Co-doping effects of (Al,Ti, Mg) on the microstructure and electrical behavior of ZnO-based ceramics

Co-doped ZnO-based ceramics using Al, Ti, and Mg ions in different ratios were synthesized with the objective to investigate the doping effects on the crystalline features, microstructure and the electrical behavior. For Al and Ti doping, a coexistence of crystalline phases was shown with a major wurtzite ZnO structure and secondary spinel phases (ZnAl₂O₄, Zn₂TiO₄, or Zn_aTi_bAl_cO_d), while Mg doping did not alter significantly the structural features of the wurtzite ZnO phase. The electrical behavior induced by Al, Ti, and Mg co-doping in different ratios was investigated using Raman, electron paramagnetic resonance (EPR) and ²⁷Al and ⁶⁷Zn solid-state nuclear magnetic resonance (NMR). Al doping induces a high electrical conductivity compared to other doping elements. In particular, shallow donors from Zn_i-Al_Zn defect structures are inferred from the characteristic NMR signal at about 185 ppm; that is, quite far from the usual oxygen coordinated Al. The Knight shift effect emanating from a highly conducting Al-doped ZnO ceramics was considered as the origin of this observation. Oppositely, as Ti doping leads to the formation of secondary spinel phases, EPR analysis shows a high concentration of Ti³⁺ ions which limit the electrical conductivity. The correlation between the structural features at the local order, the involved defects and the electrical behavior as function of the doping process are discussed.     

Yielding behaviour of thermoplastic/elastomer blends cured by gamma irradiation

Mechanical blends of thermoplastic medium density polyethylene (MDPE) and elastomeric ethylene propylene diene monomer (EPDM) have been prepared with a fixed composition of 60/40 wt%. They have been used either in their gum form or loaded with two different reinforcing fillers, high abrasion furnace (HAF) carbon black or precipitated SiO₂ (Hi Sil) of concentration 25–100 phr (parts per hundred parts of resin) with respect to the blend. Curing was achieved by gamma irradiation. Yielding properties (yield stress, yield strain and cold drawing) have been followed as a function of irradiation dose for different blend compositions. Yield stress values increased with irradiation dose and with the content of the reinforcing filler, but yield strain and cold drawing values decreased with irradiation dose and also with the filler content. The data obtained reveal that Hi Sil is more effective as a reinforcing filler, and the prepared blends are suitable for load‐bearing applications. © 2001 Society of Chemical Industry     

Swelling and electrical properties of rubber vulcanizates loaded with paraffin wax

The influence of the concentration of paraffin wax on the penetration rate, P, and the average diffusion coefficient, D, of kerosene in an SBR–NR composite and also on the coefficient of viscosity were investigated. All decreased with the addition of wax. Also, the effect of the concentration of paraffin wax on both the current–voltage characteristics and the temperature dependence of the dc electrical conductivity were studied. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3169–3177, 2001     

Corrosion Inhibition and Adsorption Behavior of Sodium Lauryl Ether Sulfate on L80 Carbon Steel in Acetic Acid Solution and Its Synergism with Ethanol

The application of sodium lauryl ether sulfate (SLES) as an anionic surfactant and its synergistic combination with ethanol for inhibition of corrosion of L80 carbon steel in acetic acid solutions were investigated by means of potentiodynamic polarization measurements, scanning electron microscopy (SEM), X‐ray diffraction (XRD), and energy‐dispersive X‐ray (EDX) investigations. The inhibition efficiency increases with an increase in concentration of SLES. The adsorption of SLES on the surface of L80 carbon steel obeys the Freundlich isotherm. SLES acts predominately as an anodic inhibitor. XRD, EDX, and SEM examinations of the electrode surface confirmed the adsorption of SLES on the electrode surface. The addition of ethanol with SLES significantly enhances the inhibition effectiveness and generates a strong synergistic effect.     

