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  • 1. Al-Hamdi, A. M.
    et al.
    Sillanpää, M.
    Dutta, Joydeep
    Department of Nanotechnology, Water Research Center, Sultan Qaboos University, 123 Al-Khoudh, Musqat, Oman.
    Photocatalytic degradation of phenol in aqueous solution by rare earth-doped SnO2 nanoparticles2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 14, p. 5151-5159Article in journal (Refereed)
    Abstract [en]

    The influence of heterogeneous semiconductors on the photodegradation of phenol in water was investigated using doped tin dioxide (SnO2) nanoparticles. Photocatalysts of SnO2 were synthesized with lanthanum (La), cerium (Ce), and neodymium (Nd) dopants. These photocatalysts were synthesized from tin tetrachloride by sol-gel method with different dopant concentrations, and its photocatalytic degradation was investigated up to 0.8 % under UV-A light in aqueous suspensions. The photocatalytic oxidation reactions were studied by varying photocatalyst composition, light intensity, reaction time, pH of the reaction medium, and phenol concentration. It was found that the photocatalytic activity of rare earth-doped SnO2 for phenol decomposition under UV light irradiation was considerably higher than that of pure SnO2 nanoparticles. The experimental results also indicate that more than 95 % phenol was effectively oxidized in the presence of an aqueous suspension of La: SnO2 nanoparticles within 120 min of UV light irradiation.

  • 2. Al-Hinai, M. H.
    et al.
    Al-Hinai, A. T.
    Dutta, Joydeep
    Water Research Center, Sultan Qaboos University, 123 Al Khoud, Oman.
    Phase transformation behavior of zinc metastannates obtained by aqueous precipitation at different temperatures2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 20, p. 7282-7289Article in journal (Refereed)
    Abstract [en]

    Phase transformation studies in ZnO-SnO2 system from zinc metastannate (ZnSnO3) to zinc orthostannate (Zn2SnO4) with annealing temperature are reported. Non-centrosymmetric oxides show unique symmetry dependent and spontaneous polarization properties, which are technologically important. ZnSnO3 particles were synthesized by a simple aqueous synthesis at low temperatures designed with the assistance of potential-pH diagrams. ZnSnO3 particles synthesized at 4 A degrees C are more porous losing the ilmenite structure upon annealing at 200 A degrees C, while the other samples prepared at higher temperatures (25-65 A degrees C) becomes amorphous at 300 A degrees C. The phase transformation into the inverse spinel orthostannate phase occurs around 750 A degrees C in all the samples.

  • 3. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Analysis of phase diagram and diffusion coefficient for modeling of microsegregation2017In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, no 3, p. 1446-1460Article in journal (Refereed)
    Abstract [en]

    Thermodynamic description of phase diagram and diffusion data are required to model microsegregation during solidification of metallic alloys. Knowledge about non-equilibrium phase diagrams is essential for modeling of microsegregation in practical situations. Therefore, the aim of this study is to theoretically analyze phase diagram and diffusion data for calculation of microsegregation. For this purpose, aluminum-rich part of the Al-Cu phase diagram was recalculated under non-equilibrium conditions. Effect of excess vacancies formed during solidification was considered on both the phase diagram and diffusion coefficient. The results show that by modifying the phase diagram, the calculated results have better consistency with the experimental results, but there is still room for improvement. When the effect of excess vacancies on diffusion coefficient is considered, the modeling results show a much better correlation with the experimental results. The origin of discrepancies between the calculations and experiments are deeply discussed using current theories in solidification.

  • 4.
    Bagampadde, Umaru
    et al.
    Makerere University, Kampala.
    Karlsson, R.
    KTH.
    Laboratory studies on stripping at bitumen/substrate interfaces using FTIR-ATR2007In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, no 9, p. 3197-3206Article in journal (Refereed)
    Abstract [en]

    A technique based on Fourier Transform Infrared Spectroscopy-Attenuated Total Reflectance (FTIR-ATR) was developed and used to study movement of water into bitumen/substrate interfaces, as well as to characterize stripping. Bitumens from different sources were used and applied on various substrates (silicon, germanium and zinc selenide) as thin films. The influence of bitumen type, substrate type, temperature, film thickness and modification with amines, on water damage was studied. The technique gave information on water flow into interfaces and how stripping possibly occurs. It distinguished between stripping and non-stripping bitumens. At least one of three processes occurred, namely water diffusion, film fracture, and bitumen displacement by water, respectively. The diffusion of water did not obey Fick's law. Stripping was influenced by bitumen source when silicon and germanium substrates were used. Notching the films made the process of water entry almost occur immediately. Additives significantly reduced stripping in the moisture-sensitive bitumen on silicon and germanium substrates, even after film notching. Although, good agreement was observed between tests for the bitumens that did not strip, the tests on stripping bitumens showed poor agreement.

  • 5. Dutta, Joydeep
    et al.
    Perrin, J.
    Emeraud, T.
    Laurent, J. -M
    Smith, A.
    Pyrosol deposition of fluorine-doped tin dioxide thin films1995In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 30, no 1, p. 53-62Article in journal (Refereed)
  • 6. Eichhorn, S. J.
    et al.
    Dufresne, A.
    Aranguren, M.
    Marcovich, N. E.
    Capadona, J. R.
    Rowan, S. J.
    Weder, C.
    Thielemans, W.
    Roman, M.
    Renneckar, S.
    Gindl, W.
    Veigel, S.
    Keckes, J.
    Yano, H.
    Abe, K.
    Nogi, M.
    Nakagaito, A. N.
    Mangalam, A.
    Simonsen, J.
    Benight, A. S.
    Bismarck, A.
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Peijs, T.
    Review: current international research into cellulose nanofibres and nanocomposites2010In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 45, no 1, p. 1-33Article, review/survey (Refereed)
    Abstract [en]

    This paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation of cellulose nanocomposites and new developments in the area, with particular emphasis on applications. The types of cellulose nanofibres covered are those extracted from plants by acid hydrolysis (nanowhiskers), mechanical treatment and those that occur naturally (tunicate nanowhiskers) or under culturing conditions (bacterial cellulose nanofibrils). Research highlighted in the article are the use of cellulose nanowhiskers for shape memory nanocomposites, analysis of the interfacial properties of cellulose nanowhisker and nanofibril-based composites using Raman spectroscopy, switchable interfaces that mimic sea cucumbers, polymerisation from the surface of cellulose nanowhiskers by atom transfer radical polymerisation and ring opening polymerisation, and methods to analyse the dispersion of nanowhiskers. The applications and new advances covered in this review are the use of cellulose nanofibres to reinforce adhesives, to make optically transparent paper for electronic displays, to create DNA-hybrid materials, to generate hierarchical composites and for use in foams, aerogels and starch nanocomposites and the use of all-cellulose nanocomposites for enhanced coupling between matrix and fibre. A comprehensive coverage of the literature is given and some suggestions on where the field is likely to advance in the future are discussed.

  • 7.
    Fahlén, Jesper
    et al.
    STFI, Swedish Pulp and Paper Res. Inst..
    Salmén, Lennart
    STFI, Swedish Pulp and Paper Res. Inst..
    Cross-sectional structure of the secondary wall of wood fibers as affected by processing2003In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 38, no 1, p. 119-126Article in journal (Refereed)
    Abstract [en]

    Understanding the arrangement of wood polymers within the fiber wall is important for understanding the mechanical properties of the fibers themselves. Due to their high load bearing ability, the arrangement of cellulose fibrils within the cell wall are of special interest. In this work AFM-Atomic Force Microscopy-in combination with image processing has been used to obtain more information about the arrangement of cellulose aggregates (fibrils) in the secondary cell wall layer of spruce wood. The effects of chemical processing on the arrangement of these cellulose aggregates were also studied. Enlargement of cellulose aggregates was found in the initial phase of the kraft cook. This increase in cellulose aggregate dimensions depended mostly on temperature for treatment temperatures above 140degreesC, regardless of the amount of alkali present. Although hemicelluloses are lost to various degrees under alkaline conditions, the increase in cellulose aggregate size was mainly related to thermally induced rearrangement of the cellulose molecules. The mean side length of cellulose aggregates was found to be around 18 nm in unprocessed wood and 23 nm in processed wood. The cellulose aggregates were assumed to be square shaped in cross section in both cases.

