The Effect of Nano-SiO2 on the Structural, Electrical and Magnetic Properties of SiO2-LiFe5O8 Glass–ceramics Prepared by Sol Gel Auto-combustion Processing

The glass–ceramic with the composition x(LiFe5O8)/(100 – x) SiO2 (x = 20, 30, 40, 50, 100 wt. % ) were prepared by sol gel auto-combustion method. The influence of the SiO2 ratio in the glass-ceramics strucure prepared was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Crystalline phases (LiFe5O8, SiO2, Fe2O3) were observed by X-ray powder diffraction in the glasses annealed at 800°C for 2h. The crystallite size was found to increase from 27.29 nm (x = 20%) to 91.48 nm(x = 100 %). The microstructure of the formed powders was SiO2 ratio dependent. Increasing the SiO2 ratio was found to inhibit the grain growth of the formed ferrite. The electrical conductivity of glass-ceramics samples were raised with increasing the concentration of SiO2 ratio as the result of increasing the hopping of electrons between Fe2+ and Fe3+ ions. The magnetic characteristics of the prepared glass ceramics were performed using a vibrating sample magnetometer in function of the magnetic field. The samples heat -treated at 800°C for 2h present a ferrimagnetic behavior. Alongside, the formed crystalline silicate lithium ferrite had good magnetic properties. High saturation magnetization (51.9 emu/g) was attained the formed ferrite sample of x = 100 % ratio annealed at 800°C for 2h

The Effect of Nano-SiO2 on the Structural, Electrical and Magnetic Properties of SiO2-LiFe5O8 Glass–ceramics Prepared by Sol Gel Auto-combustion Processing

The glass–ceramic with the composition x(LiFe5O8)/(100 – x) SiO2 (x = 20, 30, 40, 50, 100 wt. % ) were prepared by sol gel auto-combustion method. The influence of the SiO2 ratio in the glass-ceramics strucure prepared was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Crystalline phases (LiFe5O8, SiO2, Fe2O3) were observed by X-ray powder diffraction in the glasses annealed at 800°C for 2h. The crystallite size was found to increase from 27.29 nm (x = 20%) to 91.48 nm(x = 100 %). The microstructure of the formed powders was SiO2 ratio dependent. Increasing the SiO2 ratio was found to inhibit the grain growth of the formed ferrite. The electrical conductivity of glass-ceramics samples were raised with increasing the concentration of SiO2 ratio as the result of increasing the hopping of electrons between Fe2+ and Fe3+ ions. The magnetic characteristics of the prepared glass ceramics were performed using a vibrating sample magnetometer in function of the magnetic field. The samples heat -treated at 800°C for 2h present a ferrimagnetic behavior. Alongside, the formed crystalline silicate lithium ferrite had good magnetic properties. High saturation magnetization (51.9 emu/g) was attained the formed ferrite sample of x = 100 % ratio annealed at 800°C for 2h

Establishing and characterizing a permanent magnet system for the prototype of NIS's Kibble balance

The Kibble balance experiment is used to redefine the kilogram as a unit of mass based on the Planck constant. To demonstrate and understand the basic principle of the Kibble balance, the National Institute of Standards (NIS)-Egypt has constructed a prototype Kibble balance that can measure gram-level masses with 0.01% relative uncertainty. Through the construction of this prototype, the challenges can be studied and addressed to overcome the weaknesses of NIS’s prototype. This study presents the design and construction of the prototype Kibble balance. It also focuses on the design and performance of the magnetic system, which is a crucial element of the Kibble balance. Analytical modeling and finite element analysis were used to evaluate and improve the magnet system. Several other aspects were also discussed, including the yoke’s material and enhancing the magnetic profile within the air gap of the magnet system. Over a vertical distance of 30 mm inside the air gap, the magnetic flux density was found to be 0.3 T, and the uniformity was found to be 8 x 10 -5

Application of Statistical Design to Optimize the Preparation of Barium Titanate Nanopowders via Oxalate Precursor Method

Nanocrystalline barium titanate (BaTiO3) powders have been synthesized by oxalate precursor method. Statistical design (Box-Behnken) is used to study the effect of main three parameters: calcination temperature (800-1200 °C), calcination time (0.5-4 hrs), and oxalic acid mole ratio (0.5-1.5) related to barium and titanium added at constant Ba/Ti mole ratio 1 on the formation of BT powders. Barium titanate particles were characterized using X-ray diffraction (XRD), and scanning electron microscope (SEM). The statistical design showed that conversion of barium titanate increases by decreasing the oxalic acid mole ratio and decreasing the calcination temperature and calcination time. XRD showed that single phase of barium titanate is formed at calcination temperature starting from 800 °C, oxalic acid mole ratio 0.5 and calcination time 2.25 hrs. The average crystallite sizes at different conditions are in the range between 36 to 91 nm. SEM micrographs showed that the produced pure BT nanopowders were formed in the tetragonal structure shape

Enhancement of TiO2 nanoparticle properties and efficiency of dye-sensitized solar cells using modifiers

