What it is more accuracy in order to measure metal particle size, in a metallic catalyst supported, from the results of TEM, SEM or XRD??
For the point of view of surface and why ??
Zenaida Guerra Que
What is your system and application?
if you’re interested in surface (area) then you should be doing BET physisorption and the appropriate chemisorption. For supported catalysts, ESCA/XPS or Auger is essential for surface composition in relation to the bulk.
in terms of (bulk) particle size distribution then laser diffraction will do the job. For the size of the metal particles on the support then SEM is usually OK - this gives you essential visualization of crystallinity, agglomeration and aggregation and an estimate of the particle size distribution if enough particles are measured. TEM is reliant on the sample preparation and particle selection. XRD via line broadening and the Scherrer equation will give a single number for the crystallite (not particle) size: there is no distribution of crystallites generated even though we know this must exist. Williamson-Hall is a better tool here as strain broadening can also be assessed. Both Scherrer and W-H rely on the instrumental broadening to be evaluated (usually with a known crystalline material; I used quartz - nowadays LaB6 is used).
Read the books by Gregg/Sing and the excellent Structure of Metallic Catalysts by J R Anderson.
Dear:
1. The techniques of high-resolution FESEM, and HRTEM with SAED with proper indexing confirm the synthesis of the material film.
2. XPS explains the chemical part of the material.
3. AFM study uses to analyze the roughness of the film.
4. X-ray diffraction technique utilizes to determine the structural nature of the studied sample (amorphous state or crystalline state).
Any of the above technologies available in your laboratory can be used for the purpose of the above.
Ammar Qasem
We’re talking of supported metal catalysts which will be in powder, not thin film, form. XPS deals with the top 5 - 10 atomic layers, not the bulk composition.
Thanks for sharing your knowlegde, it is important to me. I have worked with metallic supported catalysts, such as Ag/ZrO2-CeO2, Cu/Al2O3-CeO2, Ni/Al2O3-CeO2, silver supported on solid solution and copper and nickel on mixed oxides and recently bimetallic supported catalyst AgCu/Al2O3-CeO2; AuCu/Al2O3-CeO2 and NiCu/Al2O3-CeO2. These materials are applied in CWAO of ROCs and production of biofuels.
@alam F Rawle thanks, for your contribution. You explained well the idea that i have, because in nanomaterials, some tecniques can take information from bulk and another only from surface as XPS.
@Ammar Qasem thanks for your explication. Another important techniques.
@Chandan Kumar Tiwari, thanks a Lot for your explication of particle aglomeration during drying in nanomaterials in TEM analysis and the strategy you mentioned is specific, i would take account the DLS and cryo-TEM. I hope to help You some day. Mi email is [email protected]. For keeping in contact.
Thanks everyone.
Zenaida Guerra Que
I worked with supported (SiO2, BaSO4, C, Al2O3 etc) Pd, Pd-Au, Pd-Ag, and a bunch of other materials many years ago.
You asked about accuracy - all the methods measure what they are given and have international standards (ISO & ASTM) associated with them. Accuracy is always defined against a known, certified standard utilizing the same technique. The more techniques you have then the more information you can collect usually.
References I mentioned (I was on my hang glider again and unable to look them up easily on cell 'phone):
- 'Adsorption, Surface Area and Porosity' S J Gregg, K S W Sing Academic Press (1967)
- 'Structure of metallic catalysts' J R Anderson, Academic Press (1975)
For powdered, metal oxide supported catalyst the crystallite size can be determined by the Debye-Scherrer equation from XRD planes. Further, you may verify the size by TEM analysis using Image J software.
I worked on bimetallic catalysts and found the size by both (i.e, Debye-Scherrer equation and TEM using Image J) techniques, and are found comparable results (with only a difference of few nanometers).
Mohammad Yusuf
There is no such entity as the Debye-Scherrer equation. There is a Debye-Scherrer camera and a Scherrer equation... (And a Debye model, BTW).
TEM has sample preparation issues. See attached by Bragdon. A set of monodisperse spheres microtomed will produce an apparent distribution of discs.
Please use image J on picture b) also attached. See this debate:
https://www.researchgate.net/post/How-to-calculate-the-particle-size-from-SEM-and-TEM-images
How did you compare TEM with Scherrer when the latter only produces a single number and the former a distribution? The is a big difference between particle size and particle size distribution. Plus we're assuming you're looking at crystallites in both cases.
Alan F Rawle excellent explication for how correctly to measure particle size by TEM and SEM, according to the great experience that you have. Besides XRD can measure crystalline (no particle) because it take into account a one specific plane in the lattice, it not possible take information for the distribution of crystallites. Thaks a lot. And I am going to get the excellent Structure of Metallic Catalysts by J R Anderson in order to read and understand more.
I am going to take into account in order to improve mi results, that´s why I asked this question. I hope to help you some day as you help me. Mi email es [email protected]. Best regards.