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  • 1.
    Akhtar, Farid
    et al.
    Stockholm University, Department of Materials and Environmental Chemistry.
    Ojuva, Arto
    Stockholm University, Department of Materials and Environmental Chemistry.
    Wirawan, Kompiang
    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.
    Bergström, Lennart
    Stockholm University, Department of Materials and Environmental Chemistry.
    Hierarchically porous binder-free silicalite-1 discs: a novel support for all-zeolite membranes2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, no 24, p. 8822-8828Article in journal (Refereed)
    Abstract [en]

    Thermal expansion mismatch between the zeolite film and the support is an important cause for the formation of defects and cracks during the fabrication and use of zeolite membranes. We have studied how silicalite-1 discs with a permeability comparable to commercially available alumina supports can be produced by pulsed current processing (PCP) as a novel substrate for all-zeolite membranes. Hierarchically porous and mechanically strong membrane supports where the surface area and crystallography of the silicalite-1 particles were maintained could be obtained by carefully controlling the thermal treatment during PCP consolidation. In situ X-ray diffraction and dilatometry showed that the coefficient of thermal expansion (CTE) of the silicalite-1 substrate was negative in the temperature range 200-800 degrees C while the commonly used alumina substrate displayed a positive CTE. The critical temperature variation, Delta T, and thicknesses for crack-free supported zeolite films with a negative CTE were estimated using a fracture energy model. Zeolite films with a thickness of 1 mu m can only sustain a relatively modest Delta T of 100 degrees when supported onto alumina substrates while the all-zeolite membranes can support temperature variations above 500 degrees

  • 2.
    Babushkin, O.
    et al.
    Luleå tekniska universitet.
    Lindbäck, Ture
    Holmgren, A.
    Jianguo, Li
    Hermansson, L.
    Thermal expansion of hot isostatically pressed hydroxyapatite1994In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 4, no 3, p. 413-415Article in journal (Refereed)
  • 3.
    Goncalves, Gil
    et al.
    TEMA-NRD, Mechanical Engineering Department, University of Aveiro.
    Marques, Paula
    TEMA-NRD, Mechanical Engineering Department, University of Aveiro.
    Barros-Timmons, Ana
    CICECO, Department of Chemistry, University of Aveiro.
    Bdkin, Igor
    TEMA-NRD, Mechanical Engineering Department, University of Aveiro.
    Singh, Manoj
    TEMA-NRD, Mechanical Engineering Department, University of Aveiro.
    Emami, Nazanin
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Machine Elements.
    Gracio, Jose
    TEMA-NRD, Mechanical Engineering Department, University of Aveiro.
    Graphene oxide modified with PMMA via ATRP as a reinforcement filler2010In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 40, no 44, p. 9927-9934Article in journal (Refereed)
    Abstract [en]

    Graphene is a two-dimensional new allotrope of carbon, which is stimulating great curiosity due to its superior mechanical, electrical, thermal and optical properties. Particularly attractive is the availability of bulk quantities of graphene (G) which can be easily processed by chemical exfoliation, yielding graphene oxide (GO). The resultant oxygenated graphene sheets covered with hydroxyl, epoxy and carboxyl groups offer tremendous opportunities for further functionalization opening plenty of opportunities for the preparation of advanced composite materials. In this work poly(methyl methacrylate) (PMMA) chains have been grafted from the GO surface via atom transfer radical polymerization (ATRP), yielding a nanocomposite which was soluble in chloroform. The surface of the PMMA grafted GO (GPMMA) was characterized by AFM, HRTEM, Raman, FTIR and contact angle. The interest of these novel nanocomposites lies in their potential to be homogenously dispersed in polymeric dense matrices and to promote good interfacial adhesion, of particular relevance in stress transfer to the fillers. PMMA composite films were prepared using different percentages of GPMMA and pristine GO. Mechanical analysis of the resulting films showed that loadings as low as 1% (w/w) of GPMMA are effective reinforcing agents, yielding tougher films than pure PMMA films and even than composite films of PMMA prepared with GO. In fact, addition of 1% (w/w) of GPMMA fillers led to a significant improvement of the elongation at break, yielding a much more ductile and therefore tougher material. Thermal analysis showed an increase of the thermal stability properties of these films providing evidence that strong interfacial interactions between PMMA and GPMMA are achieved. In addition, AFM analysis, in friction force mode, is demonstrated to be an effective tool to analyse the surface filler distribution on polymer matrices

