Journal of Nano Structures
Volume:5 Issue: 3, Summer 2015

New selective coating materials are developed and used in advanced solar collector and absorber designs with improved efficiency. Cobalt and Copper sulfides nanoparticles are high interest for absorbers of solar thermal collectors due to their optical properties and high absorptance in the solar wavelength range (> 96%). In the present work, Cobalt and Copper sulfides nanoparticles were synthesized successfully via a surfactant-assisted solvothermal process. The structural, morphological and optical characteristics of as-synthesized materials were investigated by X-ray diffraction, field emission scanning electron microscopy and diffuse reflectance spectroscopy. Evaluation of the obtained results indicated that the as-synthesized nanoparticles had well-defined morphology with very fine particles and higher light absorption in UV/vis region not only than the common inorganic pigments but also than common carbon black. Copper sulfide exhibited integral solar absorptance value equal to 0.97 that is very ideal for solar thermal collectors and thermal selective coatings. They also had low thermal emittances equal to 0.14 and 0.27 for cobalt and copper sulfides respectively.

Classical xerogels are robust, inexpensive and nontoxic materials with low-ordered nanoporous structures. In water streams where the pH is higher than the Point of Zero Charge, the surface of classical xerogels such as tetraethoxy orthosilan (TEOS) xerogel is negatively charged. It was assumed that a xerogel can work as a strong adsorbent for metal ions without further modification. Therefore, the capability of TEOS xerogel for adsorption of two heavy metal ions, Pb2+ and Cd2+, from aqueous solution was studied. The batch experiments revealed that the adsorbent has higher adsorption capacity for Pb2+ (58.82 mg/g) and Cd2+ (35.71 mg/g) as compared with the reported low-cost adsorbents. Kinetics and thermodynamic studies were employed to explain the adsorption mechanism. It was concluded that the adsorption of both ions on TEOS xerogel obey chemisorption mechanism. However, the reaction of Pb2+ with the adsorbent is thermodynamic controlled and the one of Cd2+ is kinetic controlled.

In this work firstly ZnO nanoparticles were synthesized via a simple precipitation method. At the second step titanium dioxide and silicon dioxide shell were synthesized on the core. For preparation ZnO-TiO2-SiO2 the sol product was calcinated at 500 ºC for 2h. Properties of the product were examined by X-ray diffraction pattern (XRD), scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy. The photo- catalytic behavior of ZnO-SiO2-TiO2 nanocomposite was evaluated using the degradation of a methylene blue aqueous solution under visible light irradiation. The results show that ZnO-SiO2-TiO2 nanocomposites have applicable photo-catalytic performance.

In the present study, nanocrystalline Ni50Al50-xMox (X = 0, 0.5, 1, 2.5, 5) intermetallic compound was produced through mechanical alloying of nickel, aluminum, and molybdenum powders. AlNi compounds with good and attractive properties such as high melting point, high strength to weight ratio and high corrosion resistance especially at high temperatures have attracted the attention of many researchers. Powders produced from milling were analyzed using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The results showed that intermetallic compound of NiAl formed at different stage of milling operation. It was concluded that at first disordered solid solution of (Ni,Al) was formed then it converted into ordered intermetallic compound of NiAl. With increasing the atomic percent of molybdenum, average grain size decreased from 3 to 0.5 μm. Parameter lattice and lattice strain increased with increasing the atomic percent of molybdenum, while the crystal structure became finer up to 10 nm. Also, maximum microhardness was obtained for NiAl49Mo1 alloy.

In this paper, the effect of the Brownian term in natural convection of CuO-Water nanofluid inside a partially filled porous cavity, with internal heat generation has been studied. It is assumed that the viscosity and thermal conductivity of nanofluid consists of a static part and a Brownian part of which is a function of temperature and the volume fraction of nanofluid. Because of internal heat generation, the two-equation model is used to separately account for the local solid matrix and nanofluid temperatures. To study the effect of Brownian term various parameters such as the Rayleigh number, volume fraction of nanofluid, porosity of the porous matrix, and conductivity ratio of porous media is examined and the flow and heat fields are compared to the results of non-Brownian solution. The results show that Brownian term reduces nanofluid velocity and make smoother streamlines and increasing the thermal conductivity leads to cooling of porous material and achieving more Nusselt. Also the greatest impact of Brownian term is in low-porosity, low Rayleigh or small thermal conductivity of the porous matrix. In addition, mounting the porous material increases the Brownian effect and heat transfer performance of nanofluid but increasing porosity up to 0.8 reduces this effect.

Electrochemical properties of various rock-shaped-CuO/graphite (G) composites and monoclinic structure CuO nanoparticles as the cathode versus a zinc plate as the anode in a 4M NaOH electrolyte were elucidated by electrochemical impedance spectroscopy (EIS) and chronopotentiometry (CP) in a two electrode configuration cell. Various values of G 9, 16 and 28 wt% were prepared and studied as cathode materials for an alkaline Zn-CuO Battery. The EIS results demonstrated that increasing the mass ratio of G caused significant decrease in charge transfer resistance (Rct) and capacitive behavior of the electrode. Also, the discharging voltage of the cells was increased due to raising the mass ratio of the graphite. Besides, electrochemical properties of the monoclinic structure CuO nanoparticles as cathode material in the alkaline battery was compared with a rock shaped CuO particles. The results showed that the discharged voltage of monoclinic CuO nanoparticles is less than another rock shaped CuO nanoparticles form.

