JOURNAL OF NEW MATERIALS
Year:2019 | Volume:9 | Issue:2 (34) |Papers Count:12

45S5 bioglass was synthesized by solid state reaction method using sodalime glass, calcium carbonate, sodium carbonate and phosphor pentoxide. XRF analysis was used to determine the glass composition, and Based on its results, the required amounts of other precursors were calculated and added to sodalime glass powder in order to obtain 45S5 composition. After that samples in the forms of powder and pellet were heat treated at different temperatures (800-1000º C). DTA and XRD analysis were done to investigate thermal and phase properties of the samples. Crystallization temperature was determined to be 690º C. Ca2Na2Si3O9 and CaNaPO4 crystalline phases were detected in all the samples. In-vitro bioactivity of samples was investigated by immersion of samples in SBF solution and further study of them by XRD and SEM analysis. Bioactivity of the samples was proved by determining HA layer formation on their surfaces. Results showed that Heat treatment temperature had more significant effect on the formation of crystalline phases than its time. Bioactivity of the sample heat treated at 1000º C for 8hr was better than other samples heat treated at lower temperatures.

In the present work, the effect of fabrication method on mechanical strength, chemical stability of BaCe0. 7Zr0. 1Y0. 2O3-δ (BCZY7)-(Li/Na)2CO3 composite electrolyte with proton conductivity, is studied. The composite electrolytes were fabricated by mixing carbonate and BCZY7 powders, synthesized in a solid state reaction, and shaping plus sintering. They also were fabricated by floating a porous BCZY7 scaffold in a molten of carbonate phase. To produce BCZY7 porous scaffold, starch powder was use as pore former. After preparing the composite electrolytes by the two mentioned methods, their mechanical, electrical and chemical stability were investigated. Analytical methods used in this study were included XRD and SEM. Mechanical strength of the fabricated composite electrolytes were determined by using ring on ring method and measuring electrical conductivity as a function of temperature were carried out by using an impedance analyzer. Results proved that, although distribution of carbonate phase in the composites fabricated by mechanical mixing is more uniform than that of the composites fabricated by infiltration process, but their mechanical strength is lower. The results also showed that chemical stability of the composite fabricated by mechanical mixing is higher, which can be due to its lower remained porosities and better distributed of carbonate phase in these composites. The results by impedance analysis and showed that electrical conductivity of the composites fabricated by mechanical mixing and sintering, in the temperature range of 500 to 700 oC is higher. Ionic conductivity of these composites, including 54 vol. % carbonate phase, at 700 oC in air determined as 0. 635 s. cm-1.

Mixtures of zinc sulfide and aluminum (ZnS-Al) with different stoichiometric molar ratios were prepared. Then the mixtures were milled in a planetary ball mill with different times. The results indicated that aluminothermic reduction of zinc sulfide progress gradually during ball milling and the reaction does not complete after 10 hours milling. The traces of mechanically induced self-sustaining reaction (MSR) did not observe in the zinc sulfide-aluminum mixtures induced ball milling. The 3 hours milled mixtures of ZnS-Al were heated isothermally under flow of argon atmosphere for one hour. The XRD analysis of the isothermal heated samples indicated that hexagonal zinc aluminum sulfide, (ZnAl2S4), is the major product. The spinel phase (ZnAl2S4) was well crystallized after isothermal heating of 3 hours milled sample in the zinc sulfide-aluminum mixtures with molar ratio of 4: 2. However, no traces of aluminum sulfide phase observed in the XRD patterns of milled mixture ZnS-Al with molar ratio of 3: 2. The possibility formation of product phases was explained using HSC software of thermodynamic assessments and phase diagram of ZnS-Al2S3 system. The results showed that addition of aluminum more than of stoichiometric ratio has negative effect on the crystallization of ZnAl2S4 spinel phase. Finally, the results of isothermal heated samples showed that Al/Zn ratio and molar ratio of zinc sulfide-aluminum in the initial mixtures have significant effect on the formation of zinc aluminum sulfide (ZnAl2S4) phase.

Nowadays, Fe-based amorphous/nanocrystalline alloys have been greatly developed due to the excellent magnetic properties, as well as their relatively low cost. In this study, the effect of process control agent (PCA) addition on the microstructure and magnetic properties of Fe75Ta5Si10C10 alloy produced by mechanical alloying was investigated. The X-ray diffraction (XRD) results showed that the addition of 2 wt. % PCA notably increases the glass forming ability (GFA) in the present alloying system and the percentage of the amorphous phase eventually reaches a value of 94 wt. % after 120 h milling. The amorphization reaction upon addition of the PCA was further confirmed by the transmission electron microscopy (TEM) analyzes. The crystallite size and lattice strain after 50 h milling were calculated as 10 nm and 1. 44% after PCA addition, and 15 nm and 1. 37% before that, respectively. The scanning electron microscopy (SEM) results confirmed that the powder prepared with the PCA exhibits finer particles with a more spherical shape. Magnetic measurements demonstrated that that both saturation magnetization and coercivity decrease and the soft magnetic behavior is improved with the PCA addition. Therefore, overall results in this study contain improvement of glass forming ability and soft magnetic properties with the PCA addition.

