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The deintercalation of weakly bonded A element affects the microstructure and properties of MAX phases and their reinforced composites. In this work, the effect of M-site element on the interaction of Al-containing M2AlC (M = V, Cr) phase and Ag, and the induced properties of Ag/M2AlC electrical contact materials (ECMs) were investigated. Though Ag and Al are soluble to each other and can form intermetallics, the variation of M element significantly affected the vacancy formation of Al, and thereby the interfacial reaction of Ag/M2AlC. The difficult formation of Al vacancy in V2AlC contributed to no obvious interfacial reaction in Ag/V2AlC. But the easy deintercalation of Al atoms in Cr2AlC led to their massive replacement by Ag, which generated Ag nano-twins and Cr3C2 with the same crystallographic relationship in one original Cr2AlC, and Cr7C3 and Ag3Al as well. Due to the distinct interactions, the resistivities of Ag/V2AlC and Ag/Cr2AlC increased by roughly 1 and 5 times after sintering, respectively. The low resistivity and proper hardness of the sintered Ag/V2AlC, which were very close to those of the “all-purpose” commercial Ag/CdO, contributed to its superior arc erosion resistance.

Abstract The all‐organic aqueous dual‐ion batteries (ADIBs) have attracted increasing attention due to the low cost and high safety. However, the solubility and unstable activity of organic electrodes restrict the synergistic storage of anions and cations in the symmetric ADIBs. Herein, a novel polyimide‐based covalent organic framework (labeled as NTPI‐COF) is constructed, featured with the boosted structure stability and electronic conductivity. Through regulating the porosity and bipolarity integrally, the NTPI‐COF possesses hierarchical porous structure (mesopore and micropore) and abundant bipolar active centers (C═O and C─N), which exhibits rapid dual‐ion transport and storage effects. As a result, the NTPI‐COF as the electrodes for ADIBs deliver a high reversible capacity of 109.7 mA h g−1 for Na+ storage and that of 74.8 mA h g−1 for Cl– storage at 1 A g−1, respectively, and with a capacity retention of 93.2% over 10 000 cycles at 10 A g−1. Additionally, the all‐organic ADIBs with symmetric NTPI‐COF electrodes achieve an impressive energy density of up to 148 W h kg−1 and a high power density of 2600 W kg−1. Coupling the bipolarity and porosity of the all‐organic electrodes applied in ADIBs will further advance the development of low‐cost and large‐scale energy storage.

Abstract Potassium‐ion batteries (PIBs) offer a cost‐effective and resource‐abundant solution for large‐scale energy storage. However, the progress of PIBs is impeded by the lack of high‐capacity, long‐life, and fast‐kinetics anode electrode materials. Here, we propose a dual synergic optimization strategy to enhance the K+ storage stability and reaction kinetics of Bi2S3 through two‐dimensional compositing and cation doping. Externally, Bi2S3 nanoparticles are loaded onto the surface of three‐dimensional interconnected Ti3C2Tx nanosheets to stabilize the electrode structure. Internally, Cu2+ doping acts as active sites to accelerate K+ storage kinetics. Various theoretical simulations and ex situ techniques are used to elucidate the external–internal dual synergism. During discharge, Ti3C2Tx and Cu2+ collaboratively facilitate K+ intercalation. Subsequently, Cu2+ doping primarily promotes the fracture of Bi2S3 bonds, facilitating a conversion reaction. Throughout cycling, the Ti3C2Tx composite structure and Cu2+ doping sustain functionality. The resulting Cu2+‐doped Bi2S3 anchored on Ti3C2Tx (C‐BT) shows excellent rate capability (600 mAh g–1 at 0.1 A g–1; 105 mAh g–1 at 5.0 A g–1) and cycling performance (91 mAh g–1 at 5.0 A g–1 after 1000 cycles) in half cells and a high energy density (179 Wh kg–1) in full cells.

