Energy efficient buildings require materials with a low thermal conductivity and a high fire resistance. Traditional organic insulation materials are limited by their poor fire resistance and ...inorganic insulation materials are either brittle or display a high thermal conductivity. Herein we report a mechanically resilient organic/inorganic composite aerogel with a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance. Co‐polymerization and nanoscale phase separation of the phenol‐formaldehyde‐resin (PFR) and silica generate a binary network with domain sizes below 20 nm. The PFR/SiO2 aerogel can resist a high‐temperature flame without disintegration and prevents the temperature on the non‐exposed side from increasing above the temperature critical for the collapse of reinforced concrete structures.
Fire not starter: Taking advantage of a co‐polymerization strategy an organic–inorganic binary network hybrid aerogel with a nanoscale homogeneity can be prepared. The phenol‐formaldehyde‐resin/SiO2 aerogel is mechanically resilient and has a thermal conductivity significantly lower than expanded polystyrene and excellent fire resistance.
Abstract
Tuning metal–support interaction has been considered as an effective approach to modulate the electronic structure and catalytic activity of supported metal catalysts. At the atomic level, ...the understanding of the structure–activity relationship still remains obscure in heterogeneous catalysis, such as the conversion of water (alkaline) or hydronium ions (acid) to hydrogen (hydrogen evolution reaction, HER). Here, we reveal that the fine control over the oxidation states of single-atom Pt catalysts through electronic metal–support interaction significantly modulates the catalytic activities in either acidic or alkaline HER. Combined with detailed spectroscopic and electrochemical characterizations, the structure–activity relationship is established by correlating the acidic/alkaline HER activity with the average oxidation state of single-atom Pt and the Pt–H/Pt–OH interaction. This study sheds light on the atomic-level mechanistic understanding of acidic and alkaline HER, and further provides guidelines for the rational design of high-performance single-atom catalysts.
Superelastic carbon aerogels have been widely explored by graphitic carbons and soft carbons. These soft aerogels usually have delicate microstructures with good fatigue resistance but ultralow ...strength. Hard carbon aerogels show great advantages in mechanical strength and structural stability due to the sp3‐C‐induced turbostratic “house‐of‐cards” structure. However, it is still a challenge to fabricate superelastic hard carbon‐based aerogels. Through rational nanofibrous structural design, the traditional rigid phenolic resin can be converted into superelastic hard carbon aerogels. The hard carbon nanofibers and abundant welded junctions endow the hard carbon aerogels with robust and stable mechanical performance, including superelasticity, high strength, extremely fast recovery speed (860 mm s−1), low energy‐loss coefficient (<0.16), long cycle lifespan, and heat/cold‐endurance. These emerging hard carbon nanofiber aerogels hold a great promise in the application of piezoresistive stress sensors with high stability and wide detection range (50 kPa), as well as stretchable or bendable conductors.
A family of hard carbon aerogels with nanofibrous structure templated by various nanofibers is fabricated, displaying robust and stable mechanical performances, including high strength, extremely fast recovery speed (860 mm s−1), and ultralow energy loss coefficient (<0.16). After being compressed for 104 cycles (50% strain), they show only ≈2% plastic deformation and retain ≈93% stress.
Photon loss in optical fibers prevents long-distance distribution of quantum information on the ground. Quantum repeater is proposed to overcome this problem, but the communication distance is still ...limited so far because of the system complexity of the quantum repeater scheme. Alternative solutions include transportable quantum memory and quantum-memory-equipped satellites, where long-lived optical quantum memories are the key components to realize global quantum communication. However, the longest storage time of the optical memories demonstrated so far is approximately 1 minute. Here, by employing a zero-first-order-Zeeman magnetic field and dynamical decoupling to protect the spin coherence in a solid, we demonstrate coherent storage of light in an atomic frequency comb memory over 1 hour, leading to a promising future for large-scale quantum communication based on long-lived solid-state quantum memories.
As an abundant natural resource, wood has gained great attention for thousands of years, spanning from the primitive construction materials to the modern high‐added‐value engineering materials. The ...unique delicate microstructures and the wonderful properties (e.g., low‐density, high strength and stiffness, good toughness, and environmental sustainability) have made wood a natural source of inspiration that guides researchers to invent various wood‐inspired materials. Herein, as an emerging material system, bioinspired artificial wood, with similar cellular structures and comparable mechanical properties, is discussed in the view of the design concept, fabrication strategy, properties, and possible applications. The present challenges and further research opportunities are also presented for artificial woods to thrive. To achieve the final eco‐friendly artificial wood, more endeavors should be made in biomaterials and biodegradable or recyclable engineering of polymers to gain high mechanical properties and environmental sustainability simultaneously.
Artificial woods have emerged as a novel kind of wood‐inspired engineering material with almost exactly the same channel microstructures and similar wall components. The performances of artificial woods depend on both the oriented channel and wall designs. The rational combination of other engineering polymers and channel‐making techniques hold promise to develop more useful artificial woods.
