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  • 1.
    Akhtar, Farid
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Rehman, Yaser
    Department of Metallurgical and Materials Engineering, University of Engineering and Technology Lahore, Pakistan.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    A study of the sintering of diatomaceous earth to produce porous ceramic monolithswith bimodal porosity and high strength2010Inngår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 201, 253-257 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diatomite powder, a naturally occurring porous raw material, was used to fabricate ceramic materials withbimodal porosity and high strength. The effect of the sintering temperature on the density and porosity ofdry pressed diatomite green bodies was evaluated using mercury porosimetry and water immersionmeasurements. It was found that the intrinsic porosity of the diatomite particles with a pore size around0.2 μm was lost at sintering temperatures above 1200 °C. Maintaining the sintering temperature at around1000 °C resulted in highly porous materials that also displayed a high compressive strength. Microstructuralstudies by scanning electron microscopy and energy-dispersive X-ray analysis suggested that the porecollapse was facilitated by the presence of low melting impurities like Na2O and K2O.

  • 2.
    Andersson, Linnéa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Jones, Anthony C.
    Knackstedt, Mark A.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Permeability, pore connectivity and critical pore throat control of expandable polymeric sphere templated macroporous alumina2011Inngår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 59, nr 3, 1239-1248 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have regulated the permeability in macroporous alumina materials by manipulating the connectivity of the pore phase and the sizes of the smallest constrictions between connected pores. Templating with particle-coated expandable polymeric spheres (EPS) significantly increased the fraction of isolated pore clusters, and reduced both the sizes and the number of connections with neighboring pores, as determined by three-dimensional evaluation with X-ray micro-computed tomography. The stable particle coating, applied onto the EPS surfaces using polyelectrolyte multilayers, reduced the volume expansion and the coalescence of the EPS at elevated temperatures, which reduced the simulated permeability by as much as two orders of magnitude compared to templating with uncoated EPS in materials of similar porosities. We show that the Katz-Thompson model accurately predicts the permeability for the macroporous alumina materials with porosities of 46-76%. This suggests that the permeability to fluid flow in these materials is governed by the smallest constrictions between connected pores: the critical pore throat diameter.

  • 3.
    Andersson, Linnéa
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Jones, Anthony C.
    Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia.
    Knackstedt, Mark A.
    Department of Applied Mathematics, Research School of Physical Sciences and Engineering, Australian National University, Canberra, ACT 0200, Australia.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Three-dimensional structure analysis by X-ray micro-computed tomography of macroporous alumina templated with expandable microspheres2010Inngår i: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 30, nr 12, 2547-2554 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The three-dimensional (3D) structures of macroporous alumina, produced by a novel method that combines gel casting with expandable polymericmicrospheres as a sacrificial templating material, have been characterised by X-ray micro-computed tomography (µ-CT). The grey-scale intensitytomogram data produced by the X-ray µ-CT was segmented into porous and solid phases and the individual pores were identified. We comparedtwo-dimensional slices of the analysed data with the corresponding scanning electron microscopy images and showed that the structural featuresof the pores were well reproduced in the X-ray µ-CT images. 3D visualisations of the pore structure and the pore network were also shown. Theopen porosity obtained from X-ray µ-CT corresponded well with the porosity derived from mercury porosimetry for pores larger than the voxeldimension (3 µm). The quantitative analysis also yielded information on the spatial variations in porosity and the number of connected neighboursof pores. The 3D data was used to relate the calculated permeability to the open porosity.

  • 4. Atluri, Rambabu
    et al.
    Iqbal, Muhammad Naeem
    Bacsik, Zoltan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Villaescusa, Luis Angel
    Garcia-Bennett, Alfonso E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi. alfonso@mmk.su.se.
    Self-Assembly Mechanism of Folate-Templated Mesoporous Silica2013Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, nr 38, 12003-12012 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A method to form ordered mesoporous silica based on the use of folate supramolecular templates has been developed. Evidence based on in situ small-angle X-ray scattering (SAXS), electron microscopy, infrared spectroscopy, and in situ conductivity measurements are used to investigate the organic inorganic interactions and synthesis mechanism. The behavior of folate molecules in solution differs distinctively from that of surfactants commonly used for the preparation of ordered mesoporous silica phases, notably with the absence of a critical micellar concentration. In situ SAXS studies reveal fluctuations in X-ray scattering intensities consistent with the condensation of the silica precursor surrounding the folate template and the growth of the silica mesostructure in the initial stages. High-angle X-ray diffraction shows that the folate template is well-ordered within the pores even after a few minutes of synthesis. Direct structural data for the self-assembly of folates into chiral tetramers within the pores of mesoporous silica provide evidence for the in register stacking of folate tetramers, resulting in a chiral surface of rotated tetramers, with a rotation angle of 30 degrees. Additionally, the self-assembled folates within pores were capable of adsorbing a considerable amount of CO2 gas through the cavity space of the tetramers. The study demonstrates the validity of using a naturally occurring template to produce relevant and functional mesoporous materials.

  • 5.
    Aziz, Baroz
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Bacsik, Zoltán
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Quantification of chemisorption and physisorption of carbon dioxide on porous silica modified by propylamines: Effect of amine density2012Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 159, 42-49 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Detailed molecular aspects of carbon dioxide sorption on porous silica with different amounts of tethered and cross-linked n-propylamine groups were investigated. Infrared spectroscopy was applied to directly quantify physisorbed and chemisorbed CO2 on the amine modified silicas. The fractions of physisorbed CO2 and various chemisorbed species were determined as functions of CO2 pressure and the amine density on the modified silica. Physisorbed CO2 was a minor portion of the total CO2 uptake at low pressures, but it’s contribution increased to ∼35% at 1 bar of CO2 when the propylamine surface density was low or medium (0.87-1.67 NH2/nm2). Chemisorption of CO2 dominated when the propylamine content was high (2.74 NH2/nm2). The quantities of propylammonium propylcarbamate ion pairs increased with increasing propylamine content. At low or medium amine surface densities (0.87-1.67 NH2/nm2) this increase was approximately proportional to the amine density, but the quantity of ion pairs increased very significantly when the propylamine content was high (2.74 NH2/nm2). This dependency on amine density is consistent with the idea that a sufficiently close proximity of propylamine groups allows a formation of ion pairs. The relative fractions of carbamic acid and silylpropylcarbamate were significant for materials on which ion pairs could not form. Furthermore, the quantities of carbamic acid increased with increasing amine densities suggesting that the ion pairs have a role to stabilize the labile carbamic acid through hydrogen bonds.