  • 4.
    Kozma, Erika
    et al.
    CNR.
    Concina, Isabella
    CNR IDASC SENSOR Lab.
    Braga, Antonio
    CNR IDASC SENSOR Lab.
    Borgese, Laura
    INSTM and Chemistry for Technologies Laboratory.
    Depero, Laura E.
    INSTM and Chemistry for Technologies Laboratory.
    Vomiero, Alberto
    SENSOR Lab, Department of Chemistry and Physics, Brescia University and CNR-IDASC.
    Sberveglieri, Giorgio
    CNR IDASC SENSOR Lab.
    Catellani, Marinella
    CNR.
    Metal-free organic sensitizers with a sterically hindered thiophene unit for efficient dye-sensitized solar cells2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, no 36, p. 13785-13788Article in journal (Refereed)
    Abstract [en]

    Two new organic sensitizers for dye solar cells containing a sterically hindered moiety have been synthesized. The introduction of a 3,4-dibutyl-thiophene ring into D-π-A dyes reduces the sensitizer aggregation and allows the preparation of solar cells with PCE of 7.17% and 6.27% without the use of coadsorbant agents. © 2011 The Royal Society of Chemistry.

  • 5. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Modification of MFI membranes with amine groups for enhanced CO2 selectivity2010In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, no 11, p. 2219-2225Article in journal (Refereed)
    Abstract [en]

    Much research on zeolite membranes has been devoted to MFI type zeolite and these membranes can be prepared reproducibly with high quality by our group. However, the MFI pores are too large for separation of small molecules such as CO2, H-2 CH4, and H2O by molecular sieving and the CO2 affinity is not sufficiently strong in our current membranes with quite high Si/Al ratio to achieve CO2 selective membranes. In the present work, existing MFI membranes with high Si/Al ratio are modified with methylamine to increase the CO2 affinity and thus increase the CO2 selectivity. To the best of our knowledge, this is the first time this type of modification is reported for zeolite membranes. These membranes were then evaluated for separation of CO2 from various mixtures of CO2, H-2, CH4 and H2O. The modification had significant effects on both permeances and separation factors and the selectivity towards CO2 was increased considerably for all the feed mixtures tested. The highest separation factor was observed for a CO2/CH4/H2O mixture and alpha-CO2/CH4 was 12 at about 40 degrees C. At the same time, the CO2 permeance was as high as 9 x 10(-7) mol m(-2) s(-1) Pa-1. The separation factor for the amine-modified silicalite-1 membranes was comparable to the highest reported separation factors for MFI membranes, while the CO2 permeance was higher than reported for other selective MFI membranes.

  • 6.
    Mihailova, B.
    et al.
    Luleå tekniska universitet.
    Engström, V.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Holmgren, Allan
    Sterte, Johan
    Infrared spectroscopic study of a γ-mercaptopropyltrimethoxysilane monolayer on a gold surface1999In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 9, no 7, p. 1507-1510Article in journal (Refereed)
    Abstract [en]

    Reflectance-absorption infrared spectra of ?-mercaptopropyltrimethoxysilane (?-MPT) adsorbed on Au (111)-oriented films are analyzed on the basis of the calculated vibrational modes of a monomer, a dimer and n-membered rings of SiO3R (R=CH2CH2CH2SAu). The results show that the ?-MPT molecules adsorbed on the Au surface are partially hydrolyzed and that the orientation of the methyl groups and propyl chains are near perpendicular to the surface. After a hydrolysis procedure, the SiO3 groups in ?-MPT form a quasi two-dimensional system built predominantly of 6-membered puckered Si-O rings. Additional treatment of the ?-MPT monolayer with a surface-charge-reversing cationic polymer disrupts the connectivity and increases the topological disorder in the silicate system.

  • 7.
    Mintova, Svetlana
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Valtchev, Valentin
    Luleå tekniska universitet.
    Schoeman, Brian
    Luleå tekniska universitet.
    Sterte, Johan
    Preparation of ZSM-5 films from template free precursors1997In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 7, no 12, p. 2341-2342Article in journal (Refereed)
    Abstract [en]

    Thin films of zeolite ZSM-5 on quartz substrates have been prepared in the absence of organic templates by growth of adsorbed seed crystals attached to a polymer-modified substrate surface.

