A review of the intrinsic ductility and toughness of hard transition-metal nitride alloy thin films

Abstract

Over the past decades, enormous effort has been dedicated to enhancing the hardness of refractory ceramic materials. Typically, however, an increase in hardness is accompanied by an increase in brittleness, which can result in intergranular decohesion when materials are exposed to high stresses. In order to avoid brittle failure, in addition to providing high strength, films should also be ductile, i.e., tough. However, fundamental progress in obtaining hard-yet-ductile ceramics has been slow since most toughening approaches are based on empirical trial-and-error methods focusing on increasing the strength and ductility extrinsically, with a limited focus on understanding thin-film toughness as an inherent physical property of the material. Thus, electronic structure investigations focusing on the origins of ductility vs. brittleness are essential in understanding the physics behind obtaining both high strength and high plastic strain in ceramics films. Here, we review recent progress in experimental validation of density functional theory predictions on toughness enhancement in hard ceramic films, by increasing the valence electron concentration, using examples from the V1-xWxN and V1-xMoxN alloy systems.

Tribological Properties of Mo2N Films at Elevated Temperature

“…A further increase in testing temperature decreases the average friction coefficient; the minimum average friction coefficient is 0.29 at 550 °C. Similar friction properties were also reported in other transition metal nitride films, such as TiAlVN [22], ZrAlN [23], and W-Si-N [5]. Figure 4 also presents the wear rate as a function of various testing temperatures.…”

“…It can be clearly observed that the testing temperature has a significant effect on the average friction coefficient. When the testing temperature is below 200 • C, the average friction coefficient increases from 0.30 at 25 • C to 0.53 at 200 • C. A further increase in testing temperature decreases the average friction coefficient; the minimum average friction coefficient is 0.29 at 550 • C. Similar friction properties were also reported in other transition metal nitride films, such as TiAlVN [22], ZrAlN [23], and W-Si-N [5]. Tribo-film is known to significantly influence the tribological properties of transition metal nitride films, since tribo-oxidation has been reported to be a generalized phenomenon [6,7,11].…”

“…Recently, Magnéli phases have been attracting an increasing level of interest due to their "easy sliding" crystallographic shear planes [1][2][3][4]. These phases were reported to reduce the average friction coefficient significantly [5][6][7]. For example, S.M.…”

Recent advances in biomass‐derived carbon, mesoporous materials, and transition metal nitrides as new electrode materials for supercapacitor: A short review

“…[39][40][41] Besides, TMN has a typical technical approach along with interesting mechanical properties. 42 The superior mechanical performance of TMNs is critical for the long-term life span of energy storage devices, making it favorable. The excellent mechanical support will mitigate the volume change during the reaction, where it will decrease the pulverization and stabilize the entire electrode.…”

“…43 It shows high volumetric capacitances and great cycling life as well as high rate of capability. 42 Besides, the raw materials for metal nitrides are lower in properties indicating that TMN is now a significant field of supercapacitor electrode materials. 44,45 The basic potential of metal nitrides is more significant in action compared to carbon and polymers.…”