答：先要精选，再制砂后，经磁选、浮选或化学提纯后，二氧化硅能达到95%。
Answer: want first choice, remaking sand, through the magnetic separation, flotation or chemical purification, silica be 95 percent.
论述砂带磨削的特点和利用砂带再制的异形涂附磨具的设计及其应用场合。
The feature of abrasive belt grinding as well as the design and application of special-shaped coated abrasive tool made of belts are described.
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