benxue liu

The ultrathin van der Waals (vdW) LaOCl is synthesized by controlling the growth kinetics. Due to the considerable dielectric properties of LaOCl and its dangling-bond-free surface, the MoS₂ field-effect transistor (FET) with vdW LaOCl dielectric exhibits ultralow hysteresis. LaOCl possesses the tremendous potential to act as an ideal gate dielectric for two-dimensional FETs.

Abstract

Downsizing silicon-based transistors can result in lower power consumption, faster speeds, and greater computational capacity, although it is accompanied by the appearance of short-channel effects. The integration of high-mobility 2D semiconductor channels with ultrathin high dielectric constant (high-κ) dielectric in transistors is expected to suppress the effect. Nevertheless, the absence of a high-κ dielectric layer featuring an atomically smooth surface devoid of dangling bonds poses a significant obstacle in the advancement of 2D electronics. Here, ultrathin van der Waals (vdW) lanthanum oxychloride (LaOCl) dielectrics are successfully synthesized by precisely controlling the growth kinetics. These dielectrics demonstrate an impressive high-κ value of 10.8 and exhibit a remarkable breakdown field strength (E _bd) exceeding 10 MV cm⁻¹. Remarkably, the conventional molybdenum disulfide (MoS₂) field-effect transistor (FET) featuring a dielectric made of LaOCl showcases an almost negligible hysteresis when compared to FETs employing alternative gate dielectrics. This can be attributed to the flawlessly formed vdW interface and excellent compatibility established between LaOCl and MoS₂. These findings will motivate the further exploration of rare-earth oxychlorides and the development of more-than-Moore nanoelectronic devices.

An innovative compositional design concept enables the construction of a unique transitional microstructure between traditional amorphous and nanocrystalline alloys, which results in an alloy with an unprecedented combination of exceptionally high saturation magnetic flux density (B _s = 1.94 T) and ultralow coercivity (H _c = 4.3 A m⁻¹), breaking the general trade-off between B _s and H _c in the soft-magnetic-material family.

Abstract

High saturation magnetic flux density (B _s) of soft magnetic materials is essential for increasing the power density of modern magnetic devices and motor machines. Yet, increasing B _s is always at the expense of high coercivity (H _c), presenting a general trade-off in the soft magnetic material family. Here, superior comprehensive soft magnetic properties, i.e., an exceptionally high B _s of up to 1.94 T and H _c as low as 4.3 A m⁻¹ are unprecedentedly combined in an FeCo-based alloy. This alloy is obtained through a composition design strategy to construct a transitional microstructure between amorphous and traditional nanocrystalline alloys, with nanocrystals (with < 5 nm-sized crystal-like regions around) sparsely dispersed in an amorphous matrix. Such transitional microstructure possesses extremely low magnetic anisotropy caused by the annihilation of quasi-dislocation dipoles, and a strong magnetic exchange interaction, which leads to excellent comprehensive magnetic properties. The results provide useful guidelines for the development of the next generation of soft magnetic materials, which are promising for applications of high-frequency, high-efficiency, and energy-saving devices.

A polyimide (PI) nanofibrous aerogel consisted of interlocked curly nanofibrous networks (crimp percentage 28.5%) is directly assembled by electrospinning. Benefiting from strong porous aerogel structure (porosity 99.8%), the PI aerogel achieves ultralight property (density 2.4 mg cm⁻³), mechanical robustness at extreme conditions, and ultralow thermal conductivity (22.4 mW m⁻¹ K⁻¹), thereby offering a promising candidate for thermal insulation under extreme temperature.

Abstract

Maintaining human body temperature is one of the basic needs for living, which requires high-performance thermal insulation materials to prevent heat exchange with external environment. However, the most widely used fibrous thermal insulation materials always suffer from the heavy weight, weak mechanical property, and moderate capacity to suppress heat transfer, resulting in limited personal cold and thermal protection performance. Here, an ultralight, mechanically robust, and thermally insulating polyimide (PI) aerogel is directly synthesized via constructing 3D interlocked curly nanofibrous networks during electrospinning. Controlling the solution/water molecule interaction enables the rapid phase inversion of charged jets, while the multiple jets are ejected by regulating charge density of the fluids, thus synergistically allowing numerous curly nanofibers to interlock and cross-link with each other to form porous aerogel structure. The resulted PI aerogel integrates the ultralight property with density of 2.4 mg cm⁻³, extreme temperature tolerance (mechanical robustness over −196 to 300 °C), and thermal insulation performance with ultralow thermal conductivity of 22.4 mW m⁻¹ K⁻¹, providing an ideal candidate to keep human thermal comfort under extreme temperature. This work can provide a source of inspiration for the design and development of nanofibrous aerogels for various applications.

