aL 1 =3z 50 40 well annealed For isotropic materials, 30 rapid cool homogeneous in three 20 directions,. Volume expansion coefficient 100 200300400500600700 is 3 times larger than linear Temperature expansion Glasses are isotropic Fine grained polycrystals are isotropic
• For isotropic materials, homogeneous in three directions,. • Volume expansion coefficient is 3 times larger than linear expansion • Glasses are isotropic • Fine grained polycrystals are isotropic V L P V P L T V V T L L 3 1 1 0 0 = = =
Thermal Expansion of Alkali Borate Glasses 27 oLi 口Ne OK 2 Rb NOISNYdX3 20 40 60 100 MOL%R,0 Addition of alkali modifier decreases thermal expansion coefficient in alkali borate glasses Modifier in low alkali borate glasses,cross links glass structure Creation of tetrahedral borons Adding bonds to boron,increasing connectivity of network Strengthening the network Rigidity of the glassy network increases Thermal expansion decreases with modifier
Thermal Expansion of Alkali Borate Glasses • Addition of alkali modifier decreases thermal expansion coefficient in alkali borate glasses • Modifier in low alkali borate glasses, cross links glass structure • Creation of tetrahedral borons • Adding bonds to boron, increasing connectivity of network • Strengthening the network • Rigidity of the glassy network increases • Thermal expansion decreases with modifier