I assume that the first peak base width will give the pore width of zeolites. Mostly we are getting the information regarding the pore size of zeolite from the first peak position. Of course BET adsorption isotherm is the final. However, the initial information regarding the pore size we can get from this. What is your opinion on this.
The first peak describes you the biggest lattice plane distance, i.e. this information tells you the distance of lattice points which define the translation lattice but does not contain any information about the atomic positions. For very, very, very special cases this might be a very rough assumption, but in general it is absolutely wrong, i.e. in your case it might work but in general it won't.
I am agree with Dr. Nolze,s comment. Without special instrumental attachment with the powder XRD, it is difficult to measure the pore size as suggested by Elisban. However, Small angle X-ray diffraction is a very useful technique for the purpose. Using traditional lab XRD one can calculate the amount of porosity of the sample with modification of I (relative) formula.
The standard way of determining pore sizes in zeolites is by selective adsorption of molecules, i.e., certain molecules will be too large to enter the pores at a prescribed temperature, while others will enter freely, and some that are close to the pore size will sorb very slowly. XRD on powders can work for certain mesoporous materials if you make assumptions about wall-thickness (as in the earlier replies to this question), but for zeolites you would need to do either single-crystal diffraction or detailed Rietveld refinement, probably coupled with high resolution TEM. Adsorption tests might be a better way to go.
Dear all
XRD tech. it has nothing to do with pore sizes in zeolite.
Best regards
I am agree with the answers given by Prof Coker and Prof Nolze.
So what kind of material are you looking for.
You can also view the structures (if CIF is reported for it) in certain softwares like Vesta and can roughly map the size of pores in zeolites. But you have to be careful to substract the actual size of the bonding atoms from the distance.
It maybe be measured by doing Low-angle PXRD at 2 theta range 2 - 5. A peak is generated with an intensity that when integrated, it will give you a value that approximates the respective pore size. All the same, this works for mesoporous powdered materials. However, further verification will need to be conducted eg HRTEM and BET.
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