Change search
Refine search result
1234567 1 - 50 of 382
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Abbasi, Alireza
    et al.
    Geranmayeh, Shokoofeh
    Skripkin, Mikhail Y.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Potassium ion-mediated non-covalent bonded coordination polymers2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 3, p. 850-859Article in journal (Refereed)
    Abstract [en]

    Crystal structures and vibrational spectra of three related network-forming coordination complexes have been studied. Two novel thermodynamically stable pseudo-polymorphic solvated rhodium chloro compounds, [cis-RhCl4(DMSO-kappa S)(2)K](n), 1, and [cis-RhCl4(DMSO-kappa S)(2)K center dot 3H(2)O](n), 2, and one metastable compound [trans-RhCl4(DMSO-kappa S)(2)K center dot 0.25H(2)O](n), 3, crystallize at ambient temperature in the orthorhombic space group P2(1)2(1)2(1) for 1, and the monoclinic space groups P2(1)/n and P2(1)/c for 2 and 3, respectively. All three structures contain [RhCl4(DMSO-kappa S)(2)]-complexes in which the rhodium(III) ions bind to two dimethyl sulfoxide (DMSO) sulfur atoms and four chloride ions in distorted octahedral coordination geometries. The complexes are connected in networks via potassium ions interacting with the Cl- and the DMSO oxygen atoms. As the sum of Shannon ionic radii of K+ and Cl- exceeds the K-Cl distances in compounds under study, these compounds can be described as Rh-Cl-K coordination polymers with non-covalent bonding, which is not common in these systems, forming 1- and 2-D networks for 1/2 and 3, respectively. The 2-D network with nano-layered sheets for compound 3 was also confirmed by TEM images. Further evaluation of the bonding in the cis- and trans-[RhCl4(DMSO-kappa S)(2)](-) entities was obtained by recording Raman and FT-IR absorption spectra and assigning the vibrational frequencies with the support of force-field calculations. The force field study of complexes reveals the strong domination of trans-effect (DMSO-kappa S > Cl) over the effect of non-covalent bonding in coordination polymeric structures. The comparison of calculated RhCl, RhS and SO stretching force constants showed evidence of K+-ligand interactions whereas direct experimental evidences of K+-Cl- interaction were not obtained because of strong overlap of the corresponding spectral region with that where lattice modes and Rh-ligand bendings appear.

  • 2.
    Abdelhamid, Hani Nasser
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assiut University, Egypt; The British University in Egypt, Egypt.
    MOFTextile: Metal-organic frameworks nanosheets incorporated cotton textile for selective vapochromic sensing and capture of pyridine2023In: Applied organometallic chemistry, ISSN 0268-2605, E-ISSN 1099-0739, Vol. 37, no 5, article id e7078Article in journal (Refereed)
    Abstract [en]

    Metal–organic frameworks (MOFs) improved several trends and are promising for industrial applications. However, current synthesis processes offer powder form, rendering their applications difficult. A simple solvothermal method offered an in situ growth of copper-based MOFs, for example, CuBDC (BDC: benzene-1,4-dicarboxylic acid) into a cotton textile; the material was denoted as CuBDC@Textile. CuBDCTextile was used as a solid sensor and adsorbent for volatile organic compounds (VOCs). It exhibited good vapochromic properties that enabled a colorimetric detection of pyridine (Py) via naked eyes with high selectivity and good sensitivity. Adsorption of pyridine via pervaporation using CuBDC@Textile was recorded. CuBDCTextile is a flexible textile with a high adsorption capacity (137.9 mg g−1) toward pyridine. It offered dual functional: sensor probe and adsorbent. The synthesis of CuBDC@Textile and their excellent performance as a sensor and adsorbent are promising for further investigation of the “MOFs on textile materials” topic.

  • 3.
    Abdelhamid, Hani Nasser
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Assiut University, Egypt; The British University in Egypt (BUE), Egypt.
    Sultan, Sahar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D printing of cellulose/leaf-like zeolitic imidazolate frameworks (CelloZIF-L) for adsorption of carbon dioxide (CO2) and heavy metal ions2023In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 52, no 10, p. 2988-2998Article in journal (Refereed)
    Abstract [en]

    Metal–organic frameworks (MOFs) have advanced several technologies. However, it is difficult to market MOFs without processing them into a commercialized structure, causing an unnecessary delay in the material's use. Herein, three-dimensional (3D) printing of cellulose/leaf-like zeolitic imidazolate frameworks (ZIF-L), denoted as CelloZIF-L, is reported via direct ink writing (DIW, robocasting). Formulating CelloZIF-L into 3D objects can dramatically affect the material's properties and, consequently, its adsorption efficiency. The 3D printing process of CelloZIF-L is simple and can be applied via direct printing into a solution of calcium chloride. The synthesis procedure enables the formation of CelloZIF-L with a ZIF content of 84%. 3D printing enables the integration of macroscopic assembly with microscopic properties, i.e., the formation of the hierarchical structure of CelloZIF-L with different shapes, such as cubes and filaments, with 84% loading of ZIF-L. The materials adsorb carbon dioxide (CO2) and heavy metals. 3D CelloZIF-L exhibited a CO2 adsorption capacity of 0.64–1.15 mmol g−1 at 1 bar (0 °C). The materials showed Cu2+ adsorption capacities of 389.8 ± 14–554.8 ± 15 mg g−1. They displayed selectivities of 86.8%, 6.7%, 2.4%, 0.93%, 0.61%, and 0.19% toward Fe3+, Al3+, Co2+, Cu2+, Na+, and Ca2+, respectively. The simple 3D printing procedure and the high adsorption efficiencies reveal the promising potential of our materials for industrial applications.

  • 4. Adolfsson, Erik
    et al.
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Effects of granule density on strength and granule related defects in zirconia2012In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 32, no 11, p. 2653-2659Article in journal (Refereed)
    Abstract [en]

    A suspension of zirconia powder (TZ3YSE) with a solids loading of 50 vol% was prepared by ball milling. Binders were added and some of the suspension was diluted to 40, 30 and 20 vol% before freeze granulation was performed. A spray dried material (TZ3YSEB) was used as a reference. The pore size distribution of the different granules was evaluated and from the microstructure it was shown that inhomogeneities were present in both the freeze granulated as well as in the spray dried granules. In addition, the density, microstructure as well as the strength of sintered materials prepared from the granules were studied. The results showed that a high green density or sintered density was not sufficient in order to achieve a high strength material. It was further shown that the strength was significantly influenced by the granule density and not by the inhomogeneities found in the granules.

  • 5.
    Adranno, Brando
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Complex phase behaviour of organic-inorganic green-emitting ionic manganese halidesManuscript (preprint) (Other academic)
  • 6.
    Adranno, Brando
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    In Light of Ionic Materials: A short exploration of ionic materials for light-related applications2022Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Ionic liquids (ILs) have been one of the most attractive classes of materials of the last decades. The reason behind this is their peculiar set of properties, which enable their possible application in several research fields. ILs are salts that exhibit a very low melting point, which has been arbitrarily defined to be below 100 °C. Due to their ionic nature, ILs have little to no vapor pressure and they often demonstrate good electrical conductivity and high thermal and electrochemical stability. In this work, the focus is directed toward the exploitation of ILs for the engineering of materials that can have a primary role in light-emitting or light-absorbing devices. Materials belonging to the first type are explored in Papers I-III, while the ones belonging to the second are tackled in Papers IV and V.

    There has always been a struggle to find a balance between costs and the efficiency of emitting materials for application in dedicated devices. In Papers I-III, two strategies are taken into account to address this issue. Finding inspiration from ionic complexes of Mn(II), newly designed ionic materials and ILs emitting green light are proposed as an alternative to the more expensive heavy metals-based ones such as Ir(III) and Pt(II). Coming closer to an ideal compromise of cost and performance, fully organic and extremely cheap low-melting salts based on the 8-hydroxyquinoline unit were prepared. These compounds revealed efficient fluorescence in the blue region of the spectrum for such simple molecules, paving the way for the preparation of possibly inexpensive light-emitting devices.

    In Paper IV, direct absorption of light is taken into consideration with photoresponsive ionic liquids, which undergo cis-trans isomerization. Due to this feature and their ionic nature, these materials could be adopted into photoswitches. Additionally, the effect of functional groups on the isomerization of the ILs and on the ability of the materials to undergo mesophase formation was studied.

    One of the key components of dye-sensitized solar cells is the electrolytic mediator sandwiched between two electrodes. This has been a matter of intense study due to issues regarding its stability, which impair the device's performance. ILs can be adopted in devices to solve this issue. In Paper V, triazolium ILs allowed the manufacturing of devices with higher efficiencies and longer lifetimes than the ones realized with imidazolium relatives. These materials allowed for the stability of the ionic couple I-/I3- and moisture resistance due to their non-hygroscopic nature.

