In-situ formation of Al2O3/Al core-shell from waste material: Production of porous composite improved by graphene

Aluminum dross produced from aluminum industry was used to fabricate Al₂O₃/Al porous composites. The dross was milled for 20?h to obtain nano powder. The milled material was examined by TEM and XRD. Graphene (up to 4?wt%) was mixed with the dross and utilized to reinforce sintered composites. The milled powders were compacted then fired at various temperatures up to 700?°C. Physical properties in terms of bulk density and apparent porosity for sintered composites were tested using Archimedes method. SEM attached by energy dispersive spectrometer (EDS) was used to inspect microstructure and elemental analysis of sintered composites. Microhardness and compressive strength were also measured. Ultrasonic nondestructive technique was utilized to examine the elastic moduli. Electrical conductivity of sintered composite was also studied. During milling up to 20?h, Al₂O₃/Al core-shell was in-situ formed with size of 65.9 and 23.8?nm, respectively. The apparent porosity of sintered composites was improved with rising graphene percent while it decreased with increasing sintering temperature. Increasing of graphene mass percent and firing temperature led to remarkable increase in all mechanical properties and electrical conductivity. The maximum compressive strength, hardness, elastic modulus and electrical conductivity were 200?MPa, 1200?MPa, 215?GPa and 1.42?×?10^?5 S/m, respectively, obtained for composite sintered at 700?°C having 4?wt% graphene.     

Antimicrobial materials based on poly(ethylene-co-vinyl alcohol) and silver acetate produced by reactive extrusion

The use of silver as an antimicrobial agent has exhibited great interest in recent years. In this research, poly(ethylene-co-vinyl alcohol) (EVOH)–silver acetate-based antimicrobial materials were prepared at high temperature by reactive extrusion. Silver acetates were used without pretreatment. The thermal reaction of silver acetates in the material and their effect on the thermal and mechanical properties of the polymer were investigated as a function of their concentration. The dispersed silver acetate salts within the EVOH matrix have displayed a significant thermal reaction. This reaction of metallic salts was partial when the extrusion temperature was fixed at 190 °C and completed at 230 °C. The antimicrobial agents also had significant effects on the properties of the matrix. Reductions of glass temperature and storage modulus were observed by the analyses. All the variations were dependent on both the concentration of silver acetate and the extrusion parameters. The antimicrobial activity was studied and demonstrated a promising potential to create an antimicrobial material in a one-step solvent free extrusion method. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47799.     

Pressure effects on dynamics behavior of multiwall boron nitride nanotubes

The dynamic behavior of Multiwall boron nitride nanotubes (MWBNNTs) is investigated by employing multiple elastic shells model. The influences of van der Waals interactions on layers are shown as nonlinear functions of the interlayer distance of MWBNNTs. Governing equations are solved by using the developed finite element method and by employing time history diagrams. The radial wave speed from the outermost layer to the innermost layer is computed. The effects of geometrical factors such as diameter-to-thickness ratio on dynamic behavior of MWBNNTs are determined. The magnification aspects of MWBNNTs are computed, and the effects of surrounding pressures on wave speed and magnification aspect of MWBNNTs are discussed.     

Poly[ethylene‐co‐(vinyl alcohol)]‐graft‐poly(ε‐caprolactone) Synthesis by Reactive Extrusion, 1 ‐ Structural and Kinetic Study

Chemical modification of EVOH in the molten state at 185 °C by a grafting from process of poly(ε‐caprolactone) in batch was studied. ¹H NMR was used to characterize the structure evolutions of PCL grafts. In addition to grafting reactions, dynamic covalent transesterification reactions between EVOH residual alcohols and the polyester grafts led to a redistribution of the PCL grafts length. up to 27 and SR up to 80% were obtained. Experiments made in a corotating mini twin‐screw extruder also confirmed these results. The effect of the alcohol to caprolactone ratio and catalyst concentration (SnOct₂) on kinetic evolution showed that few minutes were necessary to complete the polymerization. A kinetic model was proposed and adequate conditions for the synthesis by reactive extrusion were defined.

     

Synthesis of Novel 2-Thiouracil-5-Sulfonamide Derivatives as Potent Inducers of Cell Cycle Arrest and CDK2A Inhibition Supported by Molecular Docking

In an effort to discover potent anticancer agents, 2-thiouracil-5-sulfonamides derivatives were designed and synthesized. The cytotoxic activity of all synthesized compounds was investigated against four human cancer cell lines viz A-2780 (ovarian), HT-29 (colon), MCF-7 (breast), and HepG2 (liver). Compounds 6b,d–g, and 7b showed promising anticancer activity and significant inhibition of CDK2A. Moreover, they were all safe when tested on WI38 normal cells with high selectivity index for cancer cells. Flow cytometric analysis for the most active compound 6e displayed induction of cell growth arrest at G1/S phase (A-2780 cells), S phase (HT-29 and MCF-7 cells), and G2/M phase (HepG2 cells) and stimulated the apoptotic death of all cancer cells. Moreover, 6e was able to cause cycle arrest indirectly through enhanced expression of cell cycle inhibitors p21 and p27. Finally, molecular docking of compound 6e endorsed its proper binding to CDK2A, which clarifies its potent anticancer activity.     

