5.9 A sheet of steel 2.5-mm thick has nitrogen atmospheres on both sides at 900°C and is permitted to achieve a steady-state diffusion condition. The diffusion coefficient for nitrogen in

steel at this temperature is 1.85 × 10-10 m2/s, and the diffusion flux is found to be 1.0 x 10-7 kg/m2 .s. Also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 2 kg/m3. How far into the sheet from this high-pressure side will the concentration be 0.5 kg/m3?Assume a linear concentration profile.

Fig: 1