    Download full text (pdf)
    In Light of Ionic Materials
    Download (jpg)
    Omslagsframsida
  • 7.
    Adranno, Brando
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    The 8-Hydroxyquinolinium Cation as a Lead Structure for Efficient Colour-Tunable Ionic Small Molecule Emitting MaterialsManuscript (preprint) (Other academic)
  • 8.
    Adranno, Brando
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Renier, Olivier
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bousrez, Guillaume
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Paterlini, Veronica
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Baryshnikov, Glib V.
    Smetana, Volodymyr
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tang, Shi
    Ågren, Hans
    Metlen, Andreas
    Edman, Ludvig
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Aarhus University, Denmark.
    Rogers, Robin D.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). The Queen's University of Belfast, Northern Ireland; The University of Alabama, USA.
    The 8-Hydroxyquinolinium Cation as a Lead Structure for Efficient Color-Tunable Ionic Small Molecule Emitting Materials2023In: Advanced Photonics Research, E-ISSN 2699-9293, Vol. 4, no 3, article id 2200279Article in journal (Refereed)
    Abstract [en]

    Albeit tris(8-hydroxyquinolinato) aluminum (Alq3) and its derivatives are prominent emitter materials for organic lighting devices, and the optical transitions occur among ligand-centered states, the use of metal-free 8-hydroxyquinoline is impractical as it suffers from strong nonradiative quenching, mainly through fast proton transfer. Herein, it is shown that the problem of rapid proton exchange and vibration quenching of light emission can be overcome not only by complexation, but also by organization of the 8-hydroxyquinolinium cations into a solid rigid network with appropriate counter-anions (here bis(trifluoromethanesulfonyl)imide). The resulting structure is stiffened by secondary bonding interactions such as π-stacking and hydrogen bonds, which efficiently block rapid proton transfer quenching and reduce vibrational deactivation. Additionally, the optical properties are tuned through methyl substitution from deep blue (455 nm) to blue-green (488 nm). Time-dependent density functional theory (TDFT) calculations reveal the emission to occur from which an unexpectedly long-lived S1 level, unusual for organic fluorophores. All compounds show comparable, even superior photoluminescence compared to Alq3 and related materials, both as solids and thin films with quantum yields (QYs) up to 40–50%. In addition, all compounds show appreciable thermal stability with decomposition temperatures above 310 °C.

  • 9.
    Adranno, Brando
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Tang, Shi
    Paterlini, Veronica
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Smetana, Volodymyr
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Aarhus University, Denmark.
    Renier, Olivier
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bousrez, Guillaume
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Aarhus University, Denmark.
    Edman, Ludvig
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Aarhus University, Denmark.
    Broadband White-Light-Emitting Electrochemical Cells2023In: Advanced Photonics Research, E-ISSN 2699-9293, Vol. 4, no 5, article id 2200351Article in journal (Refereed)
    Abstract [en]

    Emerging organic light-emitting devices, such as light-emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal-free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal-free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric-field-driven structural transformation of the original green-light emitter structure into a red-emitting structure. 

  • 10.
    Agthe, Michael
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Crystallization on the Mesoscale: Self-Assembly of Iron Oxide Nanocubes into Mesocrystals2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Self-assembly of nanoparticles is a promising route to form complex, nanostructured materials with functional properties. Nanoparticle assemblies characterized by a crystallographic alignment of the nanoparticles on the atomic scale, i.e. mesocrystals, are commonly found in nature with outstanding functional and mechanical properties. This thesis aims to investigate and understand the formation mechanisms of mesocrystals formed by self-assembling iron oxide nanocubes.

    We have used the thermal decomposition method to synthesize monodisperse, oleate-capped iron oxide nanocubes with average edge lengths between 7 nm and 12 nm and studied the evaporation-induced self-assembly in dilute toluene-based nanocube dispersions. The influence of packing constraints on the alignment of the nanocubes in nanofluidic containers has been investigated with small and wide angle X-ray scattering (SAXS and WAXS, respectively). We found that the nanocubes preferentially orient one of their {100} faces with the confining channel wall and display mesocrystalline alignment irrespective of the channel widths. 

    We manipulated the solvent evaporation rate of drop-cast dispersions on fluorosilane-functionalized silica substrates in a custom-designed cell. The growth stages of the assembly process were investigated using light microscopy and quartz crystal microbalance with dissipation monitoring (QCM-D). We found that particle transport phenomena, e.g. the coffee ring effect and Marangoni flow, result in complex-shaped arrays near the three-phase contact line of a drying colloidal drop when the nitrogen flow rate is high. Diffusion-driven nanoparticle assembly into large mesocrystals with a well-defined morphology dominates at much lower nitrogen flow rates. Analysis of the time-resolved video microscopy data was used to quantify the mesocrystal growth and establish a particle diffusion-based, three-dimensional growth model. The dissipation obtained from the QCM-D signal reached its maximum value when the microscopy-observed lateral growth of the mesocrystals ceased, which we address to the fluid-like behavior of the mesocrystals and their weak binding to the substrate. Analysis of electron microscopy images and diffraction patterns showed that the formed arrays display significant nanoparticle ordering, regardless of the distinctive formation process. 

    We followed the two-stage formation mechanism of mesocrystals in levitating colloidal drops with real-time SAXS. Modelling of the SAXS data with the square-well potential together with calculations of van der Waals interactions suggests that the nanocubes initially form disordered clusters, which quickly transform into an ordered phase.

    Download full text (pdf)
    Crystallization on the Mesoscale
    Download (jpg)
    Omslagsframsida
  • 11.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Høydalsvik, Kristin
    Mayence, Arnaud
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Karvinen, Petri
    Liebi, Marianne
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Nygård, Kim
    Controlling Orientational and Translational Order of Iron Oxide Nanocubes by Assembly in Nanofluidic Containers2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 45, p. 12537-12543Article in journal (Refereed)
    Abstract [en]

    We demonstrate that spatial confinement can be used to control the orientational and translational order of cubic nanoparticles. For this purpose we have combined X-ray scattering and scanning electron microscopy to study the ordering of iron oxide nanocubes that have self-assembled from toluene-based dispersions in nanofluidic channels. An analysis of scattering vector components with directions parallel and perpendicular to the slit walls shows that the confining walls induce a preferential parallel alignment of the nanocube (100) faces. Moreover, slit wall separations that are commensurate with an integer multiple of the edge length of the oleic acid-capped nanocubes result in a more pronounced translational order of the self-assembled arrays compared to incommensurate confinement. These results show that the confined assembly of anisotropic nanocrystals is a promising route to nanoscale devices with tunable anisotropic properties.

  • 12.
    Agthe, Michael
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wetterskog, Erik
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Following the mesocrystal growth of self-assembling iron oxide nanocubes by video microscopy and quartz crystal microbalance with dissipation monitoringManuscript (preprint) (Other academic)
  • 13.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Andersson, Linnéa
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Colloidal processing and CO2 capture performance of sacrificially templated zeolite monoliths2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, p. 289-296Article in journal (Other academic)
    Abstract [en]

    Sacrificial templating of suspension cast and subsequently thermally treated zeolite monoliths with glassy carbon spheres and fibers yielded zeolite 13X and silicalite-1 monoliths with macroporosities up to 50 vol%. Homogeneous distribution of the macroporosity in hierarchically porous monoliths was obtained by tailoring the surface chemistry of the carbon particles by polyelectrolyte-assisted adsorption of zeolite particles. The effect of amount of kaolin binder and temperature for the thermal treatment on the monoliths strength, surface area and CO2 uptake was studied by diametral compression tests, electron microscopy, X-ray diffraction and gas adsorption. Cyclic adsorption and regeneration measurements showed that zeolite 13X monoliths display a high CO2 uptake while the silicalite-1 monoliths could be regenerated with a relatively low energy penalty.

  • 14.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Luleå University of Technology, Sweden.
    Keshavarzi, Neda
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Shakarova, Dilshod
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cheung, Ocean
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Aluminophosphate monoliths with high CO2-over-N2 selectivity and CO2 capture capacity2014In: RSC Advances, E-ISSN 2046-2069, Vol. 4, no 99, p. 55877-55883Article in journal (Refereed)
    Abstract [en]

    Monoliths of microporous aluminophosphates (AlPO4-17 and AlPO4-53) were structured by binder-freepulsed current processing. Such monoliths could be important for carbon capture from flue gas. TheAlPO4-17 and AlPO4-53 monoliths exhibited a tensile strength of 1.0 MPa and a CO2 adsorption capacityof 2.5 mmol g1 and 1.6 mmol g1, respectively at 101 kPa and 0 C. Analyses of single component CO2and N2 adsorption data indicated that the AlPO4-53 monoliths had an extraordinarily high CO2-over-N2selectivity from a binary gas mixture of 15 mol% CO2 and 85 mol% N2. The estimated CO2 capturecapacity of AlPO4-17 and AlPO4-53 monoliths in a typical pressure swing adsorption (PSA) process at 20C was higher than that of the commonly used zeolite 13X granules. Under cyclic sorption conditions,AlPO4-17 and AlPO4-53 monoliths were regenerated by lowering the pressure of CO2. Regeneration wasdone without application of heat, which would regenerate them to their full capacity for CO2 adsorption.

