New research sheds light on nature of friction in multi-layered graphene
New study provides insights into how surface structures influence
nanoscale friction in this promising 2D material

Date:
March 9, 2022
Source:
Pusan National University
Summary:
Multi-layered graphene is a promising carbon-based nanomaterial for
a variety of next-generation technologies, but the relationships
between its surface structures and properties are not entirely
clear. Now, in a recent study, scientists analyze how surface
structures like wrinkles and folded networks affect nanoscale
friction in multi-layered graphene.

Their findings could pave the way for graphene-based solid
lubricants and micro/nano-scale mechanical devices.



FULL STORY ========================================================================== Multi-layered graphene is a promising carbon-based nanomaterial for a
variety of next-generation technologies, but the relationships between
its surface structures and properties are not entirely clear. Now,
in a recent study, Pusan National University scientists analyze how
surface structures like wrinkles and folded networks affect nanoscale
friction in multi-layered graphene. Their findings could pave the way for graphene-based solid lubricants and micro/nano- scale mechanical devices.


========================================================================== Graphene, which consists of a single layer of carbon atoms, is the poster
child of carbon-based 2D nanomaterials. It has many attractive properties
that could be exploited in next-generation electronics, optics, catalysis, biomedicine, and many other fields. Recently, many scientists have focused
on chemical vapor deposition (CVD) as a cost-efficient technique for
producing larger graphene surfaces in lieu of the well-established method
of mechanical exfoliation, which can only produce small graphene islands.

However, CVD graphene contains a fair number of surface structures
and defects, including wrinkles, crystal grain boundaries, and surface contamination.

Because graphene is so thin, even minor surface irregularities can
greatly affect its properties, making its surface-property relationships
an important area of research. While studies on this topic have been
conducted extensively for single-layer CVD graphene, few have focused
on how surface structures affect the nanoscale friction characteristics
of multi-layered CVD graphene.

Recently, a team of researchers from Pusan National University,
Korea, led by Assistant Professor Songkil Kim tackled this knowledge
gap. "Correlating surface characteristics with a material's properties is really important," explains Dr. Kim, "Imagine you are stacking papers,
and there is a huge compressive strain over these papers. This could
cause massive structural deformations within the stacked layers and the surface. Similarly, the structural changes that occur in multi-layered
graphene can affect its surface properties, such as its friction, which
is what we focused on." Their paper was made available online on January
24, 2022, and published in Volume 584 of Applied Surface Scienceon May
15, 2022.

The team first used the atom-sized tip of an atomic force microscope
(AFM) to scratch the surface of CVD multi-layer graphene, cleaning off
any polymeric residues. Then, they used AFM imaging, friction force
microscopy, and Raman spectroscopy to identify and study various surface structures and how they affect nanoscale friction. Interestingly, they
found that only the top-most layer of graphene was twisted with respect
to the rest, which influenced the layer-dependent nanoscale friction in
a way that varied according to the applied load.

Overall, this study's findings could pave the way for interesting
mechanical applications for CVD graphene. "Graphene and similar materials
can be used as solid lubricants," comments Dr. Kim, "Whereas liquid
lubricants like motor oils are not suitable for harsh environment such as
outer space or the polar regions, the excellent robustness and frictional properties of graphene make it an attractive non-toxic alternative." Interestingly, developing high-performance lubricants has environmental benefits since reducing friction is essential to prevent energy losses in mechanical systems. Another potential application for multi-layered CVD graphene is in micro/nano-devices, where a precise control of friction
is necessary.


========================================================================== Story Source: Materials provided by Pusan_National_University. Original
written by Na-hyun Lee. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Min Gi Choi, Seonha Park, Habeom Lee, Songkil Kim. Correlating
surface
structures and nanoscale friction of CVD Multi-Layered
graphene. Applied Surface Science, 2022; 584: 152572 DOI:
10.1016/j.apsusc.2022.152572 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220309104411.htm

--- up 1 week, 2 days, 10 hours, 51 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)