| 1. |
- Azina, Clio, et al.
(författare)
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Deposition of MAX phase-containing thin films from a (Ti,Zr)(2)AlC compound target
- 2021
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 551
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Tidskriftsartikel (refereegranskat)abstract
- This work reports on sputter depositions carried out from a compound (Ti,Zr)(2)AlC target on Al2O3(0 0 0 1) substrates at temperatures ranging between 500 and 900 degrees C. Short deposition times yielded 30-40 nm-thick Al-containing (Ti,Zr)C films, whereas longer depositions yielded thicker films up to 90 nm which contained (Ti,Zr)C and intermetallics. At 900 degrees C, the longer depositions led to films that also consisted of solid solution MAX phases. Detailed transmission electron microscopy showed that both (Ti,Zr)(2)AlC and (Ti,Zr)(3)AlC2 solid solution MAX phases were formed. Moreover, this work discusses the growth mechanism of the thicker films, which started with the formation of the mixed (Ti,Zr)C carbide, followed by the nucleation and growth of aluminides, eventually leading to solid state diffusion of Al within the carbide, at the highest temperature (900 degrees C) to form the MAX phases.
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| 2. |
- Charalampopoulou, Evangelia, et al.
(författare)
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Early stages of dissolution corrosion in 316L and DIN 1.4970 austenitic stainless steels with and without anticorrosion coatings in static liquid lead-bismuth eutectic (LBE) at 500 degrees C
- 2021
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Ingår i: Materials Characterization. - : ELSEVIER SCIENCE INC. - 1044-5803 .- 1873-4189. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- This work addresses the early stages (<= 1000 h) of the dissolution corrosion behavior of 316L and DIN 1.4970 austenitic stainless steels in contact with oxygen-poor (C-O < 10(-8) mass%), static liquid lead-bismuth eutectic (LBE) at 500 degrees C for 600-1000 h. The objective of this study was to determine the relative early-stage resistance of the uncoated steels to dissolution corrosion and to assess the protectiveness of select candidate coatings (Cr2AlC, Al2O3, V2AlxCy). The simultaneous exposure of steels with intended differences in microstructure and thermomechanical state showed the effects of steel grain size, density of annealing/deformation twins, and secondary precipitates on the steel dissolution corrosion behavior. The findings of this study provide recommendations on steel manufacturing with the aim of using the steels to construct Gen-IV lead-cooled fast reactors.
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| 3. |
- Chen, Liugang, et al.
(författare)
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Theoretical Prediction and Synthesis of (Cr2/3Zr1/3)(2)AIC i-MAX Phase
- 2018
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Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 57:11, s. 6237-6244
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Tidskriftsartikel (refereegranskat)abstract
- Guided by predictive theory, a new compound with chemical composition (Cr2/3Zr1/3)(2)AlC was synthesized by hot pressing of Cr, ZrH2, Al, and C mixtures at 1300 degrees C. The crystal structure is monoclinic of space group C2/c and displays in-plane chemical order in the metal layers, a so-called i-MAX phase. Quantitative chemical composition analyses confirmed that the primary phase had a (Cr2/3Zr1/3)(2)AlC stoichiometry, with secondary Cr2AlC, AlZrC2, and ZrC phases and a small amount of Al-Cr intermetallics. A theoretical evaluation of the (Cr2/3Zr1/3)(2)AlC magnetic structure was performed, indicating an antiferromagnetic ground state. Also (Cr2/3Zr1/3)(2)AlC, of the same structure, was predicted to be stable.
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| 4. |
- Goossens, Nick, et al.
(författare)
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Upscaled Synthesis Protocol for Phase-Pure, Colloidally Stable MXenes with Long Shelf Lives
- 2023
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Ingår i: Small Methods. - : WILEY-V C H VERLAG GMBH. - 2366-9608.
