| 1. |
- Salomonsson, Anette, et al.
(författare)
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Nanoparticles for long-term stable, more selective MISiCFET gas sensors
- 2005
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 107:2, s. 831-838
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of metal-oxide nanoparticles and utilization of these particles as gate materials for field-effect sensor devices is reported. Improved selectivity to specific gases is expected by modulating the size of the oxide nanoparticles or impregnating them with catalytic metals. Another objective is to improve the long-term thermal stability of the sensors, since the metal loaded nanoparticles may prevent thermally induced restructuring of the gate layer, which is often a problematic issue for the catalytic metal layers. Because of its reasonably high electrical conductivity, which is especially important for the capacitive gas sensors, ruthenium dioxide has been identified to be one of the potential candidates as gate material for the field-effect sensor devices. Interestingly, this material has been found to change its resistivity in different gaseous ambients. When used as a gate material, sensitivity to reducing gases has been observed for the RuO2/SiO2/4H-SiC capacitors. Changes in the resistivity of the films due to various gas exposures have also been recorded. Morphological studies of nanoparticles (SiO2 and Al2O3), loaded or impregnated with catalytic metals (e.g. Pt), have been performed.
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| 2. |
- Barbier, Christophe, et al.
(författare)
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Numerical investigation of folding of coated papers
- 2005
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Ingår i: Composite Structures. - : Elsevier. ; 67:4, s. 383-394
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Tidskriftsartikel (refereegranskat)abstract
- Folding of coated paper is examined numerically using the finite element method. Particular emphasis is put on the behaviour of field variables relevant for cracking of the coating layers. In the numerical analysis, the basepaper is modelled as an anisotropic elasticplastic material (both elastic and plastic anisotropy is accounted for) while the constitutive behaviour of the coating layers are approximated by classical (Mises) elastoplasticity. The numerical results suggest, among other things, that particular forms of plastic anisotropy can substantially reduce the maximum strain levels in the coating. It is also shown that delamination buckling, in the present circumstances, will have a very small influence on the strain levels in the coating layer subjected to high tensile loading
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| 3. |
- Barbier, Christophe, 1974-, et al.
(författare)
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On material characterization of paper coating materials by microindentation testing
- 2005
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Ingår i: JCT. - Boston : Springer. - 0361-8773. ; 2:6, s. 463-471
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Tidskriftsartikel (refereegranskat)abstract
- Microindentation as a method for determining important material properties of paper coating materials is studied experimentally and numerically. The bulk of the investigation is concentrated upon the short-lived elastic part of a spherical indentation test, but determination of the failure stress of the coating is also discussed. The results indicate that microindentation can be a powerful tool for material characterization of these materials, but only if careful efforts are made to account for the influence from plasticity as well as from boundary effects
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| 4. |
- Barbier, Christophe, 1974-, et al.
(författare)
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On the effect of high anisotropy at folding of coated papers
- 2007
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Ingår i: Composite structures. - : Elsevier. - 0263-8223 .- 1879-1085. ; 72:3, s. 330-338
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Tidskriftsartikel (refereegranskat)abstract
- A finite element procedure, developed in order to account for the effect of high anisotropy at folding of coated papers, is presented. The anisotropic behaviour (with very low stiffness in the thickness direction) is modelled using stiff structural elements (trusses and beams). The numerical results indicate that high elastic anisotropy leads to lower strain levels at folding than reported in previous analyses where this effect was not accounted for. High plastic anisotropy, on the other hand, will contradict this result
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| 5. |
- Almgren, Karin, et al.
(författare)
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Role of fibre-fibre and fibre-matrix adhesion in stress transfer in composites made from resin-impregnated paper sheets.
- 2009
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Ingår i: International Journal of Adhesion and Adhesives. - : Elsevier BV. - 0143-7496 .- 1879-0127. ; 29:5, s. 551-557
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Tidskriftsartikel (refereegranskat)abstract
- Paper-reinforced plastics are gaining increased interest as packaging materials, where mechanical properties are of great importance. Strength and stress transfer in paper sheets are controlled by fibre-fibre bonds. In paper-reinforced plastics, where the sheet is impregnated with a polymer resin, other stress-transfer mechanisms may be more important. The influence of fibre-fibre bonds on the strength of paper-reinforced plastics was therefore investigated. Paper sheets with different degrees of fibre-fibre bonding were manufactured and used as reinforcement in a polymeric matrix. Image analysis tools were used to verify that the difference in the degree of fibre-fibre bonding had been preserved in the composite materials. Strength and stiffness of the composites were experimentally determined and showed no correlation to the degree of fibre-fibre bonding, in contrast to the behaviour of unimpregnated paper sheets. The degree of fibre-fibre bonding is therefore believed to have little importance in this type of material, where stress is mainly transferred through the fibre-matrix interface.
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| 6. |
- Desmaris, Vincent, 1977, et al.
