@C and MoSe2 is 3:2, the minimum reflection loss (RL) value is −50.10 dB and an effective absorption bandwidth (RL< −10 dB) value can reach 4.80 GHz (13.20–18.00 GHz). The remarkable EMWA capability can be ascribed to the synergy effects of conductive loss, polarization loss, and suitable impedance matching. This work establishes a new pathway for the synthesis of transition metal dichalcogenides‐based composites, which hold great promise as high‐performance materials for EMWA applications. [ABSTRACT FROM AUTHOR]

Rational design of the components and microstructure is regarded as an efficacious strategy for the high-performance electromagnetic wave absorbing (EMWA) materials. Herein, the CoTe2@MoS2 nanocomposites with CoTe2 nanorods and MoS2 nanosheets were synthesized via a hydrothermal method. The microstructure and composition of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The CoTe2@MoS2 composite was composed of stacked CoTe2 as the core and intertwined MoS2 nanosheets as the shell. The electromagnetic parameters of the CoTe2@MoS2 composites were investigated by vector network analyzer (VNA). The EMWA property of the composite showed a trend of first increasing and then decreasing with the increasing content of MoS2. When the mass ratio of MoS2 and CoTe2 was 1:1, the CoTe2@MoS2 composite exhibited the minimum reflection loss value of −68.10 dB at 4.71 GHz, and the effective absorption bandwidth value might reach 4.64 GHz (13.08–17.72 GHz) at a matching thickness of 1.60 mm with filler loading of 50 wt.%. The extraordinary EMWA property was attributed to the optimized impedance matching, multiple scattering and reflections, dipole polarization, conductive loss, and interfacial polarization. Therefore, the present approach to the design of microstructure and interface engineering offers a crucial way to construct high-performance EMW absorbers. [ABSTRACT FROM AUTHOR]

As a substitute for R22, an environmentally friendly zeotropic mixture R417A is often employed. The large glide temperature of the zeotropic mixture R417A could cause capacity and efficiency reductions due to changes in its composition after an isothermal vapor leak/recharge process. It is, therefore, necessary to predict the composition change in R417A under all leak conditions. This paper presents the experimental analysis of the mass composition of R417A in the presence of a 0--50% isothermal vapor leak/recharge in a heat pump water heater. Based on the experimental data, a simple model is proposed to describe the composition change in R417A for various leaks and recharge scenarios. The effect of composition change in the performance of a heat pump water heater is also dealt with. Experimental results show that the composition changes in R417A increase as ambient temperature decreases. Isothermal vapor leaks have a great effect on the composition of R417A and the performance of a heat pump water heater at lower temperatures. It is also found that when the ambient temperature is higher than 7[degrees]C with a 10% leak and R417A recharge, there is almost no difference in the performance of the plant with respect to the original state except that the compressor discharge temperature is lower [DOI: 10.1115/1.4000173] Keywords: heat pump, R417A, leakage, ternary mixture