Yousef Al-Zeghayer

Enhanced magnetization of sol-gel synthesized Pb-doped strontium hexaferrites nanocrystallites at low temperature

Effect of Pb doping on the structural and low temperature magnetic properties of SrPbxFe12-xO19 (x = 0, 0.1, 0.2, 0.3, and 0.4), synthesized by sol-gel autocombustion technique, has been investigated. The powder samples were sintered at 800°C for 2 h in order to develop the stable hexagonal phase, characteristic of the SrFe12O19 structure. The consequences of Pb substitution (at iron sites) on various structural parameters like lattice constants, unit cell volume, crystallite size, and porosity have been discussed. Fourier transform infrared frequency bands were utilized to determine the formation of tetrahedral and octahedral clusters of M-type ferrites. Hexagonal texture of the grains, a characteristic of the hexagonal crystal structure of SrFe12O19, was refined by Pb substitution. The magnetic properties, determined using a vibrating sample magnetometer, revealed that saturation magnetization decreased, while coercivity was increased with the increase of Pb contents. However, the increased squareness ratio and hence the energy product motivate the utilization of these ferrite compositions where hard magnetic characteristics are required.The increased values of saturation magnetization were observed at reduced temperature of 200 K, attributable to the better spin alignments of individual magnetic moments at low temperature.

Immunomodulatory potential of Phlomis bracteosa

The present study reports the immunomodulatory activities of different crude fractions of Phlomis bracteosa . In case of immunomodulatory study, the ethylacetate fraction demonstrated significant modulatory effect for oxidative burst of polymorphoneutrophils and CHCl 3 crude fraction for the whole blood, while the aqueous fraction demonstrated reasonable inhibition. Hence, both the chloroform and ethylacetate fractions of P. bracteosa are suggested further for the isolation and identification of active constituents responsible for the observed effects.

Novel route for amine grafting to chitosan electrospun nanofibers membrane for the removal of copper and lead ions from aqueous medium

A novel step wise synthetic route was developed to prepare amine grafted nanofibers (AGNFs) affinity membrane. The chemical structure of the nanofibers (NFs) after grafting was studied by acquiring Fourier Transform Infrared (FT-IR) spectra and Carbon, Hydrogen and Nitrogen (CHN) data. The morphology of the NFs before and after grafting was studied by Field Emission Scanning Electron Microscope (FE-SEM). FT-IR and CHN data confirmed the introduction of new functional groups into the primary structure of chitosan (CH). FE-SEM showed denser membrane with no deterioration of the NFs morphology after grafting. The aqueous stability of the membranes was studied in distilled water. The AGNFs membranes showed good aqueous stabilities (with only ∼ 6% loss in weight until 24 h and remained stable thereafter) which was less than the weight loss by glutaraldehyde treated nanofibers (GNFs) (∼44% loss in weight until 24 h) and pristine NFs (100% loss in weight as soon as the NFs were immersed in distilled water). The maximum adsorption (qm) capacity of AGNFs for Cu (II) and Pb (II) was observed to be 166.67 mg.g-1 and 94.34 mg.g-1. The adsorption capacity of the present systems was much higher for Cu (II) when compared to the already existing conventional and chitosan adsorbents. This increased might be related not just to the size, but more potentially to the increase in the number of nitrogen binding sites (chelating sites). Nitrogen donates lone-pair of electrons for chelation. The combination of processing into nano size and amine grafting (AG) has significantly increased the adsorption capacity of CH NFs membrane.

Thermal Treatment Effect on Catalytic Activity of Au/TiO2 for CO Oxidation

A novel and well-organized study for the synthesis and enhanced catalytic activity of Au/TiO2 catalysts has been developed. A momentous improvement in the catalytic activity of Au/TiO2 in CO oxidation and preferential oxidation reaction by thermal treatment has been studied. Au/TiO2 catalyst (Au (1 wt.%) supported on TiO2) was prepared by conventional deposition-precipitation method with NaOH followed by washing, drying and calcination in air at 400 °C for 4 h. Thermal treatment of Au/TiO2 was performed at 450 °C under 0.05 mTorr. The activity of the catalysts has been examined in the reaction of CO oxidation and preferential oxidation (PROX) at 25-250 °C. The catalytic performance was found to be strongly affected by thermal treatment of the prepared catalyst prior to the reaction. Heat treatment after Au deposition has a positive effect on the CO oxidation performance. This is attributed to the introduction of a stronger interaction between the oxide and Au which improves the catalytic activity.

Ruderman-Kittel-Kasuya-Yosida Magnetic Interactions in Chemically Synthesized Zn-Fe-AlO Nanocrystallites

Chemically derived auto-combustion technique is employed to synthesize the Zn0.95-xFe0.05 AlxO (x=00.07 in 0.02 increment) nanocrystallites. X-ray diffraction studies of all compositions revealed the phase pure wurtzite crystal structure with space group P63mc. The lattice parameters and crystallite size is changed with doping of Al attributed to the diversity in size of ionic radii. Temperature dependent electrical resistivity shows a decreased trend with the rise of temperature, confirming the semiconductor nature of compositions. The lower resistivity and enhanced saturation magnetization values in Al doped compositions correspond to the increase in density of carriers. Carriers mediated RKKY interactions are found to observe for enhancement of magnetization.