JOURNAL OF ADVANCED MATERIALS AND TECHNOLOGIES
Year:2014 | Volume:3 | Issue:2|Papers Count:10

In the present research work, in order to optimize the fabrication of CdS optical films, the effect of bath temperature on structural properties of CdS thin layers produced by chemical bath deposition method in the range of 60-750oC was investigated, CdCl2, NH4OH, and thiourea were used as the reactants at constant pH and deposition time. The results showed that by increasing of temperature from 60oC to 75oC, the structures of the films change from amorphous to nano crystalline. The thin layer produced at 75oC temperature showed superior optical properties as regards to the optical characteristics like transmittance and energy band gap values.

In this research, Barium titanate thick film was produced by thermal spray method on stainless steel substrate. Morphology and structure properties of BaTiO3coatings prepared by atmospheric plasma spraying were evaluated using scanning electron microscope (SEM) and X-Ray diffraction (XRD) techniques, respectively. According to the results, parameter optimization has been shown to play a critical role in the deposition of these materials as thin structurally homogeneous deposits. Based on XRD results, the sprayed films were predominantly polycrystalline but contained an amorphous second phase. The crystalline/amorphous ratio is directly related to the dielectric properties of the layer, with greater crystallinity giving higher values of dielectric constant. Microcracks and splat/splat interfaces are also believed to adversely affect the dielectric properties. The maximum dielectric constant (k) values achieved using the APS method for deposition is in the range of 70–115. Dielectric constant values changed to 160-180 after heat treatment.

The aim of this study is synthesis of 7 % yttrium-doped strontium titanat (Sr0.895Y0.07TiO3±d) as a new anodic material for solid oxide fuel cell. The nanoparticles with nonstoichiometric composition of Sr0.895Y0.07TiO3±d were synthesized by sol- gel method. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) techniques were used for characterization of phase composition, microstructure and particle size. Moreover, thermal analysis (TG-DTA) was used for determining proper temperature range of calcination.The Debye-Scherer and modified Scherer equations were employed to calculate the crystallite size of Y-SrTiO3. XRD results confirmed that crystalline SrTiO3 and Y-doped SrTiO3 compounds were formed with crystallite size of 25±4 nm. The lattice parameter of SrTiO3 was reduced by introducing yttrium into its structure. SEM micrographs showed cubic morphology for Y-doped SrTiO3 compound. The sol- gel method is capable for synthesis of Y-doped SrTiO3 with desired composition and microstructure and can be used for anode material of solid oxide fuel cells.

Boron carbide - silicon carbide composite was produced by mechanically activated combustion synthesis (MASHS) method, in this study. Initially, raw materials powders containing B2O3, Si, C and Mg were weighed and were milled under Ar atmosphere by a planetary mill. For prepare pellets, the milled powders were pressed by uniaxial cold press and synthesis was occurred in atmosphere controlled tubal furnace. In the various steps, XRD analysis was taken to check the phases. XRD analysis used to calculate the average crystalline size and SEM and TEM analysis were taken to morphology studying. Resulting product is contains MgO, B4C and SiC. Also in the XRD analysis little chance existence of Mg2SiO4 or borate compounds of magnesium and remaining boron, carbon and silicon are outstanding. In order to remove or reduce undesired phases, acid leaching by hydrochloric and mechanical activation with different energies were performed. The study of X-ray diffraction analysis after acid leaching showed great influence of acid leaching by HCl to remove impurities. It was also seen that remaining substances significantly reduced by activation energy increases. Average crystalline sizes of optimal sample were calculated by Scherrer equation by 11.09 for B4C and 12.66 for SiC. The SEM and TEM analysis confirmed synthesis of nano scale boron carbide - silicon carbide composite in nano scale. Grain size of about 30 nm was observed by TEM.

Copper is widely used in different industries due to its good thermal and electrical conductivity. However, it can be in contact with fluid environments in these applications and thus, its corrosion properties are also important. In this study, copper/silicon carbide nano-composite coatings were deposited on copper substrates from sulfate bath by pulsed current and different current densities. The effects of copper surface preparation and current density on grain size, morphology, hardness, porosity, and corrosion properties of the coatings were investigated. Results revealed that, surface preparation before electrode position leaded to more uniform and less defective coatings. Grain size and porosity percent were decreased by increasing of current density. However, incorporation of nano-particles was also decreased by increasing of current density. Therefore, the optimum peak current density was achieved at 12A.dm-2at whichthe highest micro-hardness and the lowest corrosion rate of the coatingsrespectively193 Hv and 0.008mA/cm2 obtained.

