Understanding SiOC atomic structures via synchrotron X-ray and reactive force field potential studies
Understanding SiOC atomic structures via synchrotron X-ray and reactive force field potential studies
复制标题
DOI：
10.1016/j.mtchem.2023.101429
复制
发表时间：
2023-04
影响因子：
7.3
通讯作者：
H. Chaney;Y. Zhou;K. Lu
中科院分区：
文献类型：
--
作者：
H. Chaney;Y. Zhou;K. Lu
碳氧化硅（SiOC）是一种独特的系统，可以通过不同的聚合物前体和热解条件产生各种成分和微观结构。然而，对原子结构演化的理解，如团簇形成，相演化和原子配位，缺乏。采用高能X射线衍射（HE-XRD）和径向分布函数（RDF）分析方法研究了不同SiOC陶瓷在1200 °C和1500 °C热解时的团簇演化和原子配位。提出了一种新的反应力场（ReaxFF）分子动力学模拟方法来理解纳米团簇分离和早期原子径向配位。首次证明了正交SiO2的形成和转变为抗生长的无定形SiO2。立方β-SiC也在比报道的温度低的温度下形成，沿着形成少量从未报道过的六方SiC。RDF数据支持这样的阶段演化理解。ReaxFF模拟提供了关于原子混合、元素分离以及前体分子结构和组成的影响的直接数据，特别是在热解的早期阶段。模拟的RDF数据补充了实验数据，揭示了C-H键沿着Si-O和C-C键的显著存在。
Silicon oxycarbide (SiOC) is a unique system that can generate various compositions and microstructures via different polymeric precursors and pyrolysis conditions. However, understanding of the atomic structure evolution, such as cluster formation, phase evolution, and atomic coordination, is lacking. In this study, cluster evolution and atomic coordination for different SiOC ceramics pyrolyzed at 1200 °C and 1500 °C were investigated by high energy X-ray diffraction (HE-XRD) and radial distribution function (RDF) analysis. A new Reactive Force Field (ReaxFF) molecular dynamics modeling approach was developed to understand nanocluster separation and early-stage atomic radial coordination. For the first time, we demonstrate that orthorhombic SiO2forms and converts to growth resistant amorphous SiO2. Cubic β-SiC also forms at lower temperatures than reported, along with a minor amount of hexagonal SiC that has never been reported. The RDF data support such phase evolution understanding. ReaxFF simulation provides direct data on atomic mixing, elemental separation, and effects of precursor molecular structures and compositions, especially in the early stage of the pyrolysis. The simulated RDF data complement the experimental data, revealing the significant presence of C–H bonds along with Si–O and C–C bonds.