The fundamentals of hard and superhard nanocomposites and heterostructures

The original nding of Veprek and Reiprich that in nc-TiN/a-Si3N4 and related nanocomposites, deposited under the optimum conditions that allow a complete phase segregation, and provided the impurity content is about 100 ppm or less, a maximum hardness of =50 to more than 100 GPa is achieved when the thickness of the interfacial SiNx phase is about 1 monolayer (1 ML), has been recently conrmed both theoretically and experimentally. In this chapter, we summarize these results and discuss the thermodynamic and kinetic limitations of experiments on heterostructures and nanocomposites. In Section 1.1, we discuss generally what are strong, hard, and superhard materials, and 1.1 Introduction: What Is a “Strong” and “Superhard” Material?. 2 1.2 Extrinsically Superhard Nano-Sized and Nano-Structured Materials 6.