Solvent and Extraction Conditions Control the Assayable Phenolic Content and Antioxidant Activities of Seeds of Black Beans,Canola and Millet

The effects of extraction solvent and conditions on the total phenolic content (TPC) and antioxidant activity of black beans, canola and foxtail millet were investigated. The antioxidant activity was assayed using 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity (DRSA) and oxygen radical absorbance capacity (ORAC). Four solvent systems, namely 70 % acetone, 80 % ethanol, 80 % methanol and a mixture of acetone/methanol/water (7:7:6, v/v/v) were used. The extraction methods adopted in this study included refluxing, homogenization, cold extraction and sonication. The TPC as measured using the Folin Ciocalteu's method were 12.35–28.39, 2.43–16.73, and 1.78–5.06 µmol catechin equivalents/g dry matter (dm) for canola, black beans and foxtail millet, respectively. Aqueous acetone afforded the highest TPC for black beans and canola. Within the same solvent system used, the TPC, DRSA and ORAC obtained from different extraction techniques differed for black beans, canola and foxtail millet. The results demonstrated that the solvent system as well as method influenced the extraction of phenolic compounds and their antioxidant activities, depending on the type of matrix in which phenolics were embedded.     

Influence of Single-Walled Carbon Nanotubes on the Performance of Poly(Azomethine-Ether) Composite Materials

The present work is aimed to fabricate a new set of composite materials containing conducting poly(azomethine-ether) reinforced with single-walled carbon nanotubes in the form of single-walled carbon nanotube/poly(azomethine-ether)_1–5 for excellent enhanced thermal as well as conducting behavior of poly(azomethine-ether). Single-walled carbon nanotubes of variable loading have been embedded into conducting poly(azomethine-ether) using in situ polymerization technique. Before attempting the polymerization, 1,3-thiazole established poly(azomethine-ether) and its conformable monomers have been prepared and their chemical structures have been correlated by spectral analyses. Furthermore, η_inh and M_w values for poly(azomethine-ether) were found 0.89?dL?g^?1 and 39723.6, respectively. The fabricated single-walled carbon nanotube/poly(azomethine-ether)_1–5 composites were specified and characterized by wide-angle X-ray diffraction patterns, Fourier transform infrared spectroscopy, thermal behavior, scanning electron microscopy, and transmission electron microscopy characterization techniques. A perfect indicative response for this composite material was estimated by Fourier transform infrared spectra and X-ray diffraction as well. Both techniques displayed all intensive characteristic peaks regarding single-walled carbon nanotubes and poly(azomethine-ether) in the spectra or diffraction pattern for single-walled carbon nanotube/poly(azomethine-ether)_1–5. The role of single-walled carbon nanotubes on the performance of poly(azomethine-ether) was considerably examined. Single-walled carbon nanotube/poly(azomethine-ether)_1–5 showed relatively higher thermal stability. Single-walled carbon nanotube/poly(azomethine-ether)₁ displayed the lowest final composite degradation temperature value (552°C), whereas single-walled carbon nanotube/poly(azomethine-ether)₅ displayed the highest value (621°C). T₁₀ and T₂₅ values showed a gradual temperature increased while single-walled carbon nanotubes increased. Single-walled carbon nanotube/poly(azomethine-ether)₁ showed the lowest thermal stability and single-walled carbon nanotube/poly(azomethine-ether)₅ showed the highest thermal stability between all fabricated products. Furthermore, transmission electron microscopy images showed a prominent increase in single-walled carbon nanotubes diameters (40–60?nm). The conductivity values were significantly increased while single-walled carbon nanotubes content was increased and reached to the semiconductors. ε′ values were also increased in both single-walled carbon nanotube/poly(azomethine-ether)_4,5 which have higher single-walled carbon nanotubes content.     