  • 8. Girlanda, Orlando
    et al.
    Tjahjanto, Denny D.
    Ostlund, Soren
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Schmidt, Lars E.
    On the transient out-of-plane behaviour of high-density cellulose-based fibre mats2016In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 51, no 17, p. 8131-8138Article in journal (Refereed)
    Abstract [en]

    High density cellulose-based materials have been widely used for electrical insulation and (interior) construction or structural material. Similar to typical paper/board materials, the microstructure of high-density fibre mats consists of a porous network of cellulose fibres, which contributes to its highly non-linear mechanical response. Such fibre mats exhibit strong anisotropic material behaviour as well as significant transient (time-or rate-dependent) behaviour. The present investigation is aimed at studying the transient behaviour of high-density cellulose fibre mats, particularly during out-of-plane compression. A viscoelastic-viscoplastic constitutive model dedicated for high-density cellulose-based materials has been used to simulate the responses of the high-density cellulose-based fibre mats upon two types of transient loading, i.e. compressive creep and stress relaxation. The predictions of the model are then compared to the corresponding experimental characterization results, which indicate that material densification mechanism plays a more critical role during out-of-plane compression creep than in stress relaxation.

  • 9.
    Hailesilassie, Biruk W.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Schuetz, Philipp
    Jerjen, Iwan
    Hugener, Martin
    Partl, Manfred N.
    Dynamic X-ray radiography for the determination of foamed bitumen bubble area distribution2015In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 1, p. 79-92Article in journal (Refereed)
    Abstract [en]

    Foam bitumen is highly efficient in wetting and coating the surface of mineral aggregate at lower temperature. In order to improve understanding and characterization of the bitumen foam, X-ray radiography was used to study the formation and decay of bitumen foam in 2D representation. Image segmentation analysis was used to determine the foam bubble size distribution. In addition, the main parameters influencing foam bitumen formation, water content, and temperature were also investigated. The results demonstrate the influence of the water content on morphology and expansion of foam bitumen bubbles. Adding more water in the foaming process leads to quick collapse of bubbles and intensifies coalescence of foam bitumen. Higher temperatures produces larger bubbles at early foaming stage compared to lower temperature. Moreover the morphology of bubble formation depends on the types of bitumen used. An exponential function has been implemented to represent the bubble area distribution.

  • 10.
    He, Junjing
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Formation of creep cavities in austenitic stainless steels2016In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 51, no 14, p. 6674-6685Article in journal (Refereed)
    Abstract [en]

    The possibility of creep cavity formation at subboundaries in austenitic stainless steels is analysed. It is demonstrated that such nucleation is thermodynamically feasible. A minimum stress must be exceeded in order to create cavities. The nucleation is assumed to take place where subboundaries on one side of a sliding grain boundary meet subgrain corners on the other side (double ledge models). Alternative cavitation positions can be found where particles meet subboundaries. The nucleation model can quantitatively predict the observed nucleation rate. The model gives a nucleation rate that is proportional to the creep rate in agreement with many experiments

  • 11.
    He, Junjing
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Modelling grain boundary sliding during creep of austenitic stainless steels2016In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 51, no 6, p. 2926-2934Article in journal (Refereed)
    Abstract [en]

    Two models are presented for grain boundary sliding (GBS) displacement during creep. GBS is considered as crucial for the formation of creep cavities. In the first model, the shear sliding model, GBS is accommodated by grains freely sliding along the boundaries in a power-law creeping material. The GBS rate is proportional to the grain size. In the second model, the shear crack model, the sliding boundaries are represented by shear cracks. The GBS rate is controlled by particles in the boundaries. In both models, the GBS displacement rate is proportional to the creep strain rate. Both models are consistent with existing experimental observations for GBS during creep of austenitic stainless steels. For cavity nucleation at particles, Harris’ model (1965) for the relationship between GBS and a critical particle size has been analysed and found to be in agreement with observations.

  • 12.
    Honorato, Camila
    et al.
    Abo Akad Univ, Proc Chem Ctr, Lab Wood & Paper Chem, SF-20500 Turku, Finland..
    Kumar, Vinay
    Abo Akad Univ, Ctr Funct Mat, Lab Paper Coating & Converting, SF-20500 Turku, Finland..
    Liu, Jun
    Abo Akad Univ, Proc Chem Ctr, Lab Wood & Paper Chem, SF-20500 Turku, Finland..
    Koivula, Hanna
    Univ Helsinki, Dept Food & Environm Sci, FIN-00014 Helsinki, Finland..
    Xu, Chunlin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. Process Chemistry Centre, Laboratory of Wood and Paper Chemistry, Åbo Akademi University, Porthansgatan 3, Åbo/Turku, Finland.
    Toivakka, Martti
    Abo Akad Univ, Ctr Funct Mat, Lab Paper Coating & Converting, SF-20500 Turku, Finland..
    Transparent nanocellulose-pigment composite films2015In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 22, p. 7343-7352Article in journal (Refereed)
    Abstract [en]

    Biodegradable coatings and films of cellulose nanofibers (CNFs) or a combination of CNFs and inorganic fillers, such as clay or calcium carbonate (CaCO3), can provide a replacement for non-biodegradable plastic coatings as barrier layers in packaging boards. In this work, transparent composite films were prepared from CNFs of Pinus radiata and Eucalyptus using different amounts of clay and CaCO3 as fillers. The impact of raw material (softwood vs. hardwood), TEMPO oxidation levels and filler type (clay vs. CaCO3) on film properties was studied. Pinus radiata CNF films had superior mechanical properties to Eucalyptus CNF films, but no significant differences were observed in the barrier and optical properties. Clay seemed to work better as filler compared to CaCO3, in terms of its impact on film properties. Composite films with CaCO3 as filler were highly brittle with inferior properties to clay-CNF films, and an uneven distribution and agglomeration of the CaCO3 mineral particles was evident in SEM images. Based on the results, clay as filler in CNF coatings is preferred for targeting packaging board applications. Rheological characterisation of the CNF suspensions revealed shear-thinning behaviour, with the CNF from Eucalyptus having higher viscosities and lower power-law indices when compared to the CNF from P. radiata.

  • 13.
    Hou, Ziyong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Northeastern Univ, State Key Lab Rolling & Automat, Shenyang 110819, Liaoning, Peoples R China.
    Babu, R. Prasath
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Microstructure evolution during tempering of martensitic Fe-C-Cr alloys at 700 A degrees C2018In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 53, no 9, p. 6939-6950Article in journal (Refereed)
    Abstract [en]

    The microstructure evolution of two martensitic alloys Fe-0.15C-(1.0 and 4.0) Cr (wt%) was investigated, using X-ray diffraction, electron backscatter diffraction, electron channeling contrast imaging and transmission electron microscopy, after interrupted tempering at 700 A degrees C. It was found that quenching of 1-mm-thick samples in brine was sufficient to keep most of the carbon in solid solution in the martensite constituent. The high dislocation density of the martensite decreased rapidly during the initial tempering but continued tempering beyond a few minutes did not further reduce the dislocation density significantly. The initial martensitic microstructure with both coarse and fine laths coarsened slowly during tempering for both alloys. However, a clear difference between the two alloys was distinguished by studying units separated by high-angle boundaries (HABs). In the low-Cr alloy, M3C precipitates formed and coarsened rapidly, thus they caused little hindrance for migration of HABs, i.e., coarsening of the HAB units. On the other hand, in the high-Cr alloy, M7C3 precipitates formed and coarsened slowly, thus they were more effective in pinning the HABs than M3C in the low-Cr alloy, i.e., coarsening of HAB units was minute in the high-Cr alloy.

