Metastable SiCN glass matrices studied by energy-filtered electron diffraction pattern analysis
Metastable SiCN glass matrices studied by energy-filtered electron diffraction pattern analysis
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DOI：
10.1016/j.jnoncrysol.2007.06.003
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发表时间：
2007-10
影响因子：
3.5
通讯作者：
H. Störmer;H. Kleebe;G. Ziegler
中科院分区：
文献类型：
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作者：
H. Störmer;H. Kleebe;G. Ziegler
块状 SiCN 玻璃源自具有定制结构的聚合物前体，在 1000°C 下热解并随后在 1400°C 和 1540°C 下退火进行表征。采用的表征工具是高分辨率透射电子显微镜 (HRTEM) 成像和能量过滤选区电子衍射 (EF-SAED)。这项工作的主要重点是验证聚合物衍生的本体材料的固有无定形结构在热解时是否表现出不同的结构特征，这取决于陶瓷前体聚合物的功能性，以及这些特征在高温退火后是否保持。 HRTEM 成像没有显示出不同 SiCN 玻璃结构在 1000°C 有机-无机转变后，甚至在 1400°C 热处理后，没有任何明显的变化。然而，EF-SAED 分析显示，即使在 1000°C 热解后，所研究的四种聚合物衍生 SiCN 玻璃的无定形结构也存在差异。随后在高温下进行热处理后，EF-SAED 图案的电子衍射强度分布的演变表明，在超过热解温度的温度下退火时，SiCN 玻璃网络内的结构重排的明显证据。实验结果证明，聚合物衍生的 SiCN 陶瓷的亚稳态玻璃结构取决于所用的起始聚合物，此外，固有的玻璃结构会影响无定形基体的热稳定性（结晶开始）。
Bulk SiCN glasses, derived from polymer precursors with tailored architectures, were characterized upon pyrolysis at 1000°C and subsequent annealing at 1400°C and 1540°C. The characterization tools employed were high-resolution transmission electron microscopy (HRTEM) imaging and energy-filtered selected area electron diffraction (EF-SAED). Main emphasis of this work was to verify as to whether the intrinsic amorphous structure of polymer-derived bulk materials exhibits different structural features upon pyrolysis, that depend on the functionalities of the pre-ceramic polymer, and whether such characteristic features are maintained upon high-temperature anneal. HRTEM imaging did not reveal any pronounced variation between the different SiCN glass structures after the organic–inorganic transition at 1000°C or even upon heat treatment at 1400°C. However, EF-SAED analysis showed differences in the amorphous structure of the four polymer-derived SiCN glasses studied even upon thermolysis at 1000°C. The evolution of the electron diffraction intensity profiles of the EF-SAED patterns after subsequent thermal treatment at elevated temperatures showed clear evidence of structural rearrangements within the SiCN glass networks upon annealing at temperatures exceeding the pyrolysis temperature. The experimental results provide evidence that the metastable glass structure of polymer-derived SiCN ceramics depends on the starting polymer employed and, in addition, that the intrinsic glass architecture affects the thermal stability (onset of crystallization) of the amorphous matrix.