Yunxiang Bai

The strength of carbon nanotube (CNT) bundles and fibers is generally much lower than that of single CNTs, the short length of CNT components results in the assembly strength can only be contributed by the weak shearing interaction between CNTs. Here, the welding of CNTs by a fast chemical‐vapor‐deposition self‐assembly (FCVDS) technique using TiO ₂ nanoparticles as the solder is reported. It is simple, fast, pressure‐free, applicable to ambient conditions, and can weld samples with macroscale length. The welded junctions have a mechanical strength approaching the tensile strength of a single CNT. Whereas the interface interaction between TiO ₂ and CNTs is only contributed by Van der Waals forces, avoiding the destruction of the defect‐free structure of CNTs. The solder mass can be only ≈1 wt% of welded CNTs.

Low‐dimensional ultra‐strong nanomaterials have attracted great anticipation for applications under extreme dynamic conditions. A photocatalytic method is developed to selectively cut off the outer shell of double‐walled carbon nanotubes (DWCNTs), achieving non‐contact measurement of intershell friction with both high temporal and spatial resolutions at high sliding velocities under optical microscope. The intershell friction linearly increases with the sliding velocity, with a slope related to intershell distance and chirality of DWCNTs. The maximum measured friction reaches 194.1 ± 7.3 nN at a sliding velocity of 977 mm s⁻¹, a value comparable to the tensile force (≈450 nN) for breaking the outer shell. Molecular dynamics simulations indicate that the velocity‐dependent intershell friction is related to dynamic localized commensurate contacts. The friction‐induced “intershell locking” enhances the effective dynamic strength of DWCNTs from 64.8 ± 3.4 GPa to 90.1 ± 4.0 GPa at a tensile strain rate of 3300 s⁻¹. This study reveals anomalous friction mechanisms at nanoscale and demonstrates promising application of DWCNTs as ultra‐strong materials.

We fabricated a composite laminate consisting of 1000 layers of SA-CNTFs and 1 layer of zirconia fiber, effectively shielding CFRP from 100 kA lightning strikes. Furthermore, the lightning strike protection mechanism was thoroughly investigated.

The fabrication of light-weight, highly impact-resistant, and energy-absorbent materials is urgently demanded in many facets of the society from body armor to aerospace engineering, especially under an extreme environment. Carbon nanotubes (CNTs), one of the strongest and toughest materials ever found, also have good conductivity, chemical stability, and thermal stability, etc, making them a competitive candidate as building blocks to help achieve the above goal. In this work, a kind of CNT network was prepared by using chlorosulfonic acid (CSA) to release the internal stress of super-aligned carbon nanotube films (SA-CNTF) and dendritic polyamide amine (PAMAM) to further introduce multiple hydrogen bonds and interlocking structures. The fabricated bioinspired carbon nanotube network films (PAMAM@C-CNTF) have a high toughness of 45.97 MJ/m³, showing an increase of 420% compared to neat SA-CNTF. More importantly, the anti-impact performance of the films (e.g., with a maximum specific energy absorption of 1.40 MJ/kg under 80–100 m/s projectile impact) is superior to that of conventional protective materials from steel and Kevlar fiber, and also exceeds that of any other reported carbon-based materials. The hierarchical energy dissipation mechanism was further revealed through experiment and simulation. Additional functions including intelligent heating/anti-icing, ultraviolet protection, as well as electromagnetic interference shielding properties make these network films have great potential in practical multi-protection applications, especially under an extreme environment.

The exploration of material failure behavior not only involves defining its limits and underlying mechanisms but also entails devising strategies for improvement and protection in extreme conditions. We’ve pioneered an advanced multi-scale, high-speed ascending thermal shock testing platform capable of inducing unprecedented heat shocks at rates surpassing 10⁵ °C/s. Through meticulous examination of the thermal shock responses of carbon nanotube (CNT) films, we’ve achieved remarkable breakthroughs. By employing an innovative macro-scale synchronous tightening and relaxing approach, we’ve attained a critical temperature differential in CNT films that exceeds an exceptional 2500 °C—surpassing any previously reported metric for high-performance, thermal-shock-resistant materials. Notably, these samples have demonstrated exceptional resilience, retaining virtually unchanged strength even after enduring 10,000 thermal shock cycles at temperatures exceeding 1000 °C. Furthermore, our research has revealed a novel thermal shock/fatigue failure mechanism that fundamentally diverges from conventional theories centered on thermal stress.

