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Abstract High-entropy materials have been proposed for applications in nuclear systems recently due to their outstanding properties in extreme environments. Chemical complexity in these materials plays an important role in irradiation tolerance since it significantly affects energy dissipation and defect behaviors under particle bombardment. Indeed, better resistance to irradiation-induced amorphization was observed in the high-entropy MAX (HE-MAX) phase (Ti, M)2SnC (M = V, Nb, Zr, Hf). However, in this work, we report an opposite trend in another series of HE-MAX phases (Ti, M)2AlC (M = Nb, Ta, V, Zr). It is demonstrated that the amorphization resistance is sequentially reduced as the number of components increases from single-component Ti2AlC to (TiNbTa)2AlC and (TiNbTaVZr)2AlC. These phenomena are verified through AIMD simulations and interpreted by analyzing the underlying properties combining lattice distortion and bonding characteristics through the first-principle calculation. By developing a machine-learning (ML) model, we can directly predict lattice distortion to screen HE-MAX phases with excellent resistance to irradiation-induced amorphization. We highlight that the elemental species plays a more crucial role in the irradiation tolerance of these MAX phases than the number of constituent elements. Knowledge gained from this study will enable an improved understanding of the irradiation tolerance in HE-MAX phases and other multi-elemental ceramics.

MAX phases and its derived two-dimensional MXenes have attracted considerable interest because of their rich structural chemistry and multifunctional applications. Lewis acid molten salt route provides an opportunity for structure design and performance manipulation of new MAX phases and MXenes, Although a series of new MAX phases and MXenes were successfully prepared via Lewis acid melt route in recent years, few work is explored on nitride MAX phases and MXenes. Herein, a new copper-based 413-type Ti4CuN3 MAX phase was synthesized through isomorphous replacement reaction using Ti4AlN3 MAX phase precursor in molten CuCl2. In addition, it was found that at high temperature Ti4N3Clx MXene will transform into two-dimensional cubic TiNα nanosheets with improved structural stability.

Abstract Electromagnetic (EM) wave pollution is harmful to human health and environment, thus it is absolutely important to develop new electromagnetic wave absorbing materials. MAX phases have been attracted more attention as a potential candidate for electromagnetic wave absorbing materials due to their high conductivity and nanolaminated structure. Herein, two new magnetic MAX phases with multiprincipal elements ((Ti1/3Nb1/3Ta1/3)2FeC and (Ti0.2V0.2Nb0.2Ta0.2Zr0.2)2FeC) in which Fe atoms replace Al atoms in the A sites are successfully synthesized by an isomorphous replacement reaction of multiprincipal (Ti1/3Nb1/3Ta1/3)2AlC and (Ti0.2V0.2Nb0.2Ta0.2Zr0.2)2AlC MAX phases with Lewis acid salt (FeCl2). (Ti1/3Nb1/3Ta1/3)2FeC and (Ti0.2V0.2Nb0.2Ta0.2Zr0.2)2FeC exhibit ferromagnetic behavior, and the Curie temperature (Tc) are 302 and 235 K, respectively. The dual electromagnetic absorption mechanisms that include dielectric and magnetic loss, which is realized in these multiprincipal MAX phases. The minimum reflection loss (RL) of (Ti1/3Nb1/3Ta1/3)2FeC is −44.4 dB at 6.56 GHz with 3 mm thickness, and the effective bandwidth is 2.48 GHz. Additionally, the electromagnetic wave absorption properties of the magnetic MAX phases indicate that magnetic loss also plays an important role besides dielectric loss. This work shows a promising composition‐design strategy to develop MAX phases with good EM wave absorption performance via simultaneously regulating dielectric and magnetic loss together.

Recently, we presented a family of in-plane chemically ordered transition metal borides of the general formula (M′2/3M′′1/3)2AlB2. Here, we investigate incorporation of magnetic rare earth (RE) elements into this structure by synthesis and analysis of Mo4/3RE2/3AlB2, where RE = Ho, Tb, and Er. The crystal structure is verified by X-ray diffraction and scanning transmission electron microscopy, while the composition is derived from energy dispersive X-ray analysis. Through magnetization measurements, we also show that Mo4/3Ho2/3AlB2 orders antiferromagnetically below 9 K. We suggest that (M′2/3M′′1/3)2AlB2 could potentially be a versatile platform for new magnetic materials, in 3D as well as 2D.

