1,721,073 research outputs found
Effect of Mgo Content Changes (8 To 15-percent) On the Devitrification of Glasses Obtained From Porphiric Sands, MgO and TiO2 (4-percent)
No full textGlasses have been prepared from porphiric sands, TiO2 and MgCO3 and the effect of changing the MgO content on the isothermal devitrification has been studied. The experimental data suggest that an increase in MgO content increases the devitrification rate owing to a greater aptitude to form nuclei, so that a fine grained microstructure can be obtained more easily
Devitrification Behavior of A Glass Obtained From Porphyric Sands With Addition of Tio2 (4-percent) and Mgo (8-percent)
No full textThe non-isothermal devitrification of a glass obtained from porphyric sands with addition of TiO2 (4%) and MgO (8%) has been studied. Scanning electron micrography observations suggest that the glass demixes on quenching. After prolonged heat treatment at temperatures in the glass transformation range an evolution of the glass texture is observed, with formation of non-spherical particles of a separated phase. This does not seem to influence greatly the crystal growth activation energy, which has been evaluated as being E = 105 ± 5 kcal mol−1. The maximum nucleation rate temperature has been estimated to be T = 710°C. Evidence has been found that the glass-glass interfaces produced by demixting provide alternative sites of nuclei formation
Thermal-expansion Behavior of Glass-ceramics Derived From Prophyric Sands
No full textThe thermal expansion curves are reported for ''as-quenched'' and ''heat-treated'' glasses obtained by adding MgO (8-16%) and TiO2, (4%) to porphyric sands of composition: SiO2=72.40%; Al2O3=13.85%; K2O=4.60%; Na2O=3.00%; Fe2O3=2.15%; CaO= 1.30%; MgO=0.84%; TiO2=0.20%; loss on calcination = 2.06%. The variations in the glass transition temperature T-g, the thermal expansion coefficient alpha, and the dialatometric softening temperature M(g), are discussed. The experimental results can be explained by assuming that Na2O, K2O and CaO (all or a part of them) segregate preferentially with respect to MgO into the titania-rich phase. Diffusion appears to fall as the MgO content is increased
Structure and Thermal Evolution of Glasses Obtained From Porphiric Sands, Mgo (15-percent) and Tio2 (0-16-percent)
No full textAnalysis of residual stress distribution in shot peened AL 6082 alloy subjected to fatigue loading
No full text
Pulsed laser deposition of YBCO thin films on metal substrates with YSZ buffer layer
No full textWe have deposited by pulsed laser ablation YBCO/YSZ bilayers on flexible Ni-based (Inco alloy C-276) substrates. As confirmed by X-ray diffraction spectra, the YBCO film grows mainly along the c-axis direction. However, a mosaic spread of 10 degrees, evaluated from the (005) YBCO pole figure, and the results of a film texture analysis indicate that more effort is required to obtain a complete c-axis orientation along with in-plane alignment for the YBCO layer
"Devitrification of a glass obtained from porphiric sands, MgO(15%) and TiO2(4%)
No full textA glass of composition: SiO2 = 59•84%; Al2O3 = 11•45%; MgO = 15•34%; TiO2 = 4•23%; K2O = 3•80%; Na2O = 2•48%; CaO = 1•08%; Fe2O3 = 1•78%; was prepared from porphyric sands by addition of MgO and TiO2. The quenched glass is demixed on a very fine scale. The non-isothermal devitrification has been studied. Three-dimensional crystal growth has been observed. The experimental data suggest a mechanism controlled by the crystal-glass interface reaction. The crystal growth activation energy Ec = 467 ± 20 kJ/mole has been evaluated. The temperature of most efficient nucleation is approximately TN = 720°C
Magnetic and structural properties of nanocomposite Co-Ni-Cr-Al-Y-N thin films
No full textThe relation structural and magnetic properties of Co-Ni-Cr-Al-Y-N thin films deposited by reactive r.f. magnetron sputtering was investigated. A marked change in the magnetic behaviour of the films with the different nitrogen partial pressure in the Ar/N2 deposition atmosphere was observed and qualitatively explained in correlation with the phase composition. The nanocrystalline metal solid-solution obtained at low N2 content and the nanocrystalline nitride/amorphous composite obtained at high N2 content are not magnetic, whereas the amorphous phase produced for intermediate N2 pressures behaves like a ferromagnetic semi-permanent material. The results demonstrate the possibility of modulating the magnetic properties of r.f. magnetron sputtered Co-Ni-Cr-Al-Y-N thin films, thus opening a new route for magnetic multilayer deposition
- …
