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  • 1.
    Agthe, Michael
    et al.
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Wetterskog, Erik
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Salazar-Alvarez, German
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Bergström, Lennart Magnus
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Dynamic growth modes of ordered arrays and mesocrystals during drop-casting of iron oxide nanocubes2014In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 16, no 8, p. 1443-1450Article in journal (Refereed)
    Abstract [en]

    The growth modes of self-assembled mesocrystals and ordered arrays from dispersions of iron oxide nanocubes with a mean edge length of 9.6 nm during controlled solvent removal have been investigated with a combination of visible light video microscopy, atomic force microscopy and scanning electron microscopy. Mesocrystals with translational and orientational order of sizes up to 10 μm are formed spontaneously during the final, diffusion-controlled, drop-casting stage when the liquid film is very thin and the particle concentration is high. Convection-driven deposition of ordered nanocube arrays at the edge of the drying droplet is a manifestation of the so called coffee-ring effect. Dendritic growth or fingering of rapidly growing arrays of ordered nanocubes could also be observed in a transition regime as the growth front moves from the initial three-phase contact line towards the centre of the original droplet.

  • 2.
    Aguilar, Wilson
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Cardenas, Edgar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Dendritic growth of NBA-ZSM-5In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Article in journal (Other academic)
    Abstract [en]

    Crystallization of ZSM-5 zeolite from a gel using n-butylamine as structure-directing agent was studied. Extreme high-resolution transmission and scanning electron microscopy showed the presence of dendritic features that are present at the crystal surface during most of the reaction time that become smoother towards completion of the crystallization. In addition, a web that likely stems from the gel, comprised of alumina-rich nanoparticles between the dendrites at the surface of the crystals was also identified. When the gel is not in direct contact with the crystal surface, dendrites and the web are not observed, and the crystals grow faster. Thus, the alumina-rich web retards the crystal growth and cause the formation of dendritic features.

  • 3.
    Aguilar, Wilson
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Garcia, Gustavo
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of ZSM-52014In: SpringerPlus, E-ISSN 2193-1801, Vol. 3, no 1Article in journal (Refereed)
    Abstract [en]

    Inexpensive raw materials have been used to prepare ZSM-5 zeolites with SiO2/Al2O3 molar ratios in the range 20 - 40. Kaolin or Bolivian diatomaceous earth was used as aluminosilicate raw materials and sodium hydroxide and n-butylamine were used as mineralizing agents and template. Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO2/Al2O3 ratios and to reduce the amount of iron and other impurities. After mixing the components and aging, hydrothermal treatment was carried out and the products were recovered The results clearly show for the first time that well-crystallized ZSM-5 can be directly prepared from leached metakaolin or leached diatomaceous earth using sodium hydroxide and n-butylamine as mineralizing agents and template under appropriate synthesis conditions. A longer induction time prior to crystallization was observed for reaction mixtures prepared from leached diatomaceous earth, probably due to slower digestion of the fossilized diatom skeletons as compared with that for microporous leached metakaolin. The use of leached diatomaceous earth allowed higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of Mordenite formed, which was related to the high calcium content of diatomaceous earth. Another considerable advantage of diatomaceous earth over kaolin is that diatomaceous earth does not require heat treatment at high temperature for metakaolinization.

  • 4.
    Aguilar-Mamani, Wilson
    et al.
    Department of Chemistry, Faculty of Science and Technology, San Simon University, UMSS, Cochabamba.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Solution-mediated growth of NBA-ZSM-5 crystals retarded by gel entrapment2018In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 487, p. 57-64Article in journal (Refereed)
    Abstract [en]

    The synthesis of flat tablet-shaped ZSM-5 crystals from a gel using metakaolin as aluminosilicate source and n-butyl amine as structure directing agent was investigated. The evolution inside the solid phase was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry and mass spectrometry. A kinetic study indicated that the nucleation of the majority crystals occurred concurrently with the formation of the gel upon heating the starting liquid suspension. Microstructural evidences undeniably showed that the gel precipitated on ZSM-5 crystals and mineral impurities originating from kaolin. As a result, crystal growth was retarded by gel entrapment, as indicated by the configuration and morphology of the embedded crystals. The results presented herein are harmonized with a solution-mediated nucleation and growth mechanism. Our observations differ from the autocatalytic model that suggests that the nuclei rest inside the gel until released when the gel is consumed. Our results show instead that it is crystals that formed in an early stage before entrapment inside the gel that rest inside the gel until exposed at the gel surface. These results illustrate the limitation of the classical method used in the field to determine nucleation profiles when the crystals become trapped inside the gel.

  • 5.
    Aguilar-Mamani, Wilson
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Department of Chemistry, Faculty of Science and Technology, San Simon University, Cochabamba, Bolivia.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Internal structure of a gel leading to NBA-ZSM-5 single crystals2018In: Journal of porous materials, ISSN 1380-2224, E-ISSN 1573-4854, Vol. 25, no 6, p. 1551-1559Article in journal (Refereed)
    Abstract [en]

    Porous gel structures are formed during the synthesis of the zeolite ZSM-5 due to the reaction between a source of aluminosilicate, sodium hydroxide, water and a structure directing agent, such as e.g. tetrapropylammonium (TPA) or n-butylamine (NBA). In the present work, the formation of the gel in a heterogeneous system leading to the crystallization of NBA-ZSM-5 zeolite from leached metakaolin was studied extensively. The solid and liquid phases obtained after separation were analyzed by inductively coupled plasma sector field mass spectrometry, dynamic light scattering, extreme high resolution-scanning electron microscopy, energy dispersive spectroscopy, high resolution-transmission electron microscopy, X-ray diffraction and nitrogen gas adsorption. The main gel phase formed after hydrothermal treatment exhibited a sponge-like structure resembling those forming in (Na, TPA)-ZSM-5-based systems. For the first time, the walls of the main gel were shown to be inhomogenous and to possess a biphasic internal structure consisting of a mesoporous skeleton of aluminosilicate nanoparticles embedded in a silicate-rich soluble matrix of soft matter. The data presented in this paper is of primary importance to understand the mechanism by which the gel is consumed and contributes to the growth process of the zeolite crystals.

  • 6.
    Akhtar, Farid
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bergström, Lennart M.
    Department of Materials and Environmental Chemistry, Stockholm University.
    All-Zeolite Membranes2010Conference paper (Refereed)
  • 7.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ikumapayi, Fatai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gunneriusson, Lars
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2011Conference paper (Other academic)
  • 8.
    Antzutkin, Oleg
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Kota, Hanumantha Rao
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ikumapayi, Fatai
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Johansson, Björn
    New Boliden AB.
    Berggren, Andreas
    New Boliden AB.
    Larsson, Anna-Carin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, Seija
    LKAB.
    Interactions in multi-component mineral systems2010Conference paper (Other academic)
  • 9.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Forsmo, S.P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Consideration of X-ray microtomography to quantitatively determine the size distribution of bubble cavities in iron ore pellets2013In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 233, p. 312-318Article in journal (Refereed)
    Abstract [en]

    X-ray microtomography data of iron ore green pellets of approx. 12 mm in diameter were recorded using a commercial instrument. The reconstructed volume after thresholding represented a unique dataset consisting of a three-dimensional distribution of equiaxed objects corresponding to bubble cavities. This dataset was used to successfully validate a stereological method to determine the size distribution of spherical objects dispersed in a volume. This was achieved by investigating only a few cross-sectional images of this volume and measuring the profiles left by these objects in the cross-sectional images. Excellent agreement was observed between the size distribution of the bubble cavities obtained by directly classifying their size in the reconstructed volume and that estimated by applying the aforementioned stereological method to eight cross-sectional images of the reconstructed volume. Subsequently, we discuss the possibility of calibrating X-ray tomography data quantitatively using the size distribution of the bubble cavities as a figure of merit and the results obtained by applying the stereological method to SEM images as reference data. This was justified by considering the validity of the stereological method demonstrated by tomography, the accurate thresholding made possible by back-scattered electron imaging and the solid reproducibility of the results obtained by SEM. Using different threshold values for binarization of the X-ray microtomography data and comparing the results to those obtained by SEM, we found that X-ray microtomography can be used after proper calibration against SEM data to measure the total porosity of the bubble cavities but can only provide a rough estimate of the median diameter because of the limited resolution achieved in this study.