Polyphenylene sulfide (PPS) aerogels formed from an environmentally benign, nontoxic solvent are fabricated using material extrusion (MEX) and in situ thermally induced phase separation (TIPS). Printed aerogels demonstrate geometric flexibility and hierarchical porosity while maintaining physical properties inherent to cast analogs. This new additive manufacturing process chain presents a straightforward method for developing printed polymer aerogels from TIPS systems requiring high processing temperatures.

Abstract

Additive manufacturing (AM) of aerogels increases the achievable geometric complexity, and affords fabrication of hierarchically porous structures. In this work, a custom heated material extrusion (MEX) device prints aerogels of poly(phenylene sulfide) (PPS), an engineering thermoplastic, via in situ thermally induced phase separation (TIPS). First, pre-prepared solid gel inks are dissolved at high temperatures in the heated extruder barrel to form a homogeneous polymer solution. Solutions are then extruded onto a room-temperature substrate, where printed roads maintain their bead shape and rapidly solidify via TIPS, thus enabling layer-wise MEX AM. Printed gels are converted to aerogels via postprocessing solvent exchange and freeze-drying. This work explores the effect of ink composition on printed aerogel morphology and thermomechanical properties. Scanning electron microscopy micrographs reveal complex hierarchical microstructures that are compositionally dependent. Printed aerogels demonstrate tailorable porosities (50.0–74.8%) and densities (0.345–0.684 g cm⁻³), which align well with cast aerogel analogs. Differential scanning calorimetry thermograms indicate printed aerogels are highly crystalline (≈43%), suggesting that printing does not inhibit the solidification process occurring during TIPS (polymer crystallization). Uniaxial compression testing reveals that compositionally dependent microstructure governs aerogel mechanical behavior, with compressive moduli ranging from 33.0 to 106.5 MPa.

This work develops inorganic ionic co-cross-linking by using calcium carbonate oligomers and calcium phosphate oligomers (CCOs and CPOs) to produce a group of compounds with the chemical formulas Ca(CO₃) _x (PO₄)_{2(1- x )/3} (0 < x < 1), referred to as CaCPs. They exhibit molecular homogeneity, a single-transition temperature and adjustable chemical compositions, and they are readily transformed to high strength alloy-like minerals (ALMs) by heat-induced crystallization.

Abstract

Alloys often combine different metals to generate superior mechanical properties. However, it is challenging to prepare high mechanical strength minerals with similar strategies. Using calcium carbonate (CaC) and calcium phosphate (CaP) as examples, this work synthesizes a group of compounds with the chemical formulas Ca(CO₃) _x (PO₄)_{2(1- x )/3} (0 < x < 1, CaCPs) by cross-linking ionic oligomers. Unlike mixtures, these CaCPs exhibit a single temperature for the phase transition from amorphous to crystallized CaC (calcite) and CaP (hydroxyapatite). By heat-induced synchronous crystallization, dual-phase CaC/CaP with continuous crystallized boundaries are resembled to alloy-like minerals (ALMs). The mechanical properties of the ALMs are adjusted by tailoring their chemical compositions to reach a hardness of 5.6 GPa, which exceed those of control calcite and hydroxyapatite samples by 430% and 260%, respectively. This strategy expands the chemical scope of inorganic materials and holds promise for preparing high-performance minerals.

All-organic aerogel fibers stable up to 650 °C derived from Zylon are synthesized by controlled proton absorption gelation spinning and heat-induced cross-linking strategy. The aerogel fibers exhibit high flexibility, high mechanical strength (8.6 MPa), good flame retardancy (LOI = 54.2%), and textiles woven from these aerogel fibers exhibit outstanding thermal insulation and sensing properties.

Abstract

The exceptional lightweight, highly porous, and insulating properties of aerogel fibers make them ideal for thermal insulation. However, current aerogel fibers face limitations due to their low resistance to harsh environments and a lack of intelligent responses. Herein, a universal strategy for creating polymer aerogel fibers using crosslinked nanofiber building blocks is proposed. This approach combines controlled proton absorption gelation spinning with a heat-induced crosslinking process. As a proof-of-concept, Zylon aerogel fibers that exhibited robust thermal stability (up to 650 °C), high flame retardancy (limiting oxygen index of 54.2%), and extreme chemical resistance are designed and synthesized. These fibers possess high porosity (98.6%), high breaking strength (8.6 MPa), and low thermal conductivity (0.036 W m⁻¹ K⁻¹). These aerogel fibers can be knotted or woven into textiles, utilized in harsh environments (−196–400 °C), and demonstrate sensitive self-powered sensing capabilities. This method of developing aerogel fibers expands the applications of high-performance polymer fibers and holds great potential for future applications in wearable smart protective fabrics.