  • 14.
    Huang, Fang
    et al.
    University of New Brunswick.
    Li, Kecheng
    University of New Brunswick.
    Kulachenko, Artem
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
    Measurement of interfiber friction force for pulp fibers by atomic force microscopy2009In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 44, no 14, p. 3770-3776Article in journal (Refereed)
    Abstract [en]

    Interfiber friction in paper exists in fiber suspensions, fiber flocs, and fiber networks. The interfiber friction force is, therefore, important both in papermaking and in the use of paper. The objective of this research is to develop a methodology using atomic force microscopy (AFM) for the direct measurement of the friction force between pulp fibers. Different factors such as AFM scanning velocity, contact area, and fiber surface roughness were investigated. The results show that AFM is an effective tool for measuring micro-scale interfiber friction forces. Both AFM scanning velocity and fiber surface roughness affect the measured results. The coefficient of friction increases, but the initial adhesion force decreases, with increasing fiber surface roughness.

  • 15.
    Janis, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, Hiroyuki
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    An experimental study on the influence of particles on grain boundary migration2010In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 45, no 8, p. 2233-2238Article in journal (Refereed)
    Abstract [en]

    The pinning effect of particles on grain boundary migration was studied in a Fe-20 mass % Cr alloy deoxidised with Ti and Zr. The different nitrogen contents (65, 248 and 490 ppm) were used to vary the number of precipitated inclusions. The specimens from equiaxed zones of metal samples with different particle densities were examined by in situ observations during a 60-min holding time at 1200 and 1400 degrees C in a Confocal Scanning Laser Microscope. The change of particles pinning effect on the grain growth was described by an average grain size, (D) over bar (A), and the ratio between the perimeter and area of grains, P-GB/A(G). It was found that the pinning effect of particles (mostly complex Ti-Zr oxynitrides) on grain growth decreased with a decreased nitrogen content in the metal. Furthermore, the effect of particles decreased with an increased temperature of treatment, due to the reduction of the number of particles on the grain boundaries.

  • 16.
    Kapilashrami, Era
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Wetting characteristics of oxygen-containing iron melts on refractory oxides2005In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 40, no 9-10, p. 2371-2375Article in journal (Refereed)
    Abstract [en]

    As part of refractory erosion studies, the wetting behaviour of molten iron containing varying amounts of oxygen on refractory oxides was investigated by the sessile drop method. The oxides investigated in the present work were alumina, silica and mullite. The reactions were followed in static as well as dynamic modes, under isothermal conditions, through contact angle measurements. Other parameters investigated in the present study were temperature and oxygen partial pressure. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen at constant partial pressure, came into contact with the surface of the drop. At a critical level of oxygen in the metal drop, a reaction product started forming at the drop/substrate interface and at this stage the contact angle dropped suddenly. In all cases there was a tendency for the contact angle to increase after this minimum. In the alumina case, the iron drop moved away from the reaction site, once the product layer had been formed at the interface, probably due to the imbalance in the surface forces. In the case Of SiO2 and mullite, liquid slags were formed. The substrates were analysed through SEM and EDS. The reaction products identified were in agreement with thermodynamic predictions. In the case Of SiO2, deep erosions were formed along the periphery of the drops, probably due to Marangoni flow. The possible mechanisms of the reactions and their impact on refractory erosion are discussed in the light of the present experimental results.

  • 17.
    Karlsson, Robert
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Isacsson, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Ekblad, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Rheological characterisation of bitumen diffusion2007In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, no 1, p. 101-108Article in journal (Refereed)
    Abstract [en]

    Diffusion is considered important in the process of mixing old and new binders during asphalt recycling. The degree of mixing is presumed to greatly influence the final properties of recycled asphalt concrete. Previously, studies have been undertaken to investigate diffusion using FTIR-ATR (Fourier Transform Infrared Spectroscopy using Attenuated Total Reflectance). A need was identified to verify, if the rates of diffusion detected using FTIR-ATR were accompanied by changes in rheological properties. In this paper, a dynamic shear rheometer (DSR) with parallel plates is used for monitoring diffusion. Diffusion coefficients obtained at 60, 80 and 100 degrees C from tests of a soft bitumen (rejuvenator) diffusing into a stiff one are presented. The diffusion coefficients determined are compared with the corresponding diffusion coefficients obtained using FTIR-ATR. The comparison shows that the rates of diffusion detected by the DSR are of the same magnitude, but somewhat higher than the ones detected by FTIR-ATR.

  • 18. Khan, Zaheer Abbas
    et al.
    Kumar, Rachana
    Mohammed, Waleed S
    Hornyak, Gabor L
    Dutta, Joydeep
    Asian Institute of Technology, Thailand.
    Optical thin film filters of colloidal gold and silica nanoparticles prepared by a layer-by-layer self-assembly method2011In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, no 21, p. 6877-6882Article in journal (Refereed)
    Abstract [en]

    A novel fabrication method for optical thin film filters based on the self-organization of alternating layers of colloidal gold and silica nanoparticles (NP) is reported. The filter is designed to work in the deep-UV to visible spectral range. The spectral absorption peaks are tuned by three parameters: the organic capping ligand of the gold NPs (citrate, chitosan, poly (diallyl-dimethylammonium)- chloride or PDDA); the capping environment (bare, chitosan, or PDDA) of the silica NPs and the thickness of the film. Precise control of the transmission color (less than 1% color distance per layer), is achieved by changing the film thickness. Exploitation of the self-assembly process should lead to the facile production of highly reliable large area thin film optical filters at considerably lower costs.

  • 19. Kisonen, Victor
    et al.
    Prakobna, Kasinee
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Xu, Chunlin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Salminen, Arto
    Mikkonen, Kirsi S.
    Valtakari, Dimitar
    Eklund, Patrik
    Seppala, Jukka
    Tenkanen, Maija
    Willfor, Stefan
    Composite films of nanofibrillated cellulose and O-acetyl galactoglucomannan (GGM) coated with succinic esters of GGM showing potential as barrier material in food packaging2015In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 8, p. 3189-3199Article in journal (Refereed)
    Abstract [en]

    Nanofibrillated cellulose (NFC)-Norway spruce O-acetyl-galactoglucomannan (GGM) composite films were coated either with a novel succinic ester of GGM or with native GGM. NFC films were made for reference. The succinic ester of GGM was synthesised at low (GGM-Su1) and high (GGM-Su2) degree of substitution to obtain different level of water repellence. GGM and its succinic esters had good affinity with NFC substrate. This made it possible to implement the barrier functionality on the NFC network with the adequate mechanical properties. The coatings further enhanced the already excellent oxygen permeability properties, achieving 0.1 [(cm(3) A mu m)(m(2) kPa d)] as the lowest value with the NFC-GGM film double-coated with GGM-Su2. The films demonstrated pronounced stiffness by adding GGM to the NFC, as well as coating of GGM-Su2 on the NFC-GGM films at 0-90 % relative humidity. The films turned out to be impenetrable with grease even at high temperatures. NFC-GGM film with GGM-Su2 coating exhibited hydrophobic characteristics according to the water contact angle measurements. It was shown that adding 5.5 wt% of GGM to a NFC film and further 5.4 wt% of coating of GGM-Su or GGM on the film may highly enhance the feasibility of the biocomposites to be used for food packaging to replace typical oil-based non-biodegradable plastics currently used.

