Weibang Lyu

The thermal stability of bionic superhydrophobic drop-jumping copper nanostructure surfaces is key to ensuring their safe use in the chip-cooling field. However, there is no report about the allowable heating temperature limit of such functional surfaces, and the condensate mode and wettability evolution vary with heating temperature (T), which are still unclear. Here, we demonstrate for the first time that both the macroscopic drop nonsticky superhydrophobicity and condensate microdrop self-jumping removal functions of the superhydrophobic copper nanocone array structure surface can remain stable as long as T is no more than 150 °C, which is far higher than the allowable temperature limit (45 °C) of 5G mobile phone chips and sufficient to develop matchable low-temperature (e.g., 100-140 °C) soldering technologies. As T rises up to 175, 200, and 300 °C, the sample surface presents sticky superhydrophobicity, ordinary hydrophobicity, and superhydrophilicity for macroscopic water drops, accompanied by the progressive transition of condensate dynamics toward the microdrop coalescence/pinning, dropwise condensation, and filmwise condensation. Decoupling thermal stability analyses into the morphology change of copper nanocones and the dissociation degrees of thiol bonds at different temperatures indicates that the thermal stability of superhydrophobic copper nanostructure depends on the latter rather than the former. Copper nanocones and their bonded thiol can remain stable as T ≤ 500 °C and T ≤ 150 °C, respectively. Higher heating temperature results in the gradual dissociation of thiol bonds until complete decomposition. Such temperature-dependent performance stability and instability can be rationalized by combined experiments and analyses. This work not only helps deepen the thermal stability understanding of superhydrophobic metal nanostructures but also identifies the safe use temperature limit of octadecanethiol-modifed copper nanostructures, which opens a door for developing matchable low-temperature packaging technologies and next-generation high-performance ultrathin copper vapor chambers integrated with the superhydrophobic drop-jumping function in the near future.

Spinning fibers from carbon nanotube (CNT)/superacid dispersions has emerged as a promising strategy for industrial‐scale production of high‐performance CNT fibers (CNTFs). The oxygen content and types of functional groups on CNT surfaces significantly influence dispersion, assembly processes, and fiber properties. In this study, Tuball‐SWCNTs were purified and oxidized at varying levels. The dispersion behavior of CNTs with different oxidation levels in chlorosulfonic acid was systematically observed, and the mechanical properties of fibers spun from these dispersions were compared. By adjusting the dispersion concentration, highly oriented CNTFs were produced with a specific strength of 1.03 N/tex, a tensile strength of 1.59 GPa, and an electrical conductivity of 3.58 MS/m. Further investigations indicated that oxygen‐containing functional groups decrease the coagulation rate, increasing the maximum draw ratio during spinning and improving CNT alignment in the fibers. Molecular dynamics simulations demonstrated that these functional groups (−OH, ‐COOH) enhance load transfer between CNTs through hydrogen bonding. This specific strength is the highest achieved using Tuball‐SWCNTs for superacid‐spun fibers, surpassing previous works due to the oxidation‐controlled coagulation rate, enhanced fiber orientation, and improved load transfer via hydrogen bonding. This study provides insights for designing and optimizing high‐performance CNTFs.

Multi-scale “rigid-soft” material coating has been an effective strategy for enhancing the interfacial shear strength (IFSS) of carbon fibers (CFs), which is one of the key themes in composite research. In this study, a soft material, chitosan (CS), and a rigid material, carbon nanotubes (CNTs), were sequentially grafted onto the CFs surface by a two-step amination reaction. The construction of the “rigid-soft” structure significantly increased the roughness and activity of the CFs surface, which improved the mechanical interlocking and chemical bonding between the CFs and resin. The interfacial shear strength (IFSS) of the CS- and CNT-modified CFs composites increased by 186.9% to 123.65 MPa compared to the desized fibers. In addition, the tensile strength of the modified CFs was also enhanced by 26.79% after coating with CS and CNTs. This strategy of establishing a “rigid-soft” gradient modulus interfacial layer with simple and non-destructive operation provides a valuable reference for obtaining high-performance CFs composites.

The self-assembly of cyclodextrins (CDs) with various guest polymers and small molecules has been intensively investigated for several decades, and it has still increasingly attracted wide attention to construct well-defined microstructures for the uses in biomedicine, sensors, environments, and nanorobotics. While most of the self-assembly of CDs involves the presence of guests, we recently discovered that α-CDs and γ-CDs could be self-assembled between themselves without the incorporation of any guests simply by elevating the temperature of their N,N-dimethylformamide (DMF) solution. In this work, we further found that α-CDs could self-assemble or reorganize in DMF into hexagonal rods simply by directly drying out the α-CD DMF solution. The α-CDs were self-assembled in the guest-free solution triggered by solvent evaporation. The X-ray powder diffraction results confirmed that they possessed a columnar structure, combined with the absence of guests in the strategy, and the cavities of CDs were not filled with guest molecules, but some water molecules may exist. The rods could be formed in various concentrations from 0.001 to 0.08 g/mL with drying temperatures ranging from 80 to 140 °C. The finding of this work shows the exceptional possibility of CDs to form well-defined microstructures without the engagement of guest molecules.

The active dispersant Py-PEI remarkably enhanced the dispersing stability of CNTs in water and the mechanical performance of BP/epoxy composites.