不同退火温度下a-C:Si涂层的热稳定性研究

目的在碳化硅基底上制备a-C:Si涂层,通过分析涂层在不同退火温度下的热稳定性机制,拓宽其在高温领域的应用。方法采用非平衡磁控溅射法在碳化硅表面沉积a-C:Si涂层,并进行不同温度的退火热处理,通过XPS、SEM、拉曼光谱对涂层进行表征与分析。利用分子动力学对a-C:Si涂层退火过程进行仿真,从涂层与原子结构、原子径向分布函数、配位数、键长及键角等多方面对涂层石墨化行为进行分析。通过仿真与实验数据的交叉分析,探究a-C:Si涂层热稳定性机制。结果a-C:Si涂层主要由C、Si元素组成,且碳原子之间主要形成sp2和sp3两种杂化键,其中sp3键居多,随退火温度的上升,其相对含量下降。a-C:Si涂层的拉曼光谱在400~500℃时出现明显的D峰,ID/IG积分强度比和G峰峰值具有相似的变化趋势。退火温度升高时,涂层中键长较长的sp3-sp3键最先开始向sp2-sp2转化,随着退火温度的升高,键长较短的sp3-sp3键才开始变化。石墨化过程中,sp3-sp3键转化率最大,Si与C形成高热稳定性的Si—C键。结论退火处理对a-C:Si涂层的热稳定性有重要影响,退火温度为400℃时,a-C:Si涂层开始发生石墨化转变。Si元素能稳定原子结构,与Si成键的C-sp3杂化原子具有更高的热稳定性,降低了石墨化的速率。

Thermal Stability of a-C:Si Coating at Different Annealing Temperature

The work aims to prepare a-C:Si coating on silicon carbide substrate and widen the applications of the in high-temperature fields by analyzing its thermal stability mechanism at different annealing temperature.The a-C:Si coating was deposited on the surface of silicon carbide by unbalanced magnetron sputtering,and annealed at different temperature.The coating was characterized and analyzed by XPS,SEM and Raman spectroscopy.The annealing process of a-C:Si coating was simulated by molecular dynamics,and the graphitization behavior of the coating was analyzed from the coating and atomic structure,atomic radial distribution function,coordination number,bond length and bond angle.The thermal stability mechanism of a-C:Si coating was also explored by the cross-analysis of the simulation and experiment data.From the research results,the a-C:Si coating mainly consisted of C and Si elements.Two hybrid bonds of sp2 and sp3 were formed among the carbon atoms.The sp3 bonds were dominant,and their relative content decreased with the increase in the annealing temperature.The Raman curve of a-C:Si coating showed a distinct D peak at 400~500℃,and the change trends of ID/IG integrated intensity ratio and G peak value were similar.The simulation results showed that when the annealing temperature increased,the sp3-sp3 bond with a longer bond length in the coating firstly began to transform to the sp2-sp2 bond.As the annealing temperature increased,the sp3-sp3 bond with a shorter bond length began to change.Among them,the sp3-sp3 bond had the highest conversion rate,and Si and C formed the Si-C bond with high thermal stability.The annealing has an important effect on the thermal stability of a-C:Si coating.When the annealing temperature is 400℃,the a-C:Si coating begins to graphitize.Si can stabilize the atomic structure,and C-sp3 bonded to Si possesses higher thermal stability,which also reduces the rate of graphitization.