CoFeCu nanowires were deposited by pulsed electrodeposition technique into the porous alumina templates by a two-step mild anodization technique, using the single-bath method. The electrodeposition was performed in a constant electrolyte while Cu constant was controlled by electrodeposition current. The electrodeposition current was 3.5, 4.25, 5 and 6 mA. The effect of electrodeposition current and annealing on the magnetic behavior of the nanowires was investigated. Nanowires were fabricated with 30nm diameter and 100nm inter-pore distance with both bcc-CoFe and fcc- Cu phases. With increasing the electrodeposition current the Cu content decrease and the coercivity and magnetization increase up to its optimum value, then decrease. Annealing improved the coercivity, maximum coercivity was obtained for sample fabricated at 5 mA current. After annealing the magnetization decrease for all sampls. The X-ray diffraction pattern of the sample at electrodeposition current 3.5 mA after annealed indicates that Cu and CoFe phases separately was formed and separate peak related to CoFeCu alloy structure is not seen.

Various morphologies of silica nanoparticles were synthesized by a microwave-assisted Pechini method. Silica nanostructures were synthesized via a fast reaction between tetra ethyl ortho silicate and ammonia at presence citric acid and other effective agents in Pechini procedure. Then for preparation of polymer-matrix nanocomposites, SiO2 nanoparticles were added to poly carbonate (PC) and poly styrene (PS) matrices. Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR). The influence of SiO2 nanostructures on the flame retardancy of the polymeric matrix was studied using UL- 94 analysis. Our results show that the SiO2 nanostructure can enhance the flame retardant property of the poly carbonate matrix. PC shows better flame retardancy compare to poly styrene.

Palladium is the best metal catalyst for Suzuki cross coupling reaction for synthesize of unsymmetrical biaryl compounds. But its high cost limits its application in wide scale. Using of nanoscale particles as active catalytic cites is a good approach for reducing needed noble metal. By loading precious nanoparticles on magnetic nanocores as a support, recycling and reusing of catalyst will be possible. Magnetic nanoparticles have super paramagnetic feature and applying an external magnetic field can collect the supported catalyst from reaction milieu simply. In this work new palladium catalyst immobilized on modified magnetic nanoparticles containing NNO donor atoms were synthesized. Then the catalyst characterized by FT-IR spectroscopy, thermogravimetric analysis, X-ray diffraction and ICP. Prepared catalyst showed high activity in the Suzuki– Miyaura cross-coupling reaction of phenylboronic acid with aryl halides. Activity, Pd loading, reusability and Pd leaching of catalyst were studied. Results showed that the supported catalyst has the advantage to be completely recoverable with the simple application of an external magnetic field.

Ni-Co/Cu multilayers have been grown by electrodeposition method from a single electrolyte (based on Ni(SO4).6H2O, Co(SO4).7H2O, Cu(SO4) and H3BO3) using galvanostatic control on titanium sublayers. The X-ray diffraction (XRD) patterns confirmed the mult ilayer ed structure with the nanometer thicknesses. Also, electron diffraction x-ray (EDX) analysis confirmed the purity of deposited samples. The morphology of the samples was estimated by scanning electron microscope (SEM). Magnetoresistance (MR) measurements were carried out at room temperature for the Ni-Co/Cu multilayers by measuring the resistivity in a magnetic fields varying between ±6kOe as a function of the Ni-Co and Cu layer thicknesses; (1  dCu(nm)  4 and 3  dNi - Cu (nm)  5). The Maximum va lu e of giant magnetoresistance (GMR) was obtained when the Ni-Co and Cu thicknesses were 4.0nm and 4.0nm respectively. The hysteresis loop of the samples at room temperature was studied using an alternating gradient force magnetometer (AGFM). Finally, the temperature dependence of magnet izat ion for Ni-Co/Cu multilayers; (dNi-Cu(4nm)/dCu(2nm) and dNi-Cu(3nm)/dCu(3nm)) measured by Faraday balance and decreasing the magnetization with increasing the temperature discussed according to electron scattering due to spin fluctuation.

In this work firstly MgFe2O4 nanoparticles were synthesized via a microwave-assisted method. The product was calcinated at 900 ºC for 2h. At the second step zinc oxide shell was synthesized on the ferrite under ultrasonic waves. Properties of the product were examined by X-ray diffraction pattern (XRD), scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Vibrating sample magnetometer (VSM) shows nanoparticles exhibit ferromagnetic behavior. The photo-catalytic behavior of MgFe2O4-ZnO nanocomposite was evaluated using the degradation of organic dyes aqueous solution under ultraviolet (UV) light irradiation. The results show that MgFe2O4-ZnO nanocomposites have applicable magnetic and photo-catalytic performance.

Cu2O nanoparticles were synthesized by thermal treatment in liquid paraffin without any inert gas protection using nano structures of Schiff base copper (II) complex (1) as precursor. Liquid paraffin was used as solvent and reductant. Span 80 was applied to control the morphology of cuprous oxide nanoparticles. The nano structure of the complex was characterized by X-ray diffraction measurements, UV–visible spectroscopy and Fourier transforms infrared spectroscopy. Thermal stability of Cu complex in its nano size form has also been studied by thermal gravimetric and differential scanning calorimetry analysis. The obtained cuprous oxide nanoparticle has been characterized by XRD measurements and FT- IR spectroscopy. The morphology, structure and size of the nano structure of 1 and Cu2O are investigated by scanning electron microscopy. The resulted cuprous oxide nanoparticles with average diameter about 30-40 nm were obtained and they have uniform morphology and stable when exposed to air.