Usama Khaled

Effects of pH on water-solubilization of carbon nanotube using microplasma in aqueous solution

The authors have previously proposed a novel technique for the preparation of water-soluble carbon nanotubes (CNTs) using microplasma generated by a pulsed streamer discharge in water. This paper describes effects of pH values on water-solubility of single-walled CNT (SWCNT) treated by the microplasma. The SWCNT treated under basic conditions showed two times higher solubility compared to that treated under neutral condition, whereas the SWCNT solubility considerably decreased under acidic conditions. Based on optical emission measurements of microplasma showed that radical formation was not pH sensitive. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis showed that the microplasma treated SWCNT was functionalized with –COO- groups with little pH dependence. In contrary, clear pH dependence was observed for zeta potential of the microplasma-treated SWCNT. The lowest zeta potential was -46 mV, which was obtained with basic solution adjusted by NH3 (pH ≈9). The SWCNT treated under basic conditions was more negatively charged due to suppressed protonation of –COO- groups. As a result, the electrostatic repulsion force between SWCNTs could overcome van der Waals force improving their solubility and dispersibility in water.

Solubilization of single-walled carbon nanotubes using Ozone generated by dielectric barrier discharge

This paper describes effects of ozone (O3) concentration on water-solubility of single-walled carbon nanotubes (SWCNTs). Ozone was generated by dielectric barrier discharge (DBD) in atmospheric air with the maximum concentration of 220 ppm. Water solubility of ozone-treated SWCNTs, which was evaluated by optical absorbance of the SWCNT suspension, increased with ozone treatment time and reached the maximum in 60 min. The dispersed SWCNTs suspension was stable even after two months of the ozone treatment. Fourier transform infrared (FTIR) spectroscopy and Raman spectra analysis revealed that SWCNTs surface was functionalized with chemical group such as –COO- after the ozone treatment. The longer ozone treatment introduced more functional groups and decreased zeta potential of the SWCNT surface, which improved water-solubility of the SWCNTs due to electrostatic repulsion force between them. It was also found that the ozone treatment induced morphological changes of SWCNTs.

Performance evaluation of two stages electrostatic precipitator novel design under loading conditions

This paper evaluates experimentally the influence of different parameters which controls the performance of two stages electrostatic precipitator (ESP) on its collection efficiency. A novel proto-type design that represents a two stages ESP was implemented at the high voltage laboratory. The experiments investigate the effect of gas flow velocity and injected gas temperature on ESP performance under different loading conditions. Maximum collection efficiency of ESP design will be optimized according to obtained measurements. The experimental results are validated by comparing it with simulation results.

Dielectric properties improvement of LDPE based on nano fillers

Presently along with traditional insulators such as glass and porcelain, etc., the polymeric insulators are also used world widely. The electrical properties of these composite insulations can be improved by adding of nano-sized inorganic filler. Therefore, composite insulators with nano-fillers have attracted a lot of attention. These polymeric insulators are very sensitive to various environmental parameters such as UV radiations, heat, etc. This work describes analytical study of some factors such as corona discharge, temperature, and ultraviolet (UV) radiations that affect the composite insulator performance. The nano materials such as Alumina (AhO3), Silica (SiO2), Fumed Silica, and Clay having different concentrations are added into low density polyethylene (LDPE) polymeric insulators. The samples were aged in the laboratory as per IEC std. 61109 and then the electrical/non-electrical characteristics were studied before and after the accelerated aging of the samples.

Evaluation of lightning performance on transmission system sag

A lightning stroke causes current injection into transmission lines at the point of contact. The lightning performance can be difficult to understand without using simulation programs. PSCAD is powerful software was selected to develop the appropriate data required to investigate this phenomena. In this paper, a model of 500 kV transmission line is developed when lightning stroke hits the shield wire directly at the mid-span sag location of transmission line. This study emphasizes on lightning performance when stroke hits either top of transmission tower or position of maximum sag locations between towers. In addition, the effects of lightning strokes on overvoltage along transmission system are studied. The results revealed that the sag of transmission line has a considerable influence on fast transient flashover and induced voltages occurrences across line insulators as well as phase lines.