Influencing the Size and Shape of High-Energy Ball Milled Particle Reinforced Aluminum Alloy Powder

Effect of Milling Time and Reinforcement Volume Fraction on Microstructure and Mechanical Properties of SiCp-Reinforced AA2017 Composite Powder Produced by High-Energy Ball Milling

The influence of milling time and volume fraction of reinforcement on the morphology, microstructure, and mechanical behaviors of SiCp-reinforced AA2017 composite powder produced by high-energy ball milling (HEBM) was investigated. AA2017 + SiCp composite powder with different amounts of SiC particles (5, 10, and 15 vol%) was successfully prepared from gas-atomized AA2017 aluminum alloy powder with a particle size of <100 μm and silicon carbide (SiC) powder particles with an average particle size of <1 μm. An optical microscope (OM), X-ray diffraction (XRD), and scanning electron microscope (SEM) were utilized to characterize the microstructure of the milled composite powder at different milling periods. The results indicated that the SiC particles were homogeneously distributed in the AA2017 matrix after 5 h of HEBM time. The morphology of the particles transformed from a laminar to a nearly spherical shape, and the size of the milled powder particles reduced with increasing the content of SiC particles. The XRD analysis was carried out to characterize the phase constituents, crystallite size, and lattice strain of the composite powders at different milling periods. It was found that with increasing milling time and SiC volume fraction, the crystallite size of the aluminum alloy matrix decreased while the lattice strain increased. The average crystallite sizes were reduced from >300 nm to 68 nm, 64 nm, and 64 nm after 5 h of milling, corresponding to SiC contents of 5, 10, and 15 vol%, respectively. As a result, the lattice strain increased from 0.15% to 0.5%, which is due to significant plastic deformation during the ball milling process. XRD results showed a rapid decrease in crystallite size during the early milling phase, and the minimum grain size was achieved at a higher volume fraction of SiC particles. Microhardness tests revealed that the milling time has a greater influence on the hardness than the amount of SiC reinforcements. Therefore, the composite powder milled for 5 h showed an average microhardness three times higher than that of the unmilled powder particles.

Weak CO binding sites induced by Cu-Ag interfaces promote CO electroreduction to multi-carbon liquid products

Electrochemical reduction of carbon monoxide to high-value multi-carbon (C₂₊) products offers an appealing route to store sustainable energy and make use of the chief greenhouse gas leading to climate change, i.e., CO₂. Among potential products, C₂₊ liquid products such as ethanol are of particular interest owing to their high energy density and industrial relevance. In this work, we demonstrate that Ag-modified oxide-derive Cu catalysts prepared via high-energy ball milling exhibit near 80% Faradaic efficiencies for C₂₊ liquid products at commercially relevant current densities (>100 mA cm^-2) in the CO electroreduction in a microfluidic flow cell. Such performance is retained in an over 100-hour electrolysis in a 100 cm² membrane electrode assembly (MEA) electrolyzer. A method based on surface-enhanced infrared absorption spectroscopy is developed to characterize the CO binding strength on the catalyst surface. The lower C and O affinities of the Cu-Ag interfacial sites in the prepared catalysts are proposed to be responsible for the enhanced selectivity for C₂₊ oxygenates, which is the experimental verification of recent computational predictions.