Thermal stability, structural and optical properties of rice husk sillica borotellurite glasses containing MnO2

The quaternary glass system {[(TeO2)0.7(B2O3)0.3]0.8[SiO2]0.2}1-x{MnO2}x where x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05 molar fraction was prepared by melt quenching technique. The amorphous nature of the glass is confirmed by X-ray diffraction patterns and Scanning Electron Microscopy(SEM). The prepared glass samples had also been characterized by Differential Scanning Calorimetry(DSC). The glass transition(Tg), onset glass transition(To), crystallization(Tc) and melting temperature(Tm) values were measured from DSC thermo-gram. Results from DSC indicate good thermal stability and low value of fragility (F) of the prepared glass samples. Thermal stability(Ts), Hurby parameter(Kgl), fragility(F) and activation energy(Ea) were calculated for every glass composition. It is observed that the optical band gap decreases with the concentration of MnO2. On the other hand, the refractive index(n) is observed to increase as the concentration of MnO2 increases. Fourier Transform Infrared (FTIR) spectroscopy has been done to identify the functional group in glass sample

Effect of Co3O4 doping and sintering temperature on optical energy band gap properties in Zn-Bi-Ti-O varistor ceramics

It is necessary to investigate the electronic states of ceramic based ZnO vasristor and effect of doped impurities at different concentration. Band gap (Eg) of the ceramic (99-x) mol% ZnO+0.5 mol% Bi2O3+0.5 mol% TiO2+ xCo3O4 where x = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples were prepared via solid-state route and sintered at the sintering temperature at 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of Co3O4, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.368 ± 0.002 and 2.352 ± 0.001 eV at 0.8 mol% Co3O4 for 45 and 90 min sintering time; respectively. XRD analysis indicates that two main phases existed at all concentrations which are ZnO and secondary phases, Bi12TiO20, Zn2Ti3O8, ZnCo2O4 and Co3Ti3O. Relative density decreases with the addition of Co3O4 compared to that of undoped at all doping level. When Co3O4 is added in the ceramics, relative density increases with the increase of doping level at both 45 and 90 min sintering time. The variation of sintering temperatures and XRD findings of steepness factor are correlated with the UV-Vis spectrophotometer results of based ZnO varistor doped with Co3O4 due to the growth of interface states

Shielding features of concrete types containing sepiolite mineral: comprehensive study on experimental, XCOM and MCNPX results

Natural sepiolite mineral is a naturally occurring clay form belonging to a part of layered silicate. Because of its advantages such as low production cost, light-weight and convenient, it may be selected as an alternative shielding material to others. Radiation shielding performances of some concretes to sepiolite and B4C addictive have been researched reported in a wide energy region of 0.08–1.333 MeV using experimental data, MCNP and XCOM. The simulated data obtained by MCNPX are discussed and compared with the experimental results as well as with the XCOM results. The simulations match the experiments very well except for S3 sample. From the measurement, the maximum gamma-ray attenuation was detected in the concrete specimen with 10% sepiolite (S1) while the minimum attenuation of gamma-ray was noted in the concrete specimen with 30% sepiolite (S3). The addition of sepiolite mineral to concretes may be an alternative option that can be used in several radiation protection applications

Enhancement of non-ohmic properties of CoO DopeD ZnO varistor ceramics using soda lime silica (SLS) glass

ZnO-SLS-CoO (ZSC) based varistor ceramics were prepared at a high sintering temperature of 1100 ºC via the conventional solid-state method. The effect of SLS glass on the electrical properties was studied at the different concentration of SLS glass ranging from 0.5 mol% to 2 mol%. Scanning electron microscopy (SEM) and X-ray diffractometer (XRD) were used to examine microstructure and crystal structure of the glass phase based ZSC varistor. For the electrical characteristics, the source measuring unit was used. The result shows that SiO2 as the major chemical compound found in the SLS glass that responsible for controlling the ZnO grain growth. When the concentration of SLS glass higher than 1 mol%, the dominant peak of ZnO was found in XRD pattern, which is the primary phase whereas the additional peak belongs to Zn2SiO4 as the secondary phase. ZSC varistor ceramics with 2 mol% of SLS glass possessed the best electrical properties with the highest nonlinear coefficient α at 4.38 and the lowest leakage current. The increasing value of α could be due to the increase in oxygen vacancies that eventually contributes to the increase of Schottky barrier formation

Study on the Morphology Stability of TiO2 Nanotube Arrays towards Temperature as a Potential Toxic Gas Sensor

AbstractTiO2 nanotube arrays were prepared by electrochemical anodization of titanium foil in mixed electrolyte solution of NH4F, water, and glycerol. The anodized TiO2 nanotube arrays were calcined at various temperatures and characterized using scanning electron microscope to study the morphology transformation. The results show that at low calcination temperature (300̊C) highly ordered TiO2 nanotube arrays are observed and remained up to 500̊C. At 700̊C, TiO2 nanotube arrays are completely destroyed and transformed to irregular shaped particle

Study of the elastic properties of (PbO)x(P2O5)1 − x lead phosphate glass using an ultrasonic technique