Abstract Ammonium ion batteries are promising for energy storage with the merits of low cost, inherent security, environmental friendliness, and excellent electrochemical properties. Unfortunately, the lack of anode materials restricts their development. Herein, we utilized density functional theory calculations to explore the V2CT x MXene as a promising anode with a low working potential. V2CT x MXene demonstrates pseudocapacitive behavior for ammonium ion storage, delivering a high specific capacity of 115.9 mAh g−1 at 1 A g−1 and excellent capacity retention of 100% after 5000 cycles at 5 A g−1. In-situ electrochemical quartz crystal microbalance measurement verifies a two-step electrochemical process of this unique pseudocapacitive storage behavior in the ammonium acetate electrolyte. Theoretical simulation reveals reversible electron transfer reactions with [NH4 +(HAc)3]···O coordination bonds, resulting in a superior ammonium ion storage capacity. The generality of this acetate ion enhancement effect is also confirmed in the MoS2-based ammonium-ion battery system. These findings open a new door to realizing high capacity on ammonium ion storage through acetate ion enhancement, breaking the capacity limitations of both Faradaic and non-Faradaic energy storage.

Abstract The integration of electrochromic devices and energy storage systems in wearable electronics is highly desirable yet challenging, because self‐powered electrochromic devices often require an open system design for continuous replenishment of the strong oxidants to enable the coloring/bleaching processes. A self‐powered electrochromic device has been developed with a close configuration by integrating a Zn/MnO2 ionic battery into the Prussian blue (PB)‐based electrochromic system. Zn and MnO2 electrodes, as dual shared electrodes, the former one can reduce the PB electrode to the Prussian white (PW) electrode and serves as the anode in the battery; the latter electrode can oxidize the PW electrode to its initial state and acts as the cathode in the battery. The bleaching/coloring processes are driven by the gradient potential between Zn/PB and PW/MnO2 electrodes. The as‐prepared Zn||PB||MnO2 system demonstrates superior electrochromic performance, including excellent optical contrast (80.6%), fast self‐bleaching/coloring speed (2.0/3.2 s for bleaching/coloring), and long‐term self‐powered electrochromic cycles. An air‐working Zn||PB||MnO2 device is also developed with a 70.3% optical contrast, fast switching speed (2.2/4.8 s for bleaching/coloring), and over 80 self‐bleaching/coloring cycles. Furthermore, the closed nature enables the fabrication of various flexible electrochromic devices, exhibiting great potentials for the next‐generation wearable electrochromic devices.

Al-containing MAX phase ceramic has demonstrated great potential in the field of high-performance low-voltage electrical contact material. Elucidating the anti-arc erosion mechanism of the MAX phase is crucial for further improving performance, but it is not well-understood. In this study, Ag/Ti3AlC2 electrical contact material was synthesized by powder metallurgy and examined by nanoindentation techniques such as constant loading rate indentation, creep testing, and continuous stiffness measurements. Our results indicated a gradual degradation in the nano-mechanical properties of the Ti3AlC2 reinforcing phase with increasing arc erosion times, although the rate of this degradation appeared to decelerate over arc erosion times. Specifically, continuous stiffness measurements highlighted the uneven mechanical properties within Ti3AlC2, attributing this heterogeneity to the phase’s decomposition. During the early (1–100 times) and intermediate (100–1000 times) stages of arc erosion, the decline in the nano-mechanical properties of Ti3AlC2 was primarily ascribed to the decomposition of Ti3AlC2 and limited surface oxidation. During the later stage of arc erosion (1000–6200 times), the inner region of Ti3AlC2 also sustained arc damage, but a thick oxide layer formed on its surface, enhancing the mechanical properties and overall arc erosion resistance of the Ag/Ti3AlC2.