A low-temperature hydrothermal process developed to synthesizes titania nanoparticles with controlled size. We investigate the effects of modifier substances, urea, on surface chemistry of titania (TiO) nanopowder and its applications in dye-sensitized solar cells (DSSCs). Treating the nanoparticles with a modifier solution changes its morphology, which allows the TiO nanoparticles to exhibit properties that differ from untreated TiO nanoparticles. The obtained TiO nanoparticle electrodes characterized by XRD, SEM, TEM/HRTEM, UV-VIS Spectroscopy and FTIR. Experimental results indicate that the effect of bulk traps and the surface states within the TiO nanoparticle films using modifiers enhances the efficiency in DSSCs. Under 100-mW cm simulated sunlight, the titania nanoparticles DSSC showed solar energy conversion efficiency = 4.6 %, with V = 0.74 V, J = 9.7324 mA cm, and fill factor = 71.35

Enhancement of TiO2 nanoparticle properties and efficiency of dye-sensitized solar cells using modifiers

A low-temperature hydrothermal process developed to synthesizes titania nanoparticles with controlled size. We investigate the effects of modifier substances, urea, on surface chemistry of titania (TiO) nanopowder and its applications in dye-sensitized solar cells (DSSCs). Treating the nanoparticles with a modifier solution changes its morphology, which allows the TiO nanoparticles to exhibit properties that differ from untreated TiO nanoparticles. The obtained TiO nanoparticle electrodes characterized by XRD, SEM, TEM/HRTEM, UV-VIS Spectroscopy and FTIR. Experimental results indicate that the effect of bulk traps and the surface states within the TiO nanoparticle films using modifiers enhances the efficiency in DSSCs. Under 100-mW cm simulated sunlight, the titania nanoparticles DSSC showed solar energy conversion efficiency = 4.6 %, with V = 0.74 V, J = 9.7324 mA cm, and fill factor = 71.35

Magnetic field and internal heat generation effects on the free convection in a rectangular cavity filled with a porous medium saturated with Cu–water nanofluid

The present study investigates the effect of magnetic field and internal heat generation on the free convection flow in a rectangular cavity. Here, the cavity is filled with a porous medium saturated with Cupper Cu–water nanofluid. The governing equations are transformed into dimensionless form in stream function and solved numerically using finite difference method. The computations were carried out for a wide range of the Hartmann number, solid volume fraction and magnetic field parameter. Results have been presented in terms of the isotherms, streamlines, average Nusselt number, velocity and temperature profiles. The obtained results are compared with the previous published work and it showed a good agreement. It is found that the average Nusselt number decreases as the Hartmann number or the solid volume fraction increases, while the opposite behavior occurs with the increase in magnetic field inclination angle. Moreover, the increase in the Hartmann number leads to decrease the maximum value of stream function, while it enhances the maximum temperature

Controlling the microstructure and properties of titania nanopowders for high efficiency dye sensitized solar cells

(a) A highly ordered, vertically oriented TiO2 nanorods compared with TiO2 nanopaticles and (b) Dye sensitized solar cell fabricated using sealing technique. [Display omitted] ► TiO2 nanorods particles size of 3–5nm was synthesized hydrothermally at 100°C. ► SBET was 78.14m2/g and the band gap energy was 3.2eV. ► (Jsc) and (Voc) of the DSSC were in the range 10.84–13.23mAcm−2 and 0.71–0.78V. ► Conversion efficiency of DSSCs was 7.2%. ► IPCE analyses of the DSSC showed two peaks, at ∼350 and 520nm. A low temperature hydrothermal process have been developed to synthesize titania nanorods (NRs) and nanoparticles (NPs) with controlled size for dye sensitized solar cells (DSSCs). Effect of calcination temperature on the performance of TiO2 nanoparticles for solar cells was investigated and discussed. The crystallite size and the relative crystallinity of the anatase phase were increased with increasing the calcination temperature. The structures and morphologies of both (TiO2 nanorods and nanoparticles) were characterized using XRD, SEM, TEM/HRTEM, UV–vis Spectroscopy, FTIR and BET specific surface area (SBET) as well as pore-size distribution by BJH. The size of the titania nanorods was 6.7nm width and 22nm length while it was 13nm for nanoparticles. Efficiency of dye-sensitized solar cells (DSSCs) fabricated with oriented TiO2 nanorods was reported to be more superior compared to DSSC based on mesoporous TiO2 nanoparticles due to their high surface area, hierarchically mesoporous structures, low charge recombination and fast electron-transfer rate. With increasing calcination temperature of the prepared nanopowders, the light-electricity conversion efficiency (η) decreased. The efficiency of the assembly solar cells was decreased due to the agglomeration of the particles and difficulty of electron movement. The power efficiency was enhanced from 1.7% for TiO2 nanoparticles cells at hydrothermally temperature 500°C and 5.2% for TiO2 nanoparticles cells at hydrothermally temperature 100°C to 7.2% for TiO2 nanorods cells under AM1.5 illumination (100mWcm−2)