  • 8.
    Mintova, Svetlana
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Valtchev, Valentin
    Luleå tekniska universitet.
    Schoeman, Brian
    Luleå tekniska universitet.
    Sterte, Johan
    ZSM-5 films prepared from template free precursors1998In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 8, no 10, p. 2217-2221Article in journal (Refereed)
    Abstract [en]

    Thin continuous films of zeolite ZSM-5 were synthesized on quartz substrates. The substrates were first surface modified and covered by a monolayer of colloidal silicalite-1 seed crystals. These crystals were grown into continuous films with thicknesses in the range 230-3500 nm by hydrothermal treatment in a synthesis gel free from organic templates. The preferential orientation of the crystals constituting the film was initially one with thec-axis close to parallel to the substrate surface. During the course of crystallization this orientation changed to one with most of the crystals having the c-axes directed approximately 35° from perpendicular to the substrate surface. A mechanism explaining this behavior is proposed. The final thickness of the film was controlled by the synthesis time but also by the addition of seed crystals to the synthesis gel. Films prepared according to this method may be of great value for the development of zeolite based membranes.

  • 9.
    Muthukumar, Kaliappan
    et al.
    Tyndall National Institute, University College Cork.
    Larsson, Andreas
    Explanation of the different preferential binding sites for Ce and la in M2@C80 (M = Ce, La2008In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 18, no 28, p. 3347-3351Article in journal (Refereed)
    Abstract [en]

    Metallofullerenes have many possible uses in technology and even in bio-medical applications. Some fullerenes have been found to have two incarcerated metal atoms such as M2@C80 (M = La, Ce, etc.). We have calculated the structural and electronic properties of Ce 2@C80 using density functional theory (DFT). Ce is known to be preferentially incorporated into the Ih symmetric C 80 isomer as La does in La2@C80. We have found that Ce2@C80 has a D3d symmetric ground state structure and that Ce binds to a different type of binding site compared to other cerium containing fullerenes, such as Ce@C82. This binding site also differs compared to La in La2@C80, which is D 2h symmetric. The two Ce atoms inside the C80-I h cage are equivalent and retain their f-electron. The Ce atoms bind on-top of one carbon atom (and its three neighbors) in Ce2@C 80, compared to in the center of a six-membered ring as in C 82. This novel binding site minimizes Ce(f)⋯Ce(f) overlap in favour of Ce-C bonding, giving the D3d configuration

  • 10.
    Shah, Faiz Ullah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Glavatskih, Sergei
    System and Component Design, KTH, Royal Institute of Technology.
    Dean, Pamela M.
    School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
    MacFarlane, Douglas R.
    School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
    Forsyth, Maria
    Department of Materials Engineering, Monash University.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Halogen-free chelated orthoborate ionic liquids and organic ionic plastic crystals2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 14, p. 6928-6938Article in journal (Refereed)
    Abstract [en]

    Five halogen-free orthoborate salts comprised of three different cations (cholinium, pyrrolidinium and imidazolium) and two orthoborate anions, bis(mandelato)borate and bis(salicylato)borate, were synthesised and characterised by DSC, X-ray diffraction and NMR. DSC measurements revealed that glass transition points of these orthoborate salts are in the temperature range from −18 to −2 °C. In addition, it was found that [EMPy][BScB] and [EMIm][BScB] salts have solid–solid phase transitions below their melting points, i.e. they exhibit typical features of plastic crystals. Salts of the bis(salicylato)borate anion [BScB]− have higher melting points compared with corresponding salts of the bis(mandelato)borate anion [BMB]−. Single crystal X-ray diffraction crystallography (for [Chol][BScB] crystals) and solid-state multinuclear (13C, 11B and 15N) NMR spectroscopy were employed for the structural characterisation of [Chol][BScB], [EMPy][BScB] and [EMIm][BScB], which are solids at room temperature: a strong interaction between [BScB]− anions and [Chol]+ cations was identified as (i) hydrogen bonding between OH of [Chol]+ and carbonyl groups of [BScB]− and (ii) as the inductive C–Hπ interaction. In the other salt, [EMIm][BScB], anions exhibit ππ stacking in combination with C–Hπ interactions with [EMIm]+ cations. These interactions were not identified in [EMPy][BScB] probably because of the lack of aromaticity in cations of the latter system. Our data on the formation of a lanthanum complex with bis(salicylato)borate in the liquid mixture of La3+(aq) with [Chol][BScB] suggest that this class of novel ILs can be potentially used in the extraction processes of metal ions of rare earth elements.

