Niagara Dissolve problem

Hello guys.
I just have this problem, dont know why this happen and make me upset alot.
I test the dissolve shader in Material instance, it work ok, but when I put it in niagara with dynamic parameter, dont know why there is a gray mask appear like the picture.
If I switch Material from “Masked” to “Translucent”, the gray mask wont appear, but it the material not work for the sword.
How can this happening?
Thank you very much.