    Download full text (pdf)
    Aluminophosphate monoliths with high CO2-over- N2 selectivity and CO2 capture capacity
  • 15.
    Akhtar, Farid
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ojuva, Arto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wirawan, Sang Kompiang
    Hedlund, Jonas
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    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.

  • 16.
    Almenara Perez, Naroa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gueret, Robin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Huertas-Alonso, Alberto José
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thalakkale Veettil, Unnimaya
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sipponen, Mika H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lizundia, Erlantz
    Lignin–Chitosan Gel Polymer Electrolytes for Stable Zn Electrodeposition2023In: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 11, no 6, p. 2283-2294Article in journal (Refereed)
    Abstract [en]

    Electrochemical energy storage technologies offer means to transition toward a decarbonized society and carbon neutrality by 2050. Compared to conventional lithium-ion batteries, aqueous zinc-ion chemistries do not require scarce materials or toxic and flammable organic-based electrolytes to function, making them favorable contenders in the scenario of intensifying climate change and supply chain crisis. However, environmentally benign and bio-based materials are needed to substitute fossil-based battery materials. Accordingly, this work taps into the possibilities of lignin together with chitosan to form gel polymer electrolytes (GPEs) for zinc-ion chemistries. A simple fabrication process enabling free-standing sodium lignosulfonate–chitosan and micellar lignosulfonate–kraft lignin–chitosan GPEs with diameters exceeding 80 mm is developed. The GPEs combine tensile strength with ductility, reaching Young’s moduli of 55 ± 4 to 940 ± 63 MPa and elongations at break of 14.1 ± 0.2 to 43.9 ± 21.1%. Competitive ionic conductivities ranging from 3.8 to 18.6 mS cm–1 and electrochemical stability windows of up to +2.2 V vs Zn2+/Zn were observed. Given the improved interfacial adhesion of the GPEs with metallic Zn promoted by the anionic groups of the lignosulfonate, a stable cycling of the Zn anode is obtained. As a result, GPEs can operate at 5000 μA cm–2 with no short-circuit and Coulombic efficiencies above 99.7%, outperforming conventional separator–liquid electrolyte configurations such as the glass microfiber separator soaked into 2 M ZnSO4 aqueous electrolyte, which short-circuits after 100 μA cm–2. This work demonstrates the potential of underutilized biorefinery side-streams and marine waste as electrolytes in the battery field, opening new alternatives in the sustainable energy storage landscape beyond LIBs.

  • 17.
    Andersson, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ojuva, Arto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Colloidal processing and CO2-capture performance of hierarchically porous Al2O3-zeolite 13X composites2012In: Journal of Ceramic Science and Technology, ISSN 2190-9385, Vol. 3, no 1, p. 9-16Article in journal (Refereed)
    Abstract [en]

    Hierarchically porous composites for CO2-capture have been produced by coating the inner walls of foam-like macroporous alumina monoliths, produced by templated synthesis, with microporous zeolite 13X particles. Homogeneous and dense coatings of the particulate adsorbent were obtained when the impregnation process was performed at a pH above 9. At this pH-level the colloidally stable suspensions of the negatively charged zeolite 13X particles could fill all the voids of the highly connected pore space of the alumina supports and attach to the monolith walls, which had been pre-coated with poly(ethylene imine). A CO2-uptake as high as 5 mmol CO2/g zeolite 13X was achieved for alumina-zeolite 13X composites through minimisation of the added inorganic binder, kaolin, to only 3.0 wt% with respect to zeolite content, and through optimisation of the thermal treatment.

  • 18.
    Apostolopoulou Kalkavoura, Varvara
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Fijoł, Natalia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lombardo, Salvatore
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ruiz-Caldas, Maria-Ximena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Trash to treasure: 3D printing of waste-based polycotton composite for the production of water filters and commodity productsManuscript (preprint) (Other academic)
    Abstract [en]

    The recycling of polycotton without separating its constituents for high-performance applications has not yet been fully investigated. In this study, we propose a simple and efficient method involving one-pot, 2, 2, 6, 6 – tetramethylpiperdine-1-oxyl (TEMPO) - oxidation of post-consumer polycotton textile waste followed by lenient mechanical fibrillation. Successful chemical modification of the polycotton waste was confirmed by the Fourier-transform infrared (FT-IR) spectroscopy measurements, in which the presence of carboxyl groups introduced during the TEMPO-oxidation was observed. Moreover, the waste-based pellets were single-screw extruded into 3D printing filaments, which were further processed via desktop Fused Deposition Modelling (FDM) 3D printer.

    FDM processing was carried out without hindrance. The textile-based filament was used for the fabrication of a variety of high surface-finish quality models, which presented diverse geometries and porosity architectures. The versatility of the developed 3D printed models was demonstrated through both, their potential to be utilized as fashion accessories, and by evaluating their performance in water treatment applications. Taking advantage of the introduction of negatively charged carboxylic groups onto the polycotton-based materials, which was expected to facilitate the electrostatic interactions with positively charged species, the 3D printed filters were tested for removal of cationic dye methylene blue (MB) from water in a batch adsorption study. The adsorption followed Langmuir model, with a maximim adsorption capacity of 3 µmol/g. 

    Overall, this work presents a novel approach for the upcycling of polycotton waste into functional filament suitable for a variety of 3D printing, and further, engineering applications. The development of composite filaments and their mechanical and adsorption properties pave the way for future research within valorisation of textile-based waste.

  • 19.
    Apostolopoulou-Kalkavoura, Varvara
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Thermal Conductivity of Hygroscopic Foams Based on Cellulose Nanomaterials2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Biobased super-insulating materials could mitigate climate change by minimizing the use of petroleum-based materials, creating artificial carbon sinks and minimizing the energy needed to maintain pleasant interior conditions. Cellulose nanomaterials (CNM) produced from abundantly available cellulose sources constitute versatile, highly anisotropic raw materials with tunable surface chemistry and high strength. This thesis includes the evaluation of the thermal conductivity of isotropic and anisotropic CNM-based foams and aerogels and analysis of the dominant heat transfer mechanisms. 

    We have developed a customized measurement cell for hygroscopic materials in which the humidity and temperature are carefully controlled while the thermal conductivity is measured. Anisotropic cellulose nanofibrils (CNF) foams with varying diameters showed a super-insulating behavior perpendicular (radial) to the nanofibril direction, that depended non-linearly on the relative humidity (RH) and foam density. Molecular simulations revealed that the very low thermal conductivity is related to phonon scattering due to the increase of the inter-fibrillar gap with increasing RH that resulted in a 6-fold decrease of the thermal boundary conductance. The moisture-induced swelling exceeds the thermal conductivity increase due to water uptake at low and intermediate RH and resulted in a minimum thermal conductivity of 14 mW m-1 K-1 at 35% RH and 295 K for the foams based on the thinnest CNF.

    The density-dependency of the thermal conductivity of cellulose nanocrystal (CNC) foams with densities of 25 to 129 kg m-3 was investigated and a volume-weighted modelling of the solid and gas thermal conductivity contributions suggested that phonon scattering was essential to explain the low radial thermal conductivity, whereas the replacement of air with water and the Knudsen effect related to the nanoporosity in the foam walls had a small effect. Intermediate-density CNC foams (34 kg m-3) exhibited a radial thermal conductivity of 24 mW m-1 K-1 at 295 K and 20% RH, which is below the value for air.

    The moisture uptake of foams based on CNMs with different degree of crystallinity and surface modifications decreased significantly with increasing crystallinity and temperature. Molecular simulations showed that the narrow pore size distribution of the amorphous cellulose film, and the relatively low water adsorption in the hydration cell around the oxygen of the carboxyl group play an important role for the moisture uptake of amorphous and crystalline CNM-based materials.

    Isotropic CNF- and polyoxamer based foams as well as CNF-AL-MIL-53 (an aluminum‑based metal-organic framework) foams were both moderately insulating (>40 mW m-1 K-1) and comparable with commercial expanded polystyrene. The thermal conductivity of CNF and polyoxamer foams displayed a very strong RH dependency that was modelled with a modified Künzel’s model. The presence of hydrophobic AL-MIL-53 decreased the moisture uptake of CNF-AL-MIL-53 aerogels by 42% compared to CNF-polyoxamer foams.

