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  • 1.
    Adamopoulos, Stergios
    TEI Thessaly, Greece.
    Recovery and utilization of wood and rubber at the end of their lifespan to produce innovative products2014In: Development and Business Prospects in Thessaly by Symbiotic Utilization of Agricultural and Industrial Solid Waste to Produce Materials and Energy, November 24, Larissa, Greece, 2014Conference paper (Other academic)
  • 2.
    Addassi, Mouadh
    et al.
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Wadsö, Lars
    Lund University.
    Inverse analyses of effective diffusion parameters relevant for a two-phase moisture model of cementitious materials2018In: Cement and Concrete Research, ISSN 0008-8846, E-ISSN 1873-3948, Vol. 106, p. 117-129Article in journal (Refereed)
    Abstract [en]

    Here we present an inverse analyses approach to determining the two-phase moisture transport properties re-levant to concrete durability modeling. The purposed moisture transport model was based on a continuumapproach with two truly separate equations for the liquid and gas phase being connected by the sorption ki-netics. The moisture properties of ten binder-systems containingfly ash, calcined clay, burnt shale and graymicro-filler, were investigated experimentally. The experiments used were, (i) sorption test (moisturefixation),(ii) cup test in two different relative humidity intervals, (iii) drying test, and, (iv) capillary suction test. Masschange over time, as obtained from the drying test, the two different cup test intervals and the capillary suctiontest, was used to obtain the effective diffusion parameters using the proposed inverse analyses approach. Themoisture properties obtained with the proposed inverse analyses method provide a good description of the testperiod for the ten different binder-systems.

  • 3.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Hansson, Lars
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Distribution of preservatives in thermally modified Scots pine and Norway spruce sapwood2013In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 47, no 3, p. 499-513Article in journal (Refereed)
    Abstract [en]

    Studying the impregnation and distribution of oil-based preservative in dried wood is complicated as wood is a nonhomogeneous, hygroscopic and porous material, and especially of anisotropic nature. However, this study is important since it has influence on the durability of wood. To enhance the durability of thermally modified wood, a new method for preservative impregnation is introduced, avoiding the need for external pressure or vacuum. This article presents a study on preservative distribution in thermally treated Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) sapwood using computed tomography scanning, light microscopy, and scanning electron microscopy. Secondary treatment of thermally modified wood was performed on a laboratory scale by impregnation with two types of preservatives, viz. Elit Träskydd (Beckers) and pine tar (tar), to evaluate their distribution in the wood cells. Preservative solutions were impregnated in the wood using a simple and effective method. Samples were preheated to 170 °C in a drying oven and immediately submerged in preservative solutions for simultaneous impregnation and cooling. Tar penetration was found higher than Beckers, and their distribution decreased with increasing sample length. Owing to some anatomical properties, uptake of preservatives was low in spruce. Besides, dry-induced interstitial spaces, which are proven important flow paths for seasoned wood, were not observed in this species.

  • 4.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Sweden.
    Morén, Tom
    Luleå University of Technology, Sweden.
    Moisture properties of heat-treated Scots pine and Norway spruce sapwood impregnated with wood preservatives2012In: Wood and Fiber Science, ISSN 0735-6161, Vol. 44, no 1, p. 85-93Article in journal (Refereed)
    Abstract [en]

    An experiment was conducted on commercially heat-treated (HT) Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) sapwood collected from Ht Wood AB, Arvidsjaur, Sweden. Secondary treatment on HT wood was performed in laboratory scale by impregnating with water-repellent preservatives (a commercial one and pine tar) to evaluate their retention and different moisture-related properties. Preservative solutions were impregnated using a simple and effective method. Wood samples were heated at 170°C in a dry oven and were immediately immersed in preservative solutions. Considerable retention was observed in HT wood, particularly in pine. Moisture adsorption properties were measured after conditioning in a high-humidity environmental chamber (4°C and 84% RH). Experimental results showed that secondary treatment enhanced moisture excluding efficiencies by decreasing equilibrium moisture content, suggesting better hydrophobicity. Soaking test in water showed that antiswelling and water repellence efficiencies improved, especially in tar-treated wood. In addition, this type of treatment significantly decreased water absorption. It was also possible to decrease volumetric swellings. Thus, secondary treatment of HT wood with preservative, in particular with tar, improved dimensional stability and water repellency.

  • 5.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Hansson, Lars
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Evaluation of preservative distribution in thermally modified European aspen and birch boards using computed tomography and scanning electron microscopy2013In: Journal of Wood Science, ISSN 1435-0211, E-ISSN 1611-4663, Vol. 59, no 1, p. 57-66Article in journal (Refereed)
    Abstract [en]

    The aim of this experiment was to impregnate thermally modified wood using an easy and cost-effective method. Industrially processed thermally modified European aspen (Populus tremula L.) and birch (Betula pubescens Ehrh.) were collected and secondarily treated at the laboratory scale with the preservatives tung oil, pine tar and Elit Träskydd (Beckers) using a simple and effective method. Preservative uptake and distribution in sample boards were evaluated using computed tomography (CT) and scanning electron microscopy (SEM) techniques. Preservative uptake and treatability in terms of void volume filled were found the highest in Beckers and the lowest in tung oil-treated samples. Thermally modified samples had lower treatability than their counterpart control samples. More structural changes after thermal modification, especially in birch, significantly reduced the preservative uptake and distribution. The differences of preservatives uptake near the end grain were high and then decreased near the mid position of the samples length as compared with similar type of wood sample. Non-destructive evaluation by CT scanning provided a very useful method to locate the preservative gradients throughout the sample length. SEM analysis enabled the visualization of the preservative deposits in wood cells at the microstructural level.

  • 6.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Karlsson, Olov
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Uneven distribution of preservative in kiln-dried sapwood lumber of Scots pine: Impact of wood structure and resin allocation2012In: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 66, no 2, p. 251-258Article in journal (Refereed)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) sapwood lumber was collected after kiln drying and preservative treatment with Celcure AC 800 (a copper-amine wood preservative). Distribution of the preservative throughout the lumber was visually examined. Not all, but some samples showed specific localized areas without any preservative distribution throughout their entire length. Those samples were assessed further for anatomical properties, specifically in impregnated and unimpregnated areas. Additional study was conducted on the morphological nature and redistribution of lipophilic extractives using three different histochemical staining methods. Intrinsic wood properties – especially the frequency of axial resin canals and the percentage of canals blocked – were found to be responsible for the irregular distribution of the preservative. Furthermore, the inability to create continuous and frequent interstitial spaces due to the collapse of thin-walled ray cells throughout the lumber resulted in un-even distribution of preservatives. Staining techniques were useful to localize places with more or less abundance of extractives (e.g., fats) in impregnated and unimpregnated wood, which varied considerably. Histochemical observations revealed information pertaining to the kiln dry specific distribution and redistribution of extractives between the areas. Moreover, resin reallocation and modification in ray parenchyma and resin canals induced by kiln drying would be another reason for the impregnation anomalies.

