摘要
The structure of borosilicate glasses of composition 30Na<sub>2</sub>O-2Al<sub>2</sub>O<sub>3</sub>-25SiO<sub>2</sub>-xFe<sub>2</sub>O<sub>3</sub><sub></sub> (43-x) B<sub>2</sub>O<sub>3</sub> has been investigated in the composition range of 0.5 20 mol% Fe<sub>2</sub>O<sub>3</sub>. <sup>27</sup>Al, <sup>11</sup>B, <sup>29 </sup>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 Fe<sub>2</sub>O<sub>3</sub> (in low region up to 7 mol%) are the main glass modifier. Structural determination for borosilicate glasses with a high content of (Fe<sub>2</sub>O<sub>3</sub>) was carried out by FTIR spectroscopy, where both <sup>11</sup>B and <sup>29</sup>Si 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% Fe<sub>2</sub>O<sub>3</sub> and the N<sub>4</sub> values obtained by FTIR spectroscopy agree within error with the <sup>11</sup>B NMR results of the same glass samples. Fe<sub>2</sub>O<sub>3</sub> is a main glass modifier in the low-Fe<sub>2</sub>O<sub>3</sub>-content region (≤6 mol%). On other hand, it plays the role of glass former at higher content of Fe<sub>2</sub>O<sub>3</sub>. Increasing both N<sub>4 </sub>of boron tetrahedral units and chemical shift of silicon nuclei to reach maxima at 5 mol% Fe<sub>2</sub>O<sub>3</sub> confirms the role of Fe<sub>2</sub>O<sub>3</sub> as a glass modifier in the low composition region. On the other hand, fast decrease in N<sub>4</sub> with further increasing Fe<sub>2</sub>O<sub>3</sub> contents ≥6 mol%) is an evidence for iron oxide to inter the glass network as a network former.
The structure of borosilicate glasses of composition 30Na<sub>2</sub>O-2Al<sub>2</sub>O<sub>3</sub>-25SiO<sub>2</sub>-xFe<sub>2</sub>O<sub>3</sub><sub></sub> (43-x) B<sub>2</sub>O<sub>3</sub> has been investigated in the composition range of 0.5 20 mol% Fe<sub>2</sub>O<sub>3</sub>. <sup>27</sup>Al, <sup>11</sup>B, <sup>29 </sup>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 Fe<sub>2</sub>O<sub>3</sub> (in low region up to 7 mol%) are the main glass modifier. Structural determination for borosilicate glasses with a high content of (Fe<sub>2</sub>O<sub>3</sub>) was carried out by FTIR spectroscopy, where both <sup>11</sup>B and <sup>29</sup>Si 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% Fe<sub>2</sub>O<sub>3</sub> and the N<sub>4</sub> values obtained by FTIR spectroscopy agree within error with the <sup>11</sup>B NMR results of the same glass samples. Fe<sub>2</sub>O<sub>3</sub> is a main glass modifier in the low-Fe<sub>2</sub>O<sub>3</sub>-content region (≤6 mol%). On other hand, it plays the role of glass former at higher content of Fe<sub>2</sub>O<sub>3</sub>. Increasing both N<sub>4 </sub>of boron tetrahedral units and chemical shift of silicon nuclei to reach maxima at 5 mol% Fe<sub>2</sub>O<sub>3</sub> confirms the role of Fe<sub>2</sub>O<sub>3</sub> as a glass modifier in the low composition region. On the other hand, fast decrease in N<sub>4</sub> with further increasing Fe<sub>2</sub>O<sub>3</sub> contents ≥6 mol%) is an evidence for iron oxide to inter the glass network as a network former.
作者
Gomaa El-Damrawi
Abdel Meguid Hassan
Rawia Ramadan
Sammer El-Jadal
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)
