| 1. |
- Götz, Inga Katharina, 1992-, et al.
(författare)
-
Reactive metal additive manufacturing : Surface near ZrN - metallic glass composite formation and mechanical properties
- 2023
-
Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 66
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- ZrN formation in a Zr-based bulk metallic glass is observed after processing using reactive laser powder bed fusion. Two processing routes employing nitrogen as a reactive process gas are explored: (1) Standard inert processing in argon followed by reactive remelting in nitrogen and (2) reactive processing in nitrogen. Incorporation of nitrogen is depth-dependent and both approaches result in a dispersion of ZrN nanocrystals in the amorphous matrix close to the surface. The process parameters can be adjusted to control the volume fraction of crystalline phases formed. Hence, it is shown that reactive additive manufacturing can be utilised to form bulk metallic glass-ceramic composites in surface near regions. Thereby we demonstrate that the reactive gas atmosphere utilised during additive manufacturing enables local tailoring of structure, composition, and mechanical properties in the vicinity of the surface.
|
|
| 2. |
- Kaur, Rajdeep, 1997-
(författare)
-
Case Studies in Ion Beam Assisted Nanostructure Engineering
- 2024
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Beams of energetic ions can be used for material analysis and modification. It provides us with a tool featuring unique control over the area, depth and amount of damage in the material. This property of ion beams can be used to generate desired changes in material properties or form nanostructures with specific characteristics in the material. While the modification of materials through the irradiation of GeV energy ions has been extensively researched, it is worth considering MeV ion irradiation for ion beam-based material modification. Accelerators with the ability to deliver ions in the MeV energy regime, such as tandem accelerators with a few MV terminal voltage and cyclotrons, are more accessible, easier to maintain and already available in industrial spaces. Thus, a comprehensive study on whether the damage caused in different material systems by MeV ion irradiation can be used for nanostructure engineering needs to be performed. In this thesis, the formation of nanostructures by MeV ion irradiation in two different materials is studied. The dependence of the nanostructures formed on the ion parameters such as ion type and energy is investigated for two material systems. In the first study, we investigate the formation of nanostructures on the surface of a model system, i.e., single crystals of CaF2. In the second study, we investigate the formation of etchable ion tracks in polyimide membranes. Nanoscale pores and channels, that can be formed from these etchable ion tracks, are expected to be the basis of next-generation detectors, biosensors and DNA/RNA sequencing. In the case of both materials, three distinct regions of ion-induced damage are identified after irradiation. The thresholds dividing these distinct regions of damage are dependent on ion velocity. Thus, electronic stopping power thresholds for the formation of nanostructures in materials are observed to be lower for MeV ions than for GeV ions.
|
|
| 3. |
|
|
| 4. |
- Ström, Petter, 1989-
(författare)
-
Material characterization for magnetically confined fusion : Surface analysis and method development
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The dream of abundant clean energy has brought scientists and laypeople alike to ponder the possibilities of nuclear fusion since it was established as the energy source of the stars in 1939. Starting from the mid-twentieth century, significant effort has been put into overcoming the technological challenges related to the construction of a power plant, but initial optimism has faded somewhat due to a notable absence of practical outcomes. Nevertheless, the research continues and progress is made slowly but surely.The present work deals with a small part of the fusion puzzle, namely the materials to be used in the first wall surrounding a magnetically confined plasma. Carbon, which has historically been considered as the most viable element for this role, has been ruled out due to issues with plasma-induced erosion, hydrocarbon formation and a buildup of thick deposited material layers on wall components. The latter two lead to an unacceptable accumulation of radioactive tritium, both in the deposited layers and in dust particles. A metal wall, which would alleviate these particular problems but increase the severity of others, is therefore envisioned for a future demonstration reactor.Three contributions to the overall research effort are made through this thesis. First, an increased understanding of plasma-induced erosion of so-called reduced activation ferritic-martensitic steels and preferential sputtering of light material components is provided. High-resolution ion beam analysis and microscopy methods are used to examine samples of such a steel after exposure to plasma under controlled circumstances. Model films consisting of a mixture of iron and tungsten deposited on silicon substrates are also studied as they constitute simpler systems where the effects of interest may be simulated. The knowledge obtained is necessary for an assessment of the possibility to use reduced activation steel as a plasma-facing material in specific regions of a reactor wall.The second contribution consists of reports on the composition of deposited material layers on wall components retrieved from the plasma confinement experiments JET and TEXTOR. These provide limited conclusions on the range and rate of material erosion, transport and deposition in two cases.Finally, a detection system for the ion beam technique elastic recoil detection analysis has been assembled, tested and put into operation. In addition to improving the quality of analyses performed on fusion-related materials, the system has become an established tool available for users of the 5 MV electrostatic pelletron accelerator at Uppsala University’s Tandem Laboratory.”
|
|
| 5. |
- Weckmann, Armin, et al.
(författare)
-
Global material migration in tokamaks : patterns, material balance and transport mechanisms in TEXTOR
- 2017
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- As the last experiment before the final shutdown of the TEXTOR tokamak, equipped with all-graphite plasma-facing components (PFCs), MoF6 had been injected into the vacuum vessel. During decommissioning all PFCs became available for surface studies, enabling detailed mapping of previously injected Mo, W and intrinsic 625 Inconel metals. As a result, detailed deposition patterns for these metals were obtained, revealing a number of findings: a) High-Z metals are mainly globally deposited, with concentrations decaying exponentially with distance from the injection source; b) the decay length is of the order of 0.1 m on the main PFC and 1.0 m on the receded PFC; c) ion flow velocities co-decide the position of maximum deposition. Modelling with ERO shows exponential decay. Simulated decay lengths are between 0.15 – 1.30 m, depending on the anomalous cross field diffusion coefficient. Extensive measurements of Mo have been undertaken in order to quantify the amounts deposited on the graphite PFCs, showing that the ratio of local to global deposited high-Z metals is 0.3-0.4. However, only up to 20% of the injected Mo could be detected on all the PFCs. A large fraction of injected Mo may have been pumped out before being deposited. The bumper limiter is found to be the major repository for all probed elements. For W and F, this is solely due to the limiter size – the areal concentration is not enhanced. For Mo, Inconel metals, 15N and D the areal concentration on the bumper limiter is higher than on the toroidal belt limiter ALTII acting as main PFC.
|
|
