Polymeric Nature of Glass Melts

摘要: X-ray diffraction patterns from SiO2 and B2O 3 in the glassy molten states are very similar. In fused silica basic building units SiO4 tetrahedra which share corners with one another; is built up of BO3 triangles sharing corners. The radial distribution functions (RDF) for silica, boric oxide, three glasses molar compositions 34 Na2O.66 SiO2, B2O3 43 CaO.57 P2OS shown Figure 8.1(a) (b). case first peak occurs at 1.62 A corresponds closely to silicon-oxygen distance many silicate crystals. From area under this peak, a coordination number 4.3 ± 10 per cent oxygen atoms about each silicon has been estimated [1], so establishing that exist crystalline form persist glass. RDF atomic density falls almost zero 2.2 A, indicating zone between oxygenoatoms not atomically populated. Thus within sphere radius permanently associated atom, because if they were move any significant frequency beyond boundary, time-average could be zero. Such completely prohibited does occur salts (where liquid predominantly ionic), arises there strong covalent bonds oxygen. curve immediately after comlists two overlapping peaks — oxygens (2.65 A) another silicons (3.2 A).