# Structure.questions XIV answer - MTLE-2100 Structure of...

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MTLE-2100 Structure of Engineering Materials, Questions XIV-Answer 1. SiO 2 dissolves slightly in hot water. Calculate the normalized solubility, S/S 0 , at the tip of a line crack of SiO 2 as a function of the tip radius at 90 ° C. Use the tip radius, 10 Å , 20 Å , 50 Å and 100 Å . Plot the resulting ln (S/S 0 ) against the tip radius. ln(S/S 0 ) = γ (1/R 1 +1/R 2 )(M/RT ρ ). Molecular weight of SiO 2 = 60 g/mole Gas constant, R =8.314 J/mole,K Assume the glass-water interfacial energy γ = 0.1J/m 2 Density of silica glass, ρ = 2.2g/cm 3 R 1 = , R 2 = -10 Å = - 1x10 -9 m, -20 Å = -2x10 -9 m, -50 Å = -5x10 -9 m and -100 Å = - 1x10 -8 m. ln(S/S 0 ) = 0.1(1/R 2 )(0.06/8.314x363x2.2x10 3 ) = 9.03x10 -10 /R 2 For R 2 = -10 Å = - 1x10 -9 m, ln(S/S 0 ) = - 0.9, S/S 0 = 0.407 -20 Å = -2x10 -9 m, ln(S/S 0 ) = - 0.45, S/S 0 = 0.64 -50 Å = -5x10 -9 m, ln(S/S 0 ) = -0.18, S/S 0 = 0.84 -100 Å = - 1x10 -8 m, ln(S/S 0 ) = - 0.09, S/S 0 = 0.91

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2. Plot schematically vapor pressure, p, solubility, S, and vacancy concentration, n
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Structure.questions XIV answer - MTLE-2100 Structure of...

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