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Phase Formation of Nanolaminated Transition Metal Carbide Thin Films [Elektronisk resurs] / Chung-Chuan Lai

Lai, Chung-Chuan, 1988- (författare)
Rosén, Johanna (preses)
Eklund, Per (preses)
Hultman, Lars (preses)
Radovic, Miladin (opponent)
Linköpings universitet Institutionen för fysik, kemi och biologi (utgivare)
Alternativt namn: Linköpings universitet. Institutionen för fysik och mätteknik (tidigare namn)
Alternativt namn: Linköpings universitet. Institutionen för fysik och mätteknik, biologi och kemi (tidigare namn)
Alternativt namn: IFM
Alternativt namn: Engelska : Department of Physics and Measurement Technology, Biology and Chemistry
Alternativt namn: Engelska : Department of Physics, Chemistry and Biology
Linköpings universitet Tekniska fakulteten (utgivare)
Linköping Department of Physics, Chemistry, and Biology (IFM), Linköping University, 2017
Engelska xvi, 63 s. (PDF)
Serie: Linköping Studies in Science and Technology. Dissertation, 0345-7524 ; 1850
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  • E-bokAvhandling(Diss. (sammanfattning) Linköping : Linköpings universitet, 2017)
Sammanfattning Ämnesord
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  • Research on inherently nanolaminated transition metal carbides is inspired by their unique properties combining metals and ceramics, such as higher damage tolerance, better machinability and lower brittleness compared to the binary counterparts, yet retaining the metallic conductivity. The interesting properties are related to their laminated structure, composed of transition-metalcarbide layers interleaved by non-transition-metal (carbide) layers. These materials in thin-film form are particularly interesting for potential applications such as protective coatings and electrical contacts. The goal of this work is to explore nanolaminated transition metal carbides from the aspects of phase formation and crystal growth during thin-film synthesis. This was realized by studying phases in select material systems synthesized from two major approaches, namely, fromdirect-deposition and post-deposition treatment. The first approach was used in studies on the Mo-Ga-C and Zr-Al-C systems. In the former system, intriguing properties have been predicted for the 3D phases and their 2D derivatives (socalled MXenes), while in the latter system, the phases are interesting for nuclear applications. In this work, the discovery of a new Mo-based nanolaminated ternary carbide, Mo 2 Ga 2 C, is evidenced from thin-film and bulk processes. Its structure was determined using theoretical and experimental techniques, showing that Mo 2 Ga 2 C has Ga double-layers in simple hexagonal stacking between adjacent Mo 2 C layers, and therefore is structurally very similar to Mo 2 GaC, except for the additional Ga layers. For the Zr-Al-C system, the optimization of phase composition and structure of Zr 2 Al 3 C 4 in a thin-film deposition process was studied by evaluating the effect of deposition parameters. I concluded that the formation of Zr 2 Al 3 C 4 is favored with a plasma flux overstoichiometric in Al, and with a minimum lattice-mismatch to the substrates. Consequently, epitaxial Zr 2 Al 3 C 4 thin film of high quality were deposited on 4H-SiC(001) substrates at 800 °C. With the approach of post-deposition treatment, the studies were focused on a new method of thermally-induced selective substitution reaction of Au for the non-transition-metal layers in nanolaminated carbides. Here, the reaction mechanism has been explored in Al-containing (Ti 2 AlC and Ti3AlC2) and Ga-containing (Mo2GaC and Mo 2 Ga 2 C) phases. The Al and Ga in these phases were selectively replaced by Au while the carbide layers remained intact, resulting in the formation of new layered phases, Ti 2 Au 2 C, Ti 3 Au 2 C 2 , Mo 2 AuC, and Mo 2 (Au 1 - x Ga x ) 2 C, respectively. The substitution reaction was explained by fast outward diffusion of the Al or Ga being attracted to the surface Au, in combination with back-filling of Au, which is chemically inert to the carbide layers,to the vacancies. The substitution reaction was further applied to Ga-containing nanolaminated carbides, (Cr 0.5 Mn 0.5 ) 2 GaC and Mo 2 GaC, motivated by development of novel magnetic nanolaminates. The former experiment resulted in the formation of (Cr 0.5 Mn 0.5 ) 2 AuC, where the retained (Cr 0.5 Mn 0.5 ) 2 C layers allowed a comparative study on the magnetic properties under the exchange of Ga for Au. After Au substitution, reduction in the Curie temperature and the saturation magnetization were observed, showing a weakened magnetic exchange interaction of the magnetic (Cr 0.5 Mn 0.5 ) 2  Clayers across the Au. In the Mo 2 GaC case, an Fe-containing MAX phase, Mo 2 AC with 50 at.% of Fe on the A site, was synthesized through selective substitution of Au-Fe alloy for the Ga layers, showing the first direct evidence for Fe in the MAX-phase structure. The substitution of Fe did not take place on another Mo 2 GaC sample tested for Fe exchange only, indicating the essential role of Au in catalyzing the Fe-substitution reaction. The knowledge gained from this thesis work contributes to improved approaches for attaining thin films of nanolaminated transition metal carbides with desired phase composition and crystal quality. The reports on the new nanolaminated phases through exchange interactions are likely to expand the family of nanolaminated carbides and advance their properties, and trigger more studies on related (quasi-) 2D materials. 

Ämnesord

Natural Sciences  (hsv)
Chemical Sciences  (hsv)
Inorganic Chemistry  (hsv)
Naturvetenskap  (hsv)
Kemi  (hsv)
Oorganisk kemi  (hsv)
Natural Sciences  (hsv)
Chemical Sciences  (hsv)
Materials Chemistry  (hsv)
Naturvetenskap  (hsv)
Kemi  (hsv)
Materialkemi  (hsv)
Natural Sciences  (hsv)
Physical Sciences  (hsv)
Condensed Matter Physics  (hsv)
Naturvetenskap  (hsv)
Fysik  (hsv)
Den kondenserade materiens fysik  (hsv)
Natural Sciences  (hsv)
Chemical Sciences  (hsv)
Physical Chemistry  (hsv)
Naturvetenskap  (hsv)
Kemi  (hsv)
Fysikalisk kemi  (hsv)
Övergångsmetaller  (sao)
Oorganisk kemi  (sao)
Tunna skikt (ytfysik)  (sao)
Tunnfilmsteknik  (sao)
Nanoteknik  (sao)
Materialteknik  (sao)
Thin films  (LCSH)
Transition metals  (LCSH)
Chemistry, Inorganic  (LCSH)
Nanotechnology  (LCSH)

Klassifikation

546.6 (DDC)
Ucea (kssb/8 (machine generated))
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