سال:1393 | دوره: | شماره: |تعداد مقالات:14

Scanning Near-Field Optical Microscopy (SNOM) is a member of scanning probe microscopes (SPMs) family which enables nanostructure investigation of the surfaces on a wide range of materials. In fact, SNOM combines the SPM technology to the optical microscopy and in this way provide a powerful tool to study nano-structures with very high spatial resolution. In this paper, a qualified overview of diverse SNOM methods mostly based on aperture and aperture-less is presented.

Nanofluids are gaining much importance over the past decade due to their enhanced thermal conductivity, specific heat, cooling capacity, electrical conductivities. Novel properties of nanofluids are yet to be explored to the highest potential applications. One of the prominent applications of nanofluids is in thermal conduction. The presence of nanoparticle in a fluid can enhance the thermal conductivities by several orders of magnitude (100-250). Experimental techniques involved in measuring thermal conductivity are transient hot wire method, steady state technique, and temperature oscillation technique, but suffer from drawbacks arising during measurement. Theoretical models are also proposed by Maxwell, Hamilton Crosser, Yu and Choi, Koo and Kleinstreuer, and Kumar. The present paper deals with identification of the best combination of nanoparticle and fluid by making use of existing models.

A new anti-corrosion compound, Melamine Formaldehyde (MF), was formulated by the addition of proper amount of formaldehyde to melamine under specific conditions. This compound was mixed with a novel nano powder, which was extracted from corn cob ash containing SiO2 particles, in order to improve its corrosion inhibition efficiency. This inhibitor provides a high level of protection for steel subjected to saline environments. The synthesized inhibitor works immediately with forming a dense protective layer and after adding the nano powder, its inhibition efficiency is improved. The electrochemical standard corrosion tests and the surface examination, using Scanning Electron Microscope (SEM) of steel specimen immersed in 3.5%Wt NaCl solutions with and without any inhibitor at room temperature, were carried out to investigate the inhibition behavior of the synthesized inhibitor. All of the results, which include the corrosion and electrochemical testing data, show that the tested corrosion inhibitor is generally effective and its efficiency gets better by adding the ceramic powder.

In the present work the effect of Cu-Water nanofluid, as heat transfer fluid, on the performance of a parabolic solar collector was studied numerically. The temperature field, thermal efficiency, mean-outlet temperatures have been evaluated and compared for the conventional parabolic collectors and nanofluid based collectors. Further, the effect of various parameters such as fluid velocity, volume fraction of nanoparticles, concentration ratio and receiver length has been investigated. The results show that, by increasing the volume fraction of nanoparticles, the performance of the solar parabolic collector enhances.

Cyanide is one of the major Environmental pollutants in industrial wastewater. Entrance of it to existence environmental contains very health hazardous. The cyanide can be removed from aqueous solutions in many ways, but most of these methods are expensive. In the present study, novel magnetic nanoparticle modified with a polydentate ligand is used to remove cyanide. The procedure is efficient and cost-effective. In this study, novel magnetic nanoparticle (Fe3O4-SiO2 -Met) is used to remove cyanide. Various parameters affecting the removal rate such as pH (9-11), the amount of absorbent (0.01, 0.03, 0.05gr) and contact time (4-12 hr) were evaluated. Data from the experiment were analyzed with a mathematical model of the smallest sum of squares. The relationship between time and pH value on the removal of cyanide are linear. Nevertheless, the amount of the adsorbent and time are effective. Absorbent weight is increased from 0.01 to 0.05 g and removal efficiency reaches from 20% to 60%. With increasing contact time from 4 to 12 hours removal efficiency reaches from 30% to 55%. The finding of this research is introducing modified nanoparticles Fe3O4-SiO2 -Met as an adsorbent for removing cyanide.

The performances of two-phase polymer-liquid PEBAXÒ/polyethylene glycol (PEG) and three-phase polymer-liquid-solid PEBAXÒ/PEG/MWNT thin film composite membranes for CO2 and CH4 permeation were studied. The effect of temperature and MWNT/PEBAXÒ ratio on single gas (CO2 and CH4) permeability was investigated. The permeation of both gases was measured at different temperatures from 303 to 323oK. The results exhibited that the PEBAXÒ/PEG/MWNT membrane had better permeability for CO2 in comparison to the PEBAXÒ/PEG membrane, whereas CO2/CH4 selectivities in both membranes were almost the same; i.e. MWNT filler promoted the performance of PEBAXÒ/PEG membrane in CO2/CH4 Separation. Also, the permeability increases with temperature in all experiments. For the three-phase PEBAXÒ/PEG/MWNT membrane, CO2 permeability was determined 221 Barrer in 323oK and the selectivity was obtained as 23 in 303oK.