A poly(3-hexylthiophene)/perovskite (P3HT/PVK) heterointerface is created by using a novel strategy of spinodal decomposition, which effectively alleviates both energy and carrier losses in perovskite solar cells (PSCs). This innovative approach achieves a remarkable 24.53% power conversion efficiency for PSCs.

Abstract

The best research-cell efficiency of perovskite solar cells (PSCs) is comparable with that of mature silicon solar cells (SSCs); However, the industrial development of PSCs lags far behind SSCs. PSC is a multiphase and multicomponent system, whose consequent interfacial energy loss and carrier loss seriously affect the performance and stability of devices. Here, by using spinodal decomposition, a spontaneous solid phase segregation process, in situ introduces a poly(3-hexylthiophene)/perovskite (P3HT/PVK) heterointerface with interpenetrating structure in PSCs. The P3HT/PVK heterointerface tunes the energy alignment, thereby reducing the energy loss at the interface; The P3HT/PVK interpenetrating structure bridges a transport channel, thus decreasing the carrier loss at the interface. The simultaneous mitigation of energy and carrier losses by P3HT/PVK heterointerface enables n-i-p geometry device a power conversion efficiency of 24.53% (certified 23.94%) and excellent stability. These findings demonstrate an ingenious strategy to optimize the performance of PSCs by heterointerface via Spinodal decomposition.

A hybrid 3D printing by coupling UV-curing with direct ink writing is proposed to fabricate dense and crack-free ceramics. Non-reactive diluent relieves polymerization-induced stress, avoiding warpage and cracking, and facilitates de-binding. Benefiting from aligned platelets, this work highlights the possibilities of additively fabricating ceramics that are stronger than conventionally manufactured ceramics, along with the unprecedented potentials of locally tunable compositions.

Abstract

Additive manufacturing (AM) of high-performance structural ceramic components with comparative strength and toughness as conventionally manufactured ceramics remains challenging. Here, a UV-curing approach is integrated in direct ink writing (DIW), taking advantage from DIW to enable an easy use of high solid-loading pastes and multi-layered materials with compositional changes; while, avoiding drying problems. UV-curable opaque zirconia-based slurries with a solid loading of 51 vol% are developed to fabricate dense and crack-free alumina-toughened zirconia (ATZ) containing 3 wt% alumina platelets. Importantly, a non-reactive diluent is added to relieve polymerization-induced internal stresses, avoid subsequent warping and cracking, and facilitate the de-binding. For the first time, UV-curing assisted DIW-printed ceramic after sintering reveals even better mechanical properties than that processed by a conventional pressing. This is attributed to the aligned alumina platelets, enhancing crack deflection and improving the fracture toughness from 6.8 ± 0.3 MPa m^0.5 (compacted) to 7.4 ± 0.3 MPa m^0.5 (DIW). The four-point bending strength of the DIW ATZ (1009 ± 93 MPa) is also higher than that of the conventionally manufactured equivalent (861 ± 68 MPa). Besides homogeneous ceramic, laminate structures are demonstrated. This work provides a valuable hybrid approach to additively manufacture tough and strong ceramic components.

When mixed-halide CsPbBr_1.2I_1.8 nanocrystals are periodically heated with a temperature change of ≈10 °C, the phase-segregation effect can be completely suppressed even under strong light illumination. The above finding marks the emergence of a practical solution to the detrimental phase-segregation problem, given that a small temperature modulation is readily available in various fundamental and practical studies of mixed-halide perovskite nanocrystals.

Abstract

Under continuous light illumination, it is known that localized domains with segregated halide compositions form in semiconducting mixed-halide perovskites, thus severely limiting their optoelectronic applications due to the negative changes in bandgap energies and charge-carrier characteristics. Here mixed-halide perovskite CsPbBr_1.2I_1.8 nanocrystals are deposited onto an indium tin oxide substrate, whose temperature can be rapidly changed by ≈10 °C in a few seconds by applying or removing an external voltage. Such a sudden temperature change induces a temporary transition of CsPbBr_1.2I_1.8 nanocrystals from the segregated phase to the mixed phase, the latter of which can be permanently maintained when the light illumination is coupled with periodic heating cycles. These findings mark the emergence of a practical solution to the detrimental phase-segregation problem, given that a small temperature modulation is readily available in various fundamental studies and practical devices of mixed-halide perovskites.

