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| 2. |
- Bring, Torun, et al.
(author)
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Potassium sulfate droplets and the origin of turbidity in alabaster glass
- 2006
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In: Glass Technology : European Journal of Glass Science and Technology A. ; 47:1, s. 15-18
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Journal article (peer-reviewed)abstract
- A study of the criteria required to manufacture multi-component semi-transparent silicate glasses, so called “alabaster” glass, has found that the optical effect is caused by non-crystal¬line potassium sulfate droplets. The droplets were characterized by use of XRD, SEM/EDX and Raman spectroscopy. The size range of the particles is in the order of 5-50 micrometers. It was found that the droplets consisted of potassium sulfate, even if other sulfate compounds were added to the glass. The amount of sulfate compound added, the melting temperature of the furnace and the melting time have significant effect on the optical density of the glass. The optical density of the glass can be correlated to the calculated surface tension of the host glass, suggesting that phase separation of a sulfate enriched liquid phase is part of the mecha¬nism forming the droplets. By adding pigments several different colours can be obtained, but the alabaster effect is not achieved during reducing conditions, thus it seems not possible to produce colours originating from reduced pigments. Pigments tested were Cr, Fe, Co, Cu, Au, Mo/Se, Nd and Ti/Ce/Se.
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| 3. |
- Lewin, Erik, et al.
(author)
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Industrialisation Study of Nanocomposite nc-TiC/a-C Coatings for Electrical Contact Applications
- 2009
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In: Plasma Processes and Polymers. - : WILEY-VCH Verlag GmbH & Co. - 1612-8850. ; 6:S1, s. S928-S934
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Journal article (peer-reviewed)abstract
- Nanocomposite nc-TiC/a-C coatings were prepared by non-reactive magnetron sputtering in industrial scale equipment, under varying deposition conditions in order to investigate upscaling and possible industrialisation. The coatings were found to have similar microstructure and performance compared to previous laboratory scale experiments. The samples were characterised with XRD, XPS and SEM as well with ball-on-disc, nanoindentation and electrical measurements. Coatings containing a small fraction of a-C matrix phase were found to have promising both electrical properties (rho < 400 mu Omega cm and contact resistances down to 0.34 m Omega at 40 N) and tribological properties (f < 0.3 for 10 000 laps).
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| 4. |
- Berggren, Gustav, et al.
(author)
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Synthesis, Characterization and Reactivity Study of a New Penta-Coordinated Mn(II) Complex
- 2009
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In: Applied Magnetic Resonance. - : Springer Science and Business Media LLC. - 0937-9347 .- 1613-7507. ; 36:1, s. 9-24
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Journal article (peer-reviewed)abstract
- A penta-coordinated Mn(II) compound [dqpMnCl2] (1) (dqp = 2,6-di-(8-quinoline-yl)-pyridine) has been synthesized and its X-ray crystallographic structure is reported here. Magnetic susceptibility measurements confirmed a high-spin Mn(II) (S = 5/2) center in 1. The X-band EPR spectrum of 1 in dimethylformamide solution exhibits widely distributed transitions in the spectral range from 0 to 700 mT with particularly well-resolved hyperfine lines due to the 55Mn (I = 5/2) nucleus. The abundance of highly resolved transition lines in the spectrum facilitated the electron paramagnetic resonance spectral simulation which revealed large zero-field splitting and g-anisotropies. When dissolved, 1 exists in equilibrium with a hexa-coordinated species, the latter probably resulting from disassociation of one chlorido-ligand allowing ligation of two solvent molecules. The redox behavior of 1 was studied and was compared to that of a structural analog for which water oxidation in the presence of a chemical oxidant has been shown. The results from water oxidation trials of 1 are discussed
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| 5. |
- Berggren, Gustav, et al.
(author)
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Two tetranuclear Mn-complexes as biomimetic models of the oxygen evolving complex in Photosystem II - A synthesis, characterisation and reactivity study
- 2009
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 45, s. 10044-10054
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Journal article (peer-reviewed)abstract
- In this work we report the preparation of two metallamacrocyclic tetranuclear manganese(II) complexes, [L1(4)Mn(4)](ClO4)(4) and [L2(4)Mn(4)](ClO4)(4) where L1 and L2 are the anions of the heptadentate ligands 2-((2-(bis(pyridin-2-ylmethyl) amino) ethyl)(methyl) amino) acetic acid and 2-(benzyl(2-(bis(pyridin-2-ylmethyl) amino) ethyl) amino) acetic acid), respectively. The complexes have been fully characterized by ESI-MS, elemental analysis, single-crystal X-ray diffraction, magnetic susceptibility, and EPR spectroscopy. Electrochemical reactions as well as reactions with different chemical redox reagents have been performed and a reversible two electron oxidation per manganese ion has been identified. The reaction of [L1(4)Mn(4)](ClO4)(4) with oxone or cerium(IV) results in the evolution of oxygen which makes this system interesting for future studies in the search for a functional mimic of the oxygen evolving complex in Photosystem II.
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| 6. |
- Kristensen, Emma, et al.