  • 10.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, S.P.E.
    LKAB.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Quantitative image analysis of bubble cavities in iron ore green pellets2011In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 214, no 3, p. 306-312Article in journal (Refereed)
    Abstract [en]

    Scanning electron microscopy and image analysis was used for quantitative analysis of bubble cavities in iron ore green pellets. Two types of pellets prepared with and without addition of flotation reagent prior to balling were studied. The bubble cavity porosity amounted to 2.8% in the pellets prepared without addition of flotation reagent prior to balling. When flotation reagent was added prior to balling, the bubble cavity porosity increased by a factor of 2.4 and the median bubble diameter was decreased slightly. It was also shown that mercury intrusion porosimetry is not suitable for determination of the distribution of bubble cavities. Finally, our data suggested that the difference in total porosity determined by mercury intrusion porosimetry and pycnometry between the two types of pellets was due to the bubble cavities.

  • 11.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, S.P.E.
    LKAB Research and Development.
    Forsberg, Fredrik
    Air bubbles in iron ore green pellets due to flotation reagent: characterization by scanning electron microscopy and X-ray microtomography2011Conference paper (Other academic)
  • 12.
    Bhuiyan, Iftekhar Uddin
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Schröppel, Birgit
    Natural and Medical Sciences Institute (NMI), University of Tübingen.
    Kaech, Andres
    Center for Microscopy and Image Analysis, University of Zurich.
    Dobryden, Illia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Forsmo, Seija P.E.
    LKAB, Research & Development, 983 81 Malmberget.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Microstructure of Bentonite in Iron Ore Green Pellets2014In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 20, no 1, p. 33-41Article in journal (Refereed)
    Abstract [en]

    Sodium-activated calcium bentonite is used as a binder in iron ore pellets and is known to increase strength of both wet and dry iron ore green pellets. In this article, the microstructure of bentonite in magnetite pellets is revealed for the first time using scanning electron microscopy. The microstructure of bentonite in wet and dry iron ore pellets, as well as in distilled water, was imaged by various imaging techniques (e.g., imaging at low voltage with monochromatic and decelerated beam or low loss backscattered electrons) and cryogenic methods (i.e., high pressure freezing and plunge freezing in liquid ethane). In wet iron ore green pellets, clay tactoids (stacks of parallel primary clay platelets) were very well dispersed and formed a voluminous network occupying the space available between mineral particles. When the pellet was dried, bentonite was drawn to the contact points between the particles and formed solid bridges, which impart strength to the solid compact.

  • 13.
    Bleken, Bjørn Tore L.
    et al.
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Wragg, David Stephen
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Arstad, Bjørnar
    SINTEF Materials and Chemistry, Blindern.
    Gunnæs, Anette Eleonora
    Department of Physics, University of Oslo FERMiO.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Helveg, Stig
    Haldor Topsøe A/S.
    Lundegaard, Lars Fahl
    Haldor Topsøe A/S.
    Beato, Pablo
    Haldor Topsøe A/S.
    Bordiga, Silvia
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Olsbye, Unni
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Svelle, Stian
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Lillerud, Karl Petter
    Department of Chemistry, InGAP Center for Research-based Innovation, University of Oslo Blindern.
    Unit cell thick nanosheets of zeolite H-ZSM-5: Structure and activity2013In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 56, no 9-10, p. 558-566Article in journal (Refereed)
    Abstract [en]

    nosheets of zeolite H-ZSM-5 were synthesized and characterized by X-ray diffraction, transmission electron microscopy (TEM), N2- physisorption, FT-IR spectroscopy, 27Al and 29Si MAS NMR spectroscopy in addition to catalytic testing in conversion of methanol to hydrocarbons (MTH). It was found that Rietveld analysis, involving anisotropic broadening parameters, gave average crystallite dimensions in good agreement with TEM images. The selectivities in MTH is intact in the mesoporous nanosheet H-ZSM-5 with the largest difference being a higher C3/C2 ratio compared to regular H-ZSM-5.

  • 14.
    Carabante, Ivan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Kumpiene, Jurate
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Fredriksson, Andreas
    Mining Technology R and D, LKAB Kiruna Mine.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Reutilization of porous sintered hematite bodies as effective adsorbents for arsenic(V) removal from water2014In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 53, no 32, p. 12689-12696Article in journal (Refereed)
    Abstract [en]

    A method was developed to enhance the arsenic adsorption capacity of porous bodies of sintered hematite. The method comprised the formation of a coating of 1 wt % iron oxide nanoparticles on the raw material. The nanoparticles showed two distinct habits: spherical habit, likely ferrihydrite, and acicular habit, likely goethite and/or akaganéite. The specific surface area of the hematite raw material increased from 0.5 to 3.75 m2/g, and the adsorption capacity increased from negligible to 0.65 mg of [As]/g as calculated from equilibrium and breakthrough adsorption data. Equilibrium adsorption data of arsenate on the adsorbent from a solution at pH 5 followed the Langmuir model, while breakthrough adsorption data for a 500 μg/L arsenate solution at pH 5 followed the Thomas model. The adsorbed arsenic could be desorbed using distilled water at pH 12. These results show the potential for the reutilization of waste products comprising coarse hematite bodies as adsorbents.

  • 15.
    Cardenas, Edgar
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Aguilar, Wilson
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tai, Cheuk-Wai
    Department of Environmental and Materials Chemistry, Stockholm Unversity.
    Cabrera, Saul
    Chemistry Research Institute, San Andres Mayor University.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Microstructural evolution of condensed aggregates during the crystallization of ZSM-5Manuscript (preprint) (Other academic)
    Abstract [en]

    In the present work, the microstructural evolution of precursors of (TPA, Na)-ZSM-5, previously described as condensed aggregates (CAs) (Ren, 2012), was studied carefully. It was observed that the CAs first comprise a core of nanocrystals and that the core is enveloped by a shell of amorphous gel phase.  During crystallization, the amorphous shell surrounding the core is converted to ZSM-5 crystals that grow to a film surrounding the core. The crystals in the film grow competitively with nutrients provided by the liquid phase surrounding the CAs, while the nanocrystals in the core show little or no signs of growth.