The novel dual-network design strategy is proposed to prepare a high-performance cellulosic composite bioplastic metafilm with exceptional mechanical toughness (23.5 MJ m⁻³), flame retardance, and solvent resistance. Moreover, it has a high maximum usage temperature (245 °C), lower thermal expansion coefficient (15.19 ppm °C⁻¹), good biocompatibility, and natural biodegradation, which is competitive for plastic substitute.

Abstract

With the escalating environmental and health concerns over petroleum-based plastics, sustainable and biodegradable cellulosic materials are a promising alternative to plastics, yet remain unsatisfied properties such as fragility, inflammability and water sensitivity for practical usage. Herein, we present a novel dual-network design strategy to address these limitations and fabricate a high-performance cellulosic composite bioplastic metafilm with the exceptional mechanical toughness (23.5 MJ m⁻³), flame retardance, and solvent resistance by in situ growth of cyclotriphosphazene-bridged organosilica network within bacterial cellulose matrix. The phosphorus, nitrogen-containing organosilica network, verified by the experimental and theoretical results, plays a triple action on significantly enhancing tensile strength, toughness, flame retardance and water resistance of composite bioplastic metafilm. Furthermore, cellulosic bioplastic composite metafilm demonstrates a higher maximum usage temperature (245 °C), lower thermal expansion coefficient (15.19 ppm °C⁻¹), and better solvent resistance than traditional plastics, good biocompatibility and natural biodegradation. Moreover, the composite bioplastic metafilm have a good transparency of average 74 % and a high haze over 80 %, which can serve as an outstanding substrate substitute for commercial polyethylene terephthalate film to address the demand of flexible ITO films. This work paves a creative way to design and manufacture the competitive bioplastic composite to replace daily-used plastics.

A photochromic (PC) film that simultaneously regulates solar heat and visible light entrance is introduced. On a sunny day, the film tints and blocks sunlight, which reduces energy consumption for cooling and preventing excessive brightness and glare. With weak sunlight intensity, the photochromic film becomes transparent to let sunlight enter the room, which prevents additional heating and lighting energy use.

Abstract

The adaptive control of sunlight through photochromic smart windows could have a huge impact on the energy efficiency and daylight comfort in buildings. However, the fabrication of inorganic nanoparticle and polymer composite photochromic films with a high contrast ratio and high transparency/low haze remains a challenge. Here, a solution method is presented for the in situ growth of copper-doped tungsten trioxide nanoparticles in polymethyl methacrylate, which allows a low-cost preparation of photochromic films with a high luminous transparency (luminous transmittance T _lum = 91%) and scalability (30 × 350 cm²). High modulation of visible light (ΔT _lum = 73%) and solar heat (modulation of solar transmittance ΔT _sol = 73%, modulation of solar heat gain coefficient ΔSHGC = 0.5) of the film improves the indoor daylight comfort and energy efficiency. Simulation results show that low-e windows with the photochromic film applied can greatly enhance the energy efficiency and daylight comfort. This photochromic film presents an attractive strategy for achieving more energy-efficient buildings and carbon neutrality to combat global climate change.

It has already been ≈90 years since the first development of aerogels, and many researchers have devoted tremendous efforts to enhance their mechanical properties, which is yet completely achieved. This review presents multiscale, multicompositional and multidimensional strategies, resulting from flexible synthesis techniques for 0D–1D, 0D–2D, 1D–2D, and 0D–1D–2D combined aerogels.

Abstract

In recent decades, aerogels have attracted tremendous attention in academia and industry as a class of lightweight and porous multifunctional nanomaterial. Despite their wide application range, the low mechanical durability hinders their processing and handling, particularly in applications requiring complex physical structures. “Mechanically strengthened aerogels” have emerged as a potential solution to address this drawback. Since the first report on aerogels in 1931, various modified synthesis processes have been introduced in the last few decades to enhance the aerogel mechanical strength, further advancing their multifunctional scope. This review summarizes the state-of-the-art developments of mechanically strengthened aerogels through multicompositional and multidimensional approaches. Furthermore, new trends and future directions for as prevailed commercialization of aerogels as plastic materials are discussed.

