King Abdulaziz University Chemical and Materials Engineering Department Supplementary Information
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
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.
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
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
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
King Abdulaziz University Chemical and Materials Engineering Department
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
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
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
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department Crystal Directions
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department Crystal Planes
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department
King Abdulaziz University Chemical and Materials Engineering Department