Shaker Ebrahim

Dye-Sensitized Solar Cell Based on Polyaniline/Multiwalled Carbon Nanotubes Counter Electrode

This work presented the successful fabrication of dye-sensitized solar cell using polyaniline base (EB), multiwalled carbon nanotubes (MWCNTs), organic dye (rhodamine B or riboflavin), zinc oxide (ZnO), and indium tin oxide (ITO). The electrical properties of the resultant devices were investigated by measuring the current density voltage (-), capacitance voltage (-), and impedance measurements under both dark and illuminated conditions. The photovoltaic cell characteristics, that is, open circuit voltage (), short circuit current density (), and energy conversion efficiency (), were evaluated under illumination and were found to be 0.48 mA/cm2, 400 mV, and 0.224%, respectively, for ITO/EB-MWCNTs/ZnO-rhodamine B/ITO heterostructure. Using impedance spectra, it was found that the series resistances of this type of solar cell are 62 and 60 Ω under darkness and illumination, respectively.

Blend of Nylon 6 and Polyaniline Doped with Sulfanilic Acid and its Schottky Diode

Polyaniline/nylon 6 blends were prepared from formic acid as a single solvent with various weight ratios of polyaniline (PANI). The optical, structural, morphological, thermal, and electrical properties of these blends were investigated. Blend films with PANI protonated with sulfanilic acid (SA) as a new protonating agent showed higher conductivity and degree of protonation in comparison with unprotonated PANI. The PANI-SA/nylon 6 blend exhibited a percolation threshold at around 1.66 wt.% of PANI, whereas unprotonated PANI/nylon 6 blend appeared at round 10 wt.% of PANI. Schottky diodes based on PANI-SA and nylon 6 blend at different weight percentages of PANI were fabricated and characterized using Al as Schottky contact and Ag as an Ohmic contact.Polyaniline/nylon 6 blends were prepared from formic acid as a single solvent with various weight ratios of polyaniline (PANI). The optical, structural, morphological, thermal, and electrical properties of these blends were investigated. Blend films with PANI protonated with sulfanilic acid (SA) as a new protonating agent showed higher conductivity and degree of protonation in comparison with unprotonated PANI. The PANI-SA/nylon 6 blend exhibited a percolation threshold at around 1.66 wt.% of PANI, whereas unprotonated PANI/nylon 6 blend appeared at round 10 wt.% of PANI. Schottky diodes based on PANI-SA and nylon 6 blend at different weight percentages of PANI were fabricated and characterized using Al as Schottky contact and Ag as an Ohmic contact.

Impedance spectroscopy and equivalent circuits of heterojunction solar cell based on n-Si/polyaniline base

Different equivalent circuit models were used to fit the impedance spectra of a novel polyaniline base (EB)/n-type Si heterojunction solar cell at different bias voltages. The photovoltaic cell characteristics, i.e., open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF) and energy conversion efficiency (η) were evaluated under illumination (0.09 W/cm2) to be are 5.1 mA/cm2, 214 mV and 0.974%, respectively. Rollover and crossover phenomena in current density-voltage (J-V) curves under illumination were explained based on back contact barrier and the surface recombination of electrons at back contact. A phenomenological description of the capacitance behaviour was obtained by replacing the capacitor of the first model by a frequency-dependent non-ideal capacitor, a so-called constant phase element (CPE). The impedance spectra obtained at different applied voltages under illumination was not fitted with the same equivalent circuit as reported under darkness. The spectra displayed a phenomenon of negative imaginary impedance were related to the inductive effect in low frequencies in the heterojunction.

Electrical Transport Mechanism in Polyaniline/Formvar Blend Films:

Polyaniline (PANI) was synthesized chemically and doped with camphor sulfonic acid. New PANI/formvar blend films were prepared using solution blending. These blend films were characterized by UV-visible, Fourier transform infrared spectra and scanning electron microscopy to investigate their optical, structural and morphological properties. It was found that the percolation threshold of these blend films is 4.4 wt.% of PANI. The dc and ac conductivities of these blend films were measured at a temperature range from 70 to 300 K in the frequency range of 10 kHz—1 MHz. The temperature dependence of the dc conductivity of the PANI/formvar blend films followed the three-dimensional variable range hopping. Temperature variation of frequency exponents in this blend suggests that ac conduction is attributed to be correlated to barrier hopping.