  • 6.
    Cheung, Ocean
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Bacsik, Zoltán
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Krokidas, Panagiotis
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Mace, Amber
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Laaksonen, Aatto
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    K+ Exchanged Zeolite ZK-4 as a Highly Selective Sorbent for CO22014Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, nr 32, 9682-9690 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adsorbents with high capacity and selectivity for adsorption of CO2 are currently being investigated for applications in adsorption-driven separation of CO2 from flue gas. An adsorbent with a particularly high CO2-over-N-2 selectivity and high capacity was tested here. Zeolite ZK-4 (Si:Al similar to 1.3:1), which had the same structure as zeolite A (LTA), showed a high CO2 capacity of 4.85 mmol/g (273 K, 101 kPa) in its Na+ form. When approximately 26 at % of the extraframework cations were exchanged for K+ (NaK-ZK-4), the material still adsorbed a large amount of CO2 (4.35 mmol/g, 273 K, 101 kPa), but the N-2 uptake became negligible (<0.03 mmol/g, 273 K, 101 kPa). The majority of the CO2 was physisorbed on zeolite ZK-4 as quantified by consecutive volumetric adsorption measurements. The rate of physisorption of CO2 was fast, even for the highly selective sample. The molecular details of the sorption of CO2 were revealed as well. Computer modeling (Monte Carlo, molecular dynamics simulations, and quantum chemical calculations) allowed us to partly predict the behavior of fully K+ exchanged zeolite K-ZK-4 upon adsorption of CO2 and N-2 for Si:Al ratios up to 4:1. Zeolite K-ZK-4 with Si:Al ratios below 23:1 restricted the diffusion of CO2 and N-2 across the cages. These simulations could not probe the delicate details of the molecular sieving of CO2 over N-2. Still, this study indicates that zeolites NaK-ZK-4 and K-ZK-4 could be appealing adsorbents with high CO2 uptake (similar to 4 mmol/g, 101 kPa, 273 K) and a kinetically enhanced CO2-over-N-2 selectivity.

  • 7.
    Cheung, Ocean
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Jie, Su
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zoltán, Bacsik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Jing, Li
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Samain, Louise
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Xiaodong, Zou
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Niklas, Hedin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    CO2 selective NaMg-CTS-1 and its structural formation from the titanium silicate based molecule sieve NaMg-ETS-4 upon dehydration2014Inngår i: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 198, 63-73 s.Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    A range of titanium silicates (ETS-4 and CTS-1) with interesting gas separation properties were studied as CO2 adsorbents. Some of these adsorbents, in particular NaMg-CTS-1, showed the ability to selectively adsorb CO2-over-N2. Partially exchanged NaM-ETS-4 (M = Mg, Ca, Sr and Ba) were synthesised in the Na+ form and ion exchanged with group 2 cations. All but NaBa-ETS-4 transformed into their CTS-1 counterparts, when these partially exchanged Na-ETS-4 were dehydrated. The transformation from ETS-4 to CTS-1 was monitored and studied extensively using diffraction and spectroscopic techniques. Powder X-ray diffraction allowed us to follow the changes of the unit cell parameters occurred at different temperatures. We combined high energy X-ray total scattering (analysed by pair distribution functions – PDF analysis), electron diffraction, infrared, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy to study the transformation of ETS-4 to CTS-1. We understood that under dehydration steps, there was significant disruption to the Ti–O–Ti chain along the b-axis, which occurred concurrently with the distortion of the double 3-rings alongside of these chains. These changes were partly responsible for the contraction of the ETS-4 framework (and successive transformation to CTS-1). The new information allowed us to understand the interesting structures and sorption properties of these adsorbents

  • 8.
    Cheung, Ocean
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Zoltán, Bacsik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Panagiotis, Krokidas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Niklas, Hedin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    CO2 separation properties of high silicon zeolite NaK-ZK-4 with Si:Al up to 2.8:1Manuskript (preprint) (Annet vitenskapelig)
  • 9.
    Cheung, Ocean
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Zoltán, Bacsik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Petr, Vasiliev
    Niklas, Hedin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Carbon dioxide separation from methane on highly selective ion exchanged zeolite NaKCsA – a possible sorbent for biogas upgradingManuskript (preprint) (Annet vitenskapelig)
  • 10.
    Eden, Mattias
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för fysikalisk kemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för oorganisk kemi.
    Jansson, Kjell
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Al and O substitutions in BaS-phases, Ba2AlxSi12-xN16-xO2+x: A TEM, XRD and solid-state NMR study2008Inngår i: Solid State Sciences, ISSN 1293-2558, E-ISSN 1873-3085, Vol. 10, nr 1, 50-60 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a series of Ba-based oxonitrido-silicate S-phases (Ba2AlxSi12-xN16-xO2+x) spanning a compositional range up to x approximate to 3, we examine the incorporation of Al and O by Si-29 and Al-27 magic-angle spinning (MAS) solid state nuclear magnetic resonance (NMR) and Al-27 triple-quantum MAS (3QMAS). The 3QMAS spectra reveal Al-27 signals from two distinct structural environments, assigned to AlN4 or AlN3O tetrahedra, respectively, and with their relative amounts depending on the S-phase substitution parameter x. Si-29 NMR show variable fractions of SiN4 and SiN3O environments. The NMR results accord overall with a structural substitution model for which O enters at one crystallographic position (occupied according to N4-xOx), in conjunction with a random Al for Si substitution at two distinct crystallographic positions. This leads to S-phase frameworks built from SiN4, SiN3O, AlN4 and AlN3O tetrahedra.

  • 11.
    Eriksson, Mirva
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Liu, Yi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Hu, Jiangfeng
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Gao, Lian
    State Key Lab of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai.
    Nygren, Mats
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Transparent hydroxyapatite nanoceramics by high pressure spark plasma sintering at the minimized sintering temperatureManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    For direct observation of the bio-interfacial reactions with improved spatial and temporal resolution by confocal microscopy transparent hydroxyapatite nanoceramics are demanded. The aim of the present study was to, through detailed kinetics study and micostructural characterization, define a processing window within which transparent HAp nanoceramics can be produced by spark plasma sintering of dry powders.  A lab-made hydrothermally processed bulky powder composed of loosely aggregated nanorods and a commercial granulated-powder composed of irregular shaped nanorods were tested.  The use of a high pressure cell allows the application of pressure up to 500 MPa. It was found that applying of high pressure is beneficial for widen up the processing window for attaining dense HAp ceramics with nano grained microstructure. The high transparency of HAp nanoceramics obtained in this study is ascribed to the high density and homogeneous nano-structure achieved besides the unique intrinsic optical properties of the HAp crystal, i.e. its low refractive index and very small birefringence. Achieving full densification at the minimized sintering temperature allows for the first time the preparation of transparent HAp nanoceramics with stoichiometric composition, i.e. avoiding the loss of water that commonly encountered  during the conventional ways of sintering.

  • 12.
    Eriksson, Mirva
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Salamon, David
    Nygren, Mats
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Spark plasma sintering and deformation of Ti-TiB2 composites.2008Inngår i: Materials Science & Engineering, A: Structural Materials: Properties, Microstructure and Processing, ISSN 0921-5093, Vol. 1-2, nr A475, 101-104 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spark plasma sintering (SPS) was used to investigate the densification and deformation behaviour of Ti–TiB2 composites. Fully densified samples were prepared with Ti addition larger than 5%. The prepared composites can be deformed under compression at 1700 °C to achieve a strain of 50% without cracking. At lower temperatures, cracks were initiated due to low ductility of TiB2 and low content of Ti. During the sintering and deformation, TiB is formed via a reaction between Ti and TiB2. To elucidate the formation mechanism of TiB in the SPS process, reactive sintering of TiB using element precursors was also performed. Fully dense samples were prepared but it was not possible to prepare pure uniphase TiB. The reactive sintering resulted in the formation of TiB and TiB2 mixtures at low temperatures and a mixture of TiB2 and Ti3B4 at high temperature

  • 13.
    Eriksson, Mirva
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Yan, Haixue
    School of Engineering and Materials Science, Queen Mary University of London,.
    Nygren, Mats
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Reece, Mike J
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Low temperature consolidated lead-free ferroelectric niobateceramics with improved electrical properties2010Inngår i: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 25, nr 2, 240-247 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a concerted effort to develop lead-free piezoelectric ceramics. ((Na0.5K0.5)NbO3 based ceramics have good electrical properties, and are a potential replacement material for lead zirconate titanate piezoelectric ceramics. In this work a commercial powder based on (Na0.5K0.5)NbO3 with an initial particle size of 260 nm was consolidated by plasma sintering (SPS). To avoid volatilization, high mechanical pressures were used to minimize the densification temperature. It was found that under a uniaxial pressure of 100 MPa, fully densified compacts can be prepared at 850. Ceramics densified at such a low temperature demonstrate an unusually high remanent polarization (30 mC/cm2) and high d33 (146 pC/N). The improved ferroelectric properties are ascribed to the homogeneous, dense, and submicron grained microstructure achieved.

