MST-8 People
| Name |
Tongde Shen |
| Team |
Alloy Theory |
| Position |
Technical Staff Member |
| Phone |
(505) 665-1171 |
| E-Mail |
tdshen@lanl.gov |
| Research Interests |
Bulk metallic glasses, nanocrystalline materials, magnetic semiconductors, radiation effects |
| Research Highlights |
- MST-8 Scientists Develop Breakthrough in Processing Ultrastrong Bulk Nanomaterials
There has been growing interest in bulk nanomaterials-materials with crystallite size 100 nm or less-for structural applications because of their high strength and hardness, predictions of ductility and toughness in normally brittle materials, and even superplasticity at relatively low temperatures. Lack of reliable and inexpensive methods of processing and an absence of fundamental insight into the deformation processes, however, have been obstacles to their widespread application. Researchers led by Tongde Shen of MST-8 have used a flux-melting and melt-solidification technique to prepare bulk nanostructured Ag60Cu40 alloy. Technologically, the flux-melting and melt-solidification method represents a breakthrough in processing ultrastrong bulk nanomaterials for structural applications. To achieve nanosized crystallites in solidified melts usually requires a fast cooling rate of above a million Ks, resulting in only powders or thin foils. The flux technique can achieve nano!
Sized crystallites at a slow cooling rate of 100 Ks, leading to the formation of bulk nanomaterials. The flux-melting purifies the melts, leading to a large undercooling and nanometer-sized microstructure. These lead to the formation of artifact-free bulk nanomaterials, which provide perhaps the first good physical system to study the inherent mechanical properties of nanomaterials. The research by Shen and Ricardo Schwarz, MST-8, and X. Zhang at Texas AM University has been published in Applied Physics Letters 87, 141906 (2005).
- MST-8 collaboration results in radiation tolerant nanocrystalline materials MST-8's Tongde Shen, in collaboration with Kurt Sickafus, also MST-8, has made nanocrystalline MgGa2O4 powder by a mechanical alloying technique. The resulting nanophase has a grain size of approximately 10 nm with a narrow size distribution. Its radiation resistance is significantly enhanced compared to polycrystalline MgGa2O4. TEM observations of phase, structure, and defects are aimed at elucidating the influence of grain boundary on radiation damage effects.
A simple model has been developed to explain the enhanced radiation tolerance. By assuming that the accumulation of point defects induces the crystalline-to-amorphous phase transformation in the MgGa2O4 compound and that grain boundaries provide sinks for vacancies and interstitials (thereby allowing for defect recovery and annihilation), the model predicts that radiation tolerance in nanograined material may be enhanced by ~ six orders of magnitude compared to that of the corresponding polycrystalline phase. The model is now being tested on a LaAlO3 compound, which has a very low critical amorphization dose of ~ 0.03 dpa, allowing structural changes to be monitored over a wide range (four to five orders of magnitude) of radiation dose. The processing technique used to produce the material can be applied to most metals, ceramics or mixtures, offering opportunities to produce protective coatings for nuclear power applications.
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| Education |
- Ph.D.(Major Mater. Sci. Eng.), North Carolina State University, Raleigh, NC. 1993-1995
- Ph.D.(Major Mater. Sci. Eng.), Inst. Met. Res. Academia Sinica, Shenyang, China 1991-1993
- M. S.(Major Mater. Sci. Eng.), Inst. Met. Res. Academia Sinica, Shenyang, China 1988-1991
- B. S.(Major Mater. Sci. Eng.), Zhejiang Univ., Hangzhou, China 1982-1986
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| Curriculum Vitæ |
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Structure/Property Relations, MST-8 
