ultra-fine particle

• 超细粉体

ultra-fine particle的用法和样例：

例句

1. They pounded the grain into a fine powder.
   他们把谷子碾成细粉。
2. When the bead has cooled on the metal sheet transfer it to a mortar and grind to a fine powder.
   当球珠已在金属板上冷却，把它转移到一个研钵里，研磨成细粉。