| 1. |
- Naguib, M., et al.
(författare)
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New Solid Solution MAX Phases: (Ti-0.5, V-0.5)(3)AlC2, (Nb-0.5, V0.5)(2)AlC, (Nb-0.5, V-0.5)(4)AlC3 and (Nb-0.8, Zr-0.2)(2)AlC
- 2014
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Ingår i: Materials Research Letters. - : TAYLOR & FRANCIS INC. - 2166-3831. ; 2:4, s. 233-240
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Tidskriftsartikel (refereegranskat)abstract
- We synthesized the following previously unreported aluminum-containing solid solution M(n+1)AX(n) phases: (Ti-0.5, V-0.5)(3)AlC2, (Nb-0.5, V-0.5)(2)AlC, (Nb-0.5, V-0.5)(4)AlC3 and (Nb-0.8, Zr-0.2)(2)AlC. Rietveld analysis of powder X-ray diffraction patterns was used to calculate the lattice parameters and phase fractions. Heating Ti, V, Al and C elemental powders-in the molar ratio of 1.5: 1.5: 1.3: 2-to 1, 450 degrees C for 2 h in flowing argon, resulted in a predominantly phase pure sample of (Ti-0.5, V-0.5)(3)AlC2. The other compositions were not as phase pure and further work on optimizing the processing parameters needs to be carried out if phase purity is desired.
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| 2. |
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| 3. |
- Champagne, A., et al.
(författare)
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First-order Raman scattering of rare-earth containing i-MAX single crystals (Mo2/3RE1/3)(2)AlC (RE = Nd, Gd, Dy, Ho, Er)
- 2019
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Ingår i: Physical Review Materials. - : AMER PHYSICAL SOC. - 2475-9953. ; 3:5
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report on the growth of single crystals of various (Mo2/3RE1/3)(2)AlC (RE = Nd, Gd, Dy, Ho, Er) i-MAX phases and their Raman characterization. Using first principles, the wave numbers of the various phonon modes and their relative atomic displacements are calculated and compared to experimental results. Twelve high-intensity Raman peaks are identified as the fingerprint of this new family of rare-earth containing i-MAX phases, thus being a useful tool to investigate their corresponding composition and structural properties. Indeed, while a redshift is observed in the low-wave-number range due to an increase of the rare-earth atomic mass when moving from left to right on the lanthanide row, a blueshift is observed for most of the high-wave-number modes due to a strengthening of the bonds. A complete classification of bond stiffnesses is achieved based on the direct dependence of a phonon mode wave number with respect to the bond stiffness. Finally, STEM images are used to confirm the crystal structure.
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| 4. |
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| 5. |
- Halim, Joseph, 1985-, et al.
(författare)
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Synthesis of Two-Dimensional Nb1.33C (MXene) with Randomly Distributed Vacancies by Etching of the Quaternary Solid Solution (Nb2/3Sc1/3)2AlC MAX Phase
- 2018
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 1:6, s. 2455-2460
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Tidskriftsartikel (refereegranskat)abstract
- Introducing point defects in two-dimensional (2D) materials can alter or enhance their properties. Here, we demonstrate how etching a laminated (Nb2/3Sc1/3)2AlC MAX phase (solid solution) of both the Sc and Al atoms results in a 2D Nb1.33C material (MXene) with a large number of vacancies and vacancy clusters. This method is applicable to any quaternary, or higher, MAX phase, wherein one of the transition metals is more reactive than the other and could be of vital importance in applications such as catalysis and energy storage. We also report, for the first time, on the existence of solid solution (Nb2/3Sc1/3)3AlC2 and (Nb2/3Sc1/3)4AlC3 phases.
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| 6. |
- Men, Arturo, et al.
(författare)
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Spectroscopic ellipsometry study on the dielectric function of bulk Ti2AlN,Ti2AlC, Nb2AlC, (Ti0.5,Nb0.5)2AlC, and Ti3GeC2 MAX-phases
- 2011
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Ingår i: Journal of Applied Physics. - USA : AIP Publishing. - 0021-8979 .- 1089-7550. ; 109, s. 013530-
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Tidskriftsartikel (refereegranskat)abstract
- The averaged complex dielectric function epsilon=() /3 of polycrystalline Ti2AlN, Ti2AlC,Nb2AlC, (Ti0.5,Nb0.5)2AlC, and Ti3GeC2 was determined by spectroscopic ellipsometry coveringthe mid infrared to the ultraviolet spectral range. The dielectric functions of epsilon correspond to the perpendicular and parallel dielectric tensor components relative to the crystallographic c-axis ofthese hexagonal compounds. The optical response is represented by a dispersion model with Drude–Lorentz and critical point contributions. In the low energy range the electrical resistivity is obtainedfrom the Drude term and ranges from 0.48 microOhm m for Ti3GeC2 to 1.59 mucro Ohm m for (Ti0.5,Nb0.5)2AlC.Furthermore, several compositional dependent interband electronic transitions can be identified. Forthe most important ones, Im(epsilon) shows maxima at: 0.78, 1.23, 2.04, 2.48, and 3.78 eV for Ti2AlN;0.38, 1.8, 2.6, and 3.64 eV for Ti2AlC; 0.3, 0.92, and 2.8 eV in Nb2AlC; 0.45, 0.98, and 2.58 eV in(Ti0.5,Nb0.5)2AlC; and 0.8, 1.85, 2.25, and 3.02 eV in Ti3GeC2.
