Bahaa M. Abu-Zied

Direct Fabrication of Cobalt Oxide Nanoparticles Employing Sucrose as a Combustion Fuel

Combustion method has been used as a fast and facile method to prepare nanocrystalline Co3O4 spinel employing sucrose as a combustion fuel. The products were characterized by thermal analyses (TGA and DTA), X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Experimental results revealed that the molar ratio of fuel/oxidizer (F/O) plays an important role in controlling the crystallite size of Co3O4 nanoparticles. Transmission electron microscopy indicated that the crystallite size of Co3O4 nanocrystals was in the range of 13–32 nm. X-ray diffraction confirmed the formation of CoO phase with spinel Co3O4. The effect of calcination temperature on crystallite size and morphology has been, also, discussed.

Nitrous Oxide Decomposition over Alkali-Promoted Magnesium Cobaltite Catalysts

The direct decomposition of N2O was investigated over a series of magnesium cobaltite catalysts, MgxCo1-xCo2O4 (0.0 ≤ x ≤ 1.0), which were prepared by the thermal decomposition of stoichiometric amounts of magnesium hydroxide and cobalt acetate. The thermal genesis of the different catalysts from their precursors was explored using thermogravimetric analysis, differential thermal analysis, and X-ray diffraction. Texture analysis was carried out using N2 adsorption at −196 °C. We found that all the catalysts that were calcined at 500 °C have a spinel structure. N2O decomposition activity was found to increase with an increase in the spinel structures magnesium content. The influence of alkali cation promoters (Li, Na, K, and Cs) on the activity of the most active catalyst in the MgxCo1-xCo2O4 series, i.e. MgCo2O4, was also investigated. The sequence of the promotional effect was found to be: un-promoted 0.05, based on N2 adsorption and scanning electron microscopy results.

Pure and Ni-substituted Co3O4 spinel catalysts for direct N2O decomposition

Abstract A series of Ni x Co 1- x Co 2 O 4 (0 ≤ x ≤ 1) spinel catalysts were prepared by the co-precipitation method and used for direct N 2 O decomposition. The decomposition pathway of the parent precipitates was characterized by thermal analysis. The catalysts were calcined at 500 °C for 3 h and characterized by powder X-ray diffraction, Fourier transform infrared, and N 2 adsorption-desorption. Nickel cobaltite spinel was formed in the solid state reaction between NiO and Co 3 O 4 . The N 2 O decomposition measurement revealed significant increase in the activity of Co 3 O 4 spinel oxide catalyst with the partial replacement of Co 2+ by Ni 2+ . The activity of this series of catalysts was controlled by the degree of Co 2+ substitution by Ni 2+ , spinel crystallite size, catalyst surface area, presence of residual K + , and calcination temperature.

The synergism of cadmium on the catalytic activity of Cd–Cr–O system: II. Ethanol decomposition, catalysts reducibility, and in situ electrical conductivity measurements

Abstract In this paper, the conversion (dehydration/dehydrogenation) of ethanol over a series of chromia as well as cadmium/chromia catalysts calcined in the 400–1000°C temperature range has been studied. The reaction was performed in a fixed-bed reactor at atmospheric pressure and in the 150–400°C temperature range using nitrogen as a carrier gas. The reaction products were ethane, ethylene, and acetaldehyde together with trace amounts of ethyl acetate. The cadmium-containing catalysts, especially those calcined at 400 and 500°C, showed higher dehydrogenation activity. This trend was attributed to the catalyst reducibility, which was correlated with the presence of chromate ions. Such ions enhance the reduction of cadmium ions to zerovalent cadmium. Catalysts reducibility was checked by means of EtOH-temperature-programmed reduction (TPR), XRD, and FT-IR analyses. Moreover, in situ electrical conductivity measurements during alcohol admission were carried out. A good parallelism was found between the catalyst activity and its reducibility. In this way, the presence of Cd 0 –Cr 2 O 3 mixture, as a result of cadmium chromate reduction, showed a synergistic effect towards ethanol conversion as well as acetaldehyde selectivity. This effect was ascribed to the formation of donor–acceptor pairs as a consequence of Cd 0 –Cr 2 O 3 mixture formation.

Fabrication, characterization, and electrical conductivity properties of Pr6O11 nanoparticles

Abstract Pr 6 O 11 nanoparticles were obtained by subsequent thermal decomposition of the as-prepared precipitate formed under ambient temperature and pressure using NaOH as precipitant. The calcination process was affected, for 1 h in static air atmosphere, at 400–700 °C temperature range. The different samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), in situ electrical conductivity, and N 2 adsorption/desorption. The obtained results demonstrated that nano-crystalline Pr 6 O 11 , with crystallites size of 6–12 nm, started to form at 500 °C. Such value increased to 20–33 nm for the sample calcined at 700 °C. The as-synthesized Pr 6 O 11 nanoparticles presented high electrical conductivity due to electron hopping between Pr(III)-Pr(IV) pairs.

Nanocrystalline Co3O4 fabricated via the combustion method

A facile and rapid combustion method has been used to prepare nano-crystalline Co3O4 spinel employing urea as a combustion fuel. The fabrication was carried out by refluxing a mixture of cobalt nitrate and urea followed by calcination, for 3 h in static air atmosphere, at 400 °C. The thermal genesis of the Co3O4 was explored by means of thermogravimetric and differential thermal analyses in air atmosphere in the temperature range 25–1000 °C. X-ray diffraction, Fourier transform infrared spectra, and scanning electron microscopy were used to characterize the structure and morphology of the Co3O4. The obtained results conrmed that the resulting oxides were comprised of pure single-crystalline Co3O4 nanoparticles. Moreover, various comparison experiments showed that several experimental parameters, such as the reflux time and the urea/cobalt nitrate molar ratio, play important roles in the crystallite size as well as the morphological control of Co3O4 powders. Consequently, the minimum crystallite size can be obtained at 12 h reflux and a urea/cobalt nitrate molar ratio of 5.

