This contribution aimed at developing a treatment under ammonia in order to eliminate free carbon from the surface of SiC-based fine ceramics like fibers or coatings. The reaction of NH₃ with graphitic and non-graphitic carbon was first investigated through kinetic measurements, in situ gas phase analysis and physicochemical investigations of the solid. The carbon etching rate is controlled by heterogeneous reactions involving active sites arising from bulk structural defects and the formation of HCN. A selection of SiC-based fibers and coatings with various carbon contents and (micro)structures was treated in ammonia in favorable conditions. The analyses of the tested SiC–C specimens revealed a reduction of the free carbon content and, simultaneously, a nitridation of the initial Si–C–(O) continuum over a reaction layer. The growth rate, composition and the volume change of this layer vary with the initial microstructure. The ammonia treatment is able to restore the adhesion of carbon-contaminated surfaces.

该贡献旨在开发一种在氨气下的处理工艺，以消除纤维或涂层等SiC基精细陶瓷表面的游离碳。首先通过原位动力学测量研究了NH ₃与石墨碳和非石墨碳的反应气相分析和固体的理化研究。碳蚀刻速率由异质反应控制，该异质反应涉及由整体结构缺陷和HCN的形成引起的活性位。在有利条件下，在氨气中处理了各种具有不同碳含量和（微）结构的SiC基纤维和涂层的选择。对测试的SiC-C样品的分析表明，游离碳含量降低了，同时，反应层上的初始Si-C-（O）连续体也被氮化了。该层的生长速率，组成和体积变化随初始微观结构而变化。氨处理能够恢复被碳污染的表面的附着力。