فصلنامه نانو مواد
پیاپی 2 (تابستان 1388)

In present work, Al2O3/0.5 wt% Ag nanocomposite was synthesized by using gelcasting process from water soluble precursors in order to provide the second phase. Silver nitrate is used as the source of silver nanoparticles in alumina matrix. With investigating the several dispersants on the rheology properties of the slurry, it was found that the Dolapix ET85 with appropriateconcentration 1.5 wt% is the best dispersant. The existence of silver nanoparticles and homogenous dispersion of these particles in alumina matrix was investigated by scanningelectron microscopy (SEM), energy dispersive spectroscopy (EDX), and transmission electron microscopy (TEM) images revealed that the average particle size of silver nanoparticles was about 10 nm.

Different industries like petrochemical served alumina by their excellent catalytic, moisture absorbing, resistance to wearing and refractoriness properties. General method such as sol-gel is relatively expensive for synthesis of alumina nanopowder. Bayer liquor is a cheap and industrial precursor that can decrease the cost of production. This method can be done by Bayer industrial route. Bayer method precipitated gibbsite (Al(OH)3) from seeded sodium aluminate solution under basic conditions. Alumina powder with high purity obtained after calcinations. The powders were investigated by DTA, XRD, zetasizer, EDAX and TEM and showed the successful synthesis of alumina nanopowder with bayer method.

In this paper, hydroxyapatite (HA), flour-hydroxyapatite (FHA) and fluorapatite (FA) powders have been synthesized in nanometric scales by sol-gel method. Structural changes, morphology, phase analysis and in vitro behavior of powders were studied. According to the XRD and SAED results, increasing the fluorine precursor caused an increase in the degree of crystallinity and crystallite size. FT-IR results demonstrated the replacement of F- in OH- positions and formation of FHA or FA. SEM and zetasizer studies showed that increasing of fluorine amounts raised the aptitude for agglomeration. According to the direct measurement during TEM studies,the crystallite sizes were found to be between 20 and 50 nm. The samples with higher amounts of fluorapatite resulted in the increasing of cells counts in the fibroblast cell culture experiment. So, fluor ion has a positive effect on biocompatibility of FHA powders.

In this research, polystyrene foam is produced by batch process and saturation of inert gas to achieve a sudden thermodynamic instability. Also, foaming process of polystyrene aluminum oxide nanocomposite (as nucleating agent) with supercritical N2 (as foaming agent), nucleating condition, growth and mean size of bubbles is investigated by scanning electron microscopy (SEM) and compared with pure polystyrene sample. So, the cluster growth rate and bubble size in nanocomposite are compared with pure polystyrene. Results showed that presence of nanoparticles decreased the final size and growth rate of bubbles. Also, the size and distribution of bubbles in nanocomposites foams were more uniform than pure polystyrene foam.

In this study, the needle-like hydroxyapatite nanoparticles were prepared with aqueous solution of glutamic acid with a concentration of 0.2 M and 0.4 M via biomimmetic synthesis method. The Ca(NO3)2.4H2O and (NH4)2HPO4 were used as Ca and P precursors. The phase development and chemical structure were studied by XRD and FT-IR. Also, morphology of nanoparticles was investigated by SEM and TEM. Crystallinity of powders was decreased with increasing the amino acid. The characteristic peaks of hydroxyapatite were identified in the FT-IR spectra andXRD patterns of heat treated powders. Also, the FT-IR analysis revealed the presence of COOH- bonds of glutamic acid. TEM images showed the needle shape nanoparticles obtained after a heattreatment at 600°C. The particle size values measured by TEM was about 20-100 nm. The carboxylate, carbonyl and amides groups of proteins can be considered as the nucleation sites of needle shape hydroxyapatite nanoparticles obtained in this work.

Grain growth of nanostructured materials at room or elevated temperature is one of most important problems in the science of nanotechnology. Distribution of second phase particles is one of the most important methods for grain growth inhibition. In this paper a comprehensive study is performed to investigate grain growth and then mathematical calculation will be used todeclare the effect of alumina nanoparticles on the final grain size of an intermetallic compound of nanostructured RuAl. Results show that kinetic relationships such as D2- D2 0= kt would not be a suitable model for prediction of grain growth behavior of nanostructured matrixes.

Cross linking of high density polyethylene (HDPE) and high density polyethylene – clay nanocomposite was first performed via high energy electron beam (EB) irradiation. Then, both samples were cross linked with dicumyle peroxide (DCP) and the relation of polymer cross linkingmethod with electrical properties was analyzed by different methods. So, the gelcontent of samples was determined by solvent extraction. Degree of cross linking was evaluated by hot set apparatus. It was found that, in the same amount of gel content, electrical properties of samples prepared by two kinds of cross linking methods significantly differed. These results also obtained for the relation of electrical properties like volume resistance, dielectric constant and dielectric strength with gel content for the samples containing nano clay. In other words, most of electrical properties in electron beam irradiated samples showed little change, but there were more changes with gel content for chemical cross linked samples.