Lithium cobalt oxide accounts for 30% of the cost of a lithium-ion battery. Air, however, is free.

锂钴氧化物的成本占到锂离子电池的30%，而空气却是免费的。

youdao

He and some of his grad students wanted to use nitrous oxide as an emissions-free energy source.

他和他班上一些大学生想利用氧化氮作为无排放的动力能源。

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The assumption is made that if there is no detectable free iron, the metal surface is clean enough for a uniform oxide film to develop.

假定如果没有探测到游离铁，则金属表面就是足够清洁以形成均一的氧化物膜的。

youdao

The fuel in No. 3 is a blend of plutonium and reprocessed uranium, referred to as MOX (for mixed oxide) and manufactured by the French nuclear company AREVA. MOX fuel rods are also less stable than plutonium-free rods.

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