Autocatalytic dissolution of Pb in HNO3

The reaction between Pb and HNO₃ has been investigated using the thermometric technique. Weight-loss measurements on the reaction were also obtained. As the HNO₃ concentration is increased from 5×10^–2 to 4mol l^–1, the corrosion rate increases. This is shown thermometrically by a substantial increase in the maximum temperature attained, T _m, as well as a decrease in the time, t, required for reaching T _m. Dissolution of Pb in HNO₃ is proposed to take place according to an autocatalytic mechanism. Passivation sets were detected in solutions 11 mol l^–1 HNO₃. A parallel indication between the thermometric technique and weight-loss measurements was obtained. The rate-determining step of the autocatalytic process involves HNO₂ in dissolution of Pb in HNO₃. This is supported by the results of addition of hydrazine to the solution. This additive raises the maximum measured temperature, without affecting the corresponding time necessary to reach it. The effect of addition of NaNO₂, NaNO₃, NaCl, Na₂SO₄, NaH₂PO₄ and NaClO₄ on the reaction number, RN, of Pb in 4 mol l^–1 HNO₃ was examined. Only NaNO₂ accelerates the dissolution reaction while the other salts show as inhibition effect. It was found that these additives inhibit dissolution due to the displacement of some cathodic depolarizing components, as NO₂, from the active sites on the metal surface. The effect of addition of HCl, H₂SO₄, HClO₄ and H₃PO₄ on the reaction number, RN, of Pb in 4 mol l^–1 HNO₃ was also investigated. The observed acceleration and retardation of the dissolution of Pb was found to be dependent on both the concentration and nature of anions of the extra acids added.     

The use of wood pulp and radiation‐modified starch in wastewater treatment

Radiation‐induced graft copolymerization of maize starch/acrylic acid has been performed. Also, natural byproduct wood pulp was used after chemical treatment for the removal of metal ions from the investigated wastewater. The surface and structure morphology of the wood pulp and starch/acrylic acid were investigated by scanning electron microscopy and infrared spectroscopy. The physical parameters, such as swelling, gel percentage, and grafting efficiency (%) of starch/acrylic acid copolymer, were studied. The factors affecting the abilities of the prepared materials for removing heavy metal ions and dyes from aqueous solutions were studied. It was found that the maximum metal uptake is in the following sequence: Fe³⁺ > Cr³⁺ > Pb²⁺ > Cd²⁺. The adsorption capacity of such investigated metal ions increases with the increase of pH values. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Media,Technologies, Cooperation – Rethinking Publics and Publicness in the MENA Region

Computer Supported Cooperative Work (CSCW) -     

Effects of diagenesis on the geomechanical and petrophysical aspects of the Jurassic Bir El-Maghara and Masajid carbonates in Gebel El-Maghara,North Sinai,Egypt

Bulletin of Engineering Geology and the Environment - In the present study, the Jurassic Bir El-Maghara and Masajid Formations in North Sinai are subjected to a detailed microfacies analysis to...     

Anodic dissolution of nickel in acidic chloride solutions

The anodic dissolution of nickel was studied galvanostatically in hydrochloric acid solutions of various concentrations. The reaction orders of chloride ion and hydrogen ion concentrations were found to be 0.5 and 1.0, respectively. An anodic Tafel slope equal to 120 ± 10 mV · decade⁻¹ was obtained. The dissolution rate of nickel at constant acid concentration was increased with stirring of the solution and increasing temperature. The activation energy, ΔH, for the anodic dissolution process was found to be 12 kcal · mol⁻¹. The presence of oxygen in solutions assisted the passivation process. The effect of addition of aniline and some of its derivatives (o-, m-, and p-anisidine) as inhibitors on the dissolution kinetics of Ni in 1 M HCl was also investigated. These compounds inhibited the anodic dissolution of nickel without affecting the Tafel slope, indicating that the adsorption of such inhibitors could not interfere with the mechanism of metal dissolution.     

