Understanding formation of metals and alloys in solution with in situ characterizations

Ma, Xuetian

Title:

Understanding formation of metals and alloys in solution with in situ characterizations

dc.contributor.advisor	Chen, Hailong
dc.contributor.author	Ma, Xuetian
dc.contributor.committeeMember	Hesketh, Peter
dc.contributor.committeeMember	Kohl, Paul
dc.contributor.committeeMember	Xia, Shuman
dc.contributor.committeeMember	Zhu, Ting
dc.contributor.department	Mechanical Engineering
dc.date.accessioned	2019-05-29T14:01:09Z
dc.date.available	2019-05-29T14:01:09Z
dc.date.created	2019-05
dc.date.issued	2019-01-08
dc.date.submitted	May 2019
dc.date.updated	2019-05-29T14:01:09Z
dc.description.abstract	Phase diagrams are the maps for the design and synthesis of functional materials. However, the bulk phase diagrams oftentimes become not predictive in the synthesis of nanoparticles owing to the significant contribution of surface energy to the total energy. Synchrotron X-ray diffraction (XRD) is a powerful tool to monitor nucleation and crystal growth process of nanostructured materials with time-resolved observations. A series of in situ studies were conducted to understand the phase formation of metals in nanoscale. To achieve a systematical understanding on the polymorphism of nanomaterials, metallic Cobalt (Co) was chosen as a model system, where the two polymorphs, fcc and hcp phases, can be tuned with 100% selectivity. Through both in situ solvothermal and in situ electrodeposition, combining with first-principles Density Functional Theory (DFT), we found out that the bulk metastable phase becomes stable at nanometer scale, mainly resulting from the change of surface energy under various pH conditions. Furthermore, in situ electrodeposition studies show that high over-potential expedites the kinetics of the reaction and yields both the metastable phase and stable phase concurrently under certain pH regions. Based on these works, we first explored the nanometric phase formation of Cobalt (Co)-Nickel (Ni) system through in situ electrodeposition. It was found that the polymorphs formation of Co-Ni is determined by a number of key factors, including the composition (elementary ratio), the pH of electrolyte and the overpotential. These factors together impact the surface energy and the thermodynamics of the nanometric alloy particles, as well as the kinetics of reaction, and thus alternate phase boundaries in the phase diagram. Inspired by the new findings in above fundamental research, we also conducted research closely related to applications. We developed a facile one-step electrodeposition process for copper current collectors with 3-D architected porous nano-structures. The Li anode hosted in the 3-D Cu current collectors demonstrates excellent cycling performance with little dendrites formation for both liquid or solid-state full cells. This extremely simple and scalable process could be easily incorporated into the roll-to-roll manufacturing processes of battery industries.
dc.description.degree	Ph.D.
dc.format.mimetype	application/pdf
dc.identifier.uri	http://hdl.handle.net/1853/61198
dc.language.iso	en_US
dc.publisher	Georgia Institute of Technology
dc.subject	Nanoparticles
dc.subject	Cobalt
dc.subject	In situ solvothermal
dc.subject	In situ electrodeposition
dc.subject	Synchrotron x-ray diffraction
dc.subject	Lithium-metal batteries.
dc.title	Understanding formation of metals and alloys in solution with in situ characterizations
dc.type	Text
dc.type.genre	Dissertation
dspace.entity.type	Publication
local.contributor.advisor	Chen, Hailong
local.contributor.corporatename	George W. Woodruff School of Mechanical Engineering
local.contributor.corporatename	College of Engineering
relation.isAdvisorOfPublication	75e178e0-922b-4f56-afcf-286fb9f7d9c5
relation.isOrgUnitOfPublication	c01ff908-c25f-439b-bf10-a074ed886bb7
relation.isOrgUnitOfPublication	7c022d60-21d5-497c-b552-95e489a06569
thesis.degree.level	Doctoral