Phase Formation, Microstructure and Mechanical Properties in Mixed Metal/Silicon Carbide Films

在本研究计画中，将研究混合过渡金属碳化物/碳化硅薄膜的结构与机械性质。 金属碳化物和SiC之间的强化学不相容性以及低温沉积工艺的使用将促进异相纳米尺度微结构的形成。 在这些薄膜中的相的形成和微观结构的演变的基本机制，特别强调的结构附近形成的渗滤阈值的a-SiC的金属碳化物的晶界上，将被检查。 表征方法将包括高分辨率透射电子显微镜和X射线光电子能谱。 此外，表面与体相扩散过程的模型将用于合理化所观察到的微观结构，包括相分离的观察。 还将研究这些薄膜的机械性能，特别是通过观察压痕后存在的微观变形结构来研究这些薄膜中的变形机制。最近的研究报告的机械性能的混合金属氮化物/氮化硅薄膜的纳米级异质结构声称显着的性能增强，包括硬度水平超过金刚石和高断裂韧性。 制造硬度高于金刚石的材料的能力是材料科学家长期以来的追求。 如果这一目标能够实现，它将允许在诸如切削工具和轴承涂层等应用方面取得重大进展。 在这项研究计划中，我们将研究过渡金属碳化物/碳化硅涂层，类似于氮化物系统，最近的研究兴趣的主题。 使用先进的表征和测试方法，沿着热力学和动力学建模，我们希望能够更好地理解这些材料的强化机制，沿着用于改进工业涂层的新候选陶瓷材料。

In this research program the structural and mechanical properties of mixed transition metal carbide/silicon carbide thin films will be studied. The strong chemical immiscibility between the metallic carbides and SiC, as well as the use of low-temperature deposition processes will promote the formation of heterophase nano-scale microstructures. Fundamental mechanisms of phase formation and microstructural evolution in these films, with particular emphasis on the structures formed near the percolation threshold of a-SiC on the grain boundaries of the metallic carbides, will be examined. Characterization methods will include high-resolution transmission electron microscopy and x-ray photoelectron spectroscopy. In addition, models of surface vs. bulk diffusion processes will be used to rationalize the observed microstructures, including observations of phase separation. The mechanical properties of these films, particularly the deformation mechanisms operating in these films by observing the microscopic deformation structure present after indentation, will also be investigated.%%%Recent research reports on the mechanical properties of mixed metal nitride/silicon nitride thin films with nano-scale heterophase structures have claimed dramatic property enhancements, including hardness levels exceeding that of diamond and high fracture toughness. The ability to create materials with hardness levels above that of diamond is a long-standing quest for materials scientists. If this objective can be achieved, it would allow significant advances in applications such as coatings for cutting tools and bearings. In this research program we will study transition metal carbide/silicon carbide coatings that are analogous to the nitride systems that have been the subject of much recent research interest. Using advanced characterization and testing methods, along with thermodynamic and kinetic modeling, we hope to achieve an improved understanding of strengthening mechanisms in these materials, along with new candidate ceramic materials for improved industrial coatings.***