  • 20. Kuhl, Ellen
    et al.
    Holzapfel, Gerhard A.
    A continuum model for remodeling in living structures2007In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, no 21, p. 8811-8823Article in journal (Refereed)
    Abstract [en]

    A new remodeling theory accounting for mechanically driven collagen fiber reorientation in cardiovascular tissues is proposed. The constitutive equations for the living tissues are motivated by phenomenologically based microstructural considerations on the collagen fiber level. Homogenization from this molecular microscale to the macroscale of the cardiovascular tissue is performed via the concept of chain network models. In contrast to purely invariant-based macroscopic approaches, the present approach is thus governed by a limited set of physically motivated material parameters. Its particular feature is the underlying orthotropic unit cell which inherently incorporates transverse isotropy and standard isotropy as special cases. To account for mechanically induced remodeling, the unit cell dimensions are postulated to change gradually in response to mechanical loading. From an algorithmic point of view, rather than updating vector-valued microstructural directions, as in previously suggested models, we update the scalar-valued dimensions of this orthotropic unit cell with respect to the positive eigenvalues of a tensorial driving force. This update is straightforward, experiences no singularities and leads to a stable and robust remodeling algorithm. Embedded in a finite element framework, the algorithm is applied to simulate the uniaxial loading of a cylindrical tendon and the complex multiaxial loading situation in a model artery. After investigating different material and spatial stress and strain measures as potential driving forces, we conclude that the Cauchy stress, i.e., the true stress acting on the deformed configuration, seems to be a reasonable candidate to drive the remodeling process.

  • 21. Kymalainen, M.
    et al.
    Hautamaki, S.
    Lillqvist, Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, L.
    Surface modification of solid wood by charring2017In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, no 10, p. 6111-6119Article in journal (Refereed)
    Abstract [en]

    Most wooden structures for outdoor applications require repetitive maintenance operations to protect the surfaces from adverse effects of weathering. One-sided surface modification of boards with a relatively fast charring process has the potential to increase the durability and service life of wooden claddings. To assess some weathering-related effects on surface charred wood, spruce and pine sapwood were subjected to a series of long charring processes (30-120 min) at a moderate temperature of 250 A degrees C and to a short one (30 s) at a high temperature of 400 A degrees C. The wettability and contact angles of treated samples were investigated, and the heat transfer was measured along with the micromorphological changes taking place in the material. The result revealed an increased moisture resistance of charred spruce sapwood and an increased water uptake of pine sapwood. The contact angles of both wood species improved compared to references. Heat conduction measurement revealed that only a thin section of the wood was thermally modified. Some micromorphological changes were recorded, especially on the inside walls of the lumina. The results show that spruce sapwood has an improved resistance towards moisture-induced weathering, but more studies are needed to unlock the potential of surface charred wood.

  • 22. Laine, Kristiina
    et al.
    Segerholm, Kristoffer
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Wålinder, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Rautkari, Lauri
    Ormondroyd, Graham
    Hughes, Mark
    Jones, Dennis
    Micromorphological studies of surface densified wood2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 5, p. 2027-2034Article in journal (Refereed)
    Abstract [en]

    Scots pine (Pinus sylvestris L.) wood was surface densified in its radial direction in an open press with one heated plate to obtain a higher density on the wood surface whilst retaining the overall thickness of the sample. This study investigated the effect of temperature (100, 150 and 200 A degrees C) and press closing speed (5, 10 and 30 mm/min, giving closing times of 60, 30 and 10 s, respectively) on the micromorphology of the cell-wall, as well as changes occurring during set-recovery of the densified wood. The micromorphology was analysed using scanning electron microscopy (SEM) combined with a sample preparation technique based on ultraviolet-excimer laser ablation. Furthermore, the density profiles of the samples were measured. Low press temperature (100 A degrees C) and short closing time (10 s) resulted in more deformation through the whole thickness, whilst increasing the temperature (150 and 200 A degrees C) and prolonging the closing time (30 and 60 s) enabled more targeted deformation closer to the heated plate. The deformation occurred in the earlywood regions as curling and twisting of the radial cell-walls, however, no apparent cell-wall disruption or internal fracture was observed, even at low temperatures and fast press closing speed, nor after soaking and drying of the samples. In the SEM-analysis after soaking and drying, it was noticed that the cells did not completely recover their original form. Thus, part of the deformation was considered permanent perhaps due to viscoelastic flow and plastic deformation of the cell-wall components.

  • 23.
    Laurell Lyne, Åsa
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Wallqvist, V.
    Rutland, Mark
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Claesson, Per
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Surface wrinkling: The phenomenon causing bees in bitumen2013In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 20, p. 6970-6976Article in journal (Refereed)
    Abstract [en]

    The so called "bee phenomenon" in bitumen has been investigated by means of AFM quantitative nanomechanical property mapping. Bees are a phenomenon that can be observed by topography measurements using AFM. The characteristic "bee" appearance comes from regions with alternating higher and lower bands in the surface topography of bitumen, which are surrounded by a flat area. The proposed mechanism for bee formation is phase separation and differential contraction during cooling from melt temperatures leading to wrinkling due to differences in the elastic modulus of the material phases. Using a laminate wrinkling model, the thickness of the bee laminate was calculated from the wavelengths and Young's moduli of the bee laminate and the matrix. It was found to vary between 70 and 140 nm for the five bitumen samples that contained significant amounts of wax.

  • 24. Lemaire, L.
    et al.
    Scholz, S. M.
    Bowen, P.
    Dutta, Joydeep
    Hofmeister, H.
    Hofmann, H.
    Effect of CuO additives on the reversibility of zirconia crystalline phase transitions1999In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 34, no 9, p. 2207-2215Article in journal (Refereed)
  • 25. Lingois, P.
    et al.
    Berglund, Lars A.
    Modeling elastic properties and volume change in dental composites2002In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 37, no 21, p. 4573-4579Article in journal (Refereed)
    Abstract [en]

    A modeling approach was applied to study elastic properties and volume change in dental composites. Mechanics modeling results were compared with experimental data in model materials of known composition where the filler content was varied. Composite behavior was predicted based on polymer and filler properties in order to improve basic understanding. Model predictions agree well with data. The models were used to discuss effects of resin properties, filler volume fraction and microstructure (particle shape and filler size distribution).

  • 26. Lingois, P.
    et al.
    Berglund, Lars A.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Greco, A.
    Maffezoli, A.
    Chemically induced residual stresses in dental composites2003In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 38, no 6, p. 1321-1331Article in journal (Refereed)
    Abstract [en]

    In several European countries, dental composites are replacing mercury-containing amalgams as the most common restorative materials. One problem with dental composites is residual stresses which may lead to poor performance of the restoration. In the present study, a combined modeling and materials characterization approach is presented and predictions compare well with experimental data on residual stresses. The model takes stress relaxation into account through the complete relaxation time spectrum of the resin. The approach allows for detailed parametric studies where resin and composite composition as well as cure conditions may be tailored with respect to residual stress generation.

  • 27. Liu, Tie
    et al.
    Wang, Qiang
    Zhang, Hong-Wei
    Lou, Chang-Sheng
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    He, Ji-Cheng
    Effects of high magnetic fields on solidification microstructure of Al-Si alloys2011In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 46, no 6, p. 1628-1634Article in journal (Refereed)
    Abstract [en]

    The effects of high magnetic fields on the solidification microstructure of Al-Si alloys were investigated. Al-7.2 wt%Si and Al-11.8 wt%Si alloys were solidified in various high magnetic fields at different cooling rates. The secondary dendrite arm spacing (SDAS) of the primary Al dendrites and the lamellar spacing (LS) of the eutectics were measured. It was found that the application of a high magnetic field could decrease the SDAS of the primary Al dendrites in Al-7.2 wt% Si alloys and the LS of the eutectics in Al-11.8 wt% Si alloys. The effects of the high magnetic field on the SDAS decreased with increasing cooling rate. The decrease in the SDAS and LS can be attributed to the decrease of the solute diffusivity in the liquid ahead of the solid/liquid interface during the growth of the dendrite and eutectic. This decrease is caused by the high magnetic field which can damp the convection and avoid its contributions to the diffusion.