The study of material failure is crucial for the design of engineering applications, as it can have significant social and economic impacts. Carbon nanotubes (CNTs), with their exceptional electrical, mechanical, and thermal properties, hold immense potential for a wide range of cutting-edge applications such as superstrong fiber, lightning strike protector, and even space elevator. This review provides an overview of the advancement in understanding the mechanical and electrical failure study of CNTs and their assemblies, serving as a comprehensive reference for utilizing CNTs in various forms. To begin, we emphasize the importance of studying material failure and provide a brief introduction to CNTs. Subsequently, we explore the mechanical and electrical failure characteristics of CNTs and their assemblies, along with notable examples of applications that utilize their failure-resistant properties, such as flywheel energy storage and lightning strike protection. Lastly, we present perspectives associated with analyzing CNT failure and its implications for extreme applications.

Carbon nanotubes (CNTs) with superior mechanical properties are expected to play a role in the next generation of critical engineering mechanical materials. Crucial advances have been made in CNTs, as it has been reported that the tensile strength of defect-free CNTs and carbon nanotube bundles can approach the theoretical limit. However, the tensile strength of macro carbon nanotube fibers (CNTFs) is far lower than the theoretical level. Although some reviews have summarized the development of such fiber materials, few of them have focused on the controllable preparation and performance optimization of high-strength CNTFs at different scales. Therefore, in this review, we will analyze the characteristics and latest challenges of multiscale CNTFs in preparation and strength optimization. First, the structure and preparation of CNTs are introduced. Then, the preparation methods and tensile strength characteristics of CNTFs at different scales are discussed. Based on the analysis of tensile fracture, we summarize some typical strategies for optimizing tensile performance around defect and tube–tube interaction control. Finally, we introduce some emerging applications for CNTFs in mechanics. This review aims to provide insights and prospects for the controllable preparation of CNTFs with ultra-high tensile strength for emerging cutting-edge applications.

Carbon nanotubes (CNTs) possess a unique tubular structure composed of highly graphitized atoms. Since their sp² hybridized skeleton is discovered under the microscope, extensive attention is paid to their peculiar physics and extraordinary performances in mechanics, optics, and electricity. However, due to the challenges in controlled synthesis and mass production, there is a long bottleneck period in both the science and engineering of CNTs. In the recent decade, significant advances have emerged in ton‐scale production, 3D microprocessors, ultrastrong fibers, etc., which have pushed the renaissance of CNTs toward a new peak. This important progress benefits from the critical but commonly ignored breakthroughs in the precise structure control and assembly of CNTs. Herein, the morphological manipulation and technical routes toward the CNT industry will be focused on. First, the growth mechanism of defect‐free aligned CNTs will be discussed. Subsequently, nondestructive flow‐guided fabrication methods and their application paradigms are summarized. Then, attention will be turned to assembly‐based industrial production and applications of CNTs. Some research prospects toward the precise synthesis and CNT industry are proposed at last, in the hope of building a comprehensive understanding on the catalytic assembly toward defect‐free nanostructures and their high‐end applications.

Finding the source of their durability: Many high-strength materials can fail after repeated exposure to subcritical loading; therefore, understanding the causes of fatigue is key to extending the longevity of the material in use. Bai et al. used chemical vapor deposition to produce centimeter-long carbon nanotubes. They then decorated these nanotubes with titanium dioxide nanoparticles for optical visualization and studied them using noncontact acoustic resonance tests. The authors determined that fatigue lifetime is dependent on the formation of the first defects on straining and is higher at lower temperatures. Science , this issue p. 1104