Serious arc erosion is the main reason for premature failure of the Ag-matrix composite electrical contact materials in actual service. Clarifying the structure and property degradation process is crucial for creating eco-friendly Ag/MAX electrical contacts and upgrading high-performance materials for low-voltage switch applications. In this study, the representative Ag/Ti2AlC electrical contacts were designed into three arc erosion stages (from 1 to 5610 cycles) by ex-situ arc discharging experiment, and the nanoindentation technique was then applied to in-depth analyze the evolution behavior of nano-mechanical properties by comparing nano hardness, modulus, creep, continuous stiffness, elastic/plastic deformation, and NanoBlitz 3D Mapping indentation results in different erosion stages. Finally, the inherent relationship among the structural dissociation of Ti2AlC, and compositional changes of Ag/Ti2AlC interface and nano-mechanical properties of composite was revealed, and the material degradation model and anti-arc erosion mechanism were proposed. This work further elucidates the intrinsic source of excellent arc erosion resistance and degradation process of Ag/Ti2AlC composite from the nano-mechanical perspective and lays a theoretical foundation for the future design and optimization of this material system.

Highlights Heterostructure engineering is proposed to construct CoTe2/ZnTe heterostructures with built-in electric field. Conductive and elastic Ti3C2T x MXene is introduced to improve the conductivity and alleviate the volume change of CoTe2/ZnTe upon cycling. The resulting CoTe2/ZnTe/Ti3C2T x (CZT) demonstrates outstanding rate capability (137.0 mAh g−1 at 10 A g−1) and cycling stability (175.3 mAh g−1 after 4000 cycles at 3.0 A g−1). Moreover, the CZT-based full cells demonstrate excellent energy density (220.2 Wh kg−1) and power density (837.2 W kg−1).

Metal whisker growth poses a significant reliability threat to electronic devices. Previous investigations have predominantly focused on metal platings and alloy solder samples, yet the intricate factors involved have yielded inconsistent comprehension of the phenomenon. To achieve a comprehensive understanding, exploring intermetallic compounds (IMCs) may offer a novel standpoint. Herein, we present the first report on the growth of single crystal cadmium (Cd) whiskers on Ti2Cd IMC, accompanied by the characterization of their composition, crystal structure, and morphological features. Furthermore, the influence of mechanical damage and temperature on the whisker growth is examined. Ball milling induces the decomposition of Ti2Cd, liberating active Cd atoms with elevated chemical potentials that consequently feed the whisker growth. These findings augment the existing knowledge on the topic of the metal whisker growth and provide fresh perspectives and references for further investigations in this field.

The achievement of chemical diversity and performance regulation of MAX phases primarily relies on solid solution approaches. However, the reported A-site solid solution is undervalued due to their expected chemical disorder and compliance with Vegard’s law, as well as discontinuous composition and poor purity. Herein, we synthesized high-purity Ti2(SnxAl1−x)C (x = 0–1) solid solution by the feasible pressureless sintering, enabling us to investigate their property evolution upon the A-site composition. The formation mechanism of Ti2(SnxAl1−x)C was revealed by thermal analysis, and crystal parameters were determined by Rietveld refinement of X-ray diffraction (XRD). The lattice constant (a) adheres to Vegard’s law, while the lattice constant (c) and internal free parameter (zM) have noticeable deviations from the law, which is caused by the significant nonlinear distortion of Ti6C octahedron as Al atoms are substituted by Sn atoms. Also, the deviation also results in nonlinear changes in their physicochemical properties, which means that the solid solution often exhibits better performance than end members, such as hardness, electrical conductivity, and corrosion resistance. This work offers insights into the deviation from Vegard’s law observed in the A-site solid solution and indicates that the solid solution with enhanced performance may be obtained by tuning the A-site composition.

Highlights Curving 2D MXene into 1D nanofibers can effectively stop the restacking of MXene flakes, and then the nanofibers are used to construct a lightweight and multifunctional MXene/C aerogel. The MXene/C aerogels achieved an RLmin of − 53.02 dB and EAB of 5.3 GHz. The radar cross-sectional reduction value of MXene/C aerogels can reach 12.02 dB m2. Integrating multiple functions such as thermal insulation, sensing, and microwave absorption into one material—MXene/C aerogel.