  • 7.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Yang, Qian
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Accelerated Mold Test on Dried Pine Sapwood Boards: Impact of Contact Heat Treatment2013In: Journal of wood chemistry and technology, ISSN 0277-3813, E-ISSN 1532-2319, Vol. 33, no 3, p. 174-187Article in journal (Refereed)
    Abstract [en]

    We test the hypothesis that the combination of kiln drying of double-stacked boards and contact heat treatment will reduce the susceptibility of treated boards to colonization by mold fungi. Winter-felled Scots pine (Pinus sylvestris L.) sapwood boards were double-stacked in an industrial kiln in ''sapwood out'' and ''sapwood in'' positions. Dried samples were then contact heat-treated using a hot press at three different temperatures (140°C, 170°C, and 200°C) for three different periods (1, 3, and 10 min). An accelerated mold test was performed in a climate chamber where naturally mold-infected samples were used as a source of mold inocula. Contact heat treatment degraded the saccharides that accumulated at dried surfaces, and reduced the mold growth. The threshold temperature and time for inhibiting mold growth were 170°C for 10 min. However, for industrial application, the most feasible combination of temperature and time would be 200°C for 3 min. We concluded that double stacking/contact heat treatment used is an environmentally friendly alternative to chemicals for reducing mold on Scots pine sapwood boards.

  • 8.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Nitrogen rich Glasses and Glass Surfaces for High-tech and Specialty Applications2017Report (Refereed)
    Abstract [en]

    The aim of this project is to produce more chemical and mechanically durable glasses and glass surfaces having high thermal, mechanical and optical properties. The development of new materials is fundamental for the technological progress; their preparation and characterization lead to breakthrough applications as well as progress in our understanding of basic solid state materials properties. Glasses play an important role in our society and are expected to do so even more in the future. In the current proposed project we would like to extend the M-Si-O-N  ( M= Ca and Sr) system to T-Si-O-N (T= Transition metals e.g. Ti, Zr, Y, Mn etc) and Ln-Si-O-N ( Ln = Lanthanoids e.g. La, Ce, Pr, Eu, Gd, etc) systems. Applications of these nitrogen rich glasses include, as potential materials for use in more light-weight applications in modern communications equipment, in biomedical devices and where reductions in energy usage are critical. Furthermore, these glass materials can be used as a passive coatings on electronic substrates using their higher dielectric constants and elastic moduli to best advantage; special windows where their higher elastic moduli would allow them to remain stiff in thinner sections, thus allowing weight and energy savings; hard disk drives, again making use of higher modulus and lower densities to achieve higher rotation speeds; new bioactive oxynitride glasses and glass-ceramics with better load-bearing properties.

  • 9.
    Blom, Åsa
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Johansson, Jimmy
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Sivrikaya, Hüseyin
    Some factors influencing susceptibility to discoloring fungi and water uptake of Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and Oriental spruce (Picea orientalis) 2012In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 8, no 2, p. 139-144Article in journal (Refereed)
    Abstract [en]

    The heartwood and sapwood from Scots pine (PS), Norway spruce (PA), and Oriental spruce (PO) were tested for susceptibility to discoloring fungi and water uptake. In addition, annual ring width and density were measured. The methods used were Mycologg for testing growth of fungi and a modified version of EN 927-5 to investigate water uptake. For pine, the heartwood showed a lower water uptake and no discoloring fungi growing in the tests. The heartwood had a significantly higher density and smaller annual ring width than the sapwood. In PA the heartwood had significantly lower discoloration than sapwood. The total water uptake in g/m2 was significantly higher in sapwood, but not the calculated moisture content. As for wood properties, the density was significantly higher in sapwood compared to heartwood, although there were no differences in annual ring width. Regarding PO, differences in water uptake could be seen between sapwood and heartwood although the densities were similar. These results show that susceptibility to discoloring fungi and water uptake is hard to correlate to a single inherent property when looking at different wood species.

  • 10.
    Blom, Åsa
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Thörnqvist, Thomas
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Bergström, Mikael
    Presence of longitudinal cracks in planks from storm-felled pine (Pinus sylvestris L.) and spruce (Picea abies (L.) Karst.)2012In: Wood Material Science & Engineering, ISSN 1748-0272, E-ISSN 1748-0280, Vol. 7, no 4, p. 237-241Article in journal (Refereed)
    Abstract [en]

    After the severe storm Gudrun in southern Sweden in 2005, a quantitative study was done in order to investigate the presence of lengthwise crack on planks taken from storm-felled trees in southern Sweden, compared to planks from standing trees not subjected to this storm (central Sweden). The main yield from each log was examined. In total, 1087 pine (Pinus sylvestris) planks and 3626 spruce (Picea abies) planks from the storm-struck area were investigated and compared to 1953 spruce and 2000 pine planks from trees outside the storm-struck area. The examination of cracks was done visually on dried planks. For pine, 51.7% of the planks from storm-felled trees had a total length longer than 0.5 m, compared to 7.3% for the reference material. As for spruce, 11.0% of the planks from storm-felled trees had a total crack length of more than 0.5 m, compared to the reference material where 2.2% had cracks longer than 0.5 m. The results show that the storm-felled trees had more longitudinal cracks than the reference material and that pine was more likely to develop storm-related cracks than spruce.

