Research reports

Reports within the materials research area

Grants are given to research projects investigating the structure of materials, introduction of new materials in industrial production, weir and tear. Reports may cover subjects, such as

  • Metallic materials
  • Biomaterials
  • Building materials
  • Polymers
  • Nanomaterials

A modular high performance metal ion source for surface and materials technology

A novel type of metal ion source based on gasless sputtering has been design. It will uniquely combine pure, high metal ion currents with equipment portability and can therefore be used in combination with other processes on many different machines. This way metal ion processing for sputtering, subplantation, and surface texturing is facilitated also for existing conventional laboraty thin film equipment. The most attractive design, considering performance and features versus cost and safety, is a three-grid 10kV acceleration unit mounted on a Conflat 160 flange. Peak current for singly charged ions would be up to 10A and an implantation depth in excess of 10 nm is possible. Such units could be useful in many settings, some examples being to make low-defect metal coatings for high tempterature stability conductors and quantum computers, highly ordered superconducting materials and to make implantations to mitigate bacterial growth on medical implants. Due to its modular and very flexible design approach it is also a very interesting pedagogic tool for accelerators as well as surface technology. The mechanical design was made by Carl-Johan Englund, the electronic parts by Petter Larsson, and the project was coordinated by Joakim Andersson with great help and inspiration from Ian Brown.

Date
2016-07
Author

Uppsala Universitet, Ångströmslaboratoriet; Joakim Andersson
Lawrence Berkeley National Laboratory, Berkeley; Ian Brown
Englund Engineering; Carl-Johan Englund
Ionautics AB; Petter Larsson

Using resource based slicing to capture the intermittency of variable renewables

As the share of variable renewables - wind and solar PV - is expected to grow significantly in coming decades, it has become increasingly important to account for their intermittency in large scale energy models that are used to explore long term energy futures. In this paper we propose and evaluate one method for doing so, namely, resource based slicing. In addition we implement storage based on possible transitions between slices which allows us to expore new dynamics between intermittent generation and electricity storage in large scale models. Our preliminary results show that this approach manages to capture many aspects introduced by variable renewables such as need for flexible generation capacity and curtailment at high penetration levels. We show that adding electricity storage to the system will favour solar power but has only a minor effect on wind and nuclear power.

Date
2016-07
Author

Chalmers; Mariliis Lehtveer, Niclas Mattsson, Fredrik Hedenus, Martin Soini

Surface passivation of SiC for reduced surface recombination in LED and solar cell applications

Alkali metals (Li, Na, K and Cs) have been studied as possible candidates for passivation of surface and interfaces between dielectric materials and silicon carbide (SiC). The main emphases have been on diffusion of alkali metals in SiC. Further, the mobility of alkali metals at interfaces between dielectrics/SiO2 and SiC has been investigated.

The result of the project gives insight in the limitations for the usefulness of alkali metals in combination with SiC. The alkali metals are more mobile than expected in SiC. As the mass increases from lithium to cesium the diffusivity decreases, as expected. Among the alkali metals it is only cesium that shows negligible diffusion at typical device provess temperatures. If only the mobility in SiC is of concern, cesium is the best candidate. However, a high mobility of cesium in SiO2 indicates that it may be necessary to avoid all alkali metals if SiO2 are used as dielectric material.

Additional, Al2O3 has been used as an alternatibe dielectric for SiO2. Life time measurements have been performed indicating that the surface preparation may be as important as the choice of dielectric material for isolation.

This project is a first attempt and further effort on the passivation issue is needed.

Date
2016-06
Author

KTH; Margareta Linnarsson

Spray deposition of new environmental friendly, highly efficient and low-cost building integrated solar cells for increased solar

