Engineering of oriented carbon nanotubes in composite materials

Abstract

The orientation and arrangement engineering of carbon nanotubes (CNTs) in composite structures is considered a challenging issue. In this regard, two groups of in situ and ex situ techniques have been developed. In the first, the arrangement is achieved during CNT growth, while in the latter, the CNTs are initially grown in random orientation and the arrangement is then achieved during the device integration process. As the ex situ techniques are free from growth restrictions and more flexible in terms of controlling the alignment and sorting of the CNTs, they are considered by some as the preferred technique for engineering of oriented CNTs. This review focuses on recent progress in the improvement of the orientation and alignment of CNTs in composite materials. Moreover, the advantages and disadvantages of the processes are discussed as well as their future outlook.

Hydrolytic degradation and cytotoxicity of poly(lactic‐co‐glycolic acid)/multiwalled carbon nanotubes for bone regeneration

“…Magnetization decreased, with the content of MWCNTs, due to the diamagnetic behavior of PLGA. The MWCNTs could be aligned in the PLLA scaffolds under a magnetic field and the magnetization and various thermal, electrical, and optical properties will depend on the orientation of the MWCNTs in the polymer . Some authors have found a superparamagnetic behavior with no coercivity and remanence to PLLA/m‐MWCNTs composites, but with a much higher content of MWCNTs, at around 3 wt %, than the one used in this study to produce our samples.…”

Purification of Single‐Walled Carbon Nanotubes Using Acid Treatment and Magnetic Separation

“…[29,30] This peak could be attributed to catalyst located on the surface of the CNTs. After acid processing, the intensity of this line decreases and the line completely disappeared for SW_HNO 3 :…”

“…Single‐walled carbon nanotubes (SWCNTs) attract great attention due to their remarkable properties . Since their discovery, SWCNTs have occupied key positions in many areas, including composite materials, conductive and cable fibers, electrochemistry, and other applications. The as‐grown CNTs contain carbonaceous impurities, such as amorphous carbon and carbon nanoparticles, and metal impurities used as catalyst for nanotubes growth.…”

“…15.0 wt.% of iron in their composition were purified with concentrated HCl and 5 M HCl at a purity degree about 93 and 98%. [9] The treatment with concentrated HNO 3 was not efficient for MWNCT purification, [9] while SWCNT purity degree could reach ca. 98-99% with their sonication in concentration HNO 3 .…”

“…[10,11] Mixed acid treatment usually demonstrates better efficiency for iron removal. [9,12,13] In particular, processing of SWCNTs and MWCNTs in acid solution H 2 SO 4 :HNO 3 promotes iron elimination to ca. 2 and 5 wt.%, respectively.…”