  • 11.
    Carlsson, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
    Total cost accounting helps reduce resource use in manufacturing - New method to assess product sustainability2011In: Science for Environmental Policy, DG Enviroment News Alert Sevice, no 26, p. 11-Article, review/survey (Other (popular science, discussion, etc.))
  • 12.
    Dugic, Izudin
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Metal Expansion Penetration on Concave Casting Surfaces of Cylinder Heads Cast in Grey Cast Iron2009Conference paper (Refereed)
    Abstract [en]

    Cylinder heads have an extremely complex shape with large areas of concave casting surfaces. The concave casting surfaces are often associated with metal expansion penetration problems or other surface defects, e. g. surface shrinkage. The defects cause high production costs due to component rejection and increased fettling time. This report presents an investigation of the microstructure in grey cast iron close to the sand-metal interface affected by metal penetration in a complex shaped casting. The dominant penetration defect observed in the cylinder heads was expansion penetration. Even pre-solidification penetration and sand crack defects were observed. The microstructure found in the non penetrated areas is typical for solidification of grey iron cast in sand moulds.

  • 13.
    Ehlers, Sören
    et al.
    Ship Laboratory, Helsinki University of Technology.
    Enquist, Bertil
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Uniaxial tensile of steel dog-bone specimens2007Report (Other academic)
    Abstract [en]

    This test report describes the test arrangement and the results of 4 sets of tensile specimens tested under uniaxial tension. The Aramis 4M optical strain measuring system was used to study the necking phenomena. Strain histories for a large area of the specimen over the entire range of the test are obtained and presented. The manufactures given yield strengths were 235 MPa and 275 MPa, for the nominal thickness's of 4 mm and 6 mm respectively. The specimen dimensions were according to classification society's standards and of non standard geometry. The usage of optical strain measuring system entails very satisfactory information of the whole testing process, respectively the deformation distribution. This report shall serve as a basis reference for future research in the field of metal deformation analysis. True stress versus strain curves can be derived accurately and a comparison between the clamping displacement versus Aramis displacement at a certain point can be made based on the presented results.

  • 14.
    Ekevid, Torbjörn
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Maskinteknik.
    Lane, Håkan
    Wiberg, Nils-Erik
    Adaptive solid wave propagation: Influences of boundary conditions in high-speed train applications2006In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, Vol. 195, no 4-6, p. 236-250Article in journal (Refereed)
    Abstract [en]

    Wave propagation in solid materials is of great interest in many engineering applications. The fact that the area of interest changes with time creates a number of computational problems such as the need for a mesh density varying in space and time. This means that the mesh must be continuously updated and controlled, rendering a large demand of computer effort. In certain applications like railway mechanics there are mobile loads. A load speed close to the natural speed in the underlying soil causes specific problems, shock waves being one of them. The transmitted waves have to leave the defined finite element domain without reflection, which imposes a need for certain modelling methods. The paper will deal with quality controlled FE-procedures for wave propagation including error estimation and mesh refinement/coarsening. As an application an important problem from railway mechanics is considered. When a high-speed train approaches an area with decreasing thickness of underlying soft soil on a stiff rock it is expected that the reflection of the wave will increase the total amplitude of the wave. We will study this problem with the procedures described above in full 3D with partly absorbing boundaries

  • 15.
    Eliasson, Lars
    University of Kalmar, Department of Technology.
    Significance of raw material quality for finger jointing of knot freeboards2008In: END USER’S NEEDS FOR WOOD MATERIAL AND PRODUCTS / [ed] . Gard, W.F. & van de Kuilen, J.W.G., 2008, p. 41-50Conference paper (Refereed)
  • 16.
    Forde, Sean
    et al.
    National University of Ireland, Ireland.
    Hynes, Michael
    National University of Ireland, Ireland.
    Jonson, Bo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Dissolution of glass compositions containing no added lead in simulated lung fluid2008In: International journal of hygiene and environmental health (Print), ISSN 1438-4639, E-ISSN 1618-131X, Vol. 211, no 3-4, p. 357-366Article in journal (Refereed)
    Abstract [en]

    Six crystal glass compositions containing no added lead were studied with respect to the potential exposure of workers during the cold end working of crystal type glasses. During cutting and grinding of crystal glass, fine dusts are produced. These may be inhaled by the workers with subsequent partial dissolution of the dusts in the lung fluid. In order to provide a measure of the degree of dissolution in the case of the six crystal glass compositions produced in this work the release of antimony, barium, silicon, and bismuth was investigated by passing simulated lung fluid over powdered samples of the crystal compositions having a diameter of ca. 0.5 micron for a period of 21 days. The results show that it is possible to produce durable glass containing no added lead. While the leaching and weathering of the glass compositions studied here could be correlated with the mole ratio of alkali/silica and the degree of depolymerisation of the silica network, the dissolution of silica in simulated lung fluid seems to be independent of this property.

  • 17.
    Grund Bäck, Lina
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Karlsson, Stefan
    Glafo, the Glass Research Institute.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Physical properties and Raman Spectroscopy of mixed alkali/alkaline earth silicate glassesManuscript (preprint) (Other academic)
  • 18.
    Grund Bäck, Lina
    et al.
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Ali, Sharafat
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    Karlsson, Stefan
    Friedrich Schiller University of Jena, Germany.
    Wondraczek, Lothar
    Friedrich Schiller University of Jena, Germany.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
    X-ray and UV-Vis-NIR absorption spectroscopy studies of the Cu(I) and Cu(II) coordination spheere in (mixed) alkali-lime-silicate glassesManuscript (preprint) (Other academic)
  • 19.
    Gröndahl, Alexander
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Wernersson, Gustav
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Projektering av markarbete, parkeringsplatser, cykelställ m.m2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Arbetet tar upp lösningsförslag och val av lösning för en unik parkeringsplats på ett företag i Emmaboda. Lösningarna omfattar lokalt omhändertagande av dagvatten, val av beläggningstyper och trafiksäkerhet. Arbetet kommer att användas av Xylem till förfrågningsunderlaget för kommande anläggning av parkeringen.

  • 20.
    Hultberg, Ann-Charlotte
    et al.
    Växjö University. Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Larsson, Emelie
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Tilläggsisolering inom byggnadsvård2009Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [en]

    This report evaluates if there are any known facts that support that the hygroscopic and ecologic materials are better in supplement insulation than non hygroscopic. Different kind of insulate materials from these two mentioned groups are compared from without different kind of parameters.

  • 21.
    Håbecker, Linus
    et al.
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Strömberg, Victor
    Linnaeus University, Faculty of Technology, Kalmar Maritime Academy.
    Superhydrofobisk Coating: En studie som försöker minska rörfriktionsförluster med hjälp av invändig ytbehandling.2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The greatest loss of energy in a pipe system has many times been proven to be frictional loss. This study with that in mind, will try to answer if this type of loss can be prevented using a superhydrophobic coating on the inside of a pipe.