Cement-based materials are the foundation of modern buildings but suffer from intensive energy consumption. Utilizing cement-based materials for efficient energy storage is one of the most promising strategies for realizing zero-energy buildings. However, cement-based materials encounter challenges in achieving excellent electrochemical performance without compromising mechanical properties. Here, we introduce a biomimetic cement-based solid-state electrolyte (labeled as l-CPSSE) with artificially organized layered microstructures by proposing an in situ ice-templating strategy upon the cement hydration, in which the layered micropores are further filled with fast-ion-conducting hydrogels and serve as ion diffusion highways. With these merits, the obtained l-CPSSE not only presents marked specific bending and compressive strength (2.2 and 1.2 times that of traditional cement, respectively) but also exhibits excellent ionic conductivity (27.8 mS·cm−1), overwhelming most previously reported cement-based and hydrogel-based electrolytes. As a proof-of-concept demonstration, we assemble the l-CPSSE electrolytes with cement-based electrodes to achieve all-cement-based solid-state energy storage devices, delivering an outstanding full-cell specific capacity of 72.2 mF·cm−2. More importantly, a 5 × 5 cm2 sized building model is successfully fabricated and operated by connecting 4 l-CPSSE-based full cells in series, showcasing its great potential in self-energy-storage buildings. This work provides a general methodology for preparing revolutionary cement-based electrolytes and may pave the way for achieving zero-carbon buildings.

Abstract Background Kashin–Beck disease (KBD) is an endemic deformable bone and joint disease, which affects the quality of life (QOL) of patients. We conducted a cross-sectional study of the QOL of KBD patients by a new KBD quality of life (KBDQOL) questionnaire. Methods A total of 252 KBD patients and 248 OA patients came from Northwest China, and 260 healthy people living in the same area as KBD and osteoarthritis (OA) patients served as the controls. KBDQOL questionnaire was used to evaluate the QOL of all objects. Results The average scores for physical functions, activity limitations, support of society, mental health and general health were significantly lower in KBD patients than that in OA patients and healthy people except for economics. Monofactor analysis showed that age, height, weight status, education level and grade of KBD had a significant effect on KBDQOL score. Multivariate analysis showed that grade of KBD was the influencing factor of physical function score; gender, age, height, grade of KBD and duration of symptoms were the influencing factors of activity restriction score; age and grade of KBD were factors affecting the general health score. Conclusion The QOL of KBD patients was significantly lower than that of OA patients and healthy people. The KBDQOL questionnaire may be a promising tool for assessing the QOL of KBD patients.

Abstract Hydrogel actuators have shown great promise in underwater robotic applications as they can generate controllable shape transformations upon stimulation due to their ability to absorb and release water reversibly. Herein, a photoresponsive anisotropic hydrogel actuator is developed from poly(N‐isopropylacrylamide) (PNIPAM) and gold‐decorated carbon nitride (Au/g‐C3N4) nanoparticles. Carbon nitride nanoparticles endow hydrogel actuators with photocatalytic properties, while their reorientation and mobility driven by the electrical field provide anisotropic properties to the surrounding network. A variety of light‐fueled soft robotic functionalities including controllable and programmable shape‐change, gripping, and locomotion is elicited. A responsive flower‐like photocatalytic reactor is also fabricated, for water splitting, which maximizes its energy‐harvesting efficiency, that is, hydrogen generation rate of 1061.82 µmol g−1 h−1, and the apparent quantum yield of 8.55% at 400 nm, by facing its light‐receiving area adaptively towards the light. The synergy between photoactive and photocatalytic properties of this hydrogel portrays a new perspective for the design of underwater robotic and photocatalytic devices.

