| 1. |
- Björk, Emma, et al.
(författare)
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Formation of block-copolymer-templated mesoporous silica
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0021-9797 .- 1095-7103. ; 521, s. 183-189
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Tidskriftsartikel (refereegranskat)abstract
- In situ attenuated total reflectance Fourier transform infrared spectroscopy is used to monitor the chemical evolution of the mesoporous silica SBA-15 from hydrolysis of the silica precursor to final silica condensation after the particle formation. Two silica precursors, tetraethyl orthosilicate (TEOS) or sodium metasilicate (SMS) were used, and the effects of additive (heptane and NH4F) concentrations were studied. Five formation stages are identified when TEOS is used as the precursor. The fourth stage correlates with the appearance and evolution of diffraction peaks recorded using in situ small angle X-ray diffraction. Details of the formed silica matrix are observed, e.g. the ratio between six-fold cyclic silica rings and linear bonding increases with the NH4F concentration. The TEOS hydrolysis time is independent of the NH4F concentration for small amounts of heptane, but is affected by the size of the emulsion droplets when the heptane amount increases. Polymerization and condensation rates of both silica precursors are affected by the salt concentration. Materials synthesized using SMS form significantly faster compared to TEOS-materials due to the pre-hydrolysis of the precursor. The study provides detailed insights into how the composition of the synthesis solution affects the chemical evolution and micellar aggregation during formation of mesoporous silica. (C) 2018 Elsevier Inc. All rights reserved.
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| 2. |
- Eriksson, Fredrik, et al.
(författare)
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Ion-assisted magnetron sputter deposition of B4C doped Ni/Ti multilayer mirrors
- 2018
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Ingår i: ADVANCES IN X-RAY/EUV OPTICS AND COMPONENTS XIII. - : SPIE-INT SOC OPTICAL ENGINEERING. - 9781510620926
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Konferensbidrag (refereegranskat)abstract
- Ion-assisted magnetron sputter deposition have been used to deposit Ni/Ti multilayer neutron mirrors. Improved interface widths were obtained by using B4C doping, to eliminate nanocrystallites by amorphization, and a two-stage modulated ion assistance, to obtain abrupt and smooth interfaces. In situ high-energy wide angle X-ray scattering during multilayer depositions was used to monitor the microstructure evolution and to determine the most favourable growth conditions. Post growth X-ray reflectometry in combination with high resolution transmission electron microscopy confirmed the amorhization and revealed significant improvements in interface widths and reduction of kinetic roughening upon applying B4C doping and modulated ion assistance during growth. Significant improvement of neutron supermirror performance is predicted by employing this technique.
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| 3. |
- Eriksson, Fredrik, 1975-, et al.
(författare)
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Morphology control in Ni/Ti multilayer neutron mirrors by ion-assisted interface engineering and B4C incorporation
- 2023
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Ingår i: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 13:5, s. 1424-1439
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Tidskriftsartikel (refereegranskat)abstract
- The optical contrast and minimum layer thickness of Ni/Ti broadband neutron multilayer supermirrors is usually hampered by an interface width, typically 0.7 nm, caused by nanocrystallites, interdiffusion, and/or intermixing. We explore the elimination of nanocrystallites in combination with interface smoothening by modulation of ion assistance during magnetron sputter deposition of 0.8 to 6.4 nm thick Ni and Ti layers. The amorphization is achieved through incorporation of natural B4C where B and C preferably bond to Ti. A two-stage substrate bias was applied to each layer; -30 V for the initial 1 nm followed by -100 V for the remaining part, generating multilayer mirrors with interface widths of 0.40-0.45 nm. The results predict that high performance supermirrors with m-values as high as 10 are feasible by using 11B isotope-enriched B4C combined with temporal control of the ion assistance.
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| 4. |
- Höglund, Carina, 1981-, et al.
(författare)
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Topotaxial growth of Ti2AlN by solid state reaction in AlN/Ti(0001) multilayer thin films
- 2007
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:174106
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Tidskriftsartikel (refereegranskat)abstract
- The formation of Ti2AlN by solid state reaction between layers of wurtzite-AlN and α-Ti was characterized by in situ x-ray scattering. The sequential deposition of these layers by dual magnetron sputtering onto Al2O3(0001) at 200 °C yielded smooth, heteroepitaxial (0001) oriented films, with abrupt AlN/Ti interfaces as shown by x-ray reflectivity and Rutherford backscattering spectroscopy. Annealing at 400 °C led to AlN decomposition and diffusion of released Al and N into the Ti layers, with formation of Ti3AlN. Further annealing at 500 °C resulted in a phase transformation into Ti2AlN(0001) after only 5 min.
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| 5. |
- Landälv, Ludvig, 1982-, et al.
(författare)
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Phase evolution of radio frequency magnetron sputtered Cr-rich (Cr,Zr)(2)O-3 coatings studied by in situ synchrotron X-ray diffraction during annealing in air or vacuum
- 2019
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Ingår i: Journal of Materials Research. - : CAMBRIDGE UNIV PRESS. - 0884-2914 .- 2044-5326. ; 34:22, s. 3735-3746
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Tidskriftsartikel (refereegranskat)abstract
- The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr0.28Zr0.10O0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO2 formation starting at similar to 750-800 degrees C, followed by decomposition of the alpha-Cr2O3 structure in conjunction with bcc-Cr formation, starting at similar to 950 degrees C. The resulting coating after annealing to 1140 degrees C is a mixture of t-ZrO2, m-ZrO2, and bcc-Cr. The air-annealed sample shows t-ZrO2 formation starting at similar to 750 degrees C. The resulting coating after annealing to 975 degrees C is a mixture of t-ZrO2 and alpha-Cr2O3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO2 fraction compared with alpha-Cr2O3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 degrees C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.
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| 6. |
- Moreno, Maiara, 1993-, et al.
(författare)
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Strain and phase evolution in TiAlN coatings during high-speed metal cutting : An in operando high-energy x-ray diffraction study
- 2024
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 263
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Tidskriftsartikel (refereegranskat)abstract
- We report on phase and strain changes in Ti1-xAlxN (0 ≤ x ≤ 0.61) coatings on cutting tools during turning recorded in operando by high-energy x-ray diffractometry. Orthogonal cutting of AISI 4140 steel was performed with cutting speeds of 360–370 m/min. Four positions along the tool rake face were investigated as a function of time in cut. Formation of γ-Fe in the chip reveals that the temperature exceeds 727 °C between the tool edge and the middle of the contact area when the feed rate is 0.06 mm/rev. Spinodal decomposition and formation of wurtzite AlN occurs at the positions of the tool with the highest temperature for the x ≥ 0.48 coatings. The strain evolution in the chip reveals that the mechanical stress is largest closest to the tool edge and that it decreases with time in cut for all analyzed positions on the rake face. The strain evolution in the coating varies between coatings and position on the rake face of the tool and is affected by thermal stress as well as the applied mechanical stress. Amongst others, the strain evolution is influenced by defect annihilation and, for the coatings with highest Al-content (x ≥ 0.48), phase changes.
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| 7. |
- Nayak, Sanjay Kumar, et al.
(författare)
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Dynamic evolution of internal stress, grain growth, and crystallographic texture in arc-evaporated AlTiN thin films using in-situ synchrotron x-ray diffraction
- 2024
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Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 272
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the nucleation and growth of polycrystalline thin films is a long-standing goal. Numerous studies have been done to determine the grain size, stress, and the ideal crystallographic orientation in films. The majority of past studies have either employed an ex-situ methodology or only monitor the development of macroscopic stress in real-time. There has never been any research done on the simultaneous changes in crystallographic texture, grain size, and microscopic stress in polycrystalline thin films. In this study, we investigated the generation and temporal evolution of texture, grain size, and internal stress in cathodic arc evaporated Al0.50Ti0.50N thin films using a bespoke deposition apparatus designed for use with 2-dimensional synchrotron x-ray diffraction technique. The influence of the substrate temperature is investigated in terms of the emergence and development of texture, grain size and stress evolution. A dynamic evolution of the crystallographic texture is observed as the overall film thickness varies. We clearly resolved two regime of films growth based on stress evolution. Beyond a threshold grain size (similar to 14 nm), the stress scales inversely to the average grain sizes, and as the film thickness increases, immediate compressive stress relaxation was seen. An extensive ex-situ evaluation of thin films using electron microscopies and electron diffraction was performed to support the in-situ x-ray diffraction results.
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| 8. |
- Paul, Biplab, et al.
(författare)
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Mechanism of Formation of the Thermoelectric Layered Cobaltate Ca3Co4O9 by Annealing of CaO-CoO Thin Films
- 2015
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Ingår i: Advanced Electronic Materials. - : Wiley-Blackwell. - 2199-160X. ; 1:3
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Tidskriftsartikel (refereegranskat)abstract
- The layered cobaltate Ca3Co4O9 is of interest for energy-harvesting and heat-conversion applications because of its good thermoelectric properties and the fact that the raw materials Ca and Co are nontoxic, abundantly available, and inexpensive. While single-crystalline Ca3Co4O9 exhibits high Seebeck coefficient and low resistivity, its widespread use is hampered by the fact that single crystals are too small and expensive. A promising alternative approach is the growth of highly textured and/or epitaxial Ca3Co4O9 thin films with correspondingly anisotropic properties. Here, we present a two-step sputtering/annealing method for the formation of highly textured virtually phase-pure Ca3Co4O9 thin films by reactive cosputtering from Ca and Co targets followed by an annealing process at 730 °C under O2-gas flow. The thermally induced phase transformation mechanism is investigated by in situ time-resolved annealing experiments using synchrotron-based 2D X-ray diffraction (XRD) as well as ex situ annealing experiments and standard lab-based XRD. By tuning the proportion of initial CaO and CoO phases during film deposition, the method enables synthesis of Ca3Co4O9 thin films as well as CaxCoO2. With this method, we demonstrate production of epitaxial Ca3Co4O9 thin films with in-plane electrical resistivity of 6.44 mΩ cm and a Seebeck coefficient of 118 μV K−1 at 300 K.
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| 9. |
- Schroeder, Jeremy, et al.
(författare)
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Thermal stability of epitaxial cubic-TiN/(Al,Sc)N metal/semiconductor superlattices
- 2015
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Ingår i: Journal of Materials Science. - : Springer Verlag (Germany). - 0022-2461 .- 1573-4803. ; 50:8, s. 3200-3206
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Tidskriftsartikel (refereegranskat)abstract
- We report on the thermal stability of epitaxial cubic-TiN/(Al,Sc)N metal/semiconductor superlattices with the rocksalt crystal structure for potential plasmonic, thermoelectric, and hard coating applications. TiN/Al0.72Sc0.28N superlattices were annealed at 950 and 1050 A degrees C for 4, 24, and 120 h, and the thermal stability was characterized by high-energy synchrotron-radiation-based 2D X-ray diffraction, high-resolution (scanning) transmission electron microscopy [HR(S)/TEM], and energy dispersive X-ray spectroscopy (EDX) mapping. The TiN/Al0.72Sc0.28N superlattices were nominally stable for up to 4 h at both 950 and 1050 A degrees C. Further annealing treatments for 24 and 120 h at 950 A degrees C led to severe interdiffusion between the layers and the metastable cubic-Al0.72Sc0.28N layers partially transformed into Al-deficient cubic-(Al,Sc)N and the thermodynamically stable hexagonal wurtzite phase with a nominal composition of AlN (h-AlN). The h-AlN grains displayed two epitaxial variants with respect to c-TiN and cubic-(Al,Sc)N. EDX mapping suggests that scandium has a higher tendency for diffusion in TiN/(Al,Sc)N than titanium or aluminum. Our results indicate that the kinetics of interdiffusion and the cubic-to-hexagonal phase transformation place constraints on the design and implementation of TiN/(Al,Sc)N superlattices for high-temperature applications.
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