| 1. |
- Eklund, Per, et al.
(författare)
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Epitaxial growth and electrical transport properties of Cr(2)GeC thin films
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 84:7, s. 075424-
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Tidskriftsartikel (refereegranskat)abstract
- Cr(2)GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr(2)GeC was grown directly onto Al(2)O(3)(0001) at temperatures of 700-800 degrees C. These films have an epitaxial component with the well-known epitaxial relationship Cr(2)GeC(0001)//Al(2)O(3)(0001) and Cr(2)GeC(11andlt;(2) overbarandgt;0)//Al(2)O(3)(1andlt;(1)over barandgt;00) or Cr(2)GeC(11andlt;(2) over barandgt;0)//Al(2)O(3)(andlt;(1) over barandgt;2andlt;(1) over barandgt;0). There is also a large secondary grain population with (10andlt;(1)overbarandgt;3) orientation. Deposition onto Al(2)O(3)(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr(2)GeC(0001) with a virtually negligible (10andlt;(1) over barandgt;3) contribution. In contrast to the films deposited at 700-800 degrees C, the ones grown at 500-600 degrees C are polycrystalline Cr(2)GeC with (10andlt;(1) over barandgt;0)-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53-66 mu Omega cm. Temperature-dependent resistivity measurements from 15-295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.
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| 2. |
- Gustavsson, Fredrik, et al.
(författare)
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A High-Resolution TEM/EELS Study of the Effect of Doping Elements on the Sliding Mechanisms of Sputtered WS2 Coatings
- 2013
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Konferensbidrag (refereegranskat)abstract
- It has been shown many times that cosputtering low-friction coatings of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) with other elements can improve the structural, mechanical, and tribological properties. To achieve the lowest friction, MoS2 or WS2 should be doped with element(s) improving the hardness and density of the coatings. On the other hand, such elements, or their compounds, should not be present in the outermost molecular layers at the sliding interface. This article suggests that there are important differences between how MoS2 and WS2 coatings respond to or react with doping elements, despite the almost identical structure and behavior of the undoped materials. Two systems have been investigated by high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) electron energy loss spectroscopy (EELS), W-S-C-Cr and W-S-C-Ti, and showed significant amounts of oxides, which typically formed a layer just underneath the crystalline WS2 top layer. Further, carbon was almost completely absent in the tribofilms, despite the fact that the as-deposited coatings contained as much as 40-50 at% C. An interesting observation here is that WS2 basal planes surround or embed Fe wear particles, suggesting a relatively strong adhesion or a Fe-S chemical bonding between iron/steel and WS2. The result of this is that the wear particles become pacified and remain in the contact as low-friction material.
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| 3. |
- Gustavsson, Fredrik, et al.
(författare)
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A High-Resolution TEM/EELS Study of the Effect of Doping Elements on the Sliding Mechanisms of Sputtered WS2 Coatings
- 2015
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Ingår i: Tribology Transactions. - : Informa UK Limited. - 1040-2004 .- 1547-397X. ; 58:1, s. 113-118
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Tidskriftsartikel (refereegranskat)abstract
- It has been shown many times that cosputtering low-friction coatings of molybdenum disulfide (MoS2) and tungsten disulfide (WS2) with other elements can improve the structural, mechanical, and tribological properties. To achieve the lowest friction, MoS2 or WS2 should be doped with element(s) improving the hardness and density of the coatings. On the other hand, such elements, or their compounds, should not be present in the outermost molecular layers at the sliding interface. This article suggests that there are important differences between how MoS2 and WS2 coatings respond to or react with doping elements, despite the almost identical structure and behavior of the undoped materials. Two systems have been investigated by high-resolution transmission electron microscopy (HRTEM) and scanning TEM (STEM) electron energy loss spectroscopy (EELS), W-S-C-Cr and W-S-C-Ti, and showed significant amounts of oxides, which typically formed a layer just underneath the crystalline WS2 top layer. Further, carbon was almost completely absent in the tribofilms, despite the fact that the as-deposited coatings contained as much as 40-50 at% C. An interesting observation here is that WS2 basal planes surround or embed Fe wear particles, suggesting a relatively strong adhesion or a Fe-S chemical bonding between iron/steel and WS2. The result of this is that the wear particles become pacified and remain in the contact as low-friction material.
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| 4. |
- Wang, Xiaoyue, et al.
(författare)
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Biomineralization at Titanium Revealed by Correlative 4D Tomographic and Spectroscopic Methods
- 2018
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Ingår i: Advanced Materials Interfaces. - : Wiley. - 2196-7350. ; 5:14
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Tidskriftsartikel (refereegranskat)abstract
- At an implant biointerface, where an engineered material merges into a biological environment, complex biophysicochemical interactions occur. One typical biointerface is the bond between human bone and dental or orthopedic implants, which is based on the biomineralization of essential bone components such as hydroxyapatite, at the implant surface. However, the exact bonding mechanism between bone and implants is still unclear. The distribution of both the mineralized and organic components of bone at the interface, and their origins, requires improved characterization. Here, the first correlative characterization is reported using multiple-length-scale tomography and spectroscopy techniques to probe the chemical structure of the biointerface between human bone and commercial titanium dental implant down to the atomic scale in four dimensions (4D). The existence of an intervening transition zone bonding mature bone tissue is demonstrated to implant at multiple length scales, where the phase of bone mineral differs immediately adjacent to the implant and atomic-scale osseointegration is confirmed. The correlative 4D electron energy loss spectroscopy tomography and atom probe tomography workflow established herein is transferable to other applications in materials or biological sciences.
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