Developing coordination complexes (such as metal–organic frameworks, MOFs) with circularly polarized luminescence (CPL) is currently attracting tremendous attention and remains a significant ...challenge in achieving MOF with circularly polarized afterglow. Herein, MOFs‐based circularly polarized afterglow is first reported by combining the chiral induction approach and tuning the afterglow times by using the auxiliary ligands regulation strategy. The obtained chiral R/S‐ZnIDC, R/S‐ZnIDC(bpy), and R/S‐ZnIDC(bpe)(IDC = 1H‐Imidazole‐4,5‐dicarboxylate, bpy = 4,4′‐Bipyridine, bpe = trans‐1,2‐Bis(4‐pyridyl) ethylene) containing a similar structure unit display different afterglow times with 3, 1, and <0.1 s respectively which attribute to that the longer auxiliary ligand hinders the energy transfer through the hydrogen bonding. The obtained chiral complexes reveal a strong chiral signal, obvious photoluminescence afterglow feature, and strong CPL performance (glum up to 3.7 × 10−2). Furthermore, the photo‐curing 3D printing method is first proposed to prepare various chiral MOFs based monoliths from 2D patterns to 3D scaffolds for anti‐counterfeiting and information encryption applications. This work not only develops chiral complexes monoliths by photo‐curing 3D printing technique but opens a new strategy to achieve tunable CPL afterglow in optical applications.
Chiral metal‐organic frameworks (MOFs) nanoparticles with different afterglow times are prepared by combining chiral induction approach and auxiliary ligands regulation strategy, displaying tunable circularly polarized luminescence afterglow performance. Furthermore, the corresponding chiral MOFs nanoparticles are first prepared to various chiral monoliths by photo‐curing 3D printing technology for anti‐counterfeiting and information encryption applications.
Abstract
Regulating nonlinear optical (NLO) property of metal−organic frameworks (MOFs) is of pronounced significance for their scientific research and practical application, but the regulation ...through external stimuli is still a challenging task. Here we prepare and electrically control the nonlinear optical regulation of conductive MOFs Cu-HHTP films with 001- (Cu-HHTP
001
) and 100-orientations (Cu-HHTP
100
). Z-scan results show that the nonlinear absorption coefficient (
β
) of Cu-HHTP
001
film (7.60 × 10
−6
m/W) is much higher than that of Cu-HHTP
100
film (0.84 × 10
−6
m/W) at 0 V and the
β
of Cu-HHTP
001
and Cu-HHTP
100
films gradually increase to 3.84 × 10
−5
and 1.71 × 10
−6
m/W at 10 V by increasing the applied voltage, respectively. Due to 2D Cu-HHTP having anisotropy of charge transfer in different orientations, the NLO of MOFs film can be dependent on their growth orientations and improved by tuning the electrical field. This study provides more avenues for the regulation and NLO applications of MOFs.
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•Morphology and defect engineering are used to improve the photocatalytic activity of materials.•Defect strategy can enhance the activation of molecular oxygen.•The structure-inducing ...strategy of BiOCl {110} facet exposure was explained at the molecular level.•BiOCl (110)-OV showed excellent photocatalytic activity and reusability.•Based on the experiments and DFT calculations, the mechanism of photodegradation is explained.
Because of different atomic arrangements and/or different exposed atoms on different surfaces of crystalline particles, different physical and chemical properties can be resulted and exhibited. In this work, we prepared BiOCl with {110} crystal facet by introducing urea as the structure-directing agent, and constructed oxygen vacancies (OVs) in BiOCl (110) to form BiOCl (110)-OV. Control of exposure surface can improve photocatalyst activity and the defect level caused by OVs can improve charge separation and light absorption, thereby further enhancing the production of free radicals and the activation of pollutants. Due to the synergistic effect of the hierarchical microsphere structure of BiOCl and OVs, the degradation rate of tetracycline hydrochloride (20 mg/L) in the presence of BiOCl (110)-OV can reach 95.1% after 15 min of the simulated sunlight illumination. This research provides novel ideas for the design and development of photocatalyst with hierarchical structure and oxygen vacancy defects.
Soft woods have attracted enormous interest due to their anisotropic cellular microstructure and unique flexibility. The conventional wood-like materials are usually subject to the conflict between ...the superflexibility and robustness. Inspired by the synergistic compositions of soft suberin and rigid lignin of cork wood which has good flexibility and mechanical robustness, an artificial soft wood is reported by freeze-casting the soft-in-rigid (rubber-in-resin) emulsions, where the carboxy nitrile rubber confers softness and rigid melamine resin provides stiffness. The subsequent thermal curing induces micro-scale phase inversion and leads to a continuous soft phase strengthened by interspersed rigid ingredients. The unique configuration ensures crack resistance, structural robustness and superb flexibility, including wide-angle bending, twisting, and stretching abilities in various directions, as well as excellent fatigue resistance and high strength, overwhelming the natural soft wood and most wood-inspired materials. This superflexible artificial soft wood represents a promising substrate for bending-insensitive stress sensors.
In the paper, a novel magneto-electro-elastic model of bi-directional (2D) functionally graded materials (FGMs) beams is developed for investigating the nonlinear dynamics. It is shown that the ...asymmetric modes induced by the 2D FGMs may significantly affect the nonlinear dynamic responses, which is tremendously different from previous studies. Taking into account the geometric nonlinearity, the nonlinear equation of motion and associated boundary conditions for the beams are derived according to the Hamilton’s principle. The natural frequencies and numerical modes of the beams are calculated by the generalized differential quadrature method. The frequency responses of the nonlinear forced vibration are constructed based on the Galerkin technique incorporating with the incremental harmonic balance approach. The influences of the material distributions, length–thickness ratio, electric voltage, magnetic potential as well as boundary condition on the nonlinear resonant frequency and response amplitude are discussed in details. It is notable that increasing in the axial and thickness FG indexes, negative electric potential and positive magnetic potential can lead to decline the nonlinear resonance frequency and amplitude peak, which is usually applied to accurately design the multi-ferroic composite structures. Furthermore, the nonlinear characteristics of motion can be regulated by tuning/tailoring the 2D FG materials.
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