The electronic and mechanical properties of the XYB14 complex borides studied by first-principles methods

dc.contributor.advisor Scott P. Beckman
dc.contributor.author Wan, Liwen
dc.contributor.department Materials Science and Engineering
dc.date 2018-08-11T12:41:56.000
dc.date.accessioned 2020-06-30T02:47:48Z
dc.date.available 2020-06-30T02:47:48Z
dc.date.copyright Tue Jan 01 00:00:00 UTC 2013
dc.date.embargo 2015-07-30
dc.date.issued 2013-01-01
dc.description.abstract <p>Intensive scientific efforts have been invested in searching and designing new superhard materials for applications as abrasives, polishing and cutting tools, wear-resistant and protective coatings. The best-known superhard material to date is diamond. However, its industrial applications are greatly limited by its high cost and susceptibility to chemical corrosion. Alternatively, boron compounds are promising candidates because of boron's hardness and excellent chemical and thermal stability.</p> <p>Conventional superhard materials, such as diamond and cubic boron nitride, are usually comprised of a strong, covalently bonded network of atoms. This bonding usually results in a dense, highly symmetric crystal structure that is stoichiometric. Therefore, it is particularly challenging to chemically modify the structure and their mechanical properties are thus, "as made", rather than, "by design".</p> <p>Recently, a class of complex borides, based upon the AlMgB14 crystal structure, has been proposed as a potentially superhard material. Unlike conventional superhard materials, the crystal structure of AlMgB14 is only loosely packed. It is also known that a variety of metal species and vacancies can occupy the metal atom sites. The measured Vickers hardness of the base compound exceeds 32 GPa, and it is experimentally observed that the addition of impurity species and second phases has a significant beneficial impact on the mechanical properties. At this time, there has been no systematic study aimed to explain the origin of the intrinsic hardness of the XYB14-type compound or to understand how to control its physical properties.</p> <p>The goal of this project is to provide a thorough understanding of the electronic structure of the XYB14-type metal borides, and in particular how the electronic structure is related to its chemical composition. Based on first-principles methods, a series of calculations are performed to examine the relationship between the chemical bonding and the mechanical properties of XYB14. The impact of substituting different atomic species into both metal and boron sites is examined. The success of this project will provide insight to the origin of its unexpected hardness and predict practical methods to control the mechanical properties of XYB14 crystals.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/13166/
dc.identifier.articleid 4173
dc.identifier.contextkey 4250815
dc.identifier.doi https://doi.org/10.31274/etd-180810-3257
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/13166
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/27355
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/13166/Wan_iastate_0097E_13498.pdf|||Fri Jan 14 19:46:01 UTC 2022
dc.subject.disciplines Mechanics of Materials
dc.subject.keywords Borides
dc.subject.keywords Defects
dc.subject.keywords Density functional theory
dc.subject.keywords Mechanical properties
dc.title The electronic and mechanical properties of the XYB14 complex borides studied by first-principles methods
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication bf9f7e3e-25bd-44d3-b49c-ed98372dee5e
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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