Gamal Nasr - Academia.edu (original) (raw)

Papers by Gamal Nasr

Effective enhancement of electric and magnetic properties of PMMA/LiFe5O8 nanocomposites via magnetic treatment

Journal of Materials Science: Materials in Electronics, 2021

The present study presents a facile effective method to enhance the electric as well as the magne... more The present study presents a facile effective method to enhance the electric as well as the magnetic properties of polymer/ferrite nanocomposites. Polymethyl methacrylate/lithium ferrite (75/25 wt%) nanocomposite is prepared by a modified casting technique. Samples were subjected to static magnetic field of 50 mT at room temperature for different time intervals (15 and 30 min.) during preparation. The measured DC and AC electrical properties as well as magnetic properties were compared to those of untreated sample, and the results were correlated to structural investigations. SEM and XRD studies revealed the formation of quasi-3– 1 nanocomposite after (30 min) pre-exposure to magnetic treatment. The DC conductivity at room temperature increased from 6.6 × 10−13 Ω−1 cm−1 for untreated sample to 3.14 × 10−10 Ω−1 cm−1 for (30 min.) pre-exposed sample. Besides, the dielectric constant at 1 kHz increased from 6.5 for untreated composite to 16 for the (30 min.) pre-exposed one. Finally, the saturation magnetization increased from 10.05 emu.g−1 for untreated sample to 19.09 emu.g−1 for (30 min.) treated sample.

Arab Journal of Nuclear Sciences and Applications, 2021

The effect of the surface treatment of clay nanoparticles on the Styrene -butadiene Rubber (SBR) ... more The effect of the surface treatment of clay nanoparticles on the Styrene -butadiene Rubber (SBR) /clay nanocomposite was studied. The treatment process was done by coating the clay surface with trimethylolpropane tiracrylate monomer (TMPTA) followed by polymerization with the assistance of 100KGy of electron beam irradiation. For comparison, two distinct groups of SBR/treated clay nanocomposites containing treated and untreated clay were prepared. The effect of clay nanoparticles loading and treatment process on rubber properties was investigated by various techniques such as dielectric spectroscopy, thermal gravimetric analysis (TGA), and thermomechanical analysis (TMA). It is found that by the addition of clay, there is a decrease in the amorphous contents of the samples owing to the detectable increase in the relaxation time. Furthermore, the increased dielectric constant (') of nanocomposite, with untreated clay content was observed which may result in more localization of charge carriers causing higher ionic conductivity. The thermal stability of nanocomposites increased with clay loading while it decreased with the treatment process. The converging values of the theoretical and experimental values of ', and dielectric loss ('') were also deduced. From TMA, it was found that the mean thermal expansion coefficient of nanocomposites decreased with increasing clay loading and treatment process.

Journal of Electronic Materials, 2021

Transparent films of polyvinyl alcohol/polyethylene glycol (PVA/PEG) blend loaded with different ... more Transparent films of polyvinyl alcohol/polyethylene glycol (PVA/PEG) blend loaded with different nano-silica (SiO 2) content were prepared by using solution casting. The effect of SiO 2 nanoparticle loading on the optical properties of selected PVA/PEG blend ratio is studied in the spectral region 200-700 nm. The present study monitors the changes in the optical dispersion parameters such as band tail width, extinction coefficient, refractive index, and optical dielectric constant calculated as a function of nano-silica content. The results revealed that the obtained optical parameters were strongly affected by the SiO 2 content in the blend films. Also, Cauchy model is used to fit the wavelength dependence of the refractive index of the composites. In addition, thermogravimetric analysis indicates the increase of thermal stability of the composites with respect to pure blend. The Coats and Redfern model is used to calculate activation energies for decomposition.

In this work, novel elastic rubber composites containing lithium ferrite (Li0.5Fe2.5O4) have been... more In this work, novel elastic rubber composites containing lithium ferrite (Li0.5Fe2.5O4) have been prepared to be applied as microwave elements and in microwave shielding applications. Nano scale lithium ferrite powder was synthesized via citrate gel autocombustion route. It has been incorporated in nitrile butadiene rubber (NBR) in a concentration levels 10-100 phr. X-ray diffraction analysis revealed that the addition of LF to NBR matrix greatly enhanced the crystallinity of NBR. The DC electric properties of these LF loaded NBR composites have been studied. The DC conductivity of LF loaded NBR composites showed marked dependence on LF concentration. The addition of LF initially increased the DC conductivity up to a concentration level of 20 phr, then the conductivity decreases upon further addition of LF. The dependence of current density on electric field intensity has been also studied. The behavior showed the non-Ohmic nature of the DC conduction process. Moreover, the possibil...

The use of polymer alloys blends and composites have grown constantly at 9% in the last 10 years ... more The use of polymer alloys blends and composites have grown constantly at 9% in the last 10 years and it is f our times the growth rate of total plastic industry . In this study, we report the polymerization process of undoped and doped Polymethyl methacrylate ( PMMA ) with different dye concentrations .The dielectric properties of PMMA (undoped and doped) polymerize d by laser beam irradiation have been compared with those polymerized with laser beam irradiation effects in order to establish the superiority of the laser beam irradiation process over the conventional polymerization. Compared to pure polymer, the dielec tric constant of the dye - polymer composites is greater for all fill concentrations because the system becomes more heterogeneous than the pure polymer as more dye is added to it. The increase in e΄ with increase in dye is attributed to the formation of cl usters, which lead to greater average polarization and thus a greater contribution to dielectric constant. In cas...

