Would you please guide me about questions below via the attached file:
I mixed calcium chloride and sodium sulfate and precipitated prismatic monoclinic needle shape gypsum crystals that SEM (fig 1) shows it. I used XRD (fig 2) and by software and PDF database 2-33-311 found the peaks. Then I added additive 1 and I saw needle gypsum changed to plate like gypsum (Figs 5 and 6) and XRD shows change in intensity of the peaks (fig 3). Then I added additive 2 and saw needle gypsums elongated (fig 7 )and XRD shows it (fig 4).Now:
1- How can I name the gypsum faces in fig 8 according to fig 2 peaks?
2- Would you please name the faces (aaa) (bbb) (ccc) (ddd) (eee) for me?
3- In the case of additive 1, According to fig 3 and Fig 5, which faces of needle gypsum in fig 8 has been changed? Which direction x or y or z changed?
4- In the case of additive 2, According to fig 4 and Fig 7, which faces of needle gypsum in fig 8 has been changed?
5- Why did authors in figs 10 and 11, 12 and 13 have named the gupsum crystals faces different than XRD peaks?
Question is of fundamental interest in XRD. So I'm interested right away.
1. Where is your XRD data? Send Excell data to [email protected]
2. What XRD instrumentation and detectors do you have access to?
3. What is your ultimate objective with XRD? Why?
Note that based on the shapes of the crystals you may have strong influences on the conventional XRD diffractograms due to potential "preferred orientation" of the elongated of flat appearing "particles"/"crystals".
4. How do you prepare the sample for XRD? What are the precise steps? How do you pick up the powder and deposit on the sample holder?
5. What XRD geometry/optics are you using for your conventional equatorial diffractograms?
6. What X-ray incident beam conditioning?
7. You'd need a tool to record the 2D X-ray diffractogram to be able to sense the effect of the "needle" shape in the XRD pattern. Conventional photographic film for X-ray would do, unless you have the luxury of a real time 2D detector as we do and have had for over 3 decades. You'd need to create some standards by quantifying the micrographs in terms of "particle" size/shape/distribution. Only then would you be able to calibrate your XRD tool. In my opinion.
8. Other...
I want to name the gypsum faces with my XRD peaks. for example determine which face is (020)?
Also I want to prove the shape modification effects of additive on gypsum crystal by XRD patterns I mean by using SEM I tell the face (020) resized.
I suspect you'd see the effects of the particle shape and size in the transmission Laue pattern. If you picked up the powder on the adhesive side of Scotch Tape from the container as-was, then looked at the transmission Laue XRD pattern in situ. I've done so with composite materials with crystalline & amorphous content. Sort of like this:
I cannot open your attachment but I can say that for sure there is no relatioship between the indexing of diffraction peaks and the indexing of the crystal faces.
One idea : if you set your sample with specific orientation on your diffractometer support, you'll have an enhanced diffracted intensity from this specific orientation i.e. if you cover your support with your platelets and have an enhanced diffracted peak, it means that these faces are faces ... and so on !!
if you can cleave each of your surfaces and do the same, then you'll have your answers ..
but a Laue pattern would be much more efficient. Nowadays, with a CCD camera for example (like the one we get here) and a classical XR tube (equiped with foccusing polycapillary) , less than one minute is enough to record and defined which are the faces index.
An XRD four circle experiment would determine also your orientation matrix, then you can easily index and check which are your faces orientations.
But a face you can see by your eyes (morphology seen by light), once again has no relation with the intensity of its corresponding diffracted peak (seen by XRays), even this peak could be fully extint.
Defects your are producing within the structure when doping (like dislocations) have a strong effect on the growth speed of specific directions as often growth take place aound defects, that is why your morphology changes with the type and amount of dopants.
That is right Gerard! In my knowledge that is the only unequivocal in situ NDE method for establishing such surface oirentations in crystalline materials. These method are the basis of all of the Braggs' achievements and have been tried and tested for over a century now.
"Defects your are producing within the structure when doping (like dislocations) have a strong effect on the growth speed of specific directions", interesting note. I'd like to study some literature concerning this issue. Please post or forward PDF files when convenient. Thanks!
http://www.flickr.com/photos/85210325@N04/11604959265/
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