  • 14.
    Eriksson, Mirva
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Yan, Haixue
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Viola, Giuseppe
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Ning, Huanpo
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Gruner, Daniel
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Nygren, Mats
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Reece, Mike
    School of Engineering and Materials Science and Nanoforce Technology Ltd, Queen Mary University of London, London, United Kingdom.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Effect of grain size on ferroelectric domain and electrical properties of submicron sized sodium potassium niobate ceramicsManuskript (preprint) (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Piezoelectric ceramics of the composition Na0.5K0.5NbO3 (NKN) with grain sizes in the range of 0.2 - 1 mm were fabricated by Spark Plasma Sintering using normal pressure dies and a high pressure cell designed for pressures up to 500 MPa  with the purpose of investigating the effect of grain size on domain structures and electrical properties. Optimized processing conditions enabled ceramics of high densities (>99.5%TD) to be made at T≥850°C. It was found that domain size decreases with decreasing grain size and that non-180° ferroelectric domains walls were still visible in 200 nm sized grains. The room temperature dielectric constant firstly increased with decreasing grain size and then decreased in the low grain size regime. The materials with finer grain size displayed a broad ferro-paraelectric phase transition and a depression of the dielectric maximum at the Curie point. They also displayed an increase in the coercive field and approximately unchanged remnant polarization. The material sintered at 850°C represents a very good candidate for lead-free piezoelectric applications, because of its high piezoelectric constant (d33 = 160±2 pC/N).

  • 15.
    Faure, Bertrand
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Lindeløv, Jesper Sæderup
    GEA Niro, GEA Process Engineering A/S, Gladsaxevej 305, 2860 Søborg, Denmark.
    Wahlberg, Michael
    GEA Niro, GEA Process Engineering A/S, Gladsaxevej 305, 2860 Søborg, Denmark.
    Adkins, Nicholas
    Interdisciplinary Research Center in Materials Processing, University of Birmingham, Birmingham, B15 2TT, United Kingdom.
    Jackson, Phil
    Ceram Research Ltd., Queens Road, Penkhull, Stoke-on-Trent, Staffordshire ST4 7LQ, United Kingdom.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Spray drying of TiO2 nanoparticles into redispersible granules2010Inngår i: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 203, nr 2, 384-388 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have demonstrated how titania nanoparticles can be spray-dried to produce redispersible granules. Theevaluation of different dispersants using rheology, particle size and electrokinetic measurements showedthat an anionic carboxylated polyelectrolyte, Dispex N40, was able to stabilize the primary aggregates of thetitania nanoparticles with a size of about 180 nm at an addition of 2.4% dry-weight basis over a relativelylarge pH-range. Transmission electron microscopy showed that the commercial P-25 titania nanopowdercould not be deagglomerated down to the individual crystallite size of 15–40 nm. Spherical granules with asize between 20 and 50 μm and a minimum amount of dusty fines could be produced by spray drying theaqueous titania dispersions in a configuration with internal bag filters. The granules could be completelydisintegrated and redispersed in water by ultrasonication into a stable suspension with a size distributionthat is identical to the as-received powder. The possibility to prepare redispersible nanoparticle granules byspray drying is a route to minimize the risk of airborne exposure and facilitate the handling of nanopowders.

  • 16. Fischer, Christian E.
    et al.
    Mink, Janos
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Hajba, Laszlo
    Bacsik, Zoltan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Nemeth, Csaba
    Mihaly, Judith
    Raith, Alexander
    Cokoja, Mirza
    Kuehn, Fritz E.
    Vibrational spectroscopic study of SiO2-based nanotubes2013Inngår i: Vibrational Spectroscopy, ISSN 0924-2031, E-ISSN 1873-3697, Vol. 66, 104-118 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Novel organic-inorganic hybrid nanotubes containing silica and ethane (EtSNT), ethylene (ESNT) and acetylene (ASNT) units, as well as brominated ESNT (Br-ESNT) and glycine-modified Br-ESNT (Gly-ESNT) have been studied by IR and Raman spectroscopy. The results are compared with the spectral features for conventional silica nanotubes (SNT) and amorphous silica. Bands peculiar to organic moieties have been detected and assigned. Assignment of the silicate backbone vibrations was based on the results of normal coordinate calculations. Furthermore, characteristic silicate, so-called 'nanotube' vibrations have been identified and their band positions have been summarized to serve as a future reference for such compounds. SiOSi antisymmetric stretchings were observed in the range 1000-1110 cm(-1), while the symmetric stretchings appeared between 760 and 960 cm(-1) for EtSNT, ESNT and Br-ESNT. Force constants have been refined for models of the repeating structure units: O3SiOSi(OSi)(3) for SNT and SiCHnCHnSi(OSi)(3) for organosilica nanotubes (n = 2, EtSNT: n = 1, ESNT and n = 0, ASNT). The calculated SiO stretching force constants were increased from 4.79 to 4.88 and 5.11 N cm(-1) for EtSNT, ESNT and ASNT, respectively. The force constants have been compared with those for several silicates and SiO bond length are predicted and discussed.

  • 17.
    Gebauer, Denis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Gunawidjaja, Philips N.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Ko, J. Y. Peter
    Bacsik, Zoltan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Aziz, Baroz
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Liu, Lijia
    Hu, Yongfeng
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Tai, Cheuk-Wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Sham, Tsun-Kong
    Edén, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Proto-Calcite and Proto-Vaterite in Amorphous Calcium Carbonates2010Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 49, nr 47, 8889-8891 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Amorphous order: Amorphous calcium carbonates (ACC) have an intrinsic structure relating to the crystalline polymorphs of calcite and vaterite. The proto-crystalline structures of calcite and vaterite (pc-ACC and pv-ACC) are analyzed by NMR (see picture), IR, and EXAFS spectroscopy, which shows that the structuring of ACC relates to the underlying pH-dependent equilibria.

  • 18.
    Gebauer, Denis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Liu, Xingmin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Aziz, Baroz
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zhao, Zhe
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Porous tablets of crystalline calcium carbonate via sintering of amorphous nanoparticles2013Inngår i: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 15, nr 6, 1257-1263 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Porous tablets of crystalline calcium carbonate were formed upon sintering of a precursor powder of amorphous calcium carbonate (ACC) under compressive stress (20 MPa) at relatively low temperatures (120-400 degrees C), induced by pulsed direct currents. Infrared spectroscopy ascertained the amorphous nature of the precursor powders. At temperatures of 120-350 degrees C and rates of temperature increase of 20-100 degrees C min(-1), the nanoparticles of ACC transformed into crystallites of mainly aragonite, which is generally difficult to achieve using wet-chemicals under kinetic control. The amorphous precursor particles (similar to 10 nm) transformed into crystallites (similar to 30-50 nm) during sintering. Consistently, the specific surface areas of 140-160 m(2) g(-1) for the precursor particles were reduced to 10-20 m(2) g(-1) for the porous tablets. The porous network within the tablets consisted of fused aragonite and vaterite particles in a ratio of similar to 80 : 20. The fraction of aragonite to vaterite was invariant to the temperature and rate of temperature change used. The particle size increased only to a small amount on an increased rate of temperature change. At temperatures above 400 degrees C, porous tablets of calcite formed. The later transformation was under thermodynamic control, and led to a minor reduction of the specific surface area. The size of the crystallites remained small and the transformation to calcite appeared to be a solid-state transformation. Porous, template-and binder-free tablets of calcium carbonate could find applications in for example, biology or water treatment.

