[-] Show simple item record

dc.contributor.advisorChing, Wai-Yimeng
dc.contributor.authorMo, Yuxiang, 1986-eng
dc.date.issued2014-09-30eng
dc.date.submitted2014 Falleng
dc.descriptionTitle from PDF of title pages, viewed on July 13, 2015eng
dc.descriptionDissertation advisor: Wai-Yim Chingeng
dc.descriptionVitaeng
dc.descriptionIncludes bibliographic references (pages 124-140)eng
dc.descriptionThesis (Ph.D.)--Department of Physics and Astronomy and Department of Chemistry. University of Missouri--Kansas City, 2015eng
dc.description.abstractThe term “MAX phase” refers to a very interesting and important class of layered ternary transition-metal carbides and nitrides with a novel combination of both metal- and ceramic-like properties that have made these materials highly regarded candidates for numerous technological and engineering applications. In the present dissertation work, the electronic structure and optical conductivities of 20 MAX phases Ti3AC2 (A = Al, Si, Ge), Ti2AC (A = Al, Ga, In, Si, Ge, Sn, P, As, S), Ti2AlN, M2AlC (M = V, Nb, Cr), and Tan+1AlCn (n = 1 to 4) are studied using the first-principles orthogonalized linear combination of atomic orbitals (OLCAO) method. It is confirmed that the N(Ef) (total density of states at the Fermi level Ef) increases as the number of valence electrons of the composing elements increases. The local feature of total density of states (TDOS) near Ef is used to predict structural stability. The calculated effective charge on each atom shows that the M (transition-metal) atoms always lose charge to the X (C or N) atoms, whereas the A-group atoms mostly gain charge but some lose charge. Bond order values are obtained and critically analyzed for all types of interatomic bonds in the 20 MAX phases. Also included in this work is the exploration [using (Cr2Hf)2Al3C3 as an example] of the possibility of incorporating more types of elements into a MAX phase while maintaining the crystallinity, instead of creating solid solution phases. The crystal structure and elastic properties of (Cr2Hf)2Al3C3 are studied using the Vienna ab initio Simulation Package. Unlike MAX phases with a hexagonal symmetry (P63/mmc, #194), (Cr2Hf)2Al3C3 crystallizes in the monoclinic space group of P21/m (#11). Its structure is found to be energetically much more favorable against the allotropic segregation and solid solution phases. Calculations using a stress versus strain approach and the VRH approximation for polycrystals also show that (Cr2Hf)2Al3C3 has outstanding elastic modulieng
dc.description.tableofcontentsIntroduction of max phases -- Scope and motivation of research -- Theory and methodology -- Results and discussion on the twenty max phases -- Results and discussion on the derivative (Cr2Hf)2Al3C3 -- Summary -- Appendix A. Full basis of titanium atomic orbitals -- Appendix B. The relaxed unit cell of (Cr2Hf)2Al3C3 -- Appendix C. The relaxed 1 x 1 x 3 supercell of (Cr2Hf)2Al3C3 -- Appendix D. The relaxed segregation model -- Appendix E. The relaxed 3 x 3 x1 supercell of (Cr2Hf)2Al3C3 -- Appendix F. The relaxed solid solution modeleng
dc.format.extentxii, 142 pageseng
dc.identifier.urihttps://hdl.handle.net/10355/43901eng
dc.subject.lcshNitrideseng
dc.subject.lcshElectronic structureeng
dc.subject.lcshMaterials scienceeng
dc.subject.lcshCarbideseng
dc.subject.otherDissertation -- University of Missouri--Kansas City -- Physicseng
dc.subject.otherDissertation -- University of Missouri--Kansas City -- Chemistryeng
dc.titleElectronic, Optical, Structural, and Elastic Properties of MAX Phases and (Cr2Hf)2Al3C3eng
dc.typeThesiseng
thesis.degree.disciplinePhysics (UMKC)eng
thesis.degree.disciplineChemistry (UMKC)
thesis.degree.grantorUniversity of Missouri--Kansas Cityeng
thesis.degree.levelDoctoraleng
thesis.degree.namePh.D.eng


Files in this item

[PDF]

This item appears in the following Collection(s)

[-] Show simple item record