prov:value
| - num, iron, lead, copper, boron, cobalt, beryllium, zinc, and tin; metal alloys such as steel, brass, bronze, boron carbide whiskers, and tungsten carbide whiskers; metal oxides such as zinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium oxide, tungsten oxide, lead oxides, and zirconium oxide; particulate carbonaceous materials such as graphite, carbon black, cotton flock, natural bit
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