Sharif Digital Repository

Different concentrations of CaF2 were incorporated in mica glass-ceramics to evaluate their effects on the crystallization and microstructure. The kinetics of phase transformations, and the microstructures of the final crystalline phase were found to be dependent on the concentration of nucleation agents. The results showed that CaF2 in high concentration had a synergistic effect and enhanced the formation of interlocked mica crystals. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses were changed in the range of 235-405 kJ/mol, while the crystallization activation energies of samples with addition of CaF2 were changed in the range of 419-747... 

In this study, tungsten oxide films were deposited by pulsed-laser deposition (PLD) technique. The as-deposited films were annealed at 250 °C in air for 1 h. The surface morphology, microstructure, crystalline phase, and chemical composition of the films were characterized by SEM, XRD and XPS techniques. Pt nanoparticles were deposited onto the tungsten oxide films through a two-step process. First of all, a layer of PtCl2 was coated on the WO3 surface by drop-drying the PtCl2 solution onto the WO3 surface at 60 °C. Consequently, the reduction of the PtCl2 into the metallic Pt nanoparticles was performed at 200 °C. In this study, the effect of the temperature during hydrogen reduction of... 

Over the last decade, nanoparticles used as protein carriers have opened new avenues for a variety of biomedical applications. The main concern for these applications is changes in biological activity of immobilized proteins due to conformational changes on the surface of the carrier. To evaluate this concern, the preparation and biocatalyst activity of α-chymotrypsin-Fe 3O4 @ Au core/shell nanoparticles were investigated. First, Fe3O4 @ Au core/shell nanoparticles were synthesized by coprecipitation method and citrate reduction of HAuCl 4. TEM imaging revealed a core size of 13 ± 3 nm and a shell thickness of 4 ± 1 nm for synthesized nanoparticles. X-ray diffraction (XRD) was used to study... 

Poly (vinylidene fluoride) (PVDF) nanocomposites were prepared via melt, solution, and co-precipitation mixing methods using Cloisite 30B as organoclay. The results from X-ray diffraction patterns display intercalation or exfoliation of nanoclay depending on the nanocomposite preparation method. The solvent cast and co-precipitated samples showed exfoliation, while intercalation was observed in the nanocomposites prepared by melt mixing. Introducing organoclay induced formation of β-crystals in the PVDF nanocomposites as evidenced by XRD and FT-IR. FT-IR analysis indicated that the samples prepared by the co-precipitation method had a higher tendency for β phase formation, while the sample... 

Crystallographic texture considerably affects the formability of crystalline materials. In this paper, the effects of BCC ideal rolling fibers—including α, ε, η, γ, and ξ fibers—on the sheet formability are numerically studied. The simulations are based on the numerical procedure developed by the authors in [1] in which a rate dependent crystal plasticity model along with the power law hardening are employed in a user material subroutine to model the behavior of crystalline materials. In order to determine FLD—in a M-K type approach—second-order derivative of sheet thickness variations with respect to time is used as necking criterion. The calculated FLDs of the fibers are compared with each... 

A metal-organic framework [Co3(BDC)3(DMF)2(H2O)2] was synthesized and structurally characterized. X-ray single crystal analysis revealed that the framework contains a 2D polymeric chain through coordination of 1,4-benzenedicarboxylic acid linker ligand to cobalt centers. The polymer crystallize in monoclinic P21/n space group with a=13.989(3) Å, b=9.6728(17) Å, c=16.707(3) Å, and Z=2. The polymer features a framework based on the perfect octahedral Co-O6 secondary building units. The catalytic activities of [Co3(BDC)3(DMF)2(H2O)2]n for olefins oxidation was conducted. The heterogeneous catalyst could be facilely separated from the reaction mixture, and reused three times without significant... 

Antibacterial activity of tungsten oxide nanorods/microrods were studied against Escherichia coli bacteria under visible light irradiation and in dark. A two-step annealing process at temperatures up to 390 °C and 400-800 °C was applied to synthesize the tungsten oxide nanorods/microrods on tungsten foils using KOH as a catalyst. Annealing the foils at 400 °C in the presence of catalyst resulted in formation of tungsten oxide nanorods (with diameters of 50-90 nm and crystalline phase of WO3) on surface of tungsten foils. By increasing the annealing temperature up to 800 °C, tungsten oxide microrods with K2W6O19 crystalline phase were formed on the foils. The WO3 nanorods showed a strong... 

