Dielectric, elastic and optical properties of 80TeO2-(20-x) MnO2-xFe2O3 and 30Li2O-4MoO3-(66-x)TeO2-xV2O5 mixed oxide tellurite glasses in the conductivity anomaly region / Rosdiyana Hasham @ Hisam

In this study, two series of mixed oxide tellurite based glasses with composition 80TeO2-(20-x)MnO2-xFe2O3 (x = 5 mol% to 20 mol%) and 30Li2O-4MoO3-(66-x)TeO2-xV2O5 (x = 0.2–1.2 mol%) were prepared using melt-quenching method to investigate their dielectric, AC conductivity, elastic and optical properties. For the 80TeO2-(20-x)MnO2- xFe2O3 glass samples, the dielectric constant showed strong variation with Fe2O3 at a frequency ≥ 10 kHz, where ε′ decreased to a minimum value at x = 10 mol% before increasing for x >10%. The decrease in ε′ may be attributed to some form of hindrance effect on heavy dipoles caused by the mixed transition-ion effect (MTE). Meanwhile, variation of AC conductivity with Fe2O3 showed non-linear increase for x ≤ 10 mol% before dropping to a minimum at 15 mol% Fe2O3. This result is attributed to Anderson localization because of the disorder in the glass system. On the other hand, DC conductivity for the same glass system showed a strong increase for x ≤ 10 mol% Fe2O3 before reaching a saddle-like behavior between 10 mol % ≤ x ≤ 15 mol%, followed by a large increase for x > 15 mol%. Independent longitudinal modulus (CL), shear modulus (μ) and bulk modulus (Ke) showed increased values for x ≤ 10 mol% with an anomalous drop at x = 15 mol% Fe2O3, followed by a large increase at x > 15 mol%. The anomalous region between 10 mol% ≤ x ≤ 15 mol% coincided with DC conductivity saddle-like region and is suggested to be related to the MTE. Meanwhile, in the same region, optical band gap (Eopt) exhibited a maxima, whereas refractive index showed a minima, thereby indicating a variation in polarizability due to changes in concentration of bridging and non-bridging oxygens. For the 30Li2O-4MoO3-(66-x) TeO2-xV2O5 glasses, the variation of AC conductivity with V2O5 showed This thesis presents a simulation study on parameter estimation for binary and multinomial logistic regression, and the extension of the clustering partitioning strategy for goodness-of-fit test to multinomial logistic regression model. The motivation behind this study is influenced by two main factors. Firstly, parameter estimation is often sensitive to sample size and types of data. Simulation studies are useful to assess and confirm the effects of parameter estimation for binary and multinomial logistic regression under various conditions. The first phase of this study covers the effect of different types of covariate, distributions and sample size on parameter estimation for binary and multinomial logistic regression model. Data were simulated for different sample sizes, types of covariate (continuous, count, categorical) and distributions (normal or skewed for continuous variable). The simulation results show that the effect of skewed and categorical covariate reduces as sample size increases. The parameter estimates for normal distribution covariate apparently are less affected by sample size. For multinomial logistic regression model with a single covariate, a sample size of at least 300 is required to obtain unbiased estimates when the covariate is positively skewed or is a categorical covariate. A much larger sample size is required when covariates are 21 22 a non-linear increase for x ≤ 0.6 mol% before decreasing to a minimum at 0.8 mol% V2O5

Anomalous dielectric constant and AC conductivity in mixed transition-metal-ion xFe2O3-(20 - x)MnO2-80TeO2 glass system

Glasses with xFe2O3–(20−x)MnO2–80TeO2 (x=2, 5, 10, 15, and 20 mol%) composition were prepared by meltquenching technique to investigate the effects of mixed-transition metal ion Fe2 +/3 +//Mn3 +/4 + on AC conductivity and dielectric properties using impedance spectroscopy. Dielectric constant showed strong variation with Fe2O3 at a frequency ≥10 kHz, where έ decreased to a minimum value at x =10 mol% before increasing for x> 10%. The decrease in έ may be attributed to some form of hindrance effect on heavy dipoles caused by the mixed transition-ion effect (MTE). Meanwhile, variation of AC conductivity with Fe2O3 showed non-linear increase for x ≤ 10 mol% before dropping to a minimum at 15 mol% Fe2O3. This result was attributed to Anderson localization because of the disorder in the glass system. Conductivity analysis showed that the conduction mechanism at the dispersion region for x = 2 mol% followed the correlated barrier hopping (CBH) model, while the mechanism transformed to the overlapping large polaron tunnelling (OLPT) model at higher Fe2O3, content (x > 2 mol%). The electric modulus of the investigated samples showed asymmetric peak of the imaginary part of electric modulus (M¢¢), which reflected a non-Debye type relaxation

