Bioinspired Nanoheterogeneous Alternating Multiarched Architecture: Toward a Superior Strength-Toughness Integration.

Strength and toughness are at odds with each other in coating design. Constructing strength-toughness-integrated coatings has long been a pursuit in materials design but is a challenge to achieve. Conventional wisdom suggests that growth of coatings is only a uniform cumulative growth on a two-dimensional plane. However, by constructing growth templates and controlling the alternation of heterogeneous materials, it subverts the traditional perception of cumulative growth in planes and creates the fact that the coating grows on a curved surface. Regulating the microstructure of the coating autonomously and matching the strength and toughness of heterogeneous materials, drawing inspiration from the multiarched structure in the nacre of red abalone, are crucial for achieving strength-toughness integration. Herein, we propose a new idea of coating deposition to achieve strength-toughness integration via preconstructing a nanoscale island-like discontinuous seed layer as a template for coating growth and then growing a nanoscale hard/soft heterogeneous multiarched architecture in situ. We refer to this architecture with intrinsic mechanical advantage as the "Nanoheterogeneous Alternating Multiarched" (NHAM) architecture. We design a nacre-like multiarched coating with a strength of 12.42 GPa and a value of 2.12 MPa·m, depositing the hard phase (TiSiCN layer) and the soft phase (Ag layer) with the unique NHAM architecture via physical vapor deposition technology, which exhibits a superior improvement in the strength-toughness integration compared to that reported in other studies (increased strength by at least 1 GPa without sacrificing toughness). The NHAM architecture strategy provides a pathway to design strength-toughness-integrated coatings. Two heterogeneous materials with well-matched strength and toughness can be deposited to achieve the NHAM architecture to greatly reflect the effect of strength-toughness integration.