  • 28. Mahmoudi, J.
    et al.
    Fredriksson, Hasse
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermal analysis of copper-tin alloys during rapid solidification2000In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 35, no 19, p. 4977-4987Article in journal (Refereed)
    Abstract [en]

    A series of solidification experiments using a mirror furnace and a levitation technique were performed on different Cu-Sn alloys. Cooling curves during solidification were registered using a thermocouple of type K connected to a data acquisition system. The undercooling, cooling rates of the liquid and of the solid state, solidification times and temperatures were evaluated from the curves. The samples were found to solidify far below the liquidus temperature. The cooling curves for different samples and alloys were simulated using a FEM solidification program. The heat transfer coefficient, heat of fusion and specific heat were evaluated. It was found that the calculated values of the heat of fusion were much lower than the tabulated ones. The calculated values of the specific heat in the solid state were also found to be much higher than those quoted in the literature, especially for the mirror furnace experiments. The effect of rapid cooling on the thermodynamic state and the solidification process of the alloys has been evaluated. The effect of cooling rate on the formation and condensation of vacancies is discussed. It is proposed that a large number of vacancies form during rapid solidification and that they condense during and after the solidification. The influence of these defects on the thermodynamics and solidification of the alloys has been evaluated.

  • 29.
    Malmberg, Kristofer J.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, Hiroyuki
    Institute of Multidisciplinary for Advanced Materials, Tohoku University, Sendai, Japan.
    Kitamura, Shin-ya
    Institute of Multidisciplinary for Advanced Materials, Tohoku University, Sendai, Japan.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nabeshima, Seiji
    Steel Research Laboratory, JFE Steel Corp., Kurashiki, Japan.
    Kishimoto, Yasuo
    Steel Research Laboratory, JFE Steel Corp., Kurashiki, Japan.
    Observed behavior of various oxide inclusions in front of a solidifying low-carbon steel shell2010In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 45, no 8, p. 2157-2164Article in journal (Refereed)
    Abstract [en]

    The engulfment and pushing (extrusion) of inclusions during solidification play an important role in the formation of a steel structure and, as a result, for the mechanical properties of the final steel product. The aim of this study is to gain knowledge about the behavior of non-metallic inclusions at the interface between a growing solid front and a liquid phase. The focus is on the effect of the titanium and titanium oxide content on the inclusions and the different phenomena, which occurs at the solid/liquid interface. This was studied in samples of low-carbon steels de-oxidized by different combinations of Al, Ca, and Ti. For this purpose, each metal sample of 0.19 g was melted at a temperature close to 1550 A degrees C in an argon atmosphere and solidified under different solidification rates. A direct observation of inclusion behavior during solidification was made using a confocal scanning laser microscope equipped with an infrared gold image furnace. The alloying elements in the sample varied between: C 0.002-0.044; Si 0.02-1.33; Mn 0.12-1.33; P 0.003-0.016; S 0.003-0.01; Al 0.002-0,033; Ni 0-0.28; Cr 0-0.25; Ti 0.008-0.065; Ca 0.0007-0.002; O 0.002-0.0114 and N 0.0028-0.0056 (mass%). Several types of inclusions with different morphologies were found within the sample. The morphology of the observed inclusions on the molten steel surface varied from round alumina and calcium-oxide-rich inclusion to needle-shaped titanium oxide-rich inclusions. The observed motions of the inclusions at the vicinity of the front of the solidifying steels were classified. At a low solidifying velocity and a small inclusion size, inclusions flowed away from the solidifying front. Furthermore, they also or got pushed a distance and thereafter flowed away from the interface. At a medium velocity and a slightly bigger size, inclusions tend to get pushed in front of the solidifying front. Another observation was that at a high velocity and a large particle size, inclusions tend to get engulfed or pushed and then engulfed by the progressing front. The relationship among the morphology, chemical composition of inclusions and the solidifying velocity is discussed in this article.

  • 30. Mao, Rui
    et al.
    Goutianos, Stergios
    Tu, Wei
    Meng, Nan
    Yang, Guang
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Peijs, Ton
    Comparison of fracture properties of cellulose nanopaper, printing paper and buckypaper2017In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, no 16, p. 9508-9519Article in journal (Refereed)
    Abstract [en]

    Cellulose nanopaper consists of a dense fibrous self-binding network composed of cellulose nanofibres connected by physical entanglements, hydrogen bonding, etc. Compared with conventional printing paper, cellulose nanopaper has higher strength and modulus because of stronger fibres and inter-fibre bonding. The aim of this paper is to investigate the fracture properties of cellulose nanopaper using double edge notch tensile tests on samples with different notch lengths. It was found that strength is insensitive to notch length. A cohesive zone model was used to describe the fracture behaviour of notched cellulose nanopaper. Fracture energy was extracted from the cohesive zone model and divided into an energy component consumed by damage in the material and a component related to pull-out or bridging of nanofibres between crack surfaces which was not facilitated due to the limited fibre lengths for the case of nanopapers. For comparison, printing paper which has longer fibres than nanopaper was tested and modelled to demonstrate the importance of fibre length. Buckypaper, a fibrous network made of carbon nanotubes connected through van der Waals forces and physical entanglements, was also investigated to elaborate on the influence of inter-fibre connections.

  • 31. Martinsson, Åsa
    et al.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Technology.
    Hydrogen depth profile in phosphorus-doped, oxygen-free copper after cathodic charging2012In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, no 19, p. 6768-6776Article in journal (Refereed)
    Abstract [en]

    Spent nuclear fuel, in Sweden, is planned to be put in 50-mm thick copper canisters and placed in 500-m depth in the bedrock. Depending on the conditions in the repository, an uptake of hydrogen in the copper may occur. It is therefore necessary to establish how a hydrogen uptake affects the microstructure in both the surface and the bulk. Phosphorus-doped, oxygen-free copper has been cathodically charged with hydrogen for up to 3 weeks. The amount of hydrogen as a function of the distance from the surface was measured by two methods: glow discharge optical emission spectrometry and melt extraction. The penetration of the increased hydrogen content was about 50 mu m. Extensive bubble formation took place during the charging. A model has been formulated for the diffusion of hydrogen into the copper, the bubble formation and growth. The model can describe the total amount of hydrogen, the number of bubbles and their sizes as a function of the distance from the surface. Bubbles close to the surface caused the surface to bulge due to the high hydrogen pressure. From the shape of the deformed surface, the maximum hydrogen pressure could be estimated with the help of stress analysis. The maximum pressure was found to be about 400 MPa, which is almost an order of magnitude larger than previously recorded values for electroless deposited copper.

  • 32. Mitchell, A
    et al.
    Freideriksson, Hasse
    KTH, Superseded Departments, Materials Science and Engineering.
    The electroslag remelting of high-nitrogen steels2004In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 39, no 24, p. 7275-7283Article in journal (Refereed)
    Abstract [en]

    Steels containing nitrogen at levels which are at or above the 1 Bar saturation solubility limit in the liquid at the liquidus temperature offer considerable metallurgical property advantages in many respects. For example, when nitrogen is used as a substitute for carbon in stainless grades, the alloys have superior corrosion properties especially in biomedical applications: nitrogen as a strengthening element in tool steels offers advantages in freedom from carbide particles which affect the polishability. Most of the steels grade of interest require electroslag remelting to control segregation without loss of nitrogen and the behaviour of nitrogen during this process is the subject of this work. It is concluded that the required process pressures are closely related to the alloy composition and that to prevent porosity in the product the ESR step must be carried out at an appropriate overpressure of either nitrogen or argon. The addition of nitrogen during ESR is also discussed and it is shown that this is possible only through solid additives.

  • 33.
    Mu, Wangzhong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Prediction of intragranular ferrite nucleation from TiO, TiN, and VN inclusions2016In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 51, no 4, p. 2168-2180Article in journal (Refereed)
    Abstract [en]

    The current study presents a method to calculate the critical diameters of TiO, TiN, and VN inclusions for intragranular ferrite (IGF) nucleation in steels. Based on the calculation results, it was noted that the critical diameters of TiO, TiN, and VN inclusions for IGF nucleation were 0.192, 0.355, and 0.810 μm. The calculation results agreed with the experiment data of a minimum inclusion size for IGF nucleation in the actual steel samples. Moreover, the effects of Mn, C, and S contents on the critical diameters of inclusions were investigated. It was found that the critical diameters of TiO, TiN, and VN inclusions increased with the increasing Mn and C contents. In addition, it was found that S does not have a direct effect on the critical diameters of TiO, TiN, and VN inclusions. However, the increasing S content led to an increased amount of MnS precipitation in the actual steels. This is negative, since MnS is ineffective nucleation site for IGF nucleation. When the amount of MnS increases in steels, the area fraction of IGF slightly decreases. This fact has been investigated by in situ observation experiments.

  • 34. Nanesa, Hadi Ghasemi
    et al.
    Jahazi, Mohammad
    Naraghi, Reza
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Martensitic transformation in AISI D2 tool steel during continuous cooling to 173 K2015In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 17, p. 5758-5768Article in journal (Refereed)
    Abstract [en]

    Martensitic transformation of AISI D2 tool steel continuously cooled from 1303 K to the cryogenic temperature of 173 K is investigated by dilatometry using 10 or 50 K s(-1) cooling rates. A 'typical' expansion takes place from the temperature and reaches a maximum at 325 K. However, an atypical behavior is observed below this temperature implying the activation of further martensitic transformation. A modification to existing equations is proposed, which allows for more accurate description of the kinetics of martensitic transformation. Scanning electron microscopic studies indicated the presence of plate and lath martensite for both cooling rates. Carbide precipitation takes place at the rate of 10 K s(-1) before the start of martensitic transformation while it was not observed when the 50 K s(-1) rate was used. Transmission electron microscopic studies revealed that the microstructure also contains a significant amount of nano-twinned martensite.

  • 35. Ndazi, B.
    et al.
    Tesha, J. V.
    Karlsson, Sigbritt
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Bisanda, E. T. N.
    Production of rice husks composites with Acacia mimosa tannin-based resin2006In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 41, no 21, p. 6978-6983Article in journal (Refereed)
    Abstract [en]

    Rice husks are amongst the typical agricultural residues, which are easily available in huge amounts. They have been considered as raw material for composites panels' production. However, the major hindrance in rice husks utilization for composite manufacture lies in the lack of direct interaction with most adhesive binders to form the anticipated interfacial bonds. Rice husks are highly siliceous and have poor resistance to alkaline and acidic conditions. Manufacture of rice husks composites panels having good interface bond is difficult and largely dependent on a proper understanding of the interaction between the husks and the binder. This paper presents and discusses results on the production of composites boards from a mixture of rice husks and wattle (Acacia mimosa) tannin based resin. The experimental results have shown that the 'as received rice husks' when blended with alkali-catalyzed tannin resin do not result in optimum composite panel properties. However, it was found that a slight physical modification of the rice husk particles by hammer-milling resulted in drastic improvements in the interfacial bond strength and stiffness of the composites panels from 0.041 MPa to 0.200 MPa and 1039 MPa to 1527 MPa, respectively.

  • 36. Neagu, Cristian R.
    et al.
    Gamstedt, Kristofer E.
    KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.).
    Modelling of effects of ultrastructural morphology on the hygroelastic properties of wood fibres2007In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 42, no 24, p. 10254-10274Article in journal (Refereed)
    Abstract [en]

    Wood fibres constitute the structural framework of e.g. wood, paper, board and composites, where stiffness and dimensional stability are of importance. An analytical modelling approach has been used for prediction of hygroelastic response, and assessment of the stresses in thick-walled cylinder models of wood fibres. A wood fibre was idealised as a multilayered hollow cylinder made of orthotropic material with helical orientation. The hygroelastic response of the layered assembly due to axisymmetric loading and moisture content changes was obtained by solving the corresponding boundary value problem of elasticity. A simple solution scheme based on the state space approach and the transfer matrix method was employed. This was combined with an analytical ultrastructural homogenisation method, used to link hygroelastic properties of constituent wood polymers to properties of each layer. Predicted hygroelastic response captured experimentally measured behaviour. Fibres that were constrained not to twist showed a stiffer response than fibres allowed twisting under uniaxial loading. It was also shown that the ultrastructure, i.e. the microfibril angle, will control the hygroexpansion in the same way as it controls the compliance of the cell wall. Qualitative failure trends comparable with experimental observations could be established with stress analysis and a simple plane-stress failure criterion.

  • 37.
    Prakobna, Kasinee
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Kisonen, Victor
    Abo Akad Univ, Lab Wood & Paper Chem, Johan Gadolin Proc Chem Ctr, SF-20500 Turku, Finland..
    Xu, Chunlin
    Abo Akad Univ, Lab Wood & Paper Chem, Johan Gadolin Proc Chem Ctr, SF-20500 Turku, Finland..
    Berglund, Lars A.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Strong reinforcing effects from galactoglucomannan hemicellulose on mechanical behavior of wet cellulose nanofiber gels2015In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 22, p. 7413-7423Article in journal (Refereed)
    Abstract [en]

    Softwood hemicelluloses could potentially be combined with cellulose and used in packaging materials. In the present study, galactoglucomannan (GGM) is adsorbed to wood cellulose nanofibers (CNF) and filtered and dried or hot-pressed to form nanocomposite films. The CNF/GGM fibril diameters are characterized by AFM, and the colloidal behavior by dynamic light scattering. Mechanical properties are measured in uniaxial tension for wet gels, dried films, and hot-pressed films. The role of GGM is particularly important for the wet gels. The wet gels of CNF/GGM exhibit remarkable improvement in mechanical properties. FE-SEM fractography and moisture sorption studies are carried out to interpret the results for hygromechanical properties. The present study shows that GGM may find use as a molecular scale cellulose binding agent, causing little sacrifice in mechanical properties and improving wet strength.

  • 38.
    Qadeer, Muhammad I.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Savage, Steven J.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Swedish Defence Research Agency (FOI), Linköping, Sweden .
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Rheological and dynamic mechanical properties of polymer-bonded magnets based on Sm2Co17 and polyamide-122014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 21, p. 7529-7538Article in journal (Refereed)
    Abstract [en]

    The rheological and dynamic mechanical properties of polymer-based composites of Sm2Co17 and polyamide-12 with different particle loadings, sizes, and surface treatments are reported. Sm2Co17 particles were surface-treated with three different silanes: 3-glycidoxy(propyl)trimethoxysilane, 3-amino(propyl)trimethoxysilane (APTMS), and methyltrimethoxysilane (MTMS). It was shown, for the composites with untreated particles, that the viscosity and storage modulus increased with increasing filler content (0-60 vol%) and decreasing filler particle size. In addition, the glass transition temperature increased significantly and the damping decreased with increasing filler content. Of the silanes, the MTMS, which yielded only a thin surface layer, had in general the least effect on the rheological properties of the composite. The composite containing the APTMS-coated filler showed the highest storage modulus. The results give new insights on how to prepare polymer-bonded magnets with optimal process conditions (rheology) and dynamic mechanical properties, by varying the amount of particles, their size, and surface treatment.

  • 39.
    Qadeer, Muhammad Ifran
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Savage, Steven J.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    High temperature magnetic properties of Sm-Co and Sm-Co/polyamide-12 materials: effects of temperature, particle size, and silanization2013In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 23, p. 8163-8170Article in journal (Refereed)
    Abstract [en]

    There is an increasing demand for polymer-bonded magnets (PBM) in high temperature applications. While most research deals with high temperature properties of NdFeB-PBM, only a few studies consider Sm-Co PBM. Therefore, this study, on the thermal and magnetic properties of Sm-Co alloy powders and blends of these with polyamide-12 (PA12), was undertaken. Since the Sm-Co powders were the product of ball milling, they contained a variety of shapes and sizes. Studies on size fractions of these showed that the thermal stability and magnetic properties were improved as the particle size increased. It was suggested that higher residual strains and smaller crystallite sizes in the small particles were responsible for a decrease in the thermal stability and magnetic properties. In addition, energy dispersive X-ray spectroscopy revealed that the oxygen content increased with decreasing particle size (larger specific surface area) and higher oxygen content was possibly also responsible for a decrease in the magnetic properties. It was shown that, in general, the surface modification by silanization, using (3-aminopropyl)trimethoxsilane, increased the saturation magnetization and remanence of both the particles and the Sm-Co/PA12 composite. The silanization also improved the thermal stability of the particles.

  • 40. Rekhi, S.
    et al.
    Saxena, S. K.
    Ahuja, R.
    Johansson, Börje
    Hu, J.
    Experimental and theoretical investigations on the compressibility of nanocrystalline nickel2001In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 36, no 19, p. 4719-4721Article in journal (Refereed)
  • 41.
    Saleemi, Mohsin
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Fiameni, S.
    Boldrini, S.
    Battiston, S.
    Famengo, A.
    Stingaciu, M.
    Johnsson, M.
    Muhammed, Mamoun
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM.
    Spark plasma sintering and thermoelectric evaluation of nanocrystalline magnesium silicide (Mg2Si)2013In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 48, no 5, p. 1940-1946Article in journal (Refereed)
    Abstract [en]

    Recently magnesium silicide (Mg2Si) has received great interest from thermoelectric (TE) society because of its non-toxicity, environmental friendliness, comparatively high abundance, and low production material cost as compared to other TE systems. It also exhibited promising transport properties, including high electrical conductivity and low thermal conductivity, which improved the overall TE performance (ZT). In this work, Mg2Si powder was obtained through high energy ball milling under inert atmosphere, starting from commercial magnesium silicide pieces (99.99 %, Alfa Aesar). To maintain fine microstructure of the powder, spark plasma sintering (SPS) process has been used for consolidation. The Mg2Si powder was filled in a graphite die to perform SPS and the influence of process parameters as temperature, heating rate, holding time and applied pressure on the microstructure, and densification of compacts were studied in detail. The aim of this study is to optimize SPS consolidation parameters for Mg2Si powder to achieve high density of compacts while maintaining the nanostructure. X-Ray diffraction (XRD) was utilized to investigate the crystalline phase of compacted samples and scanning and transmission electron microscopy (SEM & TEM) coupled with Energy-Dispersive X-ray Analysis (EDX) was used to evaluate the detailed microstructural and chemical composition, respectively. All sintered samples showed compaction density up to 98 %. Temperature dependent TE characteristics of SPS compacted Mg2Si as thermal conductivity, electrical resistivity, and Seebeck coefficient were measured over the temperature range of RT 600 A degrees C for samples processed at 750 A degrees C, reaching a final ZT of 0.14 at 600 A degrees C.

  • 42.
    Stevanic, Jasna S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Bergström, Elina Mabasa
    Gatenholm, Paul
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Salmén, Lennart
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Arabinoxylan/nanofibrillated cellulose composite films2012In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, no 18, p. 6724-6732Article in journal (Refereed)
    Abstract [en]

    There is an increasing interest in substituting petroleum based polymer films, for food packaging applications, with films based on renewable resources. In many of these applications, low oxygen permeability and low moisture uptake of films are required, as well as high enough strength and flexibility. For this purpose, rye arabinoxylan films reinforced with nanofibrillated cellulose was prepared and evaluated. A thorough mixing of the components resulted in uniform films. Mechanical, thermal, structural, moisture sorption and oxygen barrier characteristics of such films are reported here. Reinforcement of arabinoxylan with nanofibrillated cellulose affected the properties of the films positively. A decrease in moisture sorption of the films, as well as an increase in stiffness, strength and flexibility of the films were shown. From these results and dynamic FTIR spectra, a strong coupling between reinforcing cellulose and arabinoxylan matrix was concluded. Oxygen barrier properties were equal or better as compared to the neat rye arabinoxylan film. In general, the high nanofibrillated cellulose containing composite film, i.e. 75 % NFC, showed the best properties.

  • 43.
    Stevanic, Jasna S.
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Mikkonen, Kirsi S.
    Xu, Chunlin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Tenkanen, Maija
    Berglund, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Biocomposites. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Salmén, Lennart
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wood cell wall mimicking for composite films of spruce nanofibrillated cellulose with spruce galactoglucomannan and arabinoglucuronoxylan2014In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 49, no 14, p. 5043-5055Article in journal (Refereed)
    Abstract [en]

    Two hemicelluloses (HCs), galactoglucomannan (GGM) and arabinoglucuronoxylan (AGX), and nanofibrillated cellulose (NFC) were isolated from spruce wood and used for the preparation of composite films containing high amounts of cellulose, i.e. 85 and 80 wt% of NFC, respectively. The films were prepared in two ways: (i) by the pre-sorption of HCs on NFC and (ii) by the mixing of components in the usual way. Pre-sorption was applied in an attempt to mimic the carbohydrate biosynthesis pattern during wood cell wall development, where HCs were deposited on the cellulose fibrils prior to lignification taking place. It was assumed that pre-sorption would result in a better film-forming as well as stronger and denser composite films. The mechanical, thermal, structural, moisture sorption and oxygen barrier characteristics of such composite films were tested in order to examine whether the performance of composite films prepared by pre-sorption was better, when compared to the performance of composite films prepared by mixing. The performance of composite films was also tested with respect to the HCs used. All the films showed quite similar barrier and mechanical properties. In general, stiff, strong and quite ductile films were produced. The moisture sorption of the films was comparably low. The oxygen barrier properties of the films were in the range of commercially used poly ethylene vinyl alcohol films. However, the pre-sorption procedure for the preparation of composite films resulted in no additional improvement in the performance of the films compared to the corresponding composite films that had been prepared using the mixing process. Almost certainly, the applied mixing process led to an optimal mixing of components for the film performance achieved. The GGM contributed to a somewhat better film performance than the AGX did. Indications were observed for stronger interactions between the GGM and NFC than that for the AGX and NFC.

  • 44.
    Sui, Fangfei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sandström, Rolf
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Basic modelling of tertiary creep of copper2018In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 53, no 9, p. 6850-6863Article in journal (Refereed)
    Abstract [en]

    Mechanisms that are associated with acceleration of the creep rate in the tertiary stage such as microstructure degradation, cavitation, necking instability and recovery have been known for a long time. Numerous empirical models for tertiary creep exist in the literature, not least to describe the development of creep damage, which is vital for understanding creep rupture. Unfortunately, these models almost invariably involve parameters that are not accurately known and have to be fitted to experimental data. Basic models that take all the relevant mechanisms into account which makes them predictive have been missing. Only recently, quantitative basic models have been developed for the recovery of the dislocation structure during tertiary creep and for the formation and growth of creep cavities. These models are employed in the present paper to compute the creep strain versus time curves for copper including tertiary creep without the use of any adjustable parameters. A satisfactory representation of observed tertiary creep has been achieved. In addition, the role of necking is analysed with both uniaxial and multiaxial methods.

