الفهرس 
AcknowledgmentOnly 14 pages are availabe for public view
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Abstract
This thesis is dedicated to investigate the structural role of chromium sulfate and gadolinium oxide in biocompatible borate glass-ceramics. Two series of modified borate glass with chemical formulas, xCr2(SO4)3-(60-x)B2O3-15CaO-15Na2O-10P2O5 mol% and xGd2O3-(23.5-x)CaO-42.7B2O3-5SrO-28Na2O-2.8P2O5 mol% have been prepared by traditional melt process and investigated using various structural methodologies. In the first series of glasses, Cr2(SO4)3 was added at the expense of B2O3 in the range x = 0 to x = 35 mol%. In the second series, the concentrations 0, 0.1, 0.2, 0.3, 0.4, and 0.5 mol% of CaO were replaced by Gd2O3 content.Understanding and interpreting data based on structural changes in the studied glasses was extensively carried out. The results are discussed in light of density, molar volume, packing density, and other physical parameters of glasses. Comprehensive structural techniques, including X-ray diffraction (XRD), high-resolution scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray analyzer (EDX), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy have been used to investigate the microstructure of the studied glasses. The obtained results have been summarized as follows:In the first series of glasses, xCr2(SO4)3-(60-x)B2O3-15CaO-15Na2O-10P2O5 glasses (0 ≤ x ≤ 35 mol%), XRD patterns of glass samples with lower concentrations of Cr2(SO4)3 (x ≤ 2 mol%) reveal a dominance of the amorphous structure within the compositional range. While glasses with higher Cr2(SO4)3 contents (x = 5–35 mol%) are characterized by the formation of specific polycrystalline phases within the glass network. That is, the amorphous nature of the glasses converts into apolycrystalline as a result of the introduction of Cr2(SO4)3 into the glass matrix. The presence of Cr2(SO4)3 affects the glass network, acting as a glass modifier at low concentrations (≤ 5 mol%) and a glass former at higher content.Data based on FTIR absorption support the presence of BO3, BO4, SO4, and CrO4 functional groups which were randomly distributed within the main borate network. The fraction B4 of four-coordinated atoms obtained from IR spectra increases with increasing Cr2(SO4)3 content, indicating that the formation of BO4, SO4, and CrO4 functional groups is increased. Besides, the density and molar volume of the studied samples were estimated and correlated with additional physical parameters. Based on the measured density, the concentration of ions, field strength (F), and inter-nuclear distance (ri) are calculated. It was concluded that the increase in Cr and S content leads to a decrease in the inter-nuclear distance which agrees with an increase in field strength and Vicker’s micro-hardness number of the investigated glasses. The bioactivity behavior of the final product samples was evaluated in vitro test. It is known that the as-obtained glasses containing low content of Cr2(SO4)3 (x < 5 mol%) possess an amorphous structure that delays the formation of bioactive phases in the host borate matrix. This problem has been solved by treating the glass thermally. In such a situation, calcium phosphate, and calcium borate phases are produced. These well-formed phases play the role of good bioactivity of the studied materials. The effect of the soaking time of glass samples containing apatite in simulated body fluid (SBF) on the final phase has been studied. The results indicated that soaking for an appropriate time resulted in the transformation of the composition of crystalline apatite into the hydroxyapatite phase. It was concluded that the final produced samples of borate glass are promising bioactive materials that can be used for biomedical applications.In the second series of glasses, xGd2O3-(23.5-x)CaO-42.7B2O3-26Na2O-5SrO-2.8P2O5 (0≤ x ≤ 0.5 mol%) glasses, XRD diffraction patterns confirm the amorphous nature of the as-prepared glass samples. Some physical properties such as the density 〖(d〗_s), Gd3+ ions concentration (N), packing density (Pd), oxygen packing density (OPD), Vickers’s hardness (HV), and field strength (F) of the synthesized samples were calculated and they increased with increasing Gd2O3 contents. While the molar volume (Vm), free volume (Vf), polaron radius (rp), average boron-boron distance (dB–B), and inter-nuclear distance (ri) were decreased. It is concluded from Raman and FTIR spectra that Gd2O3 plays a dual role. X-ray diffraction patterns of the final product of heat-treated glass-ceramics (at 600 ºC for 12 h) reveal that calcium phosphate (Ca3(PO4)2), and calcium borate (CaB2O4) are the main well-formed crystalline phases. In addition, increasing Gd2O3concentrations enhances the growth of the crystalline phase, where Gd2O3 acts as a crystalline agent. The presence of these crystalline phases showed a remarkable effect on the bioactive properties of the glass ceramics. In vitro tests, some of the XRD diffraction peaks of the reaction products decrease in intensity after soaking in SBF for different days. In comparison to SBF, the reaction between glass and the K2HPO4 solution is substantially faster. Results from IR, X-ray, and SEM techniques revealed that the prepared glass samples containing gadolinium oxide (Gd2O3) approve the formation of the hydroxyapatite on the glass powder surface. These results indicate that all prepared glass samples exhibit good bioactivity behavior, making them very suitable for various biomedical applications.