فصلنامه نانو مواد
پیاپی 12 (زمستان 1391)

LaNi0.6Fe0.4O3 and LaNiO3 perovskite nano-structures successfully prepared by polymeric sol-gel method using nitrate salts as precursors. The thermal analysis of prepared nano-powders was detected by means of thermogravimetric-differential thermal analysis (DTA-TG). X-ray diffraction (XRD) technique were used to recognize the obtained products and phases after thermal treatments. Microstructure properties were characterized by scanning electron microscope (SEM). p type and ntype semi conduction of samples were recognized by using Four Point Probe standard method. Results show the decomposition of precursor to 750 °C and formation of pure perovskite structures with general formula (ABO3). Also, the existence of nickel in the structure has been inhibited the crystallites growth. Particle size was increased with substitution of iron. Detected structure for LaNi0.6Fe0.4 3 rhombohedral and its semiconduction is p-type, which is same as LaNiO3 structure.

The traditional picture of the interfacial transition zone (ITZ) in concrete involves an approximately 30 μm zone around each aggregate, within which the porosity increases as the aggregate interface is approached. The ITZ microcracks in concrete will grows to visible cracks, thus they are very important to be studied. Effect of nano-SiO2 on cracks width in ITZ was studied in this research. For investigation of crack width, SE signals of SEM were used. The samples were cut from edges and middle of 5×5×5 cm cubic specimens. It was seen that nano-SiO2 could less the crack width. It is for the first time that SE use for ITZ imaging. Finally it was shown that adding nano-SiO2 could reduce the width of ITZ cracks.

In injection molding process, the feedstock rheological properties are key features which influence the steady flow and the uniform filling into the mold. For this purpose a binder system containing paraffin wax (PW), bees wax (BW), and stearic acid (SA) was selected and flow characteristics of the compound of aforementioned binder and pure Mg-Al2O3 nanocomposite powder via a rotary rheometer at the shear rate of 0.1-1000 s-1 and the temperature of 84 °C, parameters of injection molding and debinding were investigated. The results indicatedaddition of nano Al2O3 till 2.5 wt.% improves rheological behavior. Also, by studying the condition of injection molding and debinding, it reveals that the temperature of 100 °C and pressure of 90bar and a graphite bed under usual atmosphere are suitable.

In recent years, there has been a tangible research diligence in improving food and pharmaceutical industry applying protein nano-particles as carriers for various molecules. Fluidized bed adsorption is an expedient technique for purification of nano-structure bioproducts, has been broadly employed in the past two decades. In the present work, the expansion and hydrodynamic properties of a fluidized bed adsorption for attaining the optimal purification conditions of egg-albumin nano-particle using anion exchange adsorbents wereinvestigated. The residence time distribution (RTD) measurement is a conventional method frequently used to infer hydrodynamic properties in a fluidized bed adsorption. Using measurements of residence time distributions, hydrodynamic properties in the expanded beds were evaluated. The effects of the bed expansion degree, column diameter and settled bed height on the hydrodynamic properties were investigated. It wasrevealed that axial dispersion coefficient (Daxl) increased with increasing bed expansion degree, column diameter and settled bed height. Additionally, dynamic binding capacity for the egg albumin nano-particles upon streamline DEAE adsorbent was analyzed. The results showed that the dynamicbinding capacity was decreased with the increasing of flow velocity. Subsequently, egg-albumin nano-particles were exerted to the column. The yield of egg-albumin nano-particle recovery under optimal condition was 80.79%, which is a noticeable result in ion exchange chromatography.

Mullite-silicon carbide composite was fabricated via two-step sintering process to achieve high density and low grain growth. In this work, 5 and 10 wt.% nano and micro silicon carbide was used to investigate the effect of percent and grain size of reinforced phase on microstructure of desired composite. The reinforced phase suppresses the grain growth by Zener mechanism. The grain size of composite was lower by addition of nano-silicon carbide but enhancement of body density in contrast with micro silicon carbide was difficult. Notwithstanding of suppression of grain growth, it was prevented to reach high density by applying 10 wt.% silicon carbide.

In this study, mullite-zirconia composites were fabricated by reaction-sintering method. Besides, the slip casting was used for forming of these composites. Then, the effect of nano-Cr2 3 addition on the properties of these composites was investigated and the results were compared with microsized Cr2O3. Hence, the physical and mechanical properties, phase composition and the microstructure of these composites were investigated. The result showed that Cr2O3 can reduce porosity and increase density by the formation of liquid phase which, the nano-sized type has higher effect. Besides, 0.5 wt.% Cr2O3 can increase the bending strength of composite which, the nano-sized type is effective than other. The height amount of this additive can produce high content of amorphous phase and then decrease of bending strength. On the other hand, the grain size of zirconia tends to decreasing due to liquid phase formation. Corresponding to XRD results addition of Cr2O3 can reduce amount of tetragonal phase which, the nano-sized type is effective than other.

In this research, the structural characteristics of hematite nano-particles synthesized by a wet ball milling have been investigated. The evolution of morphology and microstructure of the powders during milling was investigated using SEM, TEM and XRD. The crystallite size was evaluated by XRD patterns using Williamson-Hall methods. The lattice strain of hematite powder synthesized by this method increase with a increasing of milling times, while the average particle size decrease. However, XRD and TEM estimated the average particle size of the hematite nanoparticles about 30 and 12 nm, respectively. Also the uniform dispersion and spherical powder morphology, is well visible in SEM image. Finally, the synthesis results using wet ball milling and sol-gel method has been compared.

In this research, the properties and morphology development of gold nano-layer coat builds on fuel cell bipolar plates via Sputtering method were investigated. Morphology and surface microstructure of samples were investigated by scanning electron microscopy (SEM) and atomic force microscopy. Also in order to evaluate the electrical conductivity of the coated samples, electrical resistance were measured. Scanning electron microscopy results implies the formation of the gold nano-layer with appropriate and smooth morphology on surface. Also, according to test results of electrical resistance, resistance of samples coated with 20 nm thick layer of gold was about half the resistance of uncoated samples, And this issue represents a significant increase in the electrical conductivity of the coated samples.