Ali Hassanzadeh

Surface modification of Fe3O4@SiO2 microsphere by silane coupling agent

In the present study, Fe3O4@SiO2 core–shell microspheres were prepared via two steps. First, Fe3O4 nanoparticles were synthesized by co-precipitation of Fe+3 and Fe+2 as reaction substrates and NaOH as precipitant. Second, the surface of Fe3O4 was coated with silica by hydrolysis of tetraethylorthosilicate as the silica source. Subsequently, in order to reduce the amount of interaction and the agglomeration of Fe3O4@SiO2 microspheres, the silica shell of these particles was modified by vinyltriethoxysilane as the silane coupling agent. The structural properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy analyses. The results indicated that the average sizes of Fe3O4 and Fe3O4@SiO2 particles were about 50 and 500 nm, respectively. Also, the surface characterization of Fe3O4@SiO2 microspheres showed that the silane coupling agent was covalently coupled with the silica surface.

Synthesis of SnO2 nanopowders by a sol-gel process using propanol-isopropanol mixture

A simple sol-gel process is proposed for synthesizing SnO2 nanopowders utilizing normal propanol and isopropanol mixture instead of just using normal alcohols such as ethanol, propanol or butanol for Sol preparation. No surfactant was used in this Sol preparation process. The structure of sol is studied by FT-IR-ATR technique. On altering propanol to isopropanol ratio, three different nanopowders were obtained. X-ray powder diffraction, high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction pattern (SAED) and BET techniques were used to characterize prepared powders. Results show that smaller grain size was obtained via altering alcohols ratio. In addition, Merck commercial SnO2 powder was also used as a reference material for comparing purposes; because it has nanometer scale (ca. 60 nm). HRTEM images show that obtained nanopowders were polycrystalline and their average diameters fall into the range of 6–80 nm. Finally, the effect of alkoxide ligand size through sol-gel synthesis on product particle size is discussed.

Poole-frenkel conduction in Cu/Nano-SnO 2 /Cu arrangement

It is well known thatmetal/Tin-dioxide/metal sandwich structures exhibit a field-assisted lowering of the potential barrier between donor-like center and the conduction band edge, known as the Poole-Frenkel effect. This behavior is indicated by a linear dependence of Iog J on V1/2, where J is the current density, and V is the applied voltage. In this study, the electrical properties of Cu/nano-SnO2/Cu sandwich structures were investigated through current-voltage measurements at room temperature. Also, an attempt to explore the governing current flow mechanism was tried. Our results indicate that noticeable feature appearing clearly in the current-voltage characterization is the Poole-Frenkel and space-charge-limited conduction mechanisms.

The effect of fast neutron and gamma irradiation on thermal, structural and colorant properties of 2,6-diaminopyridine.

The variation in structural, thermal and colorant properties of 2,6-diaminopyridine were studied using differential scanning calorimetry (DSC), UV-visible, NMR spectroscopies and powder X-ray diffraction techniques, before and after fast neutrons irradiation with 2.12 and 3.50 kGy and gamma irradiation with 136.16 Gy doses. Under fast neutron irradiation, the sample enthalpy values, and melting and boiling temperatures were varied with increase in the irradiation dose. But the variation in boiling temperature was more pronounced than that of the melting point. However, there was no drastic change in these transition temperatures. The kinetic parameters were calculated using free isoconversional and Kissinger analysis methods. Moreover, UV-visible spectra showed that fast neutron and gamma irradiations had destroyed the color of the title compound. The gamma irradiation showed similar effect on structural and thermal properties. Results are also shown where the intensity of XRD patterns strongly depends on the irradiation dose. According to the NMR results, it seems that the collision occurs between para-hydrogen of 2,6-DAP and fast neutrons.

(E)-N′-Benzyl­idene-p-toluene­sulfono­hydrazide

In the title compound, C14H14N2O2S, a novel sulfonamide derivative, an intramolecular C—H⋯O hydrogen bond generates an S(5) ring motif. The molecule adopts a twisted E configuration around the C=N bond. An intermolecular N—H⋯O hydrogen bond generates an R 2 2(8) ring motif. The dihedral angle between the rings is 85.37 (9)°. The H atoms of the methyl group have rotational disorder with refined site occupancies of ca 0.63/0.37. In the crystal structure, intermolecular N—H⋯O hydrogen bonds link neighbouring molecules into dimers which stack along the a axis with a centroid–centroid distance of 3.8856 (10) Å.

Investigation of thermal and dielectric properties of Fe3O4/high-density polyethylene nanocomposites:

High-density polyethylene nanocomposites containing Fe3O4 nanoparticles were prepared by employing melt mixing process. The amorphous Fe3O4 nanoparticles with average size about 50 nm were prepared by the conventional coprecipitation method from iron (ΙΙ and ΙΙΙ). Thermal and dielectric properties of high-density polyethylene and its nanocomposites were investigated via differential scanning calorimetry and electrochemical impedance spectroscopy. The crystalline structure of high-density polyethylene and Fe3O4/high-density polyethylene nanocomposite were studied by wide-angle X-ray diffraction, which confirmed orthorhombic crystalline structure. The results of thermal and dielectric analysis indicated that the addition of Fe3O4 nanoparticles to high-density polyethylene matrix leads to decreasing degree of crystallinity and improvement of dielectric constant.

Modified Brillouin function to explain the ferromagnetic behavior of surfactant-aided synthesized α-Fe2O3 nanostructures

The α-Fe2O3 nanoparticles have been synthesized using some surfactants in micro-emulsion method. Magnetization, M (H), of samples was measured at room temperature. Magnetic hysteresis loops were observed in all samples. A new magnetization function (H - A model) was offered to explain the field dependence of the magnetization behavior of α-Fe2O3. In this work, the magnetization curve of all samples was analyzed based on MBrillouin, MBrillouin-Akulov, and MBrillouin-(H - A) model. The experimental data have fitted with the MBrillouin-(H - A) model, and the best fitting parameters were analyzed.

3-(2-Chloro­phen­yl)-4-(4-nitro­phen­yl)-1H-1,2,4-triazole-5(4H)-thione

In the crystal structure of the title triazole compound, C14H9ClN4O2S, molecules are connected into centrosymmetric dimers by pairs of N—H⋯S hydrogen bonds. In addition, there are weak C—H⋯N hydrogen bonds stabilizing the crystal structure. The dihedral angles between the triazole ring and the two benzene rings are 73.0 (4) and 72.9 (4)°.