A5053163067- High-Velocity Impact and Material Behavior
- Advanced ceramic materials synthesis
- Advanced materials and composites
- Boron and Carbon Nanomaterials Research
- Metal and Thin Film Mechanics
- Intermetallics and Advanced Alloy Properties
- High-pressure geophysics and materials
- Diamond and Carbon-based Materials Research
- Ion-surface interactions and analysis
- Microstructure and mechanical properties
- Aluminum Alloys Composites Properties
- Energetic Materials and Combustion
- Advanced Surface Polishing Techniques
- Advanced Materials Characterization Techniques
- Rock Mechanics and Modeling
- Electromagnetic Launch and Propulsion Technology
- Nuclear Materials and Properties
- Powder Metallurgy Techniques and Materials
- Additive Manufacturing and 3D Printing Technologies
- nanoparticles nucleation surface interactions
- Particle Dynamics in Fluid Flows
- Granular flow and fluidized beds
- Metallurgy and Material Forming
- MXene and MAX Phase Materials
- Advanced X-ray and CT Imaging
DEVCOM Army Research Laboratory
2016-2025
United States Army Combat Capabilities Development Command
2019-2024
CECOM Software Engineering Center
2010
American Ceramic Society
2005
University of California, San Diego
1992-1998
Korea Advanced Institute of Science and Technology
1996
University of California System
1995-1996
Significance When crystalline solids are stressed quasi-statically, dislocation slip, twinning, and phase transformations the predominant mechanisms to dissipate imparted elastic energy. Under shock, high hydrostatic shear stresses promptly build up at shock front, favoring fast energy dissipation mechanisms. Amorphization, which may only involve localized atomic arrangements, is therefore an additional potential candidate. Shock-induced amorphization has now been reported in various...
Two commercial hot‐pressed boron carbide ceramics were investigated by transmission electron microscopy. Atomic‐scale observations suggest that the grain boundaries of two materials are free grain‐boundary films. triple‐junction phases found and characterized to be rhombohedral Fe 2 B 103 orthorhombic Ti 3 4 . In addition, intra‐granular precipitates, AlN, Mo (C, B) graphite, identified have coherent relationships with matrix. Micron‐scale inclusions also observed most them determined...
Detailed microstructural characterization was carried out on a commercial‐grade hot‐pressed boron carbide armor plate. The grains have close to B 4 C stoichiometry, and most of them no planar defects. prominent second phase is intergranular graphite inclusions that are surrounded by multiple grains. Submicrometer intragranular BN AlN precipitates were also observed. In addition, fine dispersions nanoprecipitates observed in some but not all No films found. These characteristics compared with...
Si-doped boron carbide could be a promising material for the next-generation body armor.
The inelastic deformation mechanisms and damage features observed in structural ceramics subjected to nonpenetrating, high‐velocity impacts are similar those seen quasistatic Hertzian indentation, albeit more severe. For on large ceramic bodies (relative impactor diameter), cone cracking is the primary mechanism regions of high tensile stresses. In nonhydrostatic compressive stresses, depending material characteristics, elasticity, grain‐boundary microcracking, or plasticity mechanisms,...
It is demonstrated that controlled high-strain-rate plastic deformation of heterogeneous reactive porous materials (Nb+Si, Mo+Si+MoSi2) produces shear localization. Within the bands, having thicknesses 5–20 μm, overall strains (γ≤100) and strain rates (γ̇≤107 s−1) result in changes particle morphology, melting, regions partial reaction. The band thickness smaller than initial characteristic size mixture (≤44 μm). This ensures quenching deformed material structure same time scale as (10−5 s)....
The Ti + 2B exothermic chemical reaction was used in combination with a high‐velocity forging step to produce dense TiB 2 ‐(20 vol%)SiC composites. Densities excess of 96 % the theoretical were achieved for both SiC particulate and fiber additions. X‐ray diffractometry revealed products be SiC. microstructures are composed spheroidal phase, highly contiguous binder an apparent eutectic between located at regions preexisting These microstructural features suggest that underwent peritectic...
A novel process for the manufacture of dense titanium carbide is described. Titanium produced by reaction synthesis method, while densification and near‐net shaping accomplished a high‐velocity forging step. Disks with 10‐cm diameter were densities over 96% theoretical density. The major problem encountered in this study has been thermal shock. Use insulation furnace cooling decreased severity problem. Optical scanning electron microscopy observations resulting microstructure reveal equiaxed...
The role that grain boundaries (GBs) can play on mechanical properties has been studied extensively for metals and alloys. However, covalent solids such as boron carbide (B4C), the of GB inelastic response to applied stresses is not well established. We consider here unusual ceramic, which very hard lightweight but exhibits brittle impact behavior. used quantum mechanics (QM) simulations examine in atomistic structures model GBs B4C under pure shear also with biaxial deformation mimics...
In Tabor's classical studies of the deformation metals, yield stress ( Y ) and hardness H were shown to be related according / ≈ 3 for complete or fully plastic deformation. Since then it has been anecdotally ceramics that this ratio is <3. Interest exists explore further so Hertzian indentation was used measure apparent numerous metals their results compared with each material's load‐dependent Knoop hardness. The evaluated included standard reference materials (silicon nitride tungsten...