Multi-walled Carbon Nanotubes Powder Research Articles

Gas-phase surface functionalization of multi-walled carbon nanotubes with vacuum UV photo-oxidation

For bulk processing of carbon nanotubes, an important first step in adhesion to the nanotubes is often liquid-phase functionalization through chemical oxidation with acids (e.g., nitric and sulfuric), peroxides and/or potassium permanganate. In comparison, gas-phase photo-oxidation can be an alternative to introduce oxygenated functional groups on the surfaces of carbon nanotubes without the generation of liquid waste. In the present study, vacuum UV photo-oxidation of multi-walled carbon nanotube (MWNT) paper was investigated downstream from an Ar microwave plasma. X-ray Photoelectron Spectroscopy (XPS) was used to detect the carbon- and oxygen-containing functional groups in the top 2–5 nm of the sample's surface. The current results are compared to previous investigations using MWNT powder and single-walled carbon nanotube (SWNT) paper showing decreased levels of oxidation in MWNT samples.

Near‐Edge X‐ray Absorption Fine Structure Spectroscopy as a Tool for Investigating Nanomaterials

We have demonstrated near-edge X-ray absorption fine structure (NEXAFS) spectroscopy as a particularly useful and effective technique for simultaneously probing the surface chemistry, surface molecular orientation, degree of order, and electronic structure of carbon nanotubes and related nanomaterials. Specifically, we employ NEXAFS in the study of single-walled carbon nanotube and multi-walled carbon nanotube powders, films, and arrays, as well as of boron nitride nanotubes. We have focused on the advantages of NEXAFS as an exciting, complementary tool to conventional microscopy and spectroscopy for providing chemical and structural information about nanoscale samples.

Light-scattering and dispersion behavior of multiwalled carbon nanotubes

Elliptically polarized light-scattering measurements were performed to investigate the dispersion behavior of multiwalled carbon nanotubes (MWNT). Xylene- and pyridine-derived MWNT powders were dispersed in water and ethanol in separate optic cells and allowed to sit undisturbed over a two-week time period after probe sonication. Continuous light-scattering measurements taken between scattering angles of 10-170 deg and repeated over several days showed that the nanotubes formed fractal-like networks. The pyridine-derived MWNTs showed greater dispersion variation over time, tending to aggregate and clump much faster than the xylene-derived tubes. The water suspensions appeared much more stable than the ethanol suspensions, which transformed into nonfractal morphology after a few hours. We relate the dispersion stability to size and fringe patterns on the outer surface of the nanotubes. Measured values of fractal dimension were distinctly lower than those in previous studies of single-walled carbon nanotubes. Profiles of both diagonal and off-diagonal scattering matrix elements are presented.

Relationship between field emission property and composition of carbon nanotube paste for large area cold cathode

Carbon nanotube (CNT) paste was prepared by a mixture of multi-walled carbon nanotubes powders synthesized by arc discharge, organic vehicles and inorganic binders. We investigated rheological properties of CNT paste using a rheometer. In order to obtain the fine dispersion of CNTs in paste, pass time of 3-roll mill was increased from 3–15. However, emission current density was decreased with an increase in pass time of 3-roll mill because of an increase in the interaction among CNT powders, organic vehicles and inorganic binder. It was found that emission property of a CNT paste depends mainly on the concentration of inorganic binder and firing time. We obtained good emission property by using a CNT paste with 30 wt% inorganic binders after treatment at 350 °C for 30 min.

Ni-deposited multi-walled carbon nanotubes by electrodeposition

Multi-walled carbon nanotubes (MWNTs), having a diameter around 100–200 nm, were used as host material for electrodeposition of Ni using a Ni plating bath containing homogeneously dispersed MWNTs. Ni-deposited or coated MWNTs with a skewered dumpling shape accumulated on the Cu cathode electrode. A model representing the growth process of these electrodeposits, which possess such a skewered dumpling shape, is presented. These electrodeposits were separated easily from the cathode electrode by ultrasonic irradiation in an acetone bath to yield a Ni-deposited or coated MWNTs powder. The amount of Ni deposited on the MWNTs can be controlled by selecting the appropriate electroplating conditions.