Views: 222 Author: Lake Publish Time: 2025-03-22 Origin: Site
Content Menu
● Thermal Conductivity of Boron Carbide
>> 1. Unirradiated Boron Carbide
>>> Key Factors Affecting Thermal Conductivity:
>> 2. Impact of Neutron Irradiation
● Electrical Conductivity of Boron Carbide
>> 2. Compositional Dependence
● Applications Leveraging Conductivity
● FAQ
>> 1. Is boron carbide a good thermal conductor?
>> 2. What Are the Properties of Boron Carbide?
>> 3. Can boron carbide conduct electricity?
>> 4. How can boron carbide's electrical conductivity be improved?
>> 5. Is boron carbide used in electronics?
Boron carbide (B4C) is a ceramic material renowned for its extreme hardness, neutron absorption capability, and resistance to wear. However, its thermal and electrical conductivity properties are complex and often debated. This article explores whether boron carbide conducts heat and electricity, supported by experimental data, theoretical models, and industrial applications.
Unirradiated boron carbide exhibits moderate thermal conductivity due to its crystalline structure. At room temperature, its thermal conductivity ranges between 28–90 W/(m·K) depending on purity and density (see Table 1). This makes it suitable for heat dissipation in nuclear reactors and armor systems.
- Purity: High-purity B4C (>99%) achieves ~90 W/(m·K).
- Density: Fully dense sintered ceramics conduct heat better than porous variants.
- Temperature: Conductivity decreases at elevated temperatures due to phonon scattering.
Table: Thermal Conductivity of Boron Carbide
| Condition | Thermal Conductivity (W/m·K) |
|---|---|
| Unirradiated (RT) | 28–90 |
| Irradiated (35×1026 cap/m³) | 2–4 |
| Annealed (post-irradiation) | 10–15 |
Under fast neutron irradiation, boron carbide's thermal conductivity drops sharply due to defects:
- Substitutional Defects: Neutron collisions replace boron atoms with lithium, disrupting lattice vibrations.
- Frenkel Pairs: Vacancies and interstitial atoms scatter phonons, reducing conductivity by ~90% at 35×10⊃2;⁶ captures/m³.
Boron carbide is a p-type semiconductor with an energy bandgap of 2.09 eV. Its electrical conductivity depends on temperature and composition:
- Low Temperature (5–100 K): Conductivity follows Mott's variable-range hopping (VRH) model.
- High Temperature (>500 K): Thermally activated conduction dominates, with activation energies of 0.1–0.3 eV.
- Hopping Transport: Electrons "hop" between localized states in the bandgap.
- Bipolaron Model: Paired electrons move as a single entity, though recent studies favor VRH.
Carbon-rich boron carbide (e.g., B4.3C) shows higher conductivity due to increased carrier density. For example:
| Composition | Electrical Conductivity (S/m at 300 K) |
|---|---|
| B<sub>4</sub>C | 10-4–10-2 |
| B<sub>4.3</sub>C | 10-1–101 |
- Control Rods: B4C's neutron absorption and moderate thermal conductivity help manage reactor heat.
- Shielding: Degraded conductivity post-irradiation necessitates active cooling systems.
- High-Temperature Sensors: B4C's Seebeck coefficient (~250 µV/K) enables energy harvesting in harsh environments.
- Heat Dissipation: Conductivity prevents localized overheating during projectile impact.
1. Defect Engineering: Mitigate irradiation damage via nanostructuring or composite designs (e.g., B4C-SiC).
2. Doping Strategies: Enhance electrical conductivity with carbon nanotubes or metallic additives.
3. Hybrid Systems: Integrate B4C with high-conductivity materials like graphene for thermoelectric applications.
Boron carbide is a poor conductor of heat and electricity compared to metals but exhibits unique semiconductor properties. Its thermal conductivity is moderate initially but degrades severely under neutron irradiation. Electrically, conduction occurs via hopping or thermal activation, with resistivity highly dependent on composition. Advances in defect engineering and composite design could unlock its potential in next-generation nuclear and thermoelectric systems.
Irradiation introduces defects like Frenkel pairs and lithium substitutions, which scatter phonons and block heat transfer.
Boron carbide is known for its hardness and resistance to chemical corrosion. It is used in various applications, including armor and abrasives.
Yes, but weakly. It behaves as a semiconductor with resistivity ranging from 104to 1011 Ω·m depending on purity and temperature.
Doping with TiB2 or carbon additives enhances carrier density, reducing resistivity to 10-2–102 Ω·m.
Rarely, due to high resistivity. However, its thermoelectric properties are explored for high-temperature sensors.
[1] https://d-nb.info/1257742906/34
[2] https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4075476
[3] https://journals.sagepub.com/doi/full/10.1080/17436753.2019.1705017
[4] https://www.makeitfrom.com/material-properties/Boron-Carbide-B4C
[5] https://en.wikipedia.org/wiki/Boron_carbide
[6] https://www.americanelements.com/boron-carbide-12069-32-8
[7] https://onlinelibrary.wiley.com/doi/pdf/10.1002/pssa.2210150270
[8] https://www.azom.com/properties.aspx?ArticleID=75
[9] https://arxiv.org/pdf/1601.06828.pdf
[10] https://www.preciseceramic.com/blog/boron-carbide-key-properties-applications.html
