Papers by Keyword: Chemical Synthesis

Abstract: Nanostructured ZnO films are obtained by chemical bath deposition from zinc nitrate, hexamethylenetetramine and ammonia. The evolution of the structural and sub-structural properties of the films is characterized using high resolution scanning electron microscopy (SEM) and X-ray diffraction analysis. In particular, we detail here the influence of condensation time on the crystal phase, texture quality, lattice constants, grain size, coherent scattering domain size (CSD), microstrain, stress and concentration of dislocations. Obtained condensates have the wurtzite structure with lattice parameters in the range a = 0.3248-0.3254 nm and c = 0.5206-0.5214 nm, depending on the condensation time. The grain size and microstrain in the direction perpendicular to the crystallographic planes (002) are in the range L ~ 26-42 nm and ε ~ (0.59-3.09)·10^-3, respectively. Furthermore, the effects of deposition time on microstrain, stress and concentration of dislocations in the layers is established. By adjusting the condensation time, we are able to produce ZnO films with controlled structural properties: from nanorods to continuous nanostructured films.

Abstract: One dimensional rutile-TiO₂ nanoneedles (NNs) and nanorods (NRs) were grown directly on transparent conductive Fluorine-doped SnO₂-coated (FTO) glass substrates using Chemical Bath Deposition (CBD) method. Titanium (III) chloride was used as the precursor, followed by annealing at 200°C. The heat treatment leads to the conversion of TiO₂ nanoneedles into nanorods. Optical studies revealed that rutile-TiO₂ thin films have a high absorption coefficient and a direct bandgap which decreased slightly (3.14-3.09 eV) by applying heat treatment .The ease of deposition of rutile-TiO₂ nanocomposite with different morphologies at low temperature provides a new insight for potential applications in solar cells, sensors, catalysis and separation technology.

Abstract: Tricalcium aluminate (C₃A) are used for different applications such as thermal insulation, cement, refractory concrete as binders or binders. The aim of this work is to study the synthesis and sintering behaviour of C₃A samples. The chemical synthesis was performed by means of polymeric precursor method from metalic nitrates dissolved in ethylene glycol and citric acid forming a polymeric resin. The evolution of the crystalline phases was accomplished by X ray Diffraction (XRD). Thermogravimetric (TG), Differential Thermal Analysis (DTG) and Thermal Expansion were performed in order to verify the thermal properties of the material. From the characterizations carried out it may be concluded that the synthesis of polymeric precursors via allowed obtaining pure phase of C₃A at 1000°C low temperatures. The temperature of 1350°C it possible to obtain materials having grain morphology with uniform size and densely packed.

Abstract: We report a facile synthesis of PtNi nanosheets on the flexible ITO/PET substrate by electrochemical deposition method. The morphology and composition of the PtNi nanosheets were characterized and it was revealed that the PtNi nanosheets were polycrystalline with a thickness of about 4 nm. The average Ni content in the nanosheets was about 10 at%. The results of the electrochemical measurements showed that the PtNi nanosheets have excellent catalytic activity and stability toward the electro-oxidation of methanol in alkaline medium, which making it more attractive for fuel cell applications.

Abstract: Novel ordered three-dimensional (3D) firtree-like hexagonal cobalt microcrystals with hierarchical dendritic superstructures have been obtained by using cobalt bis (4-pyridine carboxylate) tetrahydrate as the precursor of Co. The 3D dendrite has a main axis and the leaves arrange layer by layer in parallel along the axis, which exhibit the radiate hexagonal arrangement from the axis in a layer. The main axis of the dendrite grows along the [001] direction of hexagonal Co and the leaves grow parallel to the (001) plane. The hysteresis loop of the sample shows a ferromagnetic behavior with the saturation magnetization of 134.0 emu/g and the coercivity of 184.9 Oe. It is noted that the coercivity is relatively low compared with that of the cobalt dendritic crystallites reported previously, which may result from the lower total morphology anisotropy of our sample.

