Abstract A char layer is the first barrier against the ablation of insulation materials because it is the first to be subjected to thermal-chemical ablation and particle and gas-mechanical erosion. To study the ablation mechanism of the char layer in depth and to develop accurate models of the ablation phenomenon, the structural characteristics of the char layer must be understood. In this work, the structural characteristics of the char layer were studied using an ablation motor and several other analytical techniques. It was found that the char layer usually has a compact/porous structure with a compact surface. But in alumina deposition mode, the middle portion remains relatively compact. A mechanism whereby the compact layer is formed by re-deposition of the pyrolysis gas in the char layer skeleton, which is initially relatively porous, is proposed to explain the formation of the compact/porous structure. It was found that a liquid silica film contributes to the formation of the compact layer; this explains the formation of the porous/compact/porous structure. The gas-pyrolysis-based deposition which forms the surface compact layer can be regarded as being a self-reinforcing mechanism and can be exploited to improve the ablation resistance of insulation materials.

中文翻译：

---

三元乙丙绝缘材料炭层致密/多孔结构特征及形成机制

摘要 炭层是绝缘材料烧蚀的第一道屏障，因为它最先受到热化学烧蚀以及颗粒和气体机械侵蚀。为了深入研究炭层的烧蚀机制并开发烧蚀现象的准确模型，必须了解炭层的结构特征。在这项工作中，使用烧蚀电机和其他几种分析技术研究了炭层的结构特征。发现炭层通常具有致密/多孔结构和致密表面。但在氧化铝沉积模式下，中间部分保持相对紧凑。通过热解气体在炭层骨架中重新沉积形成致密层的机制，炭层骨架最初是相对多孔的，建议解释致密/多孔结构的形成。发现液态二氧化硅膜有助于致密层的形成；这解释了多孔/致密/多孔结构的形成。形成表面致密层的基于气体热解的沉积可被视为一种自增强机制，可用于提高绝缘材料的抗烧蚀性。