{"title":"Shock-induced phase transition and damage in nano-polycrystalline graphite affected by grain boundaries","authors":"","doi":"10.1016/j.commatsci.2024.113303","DOIUrl":null,"url":null,"abstract":"<div><p>Dynamic structural response of nano-polycrystalline graphite under shock compression is investigated using molecular dynamics (MD) simulations. Hugoniot data shows that the structural transition is activated at shock pressure <em>P</em>∼30 GPa (experimental range, 20–50 GPa), resulting in the formation and extension of hexagonal diamond nuclei along grain boundaries, embedded incoherently among thin-graphite grains. As <em>P</em> increases from 130 GPa, the structure starts to liquefy, accompanied by a decrease in shear stress <em>τ</em> from approximately 5.3 GPa, and completely liquefies at <em>P</em>∼250 GPa (melting pressure of graphite, 180–280 GPa) and <em>τ</em> ∼ 0 GPa. In ultrahigh-pressure region, a two-wave structure is generated consisting of an elastic shock wave and a phase transition wave, and when the piston velocity exceeds 5.2 km/s, the latter wave can catch up with the elastic one, eventually becoming a single over-driven wave. During the relaxation of compressed nano-polycrystalline graphite, void nucleation inside the sample induces the initiation of visible cracks when piston velocity is higher than 1 km/s. At low piston velocities, the cracks propagate gradually along grain boundaries due to shear-slip effects. While at high piston velocities, direct spall of the nano-polycrystalline graphite makes it into multiple fragments by ultrahigh strain rate tensile forces. This study provides a useful guide to the structural transition and dynamic damage evolution of nano-polycrystalline graphite under shock compression.</p></div>","PeriodicalId":10650,"journal":{"name":"Computational Materials Science","volume":null,"pages":null},"PeriodicalIF":3.1000,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Computational Materials Science","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S092702562400524X","RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Dynamic structural response of nano-polycrystalline graphite under shock compression is investigated using molecular dynamics (MD) simulations. Hugoniot data shows that the structural transition is activated at shock pressure P∼30 GPa (experimental range, 20–50 GPa), resulting in the formation and extension of hexagonal diamond nuclei along grain boundaries, embedded incoherently among thin-graphite grains. As P increases from 130 GPa, the structure starts to liquefy, accompanied by a decrease in shear stress τ from approximately 5.3 GPa, and completely liquefies at P∼250 GPa (melting pressure of graphite, 180–280 GPa) and τ ∼ 0 GPa. In ultrahigh-pressure region, a two-wave structure is generated consisting of an elastic shock wave and a phase transition wave, and when the piston velocity exceeds 5.2 km/s, the latter wave can catch up with the elastic one, eventually becoming a single over-driven wave. During the relaxation of compressed nano-polycrystalline graphite, void nucleation inside the sample induces the initiation of visible cracks when piston velocity is higher than 1 km/s. At low piston velocities, the cracks propagate gradually along grain boundaries due to shear-slip effects. While at high piston velocities, direct spall of the nano-polycrystalline graphite makes it into multiple fragments by ultrahigh strain rate tensile forces. This study provides a useful guide to the structural transition and dynamic damage evolution of nano-polycrystalline graphite under shock compression.
期刊介绍:
The goal of Computational Materials Science is to report on results that provide new or unique insights into, or significantly expand our understanding of, the properties of materials or phenomena associated with their design, synthesis, processing, characterization, and utilization. To be relevant to the journal, the results should be applied or applicable to specific material systems that are discussed within the submission.