TEAM ASSIGNMENT Nº2: X-Ray Diffraction
10 pts
Due on Dec. 15 in class
In this assignment we will identify two different unknown metals present in
a mixture. This is the situation: a careless graduate student mixed
in one vial metal powders of two different sources that believed were
the same. This enraged our lab technician who decided to test the
mixture in our Siemens D500 x-ray diffractometer. Apparently the powder
mixture seems to be made of two cubic metals. Your mission, should
you decide to accept it, is to help our lab technician identify
both metals, following the guidelines below.
In the this link you will find
the x-ray pattern obtained for the powder mixture. The D500 x-ray
diffractometer is furbished with an x-ray tube with a copper target,
so it uses a Cu K-alpha radiation.
Important: To download the text file
right-click on the hyperlink and follow the "Save as…" option
to save it as a text file. Do not open the file
in Internet Explorer and then copy it (it is messier to work
with such file format). The dataset consists of two columns, the first
one being the diffraction angle 2-theta and the second one, counts
of the diffracted X-rays (Intensity).
a) Produce plots of X-ray Intensity vs. 2-theta;
b) Produce plots of Relative Intensity vs. d-spacing (in nm);
c) Identify the crystal structures of both cubic metals;
d) On the plots in a) and b) label all the peaks with their corresponding
Miller indices of the planes that produced them;
e) Determine the approximate lattice parameters of both metallic materials.
f) Identify the metals.
g) Compute the theoretical densities of both elements and compare
them with data from the literature.
h) The powder appears to be fine. Please determine if this is a nanosized
sample.
Additional practice (you don't need to hand in this but it
will prepare you better for the exam): Change the radiation
used in the experiment (Co-K-alpha instead of Cu-K-alpha ) and observe
how the spectrum is modified. Then decide what target you would use
if you need to have better resolution (accuracy) in the measurements
of: a) low-angle peaks (<30°) and b) high angle-peaks (>70°).
Hand in a report of your work (analysis and graphs). BE PROFESSIONAL
IN PRESENTING YOUR REPORT. Do not include the data files! Include
the plots by copying your graphs from Excel to the clipboard and then
into Word, by using "Edit > Past Special..." and then
the option "Picture (enhanced metafile)." For the sake of
simplicity it is recommended that you use Excel for the analysis of
the X-ray patterns. We prefer a hardcopy of the report. Please
include ONLY the names of those team members who participated in the
assignment. Leave out (do not report) those students who did not collaborate.
Only those students whose names are included
will receive credit for this assignment.
Bonus Assignment (8 pts,):
Do exactly the same for this
mixture of two metals. Prepare a second report independent from
the previous one. This pattern is much more difficult because there
is a significant overlap between the two peak sets!! So, you will
get full credit if you find out exactly what two metals these
are. If you do not have time, please do not do it. Also you can set
up smaller groups (or work individually) to complete this bonus part.
If you do so, please report only the names working on this part. Good
luck!
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