  • 16.
    Cardenas, Edgar
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Aguilar, Wilson
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Zhou, Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of the internal structure of the gel on Al-zoning in NBA-ZSM-5 crystalsIn: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093Article in journal (Other academic)
    Abstract [en]

    The crystallization of ZSM-5 from a gel comprising n-butylamine as structure directing agent was investigated. The samples were characterized by X-ray diffraction, nitrogen gas adsorption, extreme high-resolution transmission and scanning electron microscopy, and energy dispersive spectroscopy. The gel was found to be composed by a silica-rich matrix embedded in a skeleton of alumina-rich nanoparticles. During growth of the crystals, the silica-rich matrix is consumed first, and an increasing fraction of the alumina-rich nanoparticles are utilized later in the growth process. This leads to a non-uniform consumption of the gel walls during crystal growth. Consequently, the Si/Al ratio of the gel is steadily decreasing, which is accompanied by a corresponding decrease in the Si/Al ratio from the center to the outer surface of the crystals, i.e. Al-zoning of the ZSM-5 crystals.

  • 17.
    Engström, Andreas
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Córdoba, J.M.
    Instituto de Ciencia de Materiales de Sevilla, Código del Centro.
    Tegman, Ragnar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Synthesis of a TiCN – SiC polyhedron and elongated crystals nanopowder at low nitrogen concentration2012In: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 81, p. 148-150Article in journal (Refereed)
    Abstract [en]

    At room temperature diluted TiCl4 and CCl4 were reduced by sodium particles and mixed with a polycarbomethylsilane (PCS) solution to yield a precursor. It was dried and subsequently annealed at 1300 °C, 1400 °C and 1450 °C in a tube furnace using argon with 10 ppm N2. After the 1450 °C annealing a nanocrystalline powder of TiC0.5 N0.5–SiC polyhedron and elongated crystals was obtained. At the low nitrogen concentration during annealing a gradual nitration is proposed. It is promoted by carbon gaseous species, precursor oxidation, a sufficient temperature and a summarised nitrogen surplus compared to the titanium and carbon amount.

  • 18.
    Garcia, Gustavo
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Aguilar, Wilson
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Carabante, Ivan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Cabrera, Saúl
    Chemistry Research Institute IIQ, San Andres Mayor University UMSA, La Paz.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Preparation of zeolite A with excellent optical properties from clay2015In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 619, p. 771-777Article in journal (Refereed)
    Abstract [en]

    Discoloration of zeolite A powder is a common problem when natural raw materials such as kaolin clay are used because of the formation of colored iron compounds. In this study, we report on a novel method to produce zeolite A with excellent optical properties, from clays. The brightness is as high as 94.5 and the yellowness is as low as 3.0. The product is comprised of intergrown zeolite A crystals with cubic habit and a length ranging between 0.5 and 2 μm. Good optical properties are obtained when the raw material contains magnesium, as some natural raw materials do, or alternatively, when a magnesium compound is added to the raw material. Magnesium probably forces iron inside colorless extraneous magnesium aluminosilicate compounds. This simple process appears very promising for the preparation of zeolite A with good optical properties from inexpensive natural raw materials.

  • 19.
    Garcia, Gustavo
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Solid State and Theoretical Chemistry, Chemistry Research Institute, San Andres Mayor University.
    Cabrera, Saúl
    Solid State and Theoretical Chemistry, Chemistry Research Institute, San Andres Mayor University, University Campus.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Selective synthesis of FAU-type zeolites2018In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 489, p. 36-41Article in journal (Refereed)
    Abstract [en]

    In the present work, parameters influencing the selectivity of the synthesis of FAU-zeolites from diatomite were studied. The final products after varying synthesis time were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and gas adsorption. It was found that high concentrations of NaCl could completely inhibit the formation of zeolite P, which otherwise usually forms as soon as maximum FAU crystallinity is reached. In the presence of NaCl, the FAU crystals were stable for extended time after completed crystallization of FAU before formation of sodalite. It was also found that addition of NaCl barely changed the crystallization kinetics of FAU zeolite and only reduced the final FAU particle size and SiO2/Al2O3 ratio slightly. Other salts containing either Na or Cl were also investigated. Our results suggest that there is a synergistic effect between Na+ and Cl-. This is attributed to the formation of (Na4Cl)3+ clusters that stabilize the sodalite cages. This new finding may be used to increase the selectivity of syntheses leading to FAU-zeolites and avoid the formation of undesirable by-products, especially if impure natural sources of aluminosilica are used.

  • 20.
    Garcia, Gustavo
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Cardenas, Edgar
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Cabrera, Saúl
    Chemistry Research Institute IIQ, San Andres Mayor University UMSA, La Paz.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Synthesis of zeolite Y from diatomite as silica source2016In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 219, p. 29-37Article in journal (Refereed)
    Abstract [en]

    Bolivian diatomite was successfully used as a silica source for the synthesis of zeolite Y. Prior to synthesis, the diatomite was leached with sulfuric acid to remove impurities and aluminum sulfate was used as an aluminum source. The raw materials were reacted hydrothermally at 100 °C in water with sodium hydroxide and different Na2O/SiO2 ratios were investigated. The final products were characterized by scanning electron microscopy, X-ray diffraction, gas adsorption and inductively coupled plasma-atomic emission spectroscopy. Diatomites originating from different locations and therefore containing different types and amounts of minerals and clays as impurities were investigated. After optimization of synthesis time, zeolite Y with low SiO2/Al2O3 ratio (3.0–3.9) was obtained at a high yield for high alkalinity conditions (Na2O/SiO2 = 0.85–2.0). Lower Na2O/SiO2 ratios resulted in incomplete dissolution of diatomite and lower yield. Nevertheless, decreasing alkalinity resulted in a steady increase of the SiO2/Al2O3 ratio in zeolite Y. Consequently, it was possible to synthesize almost pure zeolite Y with a SiO2/Al2O3 ratio of 5.3 for a Na2O/SiO2 ratio of 0.6, albeit at a low yield. In this respect, diatomite enables the synthesis of high silica zeolite Y and behaves similarly to colloidal silica in traditional syntheses, with both sources of silica having in common a high degree of polymerization. Interestingly, the presence of minerals and clays in the starting diatomite had marginal effects on the outcome of the synthesis. However, their dissolution resulted in presence of calcium and magnesium in the zeolite Y crystals. Finally, overrun of all investigated compositions resulted in the formation of zeolite P nucleating and growing onto dissolving zeolite Y crystals, which was shown to be triggered when aluminum was completely depleted at high alkalinity

  • 21.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanoporous membranes with cellulose nanocrystals as functional entity in chitosan: removal of dyes from water2014In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 112, p. 668-676Article in journal (Refereed)
    Abstract [en]

    Fully biobased composite membranes for water purification were fabricated with cellulose nanocrystals (CNCs) as functional entities in chitosan matrix via freeze-drying process followed by compacting. The chitosan (10 wt%) bound the CNCs in a stable and nanoporous membrane structure with thickness of 250-270 μm, which was further stabilized by cross-linking with gluteraldehyde vapors. Scanning electron microscopy (SEM) studies revealed well-individualized CNCs embedded in a matrix of chitosan. Brunauer, Emmett and Teller (BET) measurements showed that the membranes were nanoporous with pores in the range of 13-10 nm. In spite of the low water flux (64 L m-2 h-1), the membranes successfully removed 98%, 84% and 70% respectively of positively charged dyes like Victoria Blue 2B, Methyl Violet 2B and Rhodamine 6G, after a contact time of 24 h. The removal of dyes was expected to be driven by the electrostatic attraction between negatively charged CNCs and the positively charged dyes.