(author)
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Heparin coating durability on artificial heart valves studied by XPS and antithrombin binding capacity
- 2006
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In: Colloids and Surfaces B. - : Elsevier BV. - 0927-7765 .- 1873-4367. ; 49:1, s. 1-7
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Journal article (peer-reviewed)abstract
- The durability and functionality of a heparin coating on artificial heart valve leaflets were evaluated with X-ray photoelectron spectroscopy (XPS) and by the coatings’ capacity to bind antithrombin. Current methods for accelerated life-time testing are based on exposing leaflets to water solutions. In this paper a method is explored, in which heart valve leaflets were exposed to a continuous high shear rate (4 L/min) of human citrated plasma. It was found that the heparin coating was stable and wear resistant enough to still be present after 3 weeks and to have about the same antithrombin uptake as coatings not exposed to circulating plasma. It was, however, partly destroyed by the test as found using XPS. We suggest that heparin chains from the upper layer of heparin have been torn off from the carrier chain, in combination with loss of heparin conjugate and plasma deposition in patches. This study showed that XPS provides additional information to biological measurements such as antithrombin uptake. XPS is therefore a valuable technique not only to characterize biomaterials but also to evaluate the effect of a performance test.
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| 7. |
- Karlsson, Maths, 1978, et al.
(author)
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Structure of Proton-Conducting Alkali Thio-Hydroxogermanates
- 2008
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In: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 20:19, s. 6014-6021
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Journal article (peer-reviewed)abstract
- Using a combination of neutron diffraction, infrared spectroscopy, and first-principles calculations, we have investigated the structure of hydrated and dehydrated proton conducting alkali thio-hydroxogermanates of general formula M2GeS2(OH)2·yH2O (M = K, Rb, and Cs). The results show that the structure of hydrated and dry materials are basically the same, which confirms previous indications that the main effect of heating these materials is just a loss of water. We suggest that in the hydrated state the structure of these materials is built of dimers of thio-hydroxogermanate anions, with the water molecules acting as bridges between such dimers. In the dehydrated structure, the thio-hydroxogermanate anions instead form an extended network through the formation of interdimer hydrogen bonds through the −OH groups in the structure. The alkali ions are suggested to act as “space-fillers” in voids formed by the thio-hydroxogermanate anion dimers, in both the hydrated and the dehydrated state.
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| 8. |
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| 9. |
- Olabarrieta, Idoia, et al.
(author)
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Aging properties of films of plasticized vital wheat gluten cast from acidic and basic solutions
- 2006
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 7:5, s. 1657-1664
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Journal article (peer-reviewed)abstract
- In order to understand the mechanisms behind the undesired aging of films based on vital wheat gluten plasticized with glycerol, films cast from water/ethanol solutions were investigated. The effect of pH was studied by casting from solutions at pH 4 and pH 11. The films were aged for 120 days at 50% relative humidity and 23 C, and the tensile properties and oxygen and water vapor permeabilities were measured as a function of aging time. The changes in the protein structure were determined by infrared spectroscopy and size-exclusion and reverse-phase high-performance liquid chromatography, and the film structure was revealed by optical and scanning electron microscopy. The pH 11 film was mechanically more stable with time than the pH 4 film, the latter being initially very ductile but turning brittle toward the end of the aging period. The protein solubility and infrared spectroscopy measurements indicated that the protein structure of the pH 4 film was initially significantly less polymerized/ aggregated than that of the pH 11 film. The polymerization of the pH 4 film increased during storage but it did not reach the degree of aggregation of the pH 11 film. Reverse-phase chromatography indicated that the pH 11 films were to some extent deamidated and that this increased with aging. At the same time a large fraction of the aged pH 11 film was unaffected by reducing agents, suggesting that a time-induced isopeptide cross-linking had occurred. This isopeptide formation did not, however, change the overall degree of aggregation and consequently the mechanical properties of the film. During aging, the pH 4 films lost more mass than the pH 11 films mainly due to migration of glycerol but also due to some loss of volatile mass. Scanning electron and optical microscopy showed that the pH 11 film was more uniform in thickness and that the film structure was more homogeneous than that of the pH 4 film. The oxygen permeability was also lower for the pH 11 film. The fact that the pH 4 film experienced a larger and more rapid change in its mechanical properties with time than the pH 11 film, as a consequence of a greater loss of plasticizer, was presumably due to its initial lower degree of protein aggregation/ polymerization. Consequently, the cross-link density achieved at pH 4 was too low to effectively retain volatiles and glycerol within the matrix.
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| 10. |
- Zhu, Jiefang, 1973, et al.
(author)
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Nanostructured materials for photocatalytic hydrogen production
- 2009
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In: Current Opinion in Colloid and Interface Science. - : Elsevier BV. - 1359-0294 .- 1879-0399. ; 14:4, s. 260-269
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Journal article (peer-reviewed)abstract
- Photocatalytic hydrogen (H-2) production represents a very promising but challenging contribution to a clean, sustainable and renewable energy system. The photocatalyst material plays a key role in photocatalytic H-2 production, and it has proven difficult to obtain corrosion resistant, chemically stable, visible light harvesting and highly efficient photocatalysts, which have their band edges matching the O-2 and H-2 production levels. Nanoscience and nanotechnology are opening a new vista in the development of highly active, nanostructured photocatalysts with large surface areas for optimized light absorption, minimized distances (or times) for charge-carrier transport, and further favorable properties. Our focus here is on recently developed nanostructured photocatalysts. In particular. the particle size, chemical composition (including dopants), microstructure, crystal phase. morphology, surface modification, bandgap and flat-band potential of the nanophotocatalysts have shown a visible effect on photocatalytic H-2 production rates, which may be further increased by adding sensitizers, cocatalysts or scavengers. Finally, potential directions required to push this research field a step further are highlighted. (
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