Somia Awad

The electrospinning method has been successfully employed to prepare various percentages of less expensive nickel/palladium (NP) nanofiber catalysts as an alternative to platinum in direct methanol fuel cells (DMFC). The chemical structure, morphological characteristics, and electrochemical (EC) properties have been investigated using a variety of analysis techniques. According to the scanning electron microscope (SEM), all prepared samples with different Pd concentrations exhibit good nanofiber form and a distinct nanoparticle look. Transmission electron microscopy (TEM) reveals an amorphous carbon nanofiber structure with imbedded crystalline spheres of nickel and palladium. The carbonized polyvinyl alcohol nanofibers (PVANFs) have a steady and even distribution of nickel and palladium with an accurate nickel and palladium content, according to the energy dispersive X‐ray mapping results. The lack of hydroxide or oxide phases in the X‐ray diffraction (XRD) pattern proves that Ni–Pd nanoparticles are present in the metallic phase. For the electrooxidation of methanol, urea, and an isopropanol‐methanol mixture, the electrocatalytic features of the fabricated samples have been examined. EC results show that methanol has the best electrocatalytic properties. Hence, NP nanofiber catalysts could be a promising candidate to replace platinum in DMFC.

The electrospinning method has been successfully employed to prepare various percentages of less expensive nickel/palladium (NP) nanofiber catalysts as an alternative to platinum in direct methanol fuel cells (DMFC). The chemical structure, morphological characteristics, and electrochemical (EC) properties have been investigated using a variety of analysis techniques. According to the scanning electron microscope (SEM), all prepared samples with different Pd concentrations exhibit good nanofiber form and a distinct nanoparticle look. Transmission electron microscopy (TEM) reveals an amorphous carbon nanofiber structure with imbedded crystalline spheres of nickel and palladium. The carbonized polyvinyl alcohol nanofibers (PVANFs) have a steady and even distribution of nickel and palladium with an accurate nickel and palladium content, according to the energy dispersive X‐ray mapping results. The lack of hydroxide or oxide phases in the X‐ray diffraction (XRD) pattern proves that Ni–P...

The role of nanofluids in the development of many electronic devices at the industrial level is very significant. This investigation describes the thermal exploration for a bioconvective flow of Maxwell nanoparticles over stretching and revolving the cylinder placed in a porous medium. The fluid flow is in contact with chemically reactive activation energy. The swirling flow is induced by the stretching rotary cylinder. The magnetic effect of constant strength B0 is practiced to the flow system in combination with thermally radiative effects and a heat source/sink for controlling the thermal effects upon the flow system. The thermophoretic and Brownian motion characteristics, due to the nanofluid flow, are captured by implementing the Buongiorno model. The central focus of this study is to explore the thermal and mass transfer for the flow problem accompanied by motile microorganisms. The governing equations have been converted to the dimensionless form with similar variables, and t...

A variable, mono-energetic positron beam was employed to study the free volume characteristics of coating system composed of zinc oxide nanoparticles dispersed in waterborne polyurethane. Positron annihilation lifetime spectroscopy, in tandem with Doppler-broadening energy spectra and derived S parameter is used to quantitatively assess the free volume and interfacial interactions between zinc oxide nanoparticle surface and waterborne polyurethane. It was found that S parameter decreases with increasing ZnO load from 0 to 5%. The decrease of S parameter is explained as a result of strong interfacial interactions between the surface of the ZnO nanoparticles and WBPU chains. Furthermore, the half depth where the change in S parameter is reduced by half from the surface to bulk was found to increase with increasing ZnO concentration. These results are presented in the framework of free volume interactions in which the S parameter is quantitatively used to characterize the free volume i...

Positron annihilation spectroscopy (PAS) has been developed as a novel probe to characterize the sub-nanometer defect, free volume, profile from the surface, interfaces, and to the bulk in polymeric materials when a variable mono-energy slow positron beam is used. Free-volume hole sizes, fractions, and distributions are measurable as a function of depth at the high precision. PAS has been successfully

ABSTRACT Positron annihilation spectroscopy coupled with a variable mono-energy positron beam has been applied to study nanoscale polymeric nanocomposites. New information about multilayer depth profiles and structures, interfacial free-volume and open space properties have been obtained in polystyrene/carbon nano fiber composites. The S parameter in Doppler Broadening Energy Spectra combined slow positron beam is used to quantitatively represent the free volume, open spaces, and interactions in the interface between polystyrene matrix and carbon nanofibers.

... Positron annihilation lifetime spectroscopy (PALS) has recently emerged as a unique nano-probe capable of measuring the free volume hole sizes in polymers (Mallon, 2003; Abdel-Hady, 2003;Abdel-Hady and Mohamed, 2002; He et al., 2002; Bamford et al., 2001). ...

... EE Abdel-Hady * , Hamdy FM Mohamed, and Somia S. Fareed Physics Department, Faculty of Science, El-Minia University, El-Minia 61519, Egypt ... Sci. B, Polym. Phys. 41, 3089 (2003). [2] EEAbdel-Hady and Hamdy FM Mohamed, Mater. Sci. Forum 363–365, 284 (2001). ...

The free-volume properties in a system of zinc oxide (ZnO) nanoparticles (20 nm) dispersed in waterborne polyurethane (WBPU) were measured using positron annihilation lifetime spectroscopy. Two glass-transition temperatures (T g), lower T g∼ 220 K and higher T g∼ ...