High‐performance electromagnetic (EM) absorbing materials are in urgent need due to severe EM pollution caused by fast development of communication technology and electronic devices. Gradient structure benefits EM absorbing performance. However, the relevant study is very limited, and the relationship between component layers and overall performance is unclear. Herein, a gradient structure containing impedance matching layer, lossy layer, and reflective layer is built via repeated casting‐drying method using Ti3C2Tx MXene and polyvinyl alcohol. With optimized gradient structure, the minimum reflection loss (RL) reaches −74.8 dB with effective absorbing bandwidth (EAB) covering the whole X‐band. The good absorbing performance is ascribed to the good impedance matching, which is derived from the stepwisely increased permittivity of each layer. Moreover, it is found that RL reaches the lowest value when lossy layer permittivity is close to the average permittivity of impedance matching layer and reflective layer. In addition, the decrease of lossy layer permittivity causes the decrease of total thickness of the gradient structure. This work demonstrates the effectiveness of gradient structure toward strong and broadband microwave absorption and provides rules for designing proper gradient structures to satisfy different requirements.

ZnO whiskers have many applications, such as in medical and photocatalysis fields. In this study, an unconventional preparation approach is reported, realizing the in-situ growth of ZnO whiskers on Ti2ZnC. The weak bonding between the layer of Ti6C-octahedron and the Zn-atom layers leads to the easy extraction of Zn atoms from Ti2ZnC lattice points, resulting in the formation of ZnO whiskers on the Ti2ZnC surface. This is the first time that ZnO whiskers have been found to grow in-situ on Ti2ZnC substrate. Further, this phenomenon is amplified when the size of the Ti2ZnC grains is mechanically reduced by ball-milling, which bodes a promising route to prepare ZnO in-situ on a large scale. Additionally, this finding can also help us better understand the stability of Ti2ZnC and the whiskering mechanism of MAX phases.

Two-dimensional (2D) materials have received tremendous attention because they possess a set of merits not available in bulk materials, such as large specific surface area, low energy barrier for electron transportation and short ion diffusion path. These advantages are desirable especially for the electrodes in electrochemical energy storage devices. MXenes, first synthesized in 2011 by etching their MAX phase precursors, have plural reasons to represent a new family of 2D materials. Their rich diversity in structure and composition together with the uncommon combination of good electrical conductivity and hydrophilicity makes themselves outstand in the whole 2D materials world. Based on these advantages, MXenes hold great promise for various technologically important applications, particularly in developing new energy storage techniques for advanced smart systems, such as portable and flexible electronics. There have been remarkable research achievements in the synthesis and application of MXene-based materials. While new synthesis routes being continuously reported, MXenes with new composition and novel structure have also been routinely discovered, which will undoubtedly help understand the fundamental properties and expand the application scope of MXenes. As for their energy storage-related applications, to cope with the intrinsic weakness of MXenes, many endeavors have been made by doping, structure-tuning and compositing with hybrid ingredients. In this review, the current status of MXenes synthesis and up-to-date progress of their applications in supercapacitors, metal-ion batteries and lithium sulfur batteries are summarized and discussed, and the typical work on the application of MXenes for the aforementioned three categories is respectively tabulated for reference and comparison.

Abstract Slip casting and subsequent pressureless sintering (PLS) allow the preparation of complex-shaped and large-sized Ti3AlC2 components for many potential applications. The behaviors of the suspensions, green compacts, and sintered samples of Ti3AlC2 were studied in this paper. The optimized condition of 1 wt% of arabic gum as dispersant at pH = 10 results in a Ti3AlC2 suspension for slip casting Ti3AlC2 green compacts without macro defects or cracks. The sintering temperature and A14C3 embedding powder are found to dominate the properties of the sintered Ti3AlC2 samples. The Ti3AlC2 sample sintered at 1450 °C for 1.5 h with A14C3 embedding powder reaches the best properties, namely 95.3% relative density, hardness of 4.18 GPa, thermal conductivity of 29.11 W·m−1K−1, and electrical resistivity of 0.39 μΩ·m. The findings in this work may pave the way for the application of MAX phases with large size and complex shape