     

    This study uses two small-scale systems, one circulation system and one simplified system for freeflow testing. On both systems, measuring equipment is fixated close to the 1,5m test-pipe. Therefore, calculated and measured data is not distorted by the surrounding components. Measuring equipment is used to check volumetric flow, velocity, temperatures and differential-pressure. This data is later used to compare the frictional losses before and after applying the superhydrophobic coating.

     

    The results, after completed tests are the opposite of the expected results. The coating that has been used for this study causes a negative effect and, in turn results in a substantial increase of frictional loss.

  • 22.
    Karlsson, Stefan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Ion exchange processes on float glass surfaces2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Glass can be strengthened by ion exchange and this process is presently used inspecial applications e.g. aircraft windshields, displays and spectacle lenses allowinga higher production cost. Chemically strengthened float glass is moreexpensive than thermally strengthenened, but will likely find applications in futurebuilding and interior constructions where strength demands, design andshape prevent the use of thermal strengthening. The aim of this work is tostudy ion exchange on float glass surfaces. In longer terms, the chemicalstrengthening is planned to be applied to specific critical area e.g. around adrilled hole which without treatment deteriorates the overall strength of theglass.Strengthening the glass through ion exchange can be done in several ways butis most often referred to as the replacement of smaller ions in the glass structureby larger ions from the salt used for treatment. By determining concentrationvs. depth profiles of ion exchanged float glasses, it is possible to calculate thediffusion coefficients and activation energy for different ions. In this study, theless frequently studied approach single-side ion exchange of different ions ofcommercial float glass is described. The concentration vs. depth profiles weredetermined either by the use of the Surface Ablation Cell (SAC), which allowsthe continuous removal of the material from a flat glass surface by slow controlledisotropic dissolution or SEM-EDX.The results of the work are that similar diffusivities and concentration vs. depthprofiles are achieved with single-side ion exchange as from the traditional wayof immersing glass in molten salt bath. Ion exchange of Ag+ stains the floatglass on both sides giving it a yellow or amber-brownish colour. Unlike Ag+ ionexchange of Cu+ stains the float glass on the tin-side only, giving it a yellow,red or red-brown colour. Determining the concentration vs. depth profiles ofion exchanged float glasses with the SAC was convenient except for Ag+ whichwas determined with SEM-EDX. The work confirms that the procedure andequipment of the SAC are very cheap, easy to use and gives data similar tothose gained by much more expensive equipment. Calculated diffusion coefficientsof K+, Ag+ and Rb+ are in accordance with literature data while Cu+ and Cs+ diffusion coefficients were slightly lower. The diffusion coefficients of the different ions follow the order Ag+>K+>Cu+>Rb+>Cs+ and ranges between9.4E-10 and 4.8E-13 cm2s-1. The calculated activation energies for diffusion of K+, Ag+ and Cu+ corresponds with reported literature data and were calculated to: Ag+(air-side) 152 kJ/mol, Ag+(tin-side) 185 kJ/mol, K+ 108 kJ/mol and Cu+115 kJ/mol.

  • 23.
    Karlsson, Stefan
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Modification of Float Glass Surfaces by Ion Exchange2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Glass is a common material in each person’s life, e.g. drinking vessels, windows, displays, insulation and optical fibres. By modifying the glass surface it is possible to change the performance of the entire glass object, generally known as Surface Engineering. Ion exchange is a convenient technique to modify the glass surface composition and its properties, e.g. optical, mechanical, electrical and chemical properties, without ruining the surface finish of the glass.

     

    This thesis reports the findings of two different research tasks; characterisation of the single-side ion exchange process and the novel properties induced. The characterisation of the ion exchange process was mainly performed by utilising a novel analytical equipment: the Surface Ablation Cell (SAC), allowing continuous removal of the flat glass surface by controlled isotropic dissolution. SAC-AAS has provided concentration vs. depth profiles of float glass ion exchanged with K+, Cu+, Rb+ and Cs+. In addition, SEM-EDX has provided concentration vs. depth profiles of Ag+ ion exchanged samples and validation of a copper concentration vs. depth profile. From the concentration vs. depth profiles, the effective diffusion coefficients and activation energies of the ion exchange processes have been calculated. Depending on the treatment time and treatment temperature, penetration depths in the range of 5-10 μm (Rb+, Cs+), 20-30 μm (K+, Cu+) and 80-100 μm (Ag+) can be readily obtained. The effective diffusion coefficients followed the order Ag+>K+>Cu+>Rb+>Cs+. This is in accordance with the ionic radii for the alkali ions (K+<Rb+<Cs+) but reverse for the noble metal ions (Cu+<Ag+).

     

    The glass properties modified by single-side ion exchange have mainly been characterised by UV-VIS spectroscopy and flexural strength measurements. Cu+ and Ag+ ion exchange give rise to surface colouration, Cu+ copper-ruby and Ag+ yellow/amber. The surface-ruby colouration was found to depend on the residual tin ions in the tin-side of the float glass. The flexural strength was studied using the coaxial double ring-test method which also was suitable for holed specimens. The flexural strength of K+ ion exchanged float glass samples was found to substantially increase compared to untreated.

  • 24.
    Karlsson, Stefan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Jonson, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Diffusion and ion exchange of float glass: Na+ substitution by Cu+, Ag+, Rb+ and Cs+Manuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, single-side ion exchange on commercial float glass of the monovalent cations Cu+, Ag+, Rb+ and Cs+ is described. Data on the concentration profiles and calculations on thediffusion coefficients as well as activation energies are reported. The ion exchange of sodiumfor copper or silver is complex, since it is affected by the distribution of the element indifferent oxidation states. Anyhow, it was possible to determine the Cu+ diffusion coefficientsto be in the range 8.0E-12 to 3.4E-11 cm2s-1 and the activation energy 115 kJ/mol. Thepenetration depth of Cu+ exceeds 25 μm. The average diffusion coefficients of silver werecalculated to be in the range 2.1E-10 to 9.9E-10 cm2s-1 and the activation energies for samplestreated at temperatures higher than 470 ºC to 152 kJ/mol and 185 kJ/mol for air-side and tinsiderespectively. The Ag+ penetration depth is beyond 150 μm for the highest temperatures.Rb+-Na+ ion exchange reaches a penetration depth of approximately 10 μm with diffusioncoefficients ranging from 1.7E-12 to 8.6E-13 cm2s-1 while Cs+-Na+ ion exchange reaches apenetration depth of approximately 7 μm with diffusion coefficients ranging from 6.2E-13 to3.8E-13 cm2s-1.