  • 22.
    Karimi, Somayeh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Yu, Liang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Khodadadi, Abbas Ali
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Mortazavi, Yadollah
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Esmaeili, Mohammad
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    A simple method for blocking defects in zeolite membranes2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 489, p. 270-274Article in journal (Refereed)
    Abstract [en]

    The abatement of defects in zeolite membranes is essential for achieving high selectivity. In the present work, a simple and effective method for blocking defects in ultra-thin (ca. 0.5 μm) MFI zeolite membranes has been developed. The method is based on deposition of an ultra-thin (∼15 nm) layer of amorphous silica on the top surface of the membrane. Permporometry data indicated that the amount of defects, especially defects larger than 4 nm, in the membranes was significantly reduced after the modification. In mixture separation experiments, the CO2/H2 separation factor increased dramatically after blocking the defects in a defective membrane that was selected for the experiments. For instance, at 263 K and 9 bar feed pressure, the CO2/H2 separation factor increased from 8.5 to 36 after modification of the membrane, whereas the CO2 flux only decreased by ca. 40%.

  • 23.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Characterization of flow-through micropores in MFI membranes by permporometry2012In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 417-418, p. 183-192Article in journal (Refereed)
    Abstract [en]

    Permporometry was used for the first time to characterize flow-through micropore defects down to 0.7 nm in size in MFI zeolite membranes. Helium was used as the non-adsorbing gas and n-hexane or benzene was used as the adsorbate. The helium flow through zeolite pores was estimated using percolation theory and the remaining flow was assigned to flow-through defects. The area distribution of flow-through defects was estimated from the data using a simple model and similar results were obtained using both adsorbates. The total area of defects determined using n-hexane as the adsorbate was as low as about 0.7% of the membrane area and defects with a width below 1 nm constituted 97% of the total defect area for the best membrane. The permporometry results were supported by n-hexane/1,3,5-trimethylbenzene separation experiments. The permporometry data were also consistent with HR-SEM observations indicating the presence of narrow open grain boundaries, and absence of large cracks and pinholes

  • 24.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Characterization of small defects in MFI membranes by permporometry, separation experiments and XHR-SEM2010Conference paper (Refereed)
  • 25.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ye, Pengcheng
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Zhou, Han
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    An experimental study of micropore defects in MFI membranes2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 186, p. 194-200Article in journal (Refereed)
    Abstract [en]

    In the present work, two ultra-thin MFI membranes, prepared using hydroxide and fluoride ions as mineralizing agents, respectively, were carefully examined by permporometry. The amount of micropore defects, as determined by permporometry, differed significantly between the two different membranes. For the first time, it was demonstrated that the micropore defects determined by permporometry were most likely open grain boundaries. The results were verified by direct observation of the open grain boundaries by a state-of-the-art XHR-scanning electron microscopy instrument. In addition, the permporometry data were also consistent with permeation data using 1,3,5-trimethylbenzene (TMB) as a probe molecule, separation data using an equimolar mixture of n-hexane and TMB, and nitrogen adsorption data.

  • 26.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ye, Pengcheng
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Han
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Correction: An experimental study of micropore defects in MFI membranes2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 197, p. 358-Article in journal (Refereed)
    Abstract [en]

    In the present work, two ultra-thin MFI membranes, prepared using hydroxide and fluoride ions as mineralizing agents, respectively, were carefully examined by permporometry. The amount of micropore defects, as determined by permporometry, differed significantly between the two different membranes. For the first time, it was demonstrated that the micropore defects determined by permporometry were most likely open grain boundaries. The results were verified by direct observation of the open grain boundaries by a state-of-the-art XHR-scanning electron microscopy instrument. In addition, the permporometry data were also consistent with permeation data using 1,3,5-trimethylbenzene (TMB) as a probe molecule, separation data using an equimolar mixture of n-hexane and TMB, and nitrogen adsorption data

  • 27.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ye, Pengcheng
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Han
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Reprint of: An experimental study of micropore defects in MFI membranes2014In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 192, p. 69-75Article in journal (Refereed)
    Abstract [en]

    In the present work, two ultra-thin MFI membranes, prepared using hydroxide and fluoride ions as mineralizing agents, respectively, were carefully examined by permporometry. The amount of micropore defects, as determined by permporometry, differed significantly between the two different membranes. For the first time, it was demonstrated that the micropore defects determined by permporometry were most likely open grain boundaries. The results were verified by direct observation of the open grain boundaries by a state-of-the-art XHR-scanning electron microscopy instrument. In addition, the permporometry data were also consistent with permeation data using 1,3,5-trimethylbenzene (TMB) as a probe molecule, separation data using an equimolar mixture of n-hexane and TMB, and nitrogen adsorption data

  • 28.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Zhou, Han
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    An experimental study of micropore defects in MFI membranes2013Conference paper (Refereed)
  • 29.
    Leduc, Jennifer
    et al.
    University of Cologne, Institute of Inorganic Chemistry,.
    Goenuellue, Yakup
    University of Cologne, Institute of Inorganic Chemistry,.
    Ghamgosar, Pedram
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    You, Shujie
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Choi, Heechae
    University of Cologne, Institute of Inorganic Chemistry.
    Vomiero, Alberto
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grosch, Matthias
    University of Cologne, Institute of Inorganic Chemistry.
    Mathur, Sanjay
    University of Cologne, Institute of Inorganic Chemistry.
    Electronically-Coupled Phase Boundaries in α‑Fe2O3/Fe3O4 Nanocomposite Photoanodes for Enhanced Water Oxidation2019In: ACS APPLIED NANO MATERIALS, E-ISSN 2574-0970, Vol. 2, no 1, p. 334-342Article in journal (Refereed)
    Abstract [en]

    Photoelectrochemical (PEC) water splittingreactions are promising for sustainable hydrogen productionfrom renewable sources. We report here, the preparation of α-Fe2O3/Fe3O4 composite films via a single-step chemical vapordeposition of [Fe(OtBu)3]2 and their use as efficient photoanode materials in PEC setups. Film thickness and phase segregation was controlled by varying the deposition time and corroborated through cross-section Raman spectroscopy and scanning electron microscopy. The highest water oxidationactivity (0.48 mA/cm2 at 1.23 V vs RHE) using intermittent AM 1.5 G (100 mW/cm2) standard illumination was found forhybrid films with a thickness of 11 μm. This phenomenon is attributed to an improved electron transport resulting from ahigher magnetite content toward the substrate interface and an increased light absorption due to the hematite layer mainly located at the top surface of the film. The observed high efficiency of α-Fe2O3/Fe3O4 nanocomposite photoanodes is attributed to the close proximity and establishment of 3D interfaces between the weakly ferro- (Fe2O3) and ferrimagnetic (Fe3O4) oxides, which in view of their differential chemical constitution andvalence states of Fe ions (Fe2+/Fe3+) can enhance the charge separation and thus the overall electrical conductivity of the layer.

