High surface area carbon aerogels as porous substrates for direct growth of carbon nanotubes

Spatially confined growth of carbon nanotubes in the pore channels of microporous ceramic supports with improved filtration efficiency

Carbon nanotubes (CNTs) with high degrees of uniformity, orientation and controlled dimensions on porous supports are highly desirable for various applications such as separation of O/W emulsions and air purification. In this work, CNTs were fabricated on silicon carbide (SiC) porous supports with different porosities and pore sizes by chemical vapor deposition (CVD). The growth processes of CNTs on the surface and in the pore channels of the SiC support were studied in detail. Based on microstructural characterization by SEM, Raman spectroscopy and TEM, it was found that these CNTs grown in the pore channels of SiC supports had a higher degree of orientation and purity than those grown on the surface due to the spatially confined effect. The growth processes of various types of CNTs on the microporous supports were proposed, which were further verified by CNTs with different steric configurations (S-CNTs and VACNTs) and on Al₂O₃ porous supports. Moreover, the contribution of CNTs in the pore channels to the filtration efficiency was demonstrated in oil-water emulsion separation and particle removal in air. This work provides significant guidance for the preparation and filtration application of CNTs on porous materials.

The Effect of the Gaseous Environment on the Electrical Conductivity of Multi-Walled Carbon Nanotube Films over a Wide Temperature Range

The surrounding gas atmosphere can have a significant influence on the electrical properties of multi-walled carbon nanotube (CNT) ensembles. In this study, we subjected CNT films to various gaseous environments or vacuum to observe how such factors alter the electrical resistance of networks at high temperatures. We showed that the removal of adsorbed water and other contaminants from the surface under reduced pressure significantly affects the electrical conductivity of the material. We also demonstrated that exposing the CNT films to the hydrogen atmosphere (as compared to a selection of gases of inert and oxidizing character) at elevated temperatures results in a notable reduction of electrical resistance. We believe that the observed sensitivity of the electrical properties of the CNT films to hydrogen or vacuum at elevated temperatures could be of practical importance.

Carbon Nanotube Assembly and Integration for Applications

Carbon nanotubes (CNTs) have attracted significant interest due to their unique combination of properties including high mechanical strength, large aspect ratios, high surface area, distinct optical characteristics, high thermal and electrical conductivity, which make them suitable for a wide range of applications in areas from electronics (transistors, energy production and storage) to biotechnology (imaging, sensors, actuators and drug delivery) and other applications (displays, photonics, composites and multi-functional coatings/films). Controlled growth, assembly and integration of CNTs is essential for the practical realization of current and future nanotube applications. This review focuses on progress to date in the field of CNT assembly and integration for various applications. CNT synthesis based on arc-discharge, laser ablation and chemical vapor deposition (CVD) including details of tip-growth and base-growth models are first introduced. Advances in CNT structural control (chirality, diameter and junctions) using methods such as catalyst conditioning, cloning, seed-, and template-based growth are then explored in detail, followed by post-growth CNT purification techniques using selective surface chemistry, gel chromatography and density gradient centrifugation. Various assembly and integration techniques for multiple CNTs based on catalyst patterning, forest growth and composites are considered along with their alignment/placement onto different substrates using photolithography, transfer printing and different solution-based techniques such as inkjet printing, dielectrophoresis (DEP) and spin coating. Finally, some of the challenges in current and emerging applications of CNTs in fields such as energy storage, transistors, tissue engineering, drug delivery, electronic cryptographic keys and sensors are considered.

Modifying the morphology and properties of aligned CNT foams through secondary CNT growth

In this work, we report for the first time, growth of secondary carbon nanotubes (CNTs) throughout a three-dimensional assembly of CNTs. The assembly of nanotubes was in the form of aligned CNT/carbon (ACNT/C) foams. These low-density CNT foams were conformally coated with an alumina buffer layer using atomic layer deposition. Chemical vapor deposition was further used to grow new CNTs. The CNT foam's extremely high porosity allowed for growth of secondary CNTs inside the bulk of the foams. Due to the heavy growth of new nanotubes, density of the foams increased more than 2.5 times. Secondary nanotubes had the same graphitic quality as the primary CNTs. Microscopy and chemical analysis revealed that the thickness of the buffer layer affected the diameter, nucleation density as well as growth uniformity across the thickness of the foams. The effects of secondary nanotubes on the compressive mechanical properties of the foams was also investigated.

Carbon aerogels with improved flexibility by sphere templating

Using soft templating, mechanically reversible compressible resorcinol–formaldehyde aerogels can be converted into mechanically reversible compressible carbon aerogels with high surface area by carbonization in an inert atmosphere.

Natural extracted aerogels with inherent anisotropy and their 3D printing assisted biomedical applications

Exemplified with jackfruit and sugarcane, natural extracted aerogels with inherent structural anisotropy were investigated for the first time. With the help of nano-modification, the dual liquid/current directing capability of the Ag decorated jackfruit aerogel was discovered. This interesting material was then applied as the core component of a 3D printed wearable device for intelligent wound management. The as-prepared ultra-light (<10 g) wearable device could provide drainage diversion, wound warning and triple antibacterial treatment in a continuous and automatic manner.

A Pd/CNT-SiC monolith as a robust catalyst for Suzuki coupling reactions

A Pd/CNT-SiC monolith prepared by a simple two-step method exhibits robust catalytic activity and recycling ability in Suzuki coupling reactions.