Abstract: A new kind of surface-functionalized magnetic nanoparticles was fabricated by surface modification of ferroferric oxide with monolayer-protected gold nanoparticles. Ferroferric oxide nanoparticles were firstly synthesized by co-precipitating Fe²⁺ and Fe³⁺ ions in base solution, and then coated with a layer of 3-aminopropyltriethoxysilane by silanization reaction. Gold nanoparticles were surface-attached with 2-mercapto-4-methyl-5-thiazoleacetic acid which were subsequently linked to the modified ferroferric oxide nanoparticles to produce Au/Fe₃O₄ composite materials. The outer layer of ligand (2-mercapto-4-methyl-5-thiazoleacetic acid) on Au/Fe₃O₄ can function as binding sites for drugs and biomolecules, whereas the innermost magnetic cores are able to respond to an externally applied magnetic field. The as-synthesized Au/Fe₃O₄ nanocomposite is superparamagnetic (31.4 emu/g), thus rendering it potentially applicable in magnetic drug delivery and bioseparation.

Abstract: During the synthesis of γ-Fe₂O₃ nanoparticles using a chemically-induced transition in a FeCl₂ solution, Co-surface modification was attempted by adding Co (NO₃)₂ and NaOH to the solution. The magnetization behaviors, morphologies, crystal structure, and chemical compositions of the as-prepared samples were characterized using vibrating sample magnetometry, transmission electron microscopy, X-ray diffractometry, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The as-prepared particles consisted of γ-Fe₂O₃/CoFe₂O₄ composite crystallite and a CoCl₂·6H₂O coating. The molar, mass and volume ratios of the phases were estimated from the characterization results for each sample. The Co-modified γ-Fe₂O₃ nanoparticles’ anisotropic constant is approximately 1.48×10^-1 J/cm³. Their coercivity depends on the size of composite crystallites, which is based on the γ-Fe₂O₃/CoFe₂O₄ content rather than the Co content.

Abstract: Electron trapping materials SrSO₄:Eu²⁺ were prepared by hydrothermal method from fatty alcohol polyoxyethylene (3) ether (AEO-3) aqueous solution at 200 °C for 20 h. The phase structure, microstructure and optical properties were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM) and excitation-emission spectroscopy (PL-PLE), respectively.

Abstract: TiO₂ nanorod array films with or without Nb doping grown directly on transparent conductive glass (FTO) were prepared by a facile hydrothermal method. The films were characterized by means of field emission scanning electron microscopy (FE-SEM) with energy-dispersive x-ray spectra (EDS), X-ray diffraction (XRD) and the X-ray photoelectron spectroscoy (XPS). The electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and transient photocurrent were investigated in a three-electrode system with TiO₂ nanorod array film served as the photoanode. The photoelectrocatalytic activity of the films was evaluated by the oxidation of glucose under UV irradiation. The results show that both the pure and Nb-doped TiO₂ nanorods perpendicularly grown on FTO substrate are rutile phase. The resistance of the TiO₂ nanorod array photoanode is decreased significantly by Nb doping. The steady-state photocurrent (i_ss) for glucose oxidation at Nb-doped TiO₂ nanorod array film is much higher than that at the pure one. The enhanced photoelectrocatalytic activity of the Nb-doped TiO₂ nanorods could be attributed to the enhanced charge transport ability.

Abstract: Eu, Sb doped SnO₂ and quartz compound conductive powders are prepared by the coprecipitation method with SnCl₄·5H₂O, SbCl_3, Eu₂O₃ and quartz powders as the raw materials. The crystal phase and structure of the prepared conductive particles are characterized by FTIR and XRD techniques respectively. The resistivity of the prepared conductive powders are measured with four-point measurement method. The resistivity of Eu, Sb doped SnO₂ and quartz compound condu-ctive powders is 0.37 Ωcm. FTIR spectrum of Eu, Sb doped SnO₂ and quartz compound conductive powders shows that there are the vibration peaks in 546.14 cm^-1, 489.95 cm^-1, 466.71 cm^-1, 430.34 cm^-1 and 418.92 cm^-1 respectively, and have intense absorption in 4000 cm^-1 ~ 1100 cm^-1. Eu, Sb doped SnO₂ conductive powders have a structure of tetragonal rutile. The complex doping is achieved well by coprecipitation method and is recognized as replacement doping or caulking doping. The composition of compound conductive powders are Eu, Sb doped SnO₂ conductive powders and quartz powders.