| 1. |
- Field, M. R., et al.
(författare)
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A combinatorial comparison of DC and high power impulse magnetron sputtered Cr2AlC
- 2014
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 259, s. 746-750
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Tidskriftsartikel (refereegranskat)abstract
- Using a combinatorial approach, Cr, Al and C have been deposited onto sapphire wafer substrates by High Power Impulse Magnetron Sputtering (HiPIMS) and DC magnetron sputtering. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and X-ray diffraction were employed to determine the composition and microstructure of the coatings and confirm the presence of the Cr2AlC MAX phase within both coatings. One location in both the DCMS and HiPIMS coatings contained only MAX phase Cr2AlC. The electrical resistivity was also found to be nearly identical at this location and close to that reported from the bulk, indicating that the additional energy in the HiPIMS plasma was not required to form high quality MAX phase Cr2AlC.
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| 2. |
- Persson, Per, et al.
(författare)
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Formation of the MAX-phase oxycarbide Ti2AlC1-xOx studied via electron energy-loss spectroscopy and first-principles calculations
- 2009
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Ingår i: PHYSICAL REVIEW B. - 1098-0121. ; 80:9, s. 092102-
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen incorporation in the Ti2AlC MAX phase and TiC was investigated in the electron microscope using spatially resolved fine-structure electron energy-loss spectroscopy analysis. Corresponding fine structures were calculated within the full-potential-linearized augmented plane-wave framework. In the calculations, oxygen was substituted for aluminum and carbon in Ti2AlC as well as for carbon in TiC, in concentrations of 3.1, 6.2, and 12.5 at %. Comparison of calculated and measured spectra shows that oxygen is incorporated on the carbon site in both TiC and Ti2AlC. These findings reveal the existence of MAX phase oxycarbide MA(O,C) alloys and O as a third X element in addition to C and N.
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| 3. |
- Persson, P.O.A., et al.
(författare)
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A solid phase reaction between Ti Cx thin films and Al2 O3 substrates
- 2008
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 103:6
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Tidskriftsartikel (refereegranskat)abstract
- Ti Cx thin films were deposited on Al2 O3 substrates at 900 °C by using a multiple cathode high current pulsed cathodic arc. The Ti:C pulse ratio and, hence, the composition was varied from C rich to Ti rich. It is found that the Al2 O3 substrate is decomposed and reacts with the Ti Cx film to incorporate significant amounts of O and Al in the growing film. When the stoichiometry is suitable, epitaxially oriented Ti2 AlC MAX phase with significant O incorporated is formed. The results indicate that Al2 O3 is not an ideal substrate material for the growth of transition metal carbides and MAX phase thin films. © 2008 American Institute of Physics.
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| 4. |
- Rosen, Johanna, et al.
(författare)
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Amorphous and crystalline phases in thermal quench simulations of alumina
- 2007
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Ingår i: Journal of Chemical Physics. - : American Institute of Physics. - 0021-9606 .- 1089-7690. ; 126:20, s. 204709-
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Tidskriftsartikel (refereegranskat)abstract
- The authors report molecular dynamics simulations of alumina (Al2O3) during crystallization from the melt. Using liquid quench methods, they investigate the effect of cooling rate on the structural evolution of the alpha, kappa, and the bixbyite phases. A critical temperature window is identified, where the time spent in this window is crucial in determining the extent to which the systems approach crystallinity. A strong dependence is observed between the final structure and the quench rate, which is most pronounced for the alpha phase and to lesser extent for the other phases. The results show that the different phases have different tendencies to crystallize that are determined by energetics, complexity of crystal structure, and the number of metastable states.
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| 5. |
- Rosen, Johanna, et al.
(författare)
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Deposition of epitaxial Ti2AlC thin films by pulsed cathodic arc
- 2007
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Ingår i: Journal of Applied Physics. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 101:5, s. 056101-
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Tidskriftsartikel (refereegranskat)abstract
- A multicathode high current pulsed cathodic arc has been used to deposit Ti2AlC thin films belonging to the group of nanolaminate ternary compounds of composition M(n+1)AX(n). The required stoichiometry was achieved by means of alternating plasma pulses from three independent cathodes. We present x-ray diffraction and transmission electron microscopy analysis showing that epitaxial single phase growth of Ti2AlC has been achieved at a substrate temperature of 900 degrees C. Our results demonstrate a powerful method for MAX phase synthesis, allowing for phase tuning within the M(n+1)AX(n) system.
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| 6. |
- Rosen, Johanna, et al.
(författare)
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Influence of gas entry point on plasma chemistry, ion energy and deposited alumina thin films in filtered cathodic arc
- 2007
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Ingår i: Plasma chemistry and plasma processing. - : Springer Science Business Media. - 0272-4324 .- 1572-8986. ; 27:5, s. 599-608
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Tidskriftsartikel (refereegranskat)abstract
- The effect of gas entry point on the plasma chemistry, ion energy distributions and resulting alumina thin film growth have been investigated for a d.c. cathodic arc with an aluminum cathode operated in an oxygen/argon atmosphere. Ions of aluminum, oxygen and argon, as well as ions originating from the residual gas are investigated, and measurements for gas entry at both the cathode and close to the substrate are compared. The latter was shown to result in higher ion flux, lower levels of ionised residual gas, and lower ion energies, as compared to gas inlet at the cathode. These plasma conditions that apply when gas entry at the substrate is used result in a higher film deposition rate, less residual gas incorporation, and more stoichiometric alumina films. The results show that the choice of gas entry point is a crucial parameter in thin film growth using reactive PVD processes such as reactive cathodic arc deposition.
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| 7. |
- Rosen, Johanna, et al.
(författare)
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Oxygen incorporation in Ti2AlC thin films
- 2008
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Ingår i: Applied Physics Letters. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 92:6, s. 064102-
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of Ti2AlC MAX phase have been deposited using a multiple cathode pulsed cathodic arc. Evidence for substantial oxygen incorporation in the MAX phase is presented, likely originating from residual gas present in the vacuum chamber during deposition. The characteristic MAX phase crystal structure is maintained, in agreement with ab initio calculations, supporting substitutional O in C lattice positions. On the basis of these results, we propose the existence of a MAX phase-like material with material properties tuned by the incorporation of oxygen. Additionally, possible unintentional O incorporation in previously reported MAX phase materials is suggested.
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| 8. |
- Rosén, Johanna, et al.
(författare)
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Oxygen incorporation in Ti2AlC: Tuning of anisotropic conductivity
- 2010
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Ingår i: APPLIED PHYSICS LETTERS. - : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 97:7, s. 073103-
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Tidskriftsartikel (refereegranskat)abstract
- The substitution of oxygen for carbon in Ti2AlC M((n+1))AX(n) (MAX) phase, forming Ti2AlC1-xOx, has recently been reported. In this paper we simulate the effect of oxygen incorporation on mechanical and electronic properties using ab initio calculations. While the mechanical properties are not sensitive to the change in composition, the electronic properties can be tuned by varying the oxygen concentration. As the concentration increases, the conduction changes from in plane, typical of MAX phases, to conduction also in the c-direction. The conduction along c passes from insulating to n-type and then finally to p-type. These findings reveal an anisotropic semiconducting material.
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| 9. |
- Abrasonis, Gintautas, et al.
(författare)
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Nanoscale precipitation patterns in carbon-nickel nanocomposite thin films: Period and tilt control via ion energy and deposition angle
- 2010
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Ingår i: JOURNAL OF APPLIED PHYSICS. - : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 108:4, s. 043503-
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Tidskriftsartikel (refereegranskat)abstract
- Periodic precipitation patterns in C:Ni nanocomposites grown by energetic ion codeposition are investigated. Films were grown at room temperature by ionized physical vapor deposition using a pulsed filtered cathodic vacuum arc. We reveal the role of the film composition, ion energy and incidence angle on the film morphology using transmission electron microscopy and grazing incidence small angle x-ray scattering. Under these growth conditions, phase separation occurs in a thin surface layer which has a high atomic mobility due to energetic ion impacts. This layer is an advancing reaction front, which switches to an oscillatory mode, producing periodic precipitation patterns. Our results show that the ion induced atomic mobility is not random, as it would be in the case of thermal diffusion but conserves to a large extent the initial direction of the incoming ions. This results in a tilted pattern under oblique ion incidence. A dependence of the nanopattern periodicity and tilt on the growth parameters is established and pattern morphology control via ion velocity is demonstrated.
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| 10. |
- Amin Yavari, S., et al.
(författare)
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Layer by layer coating for bio-functionalization of additively manufactured meta-biomaterials
- 2020
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Ingår i: Additive Manufacturing. - : Elsevier BV. - 2214-8604 .- 2214-7810. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing has facilitated fabrication of complex and patient-specific metallic meta-biomaterials that offer an unprecedented collection of mechanical, mass transport, and biological properties as well as a fully interconnected porous structure. However, applying meta-biomaterials for addressing unmet clinical needs in orthopedic surgery requires additional surface functionalities that should be induced through tailor-made coatings. Here, we developed multi-functional layer-by-layer coatings to simultaneously prevent implant-associated infections and stimulate bone tissue regeneration. We applied multiple layers of gelatin- and chitosan-based coatings containing either bone morphogenetic protein (BMP)-2 or vancomycin on the surface of selective laser melted porous structures made from commercial pure Titanium (CP Ti) and designed using a triply periodic minimal surface (i.e., sheet gyroid). The additive manufacturing process resulted in a porous structure and met the the design values comparatively. X-ray photoelectron spectroscopy spectra confirmed the presence and composition of the coating layers. The release profiles showed a continued release of both vancomycin and BMP-2 for 2–3 weeks. Furthermore, the developed meta-biomaterials exhibited a very strong antibacterial behavior with up to 8 orders of magnitude reduction in both planktonic and implant-adherent bacteria and no signs of biofilm formation. The osteogenic differentiation of mesenchymal stem cells was enhanced, as shown by two-fold increase in the alkaline phosphatase activity and up to four-fold increase in the mineralization of all experimental groups containing BMP-2. Eight-week subcutaneous implantation in vivo showed no signs of a foreign body response, while connective tissue ingrowth was promoted by the layer-by-layer coating. These results unequivocally confirm the superior multi-functional performance of the developed biomaterials.
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