The project is about developing new materials and a new method for production of solar cells for building integration and the project also contains simulations of the energy production from solar cells integrated in the roof and walls in a building. The project started 2014 and has been very successful. The new solar cell production method by a new spray deposition system, has been constructed and verified to work very well and has been further developed during 2015. For lead pervoskite solar cells with an electron transport layer prepared by spraying, we have achieved over 15% power conversion efficiency during autumn 2015, which is a very high efficiency for a perovskite solar cell prepared in air, without protective atmosphere. We have during 2015 discovered a new more environmental friendly perovskite based on bismuth (Bi) instead of environmental friendly (lead free) perovskite working in the solar cell. Using this new bismuth-pervoskite, Cs3Bi2l9, we have also developed the spray technique and we are currently investigating the growth of the bismuth perovskite in a controlled way by heating the substrate at a specific temperature at the same time as spraying the liquid. We are now optimizing the material and spraying parameters to obtain an efficient solar cell. From the collaboration with ÅF we have also simulated the use of building integrated solar cells and compared solar cells on roof and on walls and the results show that integration of solar cells in walls will be specifically important to cover demand on electricity during winter, mornings and evenings without large seasonal storage systems. Especially the results show that solar cells integrated in walls gives higher electricity production in the mid-winter compared to rooftop solar cells, which is very important for a balanced energy system. We have also integrating the new perovskite solar cells in this simulation model, which we will use to study the advantages and drawbacks with the perovskite solar cells comparated to the silicon based solar cells in building applications. We have compared the energy usage in a real office building with the solar electricity from a simulation model, where we have integrated perovskite solar cells in the building facade and roof. The results show that the solar energy produced from the solar cells at different times during the day matches the energy usage very well during summer, spring and autumn. The collaboration between the research group and ÅF has been very fruitful. The discussions about both the applied solar cell installations, simulations and the solar cells on a research level have given insight in possible new future directions of development of both research and applications.

Date
2016-05
Author

Uppsala Universitet; Erik Johansson

Standards for optimizing corrugated board packaging for exporting industry

For the globally active brand owner companies there are many problems and shortcomings associated with corrugated board boxes. One reason for this situation is the lack of uniform performance standards and guidelines. The feasibility study aimed at giving directions for future development of test methods and guidelines for currugated board packaging that are based on the real needs of the exporting industry. The project consisted of mapping of demands, mapping of existing test methods, and case studies as well as analysis of gaps and needs.

Some areas found to be lacking and in need of further development were effects of vibrations and shocks on stacking strength, effects of design (e.g. perforations), and effects of creep and varying climate. Future work should aim at providing standards and especially guidelines on how to use standards and specifications. Different guidelines for generalists and specialists should be considered. The generalist would need checklists and instructions on what a minimum specification should include. The specialist would need more technical guidelines on effects of e.g. water, humidity and creep, and on how properties of papers, board and boxes could be translated to package.

Date
2016-03
Author

Thomas Frost, Johan Alfthan; Innventia

nkjet printing of detectors for infrared light

The goal of the project was to investigate the use of ink-jet printing technology to manufacture thermal infra-red detectors. With very low cost detectors new application areas could open up, such as integrating detectors directly on packages and similar.

In the project, the polymer SU-8 was successfully ink-jet printed on plastic and Silicon substrates, showing that it should be possible to use ink-jet technology to manufacture thermally insulating membranes.

In the project, bolometer structures were successfully printed using nano particle silver ink. However, the temperature coefficient, the change in resistance with temperature, was determined to not be high enough. Especially for low cost applications the thermally isolated substrate that is needed would much likely also have lower performance to cut costs. Therefore the conductive polymer PEDOT:PSS was instead evaluated. It was shown that the resistance as well as the polymer PEDOT:PSS was instead evaluated. It was shown that the resistance as well as the temperature coefficient of PEDOT:PSS could be increased by using photo paper as substrate instead of plastic. This was attributed to salts in the paper coating. It is previously known that reducing PEDOT:PSS will lead to higher resistivity. It was also shown that the temperature coefficient could be further increased by coating the paper with a NaC1 solution before printing the PEDOT:PSS bolometers. The highest temperature coefficient achieved for PEDOT:PSS was -0.013 on NaC1 coated paper. For the silver nano particle ink bolometers the highest value was 0.0009.

The printed polymer membrane and PEDOT:PSS structure show that it is feasible to manufacture deteectors with ink-jet technology, although more development is needed.

Date
2016-02
Author

Henrik Andersson, Mittuniversitetet

Development of Graphene-based nuclear fuel cladding for improved safety

The project concern a development of multilayer SiC-graphene composite material for application in reactors' nuclerar fuel cladding in order to improve its safety and performance.