In this work, ten carbon black (CB) loaded elastic acrylonitrile butadiene rubber (NBR) nano-comp... more In this work, ten carbon black (CB) loaded elastic acrylonitrile butadiene rubber (NBR) nano-composites have been prepared to be used in microwave shielding applications. The DC electric properties of these CB loaded NBR composites have been studied. The evolution of DC conductivity of CB loaded NBR composites with loading level revealed S-shapes curve in accordance with the percolation theory. The current (I)-voltage (V) relations have been studied for these samples at room temperature. All CB loaded NBR composite samples showed Ohmic behavior with the exception of two samples namely CB30 and CB40 in which space charge limited conduction is obvious. Microwave shielding has been calculated from the transmittance data measured using terahertz time domain spectroscopy (THz-TDS) technique. The analysis of microwave shielding data revealed that the sample CB70 has the highest shielding effectiveness. The results of the microwave shielding effectiveness of CB loaded NBR composites were c...

Polymer composites are intensively studied for the new properties which are given by the combinat... more Polymer composites are intensively studied for the new properties which are given by the combination of the properties of the both polymer matrix and the filler respectively. When the concentration of the filler in the composite reaches the percolation value, the continuous bulk network structure is formed. If electrical conductive filler (Carbon black (CB)) is used, the composite properties can change from insulator to conductive ones. Electrical conductivity can change in the magnitude of several orders. The combination of polymers with carbon nanotubes allows linking the properties of both materials to form new functional materials. Samples were prepared in three steps. First, the solution samples were prepared by dissolving 1wt% sodium dodecyl sulfate (SDS) in distilled water using magnetic stirrer (corning hot plate stirrer PC-351) at 25 0 C for 1 hr. In the second step different weights of Multi-walled Carbon nanotube (CNT) in volume fraction (0.004, 0.009, 0.019, 0.029 and 0....

Egyptian Journal of Petroleum, 2019

Poly methyl methacrylate/ Lithium ferrite nano-composites have been prepared by solution mixing p... more Poly methyl methacrylate/ Lithium ferrite nano-composites have been prepared by solution mixing process. The electrical conductivity and dielectric properties of these prepared nano-composite have been investigated in the frequency range 10 2-10 6 Hz at different LiFe 5 O 8 concentrations from 0 vol% to 25 vol%. The prepared samples are studied by thermal gravimetric analysis (TGA) and X-ray diffraction (XRD). Moreover, the magnetic properties of these nano-composites are investigated through vibrating sample magnetometer studies. XRD spectral investigation revealed that the structural of PMMA and its chemical characterization are appreciably affected by mixed lithium ferrite filler. The thermal stability of the PMMA matrix was found to increase appreciably by LiFe 5 O 8 loading. The (I-V) characteristic of these nano-composites are in very good agreement with the non-linearity predicted by Kaiser et al. model. The effective dielectric constant is studied through different proposed models. Saturation magnetization of 10.05 emu/g is achieved for PMMA sample loaded with 25 vol% of LiFe 5 O 8 particles.

Polymers, 2017

Glass fiber reinforced polymer (GFRP) composites are widely used in infrastructure applications i... more Glass fiber reinforced polymer (GFRP) composites are widely used in infrastructure applications including water structures due to their relatively high durability, high strength to weight ratio, and non-corrosiveness. Here we demonstrate the potential use of carbon nanoparticles dispersed during GFRP composite fabrication to reduce water absorption of GFRP and to enable monitoring of moisture damage propagation in GFRP composites. GFRP coupons incorporating 2.0 wt % carbon nanofibers (CNFs) and 2.0 wt % multi-wall carbon nanotubes (MWCNTs) were fabricated in order to study the effect of moisture damage on mechanical properties of GFRP. Water absorption tests were carried out by immersing the GFRP coupons in a seawater bath at two temperatures for a time period of three months. Effects of water immersion on the mechanical properties and glass transition temperature of GFRP were investigated. Furthermore, moisture damage in GFRP was monitored by measuring the electrical conductivity of the GFRP coupons. It was shown that carbon nanoparticles can provide a means of self-sensing that enables the monitoring of moisture damage in GFRP. Despite the success of the proposed technique, it might not be able to efficiently describe moisture damage propagation in GFRP beyond a specific threshold because of the relatively high electrical conductivity of seawater. Microstructural investigations using Fourier Transform Infrared (FTIR) explained the significance of seawater immersion time and temperature on the different levels of moisture damage in GFRP.

Nanomaterials, 2016

In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fab... more In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fabrication of glass fiber composites to monitor damage propagation under static loading. The use of CNFs enables a transformation of the typically non-conductive glass fiber composites into new fiber composites with appreciable electrical conductivity. The percolation limit of CNFs/epoxy nanocomposites was first quantified. The electromechanical responses of glass fiber composites fabricated using CNFs/epoxy nanocomposite were examined under static tension loads. The experimental observations showed a nonlinear change of electrical conductivity of glass fiber composites incorporating CNFs versus the stress level under static load. Microstructural investigations proved the ability of CNFs to alter the polymer matrix and to produce a new polymer nanocomposite with a connected nanofiber network with improved electrical properties and different mechanical properties compared with the neat epoxy. It is concluded that incorporating CNFs during fabrication of glass fiber composites can provide an innovative means of self-sensing that will allow damage propagation to be monitored in glass fiber composites.

OPTICAL PROPERTIES of PMMA / DYE COMPOSITE IRRADIATED with LASER

Influence of Physical Aging on the Dielectric Relaxation of Ethylene-co-VinylAcetate (EVA)/PolyPyrrole (PP_y) Interpenetrating Polymer Network Composite Using TSDC Technique

Journal of the Korean Physical Society, 2011