To alleviate the increasing energy crisis and achieve energy saving and consumption reduction in building materials, preparing shape-stabilized phase-change materials using bio-porous carbon materials from renewable organic waste to building envelope materials is an effective strategy. In this work, pine cone porous biomass carbon (PCC) was prepared via a chemical activation method using renewable biomaterial pine cone as a precursor and potassium hydroxide (KOH) as an activator. Polyethylene glycol (PEG) and octadecane (OD) were loaded into PCC using the vacuum impregnation method to prepare polyethylene glycol/pine cone porous biomass carbon (PEG/PCC) and octadecane/pine cone porous biomass carbon (OD/PCC) shape-stabilized phase-change materials. PCCs with a high specific surface area and pore volume were obtained by adjusting the calcination temperature and amount of KOH, which was shown as a caterpillar-like and block morphology. The shape-stabilized PEG/PCC and OD/PCC composites showed high phase-change enthalpies of 144.3 J/g and 162.3 J/g, and the solar–thermal energy conversion efficiencies of the PEG/PCC and OD/PCC reached 79.9% and 84.8%, respectively. The effects of the contents of PEG/PCC and OD/PCC on the temperature-controlling capability of rigid polyurethane foam composites were further investigated. The results showed that the temperature-regulating and temperature-controlling capabilities of the energy-storing rigid polyurethane foam composites were gradually enhanced with an increase in the phase-change material content, and there was a significant thermostatic plateau in energy absorption at 25 °C and energy release at 10 °C, which decreased the energy consumption.

Entropy stabilization is an effective method to design and explore MAX phases with outstanding properties via tuning constituent elements and crystal structures, which have received considerable critical attention. Currently, some medium‐/high‐entropy (ME/HE) MAX phases, whose A layers are composed of Al, S, and magnetic elements, are reported, while few discussions about ME/HE‐MAX phases with other A elements (e.g., Sn) are conducted. Herein, fully dense ME/HE‐MAX phase bulks ((TiVNb)2SnC, (TiVNbZr)2SnC, and (TiVNbZrHf)2SnC) are designed and synthesized because of the chemical diversity of MAX phases. The results of Rietveld refinement of X‐ray diffraction, scanning electron microscopy, and high‐resolution scanning transmission electron microscopy‐affiliated energy‐dispersive spectrometer analysis comprehensively verify the crystal structure of ME/HE‐MAX phases. Both the electrical conductivity and the charge carrier mobility are significantly lower than the reported correlation ternary MAX phases, due to the electron scattering and structural defects in ME/HE‐MAX phase crystal structures. Similarly, the electron contribution of thermal conductivity is gradually declining; on the contrary, the phonon plays an increasingly dominant role as temperature increases. Owing to the richness in composition of MAX phases, herein, a composition design route for discovering new MAX phases and tuning their properties is indicated.

Abstract MAX phases are gaining attention as precursors of two-dimensional MXenes that are intensively pursued in applications for electrochemical energy storage. Here, we report the preparation of V2SnC MAX phase by the molten salt method. V2SnC is investigated as a lithium storage anode, showing a high gravimetric capacity of 490 mAh g−1 and volumetric capacity of 570 mAh cm−3 as well as superior rate performance of 95 mAh g−1 (110 mAh cm−3) at 50 C, surpassing the ever-reported performance of MAX phase anodes. Supported by operando X-ray diffraction and density functional theory, a charge storage mechanism with dual redox reaction is proposed with a Sn–Li (de)alloying reaction that occurs at the edge sites of V2SnC particles where Sn atoms are exposed to the electrolyte followed by a redox reaction that occurs at V2C layers with Li. This study offers promise of using MAX phases with M-site and A-site elements that are redox active as high-rate lithium storage materials.

Efficient stimulus-responsive phosphorescence organic materials are attractive, but are extremely rare because of unclear design principles and intrinsically spin-forbidden intersystem crossing. Here, the authors present a facile strategy to achieve ultraviolet irradiation-responsive ultralong room-temperature phosphorescence in several simple amorphous polymer materials.

New MAX phases Ti2(AlxCu1−x)N and Nb2CuC were synthesized by A-site replacement by reacting Ti2AlN and Nb2AlC, respectively, with CuCl2 or CuI molten salt. X-ray diffraction, scanning electron microscopy, and atomically resolved scanning transmission electron microscopy showed complete A-site replacement in Nb2AlC, which lead to the formation of Nb2CuC. However, the replacement of Al in Ti2AlN phase was only close to complete at Ti2(Al0.1Cu0.9)N. Density-functional theory calculations corroborated the structural stability of Nb2CuC and Ti2CuN phases. Moreover, the calculated cleavage energy in these Cu-containing MAX phases are weaker than in their Al-containing counterparts.

Developing novel long-lived room-temperature polymer phosphorescence (RTPP) materials could significantly expand their application scope. Herein, a series of RTPP materials based on eight simple vanilla derivatives for security ink application are reported. Attributed to strong mutual hydrogen bonding with polyvinyl alcohol (PVA) matrix, vanilla-doped PVA films exhibit ultralong phosphorescence emission under ambient conditions observed by naked eyes, where methyl vanillate shows the longest emission time up to 7 s. Impressively, when vanilla-doped PVA materials are utilized as invisible security inks, and the inks not only present excellent luminescent emission stability under ambient conditions but also maintain perfect reversibility between room temperature and 65°C for multiple cycles. Owing to the unique RTPP performance, an advanced anticounterfeiting data encoding/reading strategy based on handwriting technology and complex pattern steganography is developed.

