On the mechanism of low temperature oxidation for aluminum particles down to the nano-scale
On the mechanism of low temperature oxidation for aluminum particles down to the nano-scale
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DOI：
10.1002/prep.200400045
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发表时间：
2004-06-01
影响因子：
1.8
通讯作者：
Weiser, V
中科院分区：
文献类型：
--
作者：
Eisenreich, N;Fietzek, H;Weiser, V
利用热重分析（TG）、扫描电镜（SEM）和原位x射线衍射（xrd）研究了al颗粒氧化至纳米级的过程。铝颗粒表面通常包裹有一层2 ~ 4nm的Al2O3层，这可以从tg曲线上完全氧化后的重量增加程度得出。铝颗粒的低温氧化至少分两个步骤进行。第一步是建立一个6到10纳米厚度的层，由相同大小的晶体组成，与初始粒度无关。该反应由化学动力学主导，如果颗粒尺寸小于1 μ m，则会转化相当一部分颗粒，由于安全原因，纳米颗粒需要仔细考虑这一效应。第二步结合了扩散和化学反应，因此进行得很慢，颗粒越大越慢。这两个步骤的动力学参数可以通过一个同时考虑反应步骤、化学动力学和球形颗粒扩散的模型拟合到tg曲线上得到。x射线衍射表明，小于1 μ m的粒子在第一步以纳米晶结构生成α - al2o3和α - al2o3。
The oxidation of Al-particles down to nano-scale was investigated by TG, SEM and in-situ X-ray diffraction. Al particles are usually coated by a 2 - 4 nm layer of Al2O3 which can be derived from the degree of weight increase on complete oxidation by TG-curves. The low temperature oxidation of Al particles occurs at least in two steps. The first step builds a layer of 6 to 10 nm thickness composed of crystallites of the same size independent on the initial particle size. This reaction is dominated by chemical kinetics and converts a substantial fraction of the particle if the particle sizes decrease below 1 mum, an effect carefully to be taken into account for nano-particles because of safety reasons. The second step combines diffusion and chemical reaction and proceeds therefore slowly, the slower the bigger the particles are. The kinetic parameters of these two steps can be obtained by a model taking into account both reaction steps, chemical kinetics and diffusion for spherical particles when fitting it to TG-curves. X-ray diffraction shows that particles smaller than 1 mum build gamma-and theta-Al2O3 in the first step with nano-crystalline structures which are then transformed to alpha-Al2O3.