Date
2016-01
Author

V Dykin, D Jang, C Lau, H Nylén and M Thuvander, Chalmers

Modification of float glass surfaces by novel oxy-nitride thin films

Glass is indispensable and innovative material that has plenty of applications. It is an essential component of numerous products that we use every day, most often without noticing it. Glass is widely used in a variety of applications e.g. housing and buildings, automotive and transport, containers, drinking vessels, displays, insulation and optical fibers due to its universal forming ability, transparency, chemical durability, form stability, hardness relatively low price and possibility of recycling. Flat glass is a widemarket of the glass industry and generally ninety percent of all tlat glass produced worldwide is manufactured using the float forming process. There is a large market strive for thinner and stronger glass in order to reduce costs, save energy, and to find new applications.

This study comprises the modification of flat/float glass surface by novel oxynitride thin films in the Mg-Si-O-N and Ca-Si-N systems prepared by RF magnetron sputtering technique. The aim of this work is to develop a novel process in order to improve the mechanical and optical properties of flat/float glass by deposition of external materials e.g. alkaline earth metals and nitrogen to the surface in a process with the obvious potential to be automatic in industrial processes. Both mechanical and optical properties of the glass surface have been improved by the deposition of thin films. The float glass surface modified with Mg-Si-O-N have high value of hardness of 20 GPa, elastic modulus of 175 GPa and refractive index value of 1.96 compare to the float glass having hardness of 7 GPa, elastic modulus of 72GPa and refractive index of 1.50. The method presented here is anticipated to be used in production in the future and would make it possible to produce larger quantities of strong flat glass for smartphone, tablet covers and display technology to a considerably lower cost.

Date
2016-01
Author

Sharafat Ali and Bo Jonsson, Linnaeus University

Per Eklund and Jens Birch, Linköping University

Characterisation of surface deposits and corrosion layers of thermal power plant materials by glow discharge optical emission spectroscopy (GD-OES)

The internal surfaces of thermal power plants become covered withg deposits from the combusted material (fuel) as well as a gradual build-up of various corrosion products. The formed layers are highly complex in composition and structrue, varying depending on the alloy, temperature, type of fuel, etc. The elements present in the deposited layers affect the corrosion processes and thereby the service lifetime of the boilers. In order to better understand these corrosion processes, compositional depth profiling (CDP) of the layers is very valuable analytical information. A radio frequency (RF) Glow Discharge Optical Emission Spectroscopy (GD-OES) method has been developed for quantitative depth profile analysis of these surface deposits.

Some of the major elements of interest are CI, S, Ca, Na and K, and there are no commercially available solid reference materials (RM) with mass fractions in the range found in these materials. It was therefore necessary to produce dedicated RM's for calibration. The method devised within the project was to spray salt solutions onto steel substrates and subsequently dry these, producing coating of well-known composition for calibration. The average thicknesses (or rather coating weigh/are) of the coatings were determined by weighing the samples before and after deposition. This method was shown to work satisfactory.

A comparison with SEM cross section images have also shown that the in-depth structure of the depth profiles qualitatively agree well with the observed structure in the images. However, the analytical wok has also shown that some of these types of materials are "difficult" to analyse by GD-OES, in the sense that the plasma discharge tends to be unstable. It should therefore be noted that not all materials of this type will be amenable to GD-OES analysis.

Comparing some field exposures of 16Mo3 and 310S it has been shown that differences in corrosion mechanisms can be deteced with the GD-OES method. By observing the positions in the depth profile of primarily K and CI, the ability of a material to withstand corrosion can be deduced.

The GD-OES method developed is a valuable analytical tool in continued research on the corrosion properties of thermal power plants, as wlll as th chemical processes responsible for this corrosion.

Date
2016-01
Author

Annika Talus, Arne Bengtson, Mats Randelius and Rikard Norling at Swerea KIMAB

New method for evaluating wear resistance of coating systems intended for use on concrete parking decks

I collaboration with SwereaKIMAB, manufacturers/contractors and building owners, the Swedish Cement and Concrete Research Institute is conduting an SBUF project concerning parking decks. The purpose of the project is to develop a basis for how a parking deck should be designed with regard to floor coverings on concrete. The resistance to studded tires is here of great importance. This report focuses on relevant methodology for simulating the kind of studded tire traffic that occurs on parking decks in Nordic countries.

Field test application of nine different coating systems has been carried out on a garage concrete fllor in Kville, Gotheburg. Test slabs have been applied in connection with the work in site, for testing ear resistance in the laboratory. Laboratory tests are conducted for all systems according to three different methods, and evaluated. The focus of this resport is on the development and modification of methodology based on prEN 12697-50 (Resistance to scuffing). Laboratory testing was carried out at ISAB Institute in Aachen, with the coating system applied to concrete slabs.

Results so far show that the method is promising for testing the wear resistance of coating systems intended for use on concrete parking decks, and differentiates well between products.

Date
2015-12-14
Author

CBI Betonginstitutet; Ylva Edwards

Chemical strengthening of flat glass by vapour deposition and in-line alkali metal ion exchange

Glass is a common material in the everyday life. It is widely used in a variety of applications e.g. architetural, automotive, containers, drinking vessels, displays, insulation and optical fibers due to its universal forming ability, transparency, chemical durability, form stability, hardness and relatively low price. flat glass is a wide market of the glass industry and generally ninety percent of all flat glass produced worldwide is manufactured using the float forming process. There is a large market strive for thinner and stronger glass in order to reduce costs, save energy, reduce environmental footprint, find new applications and to improve the working environment for labour working with mounting flat glass.

This study comprises the modification of flat/float glass surface by a novel route; exchange of ionic species originating from in-line vapour deposition of salt compared to the conventional route of immersing the glass in molten salt baths. The aim of this work is to develop a novel process in order to improve the mechanical strength of flat/float glass by introducing external material to the surface in a process with the obvious potential to be automatic in industrial processes. Chemical strengthening has been performed by applying potassium chloride to the glass surface by vapour deposition and thermally activated in exchange. The method presented here is anticipated to be used in production in the future and would make it possible to produce larger quantities of chemically strenghtened flat glass to a considerably lower ost.

 

Date
2015-12-14
Author

Glafo AB; Stefan Karlsson

Ink - jet printing of detectors for infrared light

The goal of the project was to investigate the use of ink-jet printing technology to manfacture thermal infra-red detectors. With very low cost detectors new application areas could open up, such as integrating detectors directly on packages and similar.

In the project, the polymer SU-8 was successfully ink-jet printed on plastic and Silicon substrates, showing that it would, be possible to use ink-jhet technology to manufacture thermally insulating membranes.

In the project, bolometer structures were successfully printed using nano particle silver ink. However, the temperatur coefficient, the change in resistance with temperature, was determinhed to not be high enoguh. Especially for low cost applications the thermally isolated substrate that is needed would much likely also have lower performance to cut cost. There the conductive polymer PEDOT:PSS was instead evaluated. It was shown that the resistance as well as the temperature coefficient of PEDOT:PSS could be increased by using photo paper as substrate instead of plastic. This was attributed to salts in the paper coating. It is previously known that reducing PEDOT:PSS willl lead to higher resistivity. It was also shown that the temperature coefficient could be further increased by coating the paper with a NaCl solution before printing the PEDOT:PSS bolometers. The highest temperature coefficient achieved for PEDOT:PSS was -0.013 on NaCl coated paper. For the silver nano particle ink bolometers the highest values was 0.00009.

The printed polymer membrane and PEDOT:PSS structure show that is is feasible to manufacture detectors with ink-jet technology, although more development is needed.