Ti3C2Tx/NiZn ferrite composites were synthesized using a co-precipitation hydrothermal method, and further consolidated using electric current field-assisted sintering technology. Nano NiZn ferrites were inserted into the Ti3C2Tx interlayers with uniform coverage on their surfaces. The incorporation of MXenes promoted the sintering kinetics of the NiZn ferrite ceramics. The electrical conductivity increased by six orders of magnitude compared to pure NiZn ferrite ceramics at room temperature. The present work provides a potential way to develop a large family of dense MXenes/ferrite multiphase ceramics. The multiphase ceramics could be potentially used for the on-beam-line higher-order mode load in advanced particle accelerators.

The polypropylene/aluminum alloy hybrid was prepared via an ultrasonic-assisted hot-pressing technology (UAHPT). The mechanical property and structure of the UAHPT processed polypropylene/aluminum alloy hybrid were explored by the tensile shear test, scanning electron microscopy (SEM), and atomic force microscopy (AFM), respectively. Prior to obtaining the UAHPT processed hybrid, the microporous structures were prepared by the anodic oxidation in a phosphoric acid solution in which the polypropylene (PP) melt flowed into and formed the micro mechanical interlocking structure at the interface of polypropylene/aluminum alloy. The effects of bonding temperature, pressing pressure, ultrasonic amplitude, and ultrasonic time on the bonding properties of the hybrids were investigated via orthogonal experiment. The UAHPT processed hybrid was strengthened and the maximal tensile shear strength reached up to 22.43 MPa for the polypropylene/aluminum alloy hybrid prepared at the optimum vibration processing parameters.

In order to develop high-performance dielectric materials, poly(arylene ether nitrile)-based composites were fabricated by employing surface-hydroxylated calcium copper titanate (CCTO) particles. The results indicated that the surface hydroxylation of CCTO effectively improved the interfacial compatibility between inorganic fillers and the polymer matrix. The composites exhibit not only high glass transition temperatures and an excellent thermal stability, but also excellent flexibility and good mechanical properties, with a tensile strength over 60 MPa. Furthermore, the composites possess enhanced permittivity, relatively low loss tangent, good permittivity-frequency stability and dielectric-temperature stability under 160 °C. Therefore, it furnishes an effective path to acquire high-temperature-resistant dielectric materials for various engineering applications.

Intercalated layered materials offer distinctive properties and serve as precursors for important two-dimensional (2D) materials. However, intercalation of non-van der Waals structures, which can expand the family of 2D materials, is difficult. We report a structural editing protocol for layered carbides (MAX phases) and their 2D derivatives (MXenes). Gap-opening and species-intercalating stages were respectively mediated by chemical scissors and intercalants, which created a large family of MAX phases with unconventional elements and structures, as well as MXenes with versatile terminals. The removal of terminals in MXenes with metal scissors and then the stitching of 2D carbide nanosheets with atom intercalation leads to the reconstruction of MAX phases and a family of metal-intercalated 2D carbides, both of which may drive advances in fields ranging from energy to printed electronics. [ABSTRACT FROM AUTHOR]

The morphology evolution mechanism of polystyrene (PS)/poly (vinyl methyl ether) (PVME) blend thin films with different PS molecular weights (Mw) was studied. It was found that the morphology evolution was closely related to the molecular weight asymmetry between PS and PVME. In the film where Mw(PS) ≈ Mw(PVME), dewetting happened at the interface between the bottom layer and substrate after SD phase separation. While in the film where Mw(PS) >> Mw(PVME), dewetting happened at the interface between the middle PS/PVME blend layer and bottom PVME layer near the substrate prior to phase separation. The different sequences of phase separation and dewetting and different interface for dewetting occurrence were studied by regarding the competitive effects of viscoelasticity contrast between polymer components and preferential wetting between PVME and the substrate. The viscoelastic nature of the PS component played a crucial role in the sequence of phase separation and dewetting. [ABSTRACT FROM AUTHOR]

Tailoring of individual single-atom-thick layers in nanolaminated materials offers atomic-level control over material properties. Nonetheless, multielement alloying in individual atomic layers in nanolaminates is largely unexplored. Here, we report 15 inherently nanolaminated V2(AxSn1-x)C (A = Fe, Co, Ni, Mn, and combinations thereof, with x ~ 1/3) MAX phases synthesized by an alloy-guided reaction. The simultaneous occupancy of the 4 magnetic elements and Sn in the individual single-atom-thick A layers constitutes high-entropy MAX phase in which multielemental alloying exclusively occurs in the 2-dimensional (2D) A layers. V2(AxSn1-x)C exhibit distinct ferromagnetic behavior that can be compositionally tailored from the multielement A-layer alloying. Density functional theory and phase diagram calculations are performed to understand the structure stability of these MAX phases. This 2D multielemental alloying approach provides a structural design route to discover nanolaminated materials and expand their chemical and physical properties. In fact, the magnetic behavior of these multielemental MAX phases shows strong dependency on the combination of various elements. [ABSTRACT FROM AUTHOR]

