Sharif Digital Repository

PVDF/nanoclay nanocomposites were prepared via melt mixing method. The intercalated dispersion of the nanoclay in PVDF matrix was confirmed by XRD. According to FTIR, DSC and XRD results, the presence of nanoclay facilitated transition from α-to-β crystalline phase. Electron beam irradiation decreased the melting point of the nanocomposites. The decrease in melting point of the nanocomposites was about 11 C at 500 kGy. The crystallinity of nanocomposites increased at an irradiation dose of 100 kGy and decreased at higher irradiation doses. The extent of crosslinking of the nanocomposites increased significantly with irradiation up to 300 kGy. The nanoclay intensified the increase in yield... 

The effects of relaxation and nanocrystallization on magnetic properties of (Fe0.5Co0.5)73.5Si13.5B 9Nb3Cu1 ribbons have been investigated. Ribbons were melt-spun at wheel speed of 38 m/s and then annealed at different temperatures. The results indicated that the relaxation processes shift the Curie temperature of amorphous phase to the higher temperatures. It was also found that through crystallization phenomena the saturation magnetization increases due to the super-exchange between Fe and Co atoms in the crystalline phase. A slight variation in magnetization was observed at ~700 °lC during heating due to the ordering transition in FeCo system. At early stage of crystalline phase... 

The effects of different nano-SiO2 contents on the rheological properties of poly(vinylidene fluoride) (PVDF) solution and mechanical, thermal, structural, and piezoelectric properties of composite nanofibers were investigated. Results showed an increase in fiber diameter (∼125 to 350 nm) and ∼450% increase in tensile strength as the content of nano-SiO2 particles increased. The degree of crystallinity decreased by 19% as the nano-SiO2 content increased by 2% (w/w). Further investigation demonstrated that silica could significantly improve the piezoelectric properties of PVDF nanofibers as the output voltage showed an increase in the presence of silica attributed to change in the crystalline... 

Hydrolysis of titanium isopropoxide alcoholic solution has been used to prepare the crystallized TiO2 nanoparticles at low temperature. Concentration ratio was used to control the pathway of sol-gel process and change the physical characteristics of TiO2 nanopowders. The crystallinity, morphology and size of aged TiO2 nanopowders were studied by X-ray diffraction and Scanning Electron Microscopy (SEM). FTIR and, Thermo-Gravimetric (TG) analysis were used to identify the functional groups and thermal behavior of prepared samples. Experimental results have shown that high crystalline TiO2 nanomaterial with anatase polymorph can be obtained at room temperature. It has been found that the... 

Inverted perovskite solar cells (PSCs) have been introduced as better candidate for roll-to-roll printing and scale-up than their conventional configuration counterparts, while their fabrication is technically more demanding. The common light absorbing layer in inverted PSCs is the single cation methylammonium lead iodide (MAPbI3) perovskite, whereas mixed-ion perovskites are chemically more stable. In mixed-ion perovskites, where FA (formamidinium) is the main replacement for MA, the electron affinity is larger than in MAPbI3 perovskites, leading to possible barriers against photoelectron collection by the electron transporting layer (ETL). In this paper we report on a mixed-ion... 

Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of... 

Decreasing particle size results in larger increase of external surface area and shorter diffusion path, both reducing mass and heat transfer resistances in catalysis and sorption. A rapid high-temperature hydrothermal synthesis method was developed to synthesize uniform nanoparticles of SAPO-34 zeolite with high crystallinity. To investigate the effects of temperature and synthesis time on purity and crystallinity of the final products, the crystallization temperature was increased from 468 to 673 K while the synthesis time was decreased from 24 h to 45 min. The products were characterized by XRD and SEM techniques. It was found that high temperature and short synthesis time reduce the... 

Simple synthesis of silver doped TiO2 nanostructured layers by micro arc oxidation process is reported for the first time. The layers consisted of anatase and rutile phases whose characteristic XRD-peaks shifted toward lower diffraction angles when compared to the pure micro arc oxidized TiO 2 layers. Silver-doping was confirmed by XPS technique. The anatase phase crystalline size was determined as 27.6 and 21.8 nm for the layers grown under the voltages of 350 and 500 V. Employing a UV-Vis spectrophotometer, a red shift in the absorption edge of the layers was observed when silver was incorporated into the titania lattice  

In recent years, various nanocars have been synthesized in order to provide controlled mechanical function, transport other nanoparticles, or enable bottom-up assembly capability. There have even been racing competitions among well-known nanocars in which the wheels play an influential role. In this paper, the motion of thermally driven nanocars equipped with p-carborane wheels on Au(111) and Au(001) substrates is investigated. For the sake of comparison, classical all-atom molecular dynamics (MD) and rigid-body MD (RBMD) have been used to study the motion threshold as well as to analyze the effect of temperature, substrate crystalline direction, and chassis shape on the diffusive motion of... 

In recent years, various nanocars have been synthesized in order to provide controlled mechanical function, transport other nanoparticles, or enable bottom-up assembly capability. There have even been racing competitions among well-known nanocars in which the wheels play an influential role. In this paper, the motion of thermally driven nanocars equipped with p-carborane wheels on Au(111) and Au(001) substrates is investigated. For the sake of comparison, classical all-Atom molecular dynamics (MD) and rigid-body MD (RBMD) have been used to study the motion threshold as well as to analyze the effect of temperature, substrate crystalline direction, and chassis shape on the diffusive motion of... 

A simple, atom economy and highly efficient green protocol have been developed for synthesis of bis(indolyl)alkane by the reaction of indole derivatives with aldehydes and ketones in the presence of small amount of the heteropoly acids in water. © 2007 Elsevier B.V. All rights reserved  

CdS nanoparticles were grown using CdSO4 and Na 2S2O3 as the precursors and thioglycerol (TG) as the capping agent. TG was shown to exhibit a catalytic role in the reaction and also acted as a capping agent. It was demonstrated that size growth is linearly related to the temperature of the reaction, i.e.the sizes can be controllably adjusted by temperature. The crystalline phase of the nanocrystals was also dependent on the temperature of growth: higher temperature favours the cubic phase. The pH also plays an important role in nanoparticle growth, as lower pH leads to a higher release rate of sulfur species. At pH as high as 10, the growth rate remains slow even at boiling temperature. This... 

One-dimensional (1D) MgO structures were successfully synthesized via carbothermic reduction of mechanically activated mixture of MgO and graphite. Mechanical activation of source materials before carbothermic reduction can substantially enhance the formation of MgO products at a temperature (1000 °C) relatively lower than that required in previous approaches (≥1200 °C). However, the morphology of MgO formed is dependent on the degree of mechanical activation and the condition of the subsequent carbothermic reduction. Two distinctive morphologies were found for MgO products synthesized using our method: single crystalline nanorods with rectangular cross-sections whose diameters range from 50... 

The objective of this study was to evaluate the effects of P 2O5 particle size distribution on the crystalline phases and microstructure of lithium disilicate glass-ceramics derived from the TiO2-ZrO2-Li2O-CaO-Al2O 3-SiO2 system for dentistry applications. The samples were made via fusion and casting procedure. Crystallisation as well as the morphology and microstructure of the samples were investigated using X-ray diffraction, differential scanning calorimetric and scanning electron microscopy. The results showed that the crystallisation of the samples occurred in the range of 500-650°C. The main crystalline phase was lithium disilicate (Li2Si2O5) along with Lithium metasilicate (Li2SiO3),... 

In this study, lithium disilicate glass-ceramic in the TiO2-ZrO2-Li2O-CaO-Al2O3-SiO2 system was investigated for dentistry applications by incorporation of P2O5 and Nb2O5 as nucleation agent. The influence of the particles size (nano and submicron size) and nucleating agents on the crystalline phases, microstructure, crystallization mechanism and mechanical properties were investigated. Our data indicated that in ceramic glass with nano and submicron P2O5, the main crystalline phase was lithium disilicate. The results also showed that change of P2O5 particle's size had significant effect on the crystalline phases and microstructure. By replacement of submicron P2O5 with submicron Nb2O5,... 

Mechanical properties of materials are an important factor in designing nanoscale systems. Several researches and experiments have shown that the mechanical properties of the nano-scale materials are different from those of bulk. One of the major reasons for this difference is that the ratio of surface to volume increases at the nano-scale, and the effects of free surfaces become very important. In this paper, we have measured the surface elastic constants of silicon crystalline structure using different interatomic potentials. The potentials employed here are EDIP (Environment-Dependent Interatomic Potential), Stillinger-Weber and Tersoff, and also different crystalline orientations are... 

WO3 films with thicknesses between 550 and 853 nm were deposited on glass substrates using the electron beam evaporation method at room temperature. The microstructures and surface roughness of the films were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). It was observed that the crystalline structure of the WO3 thin films significantly changes from the amorphous to crystalline states with a crystalline texture, and the mosaicity and grain size dependent on the film thickness. The transmittance spectra of the obtained WO3 films were measured in the range from 340 to 850 nm, and the Swanepoel method was used to determine the refractive indices and the thicknesses of the... 

This study intends to replace polyethylene multi-layer films used in food packaging industry with single-layer polyethylene nanocomposites films. Nanocomposites of LDPE/LLDPE/ montmorillonite organoclay were prepared by melt compounding in a twin extruder and then film blown to prepare thin films. LLDPE-g-MA was used as compatibilizer to achieve better interaction between the blend and organoclay. Various compositions of organoclay and compatibilizer were prepared. The structure of nanocomposites was characterized by XRD and TEM. Permeability properties were measured using a permeability measuring set-up and aspect ratio of the particles was evaluated using permeability data. The results... 

WO3 films with thicknesses between 550 and 853 nm were deposited on glass substrates using the electron beam evaporation method at room temperature. The microstructures and surface roughness of the films were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM). It was observed that the crystalline structure of the WO3 thin films significantly changes from the amorphous to crystalline states with a crystalline texture, and the mosaicity and grain size dependent on the film thickness. The transmittance spectra of the obtained WO3 films were measured in the range from 340 to 850 nm, and the Swanepoel method was used to determine the refractive indices and the thicknesses of the...