Effects of cooling rate and oxygen partial pressure on heterogeneous crystal nucleation of supercooled lithium disilicate melt in PtRh20 containers
Effects of cooling rate and oxygen partial pressure on heterogeneous crystal nucleation of supercooled lithium disilicate melt in PtRh20 containers
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DOI：
10.1016/j.jnoncrysol.2019.119642
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发表时间：
2019-11-15
影响因子：
3.5
通讯作者：
Deubener, J.
中科院分区：
文献类型：
--
作者：
Al-Mukadam, R.;Deubener, J.
在两种不同的氧分压下，重复过冷铂-罗合金PtRh20制成的DSC容器中的二硅酸锂熔体。采用5种不同的冷却速度和332次的冷却速度，测定了异质晶形核动力学数据，具有很高的统计意义。两种不同类型的结晶很明显。在较高过冷温度下，第一种晶体完全由二硅酸锂晶体组成，而在较低过冷温度下，第二种晶体由偏硅酸锂和石英晶体混合而成。增加氧分压使这两种形核类型的概率都向更高的温度和更短的时间转变。假设在氧化条件下，随着铂合金表面氧饱和度的增加，在氧化金属、过冷熔体和炉气之间的三相界面附近会促进晶体形核。
Lithium disilicate melt in DSC containers made of platinum rhodium alloy PtRh20 is repetitively supercooled at two different oxygen partial pressures. Using 5 different cooling rates and 332 runs per cooling rate, kinetic data of heterogeneous crystal nucleation are determined with high statistical significance. Two different types of crystallizations are evident. A first at higher supercooling temperature exclusively consists of lithium disilicate crystals and a second at lower supercooling temperature consists of a mix of lithium metasilicate and quartz crystals. Increasing oxygen partial pressure shifts the probabilities of both nucleation types to higher temperatures and shorter times. It is assumed that under oxidizing conditions an increasing oxygen saturation coverage at the surface of the platinum alloy promotes crystal nucleation close to the three-phase boundary between oxidized metal, supercooled melt and furnace atmosphere.