    Solid and gas conduction are the main heat transfer mechanisms in hygroscopic nanofibrillar foams and aerogels that depend on the interfacial phonon scattering, Knudsen effect and water uptake. It is essential that the thermal conductivity measurements of hygroscopic CNM-based foams and aerogels are determined at controlled RH and that parameters such as the temperature, density, nanoporosity, fibril dimensions and alignment are characterized and controlled for systematic development and upscaling of biobased foams for applications in building insulation and packaging.

    Download full text (pdf)
    Thermal Conductivity of Hygroscopic Foams Based on Cellulose Nanomaterials
    Download (jpg)
    omslagsframsida
  • 20. Aristov, Maria
    et al.
    Eichhorn, Ralf
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Bechinger, Clemens
    Separation of chiral colloidal particles in a helical flow field2013In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 9, no 8, p. 2525-2530Article in journal (Refereed)
    Abstract [en]

    Stereoisomeric molecules with opposite chirality, so-called enantiomers, often vary regarding their sensory, pharmacological and toxicological properties. Such enantiomer specific effects play a central role in the development, testing and evaluation of drugs, pesticides and food related products. Accordingly, efficient techniques for separation of chiral mixtures into enantiopure compounds are of enormous practical relevance. Most current enantiomer separation methods are based on enantioselective interactions with an auxiliary substance which has to be developed and optimized for different chiral molecules in an elaborate and costly process. Here, we experimentally demonstrate the separation of micron-sized chiral particles in a helical fluid flow which is created inside a microfluidic device patterned with slanted grooves. We observe that the retention time of particles in a helical flow field strongly depends on their chirality which leads to an effective chiral separation within the channel. Our experimental results are confirmed by numerical calculations which demonstrate how the coupling of rotational and translational degrees of freedom leads to differences in the trajectories of particles with opposite chirality. Since our separation mechanism does not rely on material specific interactions, this offers considerable advantages over existing methods. We expect that our approach can be also applied at nanometre length scales by using channels with smaller diameters and with an optimized geometry.

  • 21. Asahina, Shunsuke
    et al.
    Uno, Shinobu
    Suga, Mitsuo
    Stevens, Sam
    Klingstedt, Miia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Okano, Yasuyuki
    Kudo, Masato
    Schuth, Ferdi
    Anderson, Michael
    Adschiri, Tadafumi
    Terasaki, Osamu
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    A new HRSEM approach to observe fine structures of novel nanostructured materials2011In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 146, no 1-3, p. 11-17Article in journal (Refereed)
    Abstract [en]

    A new approach for observing fine structures of novel thin, nanostructured materials called through the employed to observe interesting features on a variety of new, catalyticallyimportant hierarchically porous rattlespheres.

  • 22. Atluri, Rambabu
    et al.
    Iqbal, Muhammad Naeem
    Bacsik, Zoltan
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Villaescusa, Luis Angel
    Garcia-Bennett, Alfonso E.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry. alfonso@mmk.su.se.
    Self-Assembly Mechanism of Folate-Templated Mesoporous Silica2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 38, p. 12003-12012Article in journal (Refereed)
    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.

  • 23. Avila, M.
    et al.
    Burks, T.
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gothelid, M.
    Lansaker, P. C.
    Toprak, M. S.
    Muhammed, M.
    Uheida, A.
    Surface functionalized nanofibers for the removal of chromium(VI) from aqueous solutions2014In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 245, p. 201-209Article in journal (Refereed)
    Abstract [en]

    Polyacrylonitrile (PAN) nanofibers functionalized with amine groups (PAN-NH2) were prepared using a simple one-step reaction route. The PAN-NH2 nanofibers were investigated for the removal of chromium(VI) from aqueous solutions. The adsorption and the kinetic characteristics were evaluated in batch process. The adsorption process showed pH dependence and the maximum Cr(VI) adsorption occurred at pH = 2. The Langmuir adsorption model described well the experimental adsorption data and estimated a maximum loading capacity of 156 mg/g, which is a markedly high value compared to other adsorbents reported. The kinetics studies indicated that the equilibrium was attained after 90 min and the experimental data followed a pseudo-second order model suggesting a chemisorption process as the rate limiting step. X-ray Photoelectron Spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) revealed that the adsorption of Cr(VI) species on PAN-NH2 was facilitated through both electrostatic attraction and surface complexation. High desorption efficiency (> 90%) of Cr(VI) was achieved using diluted base solutions that may allow the reuse of PAN-NH2 nanofibers.

  • 24.
    Aziz, Baroz
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synthesis and modification of potential CO2 adsorbents: Amine modified silica and calcium carbonates2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The prospect of rapid changes to the climate due to global warming is subject of public concern. The need to reduce the emissions of atmospheric green house gases and in particular carbon dioxide is greater than ever. Extensive research is performed to find new solutions and new materials, which tackles this problem in economically benign way. This thesis dealt with two potential adsorbents for post combustion  carbon capture, namely, amine modified silica and calcium carbonates. We modified porous silica with large surface area by propyl-amine groups to enhance the carbon dioxide adsorption capacity and selectivity. Experimental parameters, such as reaction time, temperature, water content, acid and heat treatment of silica substrate were optimized using a fractional factorial design. Adsorption properties and the nature of formed species upon reaction of CO2 and amine-modified silica were studied by sorption and infrared spectroscopy. Physisorbed and chemisorbed amount of adsorbed CO2 were, for the first time, estimated directly in an accurate way. The effects of temperature and moisture on the CO2 adsorption properties were also studied.

    Crystallization of calcium carbonate as a precursor to calcium oxide, which can be used as carbon dioxide absorbent, was studied in the second part of this thesis. Structure of different amorphous phases of calcium carbonate was studied in detail. Crystallization of calcium carbonate with and without additives was studied. Parameters like stirring rate, temperature, pH and polymer concentration showed to be important in selection of phase and morphology. An aggregation mediated crystallization was postulated to explain the observed morphologies. 

    Download full text (pdf)
    Fulltext
  • 25.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gebauer, Denis
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kinetic control of particle-mediated calcium carbonate crystallization2011In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 13, no 14, p. 4641-4645Article in journal (Refereed)
    Abstract [en]

    By changing the temperature, pH, stirring rate, or time for calcium carbonate crystallization, complex shapes of aggregated calcium carbonates formed. Such shapes have earlier been ascribed to specific interactions with specialized additives. Without polymeric additives, aggregates of vaterite transformed more rapidly into calcite aggregates under slow than under fast stirring. With an anionic polyelectrolyte added, vaterite was stabilized. Larger polycrystalline aggregates of vaterite formed under rapid than under slow stirring, indicative of a particle mediated growth of aggregates controlled by convective currents. The size of the underlying nanoparticles was temperature dependent, with grain sizes of similar to 20 to 50 nm at 20 degrees C and similar to 350 nm at 90 degrees C. The small differences in free energy between the anhydrous polymorphs of calcium carbonate made both kinetic and equilibrium dependencies important.

    Download full text (pdf)
    fulltext
  • 26.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
    Quantification of chemisorption and physisorption of carbon dioxide on porous silica modified by propylamines: Effect of amine density2012In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 159, p. 42-49Article in journal (Refereed)
    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.

  • 27.
    Aziz, Baroz
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zhao, Guoying
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Carbon Dioxide Sorbents with Propylamine Groups-Silica Functionalized with a Fractional Factorial Design Approach2011In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 7, p. 3822-3834Article in journal (Refereed)
    Abstract [en]

    Mesoporous silica particles (Davisil) were functionalized with aminopropyltriethoxysilane (APTES) in a fractional factorial design with 19 different synthesis and uptake experiments. The number of amino groups and the uptake of CO(2) were optimized in a 2(V)(5-1) design. Most important to functionalizationwas the amount of water present during synthesis, the reaction time, and pretreating the silica with a mineral acid; certain two-way interactions were shown to be statistically significant as well. Modifications performed at 110 or 80 degrees C showed no significant differences concerning amine content or uptake of CO(2). Properly choosing center points for the discrete variables is problematic and is somewhat related to the lack of fit with respect to CO(2) uptake; the regression was good. Solid-state (29)Si NMR showed that the APTES was mainly fully condensed. Specific surface areas did not correlate with the number of n-propylamine groups on the silica, which is indicative of differential levels of heterogeneity in the coverage of propylamines. The uptake of CO(2) and N(2) was measured from -20 to 70 degrees C and from 0 to 1 bar and parametrized by the Freundlich isotherm. Amine-modified silica adsorbed significant amounts of CO(2), especially at the low partial pressure, which is important for CO(2) capture from flue gas. At such pressures, samples with a high density of amine (4 amines/nm(2)) showed a much higher uptake of CO(2) than did those with densities of similar to 2-3 amines/nm(2), reflecting differential tendencies to form propylammonium-propylcarbamate ion pairs; these require close proximity among amine groups to form. Water affected the uptake of carbon dioxide in different ways. Certain samples took up more moist CO(2) gas than dry CO(2), and others took up less moist CO(2) than dry CO(2), which is indicative of differential tendencies toward water adsorption. We conclude that experimental design is a time-efficient approach to the functionalization of silica with propylamine groups.

