Reactive Molecular Simulation of the Damage Mitigation Efficacy of POSS-, Graphene-, and Carbon Nanotube-Loaded Polyimide Coatings Exposed to Atomic Oxygen Bombardment
Reactive Molecular Simulation of the Damage Mitigation Efficacy of POSS-, Graphene-, and Carbon Nanotube-Loaded Polyimide Coatings Exposed to Atomic Oxygen Bombardment
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DOI：
10.1021/acsami.7b02032
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发表时间：
2017-04-12
影响因子：
9.5
通讯作者：
Al-Ostaz, Ahmed
中科院分区：
文献类型：
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作者：
Rahmani, Farzin;Nouranian, Sasan;Al-Ostaz, Ahmed
采用反应分子动力学模拟来比较暴露于原子氧 (AO) 轰击的 PI 基质中原始和聚酰亚胺 (PI) 接枝的聚八面体倍半硅氧烷 (POSS)、石墨烯 (Gr) 和碳纳米管 (CNT) 的损伤减轻功效。进一步研究了 POSS 的浓度以及 Gr 和 CNT 纳米颗粒的取向。总体而言，与原始 POSS 或相同纳米颗粒浓度下排列的 CNT 和 Gr 系统相比，具有随机取向 CNT 和 Gr 或 PI 接枝 POSS 的 PI 系统的质量损失、侵蚀产率、表面损伤、AO 渗透深度和温度演变较低。根据实验早期降解数据（纳米颗粒损伤发生之前），材料表面暴露的PI（所有材料成分中侵蚀产率最高）的量是影响杂化材料侵蚀产率的最重要参数。我们的数据表明，具有随机取向的 Gr 和 CNT 纳米粒子的 PI 系统在材料表面上暴露的 PI 量最低；因此，与具有对齐的 Gr 和 CNT 纳米粒子的 PI 系统相比，这些系统获得的侵蚀率较低。然而，PI/接枝-POSS 系统的侵蚀率明显低于具有对齐 Gr 和 CNT 纳米颗粒的 PI 系统，这也是由于表面暴露的 PI 量较少。当在低和高纳米颗粒浓度下比较装载有 PI 接枝 POSS 的 PI 系统与原始 POSS 时，我们的数据表明，接枝 POSS 和增加 POSS 浓度分别将侵蚀率降低了约 4 倍和 1.S 倍。前者归因于 PI 接枝 POSS 与 PI 基质中原始 POSS 相比具有更好的分散性（由径向分布函数确定）。
Reactive molecular dynamics simulation was employed to compare the damage mitigation efficacy of pristine and polyimide (PI) -grafted polyoctahedral silsesquioxane (POSS), graphene (Gr), and carbon nanotubes (CNTs) in a PI matrix exposed to atomic oxygen (AO) bombardment. The concentration of POSS and the orientation of Gr and CNT nanoparticles were further investigated. Overall, the mass loss, erosion yield, surface damage, AO penetration depth, and temperature evolution are lower for the PI systems with randomly oriented CNTs and Gr or PI -grafted POSS compared to those of the pristine POSS or aligned CNT and Gr systems at the same nanoparticle concentration. On the basis of experimental early degradation data (before the onset of nanoparticle damage), the amount of exposed PI, which has the highest erosion yield of all material components, on the material surface is the most important parameter affecting the erosion yield of the hybrid material. Our data indicate that the PI systems with randomly oriented Gr and CNT nanoparticles have the lowest amount of exposed PI on the material surface; therefore, a lower erosion yield is obtained for these systems compared to that of the PI systems with aligned Gr and CNT nanoparticles. However, the PI/grafted-POSS system has a significantly lower erosion yield than that of the PI systems with aligned Gr and CNT nanoparticles, again due to a lower amount of exposed PI on the surface. When comparing the PI systems loaded with PI -grafted POSS versus pristine POSS at low and high nanoparticle concentrations, our data indicate that grafting the POSS and increasing the POSS concentration lower the erosion yield by a factor of about 4 and 1.S, respectively. The former is attributed to a better dispersion of PI -grafted POSS versus that of the pristine POSS in the PI matrix, as determined by the radial distribution function.