فصلنامه نانو مواد
پیاپی 20 (زمستان 1393)

At the present research aluminum matrix composites reinforced with different percentages of CNT amounts (0 to 5 wt.%) were synthesized by spark plasma sintering (SPS) method that is one of the new procedure to metallic powders sintering. The microstructural properties and fracture section of samples were investigated by scanning electron microscopy (SEM). Moreover, the studies of CNT properties were done based on transmission electron microscopy (TEM) analysis. The compressive strength and micro hardness tests were carried out in order to obtain the mechanical properties. The results shows SPS is the appropriate method to composite fabricate. Furthermore, the employment of optimum amounts (about 1% or lower) of CNT as a reinforce part are led to increasing of micro hardness up to 80%, and strength up to 30%. In following, by increasing of CNT amount more than 1% the properties were dropped due to agglomeration of CNTs.

In this work carbon mesoporous nano adsorbent (CMK-3) and also silver doped mesoporous carbon nano-composite were prepared by applying a hard template of silicate precursor SBA-15 and characterized by N2 adsorption-desorption, transmission electron microscopy (TEM) andenergy dispersive X-ray analysis (EDX). These prepared materials were applied as adsorbents for Orange G dye and its removal from wastewater and their adsorption capability were compared with each other. Effects of contact time, pH, initial dye and salt concentrations on dye removal efficiency were investigated. Experimental results show that it takes an hour for both nano adsorbents to establish equilibrium with Orange G and Ag/CMK-3 nano-composite has more efficiency for Orange G adsorption than CMK-3. Furthermore, dye removal increased in high concentrations of initial dye and salt, but decreased with increasing temperature and pH.

In this paper, the cordierite-mullite bonded porous SiC nano-composites were prepared by a reaction bonding method. For this reason, nano-SiC, talc and kaolin as raw materials, using graphite as the pore-forming agents were used for the preparation of these nano composites. The effect of nano-SiC content on the properties of these nano-composites after firing at 1250 °C was investigated. Hence, the porosity and mechanical strength, thermal shock resistance, refractoriness under load, phase composition and microstructure of these nano-composites were evaluated. The results showed that nano-SiC content has a great effect on the formation of cordierite and mullite phases. The cristobalite and corundum phases can form in the composition of nano composite besides of cordierite and mullite which their contents depend on the nano-silicon carbide content. The thermal shock resistance of nano-composite improves with increasing of nano-SiC content but, the refractoriness tends to decrease. The best results were obtained with composition containing 60 wt. % nano-SiC. The microstructural investigations showed that a proper cordieritemullite bonding system is formed between nano-SiC particles.

In this research, ZnO nanostructures were synthesized via thermal decomposition by two precipitation agents, oxalic acid and ammonium hydroxide. Phase investigation, morphology and structure of nickel oxide powder obtained were evaluated by X-ray diffraction (XRD), scanningelectron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), respectively. The results of infrared spectroscopy and X-ray diffraction analysis confirm the formation of zinc oxide nanostructures by two deposited agents. According to the results the formations of single phase of the zinc oxide nanostructures occurred after heat treatment of both samples at temperature of 450 °C for 2 h. The highest degree of crystallinity occurred in the case of using the oxalic acid as deposited agent. Also the SEM results indicate that the morphology of the particles was spherical and rod in the case of using oxalic acid and ammonium hydroxide as precipitated agents.

This study examined an innovative approach for imparting multi-functional properties, i.e., selfcleaning, electrical conductivity, UV blocking as well as antimicrobial properties onto cotton fabric. Graphene oxide (GO) and commercial titanium dioxide photocatalyst (P25) were used to prepare the nanocomposite. GO/TiO2 nanocomposites were successfully prepared, by a simple method of mixing and sonication, and used for multi-functional treatment of cotton fabrics. The role of both titanium dioxide and GO concentrations on the various properties of the fabric was investigated. The morphologies of GO and GO/TiO2 nanocomposite were investigated by TEM. Furthermore, the structure and morphology of fabric surface has been examined by field emission SEM and its chemical structure has been elucidated by XPS. Microscopic analyses of the nanocomposite revealed that TiO2 particles with average particle size of ∼21 nm are attached to the surface of GO. The treated cotton fabrics with GO/TiO2 nanocomposite showed excellent photocatalytic self-cleaning activity measured by degradation of methylene blue in aqueous solution under sunlight irradiation. The antimicrobial activity of finished fabrics was assessed through the calculation of bacterial reduction against E. coli and S. aureus bacteria, which suggested that the GO/TiO2 nanocomposite can function effectively as antimicrobial agents. Results showed that the electrical conductivity of the graphene oxide/titanium dioxide nanocomposite-coated fabrics was improved significantly after sunlight irradiation, which demonstrated the photocatalytic reduction of GO sheets by titanium dioxide. Moreover, the nanocomposite finished cotton fabric demonstrated proper UV blocking activity.

In this survey, the effect of silica and titanium dioxide nanoparticles, methods of production and processing temperature on the hydrophobicity properties of concrete have been studied and optimal conditions were introduced nanoparticles in the casting solution concentration and dryingtemperature are two factors affecting the final properties and performance coatingssuper-hydrophobic described in the present work has been reviewed in detail. The results indicate that the higher the contact angle, the more hydrophobic surface will be if this value reaches 150 to 180 degrees so that the super-hydrophobic surface of the cloud will be at an angle of 90to 120 degrees will surface hydrophobicity. To study the properties of hydrophobicity, super hydrophobic coating and the hydrophobicity of silica nanoparticles and titanium dioxide nanoparticles. The concrete was prepared and its properties were analyzed. So that the concentration of nanoparticles in the coating plays an important role in hydrophobicity and super-hydrophobic due to the nature of the hydrophilic nanoparticles of titanium dioxide concentration in the coating exceeds hydrophobicity of silica nanoparticles improved the coating decreases their hydrophobicity. In order to determine the hydrophobicity of the coating through testing the contact angle (CA), the surface morphology caused by the scanning electron microscope (SEM) were studied.

Vanadium oxide nanotubes were synthesized using V2O5 powder as the precursor and hexadecylamine as the structure-directing template using a gel (V2O5.nH2O) reaction method followed by a one-step hydrothermal treatment (150-180 °C, 2–7 days). The effect of ultrasonics on the formation of nanotubes is reported. The structure and morphology of the nanotubes were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The inner and outer diameters of the nanotubes varied from 30 to 40 nm and 50 to 130 nm, respectively. The nanotubes measured several micrometers in length.

This paper deals with the preparation of porous calcium phosphate cements based on the using of CO2 bubbles solved (super-saturated) in the liquid phase of cement. Powder phase of the cement consists of 90% α-tricalcium phosphate and 10% hydroxyapatite and the liquid phase was a 4% Na2HPO4 solution containing 25% of gaseous water. To produce macroporous cement, powder and liquid phases of cement were mixed together and mechanical stresses induced by mixing procedure caused CO2 bubbles to leave the mixture and form macropores. The initial setting time of porous cement was about 16 minutes. The as-set porous cement had a compressive strength value of 3 MPa that reached to 17.5 MPa after immersion in simulated body fluid solution for 14 days. The SEM results showed that the cement structure contained macropores with an approximate size of 70 μm. About 3.1% macroporosity was produced in the cement using this method meanwhile total calculated porosity was about 47%. Nanocrystals of apatite phase and alpha-tricalcium phosphate reactant determined by XRD technique were also observed in SEM images of samples soaked in simulated body fluid solution. FTIR spectrometry results proved that the formed apatite phase is carbonated. Carbonated apatite nanocrystals are resorbed fastly and replaced by the natural bone.