  • 19.
    Gebauer, Denis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Oliynyk, Vitaliy
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Salajkova, Michaela
    Sort, Jordi
    Zhou, Qi
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    A transparent hybrid of nanocrystalline cellulose and amorphous calcium carbonate nanoparticles2011Inngår i: NANOSCALE, ISSN 2040-3364, Vol. 3, nr 9, 3563-3566 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nanocellulose hybrids are promising candidates for biodegradable multifunctional materials. Hybrids of nanocrystalline cellulose (NCC) and amorphous calcium carbonate (ACC) nanoparticles were obtained through a facile chemical approach over a wide range of compositions. Controlling the interactions between NCC and ACC results in hard, transparent structures with tunable composition, homogeneity and anisotropy.

  • 20.
    Grüner, Daniel
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Shen, Zhijian James
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Ordered coalescence of nano-crystals during rapid solidification of ceramic melts2011Inngår i: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 13, nr 17, 5303-5305 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Rapid cooling of an aluminosilicate-zirconia melt after laser sintering results in the formation of zirconia nano-crystals and dendritic zirconia crystals embedded in a glass matrix. The nano-crystals act as building blocks for the formation of non-faceted secondary crystals. Several secondary crystals built from two or a few nano-crystals with perfect structural coherence across the interface have been observed. Thus, the earliest states of these secondary crystals have been preserved by rapid cooling. Crystal growth can be described by a mechanism, ordered coalescence, which is characterized by self-assembly of nano-crystals combined with atom-by-atom growth and links classical and non-classical crystallization.

  • 21. Hodgkins, Robert P.
    et al.
    Ahniyaz, Anwar
    Parekh, Kinnari
    Belova, Lyubov M.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Maghemite nanocrystal impregnation by hydrophobic surface modification of mesoporous silica2007Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 23, nr 17, 8838-8844 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here, we report the design of a hybrid inorganic/organic mesoporous material through simultaneous pore engineering and hydrophobic surface modification of the intramesochannels to improve the uptake of superparamagnetic maghemite nanocrystals via impregnation techniques. The mesoporous material of the SBA-15 type was functionalized in situ with thiol organo-siloxane groups. Restricting the addition of the thiol organo-siloxane to 2 mol % yielded an inorganic/organic hybrid material characterized by large pores and a well-ordered hexagonal p6mm mesophase. The hydrophobic surface modification promoted the incorporation of 7.5 nm maghemite (gamma-Fe2O3) nanocrystals, prepared through temperature-control led decomposition of iron pentacarbonyl in organic solvents. The hydrophobic, oleic acid capped superparamagnetic maghemite nanocrystals were incorporated into the porous network via wet impregnation from organic suspensions. Combining diffraction, microscopy, and adsorption data confirmed the uptake of the nanocrystals within the intramesochannels of the silica host. Magnetization dependencies on magnetic field at different temperatures show a constriction in the loop around the origin, which indicates immobilization of maghemite nanocrystals inside the thiol-functionalized silica host.

  • 22. Jiang, Q. H.
    et al.
    Liu, F. T.
    Nan, Ce-Wen
    Lin, Yuan-Hua
    Reece, M. J.
    Yan, H. X.
    Ning, H. P.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    High-temperature ferroelectric phase transition observed in multiferroic Bi0.91La0.05Tb0.04FeO32009Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, nr 1, 12909- s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A single-phase Bi0.91La0.05Tb0.04FeO3 polycrystalline ceramic was fabricated by spark-plasma-sintering the precursor powder prepared by a sol-gel method. Temperature-dependent properties of polycrystalline Bi0.91La0.05Tb0.04FeO3 were characterized by x-ray diffraction, dielectric, and piezoelectric measurement. The x-ray diffraction results revealed a phase transition near 700 degrees C. Especially, temperature-dependent dielectric behavior demonstrated that there was a dielectric abnormal peak at about 697 degrees C, in addition to those two well-known dielectric abnormal peaks at 337 degrees C (Neel temperature) and 831 degrees C (Curie temperature). The observations, together with thermal depoled behavior, suggest a ferroelectric-ferroelectric phase transition from R(3)c to Pbnm at around 700 degrees C.

  • 23. Jiang, Qing-Hui
    et al.
    Mei, Ao
    Lin, Yuan-Hua
    Nan, Ce-Wen
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Ferroic properties of highly dense multiferroic Bi1-xLa0.05TbxFeO3 ceramics via sheltered spark plasma sintering2008Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 91, nr 7, 2189-2194 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Multiferroic Bi0.95-xLa0.05TbxFeO3 (BLTFO) ceramics were prepared by spark plasma sintering. The protection of CeO2 powders in the spark plasma sintering process can effectively restrain the valence fluctuation of iron ions and high-dense BLTFO ceramics with good dielectric and ferroelectric properties are fabricated. The BLTFO ceramics have low loss (tan delta similar to 5%) between 10(2) and 10(6) Hz. The doping of Tb can increase the dielectric and ferromagnetic properties, but decrease the ferroelectricity of BLTFO ceramics.

  • 24. Kamba, S.
    et al.
    Nuzhnyy, D.
    Vanek, P.
    Savinov, M.
    Knizek, K.
    Shen, Z.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Santava, E.
    Maca, K.
    Sadowski, M.
    Petzelt, J.
    Magnetodielectric effect and optic soft mode behaviour in quantum paraelectric EuTiO3 ceramics2007Inngår i: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 80, nr 2, 27002- s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Infrared reflectivity and time-domain terahertz transmission spectra of EuTiO3 ceramics revealed a polar optic phonon at 6-300K whose softening is fully responsible for the recently observed quantum paraelectric behaviour. Even if our EuTiO3 ceramics show lower permittivity than the single crystal due to a reduced density and/ or small amount of secondary pyrochlore Eu2Ti2O7 phase, we confirmed a magnetic field dependence of the permittivity, also slightly smaller than in single crystal. An attempt to reveal the soft phonon dependence at 1.8K on the magnetic field up to 13T remained below the accuracy of our infrared reflectivity experiment.

  • 25.
    Kocjan, Andraz
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi. Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, Stockholm.
    Dakskobler, Ales
    Budic, Bojan
    Kosmac, Tomaz
    Suppressed Reactivity of AlN Powder in Water at 5 degrees C2013Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 96, nr 4, 1032-1034 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The hydrolysis behavior of AlN powder suspensions (525wt%) at 5 degrees C has been investigated to explore the impact of low temperatures on the hydrolysis behavior. Throughout the 312-h long experiment, the pH value of the suspensions was below 9, where the hydrolysis remained in the induction period and was eventually suppressed due to the formation of a few-nanometers-thick film of amorphous aluminum hydroxide gel around the AlN particles, acting as a passivation layer. Moreover, the aqueous part of the suspension possessed a remarkably high value of dissolved [Al(III)]aq, being an order of magnitude higher at a given pH value than the aqueous AlCl3 solution.

