Journal of Advanced Processes in Materials Engineering
Year:2018 | Volume:11 | Issue:4 (43) |Papers Count:23

In this study the effect of substrate temperature (from room temperature (RT) to 400° C) on the sructural and physical properties of cabon thin films were investigated. The films were prepared by ion beam sputtering deposition technique on glass substrate. Optical and structural properties were studied by UV-visible spectroscopy, Raman spectroscopy and atomic force microscopy, respectively. The results showed that optical transparency decreased with the increase in the substrate temperature. Raman spectra indicated a structural transition from amorphous to graphite-like phase by increasing temperatures since in the spectra; D peak disappeared in the layer at the substrate temperature of 400° C. The result of sheet resistance and the optical band gap showed the reduction trend by the increase in the substrate temperature from 100 to 400° C. However the enhancement of the surface roughness with the substrate temperature was observed. In the layer prepered with the substrate temperature equal to 100 ° C, a minimum size of the graphite crystallites (with sp2 bands (La)) was equal to 0. 36 nm and a maximum optical band gap was equal to 3 eV.

In the present study, hydroxyapatite (HA) Single layer TiO2 single layer, HA-TiO2 double layer and functionally graded HA/TiO2 coatings were deposited on Ti-6Al-4V titanium alloy substrate by electrophoretic deposition technique (EPD). Impact resistance of coatings were measured by ball drop impact test and the results showed that the HA/TiO2 functionally graded coating has more impact resistance compare to HA single layer and HA-TiO2 double layer coatings. The wear resistance of coatings were investigated by pin on disc method. The normal load and sliding distance were 0. 5 N and 50 m respectively and the worn surface was observed using scanning electron microscope (SEM) and analyzed by ImageJ software. The results showed that the HA/TiO2 functionally graded coating has more wear resistance compare to HA single layer. Additionally, investigation of worn surface of coatings showed that all of the coatings have abrasive mechanism but wear mechanism for functionally graded coating, changed and delamination was added to abrasive mechanism.

In this study, barium strontium titanate/cobalt zinc ferrite composites that composed of two different magnetic phases were investigated. Pyroelectric phase consists of barium strontium titanate particles with particle size of about 150 nm and soft magnetic phase consists of cobalt zinc ferrite nanoparticles with particle size of about 30 nm. Two phases were prepared with sol-gel method and under appropriate stoichiometry. XRD analyses indicated formation of pure phase for each magnetic phases and FESEM analysis indicate the structural properties of Cobalt-Zinc ferrite and Barium Strontium Titanate nanoparticles. Investigation of permittivity, permeability and reflection loss of samples indicated the response of electromagnetic waves to these samples in the frequency range of 1-18 GHz. According to the reflection loss of composites, there are two mechanisms for the absorption of electromagnetic waves. In the first region of this frequency band, magnetic loss from Cobalt-Zinc ferrite nanoparticles is dominate and in the last region of this frequency band, dielectric loss from barium strontium titanate is dominate.

A copper manganese ferrite nanoparticles from effective ferrites that applicable in sensitivity investigations was prepared in this study. Co-precipitation method was used for synthesis of this ferrite that is useful method for synthesizing of these compounds. For structure evaluation, X-ray diffraction (XRD) experiments for phase formation confidence and transmission electron microscopy (TEM) for formation of nanoparticles below 30 nm scale confidence were used. By X-ray fluorescence (XRF) experiment exact percent of each element was determined in copper manganese ferrite compound. By (AGFM) experiments the magnetic behavior of powder and disk sample of copper manganese ferrite nanoparticles was determined. For sensitivity properties investigation of these nanoparticles, mentioned nanoparticles were converted to a tablet form. This tablet was putted in a temperature controlled box. Nine solvents were vaporized (gases) and exposed to this nanoparticles. Responses to these gases were transmitted to a computer by an electronic board connection. Result information was analyzed by software. Sensitivity study of this nano sensor was tested by using carbon tetrachloride, ethanol, methanol, acetonitrile, acetone, vinyl acetate, acrylonitrile, ammonia and formamide. Among these gases ethanol had the best sensitivity in 100˚ C temperature.

