Fatigue behavior of freestanding nickel-molybdenum-tungsten thin films with high-density planar faults.

This research addresses the fatigue behavior of freestanding nickel-molybdenum-tungsten (Ni-Mo-W) thin films with high-density planar faults. The as-deposited Ni-Mo-W thin films demonstrate an unprecedented fatigue life, withstanding over a million cycles at a Goodman stress amplitude () of 2190 MPa - nearly 80% of the tensile strength. The texture, columnar grain width, planar fault configuration (spacing and orientation), and tensile strength were unchanged after annealing at 500 °C for 24 hours, and the film endured over 2 × 10 cycles at of 1050 MPa.

Nanotwinned metal MEMS films with unprecedented strength and stability.

Silicon-based microelectromechanical systems (MEMS) sensors have become ubiquitous in consumer-based products, but realization of an interconnected network of MEMS devices that allows components to be remotely monitored and controlled, a concept often described as the "Internet of Things," will require a suite of MEMS materials and properties that are not currently available. We report on the synthesis of metallic nickel-molybdenum-tungsten films with direct current sputter deposition, which results in fully dense crystallographically textured films that are filled with nanotwins. These films exhibit linear elastic mechanical behavior and tensile strengths exceeding 3 GPa, which is unprecedented for materials that are compatible with wafer-level device fabrication processes.

Superstrength through Nanotwinning.

The theoretical strength of a material is the minimum stress to deform or fracture the perfect single crystal material that has no defects. This theoretical strength is considered as an upper bound on the attainable strength for a real crystal. In contradiction to this expectation, we use quantum mechanics (QM) simulations to show that for the boron carbide (BC) hard ceramic, this theoretical shear strength can be exceeded by 11% by imposing nanoscale twins.

Kinetic Role of Carbon in Solid-State Synthesis of Zirconium Diboride using Nanolaminates: Nanocalorimetry Experiments and First-Principles Calculations.

Reactive nanolaminates afford a promising route for the low-temperature synthesis of zirconium diboride, an ultrahigh-temperature ceramic with metallic properties. Although the addition of carbon is known to facilitate sintering of ZrB2, its effect on the kinetics of the formation reaction has not been elucidated. We have employed a combined approach of nanocalorimetry and first-principles theoretical studies to investigate the kinetic role of carbon in the synthesis of ZrB2 using B4C/Zr reactive nanolaminates.

Tensile characteristics of metal nanoparticle films on flexible polymer substrates for printed electronics applications.

Metal nanoparticle solutions are widely used for the fabrication of printed electronic devices. The mechanical properties of the solution-processed metal nanoparticle thin films are very important for the robust and reliable operation of printed electronic devices. In this paper, we report the tensile characteristics of silver nanoparticle (Ag NP) thin films on flexible polymer substrates by observing the microstructures and measuring the electrical resistance under tensile strain.