  • 25.
    Karlsson, Stefan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Johansson, Marie
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Enquist, Bertil
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    The effect of single-side ion exchange on the flexural strength of plain and holed float glass containing a drilled hole2013In: European Journal of Glass Science and Technology. Part A: Glass Technology, ISSN 1753-3546, Vol. 54, no 2, p. 66-71Article in journal (Refereed)
    Abstract [en]

    The effect of single-side ion exchange (using a KNO3:KCl mixture) on the ring-on-ring flexural strength of float glass has been studied. Two ion exchanged series, treated at 450 and 515°C, were investigated. The ion exchanged samples showed approximately 160 respectively 100% increases in their arithmetic mean strength compared to as-received float glass. Furthermore, a series of samples containing drilled holes were studied in order to investigate the effect of single-side ion exchange on such common construction elements. The samples that contained drilled holes were ion exchanged at 450°C and showed around 140% increase of the fracture load compared to the untreated samples containing drilled holes. As a general observation, the ion exchange treatment induced ~110 MPa compressive stresses (515°C) and ~180 MPa compressive stresses (450°C). The ion exchanged samples showed no significant increase in stiffness. 

  • 26.
    Karlsson, Stefan
    et al.
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Jonson, Bo
    Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
    Reibstein, Sindy
    Institute of Glass and Ceramics, Friedrich-Alexander University of Erlangen-Nuremberg.
    Wondraczek, Lothar
    Institute of Glass and Ceramics, Friedrich-Alexander University of Erlangen-Nuremberg.
    Surface ruby colouring of float glass by sodium-copper ion exchange2013In: European Journal of Glass Science and Technology. Part A: Glass Technology, ISSN 1753-3546, Vol. 54, no 3, p. 100-107Article in journal (Refereed)
    Abstract [en]

    In this paper, colouration of the tin side of commercial soda lime silicate float glass by copper ion exchange is described and characterised. Data on the resulting concentration vs. depth profiles, absorbance vs. depth profiles, UV-Vis spectra  and CIE-Lab colour coordinates are reported. Fundamental aspects of the process of colouration are described and discussed. Optimum saturation of colouration is achieved after ion exchange at 520 °C for 10 h, or at 500 °C for 20 h, respectively. The depth of the coloured layer increases with increasing treatment time. At the same time, a linear dependency is found between the value of a and b in the CIE-Lab colour space for variations of treatment time and temperature. The latter indicates broad tunability of colouration between different shades of ruby and varying colour saturation. It is shown that colour arises from a redox reaction between copper species and residual tin ions, and that the depth of the coloured layer is governed by the position of the tin hump. The critical concentration of tin and copper to achieve colour formation was found to be ~0.25 mol% and >1 mol%, respectively.

  • 27.
    Karlsson, Stefan
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Jonson, Bo
    Linnaeus University, Faculty of Science and Engineering, School of Engineering.
    Wondraczek, Lothar
    Institute of Glass and Ceramics, Friedrich-Alexander University Erlangen-Nürnberg.
    Copper, silver, rubidium and caesium ion exchange in soda-lime-silicate float glass by direct deposition and in line melting of salt pastes2012In: European Journal of Glass Science and Technology. Part A: Glass Technology, ISSN 1753-3546, Vol. 53, no 1, p. 1-7Article in journal (Refereed)
    Abstract [en]

    We report the change of surface composition on commercial soda-lime-silica (SLS) float glass which results from single-side exchange of Na+ by Cu+, Ag+, Rb+ and Cs+, respectively. Ion exchange is achieved by in line melting of a directly deposited salt paste in a prolonged annealing procedure. Concentration profiles obtained and computed effective diffusion coefficients, as well as apparent activation energies for diffusion, are reported. Depending on exchange species, treatment time and treatment temperature, the penetration depths are in the range of 10-20 μm for K+, Cu+, Rb+ and Cs+. A penetration depth of >100 μm can readily be obtained for Ag+.

  • 28. Kroon, Martin
    A Probabilistic Model for Cleavage Fracture with a Length Scale2003In: Presented at 5th Euromech Solid Mechanics Conference, 17-22 August, 2003, Thessaloniki, Greece, 2003Conference paper (Refereed)
  • 29.
    Kroon, Martin
    Royal Institute of Technology KTH.
    A theoretical assessment of the influence of myosin filament dispersion on smooth muscle contraction2011In: Presented at ASME Summer Bioengineering Conference, 22-25 June, 2011, ASME Press, 2011, p. 145-146Conference paper (Refereed)
    Abstract [en]

    A new constitutive model for the biomechanical behavior of smooth muscle tissue is employed to investigate the influence of statistical dispersion in the orientation of myosin filaments. The number of activated cross-bridges between the actin and myosin filaments governs the contractile force generated by the muscle and also the contraction speed. A strain-energy function is used to describe the mechanical behavior of the smooth muscle tissue. The predictions from the constitutive model are compared to histological and isometric tensile test results for smooth muscle tissue from swine carotid artery. In order to be able to predict the active stress at different muscle lengths, a filament dispersion significantly larger than the one observed experimentally was required. Furthermore, a comparison of the predicted active stress for a case of uniaxially oriented myosin filaments and a case of filaments with a dispersion based on the experimental histological data shows that the difference in generated stress is noticeable but limited. Thus, the results suggest that myosin filament dispersion alone cannot explain the increase in active muscle stress with increasing muscle stretch.

