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Metallic hydrogen is a phase of hydrogen in which it behaves like an electrical conductor. This phase was predicted in 1935 on theoretical grounds by Eugene Wigner and Hillard Bell Huntington.
A diamond anvil cell (DAC) is a high-pressure device used in geology,engineering,and materials science experiments. It enables the compression of a small (sub-millimeter-sized) piece of material to extreme pressures,typically up to around 100–200 gigapascals,although it is possible to achieve pressures up to 770 gigapascals.
A superhard material is a material with a hardness value exceeding 40 gigapascals (GPa) when measured by the Vickers hardness test. They are virtually incompressible solids with high electron density and high bond covalency. As a result of their unique properties,these materials are of great interest in many industrial areas including,but not limited to,abrasives,polishing and cutting tools,disc brakes,and wear-resistant and protective coatings.
Diamond is the allotrope of carbon in which the carbon atoms are arranged in the specific type of cubic lattice called diamond cubic. It is a crystal that is transparent to opaque and which is generally isotropic. Diamond is the hardest naturally occurring material known. Yet,due to important structural brittleness,bulk diamond's toughness is only fair to good. The precise tensile strength of bulk diamond is little known;however,compressive strength up to 60 GPa has been observed,and it could be as high as 90–100 GPa in the form of micro/nanometer-sized wires or needles,with a corresponding maximum tensile elastic strain in excess of 9%. The anisotropy of diamond hardness is carefully considered during diamond cutting. Diamond has a high refractive index (2.417) and moderate dispersion (0.044) properties that give cut diamonds their brilliance. Scientists classify diamonds into four main types according to the nature of crystallographic defects present. Trace impurities substitutionally replacing carbon atoms in a diamond's crystal structure,and in some cases structural defects,are responsible for the wide range of colors seen in diamond. Most diamonds are electrical insulators and extremely efficient thermal conductors. Unlike many other minerals,the specific gravity of diamond crystals (3.52) has rather small variation from diamond to diamond.
In materials science,shear modulus or modulus of rigidity,denoted by G,or sometimes S or μ,is a measure of the elastic shear stiffness of a material and is defined as the ratio of shear stress to the shear strain:
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Pseudoelasticity,sometimes called superelasticity,is an elastic (reversible) response to an applied stress,caused by a phase transformation between the austenitic and martensitic phases of a crystal. It is exhibited in shape-memory alloys.
Natalia Dubrovinskaia is a Swedish geologist of Russian origin.
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The mechanical properties of carbon nanotubes reveal them as one of the strongest materials in nature. Carbon nanotubes (CNTs) are long hollow cylinders of graphene. Although graphene sheets have 2D symmetry,carbon nanotubes by geometry have different properties in axial and radial directions. It has been shown that CNTs are very strong in the axial direction. Young's modulus on the order of 270 - 950 GPa and tensile strength of 11 - 63 GPa were obtained.
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In continuum mechanics,ratcheting,or ratchetting,also known as cyclic creep,is a behavior in which plastic deformation accumulates due to cyclic mechanical or thermal stress.
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References
- 1 2 3 "Valery Levitas – Distinguished Professor [AER E] – External, Faculty – Profile". Expert Finder.
- 1 2 "Iowa State University (via Public) / Iowa State materials researcher elected to European Academy of Sciences and Arts". www.publicnow.com.
- ↑ "Valery Levitas". scholar.google.com.
- ↑ "Large Deformation of Materials with Complex Rheological Properties at Normal and High Pressure".
- 1 2 "Khan Plasticity Award – Recipients". sites.google.com.
- 1 2 Levitas, Valery I. (May 1, 2021). "Phase transformations, fracture, and other structural changes in inelastic materials". International Journal of Plasticity. 140: 102914. doi:10.1016/j.ijplas.2020.102914 – via ScienceDirect.
- 1 2 Levitas, Valery I. (March 14, 2019). "High-Pressure Phase Transformations under Severe Plastic Deformation by Torsion in Rotational Anvils". Materials Transactions. 60 (7): 1294–1301. doi:10.2320/matertrans.MF201923 – via J-Stage.
- ↑ "High-pressure mechanochemistry: Conceptual multiscale theory and interpretation of experiments" (PDF).
- ↑ Zarkevich, Nikolai A.; Chen, Hao; Levitas, Valery I.; Johnson, Duane D. (October 17, 2018). "Lattice Instability during Solid-Solid Structural Transformations under a General Applied Stress Tensor: Example of $\mathrm{Si}\text{ }\text{ }\mathrm{I}\ensuremath{\rightarrow}\mathrm{Si}\text{ }\text{ }\mathrm{II}$ with Metallization". Physical Review Letters. 121 (16): 165701. doi:10.1103/PhysRevLett.121.165701 – via APS.
- 1 2 Chen, Hao; Levitas, Valery I.; Xiong, Liming (October 1, 2019). "Amorphization induced by 60° shuffle dislocation pileup against different grain boundaries in silicon bicrystal under shear". Acta Materialia. 179: 287–295. Bibcode:2019AcMat.179..287C. doi:10.1016/j.actamat.2019.08.023 – via NASA ADS.
- 1 2 3 Levitas, Valery I.; Javanbakht, Mahdi (December 9, 2013). "Phase transformations in nanograin materials under high pressure and plastic shear: nanoscale mechanisms". Nanoscale. 6 (1): 162–166. Bibcode:2013Nanos...6..162L. doi:10.1039/C3NR05044K. PMID 24213214 – via pubs.rsc.org.