Date
2015-12-11
Author

Mittuniversitetet; Henrik Andersson

The plasma processing and treatment of the internal surfaces

The project has shown that:

  • High-quality DLC films can be deposited inside tubular substrates by the hollow cathode plasma assisted CVD
  • Athmospheric plasma is not as well suited for this purpose as the plasma at reduced gas pressure of the order of 0.1 Torr. The atmospheric plasma in air can be used rather for pre-cleaning and activation of substrate surfaces, as it was fund in the previous project
  • Graphite is a suitable material for hollow cathodes to avoid unwanted contamination of the DLC films
  • For deposition of high quality films a surprisingly low content of acetylene (≤ 1%) in argon is required
  • A high power may cause an arc discharge in the hollow-cathode, accompanied by the formation of microparticles of carbon in the film, which is undesirable for some applications. Microparticles are concentrated in the center of the plasma jet plume. Therefore the films deposited on the substrates inside the tubular holder are more "clean" from these particles that the films deposited on the substrate facing the hollow-cathode jet
  • The film deposition rate at given expertimental conditions was about 10 0nm/min. It is realistic to increase this rate up to at least 10 times.

 

Date
2015-12-11
Author

Uppsala Universitet; Ladislav Bardos

Y-In-N thin films for optoelectronic and electroacoustic applications

The project resulted in successful synthesis and investigation of novel material Y-In-N (both experimental and theoretical), the knowledge obtained about the growth process and material properties will lead to new projects in the fututre. YxIn1-xN with x=0.00, 0.09, 0.15, 0.24, 0.28, 0.40, 0.53, 0.69, and 1.00 were preparated to cover full compositional range. In-plane and out-of-plane lattice parameters were measured and compared with the calculations, and the match is very good. This confirms the formation of solid solution. By introducting low amounts of Y, the stability of the parasitic zinc blende phase is decreasing faster than for desired wurtzite crystal structure. We confirmed this experimentally; with up to 15% yttrium, the zinc blende phase is no longer detected using X-ray diffraction and crystal quality of the material improves tremendously. At higher concentrations, however, the crystalline structure of the material becomes more disordered, as expected from the theoretical predictions. Piezoelectric properties of this material were calculated as well, and we sww that both piezoelectric coefficients e33 and d33 is increasing more than 400%, and is comparable to recently published data on better investigated Sc-A1-N. The collection of measurement data have led to publication of a scientific paper in 2015.

Date
2015-12
Author

Agne Zukauskaite, Institutetet för fysik, kemi och biologi (IFM) vid Linkiöpings Universittet

"Lyssna och titta" eller auralisera och visualisera

Med dagens tempo och informationslöde måste kunden snabbt förstå och kunna ta beslut i projekteringsfrågor. Det innebär att dagens konsulter måste vara mer snabbfotade och samtidigt kunna leverera attraktiva och lättbegripliga produkter/tjänster. Inom arkitektur har VR-tekniken revolutionerat presentationsmöjligheterna, dessa gör att beställare direkt förstår hur miljön kommer att se ut och medför en större möjligheter att påverka t.ex. sin blivande arbetsplats. Auraliseringar, d.v.s. datorsimulering av ljudmiljöer, har länge funnits tillgängliga inom akustikvärden. Problemet är att de programvaror som erbjuder dessa möjliheter inte har kunna erbjuda ett visuellt attraktivt resultat, dessutom krävs programvaran vid uppspelning vilket kraftigt begränsar dessa potentionella användning. Med den nya teniken kan man erbjuda auraliseringar av den blivande ljudmiljön i samma gränssnitt som högupplösta 3D-modeller i ett gränssnitt som enklare och bättre kan hjälpa kunden.

Date
2012-12
Author

ÅF-Infrastructure; DAniel Lindforss, Klas Hagberg

Meso mechanical study of new resource optimal concrete material

This project focuses on detailed studies of how the cracking process in concrete is influenced by the concrete micro- and mesostructure. The aim is to increase knowledge of how critical parameters affect the cracking process and how this is related to the material's macroscopic properties. During this project a methodology based on the combination of different experimental methods and measuring techniques at different scale levels has been developed. Crack propagation during tensile loading of small-scale specimens in a tensile stage was monitored by means of Digital Image Correlation and Acoustic Emission. After the tets, crack patterns were studied using fluorescence microscopy. As a comparison the cracking process in direct tensile tests at the macro scale was also studied.

The crack characteristics identified by DIC, AE and microscopy show clear similarities in the cracking process at meso level between the direct tensile tests and the tensile stage tests. This suggests that the cracking process observed at meso scale in the tensile stage testing is representative of the cracking process in the larger specimens.

