Are you sure your sample is not nanocrystalline? 

Please look the way you're preparing TEM samples, or look around large area in a TEM sample. It is always better if you can look few TEM samples before arriving at a  conclusion.

In your image I see fringes with a spacing of about 0.2 nm, which could be from the (200) plane of Al (d=2.02A).

Thank you,

Diamond also has d-spacing of 0.206nm which is very close to Aluminium 0.202nm. I concluded that it might be diamond as the sizes of nanodiamond is (3-6nm). Please correct me if i am wrong.

I agree with  Krishna and compare, please, the thickness of the foil and the thickness of the amorphous oxide film Al2O3.

Please post the XRD data and details of the sample prep, morphology and metallurgical history.

Assuming you are using Cu KAlpha (0.154nm) the Bragg angles for d-spacings 0.202nm & 0.206nm would be 22.4072969o & 21.94932527o respectively. 0.5o is sufficiently separated to resolve clearly and unequivocally using XRD.

Here's the XRD data. XRD doesn't show any diamond peak. (2 vol%)

Hi, for a sure phase identification with HRTEM you need not only the lattice spacings but also a low indexed zone axis and best also contrast simulations. I would also HRTEM combine with STEM / EDX in order to clarify the problem.

I agree with Debora. Find a thin zone of your sample and orient it properly, you will get HRES images of the lattice, because if XRD shows it, then it must be there.

I would propose to to EDX (if not available  EELS may also help) in the TEM - this way you are able to identify the atoms you have in your spot. IF not aluminum is present, then the XRD peaks originate from somewhere else, but you have to assure this.

 I agree with Debora, clear fringes are seen. Also particle size is ~3-5nm from HRTEM. HRTEM sample appears contaminated. Again prepare sample for HRTEM carefully. You will be able to reveal the structure.  

Have you got an aluminum sample holder for XRD measurements? 

For XRD, the energy used is somewhat the average between the energy required to excite the aluminium atoms as well as the diamond. So peaks for both of them can easily detected. For HRTEM, the energy being used is far higher, so high that it can detect the diamond only.

Thank you all. All the comments are so helpful.

@Rahim: Can you cite some reference please.

What about good old diffraction? Nano-diamonds should produce (considering the size of particles) nice diffraction rings, and there should also be some evidence of Al present?

Post diffractogram as an Excel spread sheet when convenient. Certainly post the graphic version.

How did you conclude the  "aluminum matrix is amorphous"?

In my opinion, if your XRD pattern is showing sharp peak that means there is aluminium present the problem with HRTEM is may be due to the orientation of your sample's plane which may not contain aluminium. Another thing is for HRTEM we need very little amount of sample, if that portion doesn't contain aluminium then HRTEM will not give you the information you needed better way is  to go for elemental analysis technique that will definitely help you to solve this problem. You can also do HRTEM measurement for different orientations. 

The most common fixture material used in XRD equipment is Aluminium, it is important to check if your spectra is generated from the diffraction from the sample holder. After this you can work on checking the purity of the TEM sample and other issues. I think Marcella Bini, has already asked this question.

I think to finalize this issue the comparison between the two images of TEM (nanoDiamond only and nanodiamond reinforced in aluminium) should be made, also You should confirm the presence of Al by using EDS and EDS mapping complementary with TEM image.

In my humble opinion, you can try to dilute the liquid phase samples prior to the mesurement of TEM. Becasue I just feel that your samples are yet too thick to detect the D-spacing's shapes.  

Hi Biswajyoti.., in addition to previous answered....I think you have to run also your XRF test to know exactly your composition first.

I think maybe you can try to use EDS or EELS to identify the element located between the nanodiamond. And I really hope you didn't use aluminum specimen holder for XRD.

If you have Sharp Al Peaks in the XRD, it means that your Al grain size is rather large. You hav'nt attached your XRD, but I will guess the grains are much larger than your HR image in TEM. First do EDS, Is Al present? No It was probarbly your sample holder ;-). If yes: go to lower mag, say 20000 x focus your beam to a spot and press diffraction. Now you get a kikuchi pattern, tilt your sample  a follow the lines to a major zoneaxis, acquire a diffraction pattern, calculate and compare with Al. Maybe add a dark field image, then go to HR and you will have all the Al lattices you can dream of

To summarize a few key points in one place:

1. Do you have Al sample holder?

• If you do not use Al sample holder, you can trust the XRD.  You do have crystalline Al.
• If you did use Al sample holder, this can be ok, if your sample is thick enough and covers the holder completely.  If the incident x-rays can reach the sample holder, either by penetrating through the sample or where the Al holder shows around the edge of the sample, then you will get Al peaks from the holder.

2. HREM sample preparation and data acquisition and analysis can be challenging and is certainly non-trivial.

• Follow Flemming B. Grumsen's advice in the post just before this one.
• Please be careful talking about amorphous aluminum.  Aluminum will always be crystalline in its pure form (above a few K).
• Any fresh Al surface will immediately become oxidized on exposure to air.  Since TEM samples must be very thin, you may be looking at an area where all of the Al has been oxidized between the sample thinning and the microscope.

I think the problem which you facing is the sample preparation. and I agree with the people  said you have to do EDS or EDX experiment in order to see the formation of your film because diamond is not easy to deposited in other material substrate. The high resolution TEM image of your sample also a pointed to AL formation.

Best wishes 

Hi,

I agree with previous comments. Should you do EDS in order to confirm Al, but it seems your sample is too thick to see sharp interference fringes in HRTEM images. You actually can see some rough fringe patterns in your image (see attached). In addition, sometimes highest magnification does nor help too much. It does not increase your resolution! Try to work in "lower" magnification, let's say 400-500kx until you are able to observe some pattern in the live FFT.

Have fun!

Erico

Hi,

I am not sure whether aluminium can stay in amorphous state. If yes: make an classic SAED diffraction pattern and you will see the nanodiamonds crystallic rings together with amorphous rings originated from aluminium matrix. However you have to make a sure that the contamination amorphous layer is not present on your sample. If not: you will see crystallic rings from both, the aluminium and nanodiamonds.

Please, don´t rely on HRTEM image!

If it is possible to prepare the amorphous aluminium, please consider its stability. Don´t forget of conditions inside the TEM column: high vacuum and heating under the beam. Vacuum lower all transformation temperatures dramatically and amorphous samle may comes to crystalline state very easily.

So, my suggestion is take the SAED diffraction pattern and check the chemical composition by EDS or EELS.