Boron-doped diamond growth on carbon fibre - Enhancing the electrical conductivity
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-01-08 |
| Journal | Applied Surface Science |
| Authors | Josué Millån-Barba, Hicham Bakkali, Fernando Lloret, M. Gutiérrez, Roberto Guzmån de Villoria |
| Institutions | IMEC, Foundation for the Research Development and Application of Composite Materials |
| Citations | 5 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research focuses on enhancing the electrical conductivity of carbon fibers (CF) using a polycrystalline Boron Doped Diamond (BDD) coating deposited via Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD).
- Core Problem Addressed: Carbon Fiber Reinforced Polymers (CFRP) suffer from high electrical anisotropy; transversal conductivity is two orders of magnitude poorer than longitudinal conductivity.
- Macro-Scale Achievement (Kelvin Method): The BDD coating successfully reduced the electrical resistance of a CF tow set by at least half compared to the uncoated CF.
- Estimated BDD Conductivity: The electrical conductivity of the BDD layer was estimated to be in the order of 103 Ω-1mm-1, significantly higher than the uncoated CF (58.8 Ω-1mm-1).
- Local-Scale Achievement (C-AFM): Local surface conductivity of the BDD-coated CF increased by an order of magnitude compared to uncoated CF filaments.
- Structural Confirmation (sMIM): Scanning Microwave Impedance Microscopy (sMIM) confirmed the BDD coating forms a rigid, conductive ring-like structure around the CF core, supporting the creation of a transverse conductive path.
- Doping Levels: Successful BDD layers exhibited boron concentrations ranging from 2 x 1021 cm-3 to 5 x 1021 cm-3.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Uncoated CF Conductivity (Macro) | 58.8 ± 0.2 | Ω-1mm-1 | Measured via Kelvin method. |
| Estimated BDD Layer Conductivity | 103 | Ω-1mm-1 | Calculated based on Kelvin results and Raman spectroscopy. |
| Boron Doping Concentration (Range) | 2 - 5 x 1021 | cm-3 | Achieved in samples G2 through G7. |
| BDD Coating Thickness (G4 Sample) | 104 | nm | Estimated using cross-sectional SEM micrographs. |
| BDD Coating Area (G3 Sample) | 22,510 | ”m2 | Maximum diamond growth area estimated by SEM. |
| C-AFM Peak Current (BDD-CF) | 2.08 | ”A | Local surface current response (order of magnitude increase). |
| C-AFM Peak Current (Uncoated CF) | 0.36 | ”A | Local surface current response. |
| sMIM-R Voltage Peak (BDD Coating) | 1.30 | V | Resistive signal peak, confirming BDD is the most conductive phase. |
| sMIM-R Voltage Peak (CF Core) | 0.25 | V | Resistive signal peak for the carbon fiber core. |
Key Methodologies
Section titled âKey MethodologiesâThe BDD coating was deposited on 12,000-filament carbon fiber tows (Hexcel AS7) using a Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD) system.
MPCVD Growth Conditions (Optimized for Sample G4)
Section titled âMPCVD Growth Conditions (Optimized for Sample G4)â| Parameter | Value | Unit |
|---|---|---|
| Microwave Power | 3.5 | kW |
| Pressure | 40 | Torr |
| Hydrogen (H2) Flow | 455 | sccm |
| Methane (CH4) Flow | 5 | sccm |
| Trimethylborane (TMB) Flow | 40 | sccm |
| Deposition Time | 600 | min |
Characterization Techniques
Section titled âCharacterization Techniquesâ- Kelvin Method (Macro-Scale):
- Used a 2-wire setup on CF tows fixed on insulating glass.
- Measured resistance along various lengths to determine bulk electrical conductivity (longitudinal direction).
- Conductive Atomic Force Microscopy (C-AFM) (Micro-Scale):
- Performed on single CF filaments fixed on a mica disc.
- Used diamond-coated tips (CDT-NCHR) at a sample bias of +500 mV.
- Mapped topography and current to assess local surface conductivity and granular structure.
- Scanning Microwave Impedance Microscopy (sMIM) (Cross-Sectional):
- CF filaments were embedded upright in epoxy resin and polished to expose the cross-section.
- Operated at microwave frequencies (around 3 GHz).
- Mapped the resistive signal (sMIM-R) to differentiate the conductivity of the resin, CF core, and BDD coating, confirming the core-shell structure.
- Raman Spectroscopy:
- Confirmed the diamond phase (sp3 peak) and the presence of the boron dopant (Boron band at 1200 cm-1).
- Used to estimate the boron concentration levels in the BDD layer.
Commercial Applications
Section titled âCommercial ApplicationsâThe successful reduction of electrical anisotropy and enhancement of transverse conductivity in CFRP materials opens new possibilities for high-specification engineering applications.
- Structural Fields:
- Lightning Strike Protection: Improved transverse conductivity allows for better dissipation of electrical energy, crucial for aircraft and wind turbine blades.
- Electromagnetic Shielding (EMI): Enhanced conductivity across the composite stack improves shielding effectiveness.
- Aeronautical and Transport:
- Manufacturing of lighter, stronger, and electrically functional composite components for aerospace and automotive sectors.
- Biomedical Applications:
- BDD is biocompatible and electrochemically stable, making BDD-CF suitable for advanced sensing electrodes or structural components in medical devices.
- Heating Elements:
- The conductive BDD coating can be used to create integrated heating elements within the composite structure for de-icing or thermal management.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2013 - Advanced composite materials of the future in aerospace industry [Crossref]
- 2017 - A review on utilization of textile composites in transportation towards sustainability [Crossref]
- 2013 - The Application of Carbon Fiber Materials in Sports Equipment [Crossref]
- 2019 - Multifunctional application of carbon fiber reinforced polymer composites: Electrical properties of the reinforcing carbon fibers - A short review [Crossref]
- 2008 - A Study of Electrical Conductivity Improvement of Carbon-Fiber Reinforced Plastics by Conductive Nano-Particles Coating
- 2014 - Surface Treatment of Carbon Fibers - A Review [Crossref]
- 2014 - Carbon fiber surfaces and composite interphases [Crossref]
- 2015 - Improving the through-thickness thermal and electrical conductivity of carbon fibre/epoxy laminates by exploiting synergy between graphene and silver nano-inclusions [Crossref]
- 2018 - Through-thickness thermal conductivity enhancement and tensile response of carbon fiber-reinforced polymer composites [Crossref]