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18. The influence of SiC–Al2O3 reinforcements on the deformation and fracture mechanism of thixomolded Mg-based composite.

Author

Gu, Lidong, Shang, Xiaoqing, Wang, Jie, Zhao, Zhen, Zeng, Xiaoqin, and Ding, Wenjiang

Subjects
*DEFORMATIONS (Mechanics), *DIGITAL image correlation, *ELASTIC modulus, *SCANNING electron microscopes, *FINITE element method, *HYPEREUTECTIC alloys, *MAGNESIUM alloys
Abstract

The thixomolding technology offers distinct advantages for producing magnesium matrix composites with intricate geometries. This study explores the effects of incorporating hybrid SiC–Al2O3 particles on the microstructure, deformation, fracture, and mechanical properties of a thixomolded Mg–10Zn alloy. The composite exhibits a homogeneous distribution of Al2O3 and SiC particles within the matrix. The addition of SiC–Al2O3 reinforcements helps reduce the content of primary α -Mg solid and refine the microstructure. The composite demonstrates a yield strength of 186 MPa, an elastic modulus of 48.6 GPa, and a respectable elongation of 6.8%. The digital image correlation measurement was performed at the sample scale, unveiling overall deformation characteristics. Crystal plasticity finite element method was employed for high-fidelity microstructure, showcasing mesoscale deformation feature such as the deformation mechanism of grains adjacent to reinforcements. It was found that SiC–Al2O3 particles prevent the formation of large shear band, benefiting the ductility of the material. The post-mortem analysis using scanning electron microscope near the fracture position reveals micro-cracks inside the SiC particles. Notably, the SiC/Mg interface shows no signs of cracking, while some Al2O3/Mg interfaces are separated. Reinforcement cracking is correlated to the stress it withstands, and the mesoscale deformation analysis reveals that the reinforcement stress is increased when non-basal slip in grains adjacent to the reinforcement becomes difficult to be activated. This work serves as an example for developing Mg matrix composites through the thixomolding process. The findings of this study provide valuable insights for the design of high-performance thixomolded Mg-based composites [ABSTRACT FROM AUTHOR]

Published
2024
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27. Heterostructure construction of covalent organic frameworks/Ti3C2-MXene for high-efficiency electrocatalytic CO2 reduction.

Author

Zhou, Liyuan, Tian, Qingyong, Shang, Xiaoqing, Zhao, Yanming, Yao, Weijing, Liu, Hongpo, and Xu, Qun

Subjects
ELECTROCATALYSIS, ION transport (Biology), CHARGE exchange, FAST ions, SURFACE area, HETEROJUNCTIONS
Abstract

Covalent organic frameworks (COFs), as typical organic functional materials, have shown promising potential for application in photo/electrocatalysis, especially in the electrocatalytic CO2 reduction reaction (CO2RR). COFs can ensure effective CO2 adsorption and rapid mass transfer by virtue of controllable active sites and a large specific surface area. However, the inefficient interlayer conductivity of most COFs leads to a low electron transfer rate that restricts their practical applications. In this work, porphyrin-based covalent organic framework nanosheets (Por-COF) were vertically grown on the modified MXene surface for efficient electrocatalytic CO2RR. The large exposed MXene surface serves as a carrier "bridge" for dispersed COFs, which can endow heterojunctions with more active sites and fast ion transport channels. The optimal sample can exhibit superior efficient CO2RR performance, in which the faradaic efficiency of the CO2-to-CO conversion was 97.28% at −0.6 V vs. RHE, and the bias current density was −9.33 mA cm−2 at −1.0 V vs. RHE. [ABSTRACT FROM AUTHOR]

Published
2024
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41. Causes and Control Technology of Slurry Overflow in an Ammonia Desulfurization Tower

Author

Shang Xiaoqing, Liu Zhe, Cheng Zhiye, Chen Xufei, and Chen Xiaodong

Subjects
chemistry.chemical_classification, Ammonium sulfate, Flue gas, Materials science, business.industry, General Chemical Engineering, Salt (chemistry), General Chemistry, Article, Flue-gas desulfurization, Chemistry, chemistry.chemical_compound, Ammonia, Chemical engineering, chemistry, Slurry, Coal, Ammonium, business, QD1-999
Abstract

In the flue gas ammonia desulfurization process of the coal chemical industry, ammonium sulfate slurry in the desulfurization tower often foams and overflows, which wastes resources and pollutes the environment. The solution to this problem remains largely unknown. This paper aims to reveal the causes of foaming by analyzing foam composition, ammonia desulfurization process raw material source, and characteristics of the flue gas source of the coal chemical industries. It is seen that the organic carboxylate ammonium salt surfactant in the slurry was the main cause of ammonium sulfate slurry foaming. Moreover, due to ammonium sulfate crystals and ash in foam forming a skeleton to support the foaming structure, the foam was not easy to break. More importantly, an appropriate defoaming agent was screened and optimized by an ammonia desulfurization tower simulated device in the laboratory. The YLZ-3 compound defoaming agent, with the optimal defoaming efficiency, was obtained by combining a polyether siloxane copolymer, n-octyl alcohol, fumed silica, and deionized water. It had a good temperature stability and little influence on the ammonium sulfate slurry drying time. However, defoaming agent addition could affect the ammonium sulfate crystal form. The foam overflowing could be controlled by spraying the defoaming agent from the top of the tower. Thus, the problem of bubbling overflow of the ammonia desulfurization tower could be resolved very well.

Published
2021

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