Due to the promising application of sodium ion batteries (SIBs) in stationary energy storage, great effort has been devoted to the development of anode materials, such as capacitance-type MXenes, battery-type metal sulfides/selenides and red phosphorus. However, these materials severely suffer from either low rate capability or insufficient lifespans. Toward this end, a dual-mode sodium storage concept is proposed based on the simultaneous incorporation of capacitance-type and battery-type electrochemical behavior. Correspondingly, a novel strategy of in situ formation of NaTi2(PO4)3 cubes on Ti3C2 MXene nanosheets in a liquid transformation way was developed to fabricate a dual-mode anode material (denoted as MXene@NTP-C). Acting as the anode material for SIBs, MXene@NTP-C shows outstanding rate capacities (49% capacity retention at 10 A g-1) and remarkable cycling performance (remaining stable after 10 000 cycles at 5 A g-1). Electrochemical and kinetic analyses reveal that this excellent performance was attributed to the dual-mode accommodation (46-71% capacitive contribution at 0.1-1 mV s-1) of sodium onto pseudocapacitance-type MXene and into battery-type NaTi2(PO4)3. The dual-mode sodium storage concept proposed here provides an opportunity to tackle the trade-off between energy and power densities. [ABSTRACT FROM AUTHOR]

Straw return is a promising method for managing soil organic carbon (SOC) in agricultural soils and thus may promote sustainable land use. However, the optimal straw-return strategy for economically sustainable grain production in intensive winter wheat (Triticum aestivum L.)-summer maize (Zea mays L.) cropping systems remains uncertain. A 4-yr field experiment was conducted in the central North China Plain to determine the effects of straw return on SOC stock and lability, soil enzyme activity, and grain yield, and to further evaluate the sustainability of crop production in intensive wheat-maize double-cropping systems. Four treatments were tested: no straw return (NR), return of wheat straw (WR), return of maize straw (MR), and return of both wheat and maize straw (WR+MR). Compared with the initial value, SOC stocks significantly increased by 2.8, 5.4, and 13.1% in WR, MR, and WR+MR, respectively, and significantly decreased by 2.9% in NR. Stocks of KMnO4-oxidizable C and microbial biomass C; activities of soil invertase, protease, and dehydrogenase; and the C management index were significantly higher with than without straw return and followed the order NR < WR < MR < WR+MR. Yields of wheat and maize were highest in WR+MR, but economic sustainability was higher in WR and MR relative to NR and WR+MR. Our results indicate that return of either wheat or maize straw is sufficient to maintain SOC levels and may be the optimal strategy for economically sustainable grain production in the central North China plain. [ABSTRACT FROM AUTHOR]

Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) were employed to study the microstructure of self-reinforced high-density polyethylene (HDPE) prepared by conventional injection molding (CIM) and a low frequency vibration-assisted injection molding (VAIM). SEM micrographs following permanganic etching showed the self-reinforcement of HDPE is mainly due to the existence of shish-kebab morphology within the core region for VAIM-processed HDPE samples. Pronounced molecular alignment was identified by the WAXD data. An approximate 9% increase in the crystallinity was confirmed by DSC. Both preferred molecular orientation and increased crystallinity serve to yield stronger VAIM-processed injection moldings. [ABSTRACT FROM AUTHOR]

The effect of SBS and nano-CaCO3 on the mechanical properties of PS blends was studied, and their morphologies were characterised by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The Izod impact strengths of notched samples of PS/SBS/CaCO3 blends with nanometre particles of nano-CaCO3 and SBS are higher than those of PS and PS/SBS blends with the same content of SBS, and the tensile strengths are higher than those of PS/SBS blends. The inclusion of nano-CaCO3 within the dispersed phase of SBS enlarges the volume of the domains of SBS, which increases the toughness of the ternary blends (PS/SBS/CaCO3). The mass ratio of SBS/CaCO 3 plays an important role in the properties of the ternary blends because it affects the concentration of SBS in these blends, the dispersion of nano-CaCO3 and the morphology of the ternary blends. [ABSTRACT FROM AUTHOR]

The article focuses on a study on ultralong room temperature phosphorescence (URTP) from amorphous organic materials. Without visible fluorescence and phosphorescence under ambient conditions, a series of URTP films with long lifetimes and high phosphorescent quantum yields were obtained from amorphous organic phosphors.