  • 26. Krycka, K. L.
    et al.
    Borchers, J. A.
    Laver, M.
    Salazar Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Lopez-Ortega, A.
    Estrader, M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Surinach, S.
    Baro, M. D.
    Sort, J.
    Nogues, J.
    Correlating material-specific layers and magnetic distributions within onion-like Fe3O4/MnO/gamma-Mn2O3 core/shell nanoparticles2013Inngår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 17, 17B531- s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The magnetic responses of two nanoparticle systems comprised of Fe3O4/gamma-Mn2O3 (soft ferrimagnetic, FM/hard FM) and Fe3O4/MnO/gamma-Mn2O3 (soft FM/antiferromagnetic, AFM/hard FM) are compared, where the MnO serves to physically decouple the FM layers. Variation in the temperature and applied field allows for Small Angle Neutron Scattering (SANS) measurements of the magnetic moments both parallel and perpendicular to an applied field. Data for the bilayer particle indicate that the graded ferrimagnetic layers are coupled and respond to the field as a single unit. For the trilayer nanoparticles, magnetometry suggests a Curie temperature (T-C) approximate to 40 K for the outer gamma-Mn2O3 component, yet SANS reveals an increase in the magnetization associated with outer layer that is perpendicular to the applied field above T-C during magnetic reversal. This result suggests that the gamma-Mn2O3 magnetically reorients relative to the applied field as the temperature is increased above 40 K.

  • 27.
    Lin, C.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Xiao, Changhong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Shen, Zhijian James
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Nano Pores Evolution in Hydroxyapatite Microsphere during Spark Plasma Sintering2011Inngår i: Science of Sintering, ISSN 0350-820X, Vol. 43, nr 1, 39-46 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Micron-spherical granules of hydroxyapatite (HAp) nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  • 28.
    Ma, Jing
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Zhang, Junzhan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Liu, Wei
    Shen, Zhijian James
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Suppressing pore-boundary separation during spark plasma sintering of tungsten2013Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 438, nr 1-3, 199-203 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A tungsten powder with bimodal particle size distribution is consolidated by spark plasma sintering (SPS). Effects are made for understanding the densification and grain growth mechanisms and their relations to the SPS processing parameters. By holding the sample at an intermediate temperature, i.e., 1200 degrees C for 5 min, where the densification is enhanced by particle close packing, the pore-boundary separation that yields the formation of entrapped pores inside individual grains at final stage of sintering is suppressed. This optimization of the SPS process is beneficial for preparing fine grained bulk tungsten with homogeneous microstructure from the powders produced in industrial-scale. The prepared tungsten with minimized porosity appears a potential candidate for plasma-facing materials in the divertor region in the International Thermonuclear Experimental Reactor (ITER).

  • 29.
    Mathew, Renny
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Turdean-Ionescu, Claudia
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Stevensson, Baltzar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Izquierdo-Barba, Isabel
    Garcia, Ana
    Arcos, Daniel
    Vallet-Regi, Maria
    Eden, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Direct Probing of the Phosphate-Ion Distribution in Bioactive Silicate Glasses by Solid-State NMR: Evidence for Transitions between Random/Clustered Scenarios2013Inngår i: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, nr 9, 1877-1885 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By employing P-31 multiple-quantum coherence-based solid-state nuclear magnetic resonance spectroscopy, we present the first comprehensive experimental assessment of the nature of the orthophosphate ion distributions in silicate based bioactive glasses (BGs). Results are provided both from melt prepared BG and evaporation-induced self-assembly-derived mesoporous bioactive glass (MEBG) structures of distinct compositions. The phosphate species are randomly dispersed in melt-derived BGs (comprising 44-55 mol % SiO2) of the Na2O-CaO-SiO2-P2O5 system, whereas a Si-rich (86 mol % SiO2) and Ca-poor ordered MBG structure exhibits nanometer-sized amorphous calcium phosphate clusters, conservatively estimated to comprise at least nine orthophosphate groups. A Ca-richer MBG (58 mol % SiO2) reveals a less pronounced phosphate clustering. We rationalize the variable structural role of P in these amorphous biomatetials.

  • 30. Mayerhoefer, Thomas G.
    et al.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    SUBLeonova, Ekaterina
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för fysikalisk kemi.
    Eden, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, Avdelningen för fysikalisk kemi.
    Kriltz, Antje
    Popp, Juergen
    Consolidated silica glass from nanoparticles2008Inngår i: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 181, nr 9, 2442-2447 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dense silica glass was prepared by consolidating a highly dispersed silicic acid powder (particle size < 10 nm) with the Spark Plasma Sintering (SPS) technique. The glass was characterized by ellipsometry, transmission electron microscopy (TEM), infrared reflectance and transmittance spectroscopy, as well as by Raman, UV-Vis-NIR and solid-state nuclear magnetic resonance (NMR) spectroscopy. The prototypic sample showed a transmittance of about 63% compared to silica glass in the UV-Vis spectral range. Based on the results of infrared transmittance spectroscopy this lower transparency is due to the comparably high water content, which is about 40 times higher than that in silica glass. H-1 magic-angle spinning (MAS) NMR confirmed an increase in hydroxyl groups in tie sample prepared by SPS relative to that of the conventional SiO2 reference glass. Aside from the comparably high water content, we conclude from the similarity of the IR-reflectance and the Si-29 MAS NMR spectra of the SPS sample and the corresponding spectra of the conventionally prepared silica glass, that the short- and medium-range order is virtually the same in both materials. Raman spectroscopy, however, Suggests that the number of three- and four-membered rings is significantly smaller in the SPS sample compared to the conventionally prepared sample. Based on these results we conclude that it is possible to prepare glasses by compacting amorphous powders by the SPS process. The SPS process may therefore enable the preparation of glasses with compositions inaccessible by conventional methods. 

  • 31.
    Mille, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Corkery, Robert W.
    KTH Royal Inst Technol, Div Phys Chem, Dept Chem, Stockholm.
    A structural and thermal conductivity study of highly porous, hierarchical polyhedral nanofoam shells made by condensing silica in microemulsion films on the surface of emulsified oil drops2013Inngår i: Journall of Material Chemistry A, ISSN 2050-7488, Vol. 1, nr 5, 1849-1859 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Light-weight solid foams are utilized in applications such as packaging and insulation mainly due to their intrinsically high porosity, low relative density and associated mechanical and transport properties. Here hollow core spherical shells are prepared with walls made of a polyhedral silica nanofoam with open cells. A microemulsion film at the oil-water interface of oil droplets is used as a soft structural template for the condensation of soluble silica species. The microemulsion sets the length scale of the monodisperse silica nanofoam cells, and the emulsion droplets set the micron-scale dimensions of the polydisperse spherical shells. Porosity is achieved by removing the templates and oils, leaving pure low-density silica. This results in a hierarchically structured, highly porous shell foam material that packs into beds with a measured porosity of approximately 97.3%, well into the range of silica aerogels. Using a combination of electron microscopy, small-angle synchrotron X-ray diffraction and nitrogen physisorption, an accurate structural model for the nanofoam shells is constructed. The material is shown to be comprised of open-cell foams that are structurally analogous to dry polyhedral soap froths having minimal surface partitions, and Plateau boundaries. The primary polyhedral nanofoam cells are 30 nm in diameter connected by 7 nm cylindrical windows. These nanofoams form spherical monolithic shells with volume average mean diameter of 41 microns and shell thickness of 0.7 microns. Simple models for the thermal conductivity of these nanofoam shell materials are constructed that include accounting for the nanoscale effects on gaseous and solid thermal conductivity. These are compared to the measured value of 0.041 W m(-1) K-1. These materials represent new structures in the family of self-assembled, highly porous silica materials and are potentially useful in packaging and insulation and other applications due to their light weight and/or intrinsically low thermal conductivity and associated mechanical and transport properties.