  • 30.
    Mangalaraja, Ramalinga Viswanathan
    et al.
    Universidad de Concepción.
    Ananthakumar, Solaiappan
    CSIR, Materials and Minerals Division.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lopez, Marta
    Universidad de Concepción.
    Camurri, Carlos Porro
    Universidad de Concepción.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sintering, microstructural and mechanical characterization of combustion synthesized Y2O3 and Yb3+-Y2O32009In: Ceramic Society of Japan. Journal, ISSN 1882-0743, Vol. 117, no 1371, p. 1258-1262Article in journal (Refereed)
    Abstract [en]

    The present work highlights the microstructural features and mechanical properties of Y2O3 prepared with and without Yb3+ doping that processed through combustion synthesis involving various organic fuels such as urea, citric acid and glycine. Properties such as powder-now, particle packing, green density, % of shrinkage, sintered density, grain size, Vicker's microhardness (H-v) and fracture toughness (K-IC) were analyzed and compared with respect to the fuel sources. The as combusted precursors were calcined at 1100 degrees C for 4 h under oxygen atmosphere to obtain fully crystalline Y2O3 powders. Cylindrical pellets were fabricated as test specimens and sintered at 1600 degrees C for 3 h. The SEM images of the sintered yttria samples show an average grain size of < 3 mu m irrespective of the fuels. However, the mechanical properties show significant dependence on the fuels used. A maximum hardness of 6.8 +/- 0.1 and 7.0 +/- 0.1 GPa was obtained for Y2O3 and Yb3+ doped Y2O3 derived from glycine fuel. Whereas the maximum fracture toughness of 2.6 +/- 0.3 MPa m(1/2) was obtained for the samples derived from urea. The Yb3+ doping found to increase the bulk hardness of yttria from 0.2 to 0.6 GPa. The study contributes to appropriately select the fuels for obtaining high dense, mechanically stable yttria ceramics through combustion process.

  • 31.
    Mangalaraja, Ramalinga Viswanathan
    et al.
    Universidad de Concepción.
    Ananthakumar, Solaiappan
    NIIST, Materials & Minerals Division, Kerala.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Uma, Kasimayan
    Nagoya Institute of Technology.
    Lopez, Marta
    Universidad de Concepción.
    Camurri, Carlos Porro
    Universidad de Concepción.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Synthesis of nanocrystalline yttria through in-situ sulphated-combustion technique2009In: Ceramic Society of Japan. Journal, ISSN 1882-0743, Vol. 117, no 1370, p. 1065-1068Article in journal (Refereed)
    Abstract [en]

    An in-situ sulphated-combustion reaction was conducted on the precursor mixture consisting of yttrium nitrate, organic fuels (urea, citric acid and glycine) and 10 mol% ammonium sulphate [(NH4)(2)SO4] at 500 degrees C. Effect of sulphate addition on yttria particles morphology has been analyzed with respect to the types of fuels. In un-sulphated combustion, the calcined yttria powders showed rectangular particle morphology and low specific surface area. Whereas in sulphated-combustion spherical shaped yttria particles were achieved for glycine fuel. In the case of citric acid fuel, yttria powders with high specific surface area [26 m(2)/g] were obtained. For all the fuels, the sulphated-combustion reaction produced nanocrystalline yttria powders and they also had primary crystallite size below 4 nm in the as prepared conditions. Upon calcination at 1100 degrees C, these powders attained mean particle size of 50 nm which was confirmed by TEM.

  • 32.
    Mangalaraja, R.V.
    et al.
    University of Concepción.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedström, Peter
    Camurri, C.P.
    University of Concepción.
    Ananthakumar, S.
    Université Montpellier.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Microwave assisted combustion synthesis of nanocrystalline yttria and its powder characteristics2009In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 191, no 3, p. 309-314Article in journal (Refereed)
    Abstract [en]

    Microwave assisted combustion synthesis is used for fast and controlled processing of advanced ceramics. Single phase and sinter active nanocrystalline cubic yttria powders were successfully synthesized by microwave assisted combustion using the organic fuels urea, citric acid and glycine as reducing agents. The precursor powders were investigated by thermogravimetry (TG) and differential scanning colorimetry (DSC) analyses. The as-prepared precursors and the resulting oxide powders calcined at 1100 °C in oxygen atmosphere were characterized for their structure, particle size and morphology. The thermal analyses (TG/DSC), X-ray diffraction (XRD) and Fourier transform infra red (FT-IR) results demonstrate the effectiveness of the microwave assisted combustion synthesis. The scanning electron microscopy (SEM) observations show the different morphologies of as-prepared powders and transmission electron microscopy (TEM) shows the particle sizes in the range of 30-100 nm for calcined powders for different fuels. The results confirm that the homogeneous, nano scale yttria powders derived by microwave assisted combustion have high crystalline quality and the morphology of the as-prepared precursor powders depends on the nature of organic fuel used.

  • 33.
    Mangalaraja, R.V.
    et al.
    University of Concepción.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedström, Peter
    Kero, Ida
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Ramam, K.V.S.
    University of Concepción.
    Camurri, C.P.
    University of Concepción.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Combustion synthesis of Y2O3 and Yb-Y2O3: Part 1: Nanopowders and their characterization2008In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 208, no 1-3, p. 415-422Article in journal (Refereed)
    Abstract [en]

    Nanosized yttrium oxide and ytterbium doped yttrium oxide powders were prepared by ceramic combustion techniques such as flash combustion, citrate gel decomposition and glycine combustion using urea, citric acid and glycine respectively as fuels. As synthesized precursors and calcined powders were characterized for their structural, particle size and morphology, and the optimization of calcination process by differential scanning calorimetry and thermal gravimetry. The thermal analyses together with XRD results demonstrate the effectiveness of the combustion process for the synthesis of pure phase nanocrystalline powders. Nanocrystalline pure yttria powders were obtained by the calcination of as-prepared precursors at 1100 °C for 4 h.

  • 34.
    Melk, Latifa
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Turon-Vinas, Miquel
    CIEFMA—Department of Materials Science and Metallurgical Engineering, ETSEIB, Universitat Politècnica de Catalunya.
    Akhtar, Farid
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Antti, Marta-Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Anglada, Marc
    Department of Materials Science and Engineering, Universitat Politècnica de Catalunya, Barcelona, Universitat Politècnica de Catalunya, Universidad de Extremadura.
    Surface microstructural changes of Spark Plasma Sintered Zirconia after grinding and annealing2016In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, no 14, p. 15610-15617Article in journal (Refereed)
    Abstract [en]

    Spark plasma sintered zirconia (3Y-TZP) specimens have been produced of 140 nm 372 nm and 753 nm grain sizes by sintering at 1250 C, 1450 C and 1600 C, respectively. The sintered zirconia specimens were grinded using a diamond grinding disc with an average diamond particle size of about 60 µm, under a pressure of 0.9 MPa. The influence of grinding and annealing on the grain size has been analysed. It was shown that thermal etching after of ruff grinding of specimens at 1100 C for one hour induced an irregular surface layer of about a few hundred nanometres in thickness of recrystallized nano-grains, independently of the initial grain size. However, if the ground specimens were exposed to higher temperature, e.g. annealing at 1575 °C for one hour, the nano-grain layer was not observed and the final grain size was similar to that achieved by the same heat treatments on carefully polished specimens. Therefore, by appropriate grinding and thermal etching treatments, nanograined surface layer can be obtained which increases the resistance to low temperature degradation.