In this study, using Ag-Cu brazing metal alloy, effects of brazing time on microstructure and strength of Al2O3 / Ti6Al4V joints were investigated. Therefore, ceramic/metal couple brazed by electrical furnace. Then, brazed specimens were examined by scanning electron microscope and x-ray diffraction tests. Several phases observed at the interface area and EDS analysis were recognized titanium, copper, silver, aluminum, vanadium and oxygen in this phases. With more study using x-ray diffraction patterns and phases diagrams some intermetallic compounds identified. This compounds were Ti-Cu intermetallices near to Ti6Al4V side and reactive layer of Cu2O +CuAlO2 near to Al2O3 ceramic side. Also, microstructural surveys revealed the narrow reaction layer and a little intermetallic compounds in specimen brazed for 10 minutes. With increasing brazing time, reaction layers grossed rapidly. This chemical variation made dimensional changes at metal/ceramic interface. Therefore, some crakes observed in specimen brazed for 25 minutes. Maximum of shear strength equal 295 Mpa measured in specimen brazed for 15 minutes.

Replacement of metals with bioabsorbable polymers has shown promising results for fabrication of biomedical implants. But polymers themselves have some restrictions such as inability in osteoconduction and integration with surrounding tissue, induce foreign body reactions, reducing of pH by degradation products which can results in unwanted inflammatory reactions in related place, and weak mechanical properties in compare to metallic types. In order to alleviate these problems using of polymeric composites including bioactive particles is taken into consideration. In the present work 45S5 bioactive glass and hydroxyl apatite (HA) ceramic particles were used for fabrication of poly(L-Lactic acid) (PLLA) composite screws. Microstructure and thermal properties of produced samples were evaluated by differential thermal analysis (DTA), thermogravimetry (TG), scanning electron microscopy (SEM) and particle size analysis (PSA). Also for evaluation of osteogenic activity of produced samples, alkaline phosphatase (ALP) and Alizarin Red Staining assays were carried out and cytotoxicity was conducted through MTT assay. In compare to PLLA screws, PLLA/HA and PLLA/45S5 composites showed more and less thermal stability respectively. The results of cell analysis assays showed no cytotoxicity and both composites revealed proper osteogenesis potentials.

Nano-crystalline Yttrium aluminum garnet (YAG, Y3Al5O12) were synthesized by normal co-precipitation method using yttria and aluminum nitrates as the starting materials and ammonium hydrogen carbonate (AHC, NH4HCO3) as precipitant. To investigate the effect of temperature and holding time the resultant precursors were calcined at 900-1100 ° C for 2 h also at 1100 ° C for other durations (15, 30, 45 and 60 min). The evolution of phase composition and micro-structure of the as-synthesized YAG powders were characterized by different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermal analyses (TG/DTA), Specifi c surface area analyses (BET) and field emission electron microscopy (FESEM). The cubic YAG phase with an average grain size of 33 nm and specifi c surface area of 30 m2/g was completely formed at 1000 ° C. In addition, pure YAG nano powders were obtained at 1100 ° C in only 15 min calcination. Results showed that compared with increasing holding time, raising of temperature have more intense effect in increasing YAG crystal or particle size.

In this paper, the effect of tool rotation speed on the mechanical properties and corrosion behavior on dissimilar joints Friction Stir Welds between 5083 Aluminium alloy and pure Titanium is investigated. At first, with primary welding parameters range necessary to achieve suitable connection obtained and then by changing tool rotation speed, mechanical and corrosion properties of heat affected zones, welding zones and cross section zones, by using polarization Tafel test and Electrochemical Impedance Spectroscopy was investigated and the result were compared. the result indicates that corrosion behavior of connections, is impressionable of the tool rotation speed and welding zone and heat affected zones have weaker corrosion resistance compared to the base metals.

In this study, Manganese cobaltite (MnCo2O4) spinel powders were synthesized by co-precipitation method. X ray diffraction (XRD) patterns show that the spinel phase was formed at around 350° C. Formation of spinel phase was further completed by increasing temperature up to 1000° C. Additionally, XRD patterns prove that MnCo2O4 spinel material has been stable in this temperature range. Field emission scanning electron microscope observations show that plate like particles with an average diameter of 148 and thickness of 18 nm was converted to equiaxed particles with an average particle size of 1. 5 µ m by increasing calcination temperature from 350 to 1000° C. Investigation of the coating of uncalcined and calcined powder on AISI 430 ferritic stainless steel shows that a proper dense coating is developed on the stainless steel surface by using uncalcined precursor powders. And also, this coating performs well by prohibiting of outward diffusion of Fe from the substrate. In this way, a low thickness chromia layer (Cr2O3) is formed between the coating and the substrate. EDX analysis shows that a mixed spinel zone is formed in the interface of the coating and the substrate due to diffusion of some elements such as Mn, Cr, and Fe from substrate to the coating, as well as Mn and Co from coating to the substrate.

