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Unformatted text preview: a high hydrogen gas from a low hydro-gen gas at OSOpC. 5 x ld H atoms/cm3 are in equilibrium with the hot side of the foil, while 2 x 103 H atomVcm3 are in equilibrium with the cold side Determine (a) the concentration gradient of hydrogen and (b) the flux of hydrogen through the foil. 2 x 1 0 3 - 5 x l O E = -1 969 x 108 H atoms/cm3 ' cm Sofution: (a) LclLx = (0.001 in.)(2.54 cm/in.) (b) J = -D(Lcl L,x) = -0.0012 exp[-3600/( I .987X923)](- 1969 x 108) J -0.33 x 108 H abms/cm2 . s 5-43 What temperature is required to obtain O.SO% C at a distance of 0.5 mm beneath the surface af a 0.207o c steel in 2 h, when I .10% c is present at the surface? Assume that the iron is FCC. Solution: l'1 - o'5 ,.rff= o'667 = erf[o'05/ zJ a I O.OS1Z',lfr =0.685 or Jil =0.0365 or Dr=0.00133 r = (2 hX3600 s/h) = 72gg . p = 0.00B3nzQQ = 1.85 x l0-7 =a.23 exp[-32,g0an.gg7n exp(-16,558/7) = 8.043 x 10-7 f=ll80K=907oC...
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- Spring '08
- 1911, August 8, December 11, Calculatehejump rateat 750oC