Preparation, Microwave Absorption and Infrared Emissivity of Ni-doped ZnO/Al Powders by Coprecipitation Method in the GHz Range

Ruiwen Shu,Honglong Xing,Xiaoli Cao,Xiaoli Ji,Dexin Tan,Ying Gan 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.4

In this work, Ni-doped ZnO/Al composites were prepared by a facile chemical co-precipitation method. The morphology and structure of the as-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the flakelike Al powders were successfully coated by Ni-doped ZnO nanoparticles with slight aggregation and Ni2+ was successfully doped into the crystal lattice of ZnO. Moreover, the effects of ZnO concentration and doped Ni concentration on the infrared emissivity of ZnO/Al composites at the waveband range of 8–14 µm were studied. The results showed that the ZnO/Al composites exhibited the lowest infrared emissivity of 0.34 with 50 wt.% ZnO concentration. Meanwhile, the electromagnetic parameters and microwave absorbing properties of Ni-doped ZnO/Al composites in the frequency range of 2–18 GHz were explored. Significantly, 12 mol.% Ni-doped ZnO/Al composites presented the lowest infrared emissivity of 0.37 and the maximum reflection loss reached -32.5 dB at 13.6 GHz with a thickness of 4.5 mm. The excellent microwave absorbing properties could be attributed to the good impedance match, crystal lattice defects and interfacial polarization. It was believed that the Ni-doped ZnO/Al composites could be used as potential infrared-microwave compatible stealth materials.

Coprecipitation Synthesis of Fe-doped ZnO Powders with Enhanced Microwave Absorption Properties

Ruiwen Shu,Xin Wang,Yingying Yang,Xiayu Tang,Xian Zhou,Yangfan Cheng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.12

In this work, the Fe-doped ZnO powders have been synthesized by a facile chemical coprecipitation method. The structure, morphology and magnetic properties of the as-prepared powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrum (EDS), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). The results showed that the Fe ions were well incorporated into the crystal lattice of ZnO and had a valence state of +3. The magnetization curves indicated the Fe-doped ZnO presented the ferromagnetic behavior at room temperature. Moreover, the electromagnetic (EM) parameters and microwave absorption properties of Fe-doped ZnO/paraffin wax in the frequency range of 2–18 GHz were explored. The minimum reflection loss reached -38.4 dB at 6.6 GHz, and the reflection loss less than -10.0 dB was 4.0 GHz (from 11.0 GHz to 15.0 GHz) with a thickness of only 2.5 mm. Significantly, the enhanced microwave absorption of the as-prepared powders could be achieved by doping with Fe3+ ions or varying the thickness of the absorbers. The mechanism of microwave absorption were attributed to the good impedance matching, the dielectric loss resulted from the crystal lattice defects and the magnetic loss originated from the natural resonance. It is believed that the Fe-doped ZnO powders could be used as potential microwave absorbers.

Solvothermal Synthesis of Reduced Graphene Oxide/Ferroferric Oxide Hybrid Composites with Enhanced Microwave Absorption Properties

Ruiwen Shu,Meng Wang,Yingying Yang,Siyu Chang,Gengyuan Zhang,Ying Gan,Jianjun Shi,Jie He 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.12

In this work, reduced graphene oxide (RGO)/ferroferric oxide (RGO/Fe3O4) hybrid composite was successfully fabricated by a facile one-step solvothermal method. The structure, chemical composition, morphology and magnetic properties of the samples were investigated in detail. Fe3O4 microspheres with an average diameter of 250 nm were uniformly anchored on the surface of the RGO sheets without large aggregation. Moreover, the results demonstrated that the hybrid composite exhibited obviously enhanced microwave absorption properties compared with the pure Fe3O4 microspheres. The minimum reflection loss (RL) of the hybrid composite reached -36.8 dB at 17.2 GHz with a thickness of 5.0mm and its effective absorption bandwidth (lower than - 10 dB) was 3.9 GHz with a thickness of 2.5 mm. Significantly, the hybrid composite exhibited a dual-waveband absorption characteristic covering the C and Ku bands. Besides, the relationship between the matching thickness and peak frequency was reasonably explained according to the quarter-wavelength matching theory. Therefore, the obtained composite was a promising candidate for application in microwave absorption.