Conducting polymers, because of their special properties, are used to introduce conductive polymeric composites. Also, clays have recently been used for preparation of polymer composites with enhanced mechanical and thermal properties. The aim of this work is to study the synergetic effect of the co-presence of conducting polyaniline and montmorillonite in the polyethylene matrix. Polyethylene /montmorillonite /polyaniline nanocomposite was prepared by in-situ polymerization of polyaniline in the presence of PE and MMT. All nanocomposites contain 5wt% of OMMT and different amounts of conducting PANI vary 5, 10, 15 and 20wt%. Electrical conductivity was measured and characterized by FTIR, DSC, SEM, XRD and DMA.The thermal behavior of PANI chains in the nanocomposites was investigated by DSC and it was observed that OMMT causes a remarkable increase in thermal stability and it improved mechanical properties. SEM and XRD patterns clearly showed dispersal of PANI and exfoliation/intercalated in the polymer matrix.

Mirage effect is contactless and non destructive method which has been used a lot to determine thermal properties of different kind of samples, transverse photothermal deflection PTD in skimming configuration with ccd camera and special programs is used to determine thermal conductivity of porous silicon ps film. Ps samples were prepared by electrochemical etching. Thermal conductivity with porosity changing was measured and the experiments result compared with theoretical results, and they were almost the same.

Polymer-clay nano-composite materials, in which nano-meter thick layers of clay dispersed in polymer matrix, have generally higher mechanical properties than normal polymeric materials. A new three-dimensional unit cell model has been developed for modeling three constituent phases including inclusion, interphase and matrix. The total elastic modulus of nano-composite is evaluated. Numerical results are in good agreement with the previous proposed theoretical modeling. Higher matrix and inclusion elastic modulus both can dramatically increase the total elastic modulus.

In this work, we report synthesis of surface modified superparamagnetic iron oxide nanoparticles (SPION) by co-precipitation method using FeSO4.7H2O and Fe2 (SO4) 3.5H2O as precursors and trisodium citrate dihydrate as surfactant. Surface modification of the as prepared samples was performed in pot by sol-gel precipitation method using tetraethoxysilane (TEOS). The structure, morphology, and magnetic properties of the products were characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and Vibrating sample magnetometer (VSM) at room temperature. The results revealed formation of iron oxide nanoparticles, with an average size parameter of 8.5 nm for naked and 37nm for silica coated particles, with a superparamagnetic behavior and fast response to applied magnetic fields with zero remanence and coercivity.

A novel nano-sized manganese (II) coordination polymer, [ {Mn (NCS) 2 (L) (H2O) 2} (L)] n, (1) (L-=4, 4' -Bipyridine), have been synthesized by a sonochemical process and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), IR spectroscopy and elemental analysis. Direct calcination of the single crystals and nano-sized compound 1 at 400oC under air atmosphere yields mixture of K2Mn2 (SO4) 3, MnOS and Mn3O4 nanoparticles. Results show that the size and morphology of the K2Mn2 (SO4) 3, MnOS, Mn3O4 nanoparticles depend on the particles size of compound 1. Decrease in the particles size of compound 1 leads to decrease in the particles size of the K2Mn2 (SO4) 3, MnOS and Mn3O4.

In this work, sol-gel processing was used to synthesize the fluorohydroxyapatite (nano-FHA, Ca10 (PO4) 6 (OH) 2-xFx) nanopowders. The advantages of the sol-gel method over other methods are precise control of composition, low processing temperature, and better homogeneity. Calcium nitrate tetrahydrate, phosphorous pentoxide and Tetrabuthylammonium fluoride were used, respectively, as P, Ca, and F precursors with a Ca: P ratio of 1.67. The FHA powders were calcined at temperatures of 600oC. The characterization and structural features of the synthesized powders were evaluated using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) spectra and scanning electron microscopy (SEM) techniques. The thermal stability of FHA powders was studied through diffraction thermal analysis (DTA) and the optimized calcination temperature was found 600oC, we used thermal gravimetric analysis (TGA) experiment in three heating rate 7, 10, 15 (oC) on minute. The in vitro behavior of powder was investigated with mouse fibroblast cells.

Iron oxide nanoparticles were synthesized by coprecipitation method using ammonia as precipitation agent. Most researchers usually add ammonia into the iron salt solution but in this work the salt solution drop wise has been added to the ammonia and the new obtained results were compared with those of other researches. Magnetic properties of nanoparticles were measured by VSM. The effect of reaction temperature and concentration of reactants on the size and magnetic properties of nanoparticles were investigated. The size of particles was calculated by Sherrer formula and magnetic data, and then compared with the size of nanoparticles obtained by TEM. The size of produced nanoparticles ranged from 8 to 17 nanometer and their saturation magnetizations were between 65.5 to 72.5 emu/gr. It was found that increasing reaction temperature increases saturation magnetization of nanoparticles, but variation of concentration of ammonia did not change the saturation magnetization. Saturation magnetization observed here were more than the values reported by others.

Ag/TiO2 photocatalytic nanoparticles by two methods, the sol-gel using a reducing agent and spattering was produced. Crystalline phase of Titanium dioxide was investigated in both. Ag/Tio2 peak in the sol-gel method at temperatures of 300, 500 and 600oc were studied. Ag/TiO2 peak at different temperatures were determined using the spattering. XRD patterns of calcined this is TiO2 and Ag/ TiO2.