The Use of a Eutectic Mixture of Olive Pomace Oil Fatty Amides to Easily Prepare Sulfated Amides Applied as Lime Soap Dispersants

Sulfated diethanolamides of fatty acids are known to be effective lime soap dispersing agents. However, their preparation from fatty acids via fatty amides requires the use of organic solvents due to the high viscosity of both fatty amides and sulfated fatty amides. This study shows that the preparation of sulfated fatty amides is relatively easy when using olive pomace oil as the raw material. The latter, is converted into sulfated fatty amides by performing the following steps: saponification, hydrolysis, esterification, amidation, and sulfation. In the final step, the mixture obtained has sufficient fluidity, due to its high linoleic acid amide content, to obviate the use of organic solvents, as usually suggested in the literature. Characterization of the product was carried out by chemical analyses, FTIR, ¹³C NMR, GC, and HPLC. It was shown that the yield of the amidation reaction is about 80%, and that of the sulfation reaction can exceed 100% against the pure amide (more than one sulfate group could be linked to one amide molecule). On the other hand, the Borghetty test showed that the product is an effective dispersant with a lime soap dispersing power equal to five.     

On‐line opto‐viscoelastic analysis of polypropylene fibres using multiple‐beam Fizeau fringes in transmission and a modified creep device

A creep device attached to an automated multiple‐beam Fizeau system in transmission was modified with a designed digital ruler. This device allows on‐line measurements of fibre length during creep experiments in terms of an analogue voltage value. The influence of sustained stress values on creep deformation and optical properties (n^||, n^? and Δn) for polypropylene (PP) fibres was studied interferometrically. The opto‐viscoelastic properties of PP fibres were determined for three different values of constant applied stress of 11.536, 18.717 and 25.905 MPa, at room temperature. Also, the variations of the cross‐sectional area and Poisson's ratio were studied during creep extensions. The compliance curves were obtained as a function of both time and applied stresses. Empirical formulae are suggested to describe the creep compliance curves for PP fibres, and the constants of these formulae were determined and described at each applied stress. A Kelvin chain was used to model the mechanical behaviour of the PP fibres under study. The effect of strain on the mean refractive indices, orientation function density and crystallinity was investigated as a result of the recorded data. Microinterferograms are given for illustration. The modified creep device with the designed digital ruler enables one to obtain instantaneous automatic accurate recording of fibre length values during creep experiments. Calculation of refractive indices, orientation function and crystallinity shows a difference in material behaviour at small stresses from that at higher stresses which may be attributed to different strain rates caused by different stresses. Copyright © 2010 Society of Chemical Industry     

PVD Coating of Mg–AZ31 by Thin Layer of Al and Al–Si

Although magnesium alloys have the advantage of high specific strength, they have poor atmospheric corrosion resistance. An important method of improving the corrosion resistance is by applying a coating layer. In this work, the physical vapor deposition (PVD) technique is used for coating a magnesium (Mg) AZ31 sheet substrate with a thin layer of high purity aluminum (Al) and Al–12.6% Si. Aluminum is expected to be suitable as a coating layer on Mg sheets, due to its corrosion resistance and its formability. Before coating, the substrate was subjected to several consecutive surface preparations, including sand-blasting, mechanical grinding, mirror-like polishing, ultrasonic etching, and finally ion etching by magnetron sputtering (MS). PVD coating was conducted using a PVD machine with max electron beam power and voltage of 100 kW and 40 kV, respectively. This was either with or without plasma activation, and with variable substrate speeds ranging between 10 and 70 mm/s. During MS ion etching and coating, the substrate temperature increased. The substrate temperature increased with the application of plasma activation and with lower substrate speeds. The coating-layer thickness varied inversely with substrate speed. A thinner coat with finer morphology was obtained in the case of plasma activation. Other results included coating layer characteristics, diffusion between the AZ 31 substrate and the Al coating layer, adhesion of the coating layer to the substrate, and corrosion resistance by a humidity test.     

Effect of pH and zeta potential of Pickering stabilizing magnetite nanoparticles on the features of magnetized polystyrene microspheres

Styrene as a monomer was emulsified in water using several magnetite nanoparticles concentration and pH values. Emulsified styrene drops were used as templates for polymerization, in presence of water soluble free radical initiator, and formation of composite particles. Styrene template drops stabilization was verified by light as well as scanning electron microscopy imaging, which ensured the participation of the particles in building up a mechanical barrier to stop oil drops coalescence. Furthermore, the produced polystyrene composites were strongly attracted to an external magnet. The difference in particles size as a function of pH was elucidated using zeta potential measurements, which indicated dominance of pH on the hydrophilicity of the particles and consequently the extent of emulsification, which in turn affected the size of the obtained microspheres. Under some circumstances, capsules were formed instead of particles. Thereby, it can be concluded that the magnetic microspheres are optimally formed at pH 2.3 independently of the magnetite content used.