| 1. |
- Joelsson, Torbjörn, 1972-, et al.
(författare)
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Phase stability tuning in the NbxZr1-xN thin-film system for large stacking fault density and enhanced mechanical strength
- 2005
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86:13
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Tidskriftsartikel (refereegranskat)abstract
- The phase stability of hexagonal WC-structure and cubic NaCl-structure 4d transition metal nitrides was calculated using first-principles density functional theory. It is predicted that there is a multiphase or polytypic region for the 4d transition metal nitrides with a valence electron concentration around 9.5 to 9.7 per formula unit. For verification, epitaxial NbxZr1-xN (0 <= x <= 1) was grown by reactive magnetron sputter deposition on MgO(001) substrates and analyzed with transmission electron microscopy (TEM) and x-ray diffraction. The defects observed in the films were threading dislocations due to nucleation and growth on the lattice-mismatched substrate and planar defects (stacking faults) parallel to the substrate surface. The highest defect density was found at the x=0.5 composition. The nanoindentation hardness of the films varied between 21 GPa for the binary nitrides, and 26 GPa for Nb0.5Zr0.5N. Unlike the cubic binary nitrides, no slip on the preferred [1 (1) over bar0]{110} slip system was observed. The increase in hardness is attributed to the increase in defect density at x=0.5, as the defects act as obstacles for dislocation glide during deformation. The findings present routes for the design of wear-resistant nitride coatings by phase stability tuning.
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| 2. |
- Lu, J, et al.
(författare)
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Chemical vapour deposition of molybdenum carbides: aspects of phase stability
- 2000
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 370:1-2, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of different molybdenum carbides (δ-MoC1−x, γ′-MoC1−x and Mo2C) have been deposited from a gas mixture of MoCl5/H2/C2H4 at 800°C by CVD. The H2 content in the vapour has a strong influence on the phase composition and microstructure. Typically, high H2 contents lead to the formation of nanocrystalline δ-MoC1−x films while coarse-grained γ′-MoC1−x is formed with an H2-free gas mixture. This phase has previously only been synthesized by carburization of Mo in a CO atmosphere and it has therefore been considered as an oxycarbide phase stabilized by the presence of oxygen in the lattice. Our results, however, show that γ′-MoC1−x films containing only trace amounts of oxygen can be deposited by CVD. Stability calculations using a FP-LMTO method confirmed that the γ′-MoC1−x phase is stabilized by oxygen but that the difference in energy between e.g. δ-MoC0.75 and oxygen-free γ′-MoC0.75 is small enough to allow the synthesis of the latter phase in the absence of kinetic constraints. Annealing experiments of metastable δ-MoC1−x and γ′-MoC1−x films showed two different reaction products suggesting that kinetic effects play an important role in the decomposition of these phases.
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| 3. |
- Mendoza-Garcia, Patricia, 1988-, et al.
(författare)
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The Zic family homologue Odd-paired regulates Alk expression in Drosophila.
- 2017
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Ingår i: PLoS genetics. - : Public Library of Science (PLoS). - 1553-7404 .- 1553-7390. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- The Anaplastic Lymphoma Kinase (Alk) receptor tyrosine kinase (RTK) plays a critical role in the specification of founder cells (FCs) in the Drosophila visceral mesoderm (VM) during embryogenesis. Reporter gene and CRISPR/Cas9 deletion analysis reveals enhancer regions in and upstream of the Alk locus that influence tissue-specific expression in the amnioserosa (AS), the VM and the epidermis. By performing high throughput yeast one-hybrid screens (Y1H) with a library of Drosophila transcription factors (TFs) we identify Odd-paired (Opa), the Drosophila homologue of the vertebrate Zic family of TFs, as a novel regulator of embryonic Alk expression. Further characterization identifies evolutionarily conserved Opa-binding cis-regulatory motifs in one of the Alk associated enhancer elements. Employing Alk reporter lines as well as CRISPR/Cas9-mediated removal of regulatory elements in the Alk locus, we show modulation of Alk expression by Opa in the embryonic AS, epidermis and VM. In addition, we identify enhancer elements that integrate input from additional TFs, such as Binou (Bin) and Bagpipe (Bap), to regulate VM expression of Alk in a combinatorial manner. Taken together, our data show that the Opa zinc finger TF is a novel regulator of embryonic Alk expression.
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| 4. |
- Lu, J, et al.
(författare)
-
Chemical vapour deposition of molybdenum carbides: aspects of phase stability
- 2000
-
Ingår i: THIN SOLID FILMS. - 0040-6090. ; 370:1-2, s. 203-212
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of different molybdenum carbides (delta-MoC1-x, gamma'-MoC1-x and Mo2C) have been deposited from a gas mixture of MoCl5/H-2/C2H4 at 800 degrees C by CVD. The H-2 content in the vapour has a strong influence on the phase composition and microstr
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