  • 35. Mouzon, Johanne
    Synthesis of Yb:Y2O3 nanoparticles and fabrication of transparent polycrystalline yttria ceramics2005Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    More efficient laser materials are needed for space applications in order to save weight and make cost-savings. The fabrication of polycrystalline ceramic materials is a solution to obtain new compositions with better efficiency. In order to produce a Yb doped Y2O3 laser material, we developed a process to obtain yttrium oxide nanosized particles doped with ytterbium and a sintering method that leads to transparent polycrystalline ceramics. First, nano-powder of yttria was fabricated from a precursor with transient morphology, i.d. yttrium hydroxynitrate platelets that decompose into spherical yttria nano-particles during calcination. The influence of different dewatering methods on such precursors was investigated. Water removal by freeze-drying was shown to be optimal for the production of non- agglomerated nano-particles compared with other methods that involve solvent removal by evaporation. This was attributed to the ability of freeze-drying to avoid the formation of solid bridges, since water is directly removed by sublimation. In a second step, doping with ytterbium was performed. Two precipitation routes were compared: precipitation of hydroxynitrate platelets and precipitation of amorphous carbonate. This latter was shown to allow a better distribution of ytterbium in the yttrium oxide matrix after calcination of the corresponding precursor. This was explained in terms of the good cation mixing in the amorphous particles, while formation of the hydroxynitrate platelets resulted in segregation of ytterbium, probably because a second phase with different ytterbium/yttrium composition precipitates in the first stages of the synthesis. Finally, a method combining pre-sintering in vacuum followed by hot isostatic pressing was shown to be successful to produce transparent yttria ceramics from agglomerated powders with high purity. Pre-sintering in vacuum agglomerates of closely-packed particles enables differential sintering, which is responsible for the complete elimination of porosity in the agglomerates and for the formation of intergranular porosity only. Then, hot isostatic pressing treatment of the pre-sintered samples using the glass-canning technique reactivates sintering and coarsening, which causes almost complete pore elimination. Furthermore, a liquid phase formed during sintering because of pollution from the furnace. This liquid phase is thought of as to have helped densification to some extent. The best transparent ceramic showed a transmittance of 43% at 400 nm.

  • 36.
    Mouzon, Johanne
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Synthesis of ytterbium-doped yttrium oxide nanoparticles and transparent ceramics2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, the author reports on a ceramic process leading to transparent ytterbium doped yttrium oxide ceramics. The full production route was investigated, namely: powder preparation, compaction and sintering. First, yttria nano-powder was fabricated from a precursor with transient morphology, i.e. yttrium hydroxynitrate platelets that decomposed into spherical yttria nano-particles during calcination. The influence of different dewatering methods on such precursors was investigated. Water removal by freeze-drying was shown to be optimal for the production of non- agglomerated nano-particles compared to other methods that involve solvent removal by evaporation. This was attributed to the ability of freeze-drying to avoid the formation of solid bridges, since water is directly removed by sublimation. In a second step, doping with ytterbium was performed. Two precipitation routes were compared: precipitation of hydroxynitrate platelets and precipitation of amorphous carbonate. The latter route was shown to allow a better distribution of ytterbium in the yttrium oxide matrix after calcination of the corresponding precursor. This was attributed to good cation mixing within the amorphous particles, while formation of the hydroxynitrate platelets resulted in segregation of ytterbium because of the precipitation of an ytterbium-rich secondary phase. Because of the laborious character of the above techniques, an alternative method for synthesizing yttrium oxide powder was developed. This method not only allows for producing weakly-agglomerated nano-particles with equiaxed morphology, but is also a very time-efficient process. Its characteristic feature lies in the ability to skip two processing steps encountered in common precipitation techniques (i.e. filtration and drying). The method is based on combustion synthesis, sulfation, and calcination at high temperature. Through careful tailoring of the process parameters, evolution of the cellular nanostructure towards individual yttrium oxide nano- particles was obtained during firing. A method combining pre-sintering in vacuum followed by hot isostatic pressing (HIP) using glass encapsulation was shown to be successful to produce transparent yttria ceramics from agglomerated powders. Pre- sintering in vacuum of compact agglomerates enables differential sintering, resulting in only intergranular porosity. Subsequent HIP treatment of the pre-sintered samples caused almost complete pore elimination and achievement of transparency. However, macro-defects were present in the final material. From these results it became obvious that the packing homogeneity must be improved. For comparison, green-bodies were produced by slip-casting or pressing followed by cold isostatic pressing (CIP). Rheology studies were performed in order to tailor the milling conditions and the quantity of dispersant to obtain slurries with minimum viscosity and which were suitable for slip-casting. Although slip-cast pellets exhibited similar densities as pressed samples after pre-sintering, they showed more homogeneous optical properties after HIP. This was attributed to density gradients in the pressed compacts. By using the novel powder synthesis and HIP methods developed in this work, yttrium oxide transparent ceramics doped with 30 at% ytterbium were fabricated. The best sample showed a transmittance of 25% at 400 nm for a thickness of 3mm.

  • 37.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Bhuiyan, Iftekhar Uddin
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Forsmo, Seija P.E.
    LKAB Research and Development.
    Hedlund, Jonas
    Cryo-SEM method for the observation of entrapped bubbles and degree of water filling in large wet powder compacts2011In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 242, no 2, p. 189-196Article in journal (Refereed)
    Abstract [en]

    There are generally two problems associated with cryogenic scanning electron microscopy (cryo-SEM) observations of large wet powder compacts. First, because water cannot be vitrified in such samples, formation of artefacts is unavoidable. Second, large frozen samples are difficult to fracture but also to machine into regular pieces which fit in standard holders, especially if made of hard materials like ceramics. In this article, we first describe a simple method for planning hard cryo-samples and a low-cost technique for cryo-fracture and transfer of large specimens. Subsequently, after applying the entire procedure to green pellets of iron ore produced by balling, we compare the influence of plunge- and unidirectional freezing on large entrapped bubbles throughout the samples as well as the degree of water filling at the outer surface of the pellets. By carefully investigating the presence of artefacts in large areas of the samples and by controlling the orientation of the sample during freezing and preparation, we demonstrate that unidirectional freezing enables the observation of large entrapped bubbles with minimum formation of artefacts, whereas plunge freezing is preferable for the characterization of the degree of water filling at the outer surface of wet powder compacts. The minimum formation of artefacts was due to the high packing density of the iron ore particles in the matrix

  • 38.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bhuiyan, Iftekhar Uddin
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    The structure of montmorillonite gels revealed by sequential cryo-XHR-SEM imaging2016In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 465, p. 58-66Article in journal (Refereed)
    Abstract [en]

    Imaging by extreme high resolution-scanning electron microscopy (XHR-SEM) with a monochromated and decelerated beam was applied on 5% (wt/wt) Na and Ca-montmorillonite gels frozen by high pressure freezing (HPF). In order to visualize the three-dimensional structure and the contacts between clay platelets, a new approach was developed. It consists in recording a sequence of micrographs on a region of interest during controlled sublimation. This simple method allows to rewind and to relate the instantaneous configuration between several particles to their original position in the hydrated state. Consequently, aggregates of parallel platelets (i.e. curved tactoids) were present in the Ca-sample and the instantaneous position of these aggregates in the course of sedimentation was revealed. The Na-sample consisted of a continuous network of flexible platelets sharing mostly face-to-face (FF) contacts caused by jamming at the relatively high concentration of the suspension (5% (wt/wt)), which was above the gel transition. Yet individual platelets belonging to the smallest size fraction were observed to be fully dispersed within the entangled structure, which confirmed the repulsive character of the gel. Substructures consisting of several platelets connected by FF-associations were also evidenced. The origin and potential impact of such substructures on the occurrence of the sol–gel transition and birefringence are discussed.

