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Superstrength through Nanotwinning.
Qi An1, William A Goddard1, Kelvin Y Xie2
1Materials and Process Simulation Center, California Institute of Technology , Pasadena, California 91125, United States.
Nano Letters
|December 15, 2016
Summary
Nanoscale twins in boron carbide (B4C) hard ceramic increase its strength beyond theoretical limits. This discovery challenges conventional material science understanding and offers new avenues for developing stronger materials.
Area of Science:
- Materials Science
- Nanotechnology
- Computational Materials Science
Background:
- Theoretical strength of materials is typically an upper bound for real crystals.
- Conventional understanding suggests defects limit material strength.
Purpose of the Study:
- To investigate if nanoscale twins can enhance the strength of boron carbide (B4C) beyond its theoretical limit.
- To explore the underlying strengthening mechanisms in nanotwinned B4C.
Main Methods:
- Quantum mechanics (QM) simulations were employed to model B4C.
- Nanoscale twins were computationally imposed on B4C structures.
- Experimental validation was performed on nanotwinned and twin-free B4C samples.
Main Results:
- QM simulations predicted an 11% increase in theoretical shear strength for nanotwinned B4C.
- Indentation strength of nanotwinned B4C was predicted to be 12% higher than perfect crystals.
- Experimental results confirmed nanotwinned B4C is 2.3% harder than twin-free B4C.
Conclusions:
- Nanoscale twinning can enhance the strength of hard ceramics like B4C beyond theoretical predictions.
- The strengthening mechanism involves the suppression of twin boundary slip due to directional covalent bonding.
- This finding opens possibilities for designing superior materials through controlled nanostructuring.