Organic field effect transistor based on polyaniline - dodecylbenzene sulphonic acid for humidity sensor

Humidity sensor based on organic field-effect transistor (OFET) was created using P-channel organic semiconductor polyaniline doped with dodecylbenzene sulfonic acid (DBSA)(1∶2.5) as an active layer and gate insulator polymethyl methacrylate (PMMA) layer on n-type silicon gate. The performance of OFET was evaluated using current-voltage characteristics (I–V) under exposure to humidity. The p-type OFETs operating in an enhancement mode with the current saturation (ISat) was 2.6 µA and the threshold voltage VT was found to be 2.4V. The OFET sensors exhibited a change in the electric characteristic such as the threshold voltage, the saturation current, and the field-effect charge carrier mobility when the sensors were exposed to Relative humidity (RH). Meanwhile, the favourable and rapid change in humidity response characteristics of the OFET sensors was observed from the change in the drain-source current as a function of time. After exposed to relative humidity, the drain current of sensor was enhanced due to the decrease of the channel resistance. When the sensors were exposed to 93.4 % RH the drain current was saturated.

Effect of multi-walled carbon nanotubes on thermal properties of nitrate molten salts

Energy storage is a key element in energy conservation and efficiency of thermal energy utilization. Among different methods of storing thermal energy, latent heat thermal energy storage (LHTES) systems using phase change materials (PCMs) have been widely used. In this work, composites of multi-walled carbon nanotubes (MWCNTs) and NaNO3-KNO3 binary salt (60∶40 ratio) were mixed with four different weight fractions (0.1, 0.5, 1.0, and 1.5 wt. %) of MWCNTs using the direct synthesis method. The morphology, melting enthalpy, melting point, specific heat, and thermal conductivity were characterized using scanning electron microscope, differential scanning calorimetry, and hot disk analyzer. MWCNTs with concentrations of 0.1 wt. %, 0.5 wt. %, and 1.0 wt.% enhanced the heat of fusion of solar salt to 36.11%, 33.30%, and 10.11% respectively; And enhanced its thermal conductivity by 21.93%, 33.33%, 43.86% and 50.88% with concentration of 0.1 wt. %, 0.5 wt. %,1.0 wt.%, and 1.5 wt.%, respectively.

Quasi-solid-state Electrolyte for Dye Sensitized Solar Cells Based on Nanofiber PMA-PVDF and PMA-PVDF/PEG Membranes

Novel electrospun membranes quasi-solid electrolytes based on blends of polymethylacrylate (PMA) - polyvinylidene fluoride (PVDF), and PMA-PVDF/PEG (polyethylene glycol) are prepared by electrospin ...

Performance and stability of diaminotoulene-based polyamide composite reverse osmosis membranes incorporated with additives and cast on polyester fabric

aDepartment of Materials Science, Institute of Graduate Studies and Research, Alexandria University, 163 Horreya Avenue, El-Shatby, P.O. Box 832, Alexandria, Egypt, Tel. +201024604959; Fax: +2035603053; email: mohamedsaid@alexu.edu.eg (M. Said), Tel. +201021309751; Fax: +2034285792; email: shaker.ebrahim@alexu.edu.eg (S. Ebrahim), Tel. +201114454566; email: aligad2003@yahoo.com (A. Gad), Tel. +201003400746; email: s.kandil@usa.net (S. Kandil) bAbu Qir Fertilizers and Chemical Industries Co., Postal Code 21911, El-Tabia, Rashid Road, Alexandria, Egypt

High Stability Performance of Superhydrophobic Modified Fluorinated Graphene Films on Copper Alloy Substrates

A stable self-cleaning superhydrophobic modified fluorinated graphene surface with micro/nanostructure was successfully fabricated on copper substrates via drop coating process. Irregularly stacked island-like multilayered fluorinated graphene nanoflakes comprised the microstructure. The fabricated films exhibited outstanding superhydrophobic property with a water contact angle 167° and water sliding angle lower than 4°. The developed superhydrophobic surface showed excellent corrosion resistance with insignificant decrease of water contact angle 166° in 3.5 wt.% NaCl solution. This stable highly hydrophobic performance of the fluorinated graphene films could be useful in self-cleaning, antifogging, corrosion resistive coatings and microfluidic devices.

Thermal properties of composites of octadecane/carbon imbedded with graphite derivatives thermal energy storage

Thermal storage materials are essential components of concentrated solar power plants (CSP) as they improve systems availabilty and performance. Adding thermal energy storage to CSP power plant also increases it efficiency. The latent heat storage (LHS) as one type of storage using phase change materials (PCMs) has been used due to the large latent heat of fusion of most materials and also due to their ability to provide heat at a constant temperature. The aim of this work is to prepare composites of graphite derivatives imbedded in the matrix of octadecane to improve the thermal properties. The graphite derivatives used were graphene quantum dot (GQD) in addition to graphene prepared by staudenmier method. The thermal properties such as melting point, melting enthalpy were characterized using differential scanning calorimetry (DSC). It was found that the graphite derivatives have large effects on thermal energy storage capacity.