Observation of enhanced nanoscale creep flow of crystalline metals enabled by controlling surface wettability

Abstract

Understanding and controlling interface friction are central to many science and engineering applications. However, frictional sliding is closely related to adhesion, surface roughness, surface chemistry, mechanical deformation of contact solids, which poses the major challenge to experimental studying and theoretical modeling of friction. Here, by exploiting the recent developed thermomechanical nanomolding technique, we present a simple strategy to decouple the interplay between surface chemistry, plastic deformation, and interface friction by monitoring the nanoscale creep flow of metals in nanochannels. We show that superhydrophobic nanochannels outperforming hydrophilic nanochannels can be up to orders of magnitude in terms of creep flow rate. The comparative experimental study on pressure and temperature dependent nanomolding efficiency uncovers that the enhanced creep flow rate originates from diffusion-based deformation mechanism as well as the superhydrophobic surface induced boundary slip. Moreover, our results reveal that there exists a temperature-dependent critical pressure below which the traditional lubrication methods to reduce friction will break down. Our findings not only provide insights into the understanding of mechanical deformation and nanotribology, but also show a general and practical technique for studying the fundamental processes of frictional motion. Finally, we anticipate that the increased molding efficiency could facilitate the application of nanoimprinting/nanomolding.

Observation of a Large Slip Effect in the Nanoscale Flow of Highly Viscous Supercooled Liquid Metals

“…Figure e shows that the larger the contact angle, the longer the molded metallic glass nanorods, on the basis of which the effect of surface tension can be ruled out because the surface tension-induced additional pressure usually prevents the metallic glass from entering the nanopore (Figure S1; see Surface tension effect in TMNM in the Supporting Information for details). The nanocavities are very smooth (with a root-mean-square roughness of ∼0.370 nm) and show negligible changes after silanization coating (with a root-mean-square roughness of ∼0.356 nm) . Therefore, we attribute the drastically increased flow rate in our experiments to the intrinsic boundary slippage enabled by silanization treatment. − …”

“…The nanocavities are very smooth (with a rootmean-square roughness of ∼0.370 nm) and show negligible changes after silanization coating (with a root-mean-square roughness of ∼0.356 nm). 43 Therefore, we attribute the drastically increased flow rate in our experiments to the intrinsic boundary slippage enabled by silanization treatment. 37−39 On the basis of the strategy depicted in Figure 1, the effects of nanochannel size and temperature on the slip length of Pt-BMG can be readily investigated.…”

Wafer‐Scale Fabrication of 2D Nanostructures via Thermomechanical Nanomolding

“…In addition, differences in crystal structure (fcc Al and Cu and bct In), diffusivity, and surface energies lead to different molding conditions. [ 19 ] There is a slight pressure increase necessary to mold nc‐Cu (30 MPa), µc‐Cu (60 MPa), and sc‐Cu (70 MPa). The lack of any consistent grain orientation in nc‐Cu, the presence of grains in partially molded samples, and comparable grain size in molded Cu with grain size in the bulk feedstock indicate that the microstructure of the feedstock is conserved during molding.…”

Coating-Free Superhydrophobic Hard Surfaces by Electric Discharge Machining with a Magnetic-Assisted Self-Assembly Sheet Electrode

“…The utilization of replication technology founded on robust mold structures is a facile and well-established strategy for the mass production of superhydrophobic products. − Binderless WC and glasses are two typical hard-brittle ceramic materials that are extensively employed in many industrial applications due to their excellent physical-chemical properties. Cemented carbides exhibit excellent hardness and superior wear resistance due to the tungsten carbide phase, making them widely applicable as pressing molds and cutting tools .…”