Reuse of steelmaking slags is important for the effective use of natural resources. Free magnesia (f-MgO) in steelmaking slag may cause serious problems because of a hydration reaction followed by expansion when it is reused for road construction. We present a promising method to identify f-MgO that causes volume expansion rapidly by investigating cathodoluminescence (CL) images and spectra of a steelmaking slag sample. f-MgO emitted red–orange luminescence from a peak at 755 nm. The mineral phases, 3CaO·SiO 2 and 2CaO·SiO 2 , emitted red and yellow luminescence from peaks at 720 and 590 nm, respectively. No luminescence of FeO and 2CaO·Fe 2 O 3 was detected. f-MgO changed its composition in the slag sample that was immersed in hot (70 °C) water for a week. f-MgO that was responsible for the volume expansion (combined content of FeO and MnO below 30 mass pct) retained a red–orange luminescence, whereas the other f-MgO lost luminescence. The CL intensity of the f-MgO that retained luminescence was more than 10 times larger than that of 3CaO·SiO 2 and 2CaO·SiO 2 . Therefore, we can distinguish f-MgO that causes volume expansion by detecting the intense red–orange luminescence from the peak at 755 nm in the CL image within a few seconds.

中文翻译：

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利用阴极发光快速简单地识别道路建设用炼钢炉渣中的游离氧化镁

炼钢炉渣的再利用对于有效利用自然资源非常重要。炼钢渣中的游离氧化镁 (f-MgO) 可能会导致严重的问题，因为当它重新用于道路建设时会发生水合反应，然后膨胀。我们提出了一种很有前景的方法，通过研究炼钢渣样品的阴极发光 (CL) 图像和光谱来识别导致体积快速膨胀的 f-MgO。f-MgO 从 755 nm 的峰值发出红橙色发光。矿物相 3CaO·SiO 2 和 2CaO·SiO 2 分别在 720 和 590 nm 处发出红光和黄光。未检测到 FeO 和 2CaO·Fe 2 O 3 的发光。f-MgO 在浸入热 (70 °C) 水中一周的炉渣样品中改变了其成分。导致体积膨胀的 f-MgO（FeO 和 MnO 的组合含量低于 30 质量 pct）保持红橙色发光，而其他 f-MgO 失去发光。保留发光的f-MgO的CL强度是3CaO·SiO 2 和2CaO·SiO 2 的10倍以上。因此，我们可以通过在几秒钟内检测到来自 CL 图像中 755 nm 峰的强烈红橙色发光来区分导致体积膨胀的 f-MgO。