0-17 NMR studies of some silicate crystals and glasses
Başlık çevirisi mevcut değil.
- Tez No: 400202
- Danışmanlar: PROF. RAY DUPREE
- Tez Türü: Doktora
- Konular: Fizik ve Fizik Mühendisliği, Physics and Physics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2000
- Dil: İngilizce
- Üniversite: Unıversıty Of Warwıck
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
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Özet (Çeviri)
Crystalline and glassy silicates were investigated by means of“0 NMR. Thedependence of the measured efg on the Si-O-Al bond angle was investigated in somecrystalline aluminosilicate sodalites and kalsilite. The results show that CQ increaseswith increasing bond angle while 11 decreases with increasing bond angle and they bothfollow a similar function to that found for the Si-O-Si bond angle. The clustercalculations also confirm that the dependence of CQ and il on the Si-O-Al bond angleis similar to that of one Si-O-Si linkage. The chemical shift decreases as the bond angleincreases. However this dependence does not seem to be monotonic.The structural role of Al in aluminosilicate glasses was studied by means of ”O3Q MAS NMR in sodium aluminosilicate glasses with Si/Al= 3,1.5,1,0.7.3Q MASNMR results showed the presence of Si-O-Si species as well as Si-O-Al species inglasses with Si/Al>1. The 3Q MAS NMR spectrum of glass with Si/A1=0.7 displayedthe presence of Al-O-Al linkage as well as Si-O-Al. These results showed that as theSi/Al ratio decreases from 3 to 0.7 Si-O-Si linkage is replaced by Al-O-AI linkage asa result of addition of Al into the structure.The structural role of Sn in tin-silicate glasses was also studied mainly by meansof“O MAS NMR. The model developed from the ”0 MAS NMR spectra of theseglasses showed the possible coexistence of two and three coordinated oxygen atoms inthe structure. Therefore some of the Sn has to be in three coordinated to oxygen forcharge balancing. The“O MAS NMR spectra of a partially crystallised sample showedthree distinct sites which are assigned as Sn-O-Sn, Si-O-Sn, and Si-O-Si on the basisof their chemical shift. The C. values obtained from the simulations of these peakssupports this assignment. The ”Si MAS NMR of the same sample showed twocrystalline and a glassy peaks which are fitted to two crystalline and two glassy sites.The possible composition of this sample was calculated and found to be SiSn3O1o.
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