Ion beam analysis of ancient Egyptian wall paintings

Polychromatic decorations of ancient Egyptians tombs and temples have a long tradition over three millennia but are hard to identify because many pigments have been subjected to severe chemical reactions, which have entirely changed their original colours. Optical microscopy, PIXE and microbeam-PIXE have been used for determination of the nature of pigments, their chronology, and identification of domestic and imported materials. Paint flakes from various archeological sites in Egypt were analyzed: we report the results of the analysis of samples which were collected at the Mortuary Temple of Ramesses III (Habu Town), and the tombs of Tuthmosis III (Valley of the Kings) and Sennefer (Valley of the Noblemen). The paint is composed of grains of sizes typically ranging from 50 μm to 300 μm embedded in binding material and has great non-uniformity of pigment depth and lateral distributions and discontinuity of the paint layers. Qualitative analysis using broad beam PIXE has been performed to allow determination of the average composition of both support and pigments. Microbeam-PIXE has been used for mapping of selected grains. Goethite FeO(OH) (yellow), orpiment As₂S₃ (green), and the two blues: Egyptian Blue CaCuSi₄O₁₀ and Green Frit CaCuSiO₃ (mixed with the red haematite Fe₂O₃) were identified, and interesting details of the painting technique of ancient masters, like blending of pigments and the use of multilayer structures, were revealed.     

CT combined with arterial portography. A sensitive method for evaluation of liver tumors

During the period 1994-95, 22 patients were examined with CT during arterial portography for evaluation of hepatic tumours. The majority, 20 patients, had metastases from colon cancer. All patients were candidates for liver resection. In the series of patients described here, this process detected additional lesions in four more of the patients than found with any other imaging techniques. This supports that CT during arterial portography is the most sensitive method for detecting small malignant hepatic tumours, and for localizing them in relation to liver segments and major vascular structures. Optimal results are obtained in the absence of diffuse parenchymal disease and portal hypertension. Non-tumourous perfusion defects limit the accuracy of this technique, but such defects have characteristic locations and appearance. In difficult cases the technique should be correlated with ultrasonography and MR.     

New PTCR thermistors,switching current,and electromagnetic shielding effectiveness from nanosized vanadium sesquioxides ceramic reinforced epoxy resin nanocomposites

A new polymer nanocomposites of an epoxy resin matrix with randomly dispersed nano‐vanadium sesquioxides (V₂O₃) in various amounts were prepared. The structure of the nanocomposites were characterized by scanning and transmission electron microscopy (SEM and TEM), X‐ray diffraction, hardness, packing factor, extent of filler reinforcement, glass transition temperature, and sound velocity. The percolation threshold in the conductivity of the composites is lesser than 8 wt % and the dielectric constant can reach as high as 103. The resistivity—temperature curve of the composites shows a positive temperature coefficient (PTC) effect. The thermal stability of the composites was examined in terms of thermal gravimetry and differential scanning calorimetry (TG and DTA) and isothermal resistivity–time check. Because of the interfacial interaction among filler particles and the epoxy matrix, the nanocomposites exhibit higher thermal stability. The current–voltage–temperature curves behave as switching current. The temperature increases linearly with the applied voltage which makes this PTC nanocomposites very useful for temperature probe. Finally, electromagnetic interference shielding effectiveness (SE) values have been calculated and measured for the nanocomposites in the frequency range 1–12 GHz. It is found that the SE properties of the nanocomposite improve with increase in wt % of V₂O₃. A maximum SE of 42 dB for V20 sample at 12 GHz has been achieved. These nanocomposites are potentially useful in suppression of electromagnetic interference and reduction of radar signature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Facile green synthesis, optical and photocatalytic properties of zinc oxide nanosheets via microwave assisted hydrothermal technique

Novel hexagonal two dimensional ZnO nanosheets were successfully and economically synthesized using zinc acetate and urea based on a facile microwave hydrothermal method. The structure, morphology and size of the ZnO nanosheets were investigated by X-ray diffraction (X-ray), field emission scanning electron microscopy (FESEM), energy dispersive analysis of x-ray (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Fourier transform infrared spectroscopy (FTIR). X-ray analysis showed that the obtained ZnO nanosheets are crystalline corresponding to the pure ZnO phase with an average particle size of 12 nm. Optical properties of ZnO nanosheets were investigated by UV-Vis absorption and photoluminescence (PL) techniques. The band gap energy of ZnO nanosheets was found to be 3.29 eV. The photoluminescence (PL) measurement shows a strong UV emission, blue emission and blue-green emission bands. ZnO nano sheets possess a higher photocatalytic activity leading to the degradation of methylene blue (MB). The ZnO nanosheets are expected to have new opportunities in vast research areas and for application in catalysts and optoelectronic devices.