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The puffed-rice derived carbon@Ni 3 ZnC 0.7 -400 showed RL min of −39.9 dB and the broadest absorption bandwidth of 9.9 GHz. Moreover, the composite showed good performance stability under 400 °C. [Display omitted] • Various puffed-rice derived carbon@Ni 3 ZnC 0.7 composites were prepared by chemical synthesis and annealing. • The puffed-rice derived carbon@Ni 3 ZnC 0.7 -400 mg showed best electrochemical performance. • It showed RL min of −39.9 dB and the broadest absorption bandwidth of 9.9 GHz. • The composite material can be stable at 400 °C and has good performance stability. With the rapidly development of radar detection technology and the increasingly complex application environment in military field and electromagnetic pollution surrounded by electron devices, increasingly demand is needed for electromagnetic wave absorbent materials with high absorption efficiency and thermal stability. Herein, a novel Ni 3 ZnC 0.7 /Ni loaded puffed-rice derived carbon (RNZC) composites are successfully prepared by vacuum filtration of metal-organic frameworks gel precursor together with layered porous-structure carbon and followed by calcination. The Ni 3 ZnC 0.7 particles uniformly decorate on the surface and pores of puffed-rice derived carbon. The puffed-rice derived carbon@Ni 3 ZnC 0.7 /Ni-400 mg (RNZC-4) sample displayed the best electromagnetic wave absorption (EMA) performances among the samples with different Ni 3 ZnC 0.7 loading. The minimum reflection loss (RL min) of the RNZC-4 composite reaches −39.9 dB at 8.6 GHz, while widest effective absorption bandwidth (EAB) of RNZC-4 for RL < −10 dB can reach 9.9 GHz (8.1–18 GHz, 1.49 mm). High porosity and large specific surface area promote the multiple reflection-absorption effect of the incident electromagnetic waves. The Ni 3 ZnC 0.7 nanoparticles provide a large number of interfaces and dipole factors. Analysis reveals that the RNZC-4 remained general stability under 400 °C with formation of a small amount of NiO and ZnO phases. Surprisingly, at such high temperature, the absorbing properties of the material are improved rather than decreased. Obviously, the material still maintains good electromagnetic wave performance at high temperature, and implies that the absorber shows good performance stability. Therefore, our preparations exhibit potential applications under extreme conditions and a new insight for the design and application of bimetallic carbides. [ABSTRACT FROM AUTHOR]

Ni 3 (PO 4) 2 as microwave dielectrics was investigated in terms of sintering behavior and microwave dielectric properties and synthesized using the solid-state sintering method. X-ray diffraction (XRD) data revealed that the Ni 3 (PO 4) 2 ceramics belong to the monoclinic structure with the P2 1 /c (#14) space group. The sintering behavior analysis confirmed that the sample reached a dense state at 1200 °C. It's permittivity (ε r) and quality factor (Q × f) possess distinct density-dependent features. The admirable Q × f of 83,430 GHz (at 10.21 GHz) was accomplished coupled with a low ε r of 6.23 and temperature coefficient of resonant frequency (τ f) of −24.63 ppm/°C in Ni 3 (PO 4) 2 ceramic when sintering at 1200 °C for 2 h. Thus, it is a promising candidate for microwave dielectrics with low loss and low permittivity. The dielectric properties were discussed using the chemical bond theory, and their chemical bond features were quantified. The results confirmed the significance of P–O bonds in the microwave dielectric response of Ni 3 (PO 4) 2 ceramic. [ABSTRACT FROM AUTHOR]

A novel Cu 3 (PO 4) 2 as microwave dielectrics was investigated in terms of sintering behavior and microwave dielectric properties. Samples were prepared using the solid-state sintering method. XRD data indicates that the Cu 3 (PO 4) 2 ceramic possesses a triclinic structure and belongs to the space group of P-1 (No. 2). Its microstructure was observed using a scanning electron microscope. Results confirmed that a dense ceramic was obtained at 900 °C. The permittivity and quality factor of Cu 3 (PO 4) 2 ceramics possess distinct density-dependent properties. A low permittivity (ε r) of 7.33 coupled with Q × f of 86,753 GHz (at 10.18 GHz) and τ f of −33.80 ppm/°C was obtained in the dense Cu 3 (PO 4) 2 ceramic at 900 °C for 2 h. The Cu 3 (PO 4) 2 ceramic exhibits well compatibility with Ag. Accordingly, it is a promising candidate for microwave materials with low permittivity and low loss. The microwave dielectric properties were discussed from the viewpoint of chemical bond theory. The qualified chemical bond features indicate the major contributions of P–O chemical bonds in the microwave dielectric response of the Cu 3 (PO 4) 2 ceramic. [ABSTRACT FROM AUTHOR]