  • 30. Kroon, Martin
    A Theoretical Model for Saccular Cerebral Aneurysm Growth: Deformation and Stress Analysis2007In: Presented at Summer Bioengineering Conference, 20-24 June, 2007, Keystone, Colorado, 2007Conference paper (Refereed)
  • 31. Kroon, Martin
    Material Characterization of Biological Membranes by Inverse Analysis2008In: Presented at 22nd International Congress of Theoretical and Applied Mechanics, 24-30 August, 2008, 2008Conference paper (Refereed)
  • 32.
    Kroon, Martin
    Royal Institute of Technology (KTH).
    Material Properties of Inhomogeneous Hyperelastic Membranes Assessed by Inverse Analysis2009Conference paper (Refereed)
  • 33. Kroon, Martin
    Modelling of fibroblast-controlled restructuring of collagen gels2010In: Presented at 6th World Congress in Biomechanics, 1-6 August, 2010, 2010Conference paper (Refereed)
  • 34. Kroon, Martin
    Saccular Aneurysm Growth in a Human Middle Cerebral Aneurysm: Deformation and Stress Analysis2007In: Presented at 44th Annual Meeting of the Society of Engineering Science, 21-24 October, 2007, 2007Conference paper (Refereed)
  • 35. Kroon, Martin
    Strengthening and Remodelling of Collagenous Networks2009In: Presented at 7th Euromech Solid Mechanics Conference, 7-11 September, 2009, 2009Conference paper (Refereed)
  • 36. Kroon, Martin
    Transiently cross-linked actin networks2012In: Presented at 10th World Congress on Computational Mechanics, 8-13 July, 2012, 2012Conference paper (Refereed)
  • 37.
    Kroon, Martin
    et al.
    Royal Institute of Technology, (KTH).
    Faleskog, Jonas
    Royal Institute of Technology, (KTH).
    Numerical implementation of a J2- and J3-dependent plasticity model based on a spectral decomposition of the stress deviator2013In: Computational Mechanics, ISSN 0178-7675, E-ISSN 1432-0924, Vol. 52, no 5, p. 1059-1070Article in journal (Refereed)
    Abstract [en]

    A new plasticity model with a yield criterion that depends on the second and third invariants of the stress deviator is proposed. The model is intended to bridge the gap between von Mises’ and Tresca’s yield criteria. An associative flow rule is employed. The proposed model contains one new non-dimensional key material parameter, that quantifies the relative difference in yield strength between uniaxial tension and pure shear. The yield surface is smooth and convex. Material strain hardening can be ascertained by a standard uniaxial tensile test, whereas the new material parameter can be determined by a test in pure shear. A fully implicit backward Euler method is developed and presented for the integration of stresses with a tangent operator consistent with the stress updating scheme. The stress updating method utilizes a spectral decomposition of the deviatoric stress tensor, which leads to a stable and robust updating scheme for a yield surface that exhibits strong and rapidly changing curvature in the synoptic plane. The proposed constitutive theory is implemented in a finite element program, and the influence of the new material parameter is demonstrated in two numerical examples.

  • 38.
    Kumar, Anuj
    et al.
    Natural Resources Institute Finland (Luke), Finland.
    Ryparová, Pavla
    Czech Technical University in Prague, Czech Republic.
    Hosseinpourpia, Reza
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Prošek, Zdeněk
    Czech Technical University in Prague, Czech Republic.
    Žigone, Jure
    Czech Technical University in Prague, Czech Republic.
    Petrič, Marko
    University of Ljubljana, Slovenia.
    Hydrophobicity and resistance against microorganisms of heat and chemically crosslinked poly(vinyl alcohol) nanofibrous membranes2019In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 360, p. 788-796Article in journal (Refereed)
    Abstract [en]

    Poly(vinyl alcohol) (PVA) is a water-soluble, semi-ionic and biocompatible polymer with excellent chemical and thermal stability. The chemical crosslinking of PVA membrane improve its stability towards humidity and water. In the present work, PVA nanofibrous membranes were fabricated using roller electrospinning techniques. The prepared membranes were crosslinked by heat treatment, glutaraldehyde dipping, and glutaraldehyde vapour. Furthermore, octadecyltrichlorosilane (OTS) treatment was used for hydrophobization of the crosslinked membranes. The prepared crosslinked membranes were analysed by scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The hydrophobization of PVA nanofibrous membranes were analysed by employing optical goniometer and auto-dynamic vapour sorption (AVS) techniques. Further, the PVA membranes were tested against algae and mould growth at in-vitro laboratory conditions. The SEM and FTIR results revealed significant differences in the morphology of the PVA nanofibrous membranes and in chemical bond formation due to crosslinking treatments. Water contact angle and AVS data confirmed a hydrophobization of PVA membranes by the treatments.

  • 39.
    Nilsson, Erik
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Kling, Kristoffer
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Konceptutveckling åt Kompostföretaget Balans2007Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The following rapport deals with the product development and construction of a compost reactor. The work started in late March 2007 to be concluded in early June.

    Since the construction group were given relatively free hands and was striding to come up with something revolutionary. Traditional brainstorming and a method called “Morphological chart” were used when developing the first basic concepts. These concepts were reviewed before the company, which picked out one of the ideas. Because of the size of the project the development was broken down in to single components. This way a basic structure for development has been created to make it easier for a new construction team to continue the work.

    This work resulted in a highly developed concept with the possibility for further construction. Some of the composts parts are still in a basic development stadium. Because material, surface roughness and tolerances not have been chosen, any construction drawings could not be made. These have been replaced with detailed sketches.

  • 40.
    Nilsson, Josefin A.
    et al.
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Johansson, Jimmy
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Characteristics of un-barked small-dimensioned birch for furniture and interior applications2015In: Proceedings of the XXVIIth International Conference Research for Furniture Industry, September 2015, Turkey, Gazi University , 2015, p. 175-181Conference paper (Other academic)
    Abstract [en]

    Many interior and furniture applications today use the natural aspects of wooden materials as a sales advantage. Defects such as knots, colour variations and rough surfaces are called rustic, natural or vintage and will be considered as an appreciated feature by the consumers. This approach changes the traditional view of wood quality for technical uses, and also the industrial processing of the material. As a consequence, more variables of the material than before must be handled in the production. A specific challenge in the furniture industry is to treat the raw materials under this view with as small volume losses as possible. One way of decreasing losses could be achieved by fewer processing steps. The present study aims at exploring the possibility to relate the dimensions of the trees already in the forest in relation to specific furniture components, and furthermore to leave the bark on for creating specific aesthetical characteristics to the end product. In Nordic countries, birch wood has gained interest in furniture and interior applications due to its unique aesthetic qualities. In today’s forestry industry, the small-dimensioned material from harvesting operations of birch forests is normally used by the pulp industry or as fire-wood. For the interior and furniture industries these fractions may be a new source of raw material supply. However, a proper utilization of the material requires a better knowledge of its properties. The potential of using un-barked material in round form also sets special requirements in the process. The present study presents results from initial testing concerning the behaviour of the bark in round wood pieces. For the experiments, round specimens of downy birch (Betula pubescens Ehrh.) measuring 450 mm in length and with varying diameters from 30 to 80 mm at the top were used. The green wood was dried with and without bark as to study the drying velocity in relation to dimensions. The bark was studied in respect of changes in bonding to the wood and its characteristics. The preliminary results are promising for using the material in interior and furniture applications. However, there are still some shortcomings to be addressed in the future, such as the impact of the bark in the drying process as well as the bark bonding.

