Determination of average nanoparticle size by line width method

3 Determination of average nanoparticle size by line width method 

Most of the sohd catalyst is the porous solid composed of tiny particles. Surface area provided by active substance per rniit mass is related to the nanoparticle size, and hence the determination of nanoparticle size is of great practical significance for the preparation and application of supported Ru, Pt, Pd, etc. precious metal catalyst particularly. 

Due to the difference in the tjqie, preparation method of material, and operating conditions, the nanoparticle size distribution of catalyst can vary in a great range such as from one nanometer (run) to tens of run, or even to hrmdreds of nm, and that of active metal catalyst is in the range of 1-10 run. 

A particle of less than 200 nm can widen the diffraction peak, and the finer the nanoparticle, the wider the peak is, and therefore the method is also called as the line width method. This method can be calculated by using the following equation  

The wider the diffraction peak (the finer particle), the higher is the activity of iron catalyst in ammonia synthesis. Generally, the nanoparticle size of iron catalyst is about 20-30 nm. 

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