Looks good. Supposing this is for a game, maybe you shouldn't use black background for working on this kind of asset, because this explosion will never be shown over a black background inside a game. In fact, you can alternate a white circle, black circle frames on detonation, like in Metal Slug. Transparent or gray background is better for this kind of art, in my humble opinion.
@albertov
Gray sounds cool for this. I'll try that out. I wanna make a better one than this anyways.