| 1. |
- Alnegren, Patrik, 1988, et al.
(författare)
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Inhibiting chromium evaporation and oxide scale growth on SOFC metallic interconnects by nano coatings
- 2014
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Ingår i: 20th World Hydrogen Energy Conference, WHEC 2014. - 9780000000002 ; 1:2014
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Konferensbidrag (refereegranskat)abstract
- High chromium ferritic steel is today the most commonly considered material for SOFC interconnectors due to many desirable properties, such as matching thermal expansion coefficient with other cell components but most importantly better machinability and price compared to ceramic alternatives. Yet there are some obstacles that need to be addressed before long term stability of a ferritic steel interconnector based fuel cell stack can be realized. First of all the electrical conductivity needs to remain high throughout the fuel cell stack operating life time and thus the formed oxide layers need to be electrically conductive and thin. Secondly, volatilization of chromium from the oxide scale of metallic interconnects causes rapid degradation due cathode poisoning. In the current study both oxidation and chromium evaporation of ferritic steel substrates are investigated in controlled atmospheres that simulates the environments of an operating SOFC stack. Samples coated with nanometer scale dual coatings of Co and Ce were tested. The dual coating substantially increased the performance of the ferritic substrates by i) significantly reducing oxidation rate, ii) increasing scale adherence and iii) diminishing chromium evaporation by 90 % via the formation of a Co-Mn-spinel cap layer.
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| 2. |
- Bachinger, Angelika, et al.
(författare)
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Stiffness-modifiable composite for pedestrian protection
- 2014
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Ingår i: 16th European Conference on Composite Materials, ECCM 2014. - : European Conference on Composite Materials, ECCM. - 9780000000002
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Konferensbidrag (refereegranskat)abstract
- A novel functional material allowing stiffness-reduction upon external stimulation was developed. Implementation of such technology in the design of a car front has high potential to result in increased protection of vulnerable road users (VRUs). The composite material is obtained by coating carbon fibres with a thermoplastic polymer in a continuous process, followed by infusion with an epoxy resin. The process is scalable for industrial use. The coating process was optimized regarding coating efficiency, energy consumption, risks involved for operating personnel and environment, and tailored to gain the optimal coating thickness obtained from numerical calculations. A drastic decrease in transversal stiffness could be detected for the composite material by dynamic mechanical thermal analysis (DMTA), when the temperature was increased above the glass transition temperature of the thermoplastic interphase. The ability of the material to achieve such temperature and associated reduction in stiffness by the application of current was verified using a special 3-point bending setup developed for this task.
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| 3. |
- Brynjell-Rahkola, Mattias, 1986-, et al.
(författare)
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Modal analysis of roughness-induced crossflow vortices in a Falkner-Skan-Cooke boundary layer
- 2013
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Ingår i: International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2013. - : TSFP-8. - 9780000000002
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Konferensbidrag (refereegranskat)abstract
- A three-dimensional global stability analysis using high-order direct numerical simulations is performed to investigate the effect of surface roughness with Reynolds number (based on roughness height) Rek above and below the critical value for transition, on the eigenmodes of a Falkner-Skan-Cooke boundary layer. The surface roughness is introduced with the immersed boundary method and the eigenvalues and eigenfunctions are solved using an iterative time-stepper method. The study reveals a global instability for the case with higher Reynolds number that causes the flow in the non-linear simulations to break down to turbulence shortly downstream of the roughness. Examination of the unstable linear global modes show that these are the same modes that are observed in experiments immediately before breakdown due to secondary instability, which emphasizes the importance of these modes in transition.
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| 4. |
- Cataldi, A., et al.
(författare)
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Polymer composite with micro- and nanocellulose for artwork protection and restoration
- 2014
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Ingår i: 16th European Conference on Composite Materials, ECCM 2014. - 9780000000002
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Konferensbidrag (refereegranskat)abstract
- Micro- and nanocomposites were prepared using Aquazol® 500 as a polymeric matrix and a microcrystalline cellulose (MCC), and suspensions of cellulose nanocrystals (CNC), as reinforcing agents. After a preliminary thermo-mechanical characterization that highlighted a stabilizing effect due to the micro- and nanofiller introduction, with an increase of the elastic modulus and a decrease of the thermal expansion coefficient and the creep compliance [1], these materials were applied as canvas lining adhesives. Single-lap shear tests both in quasi-static and creep conditions confirmed the dimensional stability provided by cellulose micro- and nanoparticles, with an important reduction of the adhesives compliance proportional to the filler content. Interestingly, MCC and CNC introduction did not impair the fracture behavior of the neat matrix.
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| 5. |
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| 6. |
- Davidson, Lars, 1957
(författare)
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Backscatter from a scale-similarity model: embedded LES of channel flow, developing boundary layer flow and backstep flow
- 2013
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Ingår i: 8th International Symposium on turbulence and shear flow phenomena (TSFP8). - 9780000000002 ; 3
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Konferensbidrag (refereegranskat)abstract
- The scale-similarity model was proposed by Bardina et al. (1980) some 30 years ago. It was found not to be sufficiently dissipative. Much later, Davidson (2009) found a way to make it strictly dissipative. This was simply achieved by selecting those instants when the scale-similarity term in the momentum equation has the same sign as the viscous diffusive term (the latter term is indeed dissipative). In Davidson (2009) this technique was also used the other way around: by selecting time instants when the scale-similarity term has the opposite sign to the viscous diffusion term it acts as a backscatter term, which destabilizes the momentum equation. This feature is exploited in the present work to promote the generation of resolved turbulence. It is used to promote the creation of resolved turbulence in embedded LES of channel flow, and LES of developing boundary layer and backstep flow. The present method reduces the gray area problem described by Spalart (2009). The proposedmethod can also be used to promote transition from laminar to turbulent flow.
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| 7. |
- Fernberg, Patrik, et al.
(författare)
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Processing and properties of new polyimide composites with high temperature ability
- 2014
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Ingår i: 16th European Conference on Composite Materials, ECCM 2014. - : European Conference on Composite Materials, ECCM. - 9780000000002
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Konferensbidrag (refereegranskat)abstract
- The communication present results from work on development and evaluation of new polymeric carbon fiber composites with extreme temperature performance: Tg up to 360°C is targeted. The anticipated use of such composites is found in aeroengine-applications. In the work we are exploring a new and tailored phenyl ethynyl terminated imide (PETI) formulation, specially developed for the program. The formulation utilizes crosslinkers of the Nexamide" type (from Nexam Chemical AB, Sweden). The resins are initially evaluated from a processing and property perspective. Both DSC-measurements and rheology characterization are utilized in the development. Suitable RTM-processing schemes are investigated from a viscosity point of view. The schemes are used in the composite sample manufacturing. Besides a processing perspective the study also present the first results on physical behavior of the polymers and their composites.
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| 8. |
- Ferritsius, Olof, et al.
(författare)
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Bat of CTMP and TMP plants with respect to quality development and energy efficiency
- 2014
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Ingår i: International Mechanical Pulping Conference, IMPC 2014, part of PulPaper 2014 Conference. - : PI.
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Konferensbidrag (refereegranskat)abstract
- Sixteen TMP/CTMP lines aimed for publication and board grades have been compared for energy efficiency with respect to pulp quality development. The pulp property profile and the process design differed substantially, even for similar product grades. A given level of a specific pulp property was reached over a wide range in specific energy. The most energy efficient lines operated at the highest production rates and with high relative speed of the refiner discs. With respect to the final pulp quality there was no obvious influence of how the screen room was equipped. It was possible to develop the fibers in a proper way just by refining of the whole pulp stream.
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| 9. |
- Ferritsius, Rita, et al.
(författare)
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LC-refining of mechanical pulps and its influence on fiber curl and handsheet strength properties
- 2014
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Ingår i: International Mechanical Pulping Conference, IMPC 2014. - 9780000000002
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Konferensbidrag (refereegranskat)abstract
- The effect on fiber and sheet properties has been compared for two different low consistency (LC) refiners in two TMP mills. One of the LC-refiners (CF 82) was running as second stage in the main line and the other (TF58) was running as second stage in the reject line. The development of fiber and strength properties was very similar for the two cases. Both disintegration in the laboratory and LC- refining decreased the fiber curl and increased the tensile index in a similar way. The effects of disintegration and LC-refining were additive.
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| 10. |
- Ferritsius, Rita, et al.
(författare)
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On energy efficiency in chip refining
- 2014
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Ingår i: International Mechanical Pulping Conference, IMPC 2014. - : Paper Engineers' Association (PI). - 9780000000002
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Konferensbidrag (refereegranskat)abstract
- The quality of TMP has been investigated for a CD82 chip refiner both with respect to normal variations and as a result of step changes of production rate, dilution water feed rates and plate gaps. A given level of tensile index was reached over a wide range in specific energy input. The energy efficiency with respect to tensile index decreased if the pulp consistency in the blow line exceeded 55 %. The extended entropy model applied on the refiner showed that the calculated pulp consistency after the flat zone could be extremely high, leading to lower energy efficiency. This was not possible to detect by the measured values for the pulp consistency in the blow line. The short time variations in tensile index correlated more strongly with the model based total residence time in the two refining zones than with the motor load.
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