  • 28.
    B. Brant Carvalho, Paulo H.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Pressure-Induced Amorphization and Distinct Amorphous States of Clathrate Hydrates2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis summarizes a study on the pressure-induced amorphization (PIA) and structures of amorphous states of clathrate hydrates (CHs).

    PIA involves the transition of a crystalline material into an amorphous solid in response of mechanical compression at temperatures well below the melting point. The first material observed to undergo PIA was hexagonal ice. More recently it was shown that compounds of water undergo the same phenomenon without decomposition, despite the presence of solutes. CHs, which are crystalline inclusion compounds consisting of water molecules encaging small guest species, undergo PIA at ca. 1–4 GPa below 145 K. The obtained amorphous CH phase can be further densified on isobaric heating at high pressure. This annealing step enables to retain an amorphous material on pressure release. There has been a significant amount of studies into the understanding of the nature of PIA and transformations between amorphous phases of pure ice. The aim of this thesis has been the understanding of the PIA in CHs and its relation to pure ice. New information on the nature of PIA and subsequent amorphous-amorphous transitions in CH systems were gained from structural studies and in situ neutron diffraction played pivotal role due to the sensitivity of neutrons to the light element hydrogen. Here a generalized understanding of the PIA in CHs and a clear image of amorphous CH structures are presented.

    Download full text (pdf)
    Pressure-Induced Amorphization and Distinct Amorphous States of Clathrate Hydrates
    Download (jpg)
    presentationsbild
  • 29. Bao, Zijia
    et al.
    Zhou, Guojun
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Liu, Xinrong
    Peng, Yuxin
    Huang, Zhehao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Zheng, Haoquan
    A bimetallic 3D interconnected metal–organic framework with 2D morphology and its derived electrocatalyst for oxygen reduction2023In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 25, no 13, p. 1869-1873Article in journal (Refereed)
    Abstract [en]

    Metal–organic frameworks (MOFs) are widely used as precursors to generate derivatives for electrocatalysis. However, two-dimensional (2D) MOFs often suffer from the collapse of their 2D structures after being treated at high temperature. Herein, we used the dense ZIF-EC1 as a precursor and doped Co as a secondary metal. The content of Co in ZIF-EC1 can be tuned without changing the crystalline structure. After pyrolysis, the derived carbon-based material maintains the 2D morphology from the parental precursor. The derived ZIF-EC1(ZnCo)-20-900 exhibits the best activity toward the ORR, which is even better than that of Pt/C. This work demonstrates the potential of using a nonporous dense MOF as a precursor and optimizing electrocatalytic ORR activity by tuning the Co content.

  • 30.
    Biendicho, Jordi Jacas
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). STFC Rutherford Appleton Laboratory, England.
    Shafeie, Samrand
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Frenck, Louise
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Pierre & Marie Curie University, France.
    Gavrilova, Daria
    Böhme, Solveigh
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Chemnitz University of Technology, Germany.
    Bettanini, A. M.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Universita Ca Foscari Venezia, Italy.
    Svedlindh, Peter
    Hull, Steve
    Zhe, Zhao
    Istomin, S. Y.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Grins, Jekabs
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Synthesis and characterization of perovskite-type SrxY1−xFeO3−δ (0.63≤x<1.0) and Sr0.75Y0.25Fe1−yMyO3−δ (M=Cr, Mn, Ni), (y=0.2, 0.33, 0.5)2013In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 200, p. 30-38Article in journal (Refereed)
    Abstract [en]

    Oxygen-deficient ferrates with the cubic perovskite structure SrxY1-xFeO3-d were prepared in air (0.71 ≤ x ≤ 0.91) as well as in N2 (x=0.75 and 0.79) at 1573K. The oxygen content of the compounds prepared in air increases with increasing strontium content from 3-δ=2.79(2) for x=0.75 to 3-δ=2.83(2) for x=0.91. Refinement of the crystal structure of Sr0.75Y0.25FeO2.79 using TOF neutron powder diffraction (NPD) data shows high anisotropic atomic displacement parameter (ADP) for the oxygen atom resulting from a substantial cation and anion disorder. Electron diffraction (ED) and high-resolution electron microscopy (HREM) studies of Sr0.75Y0.25FeO2.79 reveal a modulation along <100>p with G± ~0.4<100>p indicating a local ordering of oxygen vacancies. Magnetic susceptibility measurements at 5-390K show spin-glass behaviour with dominating antiferromagnetic coupling between the magnetic moments of Fe cations. Among the studied compositions, Sr0.75Y0.25FeO2.79 shows the lowest thermal expansion coefficient (TEC) of 10.5 ppm K-1 in air at 298-673K. At 773-1173K TEC increases up to 17.2 ppm K-1 due to substantial reduction of oxygen content. The latter also results in a dramatic decrease of the electrical conductivity in air above 673K. Partial substitution of Fe by Cr, Mn and Ni according to the formula Sr0.75Y0.25Fe1-yMyO3-δ (y=0.2, 0.33, 0.5) leads to cubic perovskites for all substituents with y=0.2. Their TECs are higher in comparison with un-doped Sr0.75Y0.25FeO2.79. Only M=Ni has increased electrical conductivity compared to un-doped Sr0.75Y0.25FeO2.79.

    Download full text (pdf)
    fulltext
  • 31.
    Björnerbäck, Fredrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sustainable porous organic materials: Synthesis, sorption properties and characterization2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The resources available to us humans, including metals, minerals, biomass, air, water, and anything else on the planet, are being used at an increasing rate. This anthropogenic use of resources both depletes the resources and has negative impacts on other resources, e.g. the biosphere. Thus, developing (more) sustainable chemical and industrial processes are of the utmost importance for the well-being of the creatures of Earth and for the long-term sustainability of human society.

    This thesis focuses on organic porous materials, and more specifically their synthesis and characterization. Porous materials are, for example, used in detergents, water treatment, bio gas upgrading, carbon dioxide capture, as catalysts, in sensors, and in various biological applications. The application of porous materials can contribute to the drive towards a more sustainable society. However, porous materials are typically not sustainable themselves. Thus, there is a need to develop more sustainable porous materials. The synthesis and characterization of three different groups of porous organic materials are described in this thesis.

    In pulp- and paper manufacturing, lignin is separated from desirable products and is typically combusted for heat. In one section of this thesis, lignin was used to produce bio-oil for potential use in fuels and chemicals. However, the bio-oil process produced a solid by-product. The by-product was used to synthesize and study activated carbons with very high porosities and magnetic properties, a combination of properties that may prove to be useful in applications.

    Sugar is known to produce solid and unwanted compounds through reactions with acids. It is shown here that it is possible to produce highly microporous humins, i.e. organic porous materials with a large amount of small pores, using sulphuric acid and a range of saccharides and bio-based polymers. This work supports that solid by-products in a wide range of biomass conversion processes can be of high value, both economically and as replacements for less sustainable alternatives.

    The biosphere contains vast amounts of molecules with aromatic structures. The last section of this thesis shows how such aromatic molecules can be used to produce highly porous materials through Friedel-Crafts type chemistry using sulfolane as a solvent and iron chloride as a catalyst. This synthesis strategy produces high-performance materials, improves upon the sustainability of traditional Friedel-Crafts chemistry, and makes use of typically underutilized and abundant bio-based molecules.

    Download full text (pdf)
    Sustainable porous organic materials
    Download (jpg)
    Omslagsframsida
  • 32.
    Bogár, Krisztián
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Krumlinde, Patrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bacsik, Zoltán
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bäckvall, Jan E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Heterogenized Wilkinson's Catalyst for Transfer Hydrogenation of Carbonyl Compounds2011In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 23, p. 4409-4414Article in journal (Refereed)
    Abstract [en]

    Wilkinson’s catalyst [RhCl(PPh3)3] was heterogenized on common silica by the use of a grafting/anchoring technique. The immobilized catalyst showed high activity and selectivity in transfer hydrogenation reactions of a range of carbonyl compounds in 2-propanol. Reactions carried out in 2-propanol at reflux afforded the corresponding alcohols in high yields in short reaction times. The heterogeneous feature ofthe catalyst allows for easy recovery and efficient reuse in the same reaction up to 5 times without any detectible loss of catalytic activity.

