Jiuxiang Dai

Nature Materials, Published online: 19 December 2022; doi:10.1038/s41563-022-01424-w

Nature Communications, Published online: 19 December 2022; doi:10.1038/s41467-022-35278-2

This review presents the major findings in the past two decades of the studies on carbon nanotubes (CNTs) modified fiber reinforced plastics (FRPs). It reveals that incorporating CNTs can elevate the tensile, flexural and impact properties significantly and enhance the fiber-matrix interface. Reinforcement and toughening mechanisms in CNTs modified FRPs are proposed to inspire the future development of high-performance FRPs.

Abstract

Carbon nanotubes (CNTs) are an economical and multi-functional nanofiller that can further elevate the versatile performance of fiber-reinforced polymer (FRP). The past two decades have seen significant progress in the design, fabrication, and characterization of CNTs modified FRPs (CNT-FRPs). The introduction of CNTs has been proven to enhance the key mechanical properties of CNT-FRPs and endow the composite with additional functional properties. In this review, the fabrication routes of CNT incorporation into FRPs are first discussed, and then the critical effects of CNTs on various mechanical properties of CNT-FRPs are described. Next, as a complement to the experimental results, modeling studies on CNT-FRPs are included to reveal the underlying structural effects, followed by a discussion on the reinforcement and toughening mechanisms of CNT-FRPs. The intent of this review is to provide a comprehensive summary on CNT modified FRP composites, and to shed light on the future research and development of CNT modified composites.

The horizontal mirror symmetry in BaAgSb vanishes the electron–phonon coupling mediated by phonons with purely out-of-plane vibrational vectors, which weakens the phonon-induced carrier scattering and triggers a record hole mobility among polycrystalline quasi-2D thermoelectrics. Such high mobility accompanied with intrinsically low thermal conductivity gives rise to excellent p-type thermoelectric performance in polycrystalline BaAgSb.

Abstract

Quasi-2D semiconductors have garnered immense research interest for next-generation electronics and thermoelectrics due to their unique structural, mechanical, and transport properties. However, most quasi-2D semiconductors experimentally synthesized so far have relatively low carrier mobility, preventing the achievement of exceptional power output. To break through this obstacle, a route is proposed based on the crystal symmetry arguments to facilitate the charge transport of quasi-2D semiconductors, in which the horizontal mirror symmetry is found to vanish the electron–phonon coupling strength mediated by phonons with purely out-of-plane vibrational vectors. This is demonstrated in ZrBeSi-type quasi-2D systems, where the representative sample Ba_1.01AgSb shows a high room-temperature hole mobility of 344 cm² V⁻¹ S⁻¹, a record value among quasi-2D polycrystalline thermoelectrics. Accompanied by intrinsically low thermal conductivity, an excellent p-type zT of ≈1.3 is reached at 1012 K, which is the highest value in ZrBeSi-type compounds. This work uncovers the relation between electron–phonon coupling and crystal symmetry in quasi-2D systems, which broadens the horizon to develop high mobility semiconductors for electronic and energy conversion applications.

2D copper-based materials with different systems of Cu–O, Cu–S, Cu–Se, Cu–N, and Cu–P have triggered tremendous research because of the remarkable combination of properties. This review concentrates on recent research progress in 2D copper-based materials applications in electrochemical energy storage and conversion.

Abstract

2D materials have shown great potential as electrode materials that determine the performance of a range of electrochemical energy technologies. Among these, 2D copper-based materials, such as Cu–O, Cu–S, Cu–Se, Cu–N, and Cu–P, have attracted tremendous research interest, because of the combination of remarkable properties, such as low cost, excellent chemical stability, facile fabrication, and significant electrochemical properties. Herein, the recent advances in the emerging 2D copper-based materials are summarized. A brief summary of the crystal structures and synthetic methods is started, and innovative strategies for improving electrochemical performances of 2D copper-based materials are described in detail through defect engineering, heterostructure construction, and surface functionalization. Furthermore, their state-of-the-art applications in electrochemical energy storage including supercapacitors (SCs), alkali (Li, Na, and K)-ion batteries, multivalent metal (Mg and Al)-ion batteries, and hybrid Mg/Li-ion batteries are described. In addition, the electrocatalysis applications of 2D copper-based materials in metal–air batteries, water-splitting, and CO₂ reduction reaction (CO₂RR) are also discussed. This review also discusses the charge storage mechanisms of 2D copper-based materials by various advanced characterization techniques. The review with a perspective of the current challenges and research outlook of such 2D copper-based materials for high-performance energy storage and conversion applications is concluded.

