فصلنامه نانو مواد
پیاپی 5 (بهار 1389)

In this paper, we report the synthesis of SnO2/ZnO composite nanofiberous mat via electrospinning method by sol-gel process. In addition, the effect of electrospinning voltage and PVA concentration on the morphology, size and distribution of nanofibers diameter have been investigated. PVA/zinc acetate/stannous chloride nanofiber was electrospun from the solution containing PVA, zinc acetate and stannous chloride with various PVA concentrations in distilled water and was calcined in 650 °C for 6 hours obtaining SnO2/ZnO composite nanofiberous. Characterization of effective parameters on nanofibers morphology was performed by STA, XRD, SEM and EDX analyses. The diameter of nanofibers was found to be 75 nm. The results showed that the SnO2/ZnO composite nanofiberous have both phase and chemical purity.

In this study, we demonstrate that Markov processes play a fundamental role in probing rough surfaces and characterizing their topography. The surface topography obtained by a probe, as in the atomic force microscopy (AFM) technique, is based on the probe–surface interactions. When the size of the probe tip is comparable with the height of the surface fluctuation, the surface image can be aberrated from its origin. Due to the tip effect, there is a crossover in the structure function of the surface. For scales smaller than the Markov length— the minimum length scale over which a process is Markovian—the stochastic function that describes a rough surface is non Markovian, whereas for length scales larger than the Markov length, the surface may be described by a Markov process. Synthetic rough surfaces generated by fractional Guassian noise (FGN), as well as the rough surface of V2O5, obtained by AFM, confirm this.

In the present work, alumina-titania nanostructure powder used for prepared Al2O3-20 wt%Al2TiO5 composite by reaction sintering process. For reaction sintering, samples sintered at 1300, 1400, 1500 °C. Results of XRD showed that in the all of tempretures formed primary phases of Al2TiO5 and Al2O3. When samples sintered at 1500 °C, density increased until 96.9 % theorytical density. SEM proved proper interface between Al2TiO5 and Al2O3 grains. Results of hardness and toughness tests show when temperature increased from 1300 °C to 1500 C, hardness and toughness increased to 8.5 MPa and 4.28 MPam1/2, respectively.

Hydroxyapatite is the main mineral part of natural bone tissue with nanometric structure scale. In its chemical compound, there are different iones that magnesium and carbonate are most important of them. This iones cause changes in hydroxyapatite from stoichiometry state to biologic hydroxyapatite. In order to investigation of the effect of magnesium and carbonate on hydroxyapatite structure, first hydroxyapatite with magnesium and hydroxyapatite with carbonate were synthesized by wet chemical deposition. Then, structural changes were studied by SEM, FTIR and XRD. The results showed magnesium decreased the size of c-axis and increased the size of a-axis of hydroxyapatite unit cell parameters and carbonate with more effect cause to increase the c-axis and decrease the a-axis. Also, the presence of both iones causes reduction of crystallinity of hydroxyapatite. Investigation of the synthetic samples showed that the particles size got smaller around 30-100 nanometer with presence of magnesium and carbonate lattice of crystal.

In this paper, iron chloride (FeCl3·6H2O, Merck), sodium hydroxide (NaOH, Merck), polyvinylpyrolidone (PVP) and deionized water as solvent at 50 ºC were used as precursor for sonochemical synthesis of iron oxide nanostructures. The solutions of NaOH and FeCl3·6 2O with the appropriate concentrations were prepared and the reactions is completed for 1.5 h. Sonication of the solution was performed by a sonicator (20 kHz) and ultrasound intensity of sonicator is set on different intensity. Iron oxide nanostructures were prepared when the chemical reaction was done. The precipitated particles were collected, filtered and washed thoroughly with the methanol and double distilled water to remove by-products. All the investigated samples were dried in air at 100 ºC for 4 h. The iron oxide nanostructures were characterized by X-ray powder diffraction (XRD) and the thermogravimetric and differential thermal analysis (TG-DTA) for crystallization temperature. The size and the morphology of iron oxide nanostructures were characterized by transmission electron microscopy (TEM). The obtained results show that the average size of the particles of γ-Fe2O3 is between 20 to 50 nm.

Zinc acrylate epoxy nanocomposites were prepared using a zinc acrylate and a bifunctional deglycidyl ether of bisphenol A as a epoxy resin. The nanocomposites were based on spherical TiO2 and clay nanofillers with various filler loadings and processed by shear mixing. After mixing procedure¡ the nanocomposites were moulded into a mould and then cured in presence of curing agent. Finally some specimens were fabricated to characterize mechanical properties. The experimental results showed that by increasing nanofillers¡ fracture toughness of the nanocomposites significantly raised indicating a toughening impact resulted from the nanoparticles. Tensile strength also increased by increasing of TiO2 and clay loading. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied to reveal structural evolutions and the morphology of the nanocomposites and the results showed that the nanocomposites possessed a high level of homogeneity resulted from a sufficient dispersion of nanoparticles in the resin matrix. Also as a result¡ spherical nanoparticles had better mechanical properties compared to sheet-like nanoparticles.