  • 33.
    Boscolo Bibi, Sara
    Stockholm University, Faculty of Science, Department of Physics.
    Going for gold: A spectroelectrochemical and catalytic study of gold materials2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the increase in demand for renewable energy, understanding chemical processes is essential for improving the design of catalysts in order to achieve better performance. This thesis summarises the experimental investigation of three types of catalytic gold materials: gold oxide formed from gold films, oxide-derived gold (OD-Au) produced from gold films, and gold nanoparticles supported on metal oxides. Different spectroscopic techniques were employed, such as operando sum frequency generation (SFG) and in situ and ex situ X-ray spectroscopies. These methods allowed the probing of the electronic and chemical states of gold after oxidising electrochemical treatments. The results indicate the presence of subsurface gold oxide remnants after formation of OD-Au, which may help explain its improved catalytic properties with respect to pure gold. In addition, a mathematical model to couple the early stages of gold oxide formation with the nonlinear optical response of gold during this process is presented. This model suggests that the growth proceeds from small oxide islands to 3D oxide growth, while SFG oxidation variation is due to the suppression of the free electron density by negatively-charged adsorbing oxygen atoms. Gold oxide was also studied with both in situ and operando X-ray spectroscopies, showing the importance of a continuous electrochemical treatment during measurements to avoid beam induced effects. Furthermore, gold nanoparticles supported on metal oxides (TiO2 and γ-Fe2O3) were investigated mainly with mass spectrometry. The results indicate two different reaction pathways for oxidation of CO to CO2 depending on the type of metal oxide support. These findings could be used to help design future gold-based catalysts.

    Download full text (pdf)
    Going for gold
    Download (jpg)
    Omslagsframsida
  • 34.
    Boscolo Bibi, Sara
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    El-Zohry, Ahmed M.
    Stockholm University, Faculty of Science, Department of Physics.
    Davies, Bernadette
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Stockholm University, Faculty of Science, Department of Physics.
    Grigorev, Vladimir
    Stockholm University, Faculty of Science, Department of Physics.
    Goodwin, Christopher M.
    Stockholm University, Faculty of Science, Department of Physics.
    Lömker, Patrick
    Stockholm University, Faculty of Science, Department of Physics.
    Holm, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    Ali-Löytty, Harri
    Garcia-Martinez, Fernando
    Schlueter, Christoph
    Soldemo, Markus
    Stockholm University, Faculty of Science, Department of Physics.
    Koroidov, Sergey
    Stockholm University, Faculty of Science, Department of Physics.
    Hansson, Tony
    Stockholm University, Faculty of Science, Department of Physics.
    Multi-spectroscopic study of electrochemically-formed oxide-derived gold electrodes2023In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084Article in journal (Refereed)
    Abstract [en]

    Oxide-derived metals are produced by reducing an oxide precursor. These materials, including gold, have shown improved catalytic performance over many native metals. The origin of this improvement for gold is not yet understood. In this study, operando non-resonant sum frequency generation (SFG) and ex situ high-pressure X-ray photoelectron spectroscopy (HP-XPS) have been employed to investigate electrochemically-formed oxide-derived gold (OD-Au) from polycrystalline gold surfaces. A range of different oxidizing conditions were used to form OD-Au in acidic aqueous medium (H3PO4, pH = 1). Our electrochemical data after OD-Au is generated suggest that the surface is metallic gold, however SFG signal variations indicate the presence of subsurface gold oxide remnants between the metallic gold surface layer and bulk gold. The HP-XPS results suggest that this subsurface gold oxide could be in the form of Au2O3 or Au(OH)3. Furthermore, the SFG measurements show that with reducing electrochemical treatments the original gold metallic state can be restored, meaning the subsurface gold oxide is released. This work demonstrates that remnants of gold oxide persist beneath the topmost gold layer when the OD-Au is created, potentially facilitating the understanding of the improved catalytic properties of OD-Au.

  • 35.
    Bousrez, Guillaume
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Renier, Olivier Quentin
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Paterlini, Veronica
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Smetana, Volodymyr
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mudring, Anja-Verena
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Magnetic, Photo- and Electroluminescent: Multifunctional Ionic Tb Complexes2021In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 60, no 23, p. 17487-17497Article in journal (Refereed)
    Abstract [en]

    In the search for new multifunctional materials, particularly for application in solid-state lighting, a set of terbium salicylato (Sal) complexes of general composition [Cat][Tb(Sal)4] with the commonly ionic liquid-forming (IL) cations [Cat] = (2-hydroxyethyl)trimethylammonium (choline) (Chol+), diallyldimethylammonium (DADMA+), 1-ethyl-3-methylimidazolium (C2C1Im+), 1-butyl-3-methylimidazolium (C4C1Im+), 1-ethyl-3-vinylimidazolium (C2Vim+), and tetrabutylphosphonium (P4444+) were synthesized. All Tb compounds exhibit strong green photoluminescence of high color purity by energy transfer from the ligand in comparison with what the analogous La compounds show, and quantum yields can reach up to 63% upon ligand excitation. When excited with an HF generator, the compounds show strong green electroluminescence with the same features of mission. The findings promise a high potential of application as emitter materials in solid-state lighting. As an additional feature, the Tb compounds show a strong response to applied external fields, rendering them multifunctional materials.

  • 36. Brandner, Lea A.
    et al.
    Linares-Moreau, Mercedes
    Zhou, Guojun
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Amenitsch, Heinz
    Dal Zilio, Simone
    Huang, Zhehao
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Doonan, Christian
    Falcaro, Paolo
    Water sensitivity of heteroepitaxial Cu-MOF films: dissolution and re-crystallization of 3D-oriented MOF superstructures2023In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 14, no 43, p. 12056-12067Article in journal (Refereed)
    Abstract [en]

    3D-oriented metal–organic framework (MOF) films and patterns have recently emerged as promising platforms for sensing and photonic applications. These oriented polycrystalline materials are typically prepared by heteroepitaxial growth from aligned inorganic nanostructures and display anisotropic functional properties, such as guest molecule alignment and polarized fluorescence. However, to identify suitable conditions for the integration of these 3D-oriented MOF superstructures into functional devices, the effect of water (gaseous and liquid) on different frameworks should be determined. We note that the hydrolytic stability of these heteroepitaxially grown MOF films is currently unexplored. In this work, we present an in-depth analysis of the structural evolution of aligned 2D and 3D Cu-based MOFs grown from Cu(OH)2 coatings. Specifically, 3D-oriented Cu2L2 and Cu2L2DABCO films (L = 1,4-benzenedicarboxylate, BDC; biphenyl-4,4-dicarboxylate, BPDC; DABCO = 1,4-diazabicyclo[2.2.2]octane) were exposed to 50% relative humidity (RH), 80% RH and liquid water. The combined use of X-ray diffraction, infrared spectroscopy, and scanning electron microscopy shows that the sensitivity towards humid environments critically depends on the presence of the DABCO pillar ligand. While oriented films of 2D MOF layers stay intact upon exposure to all levels of humidity, hydrolysis of Cu2L2DABCO is observed. In addition, we report that in environments with high water content, 3D-oriented Cu2(BDC)2DABCO recrystallizes as 3D-oriented Cu2(BDC)2. The heteroepitaxial MOF-to-MOF transformation mechanism was studied with in situ synchrotron experiments, time-resolved AFM measurements, and electron diffraction. These findings provide valuable information on the stability of oriented MOF films for their application in functional devices and highlight the potential for the fabrication of 3D-oriented superstructures via MOF-to-MOF transformations.

  • 37. Brunatova, Ereza
    et al.
    Matej, Zdenek
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Vesely, Josef
    Danis, Stanislav
    Popelkova, Daniela
    Kuzel, Radomir
    Thermal stability of titanate nanorods and titania nanowires formed from titanate nanotubes by heating2014In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 98, p. 26-36Article in journal (Refereed)
    Abstract [en]

    The structure of titanate nanowires was studied by a combination of powder X-ray diffraction (XRD) and 3D precession electron diffraction. Titania nanowires and titanate nanorods were prepared by heating of titanate nanotubes. The structure of final product depended on heating conditions. Titanium nanotubes heated in air at a temperature of 850 degrees C decomposed into three phases Na2Ti6O13 (nanorods) and two phases of TiO2 anatase and rutile. At higher temperatures the anatase form of TiO2 transforms into rutile and the nanorods change into rutile nanoparticles. By contrast, in the vacuum only anatase phases of TiO2 were obtained by heating at 900 degrees C. The anatase transformation into ruffle began only after a longer time of heating at 1000 degrees C. For the description of anisotropic XRD line broadening in the total powder pattern fitting by the program MSTRUCT a model of nanorods with elliptical base was included in the software. The model parameters rod length, axis size of the elliptical base, the ellipse flattening parameter and twist of the base could be refined. Variation of particle shapes with temperature was found.

