“…Secondly, the void space and interspaces in the shell-core structures enable the full exposure of NiO/NiCo 2 O 4 mixture materials to the atmosphere, which facilitates the introduction of electromagnetic waves and produces dielectric resonance [43, 44]. Thirdly, the unique yolk-shell structure of NiO/NiCo 2 O 4 mixtures can reflect and absorb the absorbed electromagnetic waves multiple times to enhance the loss of electromagnetic waves in the sample [45, 46]. Fig.…”
The NiO/NiCo
2
O
4
mixtures with unique yolk-shell structure were synthesized by a simple hydrothermal route and subsequent thermal treatment. The elemental distribution, composition, and microstructure of the samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscope (SEM), respectively. The microwave absorption property was investigated by using vector network analysis (VNA). The results indicated that the excellent electromagnetic wave absorption property of the NiO/NiCo
2
O
4
mixtures was achieved due to the unique yolk-shell structure. In detail, the maximum reflection loss (RL) value of the sample reached up to − 37.0 dB at 12.2 GHz and the absorption bandwidth with RL below − 10 dB was 4.0 GHz with a 2.0-mm-thick absorber. In addition, the NiO/NiCo
2
O
4
mixtures prepared at high temperature, exhibited excellent thermal stability. Possible mechanisms were investigated for improving the microwave absorption properties of the samples.
Electronic supplementary material
The online version of this article (10.1186/s11671-019-2988-9) contains supplementary material, which is available to authorized users.
“…Secondly, the void space and interspaces in the shell-core structures enable the full exposure of NiO/NiCo 2 O 4 mixture materials to the atmosphere, which facilitates the introduction of electromagnetic waves and produces dielectric resonance [43, 44]. Thirdly, the unique yolk-shell structure of NiO/NiCo 2 O 4 mixtures can reflect and absorb the absorbed electromagnetic waves multiple times to enhance the loss of electromagnetic waves in the sample [45, 46]. Fig.…”
The NiO/NiCo
2
O
4
mixtures with unique yolk-shell structure were synthesized by a simple hydrothermal route and subsequent thermal treatment. The elemental distribution, composition, and microstructure of the samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscope (SEM), respectively. The microwave absorption property was investigated by using vector network analysis (VNA). The results indicated that the excellent electromagnetic wave absorption property of the NiO/NiCo
2
O
4
mixtures was achieved due to the unique yolk-shell structure. In detail, the maximum reflection loss (RL) value of the sample reached up to − 37.0 dB at 12.2 GHz and the absorption bandwidth with RL below − 10 dB was 4.0 GHz with a 2.0-mm-thick absorber. In addition, the NiO/NiCo
2
O
4
mixtures prepared at high temperature, exhibited excellent thermal stability. Possible mechanisms were investigated for improving the microwave absorption properties of the samples.
Electronic supplementary material
The online version of this article (10.1186/s11671-019-2988-9) contains supplementary material, which is available to authorized users.
“…It enhances the complex permittivity, improves impedance matching of composites and reduces the reflection of electromagnetic waves on the incident interface. On the other hand, electromagnetic wave can be reflected many times in HMG after passing through the coating and absorbed many times by Ni-Zn ferrite and PT [13]. It strengthens the absorption of electromagnetic waves that have entered the media and avoided the electromagnetic wave returning to the interface.…”
Section: Microwave Absorbing Propertiesmentioning
confidence: 99%
“…When the thicknesses of these HGMs/Fe 3 O 4 composites are more than 1.5 mm, they all exhibit strong absorption peaks (lower than À 10 dB). A possible mechanism of the improved microwave absorption properties was discussed [10].…”
Section: Introductionmentioning
confidence: 99%
“…But it is lack of dielectric and magnetic loss properties. Hollow glass microspheres coated with the ferrite can solve the above mentioned problems in preparing absorbent material [13]. Fu et al reported that spinel CoFe 2 O 4 coating on the surface of HGMs with low density was synthesized by co-precipitation method and a remarkable absorption (about À 8.5 dB) appeared at 18 GHz [12].…”
“…It was also seen that the strength and non-dependent strain bearing properties depend on the wall-thickness-to-diameter ratios [29,30] in which greater cavity diameters offer better performance. It has also been demonstrated that ceramic hollow microspheres can be used as lightweight thin microwave absorbers by coating the printed ceramic structure with ferrites as well as with a conductive Co-Fe thin layer [4,31]. The usage of Co-Fe film enables easy magnetization of ceramic particles.…”
Geometrically-complex and lightweight ceramic parts manufactured via 3D printing are prospective structures that seem to provide excellent thermal, wear and dielectric performance. In the present work, binder jetted parts based on synthetic lightweight ceramic hollow microspheres were manufactured and evaluated under different testing conditions in order to characterize their mechanical performance. The resulting structures were assessed in terms of quasi-static flexural and compressive strength, and density. Furthermore, microscopy analyses highlighted the composition of the final structures and fracture mechanisms. The printed system mainly consisted of aluminum silicon dioxide, fly ash and traces of metal. The samples yielded similar strength as that achieved on conventional bulk-based 3D printed ceramic structures. It was observed that the strength of the printed microspheres increased by sintering the parts to near-fusion temperatures due to viscous flow of material during sintering. The combination of the proposed process and feedstock represents an attractive manufacturing method for fabricating lightweight structures for applications like composite tooling molds, electromagnetic devices, and biomedical implants.
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