Lubricating Properties of Cyano-Based Ionic Liquids against Tetrahedral Amorphous Carbon Film

At a Glance

Metadata	Details
Publication Date	2020-02-08
Journal	Coatings
Authors	Shouhei Kawada, H. Ōkubo, Seiya Watanabe, Chiharu Tadokoro, Ryo Tsuboi
Institutions	Tokyo University of Science, Daido University
Citations	6
Analysis	Full AI Review Included

Technical Documentation & Sales Analysis: Cyano-Based Ionic Lubrication on Carbon Films

Documentation generated by 6CCVD Advanced Materials Engineering Team.

Executive Summary

The analyzed research details the investigation into the ultra-low friction characteristics of cyano-based Ionic Liquids (ILs) when applied to tetrahedral amorphous carbon (ta-C) films. This study is highly relevant to engineers developing next-generation tribological systems utilizing high-hardness CVD carbon materials, a specialty of 6CCVD.

Core Material Achievement: High-hardness ta-C films (73 GPa) were used as the base material for evaluating boundary lubrication under elevated temperature and load.
Performance Benchmark: The lubricant 1-butyl-3-methylimidazolium tricyanomethane ((BMIM)(TCC)) achieved an exceedingly low friction coefficient of 0.03 at a sliding temperature of 90 °C.
Mechanism Confirmation: Low friction behavior is directly linked to the thermally activated reaction of the IL. Raman spectroscopy confirmed that the reduction in friction proceeds concurrently with the graphitization of the ta-C film on the wear track.
Surface Chemistry: MALDI-TOF/MS analysis confirmed the selective adsorption of IL anions onto the worn ta-C surface at specific elevated temperatures (90 °C or 170 °C), indicating tribo-decomposition is critical for forming the effective lubricating layer.
Engineering Implication: The results confirm that high-purity, stable diamond films are ideal candidates for studying thermally activated boundary lubrication mechanisms in extreme environments, requiring materials with verifiable hardness and low intrinsic surface roughness.
6CCVD Advantage: 6CCVD’s ultra-high-hardness MPCVD SCD and PCD materials offer superior stability and performance characteristics for replicating or extending this research into higher-load and higher-temperature applications.

Technical Specifications

Extracted quantitative parameters relating to material properties and test conditions.

Parameter	Value	Unit	Context
Best Friction Coefficient (COF)	0.03	None	Achieved using (BMIM)(TCC) at 90 °C.
Second COF Result	0.07	None	Achieved using (BMIM)(DCN) at 170 °C.
ta-C Film Hardness	73	GPa	High hardness required for minimal substrate wear.
ta-C Film Thickness	1.0	µm	Coating applied via arc ion plating.
ta-C Surface Roughness (R_a)	0.01	µm	Pre-test surface finish (10 nm).
Sliding Test Load	50	N	Constant normal load applied by steel cylinder.
Reciprocating Frequency	50	Hz	Sliding speed parameter.
Heating Rate (Sweep Test)	10	K/5 min	Programmed temperature increase.
Viscosity (BMIM)(TCC) @ 50 °C	11.1	mPas	Physical property of the Ionic Liquid.
Decomposition Temp (BMIM)(TCC)	344	°C	TGA measured weight loss (~5%) in N₂ atmosphere.

Key Methodologies

A concise sequence of the experimental procedure used to evaluate the lubricating mechanisms of the cyano-based ionic liquids on ta-C films.

Material Deposition: Tetrahedral amorphous carbon (ta-C) films (1.0 µm thick, 73 GPa hardness) were deposited onto AISI 52100 steel disks and cylinders via arc ion plating, utilizing a Chromium (Cr) interlayer for adhesion.
Sample Preparation: Test specimens were rigorously cleaned via ultrasonic treatment in a 1:1 petroleum benzine and acetone solution for 10 minutes.
Lubrication Application: A precise volume (90 µL) of the test ionic liquid ((BMIM)(DCN) or (BMIM)(TCC)) was applied to the disk surface.
Reciprocating Sliding Test (SRV4): Tests were run under a 50 N load, 50 Hz frequency, and 1 mm amplitude, operating in an air atmosphere.
- Temperature Sweep: Initial tests swept the temperature from 30 °C to 290 °C (10 K/5 min) to determine the temperature of friction reduction.
- Constant Temperature Tests: Subsequent tests were conducted at the critical low-friction temperatures (90 °C for TCC, 170 °C for DCN) for 30 minutes to confirm stability.
Spectroscopic Analysis:
- Raman Spectroscopy (532 nm YAG laser): Used to calculate the I_D/I_G ratio in the worn surface, quantifying the degree of ta-C graphitization.
- MALDI-TOF/MS (Laser wavelength 337 nm): Employed in reflected mode to map and analyze the adsorption of specific IL anions (DCN = 66, TCC = 90) and cations (BMIM = 139) on the worn surface.
- TGA: Used to evaluate the intrinsic thermal stability of the ILs (30-500 °C in N₂ atmosphere) for comparison with tribo-decomposition kinetics.

