New Superhard Materials: Carbon and Silicon Nitrides

2008 ◽  
pp. 253-270
Author(s):  
J. E. Lowther
Keyword(s):  
Superhard Materials ◽  
Silicon Nitrides

scholarly journals Dislocation-mediated shear amorphization in boron carbide

2021 ◽  
Vol 7 (8) ◽  
pp. eabc6714 ◽  
Author(s):  
Kolan Madhav Reddy ◽  
Dezhou Guo ◽  
Shuangxi Song ◽  
Chun Cheng ◽  
Jiuhui Han ◽  
...  
Keyword(s):  
Boron Carbide ◽  
Structural Transition ◽  
Activation Volume ◽  
Structural Evolution ◽  
Dislocation Nucleation ◽  
Superhard Materials ◽  
Rate Dependent ◽  
Transmission Electron ◽  
Lower Activation ◽  
Underlying Mechanisms

The failure of superhard materials is often associated with stress-induced amorphization. However, the underlying mechanisms of the structural evolution remain largely unknown. Here, we report the experimental measurements of the onset of shear amorphization in single-crystal boron carbide by nanoindentation and transmission electron microscopy. We verified that rate-dependent loading discontinuity, i.e., pop-in, in nanoindentation load-displacement curves results from the formation of nanosized amorphous bands via shear amorphization. Stochastic analysis of the pop-in events reveals an exceptionally small activation volume, slow nucleation rate, and lower activation energy of the shear amorphization, suggesting that the high-pressure structural transition is activated and initiated by dislocation nucleation. This dislocation-mediated amorphization has important implications in understanding the failure mechanisms of superhard materials at stresses far below their theoretical strengths.

Structure and Properties of Novel Superhard Nanocrystalline/Amorphous Composite Materials

1995 ◽  
Vol 400 ◽  
Author(s):  
S. Vepřek ◽  
M. Haussmann ◽  
S. Reiprich
Keyword(s):  
Elastic Modulus ◽  
Composite Materials ◽  
Transition Metal ◽  
Theoretical Concept ◽  
Structure And Properties ◽  
Superhard Materials ◽  
Transition Metal Nitride ◽  
Upper Limit ◽  
Amorphous Si ◽  
Matrix Hardness

AbstractWe have developed a theoretical concept for the design of novel superhard materials and verified it experimentally on several systems nc-MenN/a-Si3N4 (nc-MenN is a nanocrystalline transition metal nitride imbedded in a thin amorphous Si3N4 matrix). Hardness in excess of 5000 kg/mm2 (about 50 GPa) and elastic modulus of ≥550 GPa have been achieved [1-3]. Here we address the questions of the universality of the concept for the design of a variety of nc/a systems and the upper limit of the hardness which may be achieved.

Intelligent laser machining system for multi-function processing of superhard materials

2021 ◽  
Author(s):  
Yong Wang ◽  
Wei Wang ◽  
Dongbin Zhang ◽  
Xiaolin Tian ◽  
Jiaojiao Qu ◽  
...  
Keyword(s):  
Laser Machining ◽  
Superhard Materials ◽  
Machining System

scholarly journals Photocurable acrylate-based composites with enhanced thermal conductivity containing boron and silicon nitrides

2018 ◽  
Vol 12 (9) ◽  
pp. 790-807 ◽  
Author(s):  
M. Sadej ◽  
H. Gojzewski ◽  
P. Gajewski ◽  
G. J. Vancso ◽  
E. Andrzejewska
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nitrides ◽  
Enhanced Thermal Conductivity
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