Hydrogen embrittlement remains a critical bottleneck limiting the reliability of structural materials in hydrogen energy systems, thus fueling the imperative demand for high-performance hydrogen permeation barriers (HPBs). Ceramic nano-multilayer coatings offer unique advantages over single-layer counterparts by leveraging interface-driven hydrogen trapping and blocking. Herein, Al2O3/TiO2 nano-multilayer coatings with tailorable period thicknesses (2–50 nm) were fabricated on T91 steel via atomic layer deposition. Their microstructure, electrochemical behavior, and hydrogen permeation resistance were systematically characterized. The results demonstrate that the as-prepared coatings exhibit a dense, amorphous microstructure, accompanied by superior corrosion resistance compared to single-layer Al2O3, TiO2, and the bare T91 substrate. Notably, a non-linear correlation between hydrogen permeation resistance and period thickness was unveiled, a discovery that fills a critical knowledge gap in the field of HPBs design. Specifically, hydrogen permeation resistance was found to rise with increasing interface number up to a critical value, beyond which insufficient spatial isolation of hydrogen-induced defects gives rise to interconnected diffusion pathways and degraded barrier efficiency. The optimal Al2O3/TiO2 nano-multilayer coating achieves an order-of-magnitude reduction in the hydrogen diffusion coefficient relative to the T91 substrate, arising from the synergistic effect of interface-mediated hydrogen trapping and effective segregation of hydrogen-induced defects. This work elucidates the fundamental structure-performance relationship governing Al2O3/TiO2 nano-multilayer coatings and provides key insights into interface engineering and period thickness optimization for next-generation HPBs in hydrogen energy applications.
Tailoring interface structure is an effective strategy to enhance the mechanical performance of bimetallic laminated composites (BLCs). A nanometer-scale interfacial solid solution layer (ISSL) was engineered in Cu-Ni-Si/1010 steel BLCs via continuous solid/liquid bonding followed by multi-pass cold rolling. The Fe-based ISSL enriched with Cu, Ni, and Si forms between the two layers, which becomes thinner and develops an undulating morphology after rolling. The interfacial orientation deviation from the ideal Kurdjumov-Sachs ({111}Cu//{110}Fe) relationship increases from 7.2° to 15.7° after 90 % rolling reduction due to the formation of the new interfaces. The heterogeneous interface with higher deviation exhibits a larger strengthening effect, achieving an improvement in yield strength of 114 MPa and ultimate tensile strength of 90 MPa compared with the calculations by the rule of mix. The ISSL promotes dislocation accumulation during rolling, which impedes the intragranular dislocation slip, resulting in dislocation tangles and pile-ups. Three-dimensional discrete dislocation dynamics simulations further demonstrate that the deformation-induced high-angle deviation significantly improves the energy barrier for dislocation slip transmission across the interface, improving the yield strength of BLCs. This work provides a strategy for high-performance design of advanced BLCs and reveals the multiscale strengthening mechanisms of the ISSL.
Solar interfacial evaporation is considered a promising approach for freshwater production. However, in high-salinity environments, severe interfacial heat loss and continuous salt accumulation and crystallization hinder the long-term stable operation of evaporators. To address this issue, a thermally adaptive Janus composite aerogel (JNCC) was constructed by integrating a CuS/MMT-based photothermal top layer containing an in situ poly(N-isopropylacrylamide) (PNIPAM) interpenetrating network with a hydrophilic ion-buffering bottom layer. Through the lower critical solution temperature (LCST) behavior of PNIPAM, the aerogel exhibits temperature-driven reversible wettability switching, thereby dynamically regulating interfacial water transport and salt-ion migration. Under illumination, the material surface transitions to a hydrophobic state, reducing interfacial heat loss and inhibiting salt accumulation; when illumination weakens or ceases, the surface regains hydrophilicity, promoting water reflux and dissolving deposited salt crystals, thereby achieving self-cleaning in the dark. The optimized JNCC achieves an evaporation rate of 3.29 kg m−2 h−1 under 1 sun conditions and maintains a stable evaporation rate of 3.10 kg m−2 h−1 in a 20 wt% NaCl solution, with a salt dissolution rate of 0.8 kg m−2 h−1 in the dark. Mechanistic analyses indicate that the thermoresponsive interpenetrating network promotes the accumulation of intermediate water, reduces the effective enthalpy of evaporation, and works in concert with the asymmetric ion-buffering structure to suppress upward salt migration, thereby decoupling water supply from salt accumulation. This aerogel maintains excellent performance even after four months of natural evaporation in water. This study proposes a design strategy for thermoresponsive aerogels that dynamically suppresses salt accumulation during solar evaporation by combining an asymmetric pore structure, thermoresponsive wetting switching, and ion-buffered transport.
The advancement of lightweight, high-performance ceramic matrix composites (CMCs) is of crucial significance for advanced aerospace hot-section components. Within these CMCs, the boron nitride (BN) interface assumes a crucial function in governing both microstructure and comprehensive performance. This research centers on porous mullite fiber-reinforced SiC (P-Mu/SiC) composites featuring a BN interface. It systematically explores how the oxidized BN interface regulates their microstructure, electromagnetic wave (EMW) absorption, and mechanical properties. The thickness and morphology of the B2O3-induced free-carbon layer within P-Mu/SiC composites can be regulated by manipulating the oxidation duration of the hexagonal BN interface. Additionally, the B2O3 phase was employed to further verify the induced mechanism of the free-carbon layer. When the oxidation duration is relatively short (t ≤ 4 h), a double-layer BN-C interface forms in the P-Mu/SiC composite, which is beneficial to optimizing both the EMW absorption and mechanical properties. When the oxidation duration is 4 h, a moderate BN-C interface enables the P-Mu/SiC composite to achieve effective EMW absorption (reflection loss ≤ −10 dB) in X-band at a thinner thickness. Meanwhile, the double interface can promote crack deflection and energy dissipation, resulting in an improved flexural strength of 32 MPa. These findings demonstrate that a B2O3-induced free-carbon interface enables synergistic enhancement of both EMW absorption and mechanical performance, providing a feasible design strategy for high-performance CMCs.
The proliferation of electronic devices and wireless communication technologies has generated an urgent demand for multi-frequency and multifunctional electromagnetic wave (EMW) absorption materials. In this work, we develop a novel MXene-reinforced hierarchical porous metal-organic framework (MOF)-derived sulfide@nitrogen-doped carbon nanofiber composite (PCN/MXene/ZnS@NC) via an electrospinning-assisted strategy combined with vapor sulfuration treatment. The resulting material exhibits a unique necklace-like architecture, in which MOF-derived metal sulfide nanoparticles are uniformly anchored onto the surface of MXene-embedded carbon nanofibers. This configuration generates abundant heterointerfaces and establishes an efficient three-dimensional conductive network, enabling the synergistic interplay of hierarchical porous architecture, dual mesopore distribution, and multiple polarization relaxation processes. The developed PCN/MXene/ZnS@NC composite inherits outstanding EMW absorption performance across the C-band, X-band, and Ku-band, with reflection loss (RL) values of −53.1, −55.9, and −58.3 dB, respectively, showcasing remarkable multiple-frequency compatibility (4.32, 10.88, and 15.92 GHz). Notably, the composite enables lightweight, flexibility, hydrophobicity, and rapid thermal response characteristics.