  • 38. Brunatova, Tereza
    et al.
    Popelkova, Daniela
    Wan, Wei
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Danis, Stanislav
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Kuzel, Radomir
    Study of titanate nanotubes by X-ray and electron diffraction and electron microscopy2014In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 87, p. 166-171Article in journal (Refereed)
    Abstract [en]

    The structure of titanate nanotubes (Ti-NTs) was studied by a combination of powder X-ray diffraction (PXRD), electron diffraction and high resolution transmission electron microscopy (HRTEM). Ti-NTs are prepared by hydrothermal treatment of TiO2 powder. The structure is identified by powder X-ray diffraction as the one based on the structure of H2Ti2O5 center dot H2O phase. The same structure is obtained by projected potential from HRTEM through-focus image series. The structure is verified by simulated PXRD pattern with the aid of the Debye formula. The validity of the model is tested by computing Fourier transformation of a single nanotube which is proportional to measured electron diffraction intensities. A good agreement of this calculation with measured precession electron diffraction data is achieved.

  • 39. Burks, T.
    et al.
    Avila, M.
    Akhtar, Farid
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Gothelid, M.
    Lansaker, P. C.
    Toprak, M. S.
    Muhammed, M.
    Uheida, A.
    Studies on the adsorption of chromium(VI) onto 3-Mercaptopropionic acid coated superparamagnetic iron oxide nanoparticles2014In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 425, p. 36-43Article in journal (Refereed)
    Abstract [en]

    Chromium (Cr) in the form of Cr(VI) is deemed toxic in water due to its mutagenic and carcinogenic properties. For the successful removal of Cr(VI), we demonstrate a novel adsorbent consisting of superparamagnetic iron oxide nanoparticles (SPION) functionalized with 3-Mercaptopropionic acid (3-MPA). Fourier transform infrared spectroscopy (FT-IR) confirmed the functionalization of nanoparticles and presence of sulfonate groups. Batch adsorption experiments showed that the functionalized adsorbent recovered 45 mg of Cr(VI)/g of 3-MPA coated SPION at initial concentration of 50 mg/L aqueous solution at pH 1 with less than 1% of Fe dissolution from SPION. The results from X-ray photoelectron spectroscopy confirmed that Cr(VI) chemisorbed onto the adsorbent. Hence, the XPS spectra did not indicate any reduction of Cr(VI) to Cr(III) upon adsorption. The adsorption data were better fitted for the Freundlich model. Moreover, the Cr(VI) adsorption kinetics on functionalized SPION followed a pseudo-second order rate, revealing chemisorption as the dominant mechanism. The high Cr(VI) removal, rapid adsorption kinetics and stability of adsorbent indicate that 3-MPA coated SPION could be an efficient adsorbent for the removal of Cr(VI).

  • 40. Buxhuku, Mika
    et al.
    Hansen, Vidar
    Oleynikov, Peter
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Gjonnes, Jon
    The Determination of Rotation Axis in the Rotation Electron Diffraction Technique2013In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 19, no 5, p. 1276-1280Article in journal (Refereed)
    Abstract [en]

    Methods to determine the rotation axis using the rotation electron diffraction technique are described. A combination of rotation axis tilt, beam tilt, and simulated experimental diffraction patterns with nonintegers zone axis has been used. Accurate knowledge of the crystallographic direction of the incident beam for deducing the excitation error of reflections simultaneously near Bragg positions is essential in quantitative electron diffraction. Experimental patterns from CoP3 are used as examples.

  • 41. Candelario, Victor M.
    et al.
    Moreno, Rodrigo
    Shen, Zhijian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Guiberteau, Fernando
    Ortiz, Angel L.
    Liquid-phase assisted spark-plasma sintering of SiC nanoceramics and their nanocomposites with carbon nanotubes2017In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, no 5, p. 1929-1936Article in journal (Refereed)
    Abstract [en]

    The appropriate conditions for liquid-phase assisted spark-plasma sintering (SPS) were identified for the fabrication of both SiC nanoceramics and their nanocomposites with carbon nanotubes (CNTs). A parametric study of the nanoceramics and nanocomposites with a given type of CNTs showed that the SPS temperature (as measured by the radial optical pyrometer) optimizing their densification, nanograin size, and mechanical properties is 1700 degrees C (soaking for a few minutes), below which there is incomplete densification, and above which there is obvious grain growth with no benefit in hardness or toughness in the case of the nanoceramics, and prejudicial to both properties in the case of the nanocomposites due to the CNT degradation. It was also shown that the nanocomposites have smaller nanograins than their nanoceramic counterparts, and are softer but tougher. Extension to nanocomposites with different types of CNTs confirmed these trends, and showed that the CNT features do not condition the densification, microstructure or mechanical properties of these nanocomposites.

  • 42.
    Cantillana, Tatiana
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Sundström, Maria
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Synthesis of 2-(4-chlorophenyl)-2-(4-chloro-3-thiophenol)-1,1-dichloroethene (3-SH-DDE) via Newman-Kwart rearrangement - A precursor for synthesis of radiolabeled and unlabeled alkylsulfonyl-DDEs2009In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, ISSN 0045-6535, Vol. 76, no 6, p. 805-810Article in journal (Refereed)
    Abstract [en]

    For the first time, a pathway for synthesis of 2-(4-chlorophenyl)-2-(4-chloro-3-thiophenol)-1,1-dichloroethene (3-SH-DDE), is presented. The compound is of particular interest as a precursor for synthesis of alkylsulfonyl-DDE containing different alkyl groups to discover structural activity relationships, and to promote synthesis of radiolabeled methylsulfonyl-DDE. 2-Chloro-5-methyl phenol was first methylated and further oxidized to the corresponding benzoic acid. The acid was reduced to the corresponding aldehyde (4-chloro-3-methoxy benzaldehyde) via 4-chloro-3-methoxy-benzene methanol. A lead/aluminium bimetal system was used to carry out the reductive addition of tetrachloromethane to 4-chloro-3-methoxy benzaldehyde to obtain 2,2,2-trichloro-1-(4-chloro-3-methoxyphenyl)ethanol,the desired starting material to synthesize the DDT-analogue (2-(4-chlorophenyl)-2-(4-chloro-3-methoxy-phenyl)-1,1,1-trichloroethane). Elimination of hydrochloric acid and removal of the methyl group led to the 3-OH-DDE. The Newman-Kwart rearrangement was applied to convert 3-OH-DDE to 3-SH-DDE via the dimethyl-carbarnothioate derivative. 3-SH-DDE is then used as a precursor for the radiolabel synthesis. The overall yield to acquire 3-SH-DDE after 11 steps was 3%. The step with the lowest yield was the DDT-analog synthesis with a yield of 30%. All other step had a yield of >50%. 3-SH-DDE was methylated with C-14-labeled iodomethane and oxidized by hydrogen peroxide to obtain 3-[C-14]MeSO2-DDE in an overall yield of 30%.

  • 43. Chaim, R.
    et al.
    Marder, R.
    Estournes, C.
    Shen, Zhijian James
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Densification and preservation of ceramic nanocrystalline character by spark plasma sintering2012In: Advances in Applied Ceramics: Structural, Functional and Bioceramics, ISSN 1743-6753, E-ISSN 1743-6761, Vol. 111, no 5-6, p. 280-285Article in journal (Refereed)
    Abstract [en]

    Spark plasma sintering is a hot pressing technique where rapid heating by dc electric pulses is used simultaneously with applied pressure. Thus, spark plasma sintering is highly suitable for rapid densification of ceramic nanoparticles and preservation of the final nanostructure. A considerable portion of the shrinkage during densification of the green compact of nanoparticles in the first and intermediate stages of sintering occurs during heating by particle rearrangement by sliding and rotation. Further densification to the final stage of sintering takes place by either plastic yield or diffusional processes. Full densification in the final stage of sintering is associated with diffusional processes only. Nanoparticle sliding and rotation during heating may also lead to grain coalescence, with much faster kinetics than normal grain growth at higher temperatures. Based on existing models for particle rearrangement and sliding, the contributions of these processes in conjunction with nanoparticle properties and process parameters were highlighted.

  • 44.
    Chamoun, Mylad
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Paulraj, Alagar Raj
    Kiros, Yohannes
    Svengren, Henrik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Göthelid, Mats
    Skårman, Björn
    Vidarsson, Hilmar
    Johansson, Malin
    Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron ElectrodesManuscript (preprint) (Other academic)
    Abstract [en]

    Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.

  • 45.
    Chamoun, Mylad
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Paulraj, Alagar Raj
    Skårman, Björn
    Vidarsson, Hilmar
    Kiros, Yohannes
    Noréus, Dag
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bifunctional Performance of Flow Assisted Rechargeable Iron-Air Alkaline BatteriesManuscript (preprint) (Other academic)
    Abstract [en]

    Low cost rechargeable iron-air alkaline batteries have all essential attributes to adapt for large scale energy storage applications. To actualize this implementation needs to overcome the challenges including poor efficiency and short cycle lifetime. Herein, suitable synthesized catalysts for the air electrode were investigated prior to iron-air cell testing. NiCo2O4 as sole catalyst proved exceptional bifunctional OER/ORR activity and stability over 440 h operation in air. This catalyst fitted into an electrolyte and oxygen flow assisted rechargeable iron-air prototype and performed stable over 588 h and had an energy density of 377 Wh kg-1 Fe. Inadequate coulombic efficiencies of 75 – 85% and energy efficiencies around 50% hurt the performance of the cell though and needed further development. Nevertheless, the findings in this work reports the opportunities and obstacles of the rechargeable iron-air battery.

