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- Samuelsson, Mattias
(author)
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Fundamental aspects of HiPIMS under industrial conditions
- 2012
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Doctoral thesis (other academic/artistic)abstract
- Fundamental aspects of the high power impulse magnetron sputtering (HiPIMS) process and its implication for film growth under industrial conditions have been studied. The emerging HiPIMS technique exhibits a higher plasma density and an enhanced degree of ionisation of sputtered material as compared to conventional direct current magnetron sputtering (DCMS). The increased ionisation permits control of the deposition flux and facilitates an intense ion bombardment of the growing films. The latter allows for growth of well adherent, smooth, and dense thin films. Moreover, the technique offers increased stability of reactive processes, control of film phase constitution as well as tailoring of e.g. optical and mechanical properties.In the present work, it was shown, for eight different metals (Al, Ti, Cr, Cu, Zr, Ag, Ta, and Pt), that films grown using HiPIMS exhibit a 5-15% higher density than films grown using DCMS under otherwise identical conditions. Through simulations of the fundamental ionisation processes in the plasma discharge, a correlation between high ionisation degree and film densification was established. The densification was suggested to be a consequence of increased ion irradiation of the growing films in the HiPIMS case. This knowledge was used to investigate the degree of ionisation in the deposition flux required for film modifications. Using a hybrid process, where DCMS and HiPIMS were combined on a single Cr cathode, independent control of the degree of ionisation from other experimental parameters was achieved. The results showed that the majority of the ion irradiation induced modifications of surface related film properties occurred when ~40% of the total average power was supplied by the HiPIMS generator. Under such conditions, the power normalised deposition rate was found to be ~80% of that of DCMS. This was attributed to a reduction in back-attracted ionised sputtered material, which is considered to be the main reason for the low deposition rate of HiPIMS. Thus, enhanced film properties were attainable largely without sacrificing deposition rate.Compound carbide and boride films were synthesised using both reactive processes and compound sources. Reactive deposition of TiC/a-C:H thin films using C2H2 as reactive gas, i.e. carbon source, was demonstrated. It was found that the high plasma density processes (i.e. HiPIMS) facilitated growth conditions for the film structure formation closer to thermodynamic equilibrium than did processes exhibiting lower plasma densities (i.e. DCMS). This was manifested in a high stoichiometry of the carbide phase, whilst excess a-C was removed by physical sputtering. Moreover, the feasibility of using HiPIMS for thin film growth from a compound source, obtaining the same composition in the films as the sputtering source, was demonstrated through synthesis of ZrB2 films.
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| 2. |
- Samuelsson, Mattias, 1976-, et al.
(author)
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Growth of Ti-C nanocomposite films by reactive high power impulse magnetron sputtering under industrial conditions
- 2012
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In: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 206:8-9, s. 2396-2402
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Journal article (peer-reviewed)abstract
- Titanium carbide (TiC) films were deposited employing high power impulse magnetron sputtering (HiPIMS) and direct current magnetron sputtering (DCMS) in an Ar-C2H2 atmosphere of various compositions. Analysis of the structural, bonding and compositional characteristics revealed that the deposited films are either TiC and hydrogenated amorphous carbon (a-C:H) nanocomposites, nanocrystalline TiC, or Ti/Tic, depending on the C/Ti ratio. It was found that Ti-C films grown by HiPIMS show a C/Ti ratio of close to 1 for a wide C2H2 flow range (4-15 sccm), with free C ranging from 0 to 20%. Thus, films ranging from near stoichiometric single phase TiC to TiC/a-C:H nanocomposites can be synthesized. This was not the case for DCMS, where films grown using similar deposition rates as for HiPIMS formed larger fractions of amorphous C matrix, thus being nanocomposites in the same C2H2 (above 4 sccm) flow range. For a C/Ti ratio of 1 the resistivity is low (4-8 x 10(2) mu Omega cm) for the HiPIMS films, and high (>100x 10(2) mu Omega cm) for the DCMS films. The hardness also shows a big difference with 20-27 and 6-10 GPa for HiPIMS and DCMS grown films, respectively.