Fabrication of a series of binary (PbO)x(P2O5)1−x lead phosphate glasses with various mole fractions (x = 0.1 to 0.6) was carried out using a conventional melt-quenching method. The glass density was measured by using Archimedes principle. The ultrasonic wave velocities (Vl and Vt) of the glasses were determined at room temperature by using a nondestructive test: the digital signal processing technique of the Ultrasonic Data Acquisition System (Matec 8020, Matec Instruments, USA). The experimental data for the wave velocities and densities were then used to determine the elastic properties in each series of lead phosphate glass systems: the longitudinal, shear, bulk and Young's moduli; Poisson's ratio; and the Debye temperature. Based on the results obtained, the longitudinal, shear, bulk and Young's moduli of the glasses increased with the addition of PbO content. The Poisson's ratio obtained remains almost constant, while the Debye temperature shows a continuous decrease with the addition of PbO content

Effect of Co3O4 doping on nonlinear coefficient in Zn-Bi-Ti-O varistor ceramics

In the ZnO based varistor, the improvement of nonlinear coefficient (α) and prevention of evaporation of Bi2O3 during heat treatments can be achieved by the addition of MnO2 or Co3O4. In this conjunction, it is proper to see the effect of these additives at different low mol percentage and sintering conditions to nonlinear coefficient improvement of the varistor ceramics. In this paper, the investigation regarding to the α variation of Co3O4 doping on ZnO-Bi2O3-TiO2 system is discussed. Here, the crystalline phases were identified by an XRD (PANalytical (Philips) XPert Pro PW3040/60) with CuKα radiation and the data were analyzed by using XPert High Score software. The density of varistor ceramics was measured by the geometrical method. The current-voltage characteristics of the varistor ceramics were evaluated. The average grain size (d) was determined by lineal intercept method. The α of ZnO doped with 0.5 mol% of Bi2O3, 0.5 mol% of TiO2 and x mol% of Co3O4 was calculated from data analysis of current-voltage characteristics obtained through a Source Measure Unit (Keithley 236). The calculation of α is done by using Origin Pro8.0 software. The value of α at low concentration at 1170 °C has the value 5.36 and 3 at 45 and 90 min sintering time, respectively, and then decreases to 4.99 and 2.98 at 0.8 mol% Co3O4 concentrations. When the amount of dopant is increased then the value of α increase up to 0.4 mol% and then the value are slightly dropped after further addition. The addition of Co3O4 dopant in Zn-Bi-Ti oxide ceramics sintered at 45 minutes cause the value of α to increase up to 0.4 mol% and decrease after further addition

Effects of particle size on the dielectric, mechanical, and thermal properties of recycled borosilicate glass-filled PTFE microwave substrates

Low dielectric loss and low-cost recycled borosilicate (BRS) glass-reinforced polytetrafluoroethylene (PTFE) composites were fabricated for microwave substrate applications. The composites were prepared through a dry powder processing technique by dispersing different micron sizes (25 µm, 45 µm, 63 µm, 90 µm, and 106 µm) of the recycled BRS filler in the PTFE matrix. The effect of the filler sizes on the composites’ thermal, mechanical, and dielectric properties was studied. The dielectric properties of the composites were characterised in the frequency range of 1–12 GHz using an open-ended coaxial probe (OCP) connected to a vector network analyser (VNA). XRD patterns confirmed the phase formation of PTFE and recycled BRS glass. The scanning electron microscope also showed good filler dispersion at larger filler particle sizes. In addition, the composites’ coefficient of thermal expansion and tensile strength decreased from 12.93 MPa and 64.86 ppm/°C to 7.12 MPa and 55.77 ppm/°C when the filler size is reduced from 106 μm to 25 μm. However, moisture absorption and density of the composites increased from 0.01% and 2.17 g/cm3 to 0.04% and 2.21 g/cm3. The decrement in filler size from 106 μm to 25 μm also increased the mean dielectric constant and loss tangent of the composites from 2.07 and 0.0010 to 2.18 and 0.0011, respectively, while it reduced the mean signal transmission speed from 2.088 × 108 m/s to 2.031 × 108 m/s. The presented results showed that PTFE/recycled BRS composite exhibited comparable characteristics with commercial high-frequency laminates

Investigation of shielding parameters of some boron containing resources for gamma ray and fast neutron

Mass attenuation coefficient (μt) of some boron containing resources in China were investigated in the paper at 0.001–20 MeV through XCOM and Geant4. What’s more, half value thickness layer (HVL), mean free path (MFP), effective atomic number (Zeff) and electron density (Ne) were calculated. In addition, fast neutron removal cross sections of these resources were calculated by partial density method. It has been found that Boron bearing iron concentrate has the maximum μt, Zeff Ne and ∑R, and its HVL and MFP are lowest. The investigation would be useful for potential application of the boron containing resources in the field of neutron and gamma ray shielding materials

Effect of bismuth in lead germanate glass system on shielding properties for development of gamma-rays shielding materials

In this study, the shielding properties of bismuth lead germanate (BPG) glass system in composition x(Bi2O3)40-x(PbO)60(GeO2) where x = 0 to 40 mol% have been investigated. The shielding parameters, mass attenuation coefficients(µ/ρ), mean free path (MFP) and half value layer (HVL) values have been computed using WinXCom program and variation of shielding parameters of the BPG glasses are discussed for the effect of photon energy and Bi2O3 addition into the glasses. The replacement of PbO by Bi2O3 causes an increase in mass attenuation coefficient, while the MFP and HVL values were decreased. The investigation would be very useful for shielding applications in nuclear technologies