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Structural Role of Cerium Oxide in Lead Silicate Glasses and Glass Ceramics

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Journal of Minerals and Materials Characterization and Engineering 2018年第3期6卷 438-447页

作者： gomaa el-damrawi Amal Behairy Physics Department Faculty of Science Mansoura University Mansoura Egypt The High Institute of Engineering and Technology New Damietta Damietta Egypt

Silicate glasses and glass ceramics in the system CeO2-PbO-SiO2 have been studied as a function of the structure factors R and K. The latter two factors are defined as: R = (CeO2 + PbO)/SiO2 and K = (SiO2/CeO2) molar ratios. In this glass, PbO is fixed at 50 mol% and CeO2 increases at the expense of SiO2. NMR investigations have revealed that increasing R which is accompanied with decreasing K leads to reasonable decrease in the shielding of silicon atoms. The chemical shift (δ) showed an increasing behavior due to increasing non-bridging oxygen atoms (NBO) in silicate network. It is evidenced that NBO in cerium free glass is much lower than that of glasses containing CeO2. Increasing R is clearly leading to higher chemical shift and higher NBO. This reflects that CeO2 has an effective structural role, since it would be consumed in all cases as an intermediate oxide. The main portions from CeO2 and PbO inter as glass modifiers which are consumed to form NBO atoms. A limited portion of CeO2 acts as glass former which consumed to form tetrahedral cerium containing NBO due to modification by PbO as a modifier oxide. Increasing R = [(CeO2 + PbO)/SiO2] from 1 to 2.34 leads to a frequent increase of NBO in the average glass network. FTIR spectroscopy of the glasses showed a clear shift of the main absorbance peak toward the low wavenumber with increasing R which confirms the increasing silicate units containing NBO atoms. XRD of the investigated materials revealed the presence of some nanostructures from cerium silicate crystalline phases. Formation of separated phases containing micro clusters is found to depend on NBO concentration, since NBO can facilitate process of phase separation. Majority of modifier are consumed to form NBO in the glass network and the rest are aggregated or separated to form silicate phase riches with cerium cations. In such case, some of silicon atoms are electrically compensated with both Pb and Ce cations.

关键词： Cerium in Glasses Crystalline Clusters NMR Feature Glass Ceramics

More Insight on Structure of New Binary Cerium Borate Glasses

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New Journal of Glass and Ceramics 2018年第1期8卷 12-21页

作者： gomaa el-damrawi Fawzeya Gharghar Rawya Ramadan Glass Research Group Physics Department Faculty of Science Mansoura University Mansoura Egypt Microwave and Dielectric Department Physics Division National Research Centre Giza Egypt

The structure of glasses in the system of xCeO2(100?-?x)B2O3, x = 30, 40, 50 mol% CeO2 has been explored for the first time by correlation between data obtained from XRD, FTIR and 11B NMR analyses. NMR spectroscopy andFTIR spectroscopy have confirmed that transformation rate of BO3 to BO4 groups is reduced by CeO2 *** concentration of Ce4-O-Ce4 is increased at the expense of both B4-O-Ce4 and B3-O-B4 linkages. Boron atoms are mainly coordinated with Ce4 sites as second neighbors due to increasing CeO4 species with further increase of CeO2 concentration. Increasing B4 fraction is considered due to forming of CeO4 with rate higher than that of BO4 units. The change of chemical shift of 11B nuclei upon exchanging B2O3 with CeO2 confirms that the central boron atoms would be coordinated with tetrahedral cerium atoms as second neighbors. The X-ray diffraction of cerium rich glass is clearly indicated that the formation of crystalline phases refers to CeO4, CeBO3and Ce(BO2)3 species.

关键词： Borate Cerium Former Units NMR Analysis

Structural Characterizations for Glass Ionomer Cement Doped with Transition Metal Phthalocyanines

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New Journal of Glass and Ceramics 2019年第4期9卷 67-79页

作者： gomaa el damrawi Amal Behairy Riham Atef Physics Department Faculty of Science Mansoura University Mansoura Egypt Basic Science Department The High Institute of Engineering and Technology New Damietta Egypt Chemical Engineering Department The High Institute of Engineering and Technology New Damietta Egypt.

