I have andesite source of road aggregates. I did XRD test on bulk powder and oriented samples ((1) air dried, (2) treated with ethylene glycol at 60oC, and (3) heat-treated at 550 oC for 45 minutes). The oriented samples were prepared on 2.54 cm slides after three stages of pre-treatment procedure to isolate clay-sized particles for identification.
Experiments were run using a PANalytical Empyrean X-ray diffractometer operating at 45 kV and 40 mA. The diffractometer employs a Cu K-alpha radiation with a 1.5406 Å wavelength (Kα1) and has a graphite monochromator with a PIXcel Detector. Scans were run at a 2θ angle from 4 to 70°, with a 0.013° step size and an integrated 100 s dwell time.
I have some doubts about my result and I cannot interpret some of the peaks.
1- Peak 1-1 (P 1-1): The peak in fresh materials- bulk powder (Figure 1) around 13.5 degree (2 theta). This peak is removed in the weathered sample (Figure 4)
2- Figure 2 shows the XRD results for fresh materials- bulk powder (the black line) and oriented (the red line).
- Why some peaks are removed in the oriented sample (especially the peaks more than 43 degree (2 theta)) and what minerals are those peaks? These peaks are removed in the weathered sample as well (Figure 4).
- Why the intensity of the peaks reduced dramatically?
3 - There is a bump from from 15 to 35 degree (2 theta) in the oriented fresh sample while there is almost nothing in the bulk powder (Figure 2). Can this bump be related to the presence of volcanic glass or it is only associated with the glass slide?
4 - Figure 3 shows the XRD test results for weathered materials.
- What is the peak 3-1. This peak has higher intensity in the oriented results.
- What are peaks 3-2 and 3-3 (at 19.8 and 20.8 degree (2 theta), respectively). These peaks have higher intensity in the Bulk powder and they do not exist in the fresh sample (Figure 4)
5- Figure 5 shows the XRD results of oriented weathered sample (air dried- Glycolated, and heated) and weathered- bulk powder.
- What is the peak 5-1? This peak disappeared in the heated sample.
7- Is there any volcanic glass in my samples, especially the fresh one?
6- Is there any sign of weathering that I can get from my XRD test results?
Please let me know if you need more information.
We can keep speculating on what the peak mean and not get any meaningful thing done. Mathias has really nailed this. All the requirements to do better justice is not extractable from the image. Did you change the slides for the bulk? Or you used glass for all different measurements? The hump can be very informative on amorphous situations / disorder.
Dear Ebrahim,
Question is about the difference of bulk monocrystal diffraction and powder diffraction.
Imagine please the pictures of Laue and Debye method.
Laue has point peaks and if you move detector along the line which can cross one point or more reflections.
- Laue deals with polychrome X-ray. You use monochrom X-ray, so on in random crystal position you can found little volume of peaks ... Position of each peak belongs to ICDD data of your sample. Peak intencity depends on many conditions - it is not coinside with peak intancity of ICDD data.
Debye method - your detector cross all cone of reflections.. You can compare the shape of yours rocking curve with ICDD data.
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