Mechano-Chemical Interaction in Ultrafast Reactions of Solid Reactants

Hendrik J. Viljoen教授将研究机械激励下的非均相化学反应。将开发新的宏观模型来解释激波和反应区内的非平衡能量分布，考虑平动、旋转和振动模式、混合和超音速过渡之间的能量分布。分子动力学将用于模拟反应区的原子行为，分布连续统动力学方程将原子模型纳入宏观行为。这些原子宏观模型可用于描述低温化学自传播反应；机械合金化和声化学作为降低反应点火温度和活化能的技术；固体激波引起的反应，其中化学反应的能量必须转化为平动能以维持激波。作者将从分子动力学的角度研究激波作用下硫与铝微晶间的超快反应。为了建立连续介质模型，他们将模拟超过Hugoniot弹性极限的高压，并在经典守恒方程中加入描述孔隙崩塌和固体压实的方程。最后，通过识别临界能量交换模式并对交换模式的特征时间积分，将分子动力学和连续统模型相匹配。该基金由动力学和催化以及过程和反应工程项目资助。

Prof. Hendrik J. Viljoen will study heterogenous chemical reactions under mechanic excitation. New macroscopic models will be developed to account for non-equilibrium energy distribution within shock and reaction zones, considering energy distribution among translational, rotation, and vibrational modes, mixing, and supersonic transitions. Molecular dynamics will be used to simulate atomistic behavior in the reaction zone, and distributed continuum dynamics equations will incorporate the atomic model into the macroscopic behavior. These atomistic-macroscopic models may find applications in the description of cryochemical self-propagating reactions; mechanical alloying and sonochemistry as techniques to reduce ignition temperatures and activation energies for reaction; shock-induced reactions of solids, in which chemical reaction energy must be transformed into translational energy in order to sustain the shock wave. The authors will investigate by molecular dynamics the ultrafast reaction between sulfur and aluminum microcrystallites subjected to a shock wave. To develop the continuum model, they will simulate high pressures above the Hugoniot elastic limit, and add equations describing pore collapse and solid compaction to the classical conservation equations. Finally, the molecular dynamics and continuum models will be matched by identifying the critical energy exchange modes and integrating over the characteristic times for the exchange modes. This grant is being funded by the Kinetics and Catalysis and the Process and Reaction Engineering programs.