Dealloyed porous gold anchored by: In situ generated graphene sheets as high activity catalyst for methanol electro-oxidation reaction

A novel one-step method to prepare the nanocomposites of reduced graphene oxide (RGO)/nanoporous gold (NPG) is realized by chemically dealloying an Al2Au precursor. The RGO nanosheets anchored on the surface of NPG have a cicada wing like shape and act as both conductive agent and buffer layer to improve the catalytic ability of NPG for methanol electro-oxidation reaction (MOR). This improvement can also be ascribed to the microstructure change of NPG in dealloying with RGO. This work inspires a facile and economic method to prepare the NPG based catalyst for MOR

Energy absorption of variable stiffness composite thin-walled tubes on axial impacting

In order to realize the engineering application of automated fiber placement for composite laminates, a method of the variable angle fiber placement was proposed to design the tube structures of variable stiffness composites based on the quadratic Bezier curve. The axial crushing responses were simulated to investigate the energy absorption characteristics of composite tubes. The results showed that the method of the variable angle fiber placement contributed to the improvement of the energy absorption effects. The maximum crushing force efficiency of the variable stiffness composite thin-walled tubes designed by the method was 49.04% which was 106.48% higher than the constant stiffness composite tube. The results could be helpful for the process of automated fiber placement and the design of the energy absorption for composite thin-walled structures

Enhancing Corrosion and Wear Resistance of AA6061 by Friction Stir Processing with Fe78Si9B13 Glass Particles

The AA6061-T6 aluminum alloy samples including annealed Fe78Si9B13 particles were prepared by friction stir processing (FSP) and investigated by various techniques. The Fe78Si9B13-reinforced particles are uniformly dispersed in the aluminum alloy matrix. The XRD results indicated that the lattice parameter of α-Al increases and the preferred orientation factors F of (200) plane of α-Al reduces after friction stir processing. The coefficient of thermal expansion (CTE) for FSP samples increases at first with the temperature but then decreases as the temperature further increased, which can be explained by the dissolving of Mg and Si from β phase and Fe78Si9B13 particles. The corrosion and wear resistance of FSP samples have been improved compared with that of base metal, which can be attributed to the reduction of grain size and the CTE mismatch between the base metal and reinforced particles by FSP, and the lubrication effect of Fe78Si9B13 particles also plays a role in improving wear resistance. In particular, the FSP sample with reinforced particles in amorphous state exhibited superior corrosion and wear resistance due to the unique metastable structure

Micromorphology and Phase Composition Manipulation of Nanoporous Gold with High Methanol Electro-oxidation Catalytic Activity through Adding a Magnetic Field in the Dealloying Process

By dealloying a rapidly solidified (RS) Al₂Au alloy, nanoporous gold (np-Au) samples with a three-dimensional (3D) interpenetrating ligament-channel structure are fabricated in 0, 0.02, and 0.2 T magnetic fields. Adding magnetic field leads to intermediate AlAu phase formation, decreases the dealloying rate, and triggers the formation of fine nanocrystals and amorphous phase in the np-Au ligaments. The np-Au samples dealloyed in 0, 0.02, and 0.2 T for 24 h (DA0, DA1, and DA2) appear in maze-like, honeycomb-like, and soda cracker-like micromorphologies, respectively. The DA1 sample possesses the smallest lattice constant <i>a</i>₀ and highest preferred orientation factor <i>F</i>₍₁₁₁₎ of the (111) face. The parameters like surface coverage of the redox species Γ*, charge-transfer rate constant <i>k</i>_s, exchange current density <i>j</i>₀, corrosion potential <i>E</i>_corr, and charge transfer resistance <i>R</i>_ct indicate that the methanol electro-oxidation activity of the three samples is in this order: DA1 > DA2 > DA0, which can be ascribed to crystallographic, thermodynamic, and defective reasons. This work supplies a new method to enhance the methanol catalytic activity of np-Au

High Activity Methanol/H₂O₂ Catalyst of Nanoporous Gold from Al–Au Ribbon Precursors with Various Circumferential Speeds

We have prepared nanoporous gold (np-Au) with a three-dimensional (3D) bicontinuous interpenetrating ligament-channel structure by dealloying the melt spun Al₂Au ribbon precursors with three different circumferential speeds (<i>S</i>_c). With increasing <i>S</i>_c, the lattice constant (<i>a</i>₀) of precursors decreases. After the dealloying procedure, the np-Au samples have an increasing <i>a</i>₀ and a decreasing pore size with increasing <i>S</i>_c. There exists the heredity of the preferred orientation factors (<i>F</i>) between precursors and np-Au samples. The cyclic voltammetry (CV) curves of methanol electro-oxidation reaction (MOR) on np-Au samples are related to their <i>F</i> and show a higher activity with a higher <i>S</i>_c. In addition, np-Au with a lower pore size exhibits a higher sensitivity for the concentration of H₂O₂ in phosphate buffered solutions (PBS), which reaches 73.4 μA mM^–1 cm^–2 with <i>S</i>_c = 18.3 m/s. These results suggest that we can change the pore size of the dealloyed np-Au by adjusting the <i>S</i>_c of the precursors, and then enhance the catalytic activity of np-Au