Nanoparticles are promising materials with a variety of applications, whose surface modification is an important technique for developing these applications. In this study, a new nanostructure was synthesized in four steps that can be used to remove pollutants from wastewater. Firstly, the graphene oxide nanoparticles (GO) were synthesized by the modified Hummer method, and then by simultaneous precipitation of ferrous and ferric ions in based atmosphere on the surface of GO, graphene oxide was magnetized. Subsequently, magnetic nanoparticles of graphene oxide (m-GO) coated by chitosan saccharide polymer with covalent bonding. The magnetic graphene oxide nanoparticles coated with chitosan (m-GO@Chi) were bonded to the cysteine-glutaraldehyde schiff’ s base (CG) with cross-linking method and their surface modified with cysteine (m-GO@Chi-Cys). After that, the nanoparticle surface correction process was investigated by using og identification analyzes. The results of the FT-IR spectroscopy indicated that surface modification was successful at each stage and the presence of epoxide, carbonyl, amino, and thiol functional groups at the nanoparticles level was confirmed. According to FESEM images, GO particles were synthesized in two dimensional and average thicknesses of 29-165nm and after magnetization, iron oxide nanoparticles with a mean size of 35-50nm were observed at the GO level. VSM analysis was used to study the magnetic properties of nanoparticles. The absence of residues in the nanosize magneticization curve and the negligible reduction in the saturation magnetization of m-GO@Chi-Cys nanoparticles, as compared to m-GO, is due to the presence of thin layer of chitosan on the primary particles.

In this study, was exposed to various Quench-Temper heat treatment cycles. Structural analyzes, mechanical tests (tension and impact) as well as analyzing the fracture surfaces of tension tests for models exposed to quenching environments (100 ͦ C and 200 ͦ C) and tempering (250 ͦ C-500 ͦ C) with austenitic temperature of 800 ͦ C, were performed. The amounts of stiffness, tensile strength and impact energy of the original raw material were 20 HRC, 724MPa and 20J, respectively. Results showed that after the heat treatment cycles, the amounts of stiffness in oil 100 ͦ C and 200 ͦ C were 50 and 55 HRC respectively, and tensile strength and impact energy for both quenching environments were near 1730 MPa and 7 J. With tempering from 250 ͦ C to 500 ͦ C, stiffness and tensile strength were decreased, and ductility and impact energy were increased (up to 40J). Also, under the quenching environment of oil with temperature of 200 ͦ C, secondary stage stiffening occurred due to more remaining austenite at tempering process temperature of 350 ͦ C. Through the tempering process, A good combination of ductility and impact energy were not achieved at 250 ͦ C and the cleavage mode of fracture at this temperature was observed. At temperatures above 500 ͦ C, ductile fracture was observed and between 250 ͦ C and 350 ͦ C, the outcome was semi-cleavage (brittle + ductile) fracture.

The creep behavior of the extruded Mg-2Mn-1Ca (MX21) and Mg-2Mn-1RE (ME21) magnesium alloys was investigated by impression testing under constant punching stress in the range 175 to 450 MPa and at temperatures in the range 423 to 498 K. Microstructural inspections with OM, SEM, EDS and XRD have proved that presence of thermally stable Mg17RE2 and Mg12RE phases in ME21 alloy and Mg2Ca phase in MX21 alloy are the main cause of enhancing the mechanical properties. For both alloys the creep behavior can be divided into two stress regimes. The stress exponents of 5 to 6 and 10 to 14 were obtained at low and high stresses, respectively. When the experimental creep rates were normalized to the pipe diffusion coefficient, however, the stress exponents of about 5-6 and 9. 5-12 were obtained for the low-and high-stress regimes, respectively. The low-stress regime activation energies of about 87. 1 to 92. 7 kJ mol-1, which are close to 92 kJ mol-1 for dislocation-pipe diffusion in the Mg, and stress exponents in the range 4 to 6 suggest that the operative creep mechanism is dislocation climb. This behavior is in contrast to the high-stress regime, in which the stress exponents of 10 to 14 and activation energies of about 122 kJ mol-1 suggest that the operative creep mechanism is dislocation creep. The creep resistance of MX21 was only slightly lower than that of the ME21 alloy, which is attributed to formation of more thermally stable intermetallics in microstructure of ME21 alloy.

