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54. The essence of the band gap of 1-D photonic crystal with period consisting of two elements.

Author

FAN Xizhi

Abstract

In order to discuss the essence of 1-D photonic crystal band gap, the reflectivity of 1-D photonic crystal consisting of two elements was analyzed, and the expression of the real part of the equivalent refractive index was derived by using the transmission characteristic matrix method. Taking the 1-D photonic crystal composed of magnesium fluoride (MgF2) and zinc sulfide (ZnS) as an example, the analytical numerical calculations of the reflectivity and the real part of the equivalent refractive index were done and the corresponding curves were drawn. It was the conclusion that, wavelength range with reflectivity of 1.0 is the same as that with real part of equivalent refractive index of zero. For the light waves in the band gap, the real part of the equivalent refractive index of 1-D photonic crystal is equal to or close to zero, namely, 1-D photonic crystal is virtual equivalent index material in the extent of band gap. In other words, the optical essence of photonic crystal band gap is that photonic crystal becomes virtual equivalent index material. This study is helpful for the study of 1-D photonic crystal with multi periods consisting of two elements. [ABSTRACT FROM AUTHOR]

Published
2021
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72. Formation mechanism of Fe2O3hollow fibers by direct annealing of the electrospun composite fibers and their magnetic, electrochemical propertiesElectronic supplementary information (ESI) available. See DOI: 10.1039/c0ce00379d.

Author

Cheng, Yongliang, Zou, Binglin, Wang, Chunjie, Liu, Yangjia, Fan, Xizhi, Zhu, Ling, Wang, Ying, Ma, Hongmei, and Cao, Xueqiang

Subjects
REACTION mechanisms (Chemistry), IRON oxides, ANNEALING of crystals, ELECTROSPINNING, FIBROUS composites, MICROFABRICATION, POVIDONE, NANOFIBERS, SOLUTION (Chemistry), TEMPERATURE effect, ELECTROCHEMICAL analysis
Abstract

Fe2O3hollow fibers have been fabricated by direct annealing electrospun polyvinylpyrrolidone (PVP)/Fe(NO3)3composite nanofibers. In this approach, composite fibers were firstly synthesized by electrospinning PVP/Fe(NO3)3solution, and then calcined at high temperature with an appropriate heating rate to form hollow Fe2O3fibers. The solvent composition, the addition amount of Fe(NO3)3·9H2O and PVP, and the heating rate have important influences on the morphologies of Fe2O3fibers. Morphologies of Fe2O3could be tuned from solid belt to hollow belts and hollow fibers by controlling appropriate preparation conditions. The crystal structure, morphology, surface composition, magnetic and electrochemical properties of the Fe2O3hollow fibers were investigated by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, SQUID magnetometry and cyclic voltammetry, respectively. [ABSTRACT FROM AUTHOR]

Published
2011
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73. Synthesis and luminescence properties of CeF3:Tb3+nanodisks via ultrasound assisted ionic liquid method

Author

LIU, Sanxi, HUI, Yu, ZHU, Ling, FAN, Xizhi, ZOU, Binglin, and CAO, Xueqiang

Abstract

CeF3and CeF3:Tb3+nanocrystals were successfully synthesized by the ultrasound assisted ionic liquid (IL) method at room temperature. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron micrographs (HRTEM) and photoluminescence (PL) spectra were employed to characterize the nanocrystals. The results of XRD indicated that the obtained samples crystallized well with a hexagonal phase crystal structure. SEM and TEM images demonstrated that the obtained CeF3:Tb3+nanocrystals had a discoid shape in the presence of ultrasound and IL, whereas only granular nanoparticles were obtained by magnetic stirring. The possible formation mechanisms of the crystal growth were proposed. The PL spectra of the CeF3:Tb3+nanodisks exhibited a strong green emission when excited at 254 nm. Furthermore, the photoluminescence intensity of CeF3:Tb3+of the discoid particles was largely improved compared with that of the granular nanoparticles.

Published
2014
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74. A new double layer oxidation resistant coating based on Er2SiO5/LaMgAl11O19 deposited on C/SiC composites by atmospheric plasma spraying

Author

Zou, Binglin, Khan, Zuhair S., Fan, Xizhi, Huang, Wenzhi, Gu, Lijian, Wang, Ying, Xu, Jiaying, Tao, Shunyan, Yang, Kuiyue, Ma, Hongmei, and Cao, Xueqiang

Subjects
*PLASMA sheaths, *OXIDATION, *COATING processes, *SILICON oxide, *SILICON carbide, *PLASMA spraying, *METALLIC composites, *CHEMICAL vapor deposition, *ALUMINUM oxide
Abstract

Abstract: A new coating with Er2SiO5 as inner layer and LaMgAl11O19 (LMA) as top layer was designed and deposited on C/SiC composites by atmospheric plasma spraying to improve the oxidation resistance of the substrate at high temperature. Microstructure, oxidation protection and failure mechanism of the Er2SiO5/LMA coating during dynamic thermal cycling (DTC) were investigated. The results showed that a good interfacial bonding between the substrate and the coating was present before and after DTC test. Weight loss for the sample coated on one-side was 4.5% after 11cycles of heating for 85min, and for the uncoated sample was as high as 20.6%. Failure mechanism of the coating resulted from the liquid sintering of the coating and the formation of bubbles between the substrate and the coating. [Copyright &y& Elsevier]

Published
2013
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