The emerging amorphous-crystalline heterostructures with distinctive atomic arrangement at the heterointerfaces are promising candidates for next-generation high-performance electrocatalysts/electrodes. This review discusses for the first time these ever-increasing novel multifunctional nanomaterials toward various electrochemical applications, aiming to offer cross-sectional insights into the structure-property relationships and provide guidance for the rational design of amorphous-crystalline heterostructures with desired performance.

Abstract

Interface engineering of heterostructures has proven a promising strategy to effectively modulate their physicochemical properties and further improve the electrochemical performance for various applications. In this context related research of the newly proposed amorphous-crystalline heterostructures have lately surged since they combine the superior advantages of amorphous- and crystalline-phase structures, showing unusual atomic arrangements in heterointerfaces. Nonetheless, there has been much less efforts in systematic analysis and summary of the amorphous-crystalline heterostructures to examine their complicated interfacial interactions and elusory active sites. The critical structure-activity correlation and electrocatalytic mechanism remain rather elusive. In this review, the recent advances of amorphous-crystalline heterostructures in electrochemical energy conversion and storage fields are amply discussed and presented, along with remarks on the challenges and perspectives. Initially, the fundamental characteristics of amorphous-crystalline heterostructures are introduced to provide scientific viewpoints for structural understanding. Subsequently, the superiorities and current achievements of amorphous-crystalline heterostructures as highly efficient electrocatalysts/electrodes for hydrogen evolution reaction, oxygen evolution reaction, supercapacitor, lithium-ion battery, and lithium-sulfur battery applications are elaborated. At the end of this review, future outlooks and opportunities on amorphous-crystalline heterostructures are also put forward to promote their further development and application in the field of clean energy.

Controlling and tuning the orbital ordering in a single molecule using a monolayer ferroelectric substrate is realized. This is achieved by adsorbing transition metal phthalocyanine (TMPc) molecules on a ferroelectric monolayer SnTe. The orbital order is probed using low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy experiments, and it is demonstrated that it can be controllably changed by switching the polarization direction of the underlying ferroelectric monolayer.

Abstract

2D ferroelectric materials provide a promising platform for the electrical control of quantum states. In particular, due to their 2D nature, they are suitable for influencing the quantum states of deposited molecules via the proximity effect. Here, electrically controllable molecular states in phthalocyanine molecules adsorbed on monolayer ferroelectric material SnTe are reported. The strain and ferroelectric order in SnTe are found to create a transition between two distinct orbital orders in the adsorbed phthalocyanine molecules. By controlling the polarization of the ferroelectric domain using scanning tunneling microscopy (STM), it is successfully demonstrated that orbital order can be manipulated electrically. The results show how ferroelastic coupling in 2D systems allows for control of molecular states, providing a starting point for ferroelectrically switchable molecular orbital ordering and ultimately, electrical control of molecular magnetism.

This review focuses on an attractive class of polymer-derived high-temperature nonoxide materials. The important parameters related to polycarbosilane pyrolysis are explained. Also, polymer-derived solid-solution carbides, transition metal carbides, transition metal borides, nitrides, and high-temperature nonoxide composites are examined. Finally, an overview of applications of polymer-derived nonoxides is provided, followed by a summary and outlook.

This review is focused on an attractive class of polymer-derived high-temperature ceramics, namely, polymer-derived nonoxide materials. With a brief introduction of high-temperature nonoxides, the origin of using polycarbosilane (PCS) polymer melt spinning to synthesize silicon carbide (SiC) fibers is traced back. For SiC formation, the four stages for the conversion from polymer precursors to microcrystalline ceramics are examined first: crosslinking, polymer decomposition, ceramic formation, and crystallization. Also, the important parameters related to PCS pyrolysis are explained, and polymer-derived SiC microstructures and compositions are evaluated. Solid-solution carbides and transition metal carbides are further reviewed. For boride materials, the discussion is focused on transition metal borides and boride composites. Similar to PCS conversion to SiC, nitride materials mostly start with polycarbosilazane (PSZ) precursors and form into the final materials through pyrolysis. With different carbide and nitride precursors mixed and pyrolyzed together, high-temperature nonoxide composites are formed. Such molecular-level intermixing and versatile capability of forming different shapes enable many exciting properties. Among these are mechanical and thermal properties, along with electrical conductivity, electromagnetic shielding, and charge storage capability. An overview of applications of polymer-derived nonoxides is provided, followed by a summary and outlook.