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Tidskriftsartikel (refereegranskat)abstract
- MXenes are electrically conductive 2D transition metal carbides/nitrides obtained by the etching of nanolaminated MAX phase compounds, followed by exfoliation to single- or few-layered nanosheets. The mainstream chemical etching processes have evolved from pure hydrofluoric acid (HF) etching into the innovative "minimally intensive layer delamination" (MILD) route. Despite their current popularity and remarkable application potential, the scalability of MILD-produced MXenes remains unproven, excluding MXenes from industrial applications. This work proposes a "next-generation MILD" (NGMILD) synthesis protocol for phase-pure, colloidally stable MXenes that withstand long periods of dry storage. NGMILD incorporates the synergistic effects of a secondary salt, a richer lithium (Li) environment, and iterative alcohol-based washing to achieve high-purity MXenes, while improving etching efficiency, intercalation, and shelf life. Moreover, NGMILD comprises a sulfuric acid (H2SO4) post-treatment for the selective removal of the Li3AlF6 impurity that commonly persists in MILD-produced MXenes. This work demonstrates the upscaled NGMILD synthesis of (50 g) phase-pure Ti(3)C(2)Tz MXene clays with high extraction yields (>22%) of supernatant dispersions. Finally, NGMILD-produced MXene clays dry-stored for six months under ambient conditions experience minimal degradation, while retaining excellent redispersibility. Overall, the NGMILD protocol is a leap forward toward the industrial production of MXenes and their subsequent market deployment.
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| 5. |
- Griseri, Matteo, et al.
(författare)
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Ta-based 413 and 211 MAX phase solid solutions with Hf and Nb
- 2020
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Ingår i: Journal of the European Ceramic Society. - : ELSEVIER SCI LTD. - 0955-2219 .- 1873-619X. ; 40:54, s. 1829-1838
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Tidskriftsartikel (refereegranskat)abstract
- New bulk MAX phase-based ceramics were synthesized in the Ta-Hf-Al-C and Ta-Nb-Al-C systems. Specifically, (Ta1-x,Hf-x)(4)AlC3 and (Ta1-x,Nb-x)(4)AlC3 stoichiometries with x = 0.05, 0.1, 0.15, 0.2, 0.25 were targeted by reactive hot pressing of Ta2H, HfH2, NbH0.89, Al and C powder mixtures at 1550 degrees C in vacuum. The produced ceramics were characterized in terms of phase composition and microstructure by X-ray diffraction, scanning electron microscopy, electron probe microanalysis and scanning transmission electron microscopy. The investigation confirmed the existence of such M-site solid solutions with low solute concentrations, as predicted by first-principles calculations. These calculations also predicted a linear trend in lattice parameter evolution with increasing Hf concentration, in agreement with the experimental results. In order to increase the low phase purity of the produced ceramics, Sn was added to form (Ta1-x,Hf-x)(4)(Al-0.5,Sn-0.5)C-3 and (Ta1-x,Nb-x)(4)(Al-0.5,Sn-0.5)C-3 double solid solutions, thus resulting in a higher content of the 413 MAX phase compounds in the produced ceramics.
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| 6. |
- Lapauw, Thomas, et al.
(författare)
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Synthesis of MAX Phases in the Hf-Al-C System
- 2016
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Ingår i: Inorganic Chemistry. - : AMER CHEMICAL SOC. - 0020-1669 .- 1520-510X. ; 55:21, s. 10922-10927
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, MAX phases in the Hf-Al-C system were experimentally synthesized using reactive hot pressing. HfC was observed as the main competing phase. The lattice parameters of Hf2AlC and Hf3AlC2 were determined by Rietveld refinement based on the X-ray diffraction data. The atomic stacking sequence was revealed by high-resolution scanning transmission electron microscopy. Mixtures of 211 and 312 stacking were observed within the same grain, including 523 layers. This transition in atomic structure is discussed.
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| 7. |
- Tunca, Bensu, et al.
(författare)
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Compatibility of Zr2AlC MAX phase-based ceramics with oxygen-poor, static liquid lead-bismuth eutectic
- 2020
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Ingår i: Corrosion Science. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0010-938X .- 1879-0496. ; 171
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates the compatibility of Zr2AlC MAX phase-based ceramics with liquid LBE, and proposes a mechanism to explain the observed local Zr2AlC/LBE interaction. The ceramics were exposed to oxygen-poor (C-O <= 2.2 x 10(-10) mass%), static liquid LBE at 500 degrees C for 1000 h. A new Zr-2(Al,Bi,Pb)C MAX phase solid solution formed in-situ in the LBE-affected Zr2AlC grains. Out-of-plane ordering was favorable in the new solid solution, whereby A-layers with high and low-Bi/Pb contents alternated in the crystal structure, in agreement with first-principles calculations. Bulk Zr-2(Al,Bi,Pb)C was synthesized by reactive hot pressing to study the crystal structure of the solid solution by neutron diffraction.
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