Exploring the reaction mechanism in self-propagating Al/Ni multilayers by adding inert material
Exploring the reaction mechanism in self-propagating Al/Ni multilayers by adding inert material
复制标题
DOI：
10.1016/j.combustflame.2016.07.006
复制
发表时间：
2016-10-01
影响因子：
4.4
通讯作者：
Weihs, Timothy P.
中科院分区：
文献类型：
--
作者：
Grapes, Michael D.;Weihs, Timothy P.
我们提出了一类新的反应材料，称为“惰性介导的反应多层膜”(IMRMS)，它使用惰性材料来分离反应多层膜中化学和最高温度的影响。详细说明了在选择IMRM中活性和惰性材料的成分和厚度时应考虑的重要因素。然后我们给出了我们用23 nm双层1：1 Al：Ni反应截面和2：3Cu：Ni惰性截面制备的一组特定的IMRM样品的结果。在这些样品中，我们观察到随着反应材料体积分数的减少，反应热、最高反应温度和反应传播速度都有系统地降低。同时，对反应机理和产物敏感的指标表明，在任何样品中，惰性物质和活性物质之间几乎没有交叉污染。这表明，IMRM样品都经历了相同的净反应(Al/Ni->；Ali)，但在不同的火焰温度范围内(大约1950 K到1300 K)。利用已有的火焰温度与传播速度关系的理论模型，对实验数据进行了分析，得到了混合过程的活化能，发现随着最高反应温度的变化，活化能变化很大。在较高的反应温度下，我们观察到很低的活化能(26kJ/mol)，这表明Ni在熔融Al中的扩散是速率控制混合机制，这与其他关于非介导型Al/Ni反应多层膜的研究结论一致。然而，随着反应温度的降低，活化能似乎移动到更大的值，这意味着反应机理的改变。我们假设，这种转变表明，在这些温度下，固体产物能够在反应中更早地形成，从而阻碍了原子的扩散和混合。(C)2016年，燃烧研究所。爱思唯尔公司出版，版权所有。
We present a new class of reactive materials termed "inert-mediated reactive multilayers" (IMRMs) that use inert material to decouple the effects of chemistry and maximum temperature in a reactive multi layer. Important considerations in the selection of composition and thickness for reactive and inert material in an IMRM are detailed. We then present the results from a specific set of IMRM samples that we fabricated using 23-nm-bilayer 1:1 Al:Ni reactive sections and 2:3 Cu:Ni inert sections. In these samples we observe a systematic reduction of heats of reaction, maximum reaction temperatures, and reaction propagation velocities as the volume fraction of reactive material is reduced. At the same time, metrics sensitive to the reaction mechanism and products indicate that there is little if any cross-contamination between inert and reactive material in any of the samples. This indicates that the IMRM samples all undergo the same net reaction (Al/Ni -> AINi) but at a range of different flame temperatures (roughly 1950 K to 1300 K). Using existing theoretical models for the relationship between flame temperature and propagation velocity, we analyze the experimental data to obtain the activation energy for the mixing process and find that this value varies significantly as the maximum reaction temperature changes. At high reaction temperatures we observe a very low activation energy (26 kJ/mol) which suggests diffusion of Ni in molten AI is the rate controlling mixing mechanism in agreement with the conclusions of other studies focused on un-mediated Al/Ni reactive multilayers. However, as the reaction temperature decreases the activation energy appears to shift to much larger values implying a change in the reaction mechanism. We postulate that this shift indicates that solid products are able to form earlier in the reaction at these temperatures, impeding atomic diffusion and intermixing. (C) 2016 The Combustion Institute. Published by Elsevier Inc. All rights reserved.