I am performing the ball milling of Aluminum powder (25 micron)at 150 200 and 250 rpm for 3 6 and 12 hrs in presence of toulene. At 150 rpm and 200 rpm I got the aluminium Powder in slurry form. But at 250 rpm for the 12 hrs I observed the agglomeration of aluminium Powder. I want to know whether results correct or not.
I suggest that you consider the ratio between the selected rotation speed and the critical rotation speed of the ball mill; cf.:
https://www.researchgate.net/post/How_can_I_determine_the_best_RPM_for_Dry_Ball_Milling_machine_in_order_to_let_the_balls_to_fall_from_the_best_angles
https://www.911metallurgist.com/blog/ball-mill-critical-speed
Agglomerated coarse Al powders consisting of nanoparticles were synthesized by low energy ball milling process, and subsequently their structures were characterized in terms of agglomeration size, shape, and porosity depending on various milling time, ball size, and ball to powder weight ratio in order to optimize the process parameters. A higher milling time caused a decrease in the agglomeration size and their shape tends to become spherical while reducing the pore sizes. The agglomeration size was also reduced as the ball to powder weight ratio increased and the ball size decreased. The partial cold welding of the nanoparticles at lower milling time and fully cold-welding of the nanoparticles at higher milling time were correspondingly responsible to produce larger and smaller agglomerations, respectively.
Aluminum powder witness shifting the morphology of particles from flake to spherical shape and an increase in particle size, welding and agglomeration with a rough surface to a specific size after specific time of milling. When particle size was reduced due to higher impact forces and temperature inside the barrel that forced particle towards higher density, lower porosity and closer to a spherical shape.
In general, the agglomeration size reduces as the milling time increases, and a higher ball to powder ratio produces not only smaller but also uniform and spherical shaped agglomerations with increased porosity
During the process, an increase in the ball to powder weight ratio means a greater number of balls are in use. Thus a greater collision rate and greater shear force is attained, resulting in higher fragmentation rate of the agglomerations than cold welding of the nanoparticles causing to decrease the agglomeration size.
I have no any reason to consider your report regarding Aluminum powder agglomeration throughout attrition milling is unreliable.
First, you need reconsider the powder-to -balls ratio used (you did not reported about it).
Second, you should re-check oxidation/contamination/primary agglomeration of the initial powder.
Third, you just need to chose the optimal attrition parameters. As I see, you've done it: only one attrition milling regime you applied caused agglomeration. Just decline it and use more successful regimes!
Ball to powder ration is 5:1.i have done the 4 experiments. 150 rpm 3hrs 200 rpm 12 hrs and 250 rpm 3 hrs. In first case I observed no agglomeration but in 2nd and 3rd case there is a agglomeration.
I thought that as rpm increases agglomeration increases
Also there is no primary agglomeration in raw powder.
Please find attached photograph of milled aluminium powder at 200 rpm for 12 hrs.
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders