Self-Diffusion of the Constituent Elements in Alpha-Alumina, Mullite and Aluminosilicate Glasses
Self-Diffusion of the Constituent Elements in Alpha-Alumina, Mullite and Aluminosilicate Glasses
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DOI：
10.4028/www.scientific.net/df.8.80
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发表时间：
2016-07
期刊：
影响因子：
--
通讯作者：
P. Fielitz;G. Borchardt
中科院分区：
文献类型：
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作者：
P. Fielitz;G. Borchardt
铝是地质和人造材料中的一种关键元素，它只有一种稳定的同位素，没有半衰期适合标准实验扩散研究的放射性核素。在这里，我们报告了我们使用放射性同位素26Al （t1/2 = 7.4×105 a）作为铝的准稳定示踪剂结合SIMS深度剖面的方法。首先，我们的a-氧化铝中铝体扩散系数的数据与已发表的氧体扩散系数进行了联合讨论。它们清楚地表明，在1200°C≤T≤1800°C的温度范围内，关系式DAl>>D0是有效的。以类似的方式，两种稀有的稳定同位素18O和30Si与26Al一起用于仅由铝、硅和氧组成的材料的一般例子的扩散研究，或者这三种元素是结构的关键成分。对于结晶铝硅酸盐莫来石，我们用铝、氧和硅的扩散系数数据来解释莫来石的固态生成反应动力学和氧化铝从莫来石中分离的动力学。最后，给出了不同Al3+/Na+比例下铝硅酸盐玻璃模型中氧和铝的扩散系数随温度的变化规律。对于硅酸铝莫来石和硅酸铝玻璃，D0>DAl>DSi关系是有效的，而不考虑其确切成分。在玻璃体系中，随着Al3+/Na+比值的减小，铝和氧的扩散活化焓减小。
Aluminium is a key element in geological and man-made materials which has only one stable isotope and no radionuclides with half-life times suitable for standard experimental diffusion studies. Here we report on our method using the radioisotope 26Al (t1/2 = 7.4×105 a) as a quasi-stable tracer for aluminium in combination with SIMS depth profiling. First, our data for the aluminium bulk diffusivity in a-alumina are discussed jointly with published oxygen bulk diffusion coefficients. They clearly show that the relation DAl>>D0 is valid in the temperature range 1200 °C ≤ T ≤ 1800 °C. In an analogous manner, the two rare stable isotopes 18O and 30Si are used together with 26Al in diffusion studies of generic examples of materials which either consist of aluminium, silicon and oxygen only, or where these three elements are key constituents of the structure. For the crystalline aluminium silicate mullite our diffusivity data for aluminium, oxygen and silicon are used to explain the kinetics of the solid state formation reaction of mullite and the segregation kinetics of alumina from mullite. Finally, the diffusivities of oxygen and aluminium in model aluminosilicate glasses are presented as a function of temperature for different Al3+/Na+ ratios. For the aluminium silicate mullite and for the aluminosilicate glasses the relation D0>DAl>DSi is valid regardless of the exact composition. For the glass system the activation enthalpies of aluminium and oxygen diffusion decrease with decreasing Al3+/Na+ ratio.