Parameters for digital neutron radiography at triga mark II research reactor of Malaysian nuclear agency

Neutron radiography has been widely employed in nondestructive testing technique to detect the structural nature of internal defects of optically opaque materials. For many years, conventional neutron imaging technique has been carried out using analogue technology which uses film as means for imaging. In making transition from analogue to digital technology, several parameters have to be optimized. Beam size and neutron flux have been identified as two principal. parameters to develop digital neutron radiography. The parameters will be considered as a point to get a neutron beam to suit the scintillator size of detector and produced high quality image. Safety of the equipment was also important to protect the electronic component of the detector from damaged. In this study, a cooled charge couple device (CCD) camera system was used and a shielding is adopted to protect the CCD camera from unnecessary radiation. Therefore the thickness estimation of shielding was obtained and verified by gamma ray dose mapping. The neutron beam size has been modified by attaching a simple collimator beam plug to the neutron radiography 2 (NUR-2) beamport to accommodate 5 em x 6 ern dimension of the scintillator screen placed in the CCD camera. With the collimator beam plug attached, the neutron beam effective diameter is reduced to 7.2 em from 15.8 em which effectively covers the scintillator area. The thermal neutron flux through the collimator beam plug at CCD camera location was 2.674 x 10 5 ncm-2s-1. The neutron flux obtained is within the acceptable levels for the CCD camera requirement. Meanwhile the gamma ray dose with CCD camera shielding was less than 30 mfiyh' . The gamma ray dose mapping indicates the shielding was effective in protecting the electronic components from damaged. These experimental results consistent with the result of the analysis on the digitized the radiographic image produced using a conventional techniqu

Development of Novel Transparent Radiation Shielding Glasses by BaO Doping in Waste Soda Lime Silica (SLS) Glass

In the current study, BaO was doped in Bi2O3-ZnO-B2O3-SLS glass to develop lead-free radiation shielding glasses and to solve the dark brown of bismuth glass. The melt-quenching method was utilized to fabricate (x) BaO (1 − x)[0.3 ZnO 0.2 Bi2O3 0.2 B2O3 0.3 SLS] (where x are 0.01, 0.02, 0.03, 0.04, and 0.05 mol) at 1200 °C. Soda lime silica glass waste (SLS), which is mostly composed of 74.1% SiO2, was used to obtain SiO2. The mass attenuation coefficient (μm) was investigated utilizing X-ray fluorescence (XRF) at 16.61, 17.74, 21.17, and 25.27 keV and narrow beam geometry at 59.54, 662, and 1333 keV. Moreover, the other parameters related to gamma ray shielding properties such as half-value layer (HVL), mean free path (MFP), and effective atomic number (Zeff) were computed depending on μm values. The results indicated that HVL and MFP decreased, whereas μm increased with an increase in BaO concentration. According to these results, it can be concluded that BaO doped in Bi2O3-ZnO-B2O3-SLS glass is a nontoxic, transparent to visible light, and a good shielding material against radiation

Development of novel transparent radiation shielding glasses by BaO doping in waste soda lime silica (SLS) glass

In the current study, BaO was doped in Bi2O3-ZnO-B2O3-SLS glass to develop lead-free radiation shielding glasses and to solve the dark brown of bismuth glass. The melt-quenching method was utilized to fabricate (x) BaO (1 − x)[0.3 ZnO 0.2 Bi2O3 0.2 B2O3 0.3 SLS] (where x are 0.01, 0.02, 0.03, 0.04, and 0.05 mol) at 1200 °C. Soda lime silica glass waste (SLS), which is mostly composed of 74.1% SiO2, was used to obtain SiO2. The mass attenuation coefficient (μm) was investigated utilizing X-ray fluorescence (XRF) at 16.61, 17.74, 21.17, and 25.27 keV and narrow beam geometry at 59.54, 662, and 1333 keV. Moreover, the other parameters related to gamma ray shielding properties such as half-value layer (HVL), mean free path (MFP), and effective atomic number (Z e f f) were computed depending on μm values. The results indicated that HVL and MFP decreased, whereas μm increased with an increase in BaO concentration. According to these results, it can be concluded that BaO doped in Bi2O3-ZnO-B2O3-SLS glass is a nontoxic, transparent to visible light, and a good shielding material against radiation