  • 41.
    Paz-Garcia, Juan Manuel
    et al.
    Technical University of Denmark, Denmark.
    Johannesson, Björn
    Technical University of Denmark, Denmark.
    Ottosen, Lisbeth M.
    Technical University of Denmark, Denmark.
    Ribeiro, A. B.
    New University of Lisbon, Portugal.
    Rodriguez-Maroto, J. M.
    University of Málaga, Spain.
    Influence of the Chemical Interactions on the Removal Rate of Different Salts in Electrokinetic Desalination Processes2011In: Salt Weathering on Buildings and Stone Sculptures, University of Cyprus , 2011, , p. 8p. 373-380Conference paper (Other academic)
    Abstract [en]

    Electrokinetic desalination techniques have been successfully applied for the prevention of salt-induced deterioration problems of masonry and other construction materials. A mathematical model for electrochemical desalination treatments is described, based on the Poisson-Nernst-Planck system of equations and accounting for the chemical interactions between the species in the pore solution and the solid matrix. Due to their high abundance in the natural environment, chlorides, nitrates and sulfates are considered the main ions responsible to the salt decay processes in buildings materials and sculptures. Simulations of the desalination treatment of brick samples contaminated with these target contaminants are shown. The influence of the chemical interactions on the efficiency is highlighted in the results.

  • 42.
    Qian, Yang
    et al.
    Luleå University of Technology.
    Karlsson, Olov
    Luleå University of Technology.
    Ahmed, Sheikh Ali
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Dimensional Stability and Water Repellency of European Aspen Improved by Oxidized Carbohydrates.2013In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 8, no 1, p. 487-498Article in journal (Refereed)
    Abstract [en]

    Small samples from European aspen (Populus tremula L.) were impregnated with carbohydrates oxidized by Fenton's reagent using water in a vacuum, followed by heating in an oven at 103 °C. An antiswelling efficiency (ASE) of around 45% for wood treated with oxidized glucose and 35% for wood treated with oxidized sucrose was obtained. Samples treated with oxidized carbohydrates gave water repellent effectiveness (WRE) values over 35%. The decrease in cell wall thickness during impregnation was about 18% less in the presence of oxidized glucose than samples only treated with Fenton's reagent. An ASE of 20% for the wood samples that had been treated with oxidized glucose was obtained after 7 days of soaking in water. The reasons for the improvement in dimensional stability are discussed in this work.

  • 43.
    Sjöberg, Daniel
    et al.
    Lund University, Sweden.
    Nordebo, Sven
    Linnaeus University, Faculty of Technology, Department of Physics and Electrical Engineering.
    Gustafsson, Mats
    Lund University, Sweden.
    Convex optimization for optimal realization of material properties2014In: 2014 International Conference on Electromagnetics in Advanced Applications (ICEAA), 3-8 Aug. 2014, Palm Beach, IEEE Press, 2014, p. 782-785Conference paper (Refereed)
    Abstract [en]

    We show how the best passive approximation to a given target material or structure can be found byconvex optimization. The approach is based on a representation of positive real functions, where some of the parameters can be given physical relevance by comparison to low- and high-frequency asymptotics of the material or structure under study. A number of different optimization problems can be formulated, which generalizes previous approaches using sum rules.

  • 44.
    Stenudd, Stefan
    Member, Forest Products Society.
    Color response in silver birch during kiln-drying2004In: Forest products journal, ISSN 0015-7473, Vol. 54, no 6, p. 31-36Article in journal (Refereed)
    Abstract [en]

    Color change in silver birch caused by kiln-drying is a major down-grading factor and has substantial economical impact on high value furniture and flooring production. This study investigates the color responses to process parameters at different stages in the drying process. Samples were dried in a climate chamber and laboratory kilns and the color of dry wood was registered according to the CIE L*C*h color system. The results show that during the capillary drying phase (moisture content > 55 %) time is more important than temperature. Swift initial drying even at elevated temperatures increases the lightness and decreases the saturation. The major color changes occur later on, during the diffusive drying phase from approximately 30 to 20 percent moisture content. Here a combination of temperature, time, and initial moisture content is decisive for the final wood color. Swift drying in both stages even at moderately elevated temperatures results in a highly desirable brighter color.

  • 45.
    Stenudd, Stefan
    Linköping University.
    Colour changes in birch and beech during kilndrying2001In: Proceedings of the 7th International IUFRO Wood DryingConference, 2001, p. 300-305Conference paper (Refereed)
    Abstract [en]

    The aim of this study was to investigate the colour responses of Silver Birch (Betula pendula Roth.) and Beech(Fagus sylvatica L.) during conventional kiln-drying at industrial used conditions. The response of dryingtemperature, relative humidity, initial moisture content and board thickness on wood colour was investigated in two24 factorial designed experiments. The method was used to investigate and rank the effects of the variables and allpossible combinations of the variables with a minimum of tests. A total number of 224 clear green sapwood samplesdivided in to 32 groups were kiln-dried below 20% in a climate chamber, followed by room climate drying toapproximately 8%. Colour measurements were conducted on dry planed samples using a photoelectric colorimeterand results were expressed in the CIE L* (lightness) C* (chroma) h (hue) colour space. A comparison was also madewith 32 samples dried in room climate from green to 8%, differences were calculated and expressed as CIE (ΔE*ab)effects. The factorial experiments used high and low level for investigating the variables: temperature (60/30C),relative humidity (82/62%), initial moisture content (green/30%) and wood thickness (16/10 mm).Experimental results showed that drying temperature is the most important factor for the colour responses in theinvestigated intervals for both birch and beech. The second most important factor, for both species, was thickness ofthe wood. Relative humidity was found to be the third most important factor. Both species reacted in a similar way toincreasing temperature, thicker dimensions and high relative humidity. The wood colour became darker, moresaturated and redder compared to the reference material. The colour response effects were larger on birch comparedto beech.

