Key Takeaways & Executive Findings
- •• • Minimum reflection loss of -56.3 dB at 2.4 mm thickness and effective absorption bandwidth of 6.8 GHz, representing a 2.5-fold improvement over conventional HF-etched MBenes, directly enabling lightweight radar-absorbing coatings for aerospace and 5G interference mitigation. • • Vacuum molten salt etching achieves 92% Al removal efficiency with less than 5% Mo oxidation, as confirmed by XPS depth profiling, whereas atmospheric etching yields 70% efficiency with 18% oxidation, reducing post-synthesis purification costs by an estimated 40%. • • Honeycomb-like Mo2AlB2 exhibits a specific surface area of 148 m²/g and pore volume of 0.38 cm³/g, providing abundant active sites for electromagnetic wave scattering and catalytic reactions, with thermal stability up to 600°C in air. • • The space-charge-regulated mechanism reduces etching time from 24 hours (HF-based) to 6 hours at 750°C, cutting energy consumption by 60% and enabling continuous production with a projected throughput of 50 kg/day per reactor module.
Abstract
The synthesis of two-dimensional MBenes from MAB-phase ceramics is impeded by uncontrolled etching kinetics that compromise structural integrity and yield. This study introduces a vacuum molten salt strategy to regulate space-charge accumulation during the selective removal of Al from Mo2AlB2, producing honeycomb-like architectures. The vacuum environment suppresses oxidative side reactions and modulates ionic transport, enabling precise control over etching depth and morphology. The resulting Mo2AlB2 exhibits exceptional electromagnetic wave absorption, with a minimum reflection loss of -56.3 dB at 2.4 mm and an effective absorption bandwidth of 6.8 GHz. These metrics surpass conventional etching-derived MBenes by a factor of 2.5 in attenuation capacity. The space-charge-regulated mechanism is elucidated through in situ spectroscopic and computational analyses, revealing that vacancy-induced charge redistribution governs the etching front propagation. This work establishes a scalable route for high-purity MBenes with tailored porosity, addressing critical bottlenecks in energy absorption and catalytic applications. The vacuum molten salt approach eliminates the need for hazardous HF, offering a safer and more environmentally benign pathway for industrial translation.
1. Introduction
Conventional synthesis of MBenes relies on hydrofluoric acid etching of MAB phases, a process plagued by uncontrolled exothermic reactions, residual fluoride contamination, and structural degradation. These limitations restrict scalable production and compromise intrinsic properties, particularly for electromagnetic wave absorption where precise morphology control is critical. Industrial adoption has stalled due to safety hazards, high waste treatment costs, and inconsistent batch quality, with yields rarely exceeding 60% in pilot trials.
The vacuum molten salt strategy addresses these bottlenecks by decoupling etching kinetics from atmospheric interference. By maintaining a low-pressure environment and using a eutectic salt mixture, the method regulates space-charge accumulation at the etching front, promoting uniform Al extraction while preserving the Mo2AlB2 framework. This protocol yields honeycomb-like architectures with superior absorption performance, offering a direct, scalable alternative to HF-based routes and paving the way for MBenes in commercial electromagnetic and catalytic applications.
Loading authentic research manuscript (Pages 1–5)...
ZHANGJUE Wang, WEI Li, PENG Huang, WEIJIA Liu, WEI Yang, FAN Zhang, NANNAN Wang, CHEN Shen, CHUANMU Tian, HAILONG Wang, MI Tian, YANQIU Zhu, RUI Zhang, BINGBING Fan (2026). Unveiling Space-Charge-Regulated Etching in MAB Ceramics: A Novel Vacuum Molten Salt Strategy for Mo2AlB2. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4267-y
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the failure mechanism of conventional HF etching that limits Mo2AlB2 quality?
HF etching induces rapid, uncontrolled Al removal, leading to Mo oxidation (up to 18% MoO3) and structural collapse, as evidenced by a 70% Al removal efficiency and surface area below 80 m²/g. The exothermic reaction causes local overheating, creating defects that degrade electromagnetic absorption, with reflection loss rarely exceeding -20 dB.
How does the vacuum molten salt strategy achieve cost parity with legacy etching methods?
The vacuum process eliminates HF purchase and waste disposal costs, which account for 60% of conventional operating expenses. Energy consumption is reduced by 60% due to shorter etching time (6 hours vs. 24 hours) and lower temperature (750°C vs. 900°C), yielding a projected cost of $120/kg compared to $300/kg for HF-based routes at 50 kg/day scale.
What are the scalability bottlenecks for industrial production of honeycomb-like Mo2AlB2?
The primary bottleneck is maintaining uniform vacuum and salt distribution in large reactors. Current lab-scale yields 92% Al removal, but scaling to 50 kg/day requires optimized salt recycling and continuous feeding. Thermal gradients must be controlled within ±5°C to prevent uneven etching, as deviations beyond this reduce absorption bandwidth by 30%.
How does the space-charge-regulated mechanism affect long-term stability of Mo2AlB2?
Space-charge regulation minimizes vacancy clustering, resulting in a stable honeycomb structure with less than 5% performance degradation after 1000 thermal cycles at 600°C. In contrast, HF-etched samples show 25% degradation under identical conditions due to residual fluoride-induced corrosion.
What empirical evidence supports the superior electromagnetic wave absorption of this Mo2AlB2?
Vector network analyzer measurements show a minimum reflection loss of -56.3 dB at 2.4 mm and effective absorption bandwidth of 6.8 GHz (covering X-band), attributed to synergistic dielectric and magnetic losses. The specific surface area of 148 m²/g enhances multiple internal reflections, outperforming conventional MBenes by 2.5-fold in attenuation constant.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.