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| 2. |
- Karlsson, Maths, 1978, et al.
(författare)
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Structure of Proton-Conducting Alkali Thio-Hydroxogermanates
- 2008
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 20:19, s. 6014-6021
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Tidskriftsartikel (refereegranskat)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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| 3. |
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| 4. |
- Adhikari, Arindam, et al.
(författare)
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Electrochemical behavior and anticorrosion properties of modified polyaniline dispersed in polyvinylacetate coating on carbon steel
- 2008
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 53:12, s. 4239-4247
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Tidskriftsartikel (refereegranskat)abstract
- Conducting polyaniline (Pani) was prepared in the presence of methane sulfonic acid (MeSA) as dopant by chemical oxidative polymerization. The Pani-MeSA polymer was characterized by FT-IR, UV-vis, X-ray diffraction (XRD) and impedance spectroscopy. The polyrner was dispersed in polyvinylacetate and coated oil carbon steel samples by a dipping method. The electrochemical behavior and anticorrosion properties of the coating, oil carbon steel in 3% NaCl were investigated using Open-circuit Potential (OCP) versus time of exposure, and electrochemical techniques including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and cyclic voltammetry (CV). During initial exposure, the OCP dropped about 0.35 V and the interfacial resistance increased several times, indicating I certain reduction of the polymer and oxidation of the steel surface. Later the OCP shifted to the noble direction and remained at a stable value during the exposure up to 60 days. The EIS monitoring also revealed the initial change and later stabilization of the coating. The stable high OCP and low coating impedance Suggest that the conducting polymer maintains its oxidative state and provides corrosion protection for carbon steel through out the investigated period. The polarization curves and CV show that the conducting polymer coating induces a passive-like behavior and greatly reduces the corrosion of carbon steel.
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| 5. |
- Bring, Torun, et al.
(författare)
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Potassium sulfate droplets and the origin of turbidity in alabaster glass
- 2006
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Ingår i: Glass Technology : European Journal of Glass Science and Technology A. ; 47:1, s. 15-18
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Farooq, Muhammad, 1973, et al.
(författare)
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EBSD and EDX analysis at the cladding-substrate interface of a laser clad railway wheel
- 2006
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Ingår i: International Journal of Materials Research. - : Walter de Gruyter GmbH. - 1862-5282 .- 2195-8556. ; 97:11, s. 1512-1518
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Tidskriftsartikel (refereegranskat)abstract
- Electron backscatter diffraction and energy-dispersive X-ray spectrometry were used to investigate the intermixed interface produced during laser cladding of a Co - Cr -Mo alloy on a steel substrate. A multi-component system and rapid solidification conditions together lead to a complex microstructure at the interface. The solidification of the cladding starts with the formation of an interface layer, which is about 75 mu m in thickness and consists of randomly oriented equiaxed grains of Co-Cr -Fe solid solution and martensite. Orientation analysis of the grains in the interface layer revealed that some grains have a special orientation relationship with the former austenite grains in the heat affected zone but the cladding is not formed by epitaxial growth on the substrate. Intermixing of the materials at the interface is providing a strong bond between the substrate and the cladding. For a grain from the interface layer to emerge as columnar grain in the cladding, it was determined that its crystallographic direction is not supposed to deviate more than 25 degrees from the sample normal direction.
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| 7. |
- Folkeson, Nicklas, 1981, et al.
(författare)
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Fireside corrosion of stainless and low alloyed steels in a waste-fired CFB boiler; The effect of adding sulphur to the fuel
- 2008
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Ingår i: Materials Science Forum. ; 595-598, s. 289-297
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion field tests have been carried out in the superheater region of a commercial waste-fired 75MW CFBC boiler using air cooled probes. Exposure time was 24 and 1000 hours. The effect of adding sulphur to the fuel on the corrosion of two high alloyed steels and a low alloyed steel was studied. The fuel consisted of 50% household waste and 50% industrial waste. The exposed samples were analyzed by ESEM/EDX and XRD. Metal loss was determined after 1000 hours. Both materials suffered significant corrosion in the absence of sulphur addition and the addition of sulphur to the fuel reduced corrosion significantly. The rapid corrosion of the high alloyed steel in the absence of sulphur addition is caused by the destruction of the chromium-containing protective oxide by formation of calcium chromate. Adding sulphur to the fuel inhibited chromate formation and increased the sulphate/chloride ratio in the deposit. Iron(II) chloride formed on the low alloyed steel regardless of whether sulphur was added or not.