  • 32.
    Mille, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Tyrode, Eric C.
    Corkery, Robert W.
    3d titania photonic crystals replicated from gyroid structures in butterfly wing scales: approaching full band gaps at visible wavelengths2013Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 3, nr 9, 3109-3117 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    3D titania photonic crystals are replicated from single gyroid structures found in the butterfly Callophrys rubi. Photonic crystals were characterised using SEM imaging, X-ray and Raman scattering and reflection spectroscopy. The overall symmetry and topology of the original single gyroid structures is replicated with high fidelity. Titania replicas display photonic responses that are thermal history dependent. Replicas treated at 700 degrees C, show up to 96% reflectivity at similar to 505 nm, while at lower and higher treatment temperatures the photonic response was not as pronounced. Simulated band structures fitted to the observed spectral reflectivity data constrain the solid volume fractions and dielectric constants of the replicas. The titania photonic crystals were also found to be optically active, with both left- and right-handed single gyroids contributing to the chiral response. The 3D titania photonic crystals replicated here have nearly complete overlapping of partial band gaps, strongly suggesting that materials with full photonic band gaps are experimentally within reach using the general replication approach reported here.

  • 33.
    Mille, Christian
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Tyrode, Eric C.
    Corkery, Robert W.
    Stockholms universitet.
    Inorganic chiral 3-D photonic crystals with bicontinuous gyroid structure replicated from butterfly wing scales2011Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, nr 35, 9873-9875 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three dimensional silica photonic crystals with the gyroid minimal surface structure have been synthesized. The butterfly Callophrys rubi was used as a biotemplate. This material represents a significant addition to the small family of synthetic bicontinuous photonic crystals.

  • 34.
    Oliynyk, Vitaliy
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Mille, Christian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Ng, Jovice B. S.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    von Ballmoos, Christoph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Corkery, Robert W.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Selective and atp driven transport of ions across supported membranes into nanoporous carriers using gramicidin a and atp synthase2013Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, nr 8, 2733-2740 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a robust and versatile membrane protein based system for selective uptake and release of ions from nanoporous particles sealed with ion-tight lipid bilayers of various compositions that is driven by the addition of ATP or a chemical potential gradient. We have successfully incorporated both a passive ion channel-type peptide (gramicidin A) and a more complex primary sodium ion transporter (ATP synthase) into the supported lipid bilayers on solid nanoporous silica particles. Protein-mediated controlled release/uptake of sodium ions across the ion-tight lipid bilayer seal from or into the nanoporous silica carrier was imaged in real time using a confocal laser scanning microscope and the intensity changes were quantified. ATP-driven transport of sodium ions across the supported lipid bilayer against a chemical gradient was demonstrated. The possibility of designing durable carriers with tight lipid membranes, containing membrane proteins for selective ion uptake and release, offers new possibilities for functional studies of single or cascading membrane protein systems and could also be used as biomimetic microreactors for controlled synthesis of inorganic multicomponent materials.

  • 35. Petkov, V.
    et al.
    Buscaglia, V.
    Buscaglia, M. T.
    Zhao, Zhe
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Ren, Y.
    Structural coherence and ferroelectricity decay in submicron- and nano-sized perovskites2008Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, nr 5, 54107- s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Understanding the loss of ferroelectricity in submicron- and nano-sized perovskites is an issue that has been debated for decades. Here we report results from a high-energy x-ray diffraction (XRD) study on a prime example of the perovskite's family, BaTiO3 ceramics with a grain size ranging from 1200 to 5 nm. We find that the loss of ferroelectricity in submicron- and nano-sized BaTiO3 has an intrinsic origin related to the increased atomic positional disorder in spatially confined physical systems. Our results imply that no particular critical size at which ferroelectricity in BaTO3, in particular, and perovskites, in general, is completely lost exists. Rather it weakens exponentially with the decreasing of their physical size. Smart technological solutions are needed to bring it back.

  • 36. Petzelt, J.
    et al.
    Ostapchuk, T.
    Gregora, I.
    Nuzhnyy, D.
    Rychetsky, I.
    Maca, K.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Grain boundary and size effect on the dielectric, infrared and Raman response of SrTiO3 nanograin ceramics2008Inngår i: Ferroelectrics (Print), ISSN 0015-0193, E-ISSN 1563-5112, Vol. 363, 227-244 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The recently revealed giant grain size effect on dielectric properties in undoped SrTiO3 ceramics (J. Petzelt et al., J. Phys.: Con dens. Matter 19, 196222 (2007) and references therein), was extended to smaller grains of 80 nm mean grain size. Like for previously studied ceramics with larger grain size, in addition to dielectric permittivity also the infrared and Raman responses were studied and discussed. It was shown that the reduced effective permittivity is fully accounted for by the infrared soft mode behaviour and, similar to single crystals and other ceramics studied, no dielectric dispersion appears below the THz frequency range. The rather universal (independent of the grain size and sintering process) double dead layer structure was proposed to be responsible for the observed changes in the infrared and Raman spectra, allowing the grain core to keep the single crystal dielectric function. The outer dead layer shell (obviously charged due to an oxygen deficit) is very thin (similar to 1 nm) having frequency and temperature independent low permittivity (similar to 10) and is responsible for the static permittivity suppression. The inner layer of only slightly distorted perovskite structure is polar with local polarization normal to grain boundaries gradually decreasing towards the grain centre. This polarization and/or the thickness of the polar layers, which compensate the charged grain boundaries, appear to increase on decreasing temperature, particularly below the structural phase transition. Its nature is still not fully understood. In agreement with our previous suggestions, from the Raman data it con be also concluded that in the low-temperature tetragonal phase of all SrTiO3 ceramics, the local tetragonal axes tend perpendicular to the grain boundaries and the tetragonality is strongly reduced compared to single crystals.

  • 37.
    Salamon, David
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Maca, Karel
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Rapid sintering of crack free zirconia ceramics by pressure less spark plasma sintering2012Inngår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 66, nr 11, 899-902 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Heating of a ceramic green body is a key step in sintering. We have created inside a spark plasma sintering apparatus pressure-less sintering conditions that allow homogeneous and extremely rapid heating. Dense and crack-free zirconia ceramic was sintered at heating rates of up to 500 degrees C min(-1) and dwell times of 2 min. This extremely fast sintering process is accompanied by extremely rapid grain growth, indicating a non classical sintering mechanism. No grain size gradients were observed inside the sintered zirconia ceramics.

