Papers by Keyword: SRO

Abstract: Strontium Oxide (SrO) nanoparticles have a specific structure, and excellent optical, mechanical, and thermal properties, within direct bandgap semiconductors applications. SrO impact on the optical and electrical properties of newly (PVA-PEG/ SrO) nanocomposite were investigated. The electrical properties were measured at 100 Hz – 6 MHz frequencies. An increase in frequency caused a reduction in the dielectric loss (δ) and dielectric constant (ɛ). ɛ value revealed an improvement with an increased loading ratio of SrO. The optical properties of the (PVA-PEG/SrO) nanocomposite showed a reduction in the energy gap values. In contrast, the absorption, extinction coefficient, absorption coefficient, optical conductivity, refractive index, and dielectric constant (imaginary, real) increased with the increased concentration of SrO NPs.

Abstract: In the present report, a two dimensional (2D) model was developed to describe the fluid dynamics, heat and mass transfer of a Chemical Vapor Deposition activated by a Hot Filament (HFCVD) reactor, as well as the chemical generation of the precursor species which are present in the growth of non-stoichiometric silicon rich oxide (SRO) films. The SRO is known for have excellent photo luminescent properties which are useful in optoelectronic applications. This material can be obtained by the HFCVD technique which offers important advantages such as the easily to obtain thin films with diverse structural, compositional and optical characteristics. During deposition is a priority to control key parameters as inlet flow, substrate temperature and pressure so it compels to know previous theoretical information about these parameters which can be obtained by computational simulation. Therefore, by means of commercial Computational Fluid Dynamics (CFD) were solved the continuity, momentum and energy equations in steady state. Also, a thermodynamic equilibrium study of the SiO₂(s) + H₂ (g) reaction was carried out with the Factsage software. The thermodynamic equilibrium results provide the main chemical species which are present during the deposit process of the SRO films. The 2D model was used to simulate the temperature and velocity distribution of the hydrogen in the deposit process. The theoretical calculated temperatures were compared with those obtained experimentally by thermocouple measurements. From the simulation results, the temperature and gas velocity profiles were obtained at different hydrogen flow levels (50, 75, 100 sccm) and temperature source-substrate distances (5, 6 and 7mm) for a 50 sccm level. SEM micrographs and profilometry measurements disclose that the outlet configuration affects substantially both the thickness and surface uniformity of the SRO films. This parameter was modified to obtain a better quality (thickness and uniformity) and a large deposit area.

Abstract: Ta₂O₅, Ta₂O₅–SrO and Ta₂O₅–TiO₂ photocatalysts were prepared by hydrothermal method and characterized using X-ray diffraction (XRD), Ultraviolet-visible Diffuse Reflectance spectroscopy (UV-Vis DRS) and Thermogravimetry (TGA). In synthesized series of TiO₂-Ta₂O₅ catalysts, formation of anatase TiO₂, hexagonal Ta₂O₅ and titanium tantalates were observed. For Ta₂O₅-SrO (Ta:Sr= 1:1) formation of mixed oxide and crystallinity was observed at calcinations temperature at 1100 °C (5hr). These synthesized catalysts were used for degradation study of methylene blue. The result demonstrated that the photocatalytic activity of the mixed oxides [Ta₂O₅-TiO₂(1:1), Ta₂O₅-TiO₂(2:1), Ta₂O₅-TiO₂(1:2), Ta₂O₅-SrO (Ta:Sr= 1:1)] was higher than that of Ta₂O₅ alone.

Abstract: A series of glasses with nominal composition in (53-x)B₂O₃:11SiO₂:34SrO:1Bi₂O₃:1TiO₂: xHo₂O₃ (BSSBT) where x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol% was synthesized by conventional melt quenching method. The as-prepared glasses have been investigated and reported for their physical and optical properties. The results show that, the densities and refractive index increase with increasing Ho₂O₃ content in the glasses. The absorption peaks of doped glasses were observed at a wavelength of around 420, 460, 480, 540, 640 and 900 nm which are assigned to ⁵I₈ ® ⁵G₅, ⁵G₆, ⁵F₃, (⁵F₄+⁵S₂), ⁵F₅ and ⁵I₅ transitions of Ho³⁺, respectively.

Abstract: The addition of different dopants affects the densification and electrical properties of TiO₂ based varistor ceramics. The nonlinear current (I) and voltage (V) characteristics of titanium dioxide are examined when doped with small quantities (0.5-2 at.%) of strontium oxide. This paper discusses the electrical properties of such an SrO doped TiO₂ system, and demonstrates that some combinations produce electrical properties suitable for use as low voltage varistors. The high value of the nonlinear coefficient (α) (6.6), the breakdown field strength (Eb) (328 V/cm) and the leakage current (Ir) (0.22 mA/cm²) obtained in a system newly doped with SrO, are all adequate properties for application in low voltage varistors.

Abstract: Alite-strontium calcium sulphoaluminate cement, a new type of cementitious material, is synthesized by combining strontium calcium sulphoaluminate with minerals of Portland cement clinker. The influences of excessive SO₃ and SrO on the microstructure and performances of this cement are studied by XRD, SEM-EDS and lithofacies. The results show that the optimal excessive mass fraction of SO3 and SrO are 50% and 80%. The compressive strength of the cement prepared under the testing conditions reaches to 32.8MPa, 66.8MPa and 126.4MPa at 1d, 3d and 28d curing ages, respectively. The additions of SO₃ and SrO are benefit to improve the content of strontium calcium sulphoaluminate, and promote the formation of alite at low sintering temperature.

Abstract: Poly- and single-crystalline BaTi2O5 co-substituted with SrO and ZrO2, Ba0.99Sr0.01(Ti1-xZrx)2O5 (BT2SZ) were prepared by arc-melting and floating-zone (FZ) melting, respectively. The specimens showed a significant (020) orientation. The highest permittivity of poly-crystalline BT2SZ was 3880 at x = 0.005 and that of single-crystal was 27000 at x = 0.005. The Curie temperature (Tc) of poly-crystals decreased from 750 to 640 K with increasing x from 0 to 0.026 and that of single-crystals decreased from 750 to 710 K with increasing x from 0 to 0.008. The highest remnant polarization of single crystalline BT2SZ was 7.8×10-2 Cm-2 at x = 0.008, higher than that of the poly-crystal.