V. Jayaram; K. P. J. Reddy
Abstract
This paper presents a novel method of interaction of zirconia with strong shock wave in presence of dissociated/non-dissociated gas species for short duration using shock tube. Cubic zirconia (c-ZrO2) was synthesized by solution combustion method and exposed to strong shock heated N2 and O2 test gases ...
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This paper presents a novel method of interaction of zirconia with strong shock wave in presence of dissociated/non-dissociated gas species for short duration using shock tube. Cubic zirconia (c-ZrO2) was synthesized by solution combustion method and exposed to strong shock heated N2 and O2 test gases in a free piston driven shock tube (FPST). FPST is used to heat the test gases to very high temperature of about 7540-9530 K (estimated) and reflected shock pressure of about 65-70 bar for short duration (2-3 ms). X-ray diffraction (XRD) study shows the phase transformation of c-ZrO2 to m-ZrO2. Scanning electron microscopy (SEM) images shows the formation of sharp nano/micro zirconia needles due to melting and nucleation during super heating and cooling at the rate of about 10 6 K/s. These types of sharp nano/micro needles are observed for the first time in this shock tube experiment. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy show no change in electronic structure and chemical composition of ZrO2 which indicates that the reaction is fully catalytic. This unique experimental methodology can be used to study the chemistry of materials under extreme thermodynamic conditions which is of seminal importance in space, nuclear and other high temperature applications.
R. Siddheswaran; Petr Nov
Abstract
Thin films of BaTiO3 and Co, Nb co-doped BaTiO3 on glass and Si (100) substrates were deposited by RF sputtering (at 350 ºC), and annealed. The amorphous and crystalline phases were observed for the as-deposited and annealed samples, respectively from the X-ray diffraction (XRD) studies. The magnetic ...
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Thin films of BaTiO3 and Co, Nb co-doped BaTiO3 on glass and Si (100) substrates were deposited by RF sputtering (at 350 ºC), and annealed. The amorphous and crystalline phases were observed for the as-deposited and annealed samples, respectively from the X-ray diffraction (XRD) studies. The magnetic behaviour of the pure and doped BaTiO3 films was studied by vibrating sample magnetometry (VSM). In this study, the ferromagnetic behaviour at room temperature was observed in the Co, Nb co-doped BaTiO3 of both amorphous and crystalline films. The annealed polycrystalline Co, Nb co-doped BaTiO3 films have the larger saturation magnetization and coercivity than the amorphous films. The room temperature ferromagnetic responses were also observed by the Magneto-optical Kerr effect (MOKE) measurements for both as-deposited and annealed samples.
Fatma Pinar Gokdemir; vecihe Ece Yuzbasioglu; Bahadir Keskin; Orhan Ozdemir; Kubilay Kutlu
Abstract
Through a modified sol gel route with titanium isopropoxide (TIP) and acetic acid, titanium dioxide (TiO2) thin films were deposited by dip coating. Employing acetic acid as modifier and without inclusion of water in hydrolysis leaded to control the degree of condensation-oligorimerization of the precursor ...
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Through a modified sol gel route with titanium isopropoxide (TIP) and acetic acid, titanium dioxide (TiO2) thin films were deposited by dip coating. Employing acetic acid as modifier and without inclusion of water in hydrolysis leaded to control the degree of condensation-oligorimerization of the precursor and formation of anatase phase only upon annealing. Direct allowed energy band gap 3.87 eV verified the anatase phase of the film. Impact of temperature on structural properties was deduced by FTIR and UV-Visible spectroscopies. Due to the reduction in band gap with increase in annealing temperature, injected Li + charge amount dropped in anatase compared to the amorphous (unannealed) films.