  • 39.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Dujardin, C.
    Claude Bernard/Lyon1 University.
    Tillement, O.
    Claude Bernard/Lyon1 University.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Synthesis and optical properties of Yb0.6Y1.4O3 transparent ceramics2008In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 464, no 1-2, p. 407-411Article in journal (Refereed)
    Abstract [en]

    Transparent yttrium oxide ceramics doped with 30 at.% ytterbium were successfully produced by a combination of pre-sintering and hot isostatic pressing. The influence on the final transparency of different densification states and porosity configurations obtained by varying pre-sintering conditions were investigated by optical and electron microscopy. Our results show that densification prior to the final stage of sintering is necessary to limit final porosity. Samples showing open porosity were found to lead to pore entrapment because of the diffusion of argon inside the glass capsule during hot isostatic pressing. Transmittance measurements showed that the valence charge of the ytterbium ions was 3+ at the end of the process, indicating no effect of reduction when pre-sintering in vacuum was employed.

  • 40.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Glowacki, Emily
    Luleå tekniska universitet.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Comparison between slip-casting and uniaxial pressing for the fabrication of translucent yttria ceramics2008In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 43, no 8, p. 2849-2856Article in journal (Refereed)
    Abstract [en]

    Slip casting and uniaxial pressing were compared as first consolidation stages prior to cold isostatic pressing (CIP) to produce translucent yttria ceramics. In the first step, yttria slurries suitable for slip casting were prepared. The viscosity was optimized with respect to the starting agglomeration state, amount of dispersant, milling time, and number of milling balls. Secondly, pellets were prepared either by slip casting or uniaxial pressing and then cold-isostatically pressed. Finally, the pellets were made translucent by a combination of pre-sintering and hot isostatic pressing (HIP). Although slip-cast and pressed samples exhibited similar green-body densities after CIP and pre-sintering, the samples prepared by slip casting were more homogeneous in terms of translucency and microstructure throughout their bodies. This was attributed to the ability of slip casting to minimize density gradients during packing, and to the beneficial effect of ball-milling to remove larger agglomerates before casting. Therefore, slip casting as a first consolidation stage prior to CIP appears to be more suitable than uniaxial pressing in order to prepare homogeneous optical ceramics.

  • 41.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Growth of thin MFI zeolite films: Characterization by XHR-SEM and HR-TEM2011In: 6th EEIGM International Conference Advanced Materials Research: 7th and 8th November, 2011 EEIGM, Nancy, France, 2011Conference paper (Refereed)
  • 42.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lindbäck, Ture
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Influence of agglomeration on the transparency of yttria ceramics2008In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 91, no 10, p. 3380-3387Article in journal (Refereed)
    Abstract [en]

    In this work, five yttria powders with slightly different states of agglomeration, inherited from various procedures of dewatering the same precursor, were densified by a combination of vacuum sintering followed by hot isostatic pressing (HIP). In order to relate the densification behavior of each powder to its state of agglomeration, all powders were characterized by tap density measurements, X-ray diffraction, nitrogen adsorption, and laser scattering, while the microstructures of the corresponding densified samples were studied by optical and scanning electron microscopy. The five yttria powders produced sintered samples that differed remarkably from each other in terms of transparency. These discrepancies were related to the degree of fineness in the powders at two different levels. At the level of primary particles, fine and weakly agglomerated powder was very sinterable, causing abnormal grain growth to occur only in the very late stage of sintering. However, the resulting entrapped pores and reduction due to vacuum sintering were responsible for poor optical properties. At the agglomerate level, a bimodal size distribution was identified for all powders. For powders showing severe agglomeration of the primary particles, increasing the relative content of the smaller size population of agglomerates was found to trigger abnormal grain-growth earlier during presintering. This was attributed to the density around large agglomerates exceeding a critical threshold in the green bodies. Finally, transparency was achieved in samples for which presintering was stopped before grain growth became abnormal. This confirmed that the key to successfully obtaining transparency was to keep porosity intergranular, which could be removed subsequently by HIP treatment.

  • 43.
    Mouzon, Johanne
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Maitre, A.
    Laboratoire Science des Procédés Céramiques et Traitements de Surface, UMR CNRS 6638, UFR Sciences et Techniques, 123 Avenue Albert Thomas, F-87060 Limoges Cedex.
    Frisk, Lars
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lehto, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Odén, Magnus
    Fabrication of transparent yttria by HIP and the glass-encapsulation method2009In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 29, no 2, p. 311-316Article in journal (Refereed)
    Abstract [en]

    This method consists of a combination of vacuum sintering at 1600 °C followed by hot isostatic pressing (HIP) at 1500 °C of a highly agglomerated commercial powder. The use of evacuated glass capsules to perform HIP treatment allowed samples that showed open porosity after vacuum sintering to be sintered to transparency. The sintering response of the investigated powder was studied by careful microstructural observations using scanning electron microscopy and optical microscopy both in reflection and transmission. The successful key of this method was to keep porosity intergranular during pre-sintering, so that it can be removed subsequently by HIP treatment. It was found that agglomerates of closely packed particles are helpful to reach that purpose, since they densify fully and leave only intergranular porosity. However, performing HIP treatment at 1625 °C was found to result in opaque samples. This was attributed to the diffusion of argon inside the capsule. Contamination at different steps of processing was also investigated by inductively coupled plasma mass spectrometry (ICP-MS).

  • 44. Mouzon, Johanne
    et al.
    Nordell, Patricia
    Luleå tekniska universitet.
    Adrien, Thomas
    Luleå tekniska universitet.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Comparison of two different precipitation routes leading to Yb doped Y2O3 nano-particles2007In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 27, no 4, p. 1991-1998Article in journal (Refereed)
    Abstract [en]

    Two different precipitation routes leading to (YbxY1-x)2O3 nano-particles (with x = 0; 0.027; and 0.31) were compared, namely, precipitation of hydroxynitrate platelets and amorphous carbonate spherical particles. For both methods, the particle morphology was observed by scanning electron microscopy. X-ray diffraction studies of the unit cell, energy dispersive X-ray analysis and inductive coupled plasma spectroscopy were used to check the ytterbium distribution. The precipitation of amorphous carbonate was found to produce particles with uniform morphology and homogeneous distribution of ytterbium, while hydroxide precipitation favours the formation of hard and dense ytterbium-rich agglomerates. These differences are discussed in terms of precipitation, growth and agglomeration behaviour. The sinterability of both resulting powders is also discussed

  • 45. Mouzon, Johanne
    et al.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Alternative method to precipitation techniques for synthesizing yttrium oxide nanopowder2007In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 177, no 2, p. 77-82Article in journal (Refereed)
    Abstract [en]

    Yttrium oxide nano-powder has been successfully synthesized by a novel approach. In the first step, a foamy structure was produced by combustion synthesis using yttrium nitrate and glycine. This was followed by the addition of sulfate ions and calcination at 1100 °C for 4 h. The sulfated and unsulfated powders were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and the Brunauer-Emmett-Teller method (BET). The sinterability of the resulting powders was also studied by dilatometry. The studies indicated that this method not only allows for producing weakly-agglomerated nano-particles, but is also a very time-efficient process in comparison to precipitation techniques. Moreover, the possibility of performing all processing steps in a fully automated batch reactor was also considered.