Rheological Behavior and Electrical Properties of Graphene Oxide/Polyaniline Nanocomposites

Qing Yin,Ruiwen Shu,Honglong Xing,Dexin Tan,Ying Gan,Guocai Xu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.2

In this work, graphene oxide/polyaniline (GO/PANI) nanocomposites were synthesized by an in situ polymerization of aniline monomer in GO aqueous dispersions. The morphology and structure of GO/PANI were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra and Raman spectra. The effects of the concentration of GO/PANI and temperature on the rheological behavior of silicone oil dispersions of GO/PANI nanocomposites were investigated. The results showed that the steady state viscosity of GO/PANI dispersions remarkably increased with the addition of only little GO and the concentrated dispersions showed characteristic shear-thinning behavior. Significantly, a Newtonian-pseudoplastic transition with a critical exponent of 2.2 was observed in silicone oil dispersions of GO/PANI with the increase of nanocomposites concentration. The viscosity of GO/PANI dispersions apparently decreased with increasing temperature, while the temperature showed a certain effect on the thixotropic behavior of concentrated dispersions. In addition, the effect of the GO content on the electrical conductivity of GO/PANI nanocomposites was also explored. It was noted that the GO sheets are effective fillers for improving the rheological behavior and electrical conductivity of PANI matrix. Therefore, the study of rheological behavior and electric property of GO/PANI nanocomposites could shed light on the processing and application of GO/conductive polymer nanocomposites.

Enhanced Microwave Absorption Properties of CeO2 Nanoparticles Supported on Reduced Graphene Oxide

Qing Yin,Honglong Xing,Ruiwen Shu,Xiaoli Ji,Dexin Tan,Ying Gan 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2016 NANO Vol.11 No.5

In this work, reduced graphene oxide/CeO2 nanocomposites (RGO/CeO2) with two different RGO contents were synthesized using a facile one-step hydrothermal method, and the microwave absorption properties of RGO/CeO2 were investigated for the first time. Morphology and structure analysis shows that the CeO2 nanoparticles are uniformly dispersed on the RGO sheets with average size of 15 nm. The as-prepared RGO/CeO2 exhibits excellent microwave absorbability. An optimal reflection loss (RL) of -32 dB is found at 17 GHz with a coating layer thickness of 1.5 mm. The product with a coating layer thickness of only 2.0 mm shows a bandwidth of 4.3 GHz, corresponding to RL at -10 dB (90% of electromagnetic wave absorption). Compared with pristine RGO or pure CeO2 nanoparticles, the reported nanocomposites achieved both wider and stronger wave absorption in the frequency range of 2–18 GHz. The enhanced microwave absorption properties are attributed to the conductive loss and dielectric loss mainly caused by the higher oxygen vacancy concentration of CeO2 in RGO/CeO2, which is demonstrated by X-ray photoelectron spectroscopy. Moreover, multiple interfacial polarizations occurring in the multi-interfaces between CeO2 and RGO sheets may be beneficial to microwave absorption. RGO/CeO2 could be used as an attractive candidate for the new type of microwave absorptive materials.

Synthesis of rGO/TiO2/CdS Nanocomposites and its Enhanced Photoelectrochemical Performance in Determination of Parathion-Methyl

Jianjun Shi,Yan Wang,Li-Rong Meng,Jing-Chun Zhu,Ruiwen Shu,Jie He 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.5

A photoelectrochemical (PEC) sensor for the determination of organophosphate pesticides (OPs) was developed based on rGO/TiO2/CdS photoactive nanomaterials. The rGO/TiO2/CdS nanocomposites were prepared by solvothermal method and electrochemical deposition technique successively. The morphologies and structures of the as-prepared nanocomposites were extensively investigated by SEM and XRD. In alkaline condition, p-nitrophenol as the hydrolysate of parathion-methyl (PM) could be obtained by a simple hydrolyzation process. Under optimal conditions, the rGO/TiO2/CdS NPs modified ITO electrode exhibited a good PEC performance toward the hydrolysate of PM. The photocurrent intensity was enhanced with the increase of the concentration of the hydrolysate of PM. The proposed PEC method could detect PM in the range from 0.05 nmol L -1 to 10 nmol L -1 with a detection limit of 0.02 nmol L -1 (S/N = 3). Thus, the excellent performance of the rGO/TiO2/CdS nanocomposites serve as the matrix of the sensor, which provides a new way for the fabrication of high-sensitivity PEC sensing system.