Glass and Glass iomomer cement (GICs) based on a specific composition of cerium phosphate glass (40 CeO2-60P2O5) have been prepared. Effect of the doping type at a fixed doping concentration from metal-phthalocyanines (M-PCs) on material structure and morphologies has been carefully studied. The corresponding changes in the material structure were widely followed up by?31P MAS NMR, X-Ray diffraction and FTIR spectroscopy. The network structure of both base glass and GIC which all free from metal phthalocyanines has been confirmed to be amorphous. GIC doped with M-PCs has shown a more ordered structure. There were clear changes in the position and intensities of?31P NMR spectral peaks of glasses upon changing the dopant type. In all cases, a little concentration from M-Phthalocyanine (0.8 mol%) leads to changing the network structure from amorphous to a more ordered structure. Phosphate structural phases are evidenced to be formed upon addition of a fixed amount of M-PCs (Ga, Co, Fe). The morphologies of some selected samples were characterized by SEM. The micrographs have revealed that formulating of cerium phosphate powder of the amorphous glass with a polymeric acid successfully led to the formation of CePO4-H2O bundles phases. But formulation with GIC containing Co or Fe or Ga Phthalocyanine can simply form co-aligned linear slaps and elongated nanofibers which are consisted of hydrated and carbonated CePO4?a GaPO4, FePO4?or CoPO4?crystals. The structure of all doped materials has a lower crack length than that of base glass. This was discussed on bases of formation of more aligned and elongated tough-fibers in matrix of all doped materials. Such tough fibers have ability to withstand breaking stress via suppressing crack propagation.

关键词： Cerium Phosphate Metal Phthalocyanine Bundles Phases 31P NMR Spectros-copy

Effect of SrO on the Structure of Apatite and Wollastonite Phases of Na2O-CaO-SiO2-P2O5Glass System

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New Journal of Glass and Ceramics 2021年第2期11卷 45-56页

作者： gomaa el damrawi Rawya Mhammed Ramadan Mohamed el Baiomy Glass Research Group Physics Department Faculty of Science Mansoura University Mansoura Egypt Microwave Physics and Dielectrics Department Physics Research Division National Research Centre Cairo Egypt

Glasses in the system 24.5Na2O·24.5CaO·6P2O5·xSrO·(45-x)SiO2 have been studied in the composition region of x = 0 - 15 mol%. The as prepared glasses are transparent and have an amorphous network structure. On the otherhand, heat treated glasses are transformed to opaque white glass ceramic characterized by their highly crystalline network structure. Crystalline apatite (calcium phosphate, Ca3(PO4)2, wollastonite (calcium silicate, CaSiO3), and strontium calcium phosphate Ca2Sr(PO4)2 are the main well-formed cry

关键词： Structure Physical Properties Gasses Glass Ceramics

Structural Role of CeO2in the Modified Borate Glass-Ceramics

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New Journal of Glass and Ceramics 2021年第1期11卷 34-43页

作者： Nada elBaz gomaa el-damrawi Amr M. Abdelghany Glass Research Group Faculty of Science Physics Department Mansoura University Mansoura Egypt Spectroscopy Department Physics Division National Research Centre Giza Egypt

A new type of cerium borate glass-ceramic is prepared and studied. The microstructure and crystallization behaviors of the glass samples were investigated by X-ray diffraction (XRD), electron diffraction (ED), and 31P NMR spectroscopy. The microstructures of samples contain 2 are amorphous in nature. More addition of CeO2 transforms the glass to glass-ceramics without thermal annealing. The morphological change of the microstructure of these materials was followed by transmission electron microscopy (TEM). The obtained results have revealed that the addition of more than 0.8 mol% CeO2 can promote nucleation and crystallization routes that are combined with the establishment of diverse crystalline phases. Glasses with lower contents of CeO2showed no tendency to crystallization. The crystals of CeO2 containing glasses were spheroid like morphology that was assigned to the three-dimensional fast growth of the well-formed structural species in the boro-apatite phase. In addition, the cerium free glass is characterized by particle-like

关键词： Cerium Borate Glass Morphology Crystalline State Spheroid Species

¹¹B NMR Spectroscopy of Lead Borate Glasses: Additive Effect of Cerium Oxide

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New Journal of Glass and Ceramics 2016年第4期6卷 57-63页

作者： gomaa el-damrawi Fawzia Gharghar Rawia Ramadan Mohamed Aboelez Glass Research Group Physics Department Faculty of Science Mansoura University Mansoura Egypt Microwave and Dielectric Department Physics Division National Research Centre Giza Egypt Faculty of Engineering Monofya University Sheben Elkom Egypt

Glasses and glass ceramics in the system xCeO2·(50 - x)PbO·50B2O3 (0 ≤ x ≤ 50) have been studied, for the first time, by NMR and FTIR techniques. Effect of CeO2 substitution with PbO on NMR parameters has been discussed in terms of changing both boron and cerium coordination. The quantitative fraction of four coordinated boron (N4) has been simply determined from 11B NMR spectroscopy. On the other hand, the fraction of total tetrahedral structural units B4 (BO4 + PbO4 + CeO4) is obtained from FTIR spectral analysis. It is not possible to get the fraction of cerium oxide directly from the applied spectroscopic tools. Therefore, a simple approach is applied, for the first time, to determine CeO4 fraction by using the different criteria of both 11B NMR and FTIR spectroscopy. The fraction of B4 species is equal to N4, within the experimental error, of the same glasses in the composition region of up to 10 mol% CeO2. On the other hand, there is a clear difference between both N4 and B4 values in glasses of higher CeO2 content (>10 mol%). The related difference showed a linear increasing trend with increasing the content of CeO2 in the glass. This was discussed on the bases of structural role of CeO2 which acts as a glass former in the region >10 mol%, while, at lower concentration, it consumed as a glass modifier.

