1. The typical undercooling of nickel for homogenous nucleation is 290 °C. With
ID: 2079507 • Letter: 1
Question
1. The typical undercooling of nickel for homogenous nucleation is 290 °C. With this amount of undercooling, how many nickel atoms need to group together spontaneously to from a nucleation site? Assume the lattice parameter of solid FCC nickel is 0.356nm.
2. Calculate the equilibrium concentration of vacancies per cubic meter in pure silver at 706 C, Assume the energy of formation of a vacancy in pure silver is 1.10 eV. If you need it the density of silver is 10.5 g/cm3. The answer should be in mole fraction with 2 decimals of accuracy.
Explanation / Answer
. Calculate the equilibrium concentration of vacancies per cubic meter in pure silver at 706 C, Assume the energy of formation of a vacancy in pure silver is 1.10 eV. If you need it the density of silver is 10.5 g/cm3. The answer should be in mole fraction with 2 decimals of accuracy.
N =No Pcu /atomic ass cu =
=(6.023 x10^23) (10.5 x10^6 g/cm3) /107.870 =5.86 x10^28 atoms/m^3
E =1.10 ev for vacancies at 706+273=979 k
nv= 5.86 x10^28 atoms/m^3(exp (-1.10ev/8.62 x10^-5 ev/K (979K))
=round 2. 4 X10^-4 vacancies /atom
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