Investigation of optical properties and radioactive attenuation parameters of doped tungsten oxide soda lime silica SLS waste glass

The optical properties and radioactive attenuation parameters of doped tungsten oxide soda-lime-silica (SLS) waste glass were investigated in the current work. A novel series of lead-free transparent glass samples were manufactured with the possibility of developing radiation-absorbing glass shielding materials. The glass composition is WO3–Bi2O3–ZnO–B2O3-SLS. A new approach was employed in the utilization of soda-lime-silica (SLS) glass as an alternative for pure silicon dioxide having 74.1% of SiO2 and other elements in it. The optical properties were investigated with the help of a UV–Visible Spectrophotometer. The results for the optical properties showed that when WO3 content is increased in the glass structure, the Urbach energy ΔE and refractive index n, increase from 0.337 to 0.431 and 2.84 to 2.94 respectively, the optical basicity Λ also increase with the increase in WO3 while the energy optical band gap Eopt registered a decrease. The metallization criterion (M) confirmed that the current glass samples are nonmetallic (insulator) because Rm/Vm < 1 which is confirmed in the condensed matter theory in the Lorentz–Lorenz equations. Moreover, the theoretical radiation shielding parameter results indicate that the linear attenuation coefficient μ and Zeff were increased with an increase in WO3. It can be seen also that the relationship between the μ and HVL is an inverse one; larger values of μ result in lesser thickness of the HVL. Whereas, as the WO3 concentration increases, the half-value layer HVL decreases. The results of this study demonstrate that the glass samples are harmless, transparent to visible light, and effective radiation shielding materials

The Effect of WO₃-Doped Soda Lime Silica SLS Waste Glass to Develop Lead-Free Glass as a Shielding Material against Radiation

The current study aims to enhance the efficiency of lead-free glass as a shielding material against radiation, solve the problem of the dark brown of bismuth glass, and reduce the accumulation of waste glass disposed in landfills by using soda-lime-silica SLS glass waste. The melt-quenching method was utilized to fabricate (WO3)x [(Bi2O3)0.2 (ZnO)0.3 (B2O3)0.2 (SLS)0.3]1−x at 1200 °C, where x = (0, 0.01, 0.02, 0.03, 0.04, and 0.05 mol). Soda lime silica SLS glass waste, which is mostly composed of 74.1 % SiO2, was used to obtain SiO2. Radiation Attenuation parameters were investigated using narrow-beam geometry and X-ray fluorescence (XRF). Furthermore, the parameters related to radiation shielding were calculated. The results showed that when WO3 concentration was increased, the half-value layer was reduced, whereas the μ increased. It could be concluded that WBiBZn-SLS glass is a good shielding material against radiation, nontoxic, and transparent to visible light

Physical, structural, and Raman spectroscopic traits of neodymium-doped lead Oxyfluoride zinc phosphate glass

Nd3+ with composition of (60 - x) P2O5 - 10ZnO - 30PbF2 - (x) Nd2O3 where (0.0 ≤ x ≤ 2.0 mol %) was prepared using a melt-quenching approach to the development of transparent glasses. These glasses have been confirmed to be an amorphous structure through XRD analysis. The glass density, molar volume and ionic packing density were obtained in the range of 3.978- 4.157 g cm-3, 41.949 - 41.073 cm3 mol-1 and 0.614-0.624, respectively. Using Fourier Transform Infrared (FTIR) and Raman Spectroscopy, the chemical functional groups and biomolecules of samples were characterised. The FTIR spectra revealed six main bands assigned to P-O, P-O-P, P=O, (PO3)2- and hydroxyl groups (O-H), while Raman shift detected five symmetric and asymmetric bands attributed to P-O-P bonds in Q1 units, (PO4)3- bonds in Q0 units, (PO3)2- bonds in Q1 units, (PO2)- bonds in Q2 units and P=O bonds in Q3 units. It is believed that the proposed oxyfluoride glasses may be useful and suitable applicant to lasing materials and sensors sensitivity