Advanced Engineering Materials最新文献

Co-Packaged Optics

In article number 2402095, Drew Weninger, Samuel Serna, and co-workers present a co-packaged optics system with an electrical chip (black, center) surrounded by 8 silicon photonic chips. Chips are bonded using an automated pick-and-place tool, shown placing the final chip into position. The automation is enabled by a novel optical chip-to-chip coupler (green callout).

Reactive Al/Ni Multilayers

The image depicts a reactive multilayer system (RMS) envisioned for future chip-bonding applications. Individual layers of aluminum (Al) and nickel (Ni) are activated by a brief energy pulse, initiating a diffusion-driven reaction that reaches peak temperatures up to 1500 °C. In the course of this self-sustaining high-temperature synthesis, the two face-centered cubic metals transform into a body-centered cubic AlNi B2 phase. Further details can be found in article number 2302271 by Sebastian Matthes and co-workers.

Sputtered AlNi Multilayers

In article number 2302215, Juan Jesús Jiménez and co-workers show that preparation methods have crucial influence on transmission electron microscopy results when investigating the intermixing between Al and Ni in reactive multilayers. The comparison of three lamella preparation methods shows that Xe-based FIB leads to low contamination, although Ga-FIB is a good alternative. This outcome presents an important aspect for the investigation of self-sustaining reactions on nanostructures and rough surfaces.

Composite panels are made of a core and skins that are typically bonded with adhesive. Traditional adhesive bonding is time-consuming and requires precision, often leading to debonding under varied loading conditions. Additionally, thermal expansion differences between the core, skin, and adhesive cause residual stresses, compromising performance. This research develops a cost-effective method for creating integrated sandwich panels, addressing the effectiveness of such unification under low-velocity impact loading. Using a standard dual-nozzle fused deposition modeling 3D printer with minimal modifications, continuous fibers embedded in a thermoplastic polymer for the skin and a thermoplastic polymer for the core are simultaneously deposited, ensuring material consistency between the core and matrix of the skins, leading to an integrated panel. Integrated samples are compared to pure (fiberless) and adhesive-bonded samples under an 18 J low-velocity impact test. The integrated samples show significant improvements, with maximum impactor acceleration (279.7 m s⁻²) and force per unit mass (83 283 N kg⁻¹), surpassing adhesive-bonded and pure samples by 35 and 110%, respectively. Additionally, integrated samples show significantly less damage, with dent diameters (9.77 mm) and dent depths (1.52 mm) considerably lower. These findings highlight the benefits of this approach in enhancing impact resistance, reducing damage, and improving energy absorption in composite sandwich structures.

This study presents the first synthesis and characterization of monolithic hybrid preceramic aerogels using distinct drying techniques: ambient pressure (ambigels) and CO₂ supercritical drying. Polymeric ambi/aerogels, derived from polyhydromethlysiloxane (PHMS) and divinylbenzene (DVB), are processed at 200 °C, while hybrid ceramic-polymer (ceramer) is produced through pyrolysis at 600 °C. Despite variations in drying methods, polymer and ceramer ambi/aerogels exhibit comparable microstructural characteristics, bulk density, pore size and volume, and specific surface area (542–841 m² g⁻¹). Polymeric and ceramer ambigel with 90 vol% total porosity yield a compressive strength, reaching 2.5 MPa, demonstrating a low thermal conductivity of 0.046 W m⁻¹ K⁻¹. Sorption tests are conducted using oil and organic solvents in aqueous media to benefit their high hydrophobicity (112° < θ < 142°). Aerogels exhibit high sorption capacities: 13.17 g g⁻¹ for sesame oil, 11.74 g g⁻¹ for toluene, and 9.19 g g⁻¹ for n-hexane. The sorption rate for the oil is nearly 10 times slower than that for toluene and n-hexane. Regarding regeneration and reusability, polymer and ceramer aerogels show consistent sorption properties cycles tested for n-hexane and toluene.

Precision Macroporous Monoliths

In article number 2401363, André R. Studart, Iacopo Mattich, and Alessandro Ofner fabricate centimeter-scale macroporous materials with precisely controlled pore sizes from monodisperse droplets made by high-throughput microfluidics. Macroporosity is created by gravity-induced self-assembly of droplets, followed by polymerization of the continuous phase. Because it combines scalability, pore size control, and tunable chemistry, this microfluidic platform offers a powerful self-assembly approach to produce macroporous materials for catalysis, electrochemistry and separation processes.

Liquid-Crystal Elastomer Lattices

In article number 2401796, Devin J. Roach and co-workers use direct ink write 3D printing to fabricate aligned, monodomain liquid-crystal elastomer (LCE) lattice structures for broad strain-rate mechanical damping. It is shown that these structures can dissipate strain energy in quasi-static environments, comparable to traditional elastomeric lattices, and provide improved damping under high strain-rate drop testing due to LCE soft elasticity. Art by the team of INMYWORK Studio (https://inmywork.com).

The powder metallurgy route of high-energy ball milling followed by sintering is a common method used to fabricate nanocrystalline (NC) metals. However, the poor thermal stability of NC metals limits the use of high temperatures during sintering, which can result in insufficient densification. In order to achieve a higher relative density at low sintering temperatures, phase transformation-induced volume expansion during sintering is taken advantage of. To prove this hypothesis, NC Fe–5 at.% Zr alloy is sintered at a temperature above A3 (1073 K), which is then decreased below A1 (873 K) to introduce volume expansion caused by phase transformation from austenite to ferrite. For comparison, it is also sintered at a constant temperature above A3 (1073 K). Results show that the proposed strategy can not only enhance the relative density of as-sintered NC Fe–5 at.% Zr alloy, but also ensure a relatively smaller grain size. This study is beneficial for the fabrication of high-performance NC metals.

Dielectric Elastomer Actuators

In article number 2401306, Amine Benouhiba and co-workers present a high-performance tubular dielectric elastomer pump optimized for heart assist applications. Operating at pressures of 15, 70, and 120 mmHg, it achieves a flow rate of 6.5 L min^–1 and a pressure head of 27.5 mmHg, underscoring its potential to enhance fluid circulation and support cardiovascular function in medical applications.