Abstract New Ag/Ti2SnC (Ag/TSC) composites with uniform microstructure were prepared by powder metallurgy. The superior wettability between Ag and Ti2SnC was confirmed with a contact angle of 14°. Arc erosion properties of Ag/10wt%Ti2SnC (Ag/10TSC) and Ag/20wt%Ti2SnC (Ag/20TSC) contacts were investigated under 400 V/100 A/AC-3 and compared with Ag/CdO contact. The Ag/10TSC contact exhibited comparable arc erosion property to Ag/CdO contact. The fine arc erosion resistance was attributed to the good wettability between Ti2SnC and Ag, the good heat-conducting property of Ag/10TSC, and the slight decomposition of Ti2SnC that absorbed part of electric arc energy. The excessive Ti2SnC significantly decreased the thermal conducting property of the Ag/20TSC composite, resulting in the severe heat accumulation that decomposed Ti2SnC and deteriorated arc erosion property. The oxidation behavior of Ti2SnC under high electric arc temperature was also studied and then an arc erosion mechanism was proposed to get a comprehensive understanding on the arc erosion property of Ag/TSC composites.

Abstract Black phosphorene is a novel two-dimensional material which has unique properties and wide applications. Using first-principles calculations, we investigated the adsorption behavior of 12 different transition metals (TMs; Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au) on phosphorene. Our results showed that all of the adsorption systems have a large binding energy. The Fe-, Co-, and Au-phosphorene systems display magnetic states with magnetic moments of 2, 1, and 0.96 μ B, respectively, which means that these systems are magnetic semiconductors. Adsorption of oxygen molecules on TM-phosphorene was also investigated. Interestingly, all the O2-(TM-phosphorene) systems, except O2-(Pd-phosphorene), can elongate the O–O bond, which is critical to their application as catalysts in the oxidation of CO. We also found that the adsorption of O2 molecules enables the O2-(Fe-, Ni-, Cu-, Ir-, Rh-, Ag-, and Au-phosphorene) systems to become magnetic semiconductors, and it allows O2-(Co-phosphorene) to display half-metallic state. Our results are expected to have important implications for phosphorene-based catalysis and spintronics.

Abstract Background The purpose of this study was to test effects of negative pressure on tendon–bone healing after reconstruction of anterior cruciate ligament (ACL) in rabbits. Methods Hind legs of 24 New Zealand White rabbits were randomly selected as negative pressure group and the contralateral hind legs as control. Reconstruction of the ACL was done. Joints of the negative pressure side were placed with drainage tubes connecting the micro-negative pressure aspirator. Control side was placed with ordinary drainage tubes. Drainage tubes on both sides were removed at the same time 5 days after operation. After 6 weeks, joint fluid was drawn to detect the expression levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α); at the same time, femur–ligament–tibia complex was obtained to determine tendon graft tension and to observe the histomorphology, blood vessels of the tendon–bone interface, and expression of vascular endothelial growth factor (VEGF). Results The maximum load breakage of tendon graft was significantly greater in the negative pressure group than in the control group (P

Using as thermal reflection coating fillers is a significant recycle method for the largely available by-product of shell powders in aquaculture. However, the organics in the shell powder harm its reflection ability. To enhance the thermal reflection performance of the shell powder filled coatings, in this work, the calcined shell powders were used to fill coatings, and the performance of the coatings filled by the calcined shell powders under different temperatures was comparably investigated. Experimental results indicate that after calcination at 400 °C, the organics in the shell powders are removed, whereas the crystal structure of the calcium carbonate is maintained and its particles are refined, leading to an increase in its reflectance. Calcination at temperatures higher than 400 °C deteriorates the properties of the shell powder, due to the sintering of the calcium carbonate particles. The coatings filled by shell powder calcinated at 400 °C deliver the best cooling effect and comparable scouring resistance.