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+{
+ "metadata": {
+  "name": ""
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "Chapter 21 : Diffusion of Solids"
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 3,
+     "metadata": {},
+     "source": [
+      "Example 21.1 pageno : 577"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "\n",
+      "# Variables\n",
+      "c_cu = 2.*10**13;\t\t\t#concentration of copper in /m**3\n",
+      "c_al = 4.*10**6;\t\t\t#concn of copper on other side of Al in /m**3\n",
+      "\n",
+      "# Calculations\n",
+      "t = 3.*10**-3;\t\t    \t#thickness in m\n",
+      "z = (c_cu-c_al)/t;\t\t\t#z = dm/dx,concentration graient\n",
+      "jx = 10.**21;\t\t    \t#outward flux of copperv atoms in /sq m/sec\n",
+      "d = -jx/z;\t\t\t        #diffusivity in sq m/sec\n",
+      "\n",
+      "# Results\n",
+      "print \"Diffusivity (in sq m/sec)  =  %.2e m**2/s\"%d\n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Diffusivity (in sq m/sec)  =  -1.50e+05 m**2/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "heading",
+     "level": 3,
+     "metadata": {},
+     "source": [
+      "Example 21.2 pageno : 583"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "\n",
+      "import math \n",
+      "\n",
+      "c_n = 12.;\t\t\t#nitrogen concentration in kg/m**3\n",
+      "t = 6.*10**-3;\t\t\t#thickness in m\n",
+      "\n",
+      "# Calculations\n",
+      "z = (c_n-0)/t;\t\t\t#concentration gradient in kg/m**4\n",
+      "d0 = 5.*10**-7;\t\t\t#in sqm/sec\n",
+      "q = 75.*10**3;\t\t\t#in j/mol\n",
+      "r = 8.314;\t\t\t#in J/mol/K\n",
+      "t = 400.;\t\t\t#in K\n",
+      "dx = d0*math.exp(-q/(r*t));\t\t\t#diffusivity in sqm/sec\n",
+      "jx = dx * 2*10**-3;\t\t\t#rate of flow of nitrogen in kg/sqm/sec\n",
+      "\n",
+      "# Results\n",
+      "print \"concentration gradient (in kg/m4)  =  %.0e\"%z\n",
+      "print \"Diffusivity (in sqm/sec)  =  %.3e m**2/s\"%dx\n",
+      "print \"Rate at which nitrogen escapes (in kg/sqm/sec)  =  %.3e kg/m**2/s\"%jx\n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "concentration gradient (in kg/m4)  =  2e+03\n",
+        "Diffusivity (in sqm/sec)  =  8.028e-17 m**2/s\n",
+        "Rate at which nitrogen escapes (in kg/sqm/sec)  =  1.606e-19 kg/m**2/s\n"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 3,
+     "metadata": {},
+     "source": [
+      "Example 21.4 pageno : 585"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "\n",
+      "import math \n",
+      "\n",
+      "# variables\n",
+      "z = 8.;\t\t\t#ratio of diffusion in silicon at 1350 C and 1100 C\n",
+      "x = math.log(z);\n",
+      "\n",
+      "# calculations\n",
+      "q = x/(1.35*10**-5);\t\t\t#activation energy for silver diffusion in J/mol\n",
+      "q1 = q/1000.;\t        \t\t#in kJ/mol\n",
+      "\n",
+      "# results\n",
+      "print \"Activation Energy in Silver diffusion (in kJ/mol)  =  %d kJ/mol\"%q1\n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "Activation Energy in Silver diffusion (in kJ/mol)  =  154 kJ/mol\n"
+       ]
+      }
+     ],
+     "prompt_number": 10
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
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