  • 45.
    Sun, Weiwei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Luo, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Role of correlation and relativistic effects in MAX phases2012In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 47, no 21, p. 7615-7620Article in journal (Refereed)
    Abstract [en]

    We have performed the ab initio calculations to study the role of correlation and relativistic effects in MAX phases. As of now, there are more than 50 MAX phases reported in the literature; however, we have chosen two MAX phases, namely Cr2AlC and Ta2AlC, as representatives of MAX phases for our study as they are very poorly described from calculation point of view. Our results show that correlation effects are very important to understand the electronic and mechanical properties of Cr2AlC, but not so important for Ta2AlC. We have also studied the relativistic effects on Ta2AlC and our calculations show that going from scalar to fully relativistic effects does not have any significant effect on the electronic and mechanical properties of Ta2AlC. We conclude that Ta2AlC is a weakly correlated system, whereas Cr2AlC is a strongly correlated system. Further experiments are needed to explain the discrepancy between theory and experiments.

  • 46. Thuvander, F.
    et al.
    Berglund, Lars A.
    In situ observations of fracture mechanisms for radial cracks in wood2000In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 35, no 24, p. 6277-6283Article in journal (Refereed)
    Abstract [en]

    This paper presents the findings of work carried out to describe the micromechanisms of radial crack growth in wood. TR and TL cracks are both radial cracks but TR grows radially and TL longitudinally. TR cracks are known to show higher fracture toughness than TL cracks. The TR fracture surfaces also indicate a more tortuous crack path. Since the reason for this is unclear, details of the TR crack growth mechanisms in green Pinus sylvestris L were studied. This was done by in-situ optical microscopy as the crack was cutting through alternating layers of soft earlywood and stiff latewood. At the scale of individual cells, the crack tip advanced by separating cell walls at the middle lamella in a splitting or peeling mode. At the scale of growth rings, stick-slip type of crack growth was observed and new crack planes were often formed. The stress distribution in a material with alternating stiff and soft layers is causing this. This stress distribution also contributes to the tendency for inclined cracks to deviate in the radial direction. For interpretation of fracture mechanisms, the importance of scale interaction and the combined influences of microstructure and stress state are emphasized.

  • 47. Thuvander, F.
    et al.
    Sjodahl, M.
    Berglund, Lars A.
    Measurements of crack tip strain field in wood at the scale of growth rings2000In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 35, no 24, p. 6267-6275Article in journal (Refereed)
    Abstract [en]

    The fracture mechanisms of wood have often been interpreted on the scale of cell walls. Although this scale is important, the scale of growth rings needs to be considered in the same context. In the present study, the crack tip strain field of radial TR cracks at the scale of growth rings is measured by electronic speckle photography. The methodology is discussed in detail as well as the data reduction scheme. The tip is in the earlywood layer and the crack plane of the TR crack is perpendicular to the stiffer latewood layer. Increasing opening mode load is applied in-situ as the crack is observed by reflected light optical microscopy. Strains are measured on direct images of the microstucture. In contrast to some other methodologies, this allows direct correlation between strain field and microstructure. In the softer earlywood, tangential strains extend considerable distances in the tangential direction. Due to the stiff latewood, the strain is heavily constrained in the radial direction. This nature of the local strain field has been largely neglected, despite its obuius significance to TR crack growth mechanisms.

  • 48.
    Trybula, Marcela E.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Polish Acad Sci, Inst Met & Mat Sci, PL-30059 Krakow, Poland..
    Szafranski, Przemyslaw W.
    Jagiellonian Univ, Coll Med, PL-30688 Krakow, Poland..
    Korzhavyi, Pavel A.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Structure and chemistry of liquid Al-Cu alloys: molecular dynamics study versus thermodynamics-based modelling2018In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 53, no 11, p. 8285-8301Article in journal (Refereed)
    Abstract [en]

    Classical molecular dynamics simulations, employing a modified embedded atom model (MEAM) parametrization recently developed by Trybula, have been performed and combined with thermodynamics-based modelling for weakly interacting compound-forming molten alloys, to investigate the structure and chemistry of liquid Al-Cu alloys over a broad Cu concentration range. The compound-forming model (CFM) based on experimental thermodynamic data revealed the importance of the Al2Cu "associate" in the determination of transport properties such as diffusion and viscosity as well as confirmation of the compound formation ability with regard to the available experimental data. Adequately to this fact, molecular dynamics simulation results showed strong evidence of deviation from regular metallic solution resulting from a preponderance of chemical short-range ordering, expressed by Warren-Cowley parameter and increasing abundance of icosahedral motifs with increasing Cu content. In addition, their strong impact on mass transport properties as well as the excess entropy has been detected which exhibits nonlinear compositional behaviour. Thus, we find that the Stokes-Einstein relation is unsuitable for atom transport properties determination at investigated Cu concentration range, while the Green-Kubo formalism can fully account for the experimentally observed physical phenomena. We obtain a compact and compatible view onto the structure and chemical behaviour, including atom kinetics and thermodynamics, of Al-Cu liquid alloys, which allowed us to find another hard-sphere-like metallic system in which transport properties and thermodynamics are strongly affected by packing effects. The hybrid approach presented herein gave a broader and deeper look into the liquid state of the Al-Cu alloys being missing in the literature.

  • 49. Vahtikari, Katja
    et al.
    Rautkari, Lauri
    Noponen, Tuula
    Lillqvist (nee Laine), Kristiina
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Materials.
    Hughes, Mark
    The influence of extractives on the sorption characteristics of Scots pine (Pinus sylvestris L.)2017In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, no 18, p. 10840-10852Article in journal (Refereed)
    Abstract [en]

    The sorption behaviour of extracted and un-extracted Scots pine (Pinus sylvestris L.) heartwood was analysed using dynamic vapour sorption apparatus. In addition to the sorption isotherm and hysteresis, the moisture increments and decrements were determined as well as the rate of sorption. Parallel exponential kinetics model was used for further analysis. The effect of cyclic humidity loading on the sorption characteristics was studied by exposing samples to ten repeated sorption cycles and by determining the amount of accessible hydroxyl (OH) groups before and after the cyclic humidity loading. Removal of extractives led to an increase in EMC both in adsorption and in desorption. Hysteresis decreased due to the removal of extractives. Cyclic humidity loading reduced the sorptive capacity of wood material for both extracted and un-extracted wood, but was more pronounced in un-extracted wood. However, despite the decrease in the sorptive capacity, the amount of accessible OH groups increased after ten repeated dry-humid cycles.

  • 50. Woldegiorgis, A.
    et al.
    Jansson, K.
    Roeraade, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Analytical Chemistry.
    Fabrication of silica nano wires on the internal perimeter of narrow bore fused silicia tubing by non-isothermal etching2005In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 40, no 3, p. 583-589Article in journal (Refereed)
    Abstract [en]

    An method for fabrication of long silica nano wires is presented. The nano structured material is an integral part of the inner surface of narrow bore fused silica capillary tubing. The wire preparation method is based on a hydrothermal action and decomposition of 2-chloro-1,1,2-trifluoroethyl methyl ether at elevated temperature. In our previous work, reproducible nano wire outgrowth could only be accomplished in capillaries with an inner diameter less than 10 mum [1], and the centre of the capillary lumen remained free of wires. In the present article we report on nano wire outgrowth in capillaries with larger inner diameters. These wires are entangled via carbon nucleating particles and stretch across the entire lumen of the capillary. The long nano wire outgrowth was induced by a time dependent, non isothermal etching of the capillaries. Suggested mechanisms for the growth process are discussed.

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