  • 46. Mouzon, Johanne
    et al.
    Odén, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Tillement, Olivier
    Université C. Bernard Lyon I.
    Jorand, Yves
    GEMPPM, INSA Lyon.
    Effect of drying and dewatering on yttria precursors with transient morphology2006In: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 89, no 10, p. 3094-3100Article in journal (Refereed)
    Abstract [en]

    The influence of drying and dewatering of a yttrium hydroxynitrate precursor with transient morphology was investigated. The ability of this precursor to form soft agglomerated nanoparticles after calcination is dependent on the dewatering method. Freeze drying leads to finer particles than other dewatering methods that involve removal of the solvent from its liquid state. As water is directly removed by sublimation during freeze drying, this method inhibits the formation of solid bridges between hydroxynitrate platelets. These bridges, which form with the other dewatering methods, destabilize the spheroidization process of the platelets during subsequent firing at high temperatures.

  • 47.
    Nabavi, Mohammad Sadegh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Zhou, Ming
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Stability of colloidal ZSM-5 catalysts synthesized in fluoride and hydroxide media2019In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 278, p. 167-174Article in journal (Refereed)
    Abstract [en]

    ZSM-5 zeolite crystals with carefully controlled thicknesses in the range 20–110 nm, i.e. in the colloidal domain, were synthesized in fluoride and hydroxide media. The crystals were treated in steam at high temperature to evaluate the stability and evaluated by SEM, XRD, NMR and NH3-TPD. The results showed that the framework of crystals synthesized in fluoride media was more stable than the framework of crystals synthesized in hydroxide media. This should be an effect of lower concentration of structural defects and silanol groups in the former zeolites as reported by other groups. However, independently of the synthesis conditions, all crystals dealuminated rapidly when treated with steam at the conditions investigated in the present work.

  • 48.
    Nyberg, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Minami, Ichiro
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Formation of Boundary Film from Ionic Liquids Enhanced by Additives2017In: Applied Sciences, E-ISSN 2076-3417, Vol. 7, no 5, article id 433Article in journal (Refereed)
    Abstract [en]

    Room temperature ionic liquids (RTILs) have several properties that make them interesting candidates as base fluids for extreme conditions. However, a lack of compatibility with tribo-improving additives combined with an often overly aggressive nature is limiting their use as base fluids. To overcome these drawbacks, hydrocarbon-imitating RTIL base fluids have recently been developed. In this study, the effects of several common additives in the novel RTIL (P-SiSO) were examined by laboratory tribotesting. A reciprocating steel-steel ball-on-flat setup in an air atmosphere was used, where the lubricant performance was evaluated over a range of loads and temperatures. Surface analyses after testing were carried out using optical profilometry, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Neat P-SiSO displayed high performance in the tribotests. At an elevated load and temperature, a shift in lubrication mode was observed with an accompanying increase in friction and wear. Surface analysis revealed a boundary film rich in Si and O in the primary lubrication mode, while P was detected after a shift to the secondary lubrication mode. An amine additive was effective in reducing wear and friction under harsh conditions. The amine was determined to increase formation of the protective Si–O film, presumably by enhancing the anion activity.

  • 49.
    Rezaei, Fateme
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mosca, Alessandra
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Webley, P.A.
    Monash University, Melbourne, VIC.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The effect of wall porosity and zeolite film thickness on the dynamic behavior of adsorbents in the form of coated monoliths2011In: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 81, no 2, p. 191-199Article in journal (Refereed)
    Abstract [en]

    The effects of wall porosity, channel width distribution and zeolite film thickness on the performance of 400 and 1200 cells per square inch (cpsi) cordierite monoliths coated with zeolite X films with thicknesses of 1.5 and 2.5 μm were examined. To investigate the effect of wall porosity and restrict growth of zeolite to the external surface of the monolith channels, the macro pores in the walls of the 1200 cpsi cordierite monoliths were filled with colloidal α-alumina particles. The adsorbents were characterized by Scanning Electron Microscopy, Mercury Intrusion Porosimetry and carbon dioxide breakthrough experiments and a mathematical model describing the diffusion and adsorption in the system was fitted to the data. The model accounted for carbon dioxide uptake by filling the pores in the support by carbon dioxide gas and adsorption of carbon dioxide on cordierite, alumina and zeolite. The model indicates that the uptake of carbon dioxide by adsorption on cordierite is much slower than by pore filling and too slow to influence the very fast breakthrough experiments with monoliths without zeolite film that are over in less than 1 minute. It was shown that the pores in the cordierite monolith result in dispersion by pore filling with carbon dioxide gas, not adsorption. The CO2 adsorption capacity of a 1200 cpsi monolith coated with a 2.5 μm film was 0.13 mmol/cm3 adsorbent, which should be compared to the adsorption capacity of zeolite X beads, which is about 2.3 mmol/cm3 adsorbent. To increase adsorption capacity of a non-porous zeolite coated monolith, film thickness could be increased. The model indicated that the film thickness could be increased up to about 10 μm without increasing the dispersion and thereby approach the adsorption capacity for beads. However, simulation of the whole cycle must be performed in order to find the optimum film thickness for a real cyclic process. This work has lead to better understanding of the role of the support porosity and pore size distribution and film thickness for coated monolith adsorbents.

  • 50.
    Rodiouchkina, Maria
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Berglund, Kim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Forsberg, Fredrik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rodushkin, Ilia
    ALS Laboratory Group, ALS Scandinavia AB.
    Larsson, Roland
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Material Characterization and Influence of Sliding Speed and Pressure on Friction and Wear Behavior of Self-Lubricating Bearing Materials for Hydropower Applications2018In: Lubricants, ISSN 2075-4442, Vol. 6, no 2, article id 39Article in journal (Refereed)
    Abstract [en]

    Nowadays, hydropower plants are forced to have more frequent power control and the self-lubricated bearings used in the applications are one of the most critical components affected by the continuously changing operating conditions. In this study, microstructure and composition of two commercially available bearing materials (Orkot TXM Marine and Thordon ThorPlas) used in hydropower turbines were studied. In addition, the influence of sliding speed and applied pressure on the friction and wear behavior of the materials was investigated systematically for dry sliding conditions. The bearing materials were characterized using X-ray microtomography, Nuclear Magnetic Resonance (NMR) spectroscopy and Inductively Coupled Plasma–Sector Field Mass Spectrometry (ICP-SFMS) techniques. Friction and wear tests were carried out with a polymer pin sliding against a stainless steel (SS2333) plate with a linear reciprocating motion. Test conditions were: room temperature, 9–28 MPa pressure and 10–40 mm/s sliding speed ranges. Surface analysis of the polymer pins and the wear tracks were performed by optical profilometry, Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) techniques. Test results show that, for both materials, the coefficient of friction (COF) is decreasing at higher pressures. Surface analysis reveals higher concentrations of solid lubricants in the transfer layers formed at higher pressures, explaining the decrease in COF. Furthermore, the specific wear rate coefficients are increasing at higher sliding speeds, especially at lower pressures. Results of this study demonstrate that, under dry sliding conditions, changes in sliding speed and pressure have a significant influence on the tribological behavior of these bearing materials.

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