How Good Are the Performances of Graphene and Boron Nitride Against the Wear of Copper?

At a Glance

Metadata	Details
Publication Date	2021-02-28
Journal	Materials
Authors	Min Kang, Hai Woong Park, Arnaud Caron
Institutions	Korea University of Technology and Education
Citations	4
Analysis	Full AI Review Included

Technical Documentation & Analysis: CVD Diamond in Nanoscale Tribology

Executive Summary

This documentation analyzes the tribological performance study of Graphene and Boron Nitride (BN) coatings on copper, highlighting the critical role of high-stiffness CVD diamond materials in nanoscale metrology and protective applications.

Core Application: Investigation of wear-protective effects of 2D materials (Graphene, h-BN) on soft metals (Copper) using Friction Force Microscopy (FFM).
Metrology Tooling: The study relied on a stiff, diamond-coated AFM tip (Et = 700 GPa) to apply controlled normal forces (up to 6930 nN), confirming the necessity of ultra-hard CVD materials for high-precision nanoscale mechanical testing.
Superior Wear Protection: Hexagonal Boron Nitride (h-BN) demonstrated significantly superior wear resistance compared to Graphene, reducing the average wear depth from 30 nm (bare Cu) to 9 nm.
Load-Bearing Capacity: BN retarded the onset of plastic deformation (plowing) in the copper substrate, increasing the critical normal force (F_ny) by over 300% (from 989 nN for bare Cu to 3066 nN for BN/Cu).
Mechanism Validation: The enhanced wear protection of BN is directly attributed to its larger out-of-plane stiffness, which increases its load-bearing capacity and resistance to being stamped into the substrate.
6CCVD Relevance: This research validates the market need for high-modulus Single Crystal Diamond (SCD) materials for advanced AFM tips, indenters, and durable protective coatings in miniaturized components (MEMS/NEMS).

Technical Specifications

Data extracted from the tribological testing and material characterization sections of the research paper.

Parameter	Value	Unit	Context
Test Temperature (T)	293	K	Standardized laboratory conditions
Relative Humidity (RH)	40	%	Controlled dehumidified environment
Normal Force Range (F_n)	15 - 6930	nN	Range of successive sliding tests
Scan Area (A_s)	2.5 x 2.5	µm²	Area of repeated reciprocal sliding
Sliding Velocity (v_s)	20	µm/s	AFM tip speed
Tip Material	Diamond-coated	N/A	Stiff AFM cantilever (CDT-NCLR)
Tip Young’s Modulus (E_t)	700	GPa	Used for JKR model calculations
Bare Copper Wear Onset (F_ny)	989	nN	Critical force for plowing activation
Graphene/Cu Wear Onset (F_ny)	1507	nN	Retardment of plastic deformation
BN/Cu Wear Onset (F_ny)	3066	nN	Maximum retardment observed
Bare Copper Wear Depth (δ_w)	30	nm	Average depth of worn area
BN/Copper Wear Depth (δ_w)	9	nm	Lowest observed wear depth (highest protection)
Graphene/Cu Friction Coeff. (μ)	0.112	N/A	Wear-less regime (puckering mechanism)
BN/Cu Friction Coeff. (μ)	0.1989	N/A	Wear-less regime (higher due to stiffness)

Key Methodologies

The experiment combined advanced CVD synthesis of 2D materials with high-resolution AFM metrology, relying on ultra-stiff diamond tooling.

Substrate Preparation: Cold-rolled copper foil was annealed at 1300 K in an Ar/H₂ mixture to provide a baseline substrate for comparison.
2D Material Synthesis: Monolayer Graphene and Hexagonal Boron Nitride (h-BN) were prepared on the copper foil using Chemical Vapor Deposition (CVD) methods (BN synthesis at 1300 K).
Surface Characterization (XPS): X-ray Photoelectron Spectroscopy (XPS) was used to confirm the presence and chemical state of the coatings (e.g., C1s sp² peak for Graphene, B1s and N1s peaks for BN). Gentle Ar⁺ sputtering was used only on bare copper to remove adventitious carbon contamination without damaging the 2D coatings.
Tribological Testing (FFM): Friction Force Microscopy (FFM) was conducted using an AFM XE-100 under controlled conditions (T=293 K, RH=40%). A stiff, commercial diamond-coated AFM cantilever (CDT-NCLR) was used as the indenter.
Wear Protocol: Wear tests involved repeated reciprocal sliding over a 2.5 x 2.5 µm² area, with normal forces successively increased from 15 nN to 6930 nN.
Data Modeling: Friction forces (<F_f>) in the low-load (wear-less) regime were fitted using the Johnson-Kendall-Roberts (JKR) model, while the high-load (plowing) regime was analyzed using linear fits to determine the onset of plastic deformation (F_ny).

6CCVD Solutions & Capabilities

This research demonstrates the critical need for ultra-hard, high-modulus materials, specifically CVD diamond, for both advanced metrology (AFM tips) and high-performance protective coatings in miniaturized systems. 6CCVD is uniquely positioned to supply the materials required to replicate, extend, and commercialize this research.

Research Requirement	6CCVD Solution & Capability	Technical Advantage
Ultra-Stiff Indenters (Diamond-coated AFM tip, E_t = 700 GPa)	Optical Grade Single Crystal Diamond (SCD)	6CCVD SCD offers Young’s Modulus approaching 1000 GPa, providing superior stiffness and durability for high-load nanoscale indentation and FFM tips, ensuring reliable data acquisition in the plowing regime.
Large-Scale Substrates (For scaling up MEMS/NEMS protection)	Polycrystalline Diamond (PCD) Wafers	We supply PCD plates up to 125mm in diameter, suitable for large-area deposition of protective layers or for use as robust, wear-resistant substrates in industrial tribology applications.
High-Precision Surface Finish (Required for nanoscale metrology)	Advanced Polishing Services	6CCVD guarantees ultra-low roughness: SCD polished to R_a < 1 nm and inch-size PCD polished to R_a < 5 nm. This minimizes parasitic friction and roughness effects observed in the paper’s R_q measurements.
Custom Device Integration (Metalization for bonding/electrodes)	In-House Metalization Capabilities	We offer custom metal stacks (Au, Pt, Pd, Ti, W, Cu) to facilitate integration of diamond components into micro-devices, enabling robust electrical contacts or bonding layers required for complex MEMS/NEMS structures.
Thickness Control (Required for studying film mechanics)	Precise CVD Thickness Control	6CCVD provides SCD and PCD layers with thicknesses ranging from 0.1 µm (relevant to thin-film mechanics) up to 500 µm, allowing researchers to precisely control the mechanical response of the diamond layer.

Engineering Support

6CCVD’s in-house PhD engineering team specializes in the mechanical, thermal, and electronic properties of MPCVD diamond. We can assist researchers in selecting the optimal diamond grade (e.g., high-purity SCD for maximum stiffness or Boron-Doped Diamond (BDD) for electro-tribology studies) and custom dimensions required for similar nanoscale friction and wear projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

We investigate the copper-wear-protective effects of graphene and boron nitride in single asperity sliding contact with a stiff diamond-coated atomic force microscopy (AFM)-tip. We find that both graphene and boron nitride retard the onset of wear of copper. The retardment of wear is larger with boron nitride than with graphene, which we explain based on their respective out-of-plane stiffnesses. The wear protective effect of boron nitride comes, however, at a price. The out-of-plane stiffness of two-dimensional materials also determines their friction coefficient in a wear-less friction regime. In this regime, a higher out-of-plane stiffness results in larger friction forces.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma14051148

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