  • 46.
    Chang, Jian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Processing 2D nanomaterials into inorganic-polymer composite films and fibers with well-defined properties2023Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    2D materials such as graphene, graphene oxide (GO), reduced graphene oxide (rGO) and MXene, possess unique properties, e.g., high carrier mobilities, mechanical flexibility, good thermal conductivity, and high optical and UV adsorption. They are potentially applicable in the fields of electronics, optoelectronics, catalysts, energy storage facilities, sensors, solar cells, lithium batteries, and so on. Normally, weak interactions and irregular packing or stacking of 2D layers may adversely offset or weaken to some extent their 2D effects such as mechanical and electrical properties at a macroscale. In this regard, it is required to spatially organize 2D materials into macroscopic forms of a well-defined shape (e.g. fibers, films, or 3D structures) in a way that can simultaneously preserve favorable 2D properties and functions shown at the nanoscale, and facilitate their compatibility with the state-of-the-art industrial processes. In my thesis, different types of 2D materials, here GO, rGO and MXene together with polymers were rationally assembled into functional composite materials. The synergistic molecular crosslinking strategy was utilized and controlled in such composite materials for the sake of better performance. My thesis mainly involves four parts:

     

    (1) Tough and strong GO composite films via a polycationitrile approach. The interface between GO nanosheets was reinforced via an intermolecular covalent crosslinking approach called “polycationitrile chemistry”. As a result, the mechanical performance of the as-prepared GO-based composite films was enhanced and maintained even at an extremely high relative humidity of 98%.

    (2) rGO-poly(ionic liquid) (PIL) composite films with high mechanical performance. The rGO/PIL composite films were designed and fabricated, where the synergistic supramolecular interactions between PIL and rGO layer enable high electrical conductivity and favorable mechanical properties.

    (3) Regenerated cellulose (RC)/MXene composite nanofibers for personal heating management. I harnessed a biodegradable RC-based fibrous matrix to bond with inorganic MXene nanoflakes via electrospinning method. Via hybridization, the as-formed RC/MXene nanofibers present a promotion of mechanical performance and photothermal conversion capability. As a personal heating cloth, it realizes energy-saving outdoor thermoregulatory.

    (4) RC/MXene solar absorber for solar-driven interfacial water evaporation. The RC/MXene composite nanofibers integrate considerable merits of excellent mechanical performance, wettability, and fast steam generation rate. The RC/MXene solar absorber offers significant values for the practical application of solar-driven steam generation.

    Download full text (pdf)
    fulltext
    Download (jpg)
    Omslagsframsida
  • 47. Chang, Ribooga
    et al.
    Svensson Grape, Erik
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Clairefond, Teva
    Tikhomirov, Evgenii
    Inge, A. Ken
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Cheung, Ocean
    Synthesis and characterization of sodium hafnium oxide (Na2HfO3) and its high-temperature CO2 sorption properties2023In: Journal of Materials Chemistry A, ISSN 2050-7488, E-ISSN 2050-7496, Vol. 11, no 14, p. 7617-7628Article in journal (Refereed)
    Abstract [en]

    The CO2 sorption properties of sodium hafnium oxide (Na2HfO3) were investigated in this study. Na2HfO3 was synthesized by solid-state synthesis using Na2CO3 and HfO2 as starting materials. The solid-state synthesized Na2HfO3 appeared structurally similar to other mixed metal oxides such as Na2ZrO3, but stacking disorder appeared to be common in Na2HfO3. The synthesis conditions, including the Na : Hf ratio (between 0.5 and 1.5 : 1), synthesis temperature, time and heating rate, were investigated to optimize CO2 sorption properties of Na2HfO3. The Na2HfO3 sorbent showed comparable CO2 uptake capacity, reaction rate and excellent cycling stability compared to other metal oxide sorbents. Na2HfO3 with Na : Hf = 1 : 1 and 1.25 : 1 showed the highest CO2 uptake among all Na2HfO3 samples obtained, with a CO2 uptake capacity of around 15 wt% (at 650–800 °C). The CO2 uptake rate of NHO-1 and NHO-1.25 was fast with over 80% of the equilibrium uptake reached within 250 s. Na2HfO3 remained stable even after 100 cycles with less than 3% difference in the CO2 uptake capacity between the 1st and 100th cycles. We performed kinetic analysis on the CO2 sorption data and found that the Avrami–Erofeev model fitted the kinetic data best among the kinetic models used. Apart from sorbent optimization, we showed that 3D-printing of Na2HfO3 : HfO2 mixtures can be used to produce structured Na2HfO3 sorbents with a slightly improved CO2 uptake rate and the same CO2 uptake capacity as the powder-based solid-state synthesized Na2HfO3 sorbent.

  • 48.
    Chen, Hong
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Deng, Youqian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yu, Zhengbao
    Zhao, Huishuang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Yao, Qingxia
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Zou, Xiaodong
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D Open-Framework Vanadoborate as a Highly Effective Heterogeneous Pre-catalyst for the Oxidation of Alkylbenzenes2013In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 24, p. 5031-5036Article in journal (Refereed)
    Abstract [en]

    Three three-dimensional (3D) open-framework vanadoborates, denoted as SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni, were synthesized using diethylenetriamine as a template. SUT-6-Zn, SUT-6-Mn, and SUT-6-Ni are isostructural and built from (VO)(12)O-6 B18O36(OH)(6) clusters bridged by ZnO5, MnO6, and NiO6 polyhedra, respectively, to form the 3D frameworks. SUT-6 is the first vanadoborate with a 3D framework. The framework follows a semiregular hxg net topology with a 2-fold interpenetrated diamond-like channel system. The amount of template used in the synthesis played an important role in the dimensionality of the resulting vanadoborate structures. A small amount of diethylenetriamine led to the formation of this first 3D vanadoborate framework, while an increased amount of diethylenetriamine resulted in vanadoborates with zero-dimensional (0D) and one-dimensional (1D) structures. SUT-6-Zn was proved to be an efficient heterogeneous precatalyst for the oxidation of alkylbenzenes.

  • 49. Chen, Tianyang
    et al.
    Banda, Harish
    Yang, Luming
    Li, Jian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). KTH Royal Institute of Technology, Sweden.
    Zhang, Yugang
    Parenti, Riccardo
    Dincă, Mircea
    High-rate, high-capacity electrochemical energy storage in hydrogen-bonded fused aromatics2023In: Joule, E-ISSN 2542-4351, Vol. 7, no 5, p. 986-1002Article in journal (Refereed)
    Abstract [en]

    Designing materials for electrochemical energy storage with short charging times and high charge capacities is a longstanding challenge. The fundamental difficulty lies in incorporating a high density of redox couples into a stable material that can efficiently conduct both ions and electrons. We report all-organic, fused aromatic materials that store up to 310 mAh g−1 and charge in as little as 33 s. This performance stems from abundant quinone/imine functionalities that decorate an extended aromatic backbone, act as redox-active sites, engage in hydrogen bonding, and enable a delocalized high-rate energy storage with stability upon cycling. The extended conjugation and hydrogen-bonding-assisted bulk charge storage contrast with the surface-confined or hydration-dependent behavior of traditional inorganic electrodes.

  • 50. Chen, Xiaozong
    et al.
    Liu, Leifeng
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Dong, Yuan
    Wang, Lianjun
    Chen, Lidong
    Jiang, Wan
    Preparation of nano-sized Bi2Te3 thermoelectric material powders by cryogenic grinding2012In: Progress in Natural Science, ISSN 1002-0071, E-ISSN 1745-5391, Vol. 22, no 3, p. 201-206Article in journal (Refereed)
    Abstract [en]

    A novel method for rapid preparation of Bi2Te3 nano-sized powders with an average particle size of about 7nm was developed. A starting powder mixture consisting of Bi2Te3 coarse particles of similar to 5mm was ground using cryogenic grinding in the liquid nitrogen. For comparison, the conventional high-energy ball milling was used to prepare the Bi2Te3 nano-sized powders. Sintering properties of as-prepared powders was investigated by spark plasma sintering (SPS). The effects of the preparation procedure on the crystallinity, morphology and structure were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that Bi2Te3 was not transformed into a non-equilibrium amorphous phase or decomposed during the cryogenic grinding process, and as-prepared nano-powders possessed excellent sinterability. This technique might also be applicable to other thermoelectric materials.

1234567 1 - 50 of 382
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf