Theoretical Insight Into Diamond Doping and Its Possible Effect on Diamond Tool Wear During Cutting of Steel
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-12-14 |
| Journal | Frontiers in Materials |
| Authors | Hao Li, Sergei Manzhos, Zhijun Zhang |
| Institutions | State Key Laboratory of Chemobiosensing and Chemometrics, Tokyo Institute of Technology |
| Citations | 3 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis study utilizes ab initio calculations to analyze the mechanical and thermodynamic effects of Ga, B, and He doping on diamond cutting tools, specifically targeting the reduction of chemical wear during ferrous metal machining.
- Chemical Wear Mitigation: Substitutional Gallium (Ga) doping is the most effective strategy, thermodynamically inhibiting the graphitization of the diamond surface when exposed to diffusing Iron (Fe) atoms.
- Graphitization Inhibition: Ga-doped diamond requires a positive energy input (+2.49 eV) to form the second graphene-like layer, demonstrating superior stability compared to pristine (-3.26 eV released) or B/He doped systems.
- Surface Stability Enhancement: All three dopants reduce the diamond surface energy (up to 9.44% for Ga on the (110) face), increasing surface stability and potentially reducing interaction wear.
- Mechanical Softening: Doping introduces strain energy, leading to a reduction in the bulk modulus (mechanical softening). Boron (B) doping causes the least softening (422.94 GPa), maintaining high mechanical integrity.
- Doping Configuration: Substitutional doping is strongly preferred for Ga and B (lower formation energy), while interstitial doping is preferred for the inert element Helium (He).
- B and He Drawback: Despite improving surface stability, B and He doping make the diamond surface more susceptible to graphitization, potentially accelerating chemical wear compared to Ga.
Technical Specifications
Section titled âTechnical SpecificationsâData extracted from DFT calculations on pristine and doped diamond systems (64 C atoms).
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Pristine Bulk Modulus (B) | 434.47 | GPa | Pure diamond reference |
| Least Softening (BS) | 422.94 | GPa | Substitutional B doping |
| Most Softening (GaI) | 398.30 | GPa | Interstitial Ga doping |
| Highest Strain Energy (HeS) | 16.06 | eV | Substitutional He doping (inert element displacement) |
| Graphitization Energy Release (Pristine, 1st layer) | -2.42 | eV | Energy released upon initial graphitization |
| Graphitization Energy Required (Ga, 2nd layer) | +2.49 | eV | Energy barrier required to form the second graphene layer (Inhibition) |
| Maximum Surface Energy Decrease | 9.44 | % | Ga-doped (110) surface compared to pristine |
| Substitutional Ga Formation Energy (Ef) | 4.94 | eV | Energy required to incorporate Ga into the lattice |
| C-C Bond Length (Ga doped substrate) | 1.539 | Angstrom | Shorter bond length observed after Fe diffusion, indicating structural rigidity |
Key Methodologies
Section titled âKey MethodologiesâThe study relied on ab initio simulations using Density Functional Theory (DFT) to model the mechanical and thermodynamic behavior of doped diamond.
- Simulation Software and Method: Calculations were performed using the Vienna Ab Initio Simulation Package (VASP) employing the Projector-Augmented Plane-Wave (PAW) method.
- Functional and Cutoff: The Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional was used, with a kinetic energy cutoff of 520 eV for the plane wave basis set.
- Cell Structure: A conventional standard cubic diamond cell containing 64 C atoms (7.14 A x 7.14 A x 7.14 A) was used for bulk property calculations.
- Convergence Criteria: Strict convergence criteria were applied: 1 x 10-6 eV for electronic energy and 0.01 eV/A for force convergence.
- Bulk Modulus Assessment: Bulk moduli (BM) were calculated by applying isotropic compression and expansion to the simulation cell volume by -0.5, -0.1, 0.1, and 0.5%.
- Wear Simulation (Graphitization): The diamond (111) surface (5.05 A x 5.05 A, 64 C atoms) with a 15 A vacuum layer was constructed. Fe atoms were introduced to simulate adsorption and diffusion through the top two bilayers to assess the thermodynamic susceptibility to graphitization.
- Binding Energy Calculation (Ebind): Calculated to quantify the affinity of Fe atoms to the doped diamond surface, relating lower Ebind to reduced cutting tool wear.
Commercial Applications
Section titled âCommercial ApplicationsâThe findings provide critical theoretical guidance for the design and manufacturing of high-performance diamond cutting tools, particularly for applications involving materials that typically cause rapid chemical wear.
- Ultra-Precision Machining of Ferrous Alloys: Directly addresses the primary limitation of diamond toolsâchemical wear (graphitization) when cutting iron, steel, and other ferrous metalsâby validating Ga doping as a wear-inhibiting strategy.
- Advanced Tool Manufacturing: Provides parameters for optimizing doping techniques (e.g., ion implantation or CVD synthesis) to ensure dopants are incorporated substitutionally (Ga, B) or interstitially (He) for maximum benefit.
- Micro- and Nano-Machining: Essential for applications requiring extremely sharp, long-lasting tools for complex geometries and micro-features, where tool failure due to chemical wear is costly.
- Wear-Resistant Coatings: The principles of surface energy reduction and graphitization inhibition could be applied to the design of wear-resistant diamond-like carbon (DLC) coatings.
- Semiconductor Processing: Relevant to the development of diamond tools used for ductile mode cutting of silicon and other hard materials, where tool integrity is paramount.
View Original Abstract
Natural diamond tools experience wear during cutting of steel. As reported in our previous work, Ga doping of diamond has an effect on suppressing graphitization of diamond which is a major route of wear. We investigate interstitial and substitutional dopants of different valence and different ionic radii (Ga, B, and He) to achieve a deeper understanding of inhibiting graphitization. In this study, ab initio calculations are used to explore the effects of three dopants that might affect the diamond wear. We consider mechanical effects via possible solution strengthening and electronic effects via dopant-induced modifications of the electronic structure. We find that the bulk modulus difference between pristine and doped diamond is clearly related to strain energies. Furthermore, boron doping makes the resulting graphite with stable sp2 hybridization more perfect than diamond, but Ga-doped diamond needs 2.49 eV to form the two graphene-like layers than only one layer, which would result in the suppressed graphitization and reduced chemical wear of the diamond tool.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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