A rapid, environmental friendly and low-cost method to prepare hydroxyapatite nanoparticles is proposed. In this method, hydroxyapatite is produced in a sonicated pseudo-body solution. The sonication time was found effective in the formation of the crystalline phase of nanoparticles. In our experimental condition, 15 min sonication resulted in the most pure hydroxyapatite phase. Also it was shown that growth temperature is a crucial factor and hydroxyapatite crystallizes only at 37 °C. The particles formed by sonication were generally smaller and more spherical than those obtained without sonication. Sonication increased the hydroxyapatite crystal growth rate up to 5.5 times compared to... 

Modified versions of the Zener drag equation were obtained by evaluating a non-random distribution of incoherent ceramic particles in a nano-crystalline material. Analytical investigation of particle-boundary correlation indicates that the limiting grain size would be proportional to fV -1/3 for fV larger than 2.96%. The limiting grain size can be obtained by a combination of random and non-random Zener drag pressure in the case of volume fractions smaller than 2.96%  

The molecular-dynamics analysis is presented for 3D compaction simulation of nano-crystalline metals under uniaxial compaction process. The nano-crystalline metals consist of nickel and aluminum nano-particles, which are mixed with specified proportions. The EAM pair-potential is employed to model the formation of nano-particles at different temperatures, number of nano-particles, and mixing ratio of Ni and Al nano-particles to form the component into the shape of a die. The die-walls are modeled using the Lennard-Jones inter-atomic potential between the atoms of nano-particles and die-walls. The forming process is model in uniaxial compression, which is simulated until the full-dense... 

A series of reduced graphene oxide/ZnxCd1-xS (RGO/ZnxCd1-xS) nanocomposites (0 < x < 1) with different ratios of Zn/Cd were synthesized via a facile hydrothermal route under optimized experimental conditions and were carefully characterized by various techniques. Because very little is known about the morphology, specific surface area, and crystal phase effects of RGO/ZnxCd1-xS crystals on their photoresponsivity, field-emission scanning electron microscopy (FE-SEM), BET surface area analysis and X-ray diffraction (XRD) data were studied to investigate their effects on photoactivity. Based on the results, a crystal phase transition from a cubic phase in RGO/Zn0.9Cd0.1S to a hexagonal... 

Gold (Au) nanoparticles are widely used in diagnosing cancer, imaging, and identification of therapeutic methods due to their particular quantum characteristics. This research presents different types of aqueous models and potentials used in TIP3P, to study the effect of the particle size and density of Au clusters in aquatic environments; so it can be useful to facilitate future investigation of the interaction of proteins with Au nanoparticles. The EAM potential is used to model the structure of gold clusters. It is observed that in the systems with identical gold/water density and different cluster radii, gold particles are distributed in aqueous environment almost identically. Thus, Au... 

A low cytotoxic metal–organic framework (MOF) UiO-66 (UiO stands for University of Oslo) and NH2-UiO-66, that showed high cell viability of HFF-2 via 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyl tetrazolium assay, was reported as an effective adsorbent (antidotal) agents. The structure of MOFs was confirmed by Fourier transform infrared, Field emission scanning electron microscopy (FESEM) and X-ray diffraction. Thermal behavior of MOFs was investigated using with thermogravimetric analyzer in nitrogen atmosphere to check the thermal stability. FESEM showed NH2-UiO-66 displayed symmetrical crystals with triangular base pyramid morphology, with the particle size around 100 nm and uniform size... 

Poly(vinyl alcohol)/graphene oxide mixed matrix membranes have been prepared and applied for the pervaporation of isooctane (aliphatic) and toluene (aromatic) mixtures. Characteristics of the membranes such as crystallinity, morphology, and swelling have been investigated, and the results have been used to describe pervaporation performance. Experimental tests evidenced that incorporation of low content of graphene oxide nanoplates (0.5 wt%) in poly(vinyl alcohol) increases affinity of the membrane to aromatics by S and π bonds and selectivity increase to about four times. Moreover, interaction of graphene oxide with toluene results in increasing of swelling and decreasing of permeation... 

