Dose it matter how many microns the aluminum powder is for thermite?

iv been to the sites and they have 5 micron 10 micron and 30 micron What dose it all mean!?Dose it matter how many microns the aluminum powder is for thermite?
The number of microns refers to the average size of the aluminum powder particles. A 5 micron Al powder has particles that are (on average) 5 microns in diameter. Another way to measure the size of particles is by mesh number; a larger mesh number means a finer powder.





The other answerer is correct - smaller particle sizes mean faster reactions. With thermite, it is very difficult to ignite mixes made with coarse aluminum, and relatively easy to ignite ones with finer aluminum.





That said, it can go too quickly to make a good stream of molten iron. The only aluminum powder I have is 1 micron, which goes too quickly (shower of sparks instead of a slow burn). Aluminum powder size is also given in mesh numbers (conversion table below). I think a good size of aluminum to use is between 100 and 300 mesh (~40-150 microns), but the size isn't super critical.





Shape is also important - spherical particles burn more slowly than high surface area shapes like flakes. Small flakes should not be used in thermite; they burn too quickly and are more expensive than other types of aluminum powder anyways.Dose it matter how many microns the aluminum powder is for thermite?
In any chemical reaction, the reaction will move faster if the material has more surface area. The smaller the particles are, the more surface area they have per unit of mass. That's why you use powder instead of a big block of material.