(författare)
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Microfabrication Technology for All-Metal Sub-mm and THz Waveguide Receiver Components
- 2008
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Ingår i: In Proceedings of The 19th International Symposium on Space Terahertz Technology, Groningen, 28-30 April, 2008, ed. W. Wild, Space Research Organization of the Netherlands (SRON). ; part I, s. 342-345
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Konferensbidrag (refereegranskat)abstract
- A novel technology for manufacturing of micromachined all-metal waveguide circuits and structures for the frequency band from 200 up to 7000 GHz (Sub-Millimeter and THz) is presented. The waveguide circuits are formed using metal electroplating with preceding sputtering of a thin metal film seed layer over a photo-lithographically patterned thick SU-8 photo-resist. The process provides possibility of making 3-dimensional structures via facilitating of multi-level (layered) designs. Surface roughness of the THz waveguide structure was demonstrated to be below 0.1 µm. This technology was used to build a state-of-the art waveguide balanced 1.3 THz Hot Electron Bolometer mixer and other application for radio astronomy instrumentation.
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| 7. |
- Lindskog, P, et al.
(författare)
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Optimization as a tool for characterization of advanced constitutive models describing powder compaction
- 2007
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Ingår i: Proceedings of the Euro PM 2007 Congress and Exhibition. - Shrewsbury : European Powder Metallurgy Association. ; , s. 381-386
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Konferensbidrag (refereegranskat)abstract
- The applicability of optimization procedures used in combination with advanced constitutive models, describing dry pressing powder compaction, is investigated by aid of standard finite ele- ment and optimization commercial packages. It is found that, at fairly general conditions, this can be expected to be a very advantageous approach at material characterization
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| 8. |
- Norman, Peter, et al.
(författare)
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A sophisticated platform for characterization, monitoring and control of machining
- 2006
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Ingår i: Measurement science and technology. - BRISTOL, ENGLAND : IOP Publishing. - 0957-0233 .- 1361-6501. ; 17:4, s. 847-854
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Tidskriftsartikel (refereegranskat)abstract
- The potential for improving the performance of machine tools is considerable. However, for this to be achieved without tool failure or product damage, the process must be sufficiently well understood to enable real-time monitoring and control to be applied. A unique sophisticated measurement platform has been developed and applied to two different machining centres, particularly for high-speed machining up to 24 000 rpm. Characterization and on-line monitoring of the dynamic behaviour of the machining processes has been carried out using both contact-based methods (accelerometer, force sensor) and non-contact methods (laser Doppler vibrometry and magnetic shaker) and numerical simulation (finite element based modal analysis). The platform was applied both pre-process and on-line for studying an aluminium testpiece based on a thin-walled aerospace component. Stability lobe diagrams for this specific machine/component combination were generated allowing selection of optimal process parameters giving stable cutting and metal removal rates some 8-10 times higher than those possible in unstable machining. Based on dynamic characterization and monitoring, a concept for an adaptive control with constraints based machine tool controller has been developed. The developed platform can be applied in manifold machining situations. It offers a reliable way of achieving significant process improvement
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| 9. |
- Frodelius, Jenny, et al.
(författare)
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Ti2AlC coatings deposited by High Velocity Oxy-Fuel spraying
- 2008
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 202:24, s. 5976-5981
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Tidskriftsartikel (refereegranskat)abstract
- High Velocity Oxy-Fuel has been utilized to spray coatings from Ti2AlC (MAXTHAL 211®) powders. X-ray diffraction showed that the coatings consist predominantly of Ti2AlC with inclusions of the phases Ti3AlC2, TiC, and Al–Ti alloys. The fraction of Ti2AlC in coatings sprayed with a powder size of 38 μm was found to increase with decreasing power of the spraying flame as controlled by the total gas flow of H2 and O2. A more coarse powder (56 μm) is less sensitive to the total gas flow and retains higher volume fraction of MAX-phase in the coatings, however, at the expense of increasing porosity. X-ray pole figure measurements showed a preferred crystal orientation in the coatings with the Ti2AlC (000l) planes aligned to the substrate surface. Bending tests show a good adhesion to stainless steel substrates and indentation yields a hardness of 3–5 GPa for the coatings sprayed with a powder size of 38 μm.
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| 10. |
- Mouzon, Johanne, et al.
(författare)
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Comparison between slip-casting and uniaxial pressing for the fabrication of translucent yttria ceramics
- 2008
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Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 43:8, s. 2849-2856
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Tidskriftsartikel (refereegranskat)abstract
- Slip casting and uniaxial pressing were compared as first consolidation stages prior to cold isostatic pressing (CIP) to produce translucent yttria ceramics. In the first step, yttria slurries suitable for slip casting were prepared. The viscosity was optimized with respect to the starting agglomeration state, amount of dispersant, milling time, and number of milling balls. Secondly, pellets were prepared either by slip casting or uniaxial pressing and then cold-isostatically pressed. Finally, the pellets were made translucent by a combination of pre-sintering and hot isostatic pressing (HIP). Although slip-cast and pressed samples exhibited similar green-body densities after CIP and pre-sintering, the samples prepared by slip casting were more homogeneous in terms of translucency and microstructure throughout their bodies. This was attributed to the ability of slip casting to minimize density gradients during packing, and to the beneficial effect of ball-milling to remove larger agglomerates before casting. Therefore, slip casting as a first consolidation stage prior to CIP appears to be more suitable than uniaxial pressing in order to prepare homogeneous optical ceramics.
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