One of the new methods of coating coatings is the use of electrolytic plasma method. In the present study, we try to use an electrolytic plasma method of vanadium carbide coating on the surface of the specimen and, in the next step, optimize the effective parameters in making these coatings. In this regard, the RMS test method was used to optimize the coating. The electrolyte is composed of materials such as vanadium oxide, chloride, and NaOH. That NaOH is considered as a conductive enhancer as an important parameter. In addition to NaOH, the difference in voltage and cooking time are also the most important parameters affecting the coating properties, which in this study are considered as independent variables. The dependent variables of the research can also be indicated by thickness and hardness. The results of the study show that the optimum state of the vanadium carbide sample produced by the electrolytic plasma method is 100 V, the NaOH content is about 50 g / l and the duration is 6. 65 minutes. The optimum specimen has a hardness of about 1250 Vickers and a thickness of about 29. 5 microns.

Global energy crisis caused by the rapid growth in world population and industrial growth as well as the rapid development of the society and electricity-consuming devices increases day by day and may become a crisis. Among all renewable energies, solar energy is the most promising and easy access to the energy resource to solve the global energy crisis. Perovskite solar cells have been developed as a superior photovoltaic device owing to their high photovoltaic performance and low cost of manufacturing. In all structure of perovskite solar cells, the morphology of perovskite layers plays an important role for photovoltaic performance. The formation of a compact and uniform perovskite layer with large crystal size is a significant factor to get the best device performance and efficiently. In this work, chlorine was used in precursor perovskite solution of common perovskite structure(CH3NH3PbI3) in one step deposition method (OSD) and spin-dip deposition method (SDM) to prepare mesoporous perovskite solar cells to increase cells efficiency by getting compact and smooth perovskite layers. SEM, XRD and current density-voltage (J-V) measurements by solar cell characterization were used to investigate cell performance. As a result, in the presence of chlorine in both OSD and SDM methods power conversion efficiency has been enhanced from 3. 87% to 6. 76% and from 7. 84% to 10. 27% respectively.

In this study, the inhibition effect of metoral tablet as corrosion inhibitor for mild steel in 0. 5 M phosphoric acid solution was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy, and the scaning electron microscopy techniques. The results showed that the maximum inhibition efficiency of this drug was found to be 300 ppm, and decreased with the increase in temperature for all of the solutions. Potentiodynamic polarization curves indicated that the inhibitor acts as mixed-type inhibitor and the corrosion current density decreased with increasing the inhibitor concentration. The results obtained from analysis of EIS data was in good agreement with those achieved by the polarization measurements. The adsorption studies indicated that the adsorption of the inhibitor on the alloy surface obeys Langmuir adsorption isotherm. The adsorption process is spontaneous and exothermic process and the entropy of adsorption in this solutions decreases. Keywords: Electrochemical Impedance Spectroscopy, Potentiodynamic Polarization, Phosphoric Acid, Mild Steel, Metoral.

The simultaneous production of hydrogen and degradation of organic pollutants (methyl orange and cyanide ion) was successfully achieved using TiO2-10%ZrO2 photocatalyst which was synthesized in our previous study. With this catalyst, the degradation of methyl orange (or cyanide ion) was accompanied by the concurrent production of H2. The effects of operational variables, including pollutant concentration, solution pH and irradiation time, on the rate of hydrogen production were investigated. The activity of TiO2-10%ZrO2 gradually decreased with increasing pH, which makes its application of limited to the acidic pH region. The effect of concentration of the pollutants on the hydrogen generation rate is consistent with a Langmuir-Hinshelwood kinetic model. The enhanced photocatalytic activity could be explained in terms of reduced electron-hole recombination via hole consumption by pollutants. It is concluded that, under certain experimental conditions, it is possible to obtain significantly enhanced rates of photoinduced hydrogen production from TiO2-10%ZrO2 with simultaneous degradation of methyl orange and cyanide ion.

In this study, Fe3O4@CuO core-shell nanostructures were synthesized through simple chemical methods for using in degradation process of chemical dyes application. Structural, morphological, magnetic, and optical properties of the obtained product were studied by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), hysteresis loop, absorbance (UV-Vis), and photoluminescence (PL) spectra. The XRD patterns revealed the formation of multi-crystalline Fe3O4 (Cubic) and CuO (Monoclinic) phases. Electron microscopy images also show formation of structures in nano-dimension with spherical-and belt-like morphologies. Magnetic studies that carried out by hysteresis loop show decreases in magnetic properties of core-shell nanostructures which can be due to weak magnetic properties of CuO. Investigating optical properties of core-shell nanostructures demonstrated the existence of absorbance edge at a visible region that is proper for solar ray absorbance and participates in photocatalytic degradation activity. Tauc plot also show decreasing in optical energy band gap of core-shell compare to the shell nanostructures.