Fabrication of core–shell nanocomposites with enhanced photocatalytic efficacy

The current study establishes the unprecedented involvement in the evolution and production of novel core–shell nanocomposites composed of nanosized titanium dioxide and aniline‐o‐phenylenediamine copolymer. TiO₂@copoly(aniline and o‐phenylenediamine) (TiO₂@PANI‐o‐PDA) core–shell nanocomposites were chemically synthesized in a molar ratio of 5:1 of the particular monomers and several weights of nano‐TiO₂ via oxidative copolymerization. The construction of the TiO₂@PANI‐o‐PDA core–shell nanocomposites was ascertained from Fourier transform IR spectroscopy, UV–visible spectroscopy and XRD. A reasonable thermal behavior for the original copolymer and the TiO₂@PANI‐o‐PDA core–shell nanocomposites was investigated. The bare PANI‐o‐PDA copolymer was thermally less stable than the TiO₂@PANI‐o‐PDA nanocomposites. The core–shell feature of the nanocomposites was found to have core and shell sizes of 17 nm and 19–26 nm, respectively. In addition, it was found that the addition of a high ratio of TiO₂ nanoparticles increases the electrical conductivity and consequently lowers the electrical resistivity of the TiO₂@PANI‐o‐PDA core–shell nanocomposites. The hybrid photocatalysts exhibit a dramatic photocatalytic efficacy of methylene blue degradation under solar light irradiation. A plausible interpretation of the photocatalytic degradation results of methylene blue is also demonstrated. Our setup introduces a facile, inexpensive, unique and efficient technique for developing new core–shell nanomaterials with various required functionalities and colloidal stabilities. © 2018 Society of Chemical Industry     

Microstructure and phase composition of cordierite-based co-clinker

The aim of this work is to study the effect of phase composition and microstructure of cordierite-based co-clinkers on the electrical properties and coefficient of thermal expansion of cordierite briquettes. To achieve this aim talc and kaolinite samples were collected from quarries in the Egyptian desert. The samples are characterized using XRD, XRF, polarized light, cathodoluminescence and SEM microscopy attached with EDAX, in addition to X-ray micro-computed tomography (3D- µXCT). The electrical properties and coefficient of thermal expansion of the cordierite briquettes are determined using HiTESTER instrument and automatic Netzsch DIL402 PC dilatometer, respectively.Five talc-based batches were shaped and fired in the temperature range 1000–1350 °C for 2 h. The microstructural and physical characteristics of the resulted cordierite-based co-clinkers depend mainly on the viscosity of the liquid phase developed during firing. The microchemistry of the cordierite briquettes confirms their enrichment of both cordierite and ferroan-cordierite crystallized directly from locally developed melts. The dielectric constant and loss factor values for cordierite briquettes allow their possible use as insulator components in electronic applications.     

Sol-Gel Preparation and Spectroscopic Properties of Modified Sodium Silicate /Tartrazine Dye Nanocomposite

Silicon - Thin film nanocomposites of sodium silicate (80 SiO2 –20 Na2O)/ tartrazine dye (E102) prepared using sol gel process in acidic system. The change in the physicochemical properties...     

Influence of balancing of internal combustion engines on the operating conditions of hydrodynamic bearings

We studied the influence of balancing internal combustion engines on the performance of hydrodynamic plain bearings. A non-linear approach makes it possible to calculate the forces of pressure generated by the lubricant film. This approach is coupled with a dynamic calculation, which determines the inertia forces of the rod. The counterweight to balance the engine is applied to the heads of rods and not to the crankshaft. We chose three models of connecting rod (rod of an engine in series, rod with partial and rod with complete counterweight). To determine the lubricant pressure field in the bearing, the modified Reynolds equation was solved using the finite difference method, taking into account the boundary conditions of Reynolds. Since the bearing is subjected to a variable load, the mobility method was used to facilitate the resolution of the Reynolds equation. The proposed numerical simulation allowed us to analyze the influence of counterweight applied to the connecting rod head on the variation of the lubricant pressure field, the minimum film thickness, the axial flow and the friction torque in the big end bearing during the operating cycle.