In this work, a novel and facile synthesis process to fabricate single crystalline organometal halide perovskite nanowires has been successfully developed. Nanowires were grown in a high density ordered array from metal nanoclusters inside anodic aluminum oxide templates using a non-catalytic chemical vapor deposition method. Specifically, perovskite NWs were grown as a result of the reaction between methylammonium iodide (MAI) and the Pb/Sn (Pb or Sn) metal in anodic aluminum oxide templates under optimal conditions. The characterization results show that there is a reaction zone at the interface between the perovskite material and metal, at the bottom of the anodic aluminum oxide... 

Surface chemistry of as-received nanodiamond (ND) was first tailored by dry thermal oxidation to obtain carboxylated ND (ND-COOH) and by wet chemistry to obtain ethylenediamine-functionalized ND (ND-EDA). Then, the surface-functionalized ND particles were dispersed in polyamide 6 (PA6) using the melt-mixing method. Transmission optical and scanning electron microscopies indicated a fine dispersion at low nanodiamond concentrations, e.g. 0.25 wt%, particularly with ND-EDA. Differential scanning calorimetry revealed that ND-EDA favoured the α-phase crystal and enhanced the degree of crystallinity of PA6. Experimental data indicated that ND-EDA had considerably improved tensile properties at... 

In this study, zeolitic imidazolate framework (ZIF-8) as a metal-organic framework (MOF) and its hybrid nanocomposites based on graphene oxide (GO) and carbon nanotubes (CNTs) were synthesized by facile method at an ambient temperature. The sufficiency of GO and CNT substrates as the main components of the composites to grow nanoscale MOFs and increase dispersive forces were investigated. The characteristics of the MOF and hybrid nanocomposites were studied using FTIR, SEM, XRD, BET and TGA techniques. The prepared nanomaterials applied as adsorbents to remove malachite green (MG) as a cationic dye from colored wastewater. The removal rates of the hybrid nanocomposites were greater than that... 

Graphene nanoplatelets with different surface functional groups and polarity were prepared by Hummer's method and electrochemical exfoliation of graphite in two aqueous acids. The XRD, FTIR and sedimentation tests performed to characterize the polarity of the prepared graphenes. The highest polarity was associated with the sample prepared by Hummer's method and the sample synthesized by electrochemical exfoliation in nitric acid medium showed the moderate polarity. Meanwhile, the sample prepared in sulfuric acid medium showed the lowest polarity. Then thermoplastic polyurethane (TPU)/graphene nanocomposite films were fabricated with solvent exchange method. While the dispersion state and... 

Three versions of zirconium-based metal organic frameworks, NH2-UiO-66, GMA-UiO-66, and EDA-UiO-66, were synthesized and employed as adsorbent for CO2/CH4 separation. GMA-UiO-66 was synthesized via a ring opening reaction between the amine species in the framework and epoxy groups in glycidyl methacrylate (GMA), while the green aza-Michael addition reaction was used for the first time to functionalize GMA-UiO-66 with ethylenediamine (EDA). The products were characterized by BET, XRD, TGA, FESEM, ICP-OES, 1H NMR, mass spectroscopy, and FTIR-ATR methods to monitor their textural properties before and after functionalization. The results indicated that GMA was successfully grafted to the... 

A low cytotoxic metal–organic framework (MOF) UiO-66 (UiO stands for University of Oslo) and NH2-UiO-66, that showed high cell viability of HFF-2 via 3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyl tetrazolium assay, was reported as an effective adsorbent (antidotal) agents. The structure of MOFs was confirmed by Fourier transform infrared, Field emission scanning electron microscopy (FESEM) and X-ray diffraction. Thermal behavior of MOFs was investigated using with thermogravimetric analyzer in nitrogen atmosphere to check the thermal stability. FESEM showed NH2-UiO-66 displayed symmetrical crystals with triangular base pyramid morphology, with the particle size around 100 nm and uniform size...