The inhibition effect of Myrtus extract on steel corrosion in 1. 0 M HCl solution was investigated by means of weight loss measurements, electrochemical polarization, electrochemical impedance microscopy and chemical quantum study. The results showed that Myrtus acts as a good inhibitor and the inhibition efficiency of this compound increases with increasing inhibitor concentration and in the presence of 1000 mg/L of the inhibitor will increase to 82%. Polarization curves showed that Myrtus extract acts as an efficient mixed type inhibitor. EIS plots indicated that the polarization resistance increased and double-layer capacitance decreased upon the addition of Myrtus to the solution. The adsorption of Myrtus on the steel surface was found to obey Temkin adsorption isotherm and the values of free adsorption energy indicate the spontaneous and chemical adsorption of inhibitors on mild steel surface. Also, quantum chemical calculations were used to correlate the adsorption of two compounds of Myrtus extract with its electronic structural parameters.

To improve the process of thermal decomposition of ammonium perchlorate (for improving and modification propellant burning rate), the copper oxalate was coated by ammonium perchlorate through sol-gel method. Scanning electron microscopy (SEM) and thermal analysis(TG/DSC) were used for coating analysis of the copper oxalate on ammonium perchlorate and behavior changes of thermal decomposition of ammonium perchlorate in the presence of nano copper oxide made of nano copper oxalate respectively. The results of catalytic thermal decomposition of ammonium perchlorate shown that the cover of copper oxalate nanoparticles has a good effect on the thermal decomposition of ammonium perchlorate and the thermal decomposition temperature of ammonium perchlorate reduced from 422 º C to 299 º C. In addition, the thermal decomposition peaks of ammonium perchlorate (compared to thermal decomposition of pure ammonium perchlorate) were integrated. In order to evaluation of the effect of nano-catalyst on the thermodynamic and kinetic parameters one of the model-free methods as Ozawa-Flynn-Wall (OFW) equation was used. As result, it was observed that nano-catalyst reduced the activation energy, the frequency factor and thermodynamic parameters in different conversion rates 0. 2, 0. 4, 0. 6 and 0. 8, respectively.

Today, magnesium alloys as the new generation of biodegradable alloys, have attracted the attention of many researchers. In this research, the corrosion behavior of cast Mg-5Zn-1Y containing different amounts of calcium (0, 0. 1, 0. 5 and 1 weight percentage) was investigated. The microstructure of the alloys was analyzed using optical and scanning electron microscopes, and the corresponding phases were detected by X-ray diffraction. Corrosion behavior of cast alloys was measured using electrochemical polarization and immersion tests. Metallography analysis revealed that microstructure of the Mg-5Zn-1Y alloy includes α-Mg matrix and Mg3YZn6 lamellar phase formed at the grain boundary. The addition of calcium to the alloy refined the grains and resulted in the formation of continuous Ca2Mg6Zn3 at grain boundaries. No passive zone was detected in polarization curves, meaning domination of active polarization, indicating increased corrosion rate due to grain refinement which can be attributed to calcium addition in the alloy. The polarization and immersion tests results confirmed that the alloy Mg-5Zn-1Y-0. 1Ca has the lowest corrosion rates among the investigated alloys, and the more the calcium content, the higher the corrosion rate due to the formation of cathodic Ca2Mg6Zn3 phase.

In this study, Fe3O4 / SiO2 / TiO2 composite was prepared with core-shell-shell structure using a wet chemical method. At first the composite Fe3O4 / SiO2 was synthesized via Tetraethyl orthosilicate (TEOS) precursor. Then a shell of TiO2 was coated directly on it. Fe3O4 / SiO2 / TiO2 microstructures produced were characterized by environmental scanning electron microscopy analysis (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy devices (FTIR). The results showed that SiO2 and TiO2 layers has been coating successfully. The results indicated that the mean size of Fe3O4 particles was about 300-400 nm and thickness of the TiO2 and SiO2 shells was about 4 and 30 nm, respectively. magnetic properties of the synthesized composite were studied by Vibrating Sample Magnetometer (VSM). Pure Fe3O4 and Fe3O4@SiO2@TiO2 composites magnetization saturation (Ms) obtained 80 and 37 emu/g, respectively. also the remanent magnetization (Mr) value of Fe3O4 and Fe3O4 / SiO2 / TiO2 microstructures was 8 and 6. 43 emu/g, respectively.