  • 38.
    Salazar-Alvarez, German
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Lidbaum, Hans
    Lopez-Ortega, Alberto
    Estrader, Marta
    Leifer, Klaus
    Sort, Jordi
    Surinach, Santiago
    Dolors Baro, Maria
    Nogues, Josep
    Two-, Three-, and Four-Component Magnetic Multilayer Onion Nanoparticles Based on Iron Oxides and Manganese Oxides2011Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, nr 42, 16738-16741 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Magnetic multilayered, onion-like, hetero-structured nanoparticles are interesting model systems for studying magnetic exchange coupling phenomena. In this work, we synthesized heterostructured magnetic nanopartides composed of two, three, or four components using iron oxide seeds for the subsequent deposition of manganese oxide. The MnO layer was allowed either to passivate fully in air to form an outer layer of Mn(3)O(4) or to oxidize partially to form MnO vertical bar Mn(3)O(4) double layers. Through control of the degree of passivation of the seeds, particles with up to four different magnetic layers can be obtained (i.e., FeO vertical bar Fe(3)O(4)vertical bar MnO vertical bar Mn(3)O(4)). Magnetic characterization of the samples confirmed the presence of the different magnetic layers.

  • 39. Taninnat, Rashainbunyawat
    et al.
    Cheung, Ocean
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Niklas, Hedin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Spherical aggregates of microporous aluminum phosphates and silicoaluminophosphates and effects of non-traditional mechanism of crystallizationManuskript (preprint) (Annet vitenskapelig)
  • 40.
    Tengå, Andreas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Lidin, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Belieres, Jean-Philippe
    Department of Chemistry and Biochemistry, Arizona State University.
    Newman, Nathan
    School of Materials, Arizona State University.
    Wu, Yang
    Department of Chemistry and Biochemistry, Arizona State University.
    Häussermann, Ulrich
    Department of Chemistry and Biochemistry, Arizona State University.
    Cd13-xInySb10 (x ≈ 2.7, y ≈ 1.5): An interstitial-free variant of thermoelectric β-Zn4Sb32009Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, nr 27, 6704-6710 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Cd13-xInySb10 (x ≈ 2.7, y ≈ 1.5) was synthesized in the form of mm-sized crystals from reaction mixtures containing excess cadmium. The intermetallic compound crystallizes in the rhombohedral space group R-3m with a = 12.9704(4), c = 12.9443(5) Å, V = 1886.0(1), Z = 3 and is isostructural to thermoelectric β-Zn4Sb3 and β-Cd4Sb3. However, in contrast to the latter compounds Cd13-xInySb10 is free from interstitial atoms and does not display any temperature polymorphism. The electrical resistivity of Cd13-xInySb10 is considerably higher than that of Zn4Sb3 and Cd4Sb3 although the temperature behavior remains that of a metal. The thermal conductivity of Cd13-xInySb10 is low, with room temperature magnitudes around 0.8 Wm-1K-1, which is comparable to disordered or complex structured Cd4Sb3 and Zn4Sb3.

  • 41.
    Tengå, Andreas
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Lidin, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Belieres, Jean-Philippe
    Department of Chemistry and Biochemistry, Arizona State University.
    Newman, Nathan
    School of Materials, Arizona State University.
    Wu, Yang
    Department of Chemistry and Biochemistry, Arizona State University.
    Häussermann, Ulrich
    Department of Chemistry and Biochemistry, Arizona State University,.
    Metastable Cd4Sb3: A Complex Structured Intermetallic Compound with Semiconductor Properties2009Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, nr 46, 15564-15572 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The metastable binary intermetallic compound Cd4Sb3 was obtained as polycrystalline ingot by quenching stoichiometric Cd-Sb melts and as mm-sized crystals by employing Bi or Sn fluxes. The compound crystallizes in the monoclinic space group Pn with a = 11.4975(5) Å, b = 26.126(1) Å, c = 26.122(1) Å, b = 100.77(1)o and V = 7708.2(5) Å3. The actual formula unit of Cd4Sb3 is Cd13Sb10 and the unit cell contains 156 Cd and 120 Sb atoms (Z = 12). Cd4Sb3 displays a reversible order-disorder transition at 373 K and decomposes exothermically into a mixture of elemental Cd and CdSb at around 520 K. Disordered β-Cd4Sb3 is rhombohedral (space group R-3c, a ≈ 13.04 Å, c ≈ 13.03 Å) with a framework isostructural to β-Zn4Sb3. The structure of monoclinic α-Cd4Sb3 bears resemblance to the low-temperature modifications of Zn4Sb3, α- and α’-Zn4Sb3, in that randomly distributed vacancies and interstitial atoms of the high-temperature modification aggregate and order into distinct arrays. However, the nature of aggregation and distribution of aggregates is different in the two systems. Cd4Sb3 displays the properties of a narrow gap semiconductor. Between 10 and 350 K the resistivity of melt-quenched samples first increases with increasing temperature until a maximum value at 250 K and then decreases again. The resistivity maximum is accompanied with a discontinuity in the thermopower, which is positive and increasing from 10 to 350 K. The room temperature values of the resistivity and thermopower are about 25 mWcm and 160 mV/K, respectively. Flux synthesized samples show altered properties due to the incorporation of small amounts of Bi or Sn (less than 1 at. %). Thermopower and resistivity appear drastically increased for Sn doped samples. Characteristic for Cd4Sb3 samples is their low thermal conductivity, which drops below 1 W/mK above 130 K and attains values around 0.75 W/mK at room temperature, which is comparable to vitreous materials.

  • 42. Thormann, Esben
    et al.
    Mizuno, Hiroyasu
    Jansson, Kjell
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Hedin, Niklas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Soledad Fernandez, M.
    Luis Arias, Jose
    Rutland, Mark W.
    Pai, Ranjith Krishna
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Embedded proteins and sacrificial bonds provide the strong adhesive properties of gastroliths2012Inngår i: NANOSCALE, ISSN 2040-3364, Vol. 4, nr 13, 3910-3916 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The adhesive properties of gastroliths from a freshwater crayfish (Cherax quadricarinatus) were quantified by colloidal probe atomic force microscopy (AFM) between heavily demineralized gastrolith microparticles and gastrolith substrates of different composition. Combined AFM and transmission electron microscopy studies demonstrated that the sequential detachment and large adhesion energies that characterise the adhesive behaviour of a native gastrolith substrate are dominated by sacrificial bonds between chitin fibres and between chitin fibres and CaCO3. The sacrificial bonds were shown to be strongly related to the gastrolith proteins and when the majority of these proteins were removed by ethylenediaminetetraacetic acid (EDTA), the sequential detachment disappeared and the adhesive energy was reduced by more than two orders of magnitude.

  • 43. Trunec, Martin
    et al.
    Maca, Karel
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Warm pressing of zirconia nanoparticles by the spark plasma sintering technique2008Inngår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 59, nr 1, 23-26 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Zirconia nanoparticles were densified by pressureless sintering and spark plasma sintering (SPS). The evolution of relative density and pore size distribution in powder compacts during these sintering processes were compared. It was found that pore size increase was suppressed during SPS and that this facilitated the densification. The combined sintering process (low-temperature pre-sintering by SPS followed by pressureless sintering) was performed to confirm the advantage of the low-temperature SPS technique (referred to as SPS warm pressing). 

