Showing 25 results for Titanium
M. Mahmoudi Saleh Abad, M. Zandrahimi, H. Ebrahimi Far,
Volume 37, Issue 3 (12-2018)
Abstract
In order to improve the oxidation and hot corrosion resistance of steels, various elements including aluminum, chromium, silicon, titanium or combination of these elements can be diffused on to the surface of steel. In this study, aluminum and titanium were simultaneously co-deposited onto the AISI 430 ferritic stainless steel substrate by the pack cementation process. Coating was examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The coating consised of two layers with the thickness of approximately 14 microns. The results obtained by XRD showed the existence of FeTi, TiO2, AlTi, Al3Ti and Al5Ti phases in the coating. Isothermal oxidation and cyclic oxidation were carried out at 1000○C. It was showed that the diffusional coating of aluminum-titanium led to the improvement of cycle and isothermal oxidation resistance.
A. Sheikhali, M. Morakkabati, S. M. Abbasi,
Volume 38, Issue 1 (6-2019)
Abstract
In this paper, in order to study the flow behavior and elongation of as-cast ingots of SP-700 titanium alloy, hot tensile test was done in α/β dual phase and β single phase regions using strain rate of 0.1 s-1. Results showed that the hot tensile behavior of SP-700 in the α/β dual phase region (700-900 ºC) was different from the β single phase one (950-1100 ºC) due to the nature of alpha and beta phases and their crystallographic structure. This was since the number of slip systems and deformation mechanism in HCP structure were different from those in BCC structure. Beside, the intensive variation of elongation in microstructural studies showed that the dominant mechanism of hot tensile deformation of SP-700 alloy was dynamic recovery (DRV). Thus, serration of grain boundaries and occurrence of DRV were the reasons for the increase of elongation with the rise of temperature. However, beta grains growth and occurrence of grain boundary fracture made a slight decrease in elongation in the temperature range of 1000-1100 ºC.
A. Jafari, S. Khademi, M. Farahmandjou, A. Darudi, R. Rasuli,
Volume 38, Issue 2 (9-2019)
Abstract
Titanium dioxide nanoparticles (TiO2) are known as a widely used photocatalyst. In order to improve the performance of these nanoparticles, the recombination of the electron-cavity pair must be reduced and the absorption rate of the visible region should be expanded. One way to increase the performance of these nanoparticles is using cerium doped TiO2. In the present study, pure and doped titanium dioxide nanoparticles were made by the electrical discharge method. The effect of cerium dopants on the structural, morphological and optical properties were studied by x-ray diffraction (XRD), scanning electron microscopy (FESEM), diffused reflection spectroscopy (DRS), photoluminescence (PL) and infrared fourier transform (FTIR) spectroscopy analyses. XRD analysis revealed that the size of TiO2 nanocrystals was decreased to 7.7 nm. The FESEM morphology of the samples also showed that the uniformity of the Ce doped TiO2 was decreased. Further, the DRS results indicated that the band gap energy of Ce-TiO2 was decreased to 2.24 eV. The photoluminescence results demonstrated that the intensity of PL was reduced for the Ce-TiO2 sample, which reduced the recombination of the electron-hole coupling and increased the photocatalytic activity in the doped sample.
H. Ebrahimifar, M. Zandrahimi, F. Ekhlaspour,
Volume 38, Issue 3 (12-2019)
Abstract
One of the most effective ways to improve oxidation resistance of interconnects used in solid oxide fuel cells (SOFCs) is to apply a layer of conductive protective coating. In this study, Crofer 22APU ferritic steel was coated in a titanium- based powder mixture by pack cementation method. The powder composition for titanium coating was Ti 20 wt.%, NH4Cl 5 wt.% (activator) and Al2O3 75 wt.%. The optimum temperature and time to obtain the best coating quality in terms of adhesion and porosity were 800 °C and 7 hours, respectivly. The obtained titanized coating consisted of TiFe, TiFe2 and TiCr2 phases. The results of isothermal and cyclic oxidation tests carried out at 900 °C, showed that titanium-coated samples had better oxidation resistance than non-coated samples. Microstructural and phase studies of coated and oxidized samples were performed by scanning electron macroscopy (SEM) and X-ray diffraction analysis (XRD). During oxidation process, the coating layer was converted into TiFe, TiFe2, TiFe2O5, TiO2 and TiCr2O4 phases. The coated specimens had lower weight gains relative to uncoated samples showing that coating effectively protects the substrate against oxidation. Moreover, coated samples had higher electrical resistance than uncoated ones.
H. Fallah-Arani, S. Baghshahi, A. Sedghi, F. Shahbaz Tehrani,
Volume 40, Issue 2 (9-2021)
Abstract
In this research, the influence of titanium dioxide nanoparticles on the structural and magnetic properties of high-temperature superconductor Bi1.6Pb0.4Sr2Ca2Cu3O10+θ (Bi-2223) from the Bi-based ceramic system (BSCCO) was studied. In order to investigate the synthesized samples, X-ray diffractometry and magnetic measurements were performed. Based on the magnetic measurements, the superconductivity transition temperature declined with the increase in the nanoparticles' content. The addition of nanoparticles affected on the hysteresis loop width. Accordingly, the compound containing 0.2 wt.% nanoparticles had the maximum magnetization, hysteresis loop width, and critical current density.