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| 7. |
- Mockuté, Aurelija, et al.
(författare)
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Solid Solubility and Magnetism upon Mn Incorporation in the Bulk Ternary Carbides Cr2AlC and Cr2GaC
- 2015
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Ingår i: Materials Research Letters. - : Taylor & Francis. - 2166-3831. ; 3:1, s. 16-22
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report on the bulk synthesis of (Cr1-xMnx)(2)AlC and (Cr1-yMny)(2)GaC MAX phases. Scanning electron and transmission electron microscopy, in combination with energy-dispersive X-ray spectroscopy performed locally on MAX phase grains, revealed x and y to be 0.06 (3 at%) and 0.3 (15 at%), respectively. The introduction of Mn into the structure did not result in appreciable changes in the c-lattice constants. Vibrating sample magnetometry measurements suggest that bulk (Cr0.7Mn0.3)(2)GaC may be magnetic.
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| 8. |
- Plummer, G., et al.
(författare)
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On the origin of kinking in layered crystalline solids
- 2021
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Ingår i: Materials Today. - : Elsevier Science Ltd. - 1369-7021 .- 1873-4103. ; 43, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- Kinking is a deformation mechanism ubiquitous to layered systems, ranging from the nanometer scale in layered crystalline solids, to the kilometer scale in geological formations. Herein, we demonstrate its origins in the former through multiscale experiments and atomistic simulations. When compressively loaded parallel to their basal planes, layered crystalline solids first buckle elastically, then nucleate atomic-scale, highly stressed ripplocation boundaries - a process driven by redistributing strain from energetically expensive in-plane bonds to cheaper out-of-plane bonds. The consequences are far reaching as the unique mechanical properties of layered crystalline solids are highly dependent upon their ability to deform by kinking. Moreover, the compressive strength of numerous natural and engineered layered systems depends upon the ease of kinking or lack there of.
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| 9. |
- Spencer, C B, et al.
(författare)
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Phase Evaluation in Al(2)O(3) Fiber-Reinforced Ti(2)AlC During Sintering in the 1300 degrees C-1500 degrees C Temperature Range
- 2011
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Ingår i: Journal of The American Ceramic Society. - : Wiley-Blackwell. - 0002-7820 .- 1551-2916. ; 94:10, s. 3327-3334
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Tidskriftsartikel (refereegranskat)abstract
- In this article, the reactivity of Ti(2)AlC powders, with 3 and 10 mu m alumina, Al(2)O(3), fibers during pressure-assisted sintering is explored. Samples were fabricated by hot-isostatic-pressing (HIPed) or hot-pressing (HPed), and characterized by X-ray diffraction, differential thermal analysis, and electron microscopy-both scanning and transmission-equipped with energy dispersive X-ray spectroscopes. Samples prepared at 1300 degrees C were fully dense, with no apparent reaction between fiber and matrix. In samples HPed to 1500 degrees C, even pure Ti(2)AlC powders dissociated to Ti(3)AlC(2) according to: 2 Ti(2)AlC = Ti(3)AlC(2) + TiAl(x) (l) + (1-x) Al (l/v), with x andlt; 1. More severe Al loss results in the formation of TiC(y). The presence of the Al(2)O(3) fibers delayed densification enough to allow most of the Al and some of the Ti to escape into the vacuum of the hot press or react with the encapsulating glass during HIPing a resulting in a more intensive dissociation of the Ti(2)AlC. Although, in principle Ti(2)AlC can be reinforced with Al(2)O(3) fibers, the processing/use temperature will have to be kept below 1500 degrees C, as, at that temperature the fibers, used here, sinter together.
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| 10. |
- Altamimi, S., et al.
(författare)
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On Stiffness, Strength, Anisotropy, and Buckling of 30 Strut-Based Lattices with Cubic Crystal Structures
- 2022
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Ingår i: Advanced Engineering Materials. - : Wiley. - 1438-1656 .- 1527-2648. ; 24:7
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Tidskriftsartikel (refereegranskat)abstract
- Architected cellular structures are increasingly receiving attention in numerous applications due to advances in additive manufacturing and their promising multi-functional properties. Herein, 30 architected strut-based lattices of cubic crystal symmetry are developed and their stiffness and strength are investigated computationally and experimentally. Finite element simulations are conducted to compute the effective stiffness, yield strength, and buckling strength under uniaxial, shear, and hydrostatic loadings. Also, elastic anisotropy is assessed and bifurcation analysis is performed to estimate the threshold relative density for each lattice. Selected lattices of various relative densities are 3D printed from a polymeric material using selective laser sintering (SLS). The numerical results show that the modes of deformation whether stretching-dominated, bending-dominated, or mixed differ for the various loading conditions. It is observed that by combining different lattice structures in a hybrid approach, a decrease in the anisotropic behavior is obtained, and an overall enhancement of the mechanical properties is achieved. The numerical results show rather good agreement with the experimental findings. The current study can be crucial for using the investigated lattices for enhancing the multi-functional properties of structural systems.
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