الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 197 |  |  |
| | | from | 197 | | |
Abstract
”Ternary silver phosphate glasses with the general formula xAl2O3.(40-x)Ag2O.60P2O5 and xFe2O3.(40-x)Ag2O.60P2O5 have been studied over a wide range of x= 0 to 20 mol percent. For the development of low-Tg and to contribute in the stability of the phosphate glass structure, Al2O3 and Fe2O3 are substituted for Ag2O. The current research investigates the effect of both Al2O3 and Fe2O3 on the structure and physical properties of phosphate glass network. X-ray Diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Fourior transfrom infrared (FTIR) spectroscopies, and Vicker Hardness were used to analyze these glasses. In addition, the dissolution behavior and the shielding parameters of the investigated glasses were studied. The ””former”” character of aluminum atoms increases as alumina content rises. This means that silver phosphate glasses network have a tendency to incorporate Al2O3 as a secondary glass formation. Furthermore, the addition of alumina results in the formation of new P-O-Al-O-P bonds as well as an increase in the quantity of Q2 and Q3 groups, showing phosphate glass network copolymerization in parallel. Increased concentrations of bridging oxygen atoms shared by Al and P atoms may favour the formation of P-O-Al units over through the creation of P-O-…. Ag+ bonds. As a result, increasing the concentration of P-O-Al bonds at the expense of P-O-…. Ag+ is thought to be the primary explanation for the formation of a stronger glass network in aluminum-containing glasses than in aluminum-free glasses. Because iron oxide can exist as both Fe (III) and Fe(II) ions, incorporating Fe2O3 into the modified phosphate glasses is more complicated. The valence state of iron is influenced by melting conditions, total iron concentration, and the presence of a reducing or oxidant in glass batches. In all cases, XRD patterns for the examined glasses reveal a broad diffraction hump, indicating the existence of an amorphous matrix. In glasses of 10 moll% Al2O3, SEM pictures reveal that the glass surface is clearly visible and contains some well-formed holes. When more Al2O3 is added, the morphology entirely changes. from x=5 mol percent to x=20 mol percent, grain size and pore size dropped as glass Al2O3 concentration increased. Further increases in aluminum content result in broken nanoparticles imbedded in the hosting matrices, which would reinforce the bond energy and increase the compactness of the structure. The EDX spectra indicated the presence of all elements in all samples. The existence of identified elements demonstrates that the targeted glass samples were successfully produced and are free of contamination from the crucible. With increasing Al2O3 content, the density and molar volume steadily decrease. This trend indicates that the developed units have a lower overall density and volume than binary silver phosphate glasses. One of the explanations the DROP in Vm could be due to a decrease in Vf. Electrical conductivity measurements revealed that as temperature increases, conductivity increases as well, leading to an increase in the mobility of Ag ions as charge carriers. Logσ373 drops by nearly two orders of magnitude (from -7.3 to -9.3) as Al2O3 concentration rises, whereas Ea rises (from 0.58 to 0.91 eV). It can be deduced that non-bridging oxygen ions in glasses can be changed into glasses with a more compact structure by substituting Al2O3 or Fe2O3 for Ag2O. As a result of the blocking action of Al2O3 and Fe2O3, the studied glasses exhibit a decreased conductivity. Ion mobility is limited as a result of these properties, and charge carriers must expend more energy to travel. The decrease in conductivity and rise in activation energy are primarily explained by this mechanism. The hardness of the glass that is free of aluminum oxide compared to those that contain Al2O3 increases as the content of Al2O3 or Fe2O3 increases. Aluminum silver phosphate glasses have a higher hardness than glass containing iron oxide. The increase in hardness that has been seen is linked to the stiffness of glass. These findings are in line with the NMR and IR findings, which showed that the addition of Al2O3 increased the bond energy between P - O and Al-O. As the Al2O3 content rises, Al ions gradually join the network as a network former, replacing some Ag ions, and thus non-bridging oxygen bonds may be transformed to bridging oxygens as P-O-Al links form. As a result, increasing the