A high-performance multiscale cellulose-based structural material is constructed through a multiscale interface engineering strategy. The positive and negative charges treatment of microfibers and nanofibers effectively solves the interface bonding problem in multiscale design, and allows them to be easily shaped into complex three-dimensional special-shaped structures. This sustainable material offers superior mechanical and thermal properties compared to petrochemical-based plastics.

Abstract

All-natural materials derived from cellulose nanofibers (CNFs) are expected to be used to replace engineering plastics and have attracted much attention. However, the lack of crack extension resistance and 3D formability of nanofiber-based structural materials hinders their practical applications. Here, a multiscale interface engineering strategy is reported to construct high-performance cellulose-based materials. The sisal microfibers are surface treated to expose abundant active CNFs with positive charges, thereby enhancing their interfacial combination with the negatively charged CNFs. The robust multiscale dual network enables easy molding of multiscale cellulose-based structural materials into complex 3D special-shaped structures, resulting in nearly twofold and fivefold improvements in toughness and impact resistance compared with those of CNFs-based materials. Moreover, this multiscale interface engineering strategy endows cellulose-based structural materials with better comprehensive performance than petrochemical-based plastics and broadens cellulose's potential for lightweight applications as structural materials with lower environmental effects.

Utilizing sugar-derived carbon as a dense matrix to replace petrochemicals preparing C/C composites, and this matrix exhibit a nanocrystalline graphite structure with excellent thermal stability. Sugar-derived carbon matrix C/C composite show excellent ablative resistance at 3000 °C and 10 MW m⁻² heat flux. In addition, the S–C/C is suitabile for the preparation of a large and complex shaped thermal protection component.

Abstract

Sugars are renewable resources essential to human life, but they are rarely used as raw materials for the industrial production of carbon-based materials, especially for the preparation of carbon fiber-reinforced carbon-matrix (C/C) composites, which are extremely useful for the semiconductor and aerospace sectors. Herein, a method utilizing sugar-derived carbon to replace petrochemicals as dense matrix to preparing C/C composites is reported. The matrix from sugar-derived C/C (S–C/C) composites has a nanocrystalline graphite structure that is highly thermally stable and effectively bonded to the carbon fibers. The mechanical properties of the S–C/C composite are comparable to those prepared from petrochemical sources; significantly, it exhibits a linear ablation rate of 0.03 mm s⁻¹ after 200 s of ablation at 3000 °C in 10 MW m⁻² heat flux. This new class of S–C/C is promising for use in a broad range of fields, ranging from semiconductor to aerospace.

High and controllable degrees of macroscopic orientational ordering are demonstrated for mesostructured silica, titania, and carbon films. Judicious selection of synthesis conditions enables the control of the directions and relative rates of solvent removal, surfactant self-assembly, inorganic-oxide cross-linking, and the surfaces at which mesophases grow. The materials exhibit anisotropic properties for applications in separations, catalysis, and energy conversion.

Abstract

Inorganic–organic mesophase materials provide a wide range of tunable properties, which are often highly dependent on their nano-, micro-, or meso-scale compositions and structures. Among these are macroscopic orientational order and corresponding anisotropic material properties, the adjustability of which are difficult to achieve. This is due to the complicated transient and coupled transport, chemical reaction, and surface processes that occur during material syntheses. By understanding such processes, general criteria are established and used to prepare diverse mesostructured materials with highly aligned channels with uniform nanometer dimensions and controllable directionalities over macroscopic dimensions and thicknesses. This is achieved by using a micropatterned semipermeable poly(dimethylsiloxane) stamp to manage the rates, directions, and surfaces at which self-assembling phases nucleate and the directions that they grow. This enables mesostructured surfactant-directed silica and titania composites, including with functional guest species, and mesoporous carbons to be prepared with high degrees of hexagonal order, as well as controllable orthogonal macroscopic orientational order. The resulting materials exhibit novel anisotropic properties, as demonstrated by the example of direction-dependent photocurrent generation, and are promising for enhancing the functionality of inorganic–organic nanocomposite materials in separations, catalysis, and energy conversion applications.

The CeO ₂  (100) surface , despite its strongly hydrophilic nature, exhibits hydrophobic behaviour when immersed in water. This effect is induced by the first water layer that is in immediate contact with the hydroxylated CeO₂ (100) surface. This ordered water layer creates a key-lock H-bond pattern with the underlying surface hydroxyl groups, hindering the interactions with liquid water. The hydrophobicity is manifested by a measurable water contact angle and a considerable diffusion enhancement of the confined liquid water as compared with bulk water, as reported by Lorenzo Agosta, Kersti Hermansson et al. in their Communication (e202303910). We acknowledge Virginia Carnevali for her help with the cover image.