Positron annihilation spectroscopy coupled with a newly built slow positron beam at National University of Singapore has been used to study the free volume, pore, and depth profile (0 – 10 μm) in cellulose acetate polymeric membrane at the bottom and top sides of membranes for ionic separation in water purification applications. The S and R parameters from Doppler broadening energy of annihilation radiation representing free volumes (0.1–1 nm size) and pores (>1 nm–μm) as a function of depth have been analyzed into multilayers, i.e. skin dense, transition, and porous layers, respectively. The top side of membrane has large free volumes and pores and the bottom side has a skin dense layer, which plays a key role in membrane performance. Positron annihilation lifetime results provide additional information about free-volume size and distribution at the atomic and molecular scale in polymeric membrane systems. Doppler broadening energy and lifetime spectroscopies coupled with a vari...

• GO nanosheets were successfully embedded in PA layer via filtration IP technique. • GO nanosheets increased membrane surface hydrophilicity and provided nanochannels for higher permeability. • TFN-f 0.02 showed optimum PWP which was 31.4% higher than the control membrane. • TFN-f 0.02 showed 95.8% and 97.7% rejection against Na 2 SO 4 and MgSO 4 , respectively. A B S T R A C T In this work, tailor-made graphene oxide (GO) incorporated thin film nanocomposite (TFN) membranes based on novel interfacial polymerization (IP) technique were presented. The embedment of GO nanosheets within ul-trathin cross-linked polyamide (PA) layer was successfully achieved without forming particle agglomeration that could affect structural integrity. A total of five composite membranes with different GO loadings (0, 0.01, 0.02, 0.03 and 0.04 g/m 2) were fabricated and these membranes were characterized using TEM, FESEM, XPS, ATR-FTIR and contact angle goniometer to evaluate the impact of GO loading on the physicochemical properties of PA selective layer. It is found that with the presence of GO, the TFN membranes exhibited higher surface hy-drophilicity due to increment in hydroxyl and carboxyl groups in PA layer, hence, improved the attraction between water molecules and membrane surface. Upon incorporation of 0.02 g/m 2 of GO, the resultant TFN membrane achieved 95.8% and 97.7% removal rate for Na 2 SO 4 and MgSO 4 , respectively along with 31.4% higher water flux than the membrane contained no GO. More importantly, this work demonstrated the broad

The possibility of developing low-cost commercial grafted and sulfonated Poly(vinylidene fluoride) (PVDF-g-PSSA) membranes as proton exchange membranes for fuel cell applications have been investigated. PVDF-g-PSSA membranes were systematically prepared and examined with the focus of understanding how the polymer microstructure (degree of grafting and sulfona-tion, ion-exchange capacity, etc) affects their methanol permeability, water uptake, and proton conductivity. Fourier transform infrared spectroscopy was used to characterize the changes of the membrane's microstructure after grafting and sulfonation. The results showed that the PVDF-g-PSSA membranes exhibited good thermal stability and lower methanol permeability. The proton conductivity of PVDF-g-PSSA membranes was also measured by the electrochemical impedance spectroscopy method. It was found that the proton conductivity of PVDF-g-PSSA membranes depends on the degree of sulfonation. All the sulfonated membranes show high proton conductivity at 92°C, in the range of 27 to 235 mScm −1 , which is much higher than that of Nafion212 (102 mScm −1 at 80°C). The results indicated that the PVDF-g-PSSA membranes are particularly promising membranes to be used as polymer electrolyte membranes due to their excellent stability, low methanol permeability, and high proton conductivity. KEYWORDS Poly(vinylidene flouride), degree of sulfonation, water uptake, Ion exchange capacity, proton conductivity, methanol Permeability 1 | INTRODUCTION Recently, ion-conducting membranes are regarded as important materials because of the various fields in which they can be applied: ion exchangers, in water treatment, rechargeable batteries, electrochromic devices, and in electrolysis. 1,2 One important application for this kind of membranes is the proton-exchange membrane fuel cell (PEMFC) that is a promising power source for low-emission vehicles. The PEMFC is the most suitable type of fuel cells for terrestrial vehicles owing to its low operation temperature, high energy efficiencies and high power densities. The PEMFC has interested considerable research in chemistry, physics, and theory. 3-7 The proton-exchange membrane (PEM) is a key component in PEMFC, which serves as both an electrolyte and separa-tor. Because of the requirements of the environment, an ideal PEM material requires a combination of chemical and physical properties: long-term chemical and electrochemical stability in the reducing environment at the cathode and the harsh oxidative environment at the anode, good mechanical strength, and dimensional stability in tight PEM stacks, and high proton conductivity under various operational conditions (ie, temperatures and relative humidity). A lot of polymers have been prepared and studied in the past decades with some successes and limitations. These polymers are mainly known as fluoropolymers 8-10 and aromatic hydrocarbon polymers. 11-13 The most commonly known polymer is Nafion (sulfonated fluoropolymer), which has high stability and good proton conductivity in low temperatures and high relative-humidity conditions. However, the Nafion-based PEM is expensive, and its conductivity showed reduction at higher temperatures (>80°C) and low humidity (<40%) conditions. A lot of studies have been performed with the goal of developing alternative membranes , focusing on the reduction of the methanol permeability. Some of them have worked on developing new synthetic polymeric membranes that have ionic clusters, 14-17 or the modification of the Nafion membranes by surface treatment or by blending them with other