~...~I/t
Sf
Identify the lattice plane and lattice direction sketched.
4
For ~,
we need the reciprocals of
fractional intercepts along the axes.
y
O
1/4
With origin at '0', we get intercepts of -{1/4),
{1), {00), hence plane is (410
).
x
For direction, we go from start to end of line in
cell, hence --(1/4) (1), (-1).
Clearing fractions, [144]
Direction
lies in plane, --hu + kv + £w = 0.
~
(4xl)+(lx4)+(Ox4)=
0
Sodium is a Group I BCC metal of atomic radius 0.186 nm. The charge on an electron is 1.6 x 10-19C;
the electron mobility (~) in sodium is 0.0053 m2Ns. What is the likely electrical conductivity of sodium,
.Q.-lm-l? (Calculate number of atoms/m3 first.)
5
For a BCC metal, atoms contact along the cube diagonal, 4R.J3 a
Hence
'a' = 4(0.186)/.J3 = 0.4295 nm .
We will equate 1 atom to 1 charge carrier.
We have 2 atoms/cell, so 2 charge carriers per a3 per 0.079 nm3.
Hence, per m3 we have {f' r\,.
.,r\
i1 r\-27
\ -2.52x 1028
/m3.
\0.079 J\xI0-
J
0" = nq~ = (2.52) (1028) (1.6) (10-19) (0.0053)
0" -2.13 x 108 o.-lm-1
6.
The micrograph
below shows the crystal grains in a metal at 100x. Please determine the ASTM
grain
size number.
T count -64
grains per in2
~,
~, -,-,'
.I'-'"
.l
1
m
-'
"'-
1" ~"".
,'.
.,
..r.'
.~'
~
~'
1 If
I
"ty
( ~ ,Q;-
..-
~ ~<l
.kJ'
1).{
-l.,K
, :tJ
The magnification
is
100x, so no adjustment
needed.
N = 2n-l = 64 = 26
6=n-l
n=7
h-JY\r;~
.i-.
.;.
v ~
\.-'--t1