An innovative nanofibrous hydrogel (nf-gel) constructed with constituent polymer nanofibers is proposed and fabricated using a two-step solvent-exchange method including an essential nonsolvent-quenching step. These nf-gels show remarkably enhanced mechanical properties and swelling resistance compared to their molecular counterparts. Particularly, they are isotropic, distinctly different from conventional fiber reinforced hydrogels.. .

Abstract

Nanofibrous hydrogels are pervasive in load-bearing soft tissues, which are believed to be key to their extraordinary mechanical properties. Enlighted by this phenomenon, a novel reinforcing strategy for polymeric hydrogels is proposed, where polymer segments in the hydrogels are induced to form nanofibers in situ by bolstering their controllable aggregation at the nanoscale level. Poly(vinyl alcohol) hydrogels are chosen to demonstrate the virtue of this strategy. A nonsolvent-quenching step is introduced into the conventional solvent-exchange hydrogel preparation approach, which readily promotes the formation of nanofibrous hydrogels in the following solvent-tempering process. The resultant nanofibrous hydrogels demonstrate significantly improved mechanical properties and swelling resistance, compared to the conventional solvent-exchange hydrogels with identical compositions. This work validates the hypothesis that bundling polymer chains to form nanofibers can lead to nanofibrous hydrogels with remarkably enhanced mechanical performances, which may open a new horizon for single-component hydrogel reinforcement.

Polarization Order

Polarization-switching processes of fluorite-oxide thin films remain elusive due to the challenges of visualizing oxygen ions. In article number 2207736, Chen Ge, Qinghua Zhang, Lin Gu, and co-workers directly capture the transition between ferroelectric and antiferroelectric orders using integrated differential phase-contrast scanning transmission electron microscopy.

A deep-learning-enabled intelligent design method of thermal metamaterials is proposed by using a deep generative model. To realize automatic, real-time, and customizable design of thermal metamaterials, this framework is constructed via a pre-trained deep learning model to achieve an end-to-end mapping relationship between thermal response and microstructure, which provides great flexibility in the on-demand inverse design of thermal metamaterials.

Abstract

Thermal metamaterials are mixture-based materials that are engineered to manipulate, control, and process the flow of heat, enabling numerous advanced thermal metadevices. Conventional thermal metamaterials are predominantly designed with tractable regular geometries owing to the delicate analytical solution and easy-to-implement effective structures. Nevertheless, it is challenging to achieve the design of thermal metamaterials with arbitrary geometry, letting alone intelligent (automatic, real-time, and customizable) design of thermal metamaterials. Here, an intelligent design framework of thermal metamaterials is presented via a pre-trained deep learning model, which gracefully achieves the desired functional structures of thermal metamaterials with exceptional speed and efficiency, regardless of arbitrary geometry. It possesses incomparable versatility and is of great flexibility to achieve the corresponding design of thermal metamaterials with different background materials, anisotropic geometries, and thermal functionalities. The transformation thermotics-induced, freeform, background-independent, and omnidirectional thermal cloaks, whose structural configurations are automatically designed in real-time according to shape and background, are numerically and experimentally demonstrated. This study sets up a novel paradigm for an automatic and real-time design of thermal metamaterials in a new design scenario. More generally, it may open a door to the realization of an intelligent design of metamaterials in also other physical domains.

A novel lightweight Al battery is constructed using a dendrite-free carbon aerogel film (CAF) anode and a high-loading integrated graphite composite carbon aerogel film (GCAF) cathode. O-containing functional groups on the CAF induce Al deposition. The zero-volume expansion of the GCAF results in better stability. A CAF‖GCAF full battery exhibits excellent charge–discharge performance toward fast storage of fluctuating electricity.

Abstract

Al batteries have great potential for renewable energy storage owing to their low cost, high capacity, and safety. High energy density and adaptability to fluctuating electricity are major challenges. Here, a lightweight Al battery for fast storage of fluctuating energy is constructed based on a novel hierarchical porous dendrite-free carbon aerogel film (CAF) anode and an integrated graphite composite carbon aerogel film (GCAF) cathode. A new induced mechanism by the O-containing functional groups on the CAF anode is con-firmed for uniform Al deposition. The GCAF cathode possesses a higher mass utilization ratio due to the extremely high loading mass (9.5–10.0 mg cm⁻²) of graphite materials compared to conventional coated cathodes. Meanwhile, the volume expansion of the GCAF cathode is almost negligible, resulting in better cycling stability. The lightweight CAF‖GCAF full battery can adapt well to large and fluctuating current densities owing to its hierarchical porous structure. A large discharge capacity (115.6 mAh g⁻¹) after 2000 cycles and a short charge time (7.0 min) at a high current density are obtained. The construction strategy of lightweight Al batteries based on carbon aerogel electrodes can promote the breakthrough of high-energy-density Al batteries adapted to the fast storage of fluctuating renewable energy.