In this study, The materials used in the stucoo ornaments of "Shah-shahan "house has been Discussed. "Shah-shahan" house, in "Ibn-e-Sina" street, Located in Esfahan and is one of the most valuable monuments of the "Qajar" period. After the introduction of stucco decorations, materials used in the ornamnts has been identified. This has been performed using instrumental methods and wet Chemistry. Underneath Layers Respectively were: Thatch primer and two layers of plaster and soil that stucco decoration has been performance on this layer. These layers has been recognized Using wet Chemistry. Instrumental analysis SEM-EDX proved existence of calcium, sulfur, magnesium, aluminum, oxygen and iron. XRD analysis Showed the presence of dominant phase gypsum. This show Production was performed well. Scanning electron microscope images showed needle Crystals of gypsum Side long short crystals of "Gach-e-koshte" (in persian) or massaged plaster. In this way it was found that "Gach-e-nim-koshte" has been used in these ornaments.

The influence of mechanical activation by ball milling (BM) of Ti, B and graphite powders mixture on the synthesis of B4C-TiB2 (1: 1 mole ratio) composite by Spark Plasma Sintering (SPS) is investigated. The milled powders at 0, 3 and 8 h were chosen for investigation of synthesis mechanism, density and microstructure of powder and dense products. Results showed the milling influence on temperature and time of reactants conversion to products, but it does not have any effect on mechanism of synthesis. The synthesis process occurs through a solid-state diffusion mechanism where the first crystalline phase formed is TiB, which is gradually converted to TiB2, while the formation of B4C takes place subsequently. Investigation showed that with using 8 h milled reactant; nanostructure composite powder could be obtained. As a consequence of the mechanical treatment up to 8h, SPS product density increases from about 82% to 94% of the theoretical value. Correspondingly, a material with homogeneous phase distribution and grain submicron size is obtained.

The one-step synthesis of TiO2/C microspheres via solvo-thermal method were reported using titanium tetrachloride and glucose as the precursors of titanium dioxide and carbon respectively in ethanol as solvent. The morphology and the size of microspheres affected from the time and TiCl4 salt concentration parameters were studied and the optimum conditions for the preparation of them were determined. The phase analysis, microstructure investigation and the morphology of the samples were investigated using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) methods. At the XRD spectra only the peaks related to the anatase phase of TiO2 are appeared which demonstrated to this fact that carbon at the structure of this composite is amorphous. According to the results of SEM images the diameter of the as synthesized micro-spheres was determined between 1-3 mm. The crystallite size of TiO2 particles was 28 nm measured via the modified Scherrer's formula. The morphology investigation of TiO2/C microspheres showed that, TiO2 nanoparticles are homogenously dispersed in the carbon matrix.

Heavy metals removal by adsorption processes as general mechanisms to reduce the damage caused by heavy metals is considered. Due to a variety of reactive surface area on hydroxyapatite and cationic and anionic exchange capability, it was a matter of considerable ability is to absorb and remove heavy metals. In this study, the ability to remove heavy metal ions Pb2+and Ni2+ and placed in the structure of apatite by the method of acid-base from aqueous solution analysis. Order of elements in solution was considered so that the atomic ratio of Ca/P, Pb/P and Ni/P is equal to 1.67. Then both acid-base reacted to form apatite structure were carried out. The precipitate obtained by the techniques of XRD, FT-IR, and TEM were reviewed and evaluated. The results showed that apatite deposition method is able to eliminate lead and nickel ions from solution are almost complete. Removal mechanism of lead and nickel ions can be formed into sedimentary apatite structure or form calcium ions hydroxyapatite and adsorption of nickel and lead in calcium hydroxyapatite and cation exchange considered.

Nano photo-catalyst coatings, exposed to high-energy photons, have the ability to remove toxic organic compounds from gaseous and aqueous environments. But these coatings, due to lower surface area, are less efficient than nanoparticles. Microstructure of these coatings should be modified in order to improve their efficiency. In this study, nanostructured TiO2/Al2O3 heterogeneous films were synthesized by the sol-gel method. Quartz sheets were used as the substrates, and Al2O3 and TiO2 sols were, in turn, deposited on these substrates by the spin coating method, respectively. The deposited layers were sintered at 800oC and 500oC, respectively. Crystallization of gamma-alumina and anatase phases was confirmed by X-ray diffraction (XRD). The average crystallite size of the anatase films was measured to be about 30 nm by using scanning electron microscopy (SEM). UV-vis absorption spectroscopy was used to calculate the energy gap, and based on the measured absorption wavelengths; the total gaps were calculated to be 3.81 eV and 4.47 eV, for TiO2 and TiO2/Al2O3 layers, respectively. The emission spectra obtained by the photoluminescence analysis were used to confirm the oxygen vacancy formation. Our results showed that, by the addition of Al2O3, neutral oxygen vacancies may be thermodynamically stable stabilized in TiO2.