다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

A review on carbon/magnetic metal composites for microwave absorption

A new kind of low-temperature fired Eu2Zr3(MoO4)9 ceramic was fabricated by conventional solid-state reaction method. The mixed powders was calcined at 600 ℃ and the samples were sintered at 500 ℃ –700 ℃ for 4 h. X-ray diffraction analysis and Rietveld refinement indicated that Eu2Zr3(MoO4)9 belonged to a trigonal system with space group R-3c. Bond ionicity, lattice energy and bond energy of the ceramic were calculated by the complex chemical bond theory. Microwave dielectric properties were determined at microwave frequencies of 9.7–14.7 GHz by a network analyzer. Far infrared spectra indicated the main contribution to polarization for Eu2Zr3(MoO4)9 ceramics was the absorption of structural phonon oscillation. The ceramic sintered at 600 ℃ for 4 h exhibited the best dielectric properties with a relative permittivity (er) of 10.75, a quality factor (Q·f) of 74,900 GHz and a temperature coefficient of resonance frequency (τf) of -8.88 ppm/℃.

Crystal structure, infrared spectra and microwave dielectric properties of novel extra low-temperature fired Eu2Zr3(MoO4)9 ceramics

Three-phase PANI@nano-Fe3O4@CFs heterostructure: Fabrication, characterization and investigation of microwave absorption and EMI shielding of PANI@nano-Fe3O4@CFs/epoxy hybrid composite

The earliest microwave absorbing materials (MAMs) are fabricated in the early 20th century for military purpose to inhibit radar detection. Currently, the application of MAMs has been existing in every part of human's life to prevent radiation and interference. The microwave absorbant and microwave absorbing coatings classified by composition including alloys, metal oxides, conductive polymers, carbon materials, ceramic materials both in traditional and innovative forms are introduced in this work. Considering the harsh and complex application environment, MAMs with high temperature resistance and infrared-compatible stealth performance are involved. Metamaterials, showing excellent electromagnetic properties which are far beyond that of the materials can achieve, including perfect absorber, digitally coded control metamaterials, bionic structural materials, and adjustable smart metamaterials, are also introduced specifically in this work. In addition, to investigate electromagnetic response of absorbant, the first-principles calculations works are overviewed. The electromagnetic properties, loss mechanisms, structure, fabrication method, regulation approaches, designing principles, current applications, and future prospects of MAMs are involved in this work. This work gives a comprehensively overview over the MAMs for their theoretical and experimental advances in recent years including the military radar (frequency range of 2–18 GHz) stealth materials, relevant infrared compatible (infrared-visible, infrared-radar, infrared-laser) stealth materials, and other stealth materials with multifrequency adaptability.

Research advances in composition, structure and mechanisms of microwave absorbing materials

Dielectric and microwave absorption properties of KNN/Al2O3 composite ceramics

The work attempted to develop a new kind of high temperature microwave absorption material. Dense Na3Zr1.9M0.1Si2PO11.9 (M = Ca2+, Ni2+, Mg2+, Co2+, Zn2+) and Na3Zr2-xZnxSi2PO12-x (x = 0.1, 0.2, 0.3, 0.4) ceramics were prepared by solid-state reactions for phase, microstructure characterization and dielectric properties, microwave absorption properties analysis. Results show that the complex permittivity increases in all the divalent-doped Na3Zr2Si2PO12 ceramics. Na3Zr1.8Zn0.2Si2PO11.8 ceramic exhibits the highest complex permittivity and optimum microwave absorption performance. The lowest reflection loss is -28.1 dB at 9.88 GHz and the bandwidth is 4.14 GHz (8.26–12.4 GHz) with a thickness of 2.1 mm. It indicates that Na3Zr2Si2PO12 ceramic can be chosen as a potential candidate of microwave absorption material and the performance can be enhanced by divalent doping strategy.

Dielectric and microwave absorption properties of divalent-doped Na3Zr2Si2PO12 ceramics

Dielectric and microwave absorption properties of CB doped SiO2f/PI double-layer composites

Microwave absorption of M-type hexaferrite Ba1-xCaxFe12O19 (x ≤ 0.4) ceramics in 2.6–18 GHz

Structural and functional integrated absorbing materials have received extensive attention in recent years. Single-layer absorbing material composites in X and Ku bands (8.2–18 GHz) were prepared by using different proportion of carbon black (CB) incorporated quartz glass fiber reinforced polyimide resin (SiO2f/PI). The morphology, mechanical, dielectric and microwave absorbing properties of the composites were investigated. Different contents of CB with different distributions were observed according to the fractural morphology of the composites. When the CB content is up to 8 wt%, the flexural strength of the composite reaches a maximum value of 705 ± 5 MPa. The real and imaginary parts of complex permittivity both show an increasing trend with the CB content increase. Meanwhile, the real and imaginary parts decrease with the increase of frequency, exhibiting frequency-dependent dielectric response. The reflection loss of the composite was calculated based on the transmission line theory, which is in a good agreement with the experiment.

Lu Gao

Papers

Dielectric and microwave absorption properties of KNN/Al2O3 composite ceramics

Dielectric and microwave absorption properties of divalent-doped Na3Zr2Si2PO12 ceramics

Dielectric and microwave absorption properties of CB doped SiO2f/PI double-layer composites

Microwave absorption of M-type hexaferrite Ba1-xCaxFe12O19 (x ≤ 0.4) ceramics in 2.6–18 GHz

Mechanical, dielectric and microwave absorption properties of carbon black (CB) incorporated SiO 2f /PI composites