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319 results on '"Yao, Dongxu"'

16. Joining of silicon nitride ceramic to oxygen‐free copper using Ag–Cu–TiH2 filler.

Author

Tang, Liangliang, Yao, Dongxu, Xia, Yongfeng, Zhao, Jun, Zhu, Ming, and Zeng, Yu‐Ping

Subjects
*COPPER, *INTERFACIAL reactions, *SILICON nitride, *FILLER metal, *CERAMICS, *BRAZING, *CRYSTAL grain boundaries
Abstract

Complex liquid–solid reactions occur during brazing. A deep understanding of brazing liquid evolution is therefore of important concern for the bonding between filler and substrates. The joining of gas‐pressure‐sintered silicon nitride (Si3N4) ceramic to oxygen‐free copper (OFC) foil was prepared using Ag–Cu–TiH2 filler at 875°C for 0.5 h. The effect of the Ag:Cu ratio on the interfacial microstructure and peeling strength of the joints was analyzed. The reaction of brazing liquid with Si3N4 ceramic includes reactions with both the β‐Si3N4 and the grain boundary phases (Y–Si–Mg–O–N). The resulting interfacial reaction products include TiN, Ti5Si3, and potential Cu3Ti3O. Based on the phase composition and three‐dimensional morphology of the interfacial reaction products in the Si3N4 ceramic/OFC foil joints, a model for the evolution of the brazing liquid as the reaction proceeds was proposed. Peeling test results indicated that the peeling strength of the joints rises unilaterally with the increase of the Ag:Cu ratio in the filler until reaching the peak value of 24.3 N/mm at the maximum Ag:Cu ratio of 90:10. The mechanisms of the joint peeling fracture were discussed in detail. [ABSTRACT FROM AUTHOR]

Published
2024
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17. Dynamic response of groundwater to rainfall events and sea tides in coral island.

Author

Yao, Dongxu, Yang, Lihu, and Song, Xianfang

Subjects
RAINFALL, CORAL reefs & islands, MULTIPLE regression analysis, WATER levels, ELECTRIC conductivity, RAINSTORMS, WATER table
Abstract

Rainfall and sea tides significantly affect the coastal groundwater. The effect of rainfall events and sea tides on groundwater is not fully understood. In this study, groundwater level and electrical conductivity (EC) were simultaneously measured in three monitoring wells to evaluate the behaviour of freshwater in the uplifted atoll island of Zhaoshu, China. We used the water level sensor monitoring the position and variability of freshwater in the island. In the monitoring period, 86 rainfall events (cumulative rainfall above 1 mm) were identified. The fresh groundwater periodically fluctuates with phase lags every 1–2 h following sea tides. The intermittent rainfall increases the volume of fresh groundwater, while groundwater fluctuation is controlled by tides. Multiple regression analysis and cross‐correlation analysis were used to analyse the response relationship of groundwater to rainfall and tides. Variation in the groundwater level lags the EC as the temporal fluctuation of the sea tides. Only in case of severe rainstorm (cumulative precipitation of an event above 300 mm), the contribution of rainfall on groundwater level fluctuation is greater than that of sea tide. Four response modes (RRR, RFF, RFR, RRF) decomposition of groundwater have been defined according to the tidal stage and threshold (70.3–301.1 mm) of rainfall. The tidal‐induced groundwater effect (TGE) is stronger than the rainfall‐induced groundwater effect (RGE) but it is the opposite in the third and fourth modes. These results and mechanisms could be applied to other atoll islands, for our understanding of rainfall infiltration processes with tidal effect, and could be instrumental in estimating groundwater resources. [ABSTRACT FROM AUTHOR]

Published
2024
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46. A Facile Molten Salt Method for Diverse TiC/C Hybrid as Effective Polysulfide Confinement toward Stable Lithium–Sulfur Batteries.

Author

Zhou, Peilong, Geng, Xinwei, Yao, Dongxu, Xia, Yongfeng, and Zeng, Yu‐Ping

Subjects
POLYSULFIDES, LITHIUM sulfur batteries, FUSED salts, CARBON-based materials, POROUS materials, TITANIUM carbide
Abstract

Traditional carbon materials suffer from weak adsorption of lithium polysulfides and excessive consumption of electrolyte. A simple and feasible molten salt method is applied for constructing an active nanocrystalline TiC shell on the surface of porous carbon. The highly active TiC nanoshells endow the core–shell composite with efficient chemical–physical synergistic adsorption, which can effectively confine and convert polysulfides, thereby improving the electrochemical performance of lithium–sulfur batteries. The lithium–sulfur batteries assembled with modified separator deliver a high initial discharge specific capacity of 1396 mAh g−1 at a discharge rate of 0.5 C and a high capacity retention of 747.1 mAh g−1 after 500 cycles, with a high coulombic efficiency of 98% during cycling. Besides, this molten salt method can be applied to modify the porous carbon materials of various composite sulfur cathodes such as graphene, carbon nanotubes, and 3D nonwoven carbon fabrics. [ABSTRACT FROM AUTHOR]

Published
2024
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