This work prepared a new type of Ce 2 [Zr 1- x (Al 1/2 Nb 1/2) x ] 3 (MoO 4) 9 (CZ 1- x (AN) x M) (x = 0.02–0.10) microwave dielectric ceramics through the solid-phase process. CZ 1- x (AN) x M ceramics exhibited low dielectric constant, ultra-low dielectric loss, and near-zero resonant frequency temperature coefficient, which is suitable for 5 G technology. The effects of (Al 1/2 Nb 1/2)4+ replacing Zr4+ on the sintering characteristics, crystal structure, and microwave dielectric properties of Ce 2 Zr 3 (MoO 4) 9 (CZM) ceramics were studied systematically. In this work, CZ 1- x (AN) x M could form a pure crystal structure in the whole doping range according to the X-ray diffraction pattern. The crystal cell parameters of the ceramics were confirmed by Rietveld refinement analysis. Furthermore, the surface morphology of CZ 1- x (AN) x M sintered at the optimum sintering temperature was studied by scanning electron microscopy. Some internal parameters of the ceramics were calculated and analyzed by employing the P-V-L theory. The theoretical loss was acquired by employing an infrared reflection spectrometer. When x was 0.04 and the sintering temperature was 850 ℃, the best properties were achieved, including ε r = 10.54, Q·f = 91,476 GHz (at 9.55 GHz), and τ f = − 8.95 ppm/℃. This work studied the relationship between lattice vibration and microwave dielectric properties and discussed the influence of ion doping on microwave dielectric properties from the perspective of chemical bonds, laying a theoretical foundation for related research. [Display omitted] • The intrinsic factor of the permittivity was analyzed by IR reflectance spectroscopy. • The cell parameters were obtained through the Rietveld refinement method. • The effects of (Al 1/2 Nb 1/2)4+ the properties were explored based on the P-V-L theory. • Excellent properties including, ε r = 10.54, Q·f = 91,476 GHz, and τ f = − 8.95 ppm/℃. [ABSTRACT FROM AUTHOR]

Ce 2 [Zr 1−x (Ca 1/3 Sb 2/3) x ] 3 (MoO 4) 9 (CZ 1−x (CS) x M) (x = 0.02–0.10) ceramics were prepared by the conventional solid-state reaction method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips–Van Vechten–Levine (P–V–L) theory. Phase composition and microstructures were evaluated by scanning electron microscopy and X-ray diffraction patterns. Lattice parameters were obtained by Rietveld refinements based on XRD data. Excellent properties for Ce 2 [Zr 0.96 (Ca 1/3 Sb 2/3) 0.04 ] 3 (MoO 4) 9 ceramic sintered at 775 °C: ε r = 10.68, Q × f = 85,336 GHz and τ f = −7.58 ppm/°C were achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] The lotus seedpod-based activated carbon (LSAC) is derived from pyrolysis of lotus seedpod as biomass carbon precursor, and Co 3 O 4 is then deposited to LSAC by oxidation-precipitation and crystallization process of Co ions from Co(NO 3) 2 solution. The Co 3 O 4 particles uniformly decorate on the surface and/or the inner channels of LSAC. The optimal reflection loss (RL) value of LSAC/Co 3 O 4 -paraffin wax (PW) composite reaches −39.8 dB, and the bandwidth for RL below −10 dB and −20 dB are 10.3 and 3.0 GHz, respectively, much better than that of LSAC-PW composite for the higher magnetic loss. The addition of Co 3 O 4 particles in LSAC-PW composite significantly enhance the RL values in various thicknesses. The channels of the LSAC and decorated Co 3 O 4 can improve the abilities of multiple scattering, dipole polarization, interface polarization and magnetic loss. This composite provides a promising method to construct high performance absorbers by using biomass carbon to tune the dielectric properties of the ferromagnetic materials. [ABSTRACT FROM AUTHOR]

• Low-sintered Nd 2 (Zr 1−x Sn x) 3 (MoO 4) 9 ceramics were prepared successfully. • Rietveld refinement was used to obtain the lattice parameters. • Relationships between intrinsic factors and dielectric properties were investigated. • Performance of Nd 2 Zr 3 (MoO 4) 9 ceramics was improved by the doping of Sn4+. [Display omitted] In this work, Nd 2 (Zr 1- x Sn x) 3 (MoO 4) 9 (0.02 ≤ x ≤ 0.1) (NZSM) ceramics were successfully obtained through conventional solid-state route. Phase analysis, microstructure, and properties were investigated scientifically by XRD, SEM, and network analyzer, respectively. XRD results revealed that all samples with different substitution amounts of Sn4+ formed the pure phase with R-3c space group. The permittivity was related to the polarizability and the bond of Zr2-O5, the bond of Nd-O2 possessed a positive influence on Q×f. The reduced octahedral distortion and increased bond energy made the temperature coefficient more stable. Infrared reflection spectrum results showed that the permittivity was mainly caused by the absorption of phonon oscillation. The optimum properties (ε r = 10.34, Q×f = 74,795 GHz, τ f = −13.55 ppm/°C) were obtained when x = 0.02 sintered at 750 °C. [ABSTRACT FROM AUTHOR]