  • 44.
    Vasiliev, Petr Olegovich
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Akhtar, Farid
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Mouzon, Johanne
    Department of Applied Chemistry and Geosciences, Division of Chemical Engineering, Luleå University of Technology.
    Andersson, Charlotte
    Department of Applied Chemistry and Geosciences, Division of Chemical Engineering, Luleå University of Technology.
    Hedlund, Jonas
    Department of Applied Chemistry and Geosciences, Division of Chemical Engineering, Luleå University of Technology.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Strong Hierarchically Porous Monoliths byPulsed Current Processing of Zeolite PowderAssemblies2010Inngår i: American Chemical Society, ISSN 1944-8244, Vol. 2, nr 3, 732-737 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Binderless hierarchically porous monoliths have been produced from silicalite-1 and ZSM-5 zeolite powders by a rapidand facile powder processing method where the zeolite powders are assembled in a graphite die and subjected simultaneously to acompressive pressure and a pulsed current. Pulsed current processing (PCP) or, as it is commonly called, spark plasma sintering,enables rapid thermal processing of zeolite powder assemblies with heating and cooling rates at 100 °C/minute or more, which resultsin the formation of strong powder bodies without any addition of secondary binders. Nitrogen adsorption measurements show thatit is possible to form strong zeolite monoliths by PCP that maintain between 85 and 95% of the surface area of the as-received silicalite-1and ZSM-5 powders. Line-broadening analysis of X-ray powder diffraction data by the Rietveld method and high-resolution electronmicroscopy showed that the formation of strong interparticle bonds is associated with a local amorphization reaction at the interfacialcontact points between the zeolite particles. The PCP-treated binderless ZSM-5 monoliths display a high selectivity in xylene isomerseparation.

  • 45.
    Verho, Oscar
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kärkäs, Markus
    Åkermark, Torbjörn
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Johnston, Eric V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Gustafson, Karl
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Tai, Cheuk-Wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Svengren, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Åkermark, Björn
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Well-Defined Palladium Nanoparticles Supported on Amino-Functionalized Siliceous Mesocellular Foam: An Efficient Heterogeneous Catalyst for Chemically-Induced H2O OxidationManuskript (preprint) (Annet vitenskapelig)
  • 46.
    Wetterskog, Erik
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Tai, Cheuk-Wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Grins, Jekabs
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Bergström, Lennart
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Strain relief during stepwise oxidation of monodisperse Fe1-xO/Fe3-xO4 nanocubes. Influence on their structure and magnetic properties.2011Konferansepaper (Annet vitenskapelig)
  • 47.
    Wicklein, Bernd
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Aranda, Pilar
    Ruiz-Hitzky, Eduardo
    Darder, Margarita
    Hierarchically structured bioactive foams based on polyvinyl alcohol-sepiolite nanocomposites2013Inngår i: Journal of Materials Chemistry B, ISSN 2050-750X, Vol. 1, nr 23, 2911-2920 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hierarchically structured polymer-clay foams comprised of sepiolite and polyvinyl alcohol (PVA) are functionalized with enzymatic and conductive properties to be employed as bioreactors and 3D bioelectrodes. The concept of nanoarchitectonics was followed in the design of this hierarchical and multifunctional cellular material through tailoring of the properties at different length scales, interfacial properties of the sepiolite fibres through adsorption of lipid molecules, bioactivity by supramolecular assembly of urease enzymes on the sepiolite-lipid bio-nanohybrid, and meso- and macroporosity controlled by incorporation of the clay fibres into a PVA matrix, and further cross-linking with borax and ice-templating. The resultant bionanocomposite foams show high structural integrity, tailored multi-level porosity, and biocompatibility which is manifested in sustained enzymatic activity. Exploratory studies show that additional doping with carbon black rendered conductive foams that could hence find usage in bioelectrocatalysis.

  • 48.
    Wicklein, Bernd
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi. KTH, Wallenberg Wood Sci Ctr, SE-10044 Stockholm.
    Salazar-Alvarez, German
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi. KTH, Wallenberg Wood Sci Ctr, SE-10044 Stockholm.
    Functional hybrids based on biogenic nanofibrils and inorganic nanomaterials2013Inngår i: JOURNAL OF MATERIALS CHEMISTRY A, ISSN 2050-7488, Vol. 1, nr 18, 5469-5478 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This feature article reviews some of the recent work on the fabrication of functional hybrids based on biogenic nanofibers and inorganic nanomaterials with an emphasis on their functional properties and suggested potential applications. We also discuss some of the work oriented towards the formation of ordered materials in the pursuit of achieving a hierarchical construction. Besides the academic interest in biogenic nanomaterials, it is anticipated that the use of natural, abundant nanomaterials, e.g., cellulose, chitin, collagen, and silk, could provide affordable functional nanomaterials in developing countries.

  • 49.
    Wu, Yang
    et al.
    Department of Chemistry and Biochemistry, Arizona State University.
    Lidin, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Tengå, Andreas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Newman, Nathan
    School of Materials, Arizona State University.
    Häussermann, Ulrich
    Department of Chemistry and Biochemistry, Arizona State University.
    Phase relations and structural properties of the ternary narrow gap semiconductors Zn5Sb4In2-δ (δ = 0.15) and Zn9Sb6In22010Inngår i: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 183, nr 7, 1574-1581 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A systematic study of the Zn-rich corner of the ternary system Zn-Sb-In revealed the presence of two ternary compounds, stable Zn5Sb4In2-δ(δ = 0.15) and metastable Zn9Sb6In2, with closely related crystal structures. Their common motif is a tetragonal basic structure of 32434 nets formed by the Sb atoms that are stacked in antiposition to yield layers of square antiprisms sharing edges plus intervening tetracapped tetrahedra (tetreadersterns). The majority of Zn atoms occupy peripheral tetrahedra of such tetraedersterns which produces frameworks with a composition “ZnSb”. These frameworks represent orthorhombic superstructures, (2×1×1) for Zn5Sb4In2-δ (Z = 4) and (2×3×1) for Zn9Sb6In2 (Z = 8), with respect to the tetragonal arrangement of Sb atoms. The In and remaining Zn atoms are distributed in the channels formed by the square antiprisms. Phase relations in the Zn-Sb-In system are complex. Crystals of metastable Zn9Sb6In2 are regularly intergrown with various amounts of Zn5Sb4In2-δ. Additionally, a monoclinic variant to orthorhombic Zn9Sb6In2 could be identified. Zn9Sb6In2 decomposes exothermically into a mixture of Zn5Sb4In2-δ, Zn4Sb3 and elemental Zn at around 480 K. Both Zn5Sb4In2-δ and Zn9Sb6In2 are poor metals with resistivity values that are characteristic of heavily doped or degenerate semiconductors (0.2 to 3 mW cm at room temperature).

  • 50.
    Xiong, Yan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Hu, Jianfeng
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för oorganisk kemi och strukturkemi.
    Shen, Zhijian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för materialkemi.
    Pouchly, Vaclav
    Maca, Karel
    Preparation of Transparent Nanoceramics by Suppressing Pore Coalescence2011Inngår i: Journal of The American Ceramic Society, ISSN 0002-7820, E-ISSN 1551-2916, Vol. 94, nr 12, 4269-4273 s.Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Microstructural developments in nanoceramics were investigated in 3Y-TZP compacts with relative density (RD) exceeding 93%. Special attentions were paid to the evolutions of pore structures. It was found that the densification process of nanoceramic compacts with apparently close porosity was greatly jeopardized by pore coalescence. This observation was interpreted by the coalescence of locally interconnected pores originated from inhomogeneous packing of particles. The pore coalescence can be suppressed by application of an external pressure. The processing principle was demonstrated by spark plasma sintering (SPS) with extended holding at a minimized sintering temperature. The highly dense 3Y-TZP nanoceramics containing no large pores became optically transparent.

12 1 - 50 of 53
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