ABSTRACT
Magnesium (Mg)-matrix composites have excellent damping and electromagnetic shielding properties. However, the mismatch between their strength and toughness limits their wide application. The aim of this work is to overcome the strength-toughness mismatch by constructing micro- and nanostructures while maintaining the good functional properties of Mg-matrix composites. Electrophoretic deposition (EPD) was used to spread carbon nanotubes (CNTs) out evenly on a Mg foil matrix. After spark plasma sintering (SPS), the grain organisation was refined, and the interlayer bonding was strengthened by hot rolling deformation. Finally, the microstructure, mechanical properties, damping properties, and electromagnetic shielding properties of the composites were analysed. Compared with the pure Mg laminates, the tensile strength and elongation of the CNT/Mg laminates were increased by 6.4% and 108.4%, respectively, with the significant improvement in toughness resulting from the increase in energy required for crack propagation due to the laminate structure. When the total rolling deflection reaches 80%, the interlayer bond strength of the material is significantly increased, the grain is further refined, and the strength and elongation of the composite material reaches the optimum, with the tensile strength reaching 241.70 MPa and the elongation reaching 6.90%. The interlayer interface and grain refinement also affected the damping Mg and electromagnetic shielding effect of the composites. This work provides an experimental idea for the preparation of high-performance structure-function integrated Mg-based materials.
ABSTRACT
The objective of this study is to prepare CNT/AlSi10Mg composites using mechanical ball milling combined with SPS. The study investigates the influence of ball-milling time and CNT content on the mechanical and corrosion resistance of the composite. This is performed to address the challenge of CNTs dispersion and to understand how CNTs impact the mechanical and corrosion resistance of the composites. The morphology of the composites was characterized using scanning electron microscopy (SEM) transmission electron microscopy (TEM) and Raman spectroscopy, and the mechanics and corrosion resistance of the composite materials were tested. The results demonstrate that the uniform dispersion of CNTs can significantly enhance both the mechanical properties and corrosion resistance of the material. Specifically, when the ball-milling time was 8 h, CNTs were uniformly dispersed in the Al matrix. The CNT/AlSi10Mg composite shows the best interfacial bonding when the mass fraction of CNTs is 0.8 wt.%, with a tensile strength of -256 MPa. This is 69% higher than the original matrix material without the addition of CNTs. Moreover, the composite exhibited the best corrosion resistance.
ABSTRACT
In order to effectively solve the problem of strength and ductility mismatch of magnesium (Mg) matrix composites, carbon nanotubes (CNTs) are added as reinforcement. However, it is difficult to uniformly disperse CNTs in a metal matrix to form composites. In this paper, electrophoretic deposition (EPD) was used to obtain layered units, and then the CNTs/Mg layered units were sintered by spark plasma sintering to synthesize layered CNTs/Mg composites. The deposition morphology of the layered units obtained by EPD and the microstructure, damping properties, and mechanical properties of the composite material were analyzed. The results show that the strength and ductility of the composite sample sintered at 590 °C were improved compared with the layered pure Mg and the composite sample sintered at 600 °C. Compared with pure Mg, the composites rolled by 40% had a much higher strength but no significant decrease in ductility. The damping properties of the CNTs/Mg composites were tested. The damping-test-temperature curve (tanδ~T) rose gradually with increasing temperature in the range of room temperature to 350 °C, and two internal friction peaks appeared. The damping properties of the tested composites at room temperature decreased with increasing frequency. The layered structure of the CNTs/Mg had ultra-high strengthening efficiency and maintained its ductility. The layered units prepared by EPD can uniformly disperse the CNTs in the composites.
ABSTRACT
The widely studied Pt/C catalyst for direct methanol fuel cells (DMFCs) suffers severe carbon corrosion under operation, which undermines the catalytic activity and durability. It is of great importance to develop a carbon-free support with co-catalytic functionality for improving both the activity and durability of Pt-based catalysts. The direct loading of Pt on the smooth surface of oxides may be difficult. Herein, the Cu assisted loading of Pt on CeO2 is developed. Cu pre-coated CeO2 was facilely synthesized and Pt was electrochemically deposited to fabricate the carbon-free PtCu/CeO2 catalyst. The PtCu/CeO2 catalyst has a mass activity up to 1.84 and 1.57 times higher than Pt/C towards methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR), respectively. Better durability is also confirmed by chronoamperometry and accelerated degradation tests. The strategy in this work would be greatly helpful for developing an efficient carbon-free support of Pt-based catalysts for applications in DMFCs.
