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Information for XRD Prac Write Up : David Wexler
Information for XRD Prac Write Up : David Wexler
Information for Diffraction Report No 2 Write Up David Wexler
X-ray Diffraction Report No. 2 Write-up instructions
Report is due via Turnitin on Wed. 10th June, 10:00 pm, Worth 20%
Note: The answers in this report need to be in your own words. Significant marks will be deducted from your report if identical wording is used for reports produced by different people. As in XRD Report 1, remember to use and cite references (MARKS will be lost for poor referencing). Extra marks will be given for evidence of deep thinking and/or understanding.
Part A Understanding a Search of the Database which gives a range of possible results (8 Marks)
Figure 1 Shows XRD processed data obtained from a mixture of 2-Powders; BCC Tantalum (Ta) and Face Centred Cubic Praseodynium Oxide (PrO2). The results were obtained using our Bragg-Brentano diffractometer Traces Software and the ICDD Search-Match Database PC-PDF2. Some of the data processing steps are shown in the Figure. A search-match was performed using a search window of 0.2 degrees and using tie ICCD-PC-PDF database database from all the elements marked yellow in the periodic table. A tabulated output of the search-match is also shown in the Figure.
Tabulated Output .. The top 5 Search-match results in order of merit:
Match PDFCard No. Phase Name (Chemistry) Merit Ic/Io Peaks Matched Structure
1/50 XXXXXXXXXX NIOBIUM VANADIUM HYDRIDE/Nb0.498 V0.50H 1.00 3/3 Im-3m
2/50 XXXXXXXXXX TANTALUM/Ta 1.00 3/3 Im-3m
3/50 XXXXXXXXXX NIOBIUM/Nb 1.00 2/2 Im-3m
4/50 XXXXXXXXXX NIOBIUM/Nb 1.00 3/3 Im-3m
5/50 XXXXXXXXXX PRASEODYMIUM OXIDE/Pr O2 XXXXXXXXXX0.41 5/5 Fm-3m
Figure 1 XRD Output an Search Match Results performed on a mixture of two powders, Ta and PrO2
Part A Continued.
As can be seen from the analysis in Fig. 1, Ta was listed only as the 2nd best match, and PrO2 as the 5th best match, even though Ta and PrO2 are actually the only phases present in the sample. Other structures included a database card matching a hydride phase of Nb and V, and two separate database cards matching pure Nb.
Part A Questions:
i Briefly explain what information is revealed in the six XRD spectra in Fig. 1 (e.g., You may need to zoom in the view in order to see some results in more detail). XXXXXXXXXX2 Marks
ii Explain why Pure Niobium was appears as a possible match, with pedicted peaks very close to those of Ta. XXXXXXXXXXMarks
iii Explain why a coupound of Nb and V, which also contains interstitial hydrogen might have the same crystal structure as Ta. XXXXXXXXXXMark
iv PrO2 has the space group Fm-3m. What is the common name for this type of cubic structure? XXXXXXXXXXMark
v Go to the Crystallography Open database http:
www.crystallography.net/cod/ and perform a search for structures containing both Pr and O. You should be able to locate .cif files of the phase O2Pr, having space group Fm-3m. Wright down the COD ID for one of these .cif files and write down the lattice parameter. XXXXXXXXXXMarks
Part B Interpreting Diffraction Outputs after Milling a Mixture of Inorganic Powders (7 Marks)
Figure 2 shows are XRD outputs from a mixture of Copper Powder, Aluminium Oxide (Al2O, also called Corundum) and Ca
on (in the form of Graphite). The blue (upper) XRD output is from the undeformed sample. The sample was made by gentle mixing of the three powder ingredients. The lower XRD output (Red) is taken form the same sample after ball milling of the powder mixture for 60 hours (by tumbling the powder in a round chamber with heavy steel balls). The milling was done in the ball mill to pulverise the powder mixture, introduce severe deformation, and to reduce the crystallite sizes.
Peaks used for crystallite size estimates
Figure 2. XRD Outputs from as-received powder mixture (Blue) and mixture after ball milling for 60 hours (Red) in a controlled atmosphere ball mill.
You will notice that both the Corundum peaks (Green Peak Position Markers) and Copper peaks (Brown Position Markers) have
oadened and changed shape and height after milling. This is due to a combination of refinement of the crystallite size and, for the case of Copper, introduced defects. The graphite (Ca
on XXXXXXXXXXpeak at around 26.6 degrees (Matching the Orange marker) has disappeared after milling.
Part B Questions
i. Explain what might be the likely reasons that the Graphite Peak (Orange marker) has disappeared. To answer this you need to think about what might happen to the mix of powders, as the particles are compacted, sheared and
oken up by the action of the balls striking and shearing the powder particles. Then think about what this might do to the diffraction peaks associated with the different powder particles in the mill. XXXXXXXXXX3 Marks)
ii. Using the Sche
er formula (Given in Fig. 3, and also described in your XRD lecture notes) calculate both the Copper and the Corundum crystallite sizes after milling, based on the information given below. Give reasons why the results for copper and Corundum differ (there is more than one possible reason). XXXXXXXXXX Marks)
Figure 3 Example of estimate of FWHM Peaks using Traces Software (Peak Positions were identified after Kstripping and smoothing)
Peak Angle at peak FWHM
Copper Pk before Milling 50.45 0.26
Copper Pk after Milling 60 Hrs 50.35 0.99
Al2O3 Pk before Milling 57.51 0.19
Al2O3 Pk after Milling for 60 hrs 57.70 1.49
Part C Residual Stress and Interpreting combined XRD and SEM Results XXXXXXXXXXMarks)
(i) Describe in simple terms how an XRD instrument can be used to perform a residual stress analysis of a strained steel sample. What needs to be measured, and how are the measurements performed. XXXXXXXXXXMarks)
(ii) Below are XRD outputs and SEM EDS Maps of a sintered mixture of Nitrided Ti and Fe. Explain how these XRD results were combined with the SEM-EDS mapping results to determine the phases indicated on the fracture surface (Bottom SEM Backscattered Image). XXXXXXXXXXMarks)
Figure 4 XRD, EDS Maps and SEM Fracture Surface of a sample of Nitrided Titanium, Liquid Phase Sintered in an Fe-Ti containing liquid.