Suhaila M. Sanip

A review of purification techniques for carbon nanotubes

Purification of carbon nanotubes (CNTs) is a very actively discussed topic in contemporary CNT literature. To a large extent, impurities embedded in CNTs influence the physical and chemical characteristics of the CNTs. Different purification methods yield different CNT characteristics and may be suitable for the production of different types of CNTs. Developments in the purification methods of CNTs are reviewed, and the production methods are briefly discussed and summarized. This is followed by a detailed description of the three major purification methods, viz. chemical, physical, and multi-step purification.

Effect of Dispersed Multi-Walled Carbon Nanotubes on Mixed Matrix Membrane for O2/N2 Separation

Mixed matrix membranes (MMMs) consisting of multiwalled carbon nanotubes (MWCNTs) embedded within polyetherimide were prepared. Surfactants of different charges were utilized to disperse the nanotubes through a simple non-covalent approach. The characterization results suggest that proper selection of the dispersing agent contributed to better dispersion of nanotubes. The MMMs exhibited improved thermal stability and mechanical strength, which indicate the improvement of dispersion and compatibility within the polymer matrix. The resulting membrane exhibited permeance improvement of O2 and N2 as much as 87.7% and 120% respectively compared to that of neat polyetherimide. The results implied that Triton-X100 treated MWCNTs is a promising filler to enhance gas permeability.

Preparation and characteristics of functionalized multiwalled carbon nanotubes in polyimide mixed matrix membrane

The functionalization of multiwalled carbon nanotubes (MWNTs) with β cyclodextrin (β-CD) is described. The functionalization using β-CD treatment is an environmentally friendly and nondestructive method to modify carbon nanotubes. It was observed that the degree of functionalization increases with increasing ratios of β-CD as seen from the Raman analysis. The Raman spectra also indicated that the nanotubes walls were not damaged. The presence of functional groups associated with β-CD on the functionalized MWNTs indicated that the cyclodextrin groups were found to be adsorbed at the surface of the nanotubes walls. Mixed matrix membrane (MMM) was prepared by a phase inversion process. Enhanced selectivity and permeability for CO2 over CH4 was observed for MMM prepared using functionalized MWNTs.

Template Synthesis of Carbon Nanotubules

The template synthesis of carbon nanostructures formed in porous anodic aluminium oxide (AAO) template with a pore size of 200 nm by a liquid phase impregnation of the template with a polymer, polyfurfuryl alcohol, followed by carbonization is studied. The temperatures of exposure to furfuryl alcohol vapour were varied between 50 and 70° C. The resultant carbon nanotubules formed were hollow with open ends having diameter ranging from 220–300 nm which is in agreement with the pore size of the template used. The BET surface area was found to increase from 11.64 m2/g before pyrolysis to 90.19 m2/g after pyrolysis as a result of the formation of carbon nanotubules.

Cyclodextrin‐Functionalized Carbon Nanotubes For Mixed Matrix Membrane

Carbon nanotubes (CNTs) have generated great interest within the many areas of nanotechnology due to their superior and outstanding physical properties. However effective dispersion in many solvents has imposed limitations upon the use of CNTs in a number of novel applications. Functionalization presents a solution for CNTs to be more soluble which make them integrate well into any organic, inorganic or biological systems. CNTs can be easily functionalized using cyclodextrin (CD) treatment. The CD modification of carbon nanotubes is both simple and effective. It requires no prolonged heating, filtration and washing which can severely damage the small diameter nanotubes. The formation of surface functional groups and changes of nanotubes structures of functionalized carbon nanotubes (f‐CNTs) were monitored by Fourier transform infrared spectroscopy (FTIR), Thermo gravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM), respectively. From the TGA results, the amount of weight loss...

Hydrogen Adsorption on Activated Carbon an Carbon Nanotubes Using Volumetric Differential Pressure Technique

A simple hydrogen adsorption measurement system utilizing the volumetri differential pressure technique has been designed, fabricated and calibrated. Hydroge adsorption measurements have been carried out at temperatures 298 K and 77 K on activate carbon and carbon nanotubes with different surface areas. The adsorption data obtained will b helpful in understanding the adsorption property of the studied carbon materials using th fundamentals of adsorption theory. The principle of the system follows the Sievert‐type metho The system measures a change in pressure between the reference cell, R1 and the sample cell S1, S2, S3 over a certain temperature range. R1, S1, S2, and S3 having known fixed volume The sample temperatures will be monitored by thermocouple TC while the pressures in R1 an S1, S2, S3 will be measured using a digital pressure transducer. The maximum operatin pressure of the pressure transducer is 20 bar and calibrated with an accuracy of ±0.01 bar. Hig purity hydrogen is being used in the syst...

Effects of heat treatment on synthetic graphites for carbon nanotubes synthesis

Carbon materials are well known for their excellent adsorbent property towards gases. Much work has been done to improve the properties of carbon materials as to enhance their absorption capacity towards gases. Recent developments have resulted in the discovery of novel carbon materials such as carbon nanotubes. Numerous researches have shown that carbon nanotubes have excellent capacity for hydrogen storage. However, significant research has been undertaken to further improve the adsorption capacity through the advancement in synthesis methods for the fabrication of carbon nanotubes. Among the starting material widely employed for synthesis of carbon nanotubes is high purity graphite. Therefore, purpose of this work is to investigate the effect of thermal treatment on several synthetic graphites. Thermal treatment was conducted at temperatures ranging from 400–800°C at different dwelling times. The morphology and surface analysis of the graphites were examined using Scanning Electron Microscope and nitrogen gas adsorption techniques, respectively. It was found that temperature, time and conditions of treatment significantly change the surface structure of the graphites. A decrease in particle size was observed due to the release of internal surface area.