Nature Materials, Published online: 28 June 2023; doi:10.1038/s41563-023-01602-4

A bicontinuous conducting polymer hydrogel with high electrical conductivity, stretchability and fracture toughness in physiological environments achieves high-fidelity monitoring and effective stimulation of tissues and organs.

A rapid synthesis method is developed to introduce Zr-MOF nanozyme coating into cellulose nanofibers, resulting in the formation of processable macro-micro porous aerogel composites with high metal–organic framework (MOF) loadings. The hierarchically structured MOF nanozymes monolithic aerogel enables excellent accessibility to catalytic active sites for fast and efficient hydrolytic detoxification of organophosphorus-based nerve agent simulants and pesticides from contaminated water.

Abstract

Metal–organic frameworks (MOFs) with Lewis acid catalytic sites, such as zirconium-based MOFs (Zr-MOFs), comprise a growing class of phosphatase-like nanozymes that can degrade toxic organophosphate pesticides and nerve agents. Rationally engineering and shaping MOFs from as-synthesized powders into hierarchically porous monoliths is essential for their use in emerging applications, such as filters for air and water purification and personal protection gear. However, several challenges still limit the production of practical MOF composites, including the need for sophisticated reaction conditions, low MOF catalyst loadings in the resulting composites, and poor accessibility to MOF-based active sites. To overcome these limitations, a rapid synthesis method is developed to introduce Zr-MOF nanozyme coating into cellulose nanofibers, resulting in the formation of processable monolithic aerogel composites with high MOF loadings. These composites contain Zr-MOF nanozymes embedded in the structure, and hierarchical macro-micro porosity enables excellent accessibility to catalytic active sites. This multifaceted rational design strategy, including the selection of a MOF with many catalytic sites, fine-tuning the coating morphology, and the fabrication of a hierarchically structured monolithic aerogel, renders synergistic effects toward the efficient continuous hydrolytic detoxification of organophosphorus-based nerve agent simulants and pesticides from contaminated water.

Thermal conductivity imaging via frequency-domain thermoreflectance enables the detection of localized microscale suppression in thermal conductivity at the grain boundaries of thermoelectric SnTe. By employing a Gibbs excess approach, a thermal boundary resistance is extracted from the images, establishing a correlation between misorientation angle and thermal resistance. These findings demonstrate the capability of thermal imaging in extracting structure–property relationships.

Abstract

Grain-boundary engineering is an effective strategy to tune the thermal conductivity of materials, leading to improved performance in thermoelectric, thermal-barrier coatings, and thermal management applications. Despite the central importance to thermal transport, a clear understanding of how grain boundaries modulate the microscale heat flow is missing, owing to the scarcity of local investigations. Here, thermal imaging of individual grain boundaries is demonstrated in thermoelectric SnTe via spatially resolved frequency-domain thermoreflectance. Measurements with microscale resolution reveal local suppressions in thermal conductivity at grain boundaries. Also, the grain-boundary thermal resistance – extracted by employing a Gibbs excess approach – is found to be correlated with the grain-boundary misorientation angle. Extracting thermal properties, including thermal boundary resistances, from microscale imaging can provide comprehensive understanding of how microstructure affects heat transport, crucially impacting the materials design of high-performance thermal-management and energy-conversion devices.

Au atoms tend to form a thin, crystalline layer on graphene surfaces via van der Waals epitaxy, resulting in translucent, conductive films. Translucent yet reflective Au/graphene hybrids are invisible to the naked eye but can be clearly identified at IR wavelength. Au/graphene hybrids can be applied to a wide range of thermal management applications ranging from energy harvesting and storage to military applications.