The synergism of cadmium on the catalytic activity of Cd–Cr–O system: I. Preparation, characterization and electrical properties

Abstract Cadmium-containing catalysts were obtained by calcining a parent mixture of chromia and cadmium nitrate precursor materials in atomic ratio Cd/Cr=0.5. The thermal genesis of the catalysts was explored by means of thermogravimetric analysis (TGA) in different atmospheres (air, nitrogen, and hydrogen) and in the temperature range 25–1000°C. The calcination products were characterized by adopting many techniques such as differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), estimation of surface excess Cr 6+ concentration, surface area, and electrical conductivity measurements. It was demonstrated that raising the calcination temperature of Cd/Cr mixture results in many effects on the structural as well as the electrical properties of the calcination products. The role of Cd 2+ ions in improving the electrical behavior of such a mixture was discussed. The results of the present study offer the advantageously usage of Cd/Cr catalysts over the net chromia catalyst in the dehydration/dehydrogenation of alcohols as it will be discussed in the next paper.

Fabrication of a selective 4-amino phenol sensor based on H-ZSM-5 zeolites deposited silver electrodes

H-ZSM-5 zeolite is an inorganic material with large surface area and well-defined internal structure with porous uniform cages, cavities or channels. In this study, H-ZSM-5 was synthesised by calcination of the NH4-form at 500 °C for 3 h in air flow. This protonated H-ZSM-5 has been characterized in detail, which includes its optical, structural, morphological, and elemental properties by various conventional methods. For probable chemical sensor development, H-ZSM-5 was deposited on a silver electrode (AgE, surface area, 0.0216 cm2) to fabricate a sensor with a fast response towards selective 4-amino phenol (4-AMP) in the liquid phase. The sensor exhibited good sensitivity and long-term stability and enhanced electrochemical responses. The calibration plot was linear (r2 = 0.9979) over the 0.1 nM to 1.0 mM 4-AMP concentration ranges. The sensitivity was ∼2.085 μA cm−2 nM−1 and the detection limit was 0.02 nM (at a signal-to-noise ratio (SNR) of 3). By employing CV and EIS techniques, it was unveiled that the sensor is not well-operative in the absence of air. This shows a promising future for sensitive sensor development using mesoporous H-ZSM-5 by I–V methods for applications in the detection of hazardous and carcinogenic phenolic compounds in environmental and health care fields.

Thermal degradation studies of the reduced and oxidized poly(o-toluidine) matrix

Thermal degradation of poly(o-toluidine) (POT) reduced [base form (POT-EB)] and oxidized form [i.e. doped with salicylidine-aniline (SA) and/or salicylidine-o-aminophenol (SAP)] was investigated experimentally and computationally. The results of thermal (TGA) and differential thermal (DTG) gravimetric analysis suggest a higher thermal stability for the oxidized (SA or SAP-doped POT) than that for the respective reduced (POT-EB) chain. Non-isothermal degradation of the reduced POT matrix reveals hydrophilic nature about two times stronger than that for the oxidized form (SA and/or SAP-doped POT) under the same conditions. Molecular mechanics (MM+) calculations substantiate these observations. FTIR spectroscopic study of the calcined POT-EB showed that the quinoid (Q) ring (imino-structure) is thermally at least twice more stable than for that the benzenoid (B) rings (amino-structure) in the repeating unit of the polymer chain. Isothermal degradation curves [fraction decomposed (α) vs. degradation time (t in min)] of the polymers under investigation revealed that they are characteristically declaratory in shape.

The Role of Mixed Graphene/Carbon Nanotubes on the Coating Performance of G/CNTs/Epoxy Resin Nanocomposites

There is no doubt that, epoxy resin is one of the most important materials that has been widely used in coating technology. The present work is aimed to fabricate a new series of epoxy resin nanocomposites in the form of G/CNTs/EPY1-4 using simple dissolution method and ultrasonic assistance. The expected nanocomposites have been fabricated using 10% loading of different mixed ratios from G/CNTs. Four different G/CNTs mixed ratios were used 20/80%, 40/60%, 60/40%, and 80/20%. The structure of the G/CNT/EPY1-4 nanocomposites has been investigated and confirmed by normal characterization techniques including: X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Differential Thermal gravimetry (DTG) and field emission scanning electron microscopy (FE-SEM). T-25 and T-50 values for G/CNT/EPY1-4 nanocomposites were slightly higher than elegant epoxy. R-500 values for the fabricated materials were in the range of 8.98-10.04%. Furthermore, the role of mixed G/CNTs on the coating properties of epoxy resin was determined using electrochemical impedance and technique. The coating resistance of epoxy composites in the form of G/CNT/EPY1-4 was larger than that observed for elegant epoxy coating. G/CNT/EPY3 and G/CNT/EPY1 showed highest and the lowest coating impedance values respectively. In addition to that, the water sorption technique has been used as a complementary method for such coating behaviour. The water uptake was efficiently decreased in all the formulations compared to the epoxy due to the presence of G/CNTs reinforcing agents.