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首页> 外文期刊>Propellants, Explosives, Pyrotechnics >On the Mechanism of Low Temperature Oxidation for Aluminum Particles down to the Nano-Scale
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On the Mechanism of Low Temperature Oxidation for Aluminum Particles down to the Nano-Scale

机译：铝颗粒低温氧化至纳米尺度的机理研究

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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 A1_2O_3 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 10nm 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 um,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 um build gamma-and theta-Al_2O_3 in the first step with nano-crystalline structures which are then transformed to alpha-Al_2O_3.
机译：通过TG，SEM和原位X射线衍射研究了Al颗粒的氧化至纳米级。Al颗粒通常被2-4 nm的Al_2O_3涂层覆盖，这可以从重量增加的程度得出Al颗粒的低温氧化至少分两步进行：第一步是形成6至10nm厚度的层，该层由大小与初始粒径无关的微晶组成。由化学动力学主导，如果粒径减小到1 um以下，则会转化很大一部分颗粒，出于安全原因，应仔细考虑纳米颗粒的影响。第二步将扩散和化学反应结合起来，因此缓慢进行越慢，颗粒越大。这两个步骤的动力学参数可以通过模型来获得，该模型同时考虑了反应步骤，化学动力学和球形颗粒的扩散。 X射线衍射表明，小于1 um的颗粒在第一步中形成具有纳米晶体结构的γ-和theta-Al_2O_3，然后将其转变为α-Al_2O_3。

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