The test series in the present project included four different concrete recieps. The concretes had a w/c of about 0.38 or 0.9 and fine aggregate (< 8 mm) of natural or crushed felsic rock material. The analysis of fracture in tension show that there are more secondary fractures branching out from the primary fracture with crushed aggregate. There are, however, more diagonal fractures in samples with natural aggregates. It can be seen that propagating secondary craks often stop or are with crushed aggregate. As the diagonal secondary fractures have partly grown in shear, flaky particles may act through interlocking.

Date
2011-12
Author

SP Technical Research Institute of Sweden; Mathias Flansbjer

Development of hybrid light emitting

III-nitride-based hybrid heterostructures for light emitting diodes (LED) combine advantages of epitaxially grown semiconductor quantum wells (QW) with inexpensive polymers or colloidal nanoparticles having efficient fluorescence in the visible region. Such hybrid LED are promising for fabrication of low-cost and highly efficient microlight sources that can be used in full-color displays, imaging systems, miniature chemical and biological sensors. The light is down converted in the typical organic/inorganic GaN-based LED hybrids from UV emission to visble via common radiative energy transfer. The aim of the project was to develop a novel class of hybrid structures utilizing a non-radiative (Förster) resonant energy transfer (NRET) from excitation generated in inorganic QWs to excitons in organic films. According to theoretical predictions such hybrids might be considerably more efficient compared to their radiative analogues. Within the project several hybrid structures have been fabricated and studied. Both green polyfluorene and colloidal ZnO nanocrystals have been used for deposition as a fluorescent film on the top of AIGaN/GaN QW structures. The top layer AIGaN thickness has to be less than 4 nm to allow a dipole-dipole interaction and, thus, an efficient pumping energy transfer even at room temperatures.

Date
2011-12
Author

Linköpings Universitet; Galia Pozina

Plasma processing and treatment of inner furfaces

The goal of this project was to develop plasma reactive processes at substrate temperatures below 800 ° C for processing and treatment of internal substrate surfaces and pipes with lengths up to 500 mm and a diameter of between 20 mm and 5 mm. It was proven that the active plasma can be generated inside the narrow pipes and holes. Suitable plasma source for such purposes utilizes the principle of so-called hollow cathode. The active plasma generated inside both hollow substrate using patented plasma sources developed at Uppsala University. The plasma processing inside the tubes was possible at both the reduced gas pressure and at atmospheric and higher pressure. Obtained results and experiences will be used in the extension phase of the project for the further development of insulating coatings based on diamond-like carbon (DLC), in particular to protect the surfaces of the high-voltage components.

 

Date
2011-12
Author

Uppsala Universitet; Ladislav Bardos

Status Assessment of relining or lined sewage pipes in apartment buildings

Over the last decades, relining of pipes in buildings has become an alternative to the traditional pipe replacement. Relining is less expensive, less time consuming and causes less disturbance for the residents, compared to pipe replacement. However, questions have been raised whether or not relining is a reliable method, and if the long term performance is good enough to motivate the method. Also, the health and environmental effects have been discussed.

The first part of this report is a summary of the current status of relining in Sweden. Secondly, experimental work has been performed in order to assess the status of relined pipes, which have been in service for up to 12 years. Typical failures are described and the mechanical performance is investigated.

Finally, laboratory exposures were conducted to assess the two materials performance under hars conditions; to predict service reliability and to correlate to the field test. The study shows that the materials maintain their mechnical properties when exposed up to 60 degreees, and that degradation is taking place when the material is exposed to water at 80 degrees. During relining, it is import to assure that the material thickness is sufficient and that curing is complete.

In summary, we consider relining to be an alternative for property maintenance, whith respect to mechanical properties.

Date
2011-12
Author

SwereaKIMAB; Petter Bergsjö

Optimized design of cast components - Influence from defects on strenght of aluminium castings

The aim of the project has been to investigate the influence from defects on cast aluminium components strength with photogrammetric methods. The project has partly been focused on how heat treatment and chemical treatment affects the strength and how defects can be avoided at the design stage for defect-free (minimized defect) goods. In the design optimization process casting simulation software has been used and part of the project has been focused on finding suitable physical parameters for the plaster mould cast method used at Hackås Precision Foundry.

It is well-known that the defects have a detrimental effect on the strenght of a cast component but not widely documented how this negative impact "looks*". In this project in situ measurement during tensile tests has demonstrated how strain concentrations around different types of defects occur.

The project also aimed to increase foundrymen and casting designers understanding of how various defects influende the product's strength and urability in operation and how defects can be avoided by optimizing the casting deisgn in the design phase.

Date
2011-12
Author

Hackås Precisionsgjuteri; Peter Vomacka

Determining the ultimate limit of optical fiber Bragg gratings at elevated temperatures

Optical fiber sensors are attractive due to the small size of the optical fiber enabling embedding of the sensor with minimal influence on the external parameter to be measured. In addition optical fiber sensors enable optical readout (fast), multiplexing capabilities as well as being immune to electromagnetic interference and noise. Fiber Bragg gratings (FBGs) are wavelength specifics filters, fabricated in optical fibers by exposure to intense ultraviolet (UV) light. By exposing the fiber using an interferometric setup a periodic refractive index perturbation can be created. Light in the fiber having a wavelength twice that of the refractive index modulation period, mulltiplied by the average refractive index of the glass, will resonantly interact with the structure, resulting in strong back reflection, i.e., Bragg reflection. This project targets optical fiber sensors and FBGs  for high-temperatur applications regarding their ultimate limit of stability. To better understand the underlying mechanisms that govern the stability, and ultimately their reliability, a system for material studies has been enabling various experiments to be performed on optical fibers at elevated temperature. The central part of the project has been the development of a CO2-laser based furnace resulting in minimal thermal gradients along the heated fiber. Beam shaping to provide a top-hap profile has been the main approach for heating, inclulding muiltiple-beam exposure. Preliminary results show a significant improvement in comparison with traditional resistance furnaces, providing more possibilites and a much higher degree of control of experimental parameters.

Date
2010-12
Author

KTH; Michael Fokine, Patrik Holmberg

MAX-batteri, phase 2

The development of new environmentally friendly power sources has been under consideration all over the world. One such technological direction has been the research around hybrid vehicles batteries, which also might lead to new starter batteries.

The 1996 invention of a new class of ceramics; The Mn+1AXn (MAX) phases; where M stands for an early transition metal, A for the A-group (usually IIA and IVA) and X which is either nitrogen or carbon - seems to posses many characteristics useful in that or possibly other battery applications. At KTH the old dream of the bipolar lead-acid battery has been connected to this new material.

However, the formation of an irreversible deactivating protecting film on the surface of one such studied specimen: titanium silicon carbide when used as positive electrode, and also the low hydrogen over potential on the negative electrode made the project two steps further from realization. The two first project stages reported here dealt successfully with these obstacles which clearly showed that the new material can be used as a conductive and electrochemically stable partition in the lead-acid environment.

The remaining work to be done has to prove the expected durability of a practical battery with the new material as well as finding ways to minimize the wall thicknesses in order to lower material costs in this new battery type.

Date
2008-04-14
Author

Christopher Sylwan

Bipolar lead-acid battery

The development of new environmentally friendly power sources has been under consideration all over the world. One such technological direction has been the research around hybrid vehicles batteries, which also might lead to new starter batteries. The 1996 invention of a new class of ceramics; The Mn+1AXn (MAX) phases; where M stands for an early transition metal, A for the A-group (usually IIA and IVA) and X which is either nitrogen or carbon - seems to posses many characteristics useful in that or possibly other battery applications. At KTH the old dream of the bipolar lead-acid battery has been connected to this new material. However, the formation of an irreversible deactivating protecting film on the surface of one such studied specimen: titanium silicon carbide when used as positive electrode, and also the low hydrogen over potential on the negative electrode made the project two steps further from realization. The two first project stages reported here dealt successfully with these obstacles which clearly showed that the new material can be used as a conductive and electrochemically stable partition in the lead-acid environment. The remaining work to be done has to prove the expected durability of a practical battery with the new material as well as finding ways to minimize the wall thicknesses in order to lower material costs in this new battery type.

Date
2006-03
Author

Tor Eriksson
Sebastian Reichardt
Christopher Sylwan