6CCVD Solutions & Capabilities

This research highlights the critical role of high-purity, stable carbon films in enabling advanced boundary lubrication. 6CCVD specializes in providing engineered MPCVD diamond that offers superior performance and tailorability compared to the ta-C films used in this study.

Requirement/Observation (Paper)	6CCVD Material/Capability	Engineering Value Proposition
Material Foundation: ta-C (a form of DLC), 73 GPa Hardness.	Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD).	Our SCD (>100 GPa) and PCD (up to 125 mm wafers) provide maximum wear resistance and chemical inertness, establishing the most reliable platform for studying chemical reactions and tribo-decomposition at extreme loads.
Thickness Requirement: 1.0 µm film thickness.	Precise Thickness Control (SCD/PCD: 0.1 µm - 500 µm).	We provide precise control over the diamond layer thickness, whether ultra-thin films (e.g., 0.1 µm) for interfacial studies or thick substrates (up to 10 mm) for high-load durability tests.
Surface Quality: ta-C R_a = 0.01 µm (10 nm).	Ultra-Fine Polishing Service.	Achieve benchmark surface finishes: R_a < 1 nm for SCD and R_a < 5 nm for inch-size PCD plates, ensuring experimental reproducibility and allowing accurate measurement of boundary lubrication phenomena without surface roughness interference.
Substrate/Interface: ta-C coated on steel using a Cr interlayer.	Custom Metalization and Hybrid Materials.	6CCVD offers internal metalization services (Au, Pt, Ti, W, Cu, Pd) crucial for optimizing adhesion, thermal sinking, and creating specialized electrical contacts for advanced sensor integration or heating elements in tribology rigs.
Application Extension: Need for high-temperature stability (tested up to 290 °C).	Diamond Substrates for Extreme Environments.	Leverage diamond’s intrinsic wide bandgap and thermal stability to extend tribological testing well beyond the limits of amorphous carbon (ta-C), enabling IL and coating evaluations in temperatures exceeding 500 °C.

Applicable Materials for Advanced Tribology

To replicate or extend this research into higher-performance regimes, 6CCVD recommends:

Optical Grade SCD (0.1 µm to 500 µm): For ultimate hardness, chemical inertness, and ultra-smooth surfaces (R_a < 1 nm), ideal for fundamental studies of anion adsorption and graphitization mechanisms.
High-Density PCD Plates (Up to 125 mm): For scaling up wear tests or creating large-format tribological components capable of sustained high load applications.
Boron-Doped Diamond (BDD): Use BDD films to introduce controlled electronic conductivity for potential in-situ electrochemical or thermal analysis of the lubricant interaction film.

Customization Potential & Engineering Support

6CCVD’s advanced processing capabilities—including wafers up to 125 mm, custom laser cutting for precise cylinder/disk geometries, and integrated metalization—allow researchers to move beyond typical DLC limits. Our in-house PhD team can assist with material selection and specification development for projects focused on High-Performance Boundary Lubrication and Extreme Environment Tribology.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. 6CCVD offers global shipping (DDU default, DDP available) to ensure timely delivery of your research-grade materials.

View Original Abstract

Ionic liquids have unique characteristics, which render them ideal candidates as new base oils or additives. In particular, there are great expectations from the combination of diamond-like carbon and cyano-based ionic liquids. Lubricating properties of cyano-based ionic liquids have been studied on specific tetrahedral amorphous carbon (ta-C) films. After lubrication, ta-C film/ta-C film contact interface exhibits exceedingly low friction. Therefore, it is necessary to understand this low friction phenomenon. The current study evaluated the lubricating mechanism of cyano-based ionic liquids against ta-C films. 1-Butyl-3-methylimidazolium dicyanamide ((BMIM)(DCN)) and 1-butyl-3-methylimidazolium tricyanomethane ((BMIM)(TCC)) were used as lubricants, with the latter exhibiting low friction coefficient of 0.03. Steel cylinders and disks with ta-C films were used as test specimens. Raman spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and thermogravimetric analysis (TGA) helped us understand the mechanism of low friction induced by (BMIM)(TCC). Graphitization of the ta-C film at high temperatures might have caused the reduction in friction between the films. Similarly, anion adsorption on the worn surface at high temperatures also led to reduced friction. However, the TGA result showed a different trend than that of the sliding test. Our results indicate that the cyano-based ionic liquids underwent tribo-decomposition at low temperatures. Further, a minimum temperature was required for the adsorption of anions onto the sliding surface.

Tech Support

Original Source

DOI: https://doi.org/10.3390/coatings10020153

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