- 1 2 Levitas, Valery I.; Esfahani, S. Ehsan; Ghamarian, Iman (November 15, 2018). "Scale-Free Modeling of Coupled Evolution of Discrete Dislocation Bands and Multivariant Martensitic Microstructure". Physical Review Letters. 121 (20): 205701. Bibcode:2018PhRvL.121t5701L. doi:10.1103/PhysRevLett.121.205701. PMID 30500235 – via APS.
- ↑ Levitas, Valery I.; Zarechnyy, Oleg M. (November 23, 2010). "Modeling and simulation of strain-induced phase transformations under compression and torsion in a rotational diamond anvil cell". Physical Review B. 82 (17): 174124. Bibcode:2010PhRvB..82q4124L. doi:10.1103/PhysRevB.82.174124 – via APS.
- ↑ Levitas, Valery I.; Kamrani, Mehdi; Feng, Biao (October 1, 2019). "Tensorial stress-strain fields and large elastoplasticity as well as friction in diamond anvil cell up to 400 GPa". npj Computational Mathematics. 5: 94. Bibcode:2019npjCM...5...94L. doi:10.1038/s41524-019-0234-8 – via NASA ADS.
- ↑ Levitas, Valery I.; Dhar, Achyut; Pandey, K. K. (September 23, 2023). "Tensorial stress-plastic strain fields in α - ω Zr mixture, transformation kinetics, and friction in diamond-anvil cell". Nature Communications. 14 (1): 5955. arXiv: 2212.13000 . Bibcode:2023NatCo..14.5955L. doi:10.1038/s41467-023-41680-1. PMC 10517986 . PMID 37741842.
- ↑ Levitas, Valery I.; Shvedov, Leonid K. (February 28, 2002). "Low-pressure phase transformation from rhombohedral to cubic BN: Experiment and theory". Physical Review B. 65 (10): 104109. Bibcode:2002PhRvB..65j4109L. doi:10.1103/PhysRevB.65.104109 – via APS.
- ↑ Gao, Yang; Ma, Yanzhang; An, Qi; Levitas, Valery; Zhang, Yanyan; Feng, Biao; Chaudhuri, Jharna; Goddard III, William A. (May 29, 2018). "Shear driven formation of nano-diamonds at sub-gigapascals and 300 K". Carbon. 146: 364. arXiv: 1805.11239 . Bibcode:2019Carbo.146..364G. doi:10.1016/j.carbon.2019.02.012 – via arXiv.org.
- ↑ Levitas, Valery I.; Ma, Yanzhang; Selvi, Emre; Wu, Jianzhe; Patten, John A. (February 29, 2012). "High-density amorphous phase of silicon carbide obtained under large plastic shear and high pressure". Physical Review B. 85 (5): 054114. Bibcode:2012PhRvB..85e4114L. doi:10.1103/PhysRevB.85.054114 – via APS.
- ↑ Levitas, Valery I. (October 22, 2022). "Resolving puzzles of the phase-transformation-based mechanism of the strong deep-focus earthquake". Nature Communications. 13 (1): 6291. arXiv: 2110.10862 . Bibcode:2022NatCo..13.6291L. doi:10.1038/s41467-022-33802-y. PMC 9588062 . PMID 36273002.
- ↑ Feng, Biao; Levitas, Valery I. (April 21, 2017). "Pressure Self-focusing Effect and Novel Methods for Increasing the Maximum Pressure in Traditional and Rotational Diamond Anvil Cells". Scientific Reports. 7 (1): 45461. Bibcode:2017NatSR...745461F. doi:10.1038/srep45461 – via www.nature.com.
- ↑ Levitas, Valery I.; Henson, Bryan F.; Smilowitz, Laura B.; Asay, Blaine W. (June 11, 2004). "Solid-solid phase transformation via virtual melting significantly below the melting temperature". Physical Review Letters. 92 (23): 235702. Bibcode:2004PhRvL..92w5702L. doi:10.1103/PhysRevLett.92.235702. PMID 15245170 – via PubMed.
- ↑ Levitas, Valery I. (November 28, 2013). "Mechanochemical mechanism for reaction of aluminium nano- and micrometre-scale particles". Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences. 371 (2003): 20120215. Bibcode:2013RSPTA.37120215L. doi:10.1098/rsta.2012.0215. PMID 24146008 – via PubMed.
- ↑ Novikov, N. B.; Shvedov, L. K.; Krivosheya, Yu. N.; Levitas, V. I. (January 1, 2015). "New automated shear cell with diamond anvils for in situ studies of materials using X-ray diffraction". Journal of Superhard Materials. 37 (1): 1–7. doi:10.3103/S1063457615010013 – via Springer Link.
- ↑ "Richard-von-Mises Prize – GAMM e.V." www.gamm.org.
- ↑ "ASME Fellows List" (PDF).
- ↑ "International Journal of Plasticity | Structural Changes and Plasticity in Materials – In Honor of Professor Valery Levitas | ScienceDirect.com by Elsevier". www.sciencedirect.com.
- ↑ "Short bio of Professor Valery I. Levitas" (PDF).
- ↑ "Members | European Academy of Sciences and Arts". members.euro-acad.eu.
- ↑ "International Association of Advanced Materials – IAAM | Non-Profit Organization". IAAM. January 16, 2019.