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Updated: Jul 12, 2025
06:45
Negative Additive Manufacturing of Complex Shaped Boron Carbides
Published on: September 18, 2018
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Phase Transitions in Boron Carbide.
1Faculty of Physics, University Duisburg-Essen, D-47048 Duisburg, Germany.
Materials (Basel, Switzerland)
|October 28, 2023
Summary
Boron carbide undergoes phase transitions due to structural changes. Phonon spectroscopy reveals these transitions, which are influenced by carbon atom distribution within the icosahedra.
Area of Science:
- Materials Science
- Solid-State Physics
- Chemistry
Background:
- Boron carbide (B4C) exhibits a rhombohedral unit cell composed of icosahedra and linear chains.
- Phase transitions in boron carbide are second-order, driven by site exchange or vacancies.
- X-ray scattering is limited in probing structural changes due to similar scattering cross-sections of boron and carbon isotopes.
Purpose of the Study:
- To investigate phase transitions in boron carbide using phonon spectroscopy.
- To understand the impact of minimal structural modifications on boron carbide properties.
- To elucidate the role of carbon atom distribution in phase transitions.
Main Methods:
- Phonon spectroscopy to analyze vibrational properties.
- Analysis of changes in electronic structure, specific heat, and optical appearance.
- High-pressure experiments up to 33.2 GPa.
Main Results:
- Identified phase transition near B8C composition via electronic structure changes.
- Observed an endothermic phase transition at 712 K through specific heat anomalies.
- Characterized a high-pressure phase transition at 33.2 GPa, marked by a shift from opacity to transparency.
- Demonstrated that these transitions affect IR- and Raman-active phonons.
Conclusions:
- Phonon spectroscopy is crucial for studying boron carbide phase transitions where X-ray methods are limited.
- Phase transitions involve the transformation of distorted structures into others or highly ordered states.
- The distribution of polar carbon atoms within the icosahedra is a critical factor in boron carbide's phase behavior.
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