Abrasive wear damages observation in engineering ceramics using micro-Raman tomography

At a Glance

Metadata	Details
Publication Date	2022-12-31
Journal	Journal of Advanced Mechanical Design Systems and Manufacturing
Authors	Teppei Onuki, Kazuki Kaneko, Hirotaka Ojima, Jun Shimizu, Libo ZHOU
Institutions	Ibaraki University
Analysis	Full AI Review Included

Technical Documentation & Analysis: Precision Diamond Surfaces for Advanced Raman Tomography

This document analyzes the research paper “Abrasive wear damages observation in engineering ceramics using micro-Raman tomography” and connects the findings directly to 6CCVD’s capabilities in MPCVD diamond material science, specifically focusing on how high-quality Single Crystal Diamond (SCD) and Polycrystalline Diamond (PCD) surfaces can overcome the optical limitations identified in ceramic materials.

Executive Summary

The study validates Micro-Raman Tomographic Imaging (mRTI) for subsurface wear damage analysis in ceramics but highlights critical limitations related to optical diffusion in polycrystalline materials. 6CCVD’s ultra-precision diamond materials directly address these limitations, enabling deeper, more accurate spectroscopic analysis.

Core Challenge: Optical diffusion in polycrystalline ceramics (Alumina) severely restricts the effective mRTI measurement depth (initially 4-8 µm).
Solution Demonstrated: Precision surface polishing using diamond abrasives (#800) reduced surface roughness ($R_a$) from 600 nm to 200 nm, significantly reducing light diffusion.
Key Achievement: Optimized polishing extended the effective measurement depth range across the full 17 µm scan depth, confirming the necessity of superior surface quality.
Material Superiority: The paper notes that single-crystal materials (like sapphire, analogous to 6CCVD’s SCD) achieved deeper penetration (up to 20 µm) even with rougher surfaces, confirming the optical advantage of single-crystal structures.
6CCVD Value Proposition: We provide SCD and PCD materials with guaranteed surface roughness (R_a < 1 nm for SCD), eliminating the optical diffusion issues that plague polycrystalline ceramics and ensuring maximum effective measurement depth for advanced spectroscopic techniques.
Critical Process Control: The research emphasizes that polishing must be optimized to reduce diffusion without overwriting the original wear damage—a requirement met by 6CCVD’s precision mechanical polishing capabilities.

Technical Specifications

The following hard data points were extracted from the mRTI experiment and material characterization:

Parameter	Value	Unit	Context
Sample Material Purity	96	%	Commercial Alumina Ceramic (Al₂O₃)
Initial Surface Roughness (R_a)	600	nm	Arithmetic average roughness of initial surface
Polished Surface Roughness (#400) (R_a)	300	nm	Achieved via #400 diamond lapping film
Polished Surface Roughness (#800) (R_a)	200	nm	Achieved via #800 diamond lapping film
Initial Max Measurable Depth	4 to 8	µm	Limited by light diffusion in polycrystalline material
Improved Max Measurable Depth	17	µm	Effective over entire scan range after #800 polishing
Raman Peak Used (Alumina)	417	cm^-1	Corresponds to A_1g vibration mode
Laser Wavelength	532	nm	mRTI measurement condition
Laser Power	10	mW	mRTI measurement condition
Confocal Aperture	25	µm	Pin hole diameter
Grating Density	1800	lines/mm	Spectral resolution approximately 2 cm^-1
Objective Lens Numerical Aperture (NA)	0.9	N/A	Magnification x100
Exposure Time per Point	16	sec.	Required for high-resolution 2D depth-slice scanning
Refractive Index (Alumina)	1.76	N/A	Used for depth correction in mRTI scanning

Key Methodologies

The experiment focused on evaluating the influence of surface quality on mRTI depth penetration in polycrystalline ceramics.

Sample Selection: Commercial alumina ceramic plates (96% purity, 20 mm x 20 mm x 1 mm) were used as the measurement samples.
Initial Characterization: Surface topography and roughness (R_a ≈ 600 nm) were measured using an optical surface profiler (Zygo New View 2000).
Surface Treatment Simulation: Three surface conditions were prepared: initial surface, polished with #400 diamond abrasive lapping film, and polished with #800 diamond abrasive lapping film. Polishing was performed by hand for 15 minutes.
mRTI Setup: A DXR Raman microscope (Thermo Fisher Scientific) was utilized, employing a 532 nm laser at 10 mW power, focused through a NA 0.9 objective lens.
Data Acquisition: Raman spectra were acquired using a 25 µm confocal pinhole and an 1800 lines/mm grating, with a 16-second exposure time per point.
Depth-Slice Scanning: 2D scanning was conducted over a 24 µm horizontal range (1 µm pitch) and a 17 µm depth range (0.85 µm pitch, corrected using the alumina refractive index of 1.76).
Damage Quantification: Tomographic images were generated by fitting the Raman spectra to the Lorentzian function, extracting peak intensity, peak width (indicating crystal lattice disorder), and peak shift (indicating residual strain/stress).

6CCVD Solutions & Capabilities

The research confirms that surface quality is the primary limiting factor for deep subsurface analysis using optical techniques like mRTI in polycrystalline materials. 6CCVD’s expertise in growing and finishing high-purity MPCVD diamond provides the ideal platform for replicating and extending this research into high-performance materials.

Applicable Materials

Material	Application Focus	Technical Rationale
Optical Grade Single Crystal Diamond (SCD)	Advanced Spectroscopic Windows, High-Resolution mRTI Substrates, Quantum Sensing	SCD is the ultimate single-crystal material. Unlike polycrystalline alumina, SCD exhibits negligible light diffusion, maximizing the effective measurement depth (analogous to the superior performance noted for single-crystal sapphire).
Polycrystalline Diamond (PCD)	Industrial Wear Components, Large-Area Tribology Studies, High-Hardness Substrates	Ideal for replicating the high-wear conditions studied. Our PCD can be polished to R_a < 5 nm across inch-sized wafers, providing a superior, low-diffusion surface compared to the 200 nm achieved on alumina.
Boron-Doped Diamond (BDD)	Electrochemical Sensing, Conductive Wear Studies	If the research were extended to include electrical or electrochemical wear mechanisms, BDD offers high conductivity combined with diamond’s extreme hardness and chemical inertness.

Customization Potential for Spectroscopic Research

The paper highlights the critical need for precision mechanical polishing using diamond abrasives. 6CCVD specializes in this exact process, ensuring materials are delivered ready for high-sensitivity optical measurement.

Research Requirement	6CCVD Customization Capability
Ultra-Low Roughness Surfaces	We guarantee SCD surfaces with R_a < 1 nm and large-area PCD surfaces with R_a < 5 nm. This level of polish is essential to minimize surface light scattering and maximize mRTI depth penetration.
Custom Dimensions & Thickness	We offer PCD plates up to 125 mm in diameter and custom SCD/PCD thicknesses ranging from 0.1 µm to 500 µm, allowing researchers to design components or substrates precisely for their experimental setup.
Integrated Metalization	For applications requiring electrical contacts or thermal management (e.g., integrated heating elements for wear testing), we offer in-house metalization (Au, Pt, Pd, Ti, W, Cu) patterned to custom specifications.
Damage-Free Preparation	Our in-house processing ensures that laser cutting and polishing are performed under optimized conditions, preventing the introduction of residual strain or lattice damage that could “overwrite” the wear damage being studied, as cautioned by the authors.

Engineering Support

6CCVD’s in-house PhD team provides expert consultation to ensure material selection and preparation are optimized for demanding optical and spectroscopic applications. We can assist researchers in defining the optimal surface finish and material grade (SCD vs. PCD) required for similar subsurface wear damage analysis projects, guaranteeing that the material itself does not become the limiting factor in measurement depth or signal quality.

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

View Original Abstract

Micro Raman tomographic imaging (mRTI) is an excellent measurement technique that can nondestructively measure and image the fracture state of the crystal lattice inside materials with a high spatial resolution. mRTI has been successfully used for translucent materials such as wide bandgap semiconductor wafers. The applicability of this measurement method was evaluated by observing the wear damage in polycrystalline industrial ceramics materials. The influence of optical diffusion on the surface and inside of polycrystalline materials is a concern for the internal measurements by the optical beam. The quality degradation of spectral signals due to disturbances in the optical beam was confirmed by mRTI measurements on a commercial alumina plate. The application of surface polishing treatment was attempted to reduce the influence of surface optical diffusion. Three kinds of the surfaces were observed by mRTI, as the initial surface of the alumina plate, polished with #400 and #800 diamond abrasive lapping film, respectively. It was confirmed that the effective measurement depth range can be extended by reducing the surface roughness. However, we confirmed that excessive surface polishing may overwrite the damage on the measurement surface, making it difficult to observe the original damage.

Tech Support

Original Source

DOI: https://doi.org/10.1299/jamdsm.2023jamdsm0009