  • 46.
    Stenudd, Stefan
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Colour Response in Drying of Nordic Hardwoods2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Colour and appearance of hardwood are of great importance for the interiorand furniture industry. The widespread use of transparent surface treatmentand a fashion that prescribe light colour on many species, means that deviationfrom the ideal have considerable impact on the industrial operations. Kilndrying is generally regarded as the process that has the greatest impact on thecolour of Nordic hardwood species. The lack of satisfactory explanation modelsfor many types of discoloration, however, complicates the control of the dryingprocess.This thesis is an attempt to increase the knowledge of which factors thatcontrol the appearance of some commonly found discolorations associated withdrying of beech, birch and oak. The main focus is on convection drying but alsothe influence of timber storage, pre-steaming and press drying has beeninvestigated for individual species. The studies have been conducted ascomparative studies based on design of experiments in which the colour wasdetermined using a colorimeter.Results show that reddish and dark discoloration of beech and birch duringconvective drying is mainly dependent on the temperature and time of exposurewhen the local moisture content exceeds the fibre saturation point. Theconversion of naturally occurring substances in birch into coloured compoundsis not due to active precursors created at high moisture content levels duringthe subsequent drying at low moisture content levels. Interior grey stain inbeech is caused by slow initial drying at low temperatures. Log storage in coldwinter and spring climate does not cause discoloration in beech. Birch becomeslighter when press-dried at high temperatures, resulting in a colour comparableto that of traditionally kiln dried wood. Steaming of oak before kiln dryingreduce the presence of brown discoloration, a general darkening of the woodoccurs at temperatures above 50°C.

  • 47.
    Stenudd, Stefan
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Colour response of Silver birch to press drying2003In: Proceedings of the 8th International IUFRO Wood DryingConference, 2003, p. 449-454Conference paper (Refereed)
    Abstract [en]

    Press drying is a rapid drying technique capable of reducing deformation, but also known to cause discolourationin some wood species. The colour of Silver birch is of great importance to the furniture and flooring industry, wherethe blond colour is highly appreciated. This study investigates the colour response in the core of 36 mm Silver birchsamples to the process variables: plate temperature, plate pressure and air pressure and to the material variable initialmoisture content. Short samples were press dried in a electrically heated laboratory press to approximately 10%moisture content and the interior colour of dry wood was registered according to the CIE L*C*h colour system. Theresults show that plate temperature is the most influential process variable controlling the wood colour. Hightemperature results in brighter more yellowish colour and reduced drying time. Other process and material variablesalso have some influence on the final colour but their contributions are smaller. Press drying of green wood at 170Cin normal atmospheric air pressure gave a wood colour comparable to that of conventionally kiln dried birch wood,only slightly darker and more reddish. The study indicates that press drying of Silver birch is possible from a colourperspective by careful selection of process parameters.

  • 48.
    Stenudd, Stefan
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Influence of moisture content, temperature and air humidity during kiln drying on the lightness of Silver birch (Betula pendula Roth.)2013Manuscript (preprint) (Other academic)
    Abstract [en]

    Discoloration of birch wood during kiln drying is a considerable problem for theindustry, since any deviation from the preferred bright whitish colour reduces theusability and value of the sawn timber. This study was conducted in an effort toincrease the understanding of how MC, temperature and air humidity influence silverbirch lightness. The air humidity was represented by the equilibrium moisturecontent (EMC). Within the investigated intervals of 20-70°C and 9-20% EMC, theCIELAB colorimetric responses, were measured at the surface and at depths of 1 and5 mm below the surface. The results showed that lightness reduction was mainlycontrolled by temperature when long as the local moisture content of wood (MC)exceeded the fibre saturation point (FSP). High temperature in combination withhigh EMC levels promote lightness reduction. Transformation of naturally occurringwood constituents into coloured substances takes place within hours and does notappear to be caused by process related precursors. This study showed that visuallydetectable darkening occurred in samples with a local MC exceeding the FSP whenexposed to drying temperatures higher than 40°C in combination with EMC levelsabove 15%.

  • 49.
    Stenudd, Stefan
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    Influence of Pre-heating on Brown Discoloration whenDrying Oak Heartwood2005In: Proceedings of the 9th InternationalIUFRO Wood Drying Conference, 2005, p. 127-130Conference paper (Refereed)
    Abstract [en]

    General loss of lightness and brown discoloration of oak heartwood are major problems to the European woodindustry. In this investigation has the effect of pre-heating timber to 100°C prior to conventional kiln drying at 15, 35and 50°C been studied. Pre-heating significantly reduced the level of local brown discolouring streaks and spots aswell as slightly increasing the general lightness. Drying temperature has a major impact on the development of localbrown discoloration as higher temperature cause more discoloration. The thermal effect on general lightness is lessdistinct and a turning point seams to exist in the 40-50°C range above which the lightness is distinctly reduced.

  • 50.
    Säll, Harald
    et al.
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Skog och trä.
    Källsner, Bo
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Skog och trä.
    Olsson, Anders
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Bending strength and stiffness of aspen sawn timber2007In: Quality Control for Wood and Wood Products, COST, Warsaw , 2007, p. 6-Conference paper (Refereed)
    Abstract [en]

    In order to investigate the possibility of using sawn timber of European aspen (Populus tremula L.) as a structural

    material, 150 pieces of the dimension 45 x 120 mm2 were selected from a sawmill in the south of Sweden. The material was

    visually strength graded using the Nordic standard INSTA 142 and the British standard BS 4978-1996, respectively.

    The timber pieces were also subjected to flat-wise bending in a Cook-Bolinder Ò strength grading machine. Finally all

    specimens were tested in edge-wise bending according to the European testing standard EN 408. Global and local moduli

    of elasticity as well as bending strength were determined.

    The results indicate that the visual grading rules, intended for use on Norway spruce and Scots pine, seem to work fairly

    well on European aspen. However, grading in a flat-wise bending machine like the Cook-Bolinder seems to give a lower

    correlation between stiffness and strength for aspen timber than generally found for coniferous. Further, the correlation

    between density and bending strength was found to be very low for the aspen timber tested. It was also noticed that

    the aspen timber has a slightly higher bending strength and modulus of elasticity than is the case for normal qualities

    of Norway spruce.

    The study indicates that sawn timber of European aspen grown in southern Sweden can be visually graded and used

    as structural material.

12 1 - 50 of 52
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