concentration of P-O-Al connections at the expense of P O-…Ag+ is thought to be the primary explanation for the creation of a stronger glass network in aluminum-containing glasses than in aluminum-free glasses. The dissolution rate varies with Al2O3 content, decreasing from approximately 1.6x10-4 g/cm2/min for glass that free of aluminum to less than 2.34x10-9 g/cm2/min for glasses containing 20 mol% Al2O3 which is 100 times less than the dissolution rate of window glass and 300 times lower than that of a barium fero, aluminoborate glass. The glass that free of aluminum is completely dissolved before 20 days in distilled water at 90 oC. The dissolution rate of aluminum silver phosphate glasses is higher than the glass containing iron oxide. The increase in the chemical durability is attributed to the change of chemical bonds in the vitreous state, as the weaker P-O^-Ag+ and P=O bonds are replaced easily by more chemically durable P–O–Al bonds which is confirmed by the using the NMR technique and FTIR studies. The increase in the O/P ratio inducts an increase in the Al/P ratio and, consequently, an increased number of covalent P–O–Al bonds, making the glass structure more shielding and more hydration resistant. The EDS analysis and the SEM micrographs from the samples surfaces of the investigated glasses before and after immersion in distilled water offered more insight into the chemical reactions causing the concentration of compositions change. There was slightly detectable difference in the morphology of glass samples that contain 15 and 20 mol% Al2O3, but the glass samples that free of aluminum and that contain 5 mol% Al2O3 were more heavily corded with small amounts of phosphorus were observed than 15 and 20 mol% Al2O3. The data obtained from EDS confirm the presence of all the elements forming the glass and prove that the dissolution of phosphorus decrease with increasing aluminum content. The attenuation coefficients in present glass samples with thicknesses up to 3 cm were investigated using gamma rays with energy ranging from 121.8 to 1407.9 keV. It was found that decreasing the Ag2O proportion has a negative impact on the mass attenuation coefficient values at low energy, which reduced as the aluminum content increased. On the other hand, at high energies, the mass attenuation coefficient values for the glass containing 20 mol% Al2O3 begin to exceed those of the binary glass. Therefore, the large quantity of Al2O3 increases the shielding capability at high energies. Photoelectric absorption (PE), Compton scattering (CS), and pair creation are three processes by which gamma radiation interacts with the glass sample, depending on the energy of the gamma photon and the atomic number (Z) of the sample (PP). The values of HVL for xAl2O3.(40-x)Ag2O.60P2O5 and xFe2O3.(40-x)Ag2O.60P2O5 are depending on the composition of the glass sample for low, moderate, and high photon energies. The values of HVL of the present glass systems were compared to that of various commercially available shielding glasses developed by the SCHOTT company and three kinds of concretes (ordinary, hematite–serpentine, and ilmenite–limonite concretes) reported by Bashter for specific energy ranges. With the exception of the RS-360 glass result in the 0.1–1 MeV medium energy range, all of the chosen glasses have lower HVL thicknesses than the RS-253 G18 glass sample and the concretes used in the comparison at all energies. In terms of photon shielding, the chosen glasses outperformed certain types of concrete and certain commercial glasses. In the energy range of 15 keV to 15 MeV, the energy dependent parameters (Zeff and EBF) were examined. In the middle energy zone, EBF values were found to be maximum due to the divergence of beam as well as multiple scatterings. There is a discontinuous variation in EBF with energy in the energy region around 0.04 and 0.09 MeV, a rise in the value of EBF was noticed in the photoelectric interaction zone. The initial rise is caused by silver’s X-ray absorption K-edges. The amplitude of the K-absorption peak for Ag is related to the silver content in the investigated glasses. EBF values are observed to increase with penetration depth. Furthermore, the EBF values for the produced samples are found to have a considerable influence on the chemical composition of the glass at lower energies. The prepared glass samples have been shown to have potential applications in radiation shielding and radiation sensing, as well as various other applications in health and industry.
”