  • 11.
    Tosheva, Lubomira
    et al.
    Luleå tekniska universitet.
    Valtchev, Valentin
    Université de Haute Alsace.
    Sterte, Johan
    Amorphous very high surface area silica macrostructures2000In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 10, no 10, p. 2330-2337Article in journal (Refereed)
    Abstract [en]

    A procedure for the preparation of amorphous silica spherical macroparticles using strongly basic anion exchange gel resins as shape directing macro-templates is presented. Resin beads were hydrothermally treated with either clear homogeneous TPA–silicate solutions containing tetraethoxysilane, tetrapropylammonium hydroxide and distilled water or with sodium silicate solutions. As a result of the ion exchange of silica species into the resin structure, resin–silicate composites were formed. After separation and drying of the resin–silicate composites, the resin was removed by combustion leaving solid spherical silica particles with surface areas exceeding 1000rm2rgm1. Two types of gel resins having different active groups and degrees of cross-linking were employed and the products obtained were characterised by SEM, Raman spectroscopy and nitrogen adsorption measurements. The type of the resin as well as the type of silicate solution used were of great importance for the pore structure of the final materials.

  • 12.
    Törncrona, A.
    et al.
    Chalmers University of Technology.
    Sterte, Johan
    Otterstedt, J-E
    Chalmers University of Technology.
    Preparation of a novel fibrous catalyst support1995In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 5, no 1, p. 121-126Article in journal (Refereed)
    Abstract [en]

    A method for preparing wash-coated silica fibres is described. Colloidal silica particles (22 nm) were deposited onto the surface of 2 μm amorphous silica fibres, surface-modified by deposition of a thin film of amorphous silica with a high density of silanol groups and with the charge reversed by adsorption of a water-soluble cationic polymer. This deposition resulted in an increase in specific surface area from 0.9 m2 g-1 for the fibre to 40 m2 g-1 for the fibre with deposited silica particles. Hydrothermal treatment at 750°C in 100% steam for 24 h fixed the silica particles onto the fibre surface and made them coalesce into a strong porous structure. During this process, the specific surface area decreased from 40 to 30 m2 g-1. Particles of fibrillar boehmite were deposited onto the surface of silica fibres. The boehmite particles were fixed by thermal treatment at 550°C, during which the boehmite was transformed into γ-Al2O3. The specific surface area of the alumina wash-coated silica fibres was 28 m2 g-1. Wash-coated fibres were characterized by nitrogen adsorption-desorption analysis, scanning and transmission electron microscopy (SEM and TEM).

  • 13.
    Zhou, Ming
    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.
    Assembly of oriented iron oxide and zeolite crystals via biopolymer films2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 47, p. 24877-24881Article in journal (Refereed)
    Abstract [en]

    Biopolymers are developed as functional intermediate linkers for the assembly of nano and submicron-sized crystals. Mediated by the interlayers, iron oxide and zeolite crystals with varied shapes (cubic, ellipsoidal, and discoidal) are organized into uniformly oriented monolayers on glass plates and macroporous alumina supports. The crystal monolayers can be near-perfect transferred onto the substrate upon calcination, which are suitable for further growth. The assembled crystals display a range of colors, and important mechanisms with direct evidence for explaining this optical appearance are proposed.

  • 14.
    Zhou, Ming
    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.
    Oriented monolayers of submicron crystals by dynamic interfacial assembly2012In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, no 8, p. 3307-3310Article in journal (Refereed)
    Abstract [en]

    Large-area, void-free monolayers of oriented submicron crystals (silicalite-1, 800 nm and hematite, 400 nm) were fabricated on an air-water interface by dynamic interfacial assembly and were transferred onto solid substrates with different properties (porous, hydrophobic, conductive

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