1. Please write down the basic building blocks for the glasses of 1) vitreous si

Question

1. Please write down the basic building blocks for the glasses of 1) vitreous silica, 2) alkali silicate, 3) alkali/alkaline earth silicate, 4) alkali aluminosilicate, 5) vitreous boric oxide, 6) alkali borate, 7) alkali aluminoborate, 8) alkali borosilicate, and 9) phosphate 2. The general formula for the alkali silicate glass is xR20 (100- x)Sio2. where R is the alkali metal ion such as Na, Li etc. and x is the molar fraction of R.O in alkali silicate glass. Please derive the expressions for the following parameters. Assuming x is a small number and you only have Q4 and Q3 units in the alkali silicate glass. 1) Total number of oxygen 2) Total number of basic building block or tetrahedra 3) Total number of Q3 units 4) Total number of Q4 units 5) Oxygen number of O3 unit 6) Oxygen number of Q4 unit 7) Average number of oxygens per tetrahedron 8) NBO fraction 9) BO fraction 10) Average number of NBO per tetrahedron 11) Average bridge corners or bridges per tetrahedron 12) Fraction of Q3 unit and Q4 unit 3. Describe the structures of the following silicate glasses in terms of the Qn units present in the network. Describe the types of tetrahedra present and state the percentage of each type present in the structure (a) SiO2 (b) 20 Na 0-80 SiO2 (c) 35 Na20-65 SO2 (d)45 Na20-55 SiO2 (e) 20 Na20-10 A1203-70 SiO2 (f) 10 Na20-10 A12O3-80 SiO2 (g) 25 CaO-75 SiO2 (h) 15 Na20-10 Ca0-75 SiO2

Explanation / Answer

1) Vitreous silica: SiO2

2) alkali silicate : Na2SiO3

3)alkaline earth silicate : RO · SiO2 ( R =  Mg, Ca, Sr, Ba )

4)alkali aluminosilicate: AI2O3, SiO2

5) vitreous boric acid: H3BO3

6) alkali borate : R2O–B2O3, (R=K, Rb, Cs).

7)alkaki aluminoborate: AI2O3, B2O3

8) alkali borosilicate: B2O3:Na2O:SiO2

9) phosphate: PO43-

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