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| 3. |
- Samuelsson, Mattias, 1976-
(author)
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High power impulse magnetron sputtering under industrial conditions
- 2011
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Licentiate thesis (other academic/artistic)abstract
- In this thesis, the recent development step of magnetron sputtering, termed high power impulse magnetron sputtering (HiPIMS) has been studied. Compared to conventional magnetron sputtering HiPIMS provides a higher plasma density which can ionise the sputtered material. The beneficial influence of the coating properties due to this ionisation has been extensively shown in academic publications. Here, industrial conditions, i.e. no substrate heating and high vacuum conditions have been used during the studies, of which one was performed in an industrial deposition system.For eight metallic targets, films were deposited with HiPIMS and conventional sputtering. The films were evaluated by Rutherford back scattering analysis, scanning electron microscopy, and profilometry. It was found that the density of the HiPIMS grown films exhibited a statistically significant higher density of approximately 5-15% in comparison to films deposited using DCMS under identical conditions. A global plasma model was employed to evaluate the degree of ionisation for some of the target materials, and process conditions used in the study. Conformity between density increase and degree of ionisation as assessed by the plasma model was confirmed.The influence of using HiPIMS during reactive sputtering of TiC was also studied. A metallic Ti target was sputtered in a gas mixture of Ar and C2H2. The coatings were evaluated by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, 4 point probe resistivity measurements, and nanoindentation. The coatings were found to be nanocomposite TiC/a-C:H. For the HiPIMS process the transition zone between metallic and compound target states was found to be significantly expanded over a wide reactive gas flow range. The implications of choice of deposition method for coating composition, chemical structure, as well as electrical and mechanical properties were evaluated for DCMS and HiPIMS. The process behaviour was suggested to be due to the pulsed nature of the HiPIMS, the high plasma density, and ion content of the particles reaching the substrate.
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| 4. |
- Vedantha Krishna, Amogh, 1990-, et al.
(author)
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Quality assurance of stereolithography based biocompatible materials for dental applications
- 2023
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In: Surface Topography: Metrology and Properties. - Bristol : Institute of Physics Publishing (IOPP). - 2051-672X. ; 11:1
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Journal article (peer-reviewed)abstract
- Additive Manufacturing (AM) is increasingly being used in healthcare sectors for its potential to fabricate patient-specific customized implants, and specifically in dentistry, AM finds its applications in maxillofacial implants, dentures, and other prosthetic aids. However, in most applications, AM is largely being used for prototyping purposes. The full-scale realization of AM can only be achieved if the downsides of AM are addressed and resolved. Hence this paper focuses on providing a detailed analysis of surface quality, dimensional accuracy, and mechanical properties of the biocompatible material produced, using the Stereolithography (SLA) method for a dental application. For quality analysis, test artefacts were produced, and the quality was assessed before and after the sterilization process. The results suggest that micro-surface roughness essential for cell growth is similar for all build inclinations and well within the control limit required for effective bone regeneration. Multi-scale surface characterization revealed that the sterilization process involving heat can potentially alter the micro-roughness features of resin-based materials. The results from the dimensional analysis show that the SLA parts produced had negligible dimensional deviations from the CAD model to the printed parts and were unaffected by the sterilization process. The tensile test results suggest that the part orientation does not affect the tensile strength and that the sterilization process seems to have an insignificant effect on the tensile properties of the SLA parts. Furthermore, the results were validated by producing a membrane barrier for Guided Bone Regeneration (GBR). The validation results showed that excess resin entrapment was due to the geometrical design of the membrane barrier. In conclusion, this paper provides an overview of quality variations that can help in optimizing the AM and sterilization process to suit dental needs. © 2023 IOP Publishing Ltd.
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| 5. |
- Wälivaara, Bengt, et al.
(author)
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Automated monitoring of groundwater contamination along salted roads
- 2006
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Reports (pop. science, debate, etc.)abstract
- This report describes the results from preliminary laboratory investigations of ground water samples obtained during the autumn of 2004 from national road 67 Heby in Sweden, using a novel liquid sensor technology, "Electronic Tongue" (ET), and a commercial conductivity probe. Partial least squares regression (PLS) combined with principal component analysis (PCA) was used to build a model to quantify ET data using ion concentrations determined by conventional laboratory analysis as well as measured conductivity data. Results showed very good correlation between ET data and chlorine concentrations in field samples as well as conductivity data. In addition to chlorine concentration, results also indicated that ET has the potential to detect and warn for other types of contaminants in ground water. The reports also describes the planned installation in June 2005 of a complete system for remote monitoring of chloride concentration via the Internet using a similar technology platform as for the VTI frost monitoring system (Tjäl 2000).
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| 6. |
- Wälivaara, Bengt
(author)
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Validering av VTI-PFT version 4 : mätningar på plana och profilerade vägmarkeringar
- 2007
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Reports (other academic/artistic)abstract
- This study shows that the PFT (Portable Friction Tester) in its fourth version, featuring an improved mechanical design with a new measurement tire, similar to previous versions, is a user friendly and robust method with excellent reproducibility. The results indicate very low variation between individual instruments and an almost negligible influence by the operator. Correlation studies with the SRT pendulum on plane road markings were conducted using a set of different road markings commonly used in Sweden of varying age and quality. Results indicate a linear relationship according to the following: SRT = 78.6*PFT + 9.2 ± 9.0 A correlation study using two individual PFT instruments with different operators on a set of commonly used profiled road markings in Sweden showed an excellent repeatability and a dynamic measurement range similar to plane road markings. The results clearly indicate that the PFT is suitable to use as a stand-alone method for objective assessment of skid resistance of plane as well as of profiled road markings, thus eliminating the need of the SRT pendulum.
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