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King Abdulaziz University Chemical and Materials Engineering Department Supplementary Information.

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1 King Abdulaziz University Chemical and Materials Engineering Department Supplementary Information

2 King Abdulaziz University Chemical and Materials Engineering Department The atomic packing factor (PF) of a bcc metal assuming spherical atoms (hard ball model) and calculating the volume fraction of the unit cell that is occupied by the atoms There are 2 atoms per unit cell in a bcc metal, and we assuming spherical atoms

3 King Abdulaziz University Chemical and Materials Engineering Department Other face-centered cubic structure  e.g. molecular structure of solid methane with 5 atoms occupying the fcc positions as a molecular unit.  NaCl structure, since the atoms are unlike.  a fcc NaCl = 2(r Na + + R Cl -)  Note that there is a gap between the Cl - ions, we can not apply the eqn used for lattice constant.

4 King Abdulaziz University Chemical and Materials Engineering Department Properties of simple cubic structures  Binary (Two component system)  The unit cell has two radii.  a CsCl-type = 2(r Cs + + R Cl - )/√3  CN = 8, r/R = 0.73,  not in case of MgO r Mg 2+ /R O 2- = 0.47 Calcium titanate, CaTiO 3 is also SC Ca 2+ are located at the corners of the unit cell Ti 4+ are located at the center O 2- at the center of each face Therefore, it is neither bcc nor fcc

5 King Abdulaziz University Chemical and Materials Engineering Department Polymorphism Diamond Graphite c The existence of two crystal structure of the same substance is called polymorphism. The two forms are called polymorphs. Diamond Graphite c Heat + pressure

6 King Abdulaziz University Chemical and Materials Engineering Department bcc fcc  CN of bcc Fe = 8 at room temp., PF = 0.68 and R = nm  CN of fcc = 12 at 912 o C, PF = 0.74 and R = nm  For bcc iron R = due to thermal expansion  The reaction involves volume changes and 1.4 V% ( l%) when the temperature is raised above 912 o C.  Volume changes is due to larger CN in fcc atoms Body-Centered Cubic Iron Face-Centered Cubic Iron

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8 King Abdulaziz University Chemical and Materials Engineering Department  Zirconia toughen alumina significantly, because it has 3 polymorphs  At high temperature changes from cubic to tetragonal with CaF 2 structure  The next step it changes to monoclinic, involves dimensional strain that consumes energy before fracture

9 King Abdulaziz University Chemical and Materials Engineering Department Crystalline Phases  Phase: is that part of a material that is distinct from other parts in structure or composition, e.g. ice-water The same composition but different in state  Phase boundary: between the two states locates the discontinuinity in structure Salt and saltwater brine, both contain NaCl but form different phases Alcohol-water (miscible) different composition but form one phase Oil-water (immiscible): two phases

10 King Abdulaziz University Chemical and Materials Engineering Department The unit cell of Cr metal is cubic and contains 2 atoms, if the density of Cr = 7.19 Mg/m 3 ; determine the dimension of Cr unit cell Mass of a unit cell = 2 Cr(52.0 g)/(6.02 x Cr) = x g volume = a 3 = ( x g)/(7.19 x 10 6 g/m 3 ) = 24 x m 3 a = x m

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14 King Abdulaziz University Chemical and Materials Engineering Department Crystal Directions

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18 King Abdulaziz University Chemical and Materials Engineering Department Crystal Planes

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