关键词： New Approach Cerium Oxide Boron Fraction

Morphological and Structural Investigations on Iron Borosilicate Glasses

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New Journal of Glass and Ceramics 2017年第2期7卷 13-21页

作者： gomaa el-damrawi Abdel Meguid Hassan Sammer el-Jadal Glass Research Group Physics Department Faculty of Science Mansoura University Mansoura Egypt

Borosilicate glasses and glass ceramics in the system 30Na2O-2Al2O3-25SiO2-xFe2O3(43-x)B2O3 (x = 0 - 20 mol%) have been prepared and studied by distinguished techniques. X-ray diffraction (XRD), transmission electron microscope (TEM), electron diffraction pattern (EDP) and SEM experiments are applied to explore the induced structural changes. Nanometer-sized species of polycrystalline structure are formed particularly in low Fe2O3 containing glasses. The size of the crystallites is found to depend on Fe2O3 concentrations. It is ranged from 10 to 33 nanometers. Structurally, these materials are suggested to contain different components, crystalline component and an interfacial component which situated between the crystallized domains. Presence of these components affects the atomic arrangement without short- or long-range order. An intermediate range ordered structure is dominant in glass ceramics of Fe2O3 2O3 concentration, since more disordered structure of lower size is present. These structural changes are found to be connected with the role of Fe2O3 and Na2O in glasses. Na2O is the strong glass modifier in the studied composition region, while Fe2O3 is consumed also as a modifier in composition of 2O3 is mainly dominant in the composition region of higher iron oxide concentration (8 - 20 mol%).

关键词： Borosilicate Morphology Glass Ordered Structure Clusters

Nuclear Magnetic Resonance and FTIR Structural Studies on Borosilicate Glasses Containing Iron Oxide

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New Journal of Glass and Ceramics 2016年第4期6卷 47-56页

作者： gomaa el-damrawi Abdel Meguid Hassan Rawia Ramadan Sammer el-Jadal Glass Research Group Physics Department Faculty of Science Mansoura University Mansoura Egypt Microwave and Dielectric Department National Research Center Dokki Giza Cairo Egypt

The structure of borosilicate glasses of composition 30Na2O-2Al2O3-25SiO2-xFe2O3 (43-x) B2O3 has been investigated in the composition range of 0.5 20 mol% Fe2O3. 27Al, 11B, 29 Si MAS NMR and FTIR spectroscopies have been used to measure the fraction of different structural species in the glasses. It is evidenced from NMR data that both sodium and Fe2O3 (in low region up to 7 mol%) are the main glass modifier. Structural determination for borosilicate glasses with a high content of (Fe2O3) was carried out by FTIR spectroscopy, where both 11B and 29Si MAS NMR are impossible because of the high quantities of paramagnetic iron (III) species present. NMR analysis was performed on borosilicate glasses containing up to 7 mol% Fe2O3 and the N4 values obtained by FTIR spectroscopy agree within error with the 11B NMR results of the same glass samples. Fe2O3 is a main glass modifier in the low-Fe2O3-content region (≤6 mol%). On other hand, it plays the role of glass former at higher content of Fe2O3. Increasing both N4 of boron tetrahedral units and chemical shift of silicon nuclei to reach maxima at 5 mol% Fe2O3 confirms the role of Fe2O3 as a glass modifier in the low composition region. On the other hand, fast decrease in N4 with further increasing Fe2O3 contents ≥6 mol%) is an evidence for iron oxide to inter the glass network as a network former.

关键词： NMR-FTIR-Spectroscopy-Borosilicate-Glasses

Dielectric Studies on CuO-Na2O-B2O3Glasses

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New Journal of Glass and Ceramics 2020年第4期10卷 45-56页

作者： Norhan Atef gomaa el damrawi Abdelmagud Hassan Lobna Sharaf el-Deen Physics Department Faculty of Science Mansoura University Mansoura Egypt Physics Department Faculty of Science Monofia University Egypt

This work is aimed to shed light on the dielectric behavior of CuO containing glasses, since no publications concerning this issue have been presented before. Different glasses in the binary Na2O-B2O3 system were prepared by melt annealing technique. XRD spectra have shown that the amorphous structure is dominant in all glasses containing mixed concentrations from CuO and Na2O. The crystalline phases appeared only in glass free from Na2O. The dielectric spectroscopy is applied to shed some light on the conduction mechanisms in terms of changing both the dielectric constant and the electrical modulus of the investigated glasses. The ac conductivity increases with increasing frequency and decreases with increasing CuO concentration. Both the dielectric constant and dissipation loss is decreased with increasing frequency. Correlated barrier hopping (CBH) is considered an appropriate conduction mechanism results from the increase of frequency.

关键词： electrical Measurement Cuo Borate Glasses Impedance Spectroscopy