Abstract

Translucent Au/graphene hybrid films are shown to be effective in reducing thermal emission from the underlying surfaces when the deposition thickness of Au is close to the percolation threshold. The critical Au deposition thickness for an abrupt change in emissivity is reduced from 15 nm (Si substrate) to a percolation-threshold-limited thickness of 8.5 nm (graphene/Si substrate) because of the chemical inertness of graphene leading to the deposited Au atoms forming a thin, crystalline layer. The effect of the graphene layer on the optical properties of the hybrid film is highlighted by a drastic increase in infrared absorptivity, whereas the visible absorptivity is marginally affected by the presence of a graphene layer. The level of thermal emission from the Au/graphene hybrid films with the percolation-threshold-limited Au thickness is stable even with high background temperatures of up to 300 °C and mechanical strains of ≈4%. As an example of a thermal management application, an anti-counterfeiting device is demonstrated; thermal-camouflage-masked text fabricated with an Au/graphene hybrid film is discernible only using a thermographic camera. Ultrathin metal film assisted by a graphene layer will provide a facile platform for thermal management with semi-transparency, flexibility, and transferability to arbitrary surfaces.

High-temperature thermochromic fluorescence up to 473 K and robust structural and optical reversibility of 80 cycles are demonstrated in Rb₂MnBr₄(H₂O)₂ and related crystals. Such unique features showcase a multicolor anti-counterfeiting label based on a broad temperature gradient and multidimensional information encryption application.

Abstract

Thermochromic fluorescent materials (TFMs) characterized by noticeable emission color variation with temperature have attracted pervasive attention for their frontier application in stimulus-response and optical encryption technologies. However, existing TFMs typically suffer from weak PL reversibility as well as limited mild operating temperature and severe temperature PL quenching. PL switching under extreme conditions such as high temperature will undoubtedly improve encryption security, while it is still challenging for present TFMs. In this work, high-temperature thermochromic fluorescence up to 473 K and robust structural and optical reversibility of 80 cycles are observed in Rb₂MnBr₄(H₂O)₂ and related crystals, which is seldom reported for PL changes at such a high temperature. Temperature-driven nonluminous, red and green light emission states can be achieved at specific temperatures and the modulation mechanism is verified by in situ optical and structural measurements and single particle transition. By virtue of this unique feature, a multicolor anti-counterfeiting label based on a broad temperature gradient and multidimensional information encryption applications are demonstrated. This work opens a window for the design of inorganic materials with multi-PL change and the development of advanced encryption strategies with extreme stimuli source.

A “dynamic covalent network” reconstruction strategy is proposed for the fabrication of sustainable cellulosic bioplastics. By introducing dynamic linkages between cellulose chains, this cellulosic bioplastic is imparted with good thermo-processability, competitive mechanical properties, excellent water and solvent resistance, as well as chemical and biological degradability. This approach provides a new route for developing sustainable and degradable bioplastics from resource-abundant biomass.

Abstract

The growing environmental concern over petrochemical-based plastics continuously promotes the exploration of green and sustainable substitute materials. Compared with petrochemical products, cellulose has overwhelming superiority in terms of availability, cost, and biodegradability; however, cellulose's dense hydrogen-bonding network and highly ordered crystalline structure make it hard to be thermoformed. A strategy to realize the partial disassociation of hydrogen bonds in cellulose and the reassembly of cellulose chains via constructing a dynamic covalent network, thereby endowing cellulose with thermal processability as indicated by the observation of a moderate glass transition temperature (T _g = 240 °C), is proposed. Moreover, the cellulosic bioplastic delivers a high tensile strength of 67 MPa, as well as excellent moisture and solvent resistance, good recyclability, and biodegradability in nature. With these advantageous features, the developed cellulosic bioplastic represents a promising alternative to traditional plastics.

This work builds a modeling method from the atomic scale to the macroscale for porous electrodes. Simulations reveal that supercapacitors based on porous graphdiynes of AB stacking structure can achieve both higher capacitance and ionic conductivity than AA stacking. This is ascribed to more intense image forces in AB stacking.

Abstract

Porous graphdiynes are a new class of porous 2D materials with tunable electronic structures and various pore structures. They have potential applications as well-defined nanostructured electrodes and can provide platforms for understanding energy storage mechanisms underlying supercapacitors. Herein, the effect of stacking structure and metallicity on energy storage with such electrodes is investigated. Simulations reveal that supercapacitors based on porous graphdiynes of AB stacking structure can achieve both higher double-layer capacitance and ionic conductivity than AA stacking. This phenomenon is ascribed to more intense image forces in AB stacking, leading to a breakdown of ionic ordering and the formation of effective “free ions”. Macroscale analysis shows that doped porous graphdiynes can deliver outstanding gravimetric and volumetric energy and power densities due to their enhanced quantum capacitance. These findings pave the way for designing high-performance supercapacitors by regulating pore topology and metallicity of electrode materials.