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39 results on '"Yang, Chang-Hui"'

5. In Situ Formed Perovskite Nanocrystal Films Toward Efficient Circularly Polarized Electroluminescence.

Author

Yang, Chang‐Hui, Xiao, Hui, Sang, Yu‐Feng, Luo, Jian, Xiao, Shang‐Biao, Xuan, Hong‐Li, Ding, Qing‐Rong, Lin, Wenlie, Xu, Zong‐Xiang, Chen, Zhong‐Ning, and Xu, Liang‐Jin

Subjects
*ELECTROLUMINESCENCE, *PHOSPHINE oxides, *LIGHT emitting diodes, *HYBRID materials, *QUANTUM efficiency, *PEROVSKITE, *PHOTOLUMINESCENCE, *PHOSPHORESCENCE
Abstract

Circularly polarized electroluminescence (CPEL) is an active area of research because of its wide application in 3D displays and anti‐counterfeiting. However, it is not trivial to obtain a high asymmetry factor for highly efficient CPELs. Herein, a highly efficient CPEL is demonstrated with a superior asymmetry factor by using a chiral phosphine‐oxide‐passivated perovskite film as an emitter. An in situ‐formed perovskite nanocrystalline (NC) film is obtained by passivation of the chiral phosphine oxide. The as‐formed film exhibits much‐enhanced photoluminescence compared with the pristine film. More importantly, the NC film exhibits excellent chiral photoluminescence with a luminescence dissymmetry factor glum as high as 5.6 × 10−3. Electrically driven light‐emitting diodes based on the NC film exhibited superior device performance with a maximum brightness of 18,783 cd m−2 and a peak external quantum efficiency of 3.6%. More encouragingly, an unprecedented electroluminescence asymmetry factor gEL of up to 0.18 is achieved because of the chiral lattice distortion of the perovskite, which is the state‐of‐the‐art among hybrid materials. [ABSTRACT FROM AUTHOR]

Published
2024
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10. Effect of graphene oxide on the mechanical properties and the formation of layered double hydroxides (LDHs) in alkali-activated slag cement

Author

Zhu, Xiao Hong, Kang, Xiao Juan, Yang, Kai, and Yang, Chang Hui

Subjects
Graphene -- Mechanical properties -- Analysis, Graphite -- Mechanical properties -- Analysis, Hydroxides -- Mechanical properties -- Analysis, Cements (Building materials) -- Mechanical properties -- Analysis, Business, Construction and materials industries
Abstract

Due to its high aspect ratio and outstanding tensile strength, graphene oxide (GO) can dramatically reduce the brittleness of cement-based materials. In this paper, GO nanosheets were successfully synthesised using the modified Hummers' method. Effects of the GO on the fluidity, mechanical properties of alkali-activated slag (AAS) mortars and the microstructure of the AAS pastes were studied. It is found that addition of the GO caused a significant reduction in fluidity and a slight decrease in the compressive strength of the hardened mortars. However, the GO improved the flexural strengths by 20% with a dosage of 0.01 wt% after 7 days. Large-scale layered double hydroxides (LDHs) were observed using SEM, the compositions of which were identified and EDS and XRD. A possible mechanism of the formation of LDHs in the GO-AAS system is proposed. Due to the [Mg.sup.2+]/[Al.sup.3+] decomposed from the slag and the Al [(OH).sup.-.sub.4] formed in the high pH condition in the GO-AAS system, the reaction pathway of LDHs can be regarded as a[Mg.sup.2+] + Al[(OH).sup.-.sub.4] + (2a--2)O[H.sup.-] + x[H.sub.2]O + [A.sup.-] = [Mg.sub.a]Al[(OH).sub.2+ 2a] A x x[H.sub.2]O(s) This research provides a further understanding of the effect of graphene oxide which has a potential application of GO in AASC. Keywords: GO nanosheets Alkali-activated slag cement Microstructure LDHs Reaction pathway, 1. Introduction Alkali-activated slag cement (AAS), which can be a clinker-free binder, provides an eco-friendly alternative to conventional Portland cement [1]. The use of granulated ground blast furnace slag (GGBFS) [...]

Published
2017
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16. Alkali aggregate reaction in alkali slag cement mortars

Author

Ding Qing-jun, Chen You-zhi, Pu Xin-cheng, and Yang Chang-hui

Subjects
Cement, Materials science, Aggregate (composite), Slag, Alkali metal, law.invention, Portland cement, Chemical engineering, law, visual_art, visual_art.visual_art_medium, General Materials Science, Mortar, Composite material, Mass fraction, Alkali–aggregate reaction
Abstract

By means of “Mortar Bar Method”, the ratio of cement to aggregate was kept as a constant 1∶2,25 the water-cement ratio of the mixture was 0.40, and six prism specimens were prepared for each batch of mixing proportions with dimensions of 10×10×60mm3 at 38±2°C and RH≧95%, the influences of content and particle size of active aggregate, sort and content of alkali component and type of slag on the expansion ratios of alkali-activated slag cement (ASC) mortars due to alkali aggregate reaction (AAR) were studied. According to atomic absorption spectrometry, the amount of free alkali was measured in ASC mortars at 90d. The results show above factors affect AAR remarkably, but no dangerous AAR will occur in ASC system when the amount of active aggregate is below 15% and the mass fraction of alkali is not more than 5% (Na2O). Alkali participated in reaction as an independent component, and some hydrates containing alkali cations were produced, free alkalis in ASC system can be reduced enormously. Moreover, slag is an effective inhibitor, the possibility of generating dangerous AAR in ASC system is much lower at same conditions than that in ordinary Portland cement system.

Published
2002

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