فصلنامه نانو مواد
پیاپی 27 (پاییز 1395)

The nano-laminated ternary carbide of Ti3SiC2 is a group of ternary ceramics which has received special attention over the last decade due to their unique combination of metals and ceramic properties. In this research, Ti3SiC2 bulks have been synthesized by reactive melt infiltration of porous TiC performs fabricated by gel casting process and the effect of time and temperature of infiltration process on the formation of Ti3SiC2 was discussed. The phase formation and microstructure were investigated by XRD and SEM equipped with EDS system. The results demonstrated that the best temperature and time in order to produce Ti3SiC2 with high purity were 1500 °C and 90 min, respectively. Ti3SiC decomposed into Si and TiC in furnace atmospheres at temperatures above 1500 °C. It is found thatthe compositions of samples strongly depended on the time of infiltration and with increase the infiltration time, Ti3SiC2 decomposed to TiC compound. The microhardness results showed that the Vickers hardness value increased with increasing of TiC volume content. Vickers hardness increases to the maximum value of 21.3 GPa for Ti3SiC2-85 wt.% TiC. A composite of the Ti3SiC2-12wt.% SiC had a measured fracture toughness of 5.63 MPam1/2.

The biological approaches to synthesis of nanoparticles are better than chemical and physical procedures because of low energy expenditure. In this study, the extract of apple fruit used for biosynthesis of silver nanoparticles and the effect of these nanoparticles on pathogenic fungi of Cytosporachrysosperma, Fusariumbrachygibbosum, and Diaporthephaseolorum. To Apple fruit juice, the solution of 2 and 10 mM silver nitrate was added at room temperature and change the color from pale yellow to reddish brown was confirmed to silver nanoparticles. The formation of silver nanoparticles was confirmed by the presence of absorption peak at 450 nm using spectrophotometer. The particle size distribution and average size was measured by dynamic light scattering (DLS). Different densities of colloidal silver nanoparticles were added in PDA growth medium and the fungi were inoculated on it. The results showed that the silver nanoparticles with 10 ppm concentration were inhibited growth of hyphae of pathogenic fungi in PDA culture medium. The results of this study are green synthesis of silver nanoparticles with biological methods and without using of harmful chemical and the inhibitory effect of silver nanoparticles on some important plant pathogenic fungi.

Lanthanum manganite (LaMnO3) is one of the perovskite structures that show the electrical, magnetic and catalytic properties. In this research, the LaMnO3 nanopowder is prepared by solid state method and was calcined in different temperatures at 700, 800 and 900 °C. The result powders were investigated by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscope (FE-SEM) equipped with an energy dispersive X-ray spectrometer (EDX). XRD patterns showed that the producing of pure LaMnO3 needs at least 900 °C. As well, the results of FTIR approved the formation of perovskite structure. The images of FE-SEM displayed the morphology of particles changes with increasing of temperature and the amount of nanoparticles are more in lower temperature. Also, the agglomeration of the powders has been increased by rising the temperature due to crystals growth. The EDX images confirmed the presence of lantanium and manganese in all powders calcined at different temperatures.

In the past decade, polycarbonate has attracted great interest due to their excellent properties such as, physical, chemical, optical, thermal and mechanical properties and possibility for various applications in modern technology. In this work, polycarbonate-TiO2 nanocamposite films were prepared with different percentages. The structure of samples was studied by X-ray diffractometer. Thermal stability of the nanocomposites was studied by thermo-gravimetric analysis (TGA). The polycarbonate and polycarbonate-TiO2 nanocomposite films have been studied by different characterization techniques, viz. scanning electron microscopy (SEM), FTIR spectroscopy, UV-Vis. The mechanical properties were studied by Vickers microhardness and standard tensile testing techniques. The optical band gap values were found to reduce from 4.3 eV to 3.5 eV with increase in TiO2 content of nanocomposites. TGA curves showed that nanocomposite films have higher resistance to thermal degradation compared to polycarbonate. The microhardness value increases with increasing TiO2 nanoparticles in composite. The Vikers hardness test showed that hardness of samples increased from 11.7 for poly carbonate to 13.6 for nanocomposite film with 5%wt. titanuim oxide. The strain test showed 18% improvement in stability by increasing nano titanium oxide particle to polycarbonate.

The first four components nanocomposite was fabricated on titanium (Ti) substrate by electrophoretic deposition (EPD). The unique components including Chitosan (CS), Bioglass 45S5 (BG), hydroxyapatite (HA), and halloysite nanotube (HNT) were deposited in special limitation of effective parameters of EPD. The results of transmission electrom microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) presented formation of uniform nanocomposite deposition containing three-ceramic components dispersed in CS matrix with thickness of 28 μm. Furthermore, the results of potentio-dynamic polarization and electrochemical impedance (EIS) test depicted this four components coating increase corrosion resistance of substrate in corrected simulated body fluid (C-SBF). The nanocomposite deposition increased corrosion resistance of Ti substrate about 18 times.

This study was performed to compare the behavior of thermal shock resistance of two types of fivelayer functionally graded thermal barrier coatings. The substrate material was selected from 17 4 PH stainless steel. The first type¡ a typical five-layer coating with CoNiCrAlY layer as a bond coat and YSZ layer as a top coat and three layer between them contains a mixture of YSZઃ戊뀥 powder ratio is specified. In the second type¡ nanostructured YSZ layer as a top coat and the other layers is quite similar to the first. To compare these coatings with conventional coating¡ are examples of two-layer thermal barrier coatings were tested. Samples were prepared by plasma spraying in the natural atmosphere. Thermal shock test was carried out at a temperature of 950 °C for repeated five-minute intervals and then quenched in water with temperature about 25-20 °C and was continued to destruct all the samples. A visual spalling of 20 percent of the coat was considered as criterion for thermal shock resistance. Microstructural evaluation of samples after the thermal shock test was carried out by SEM equipped with EDS. Finally¡ it was observed that the thermal shock life-time of conventional FG-TBC was approximately 1.5 times higher than the conventional TBC. as well as the thermal shock lifetime of nanostructured FG-TBC was approximately 14% higher than the conventional FG-TBC.