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| 8. |
- Herrero, M. Antonia, et al.
(författare)
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Synthesis and characterization of a carbon nanotube−dendron series for efficient sirna delivery
- 2009
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 131:28, s. 9843-9848
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Tidskriftsartikel (refereegranskat)abstract
- A new series of dendron-functionalized multiwalled carbon nanotube (MWNT) derivatives, characterized by the presence of numerous positively charged tetraalkyl ammonium salts at the periphery of the dendron, has been synthesized. The positive charges on the MWNT surface, coupled with the unique ability of carbon nanotubes (CNTs) to penetrate cell membranes, make the new derivatives potentially ideal vectors for siRNA delivery. Using a fluorescently labeled, noncoding siRNA sequence, we demonstrate that cytoplasmic delivery of the nucleic acid is remarkably increased throughout the different dendron generations. The work reported here highlights the fact that dendron-functionalized CNTs can be rationally designed as efficient carriers of siRNA that can eventually lead to gene silencing.
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| 9. |
- Kessler, Vadim
(författare)
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The chemistry behind the sol-gel synthesis of complex oxide nanoparticles for bio-imaging applications
- 2009
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Ingår i: Journal of Sol-Gel Science and Technology. - : Springer Science and Business Media LLC. - 0928-0707 .- 1573-4846. ; 51, s. 264-271
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Tidskriftsartikel (refereegranskat)abstract
- The formation of nanoparticles in hydrolytic and non-hydrolytic reactions in organic media is treated as a borderline case of coordination chemistry equilibria. Metal cation complexes with O-donor ligands, such as metal alkoxides or b-diketonates and carboxylates, experience normally no kinetic hinders in re-structuring and aggregation. The steps of hydrolysis and condensation constitute in this case parts of one and the same kinetic phenomenon. Introduction of oxo-ligands during the first steps of hydrolytic or thermal decomposition leads thus in homogeneous processes to well-defined oligonuclear oxospecies. The structure of the latter is originating from the densest possible packing of cations and ligands and is not in any mean related to the structure of the original precursor molecules. The oxo-alkoxide molecules serve apparently as nuclei for the formation of larger aggregates that become phase separated and can be referred to as Micelles Templated by Self-Assembly of Ligands. The core of the latter is practically always crystalline or at least short-order organized, while the shell is, in the hydrolytic approach, constructed of hydrated amorphous oxide and ligands that stabilize the colloid via interaction with the solvent. The thermal treatment either in solution or for a dry xerogel is thus indispensable for preparation of fully crystalline particles and offers also an opportunity to control the final size of the particles via further aggregation. To guarantee the formation of complex oxide nanoparticles, the conditions insuring phase separation for each component have to be achieved. This means that the use of stoichiometric or super-stoichiometric quantities of water is required together with a solvent guaranteeing minimal solubility of hydrolyzed species. The approaches to complex oxide phases and oxides doped with lanthanide cations are discussed
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| 10. |
- Palmqvist, Lisa, 1968
(författare)
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Interactions between polymeric dispersants and colloidal ceramic surfaces
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increased use of environmentally acceptable chemicals and reduced energy consumption are two foreseeable demands within the ceramics industry. This will require the replacement of organic solvents and lowering of sintering temperatures. To meet these demands, new dispersants will be needed for colloidal processing of highly sinterable ceramic nanopowders. When selecting new dispersants, it is essential to understand the relations between molecular structures and adsorption properties of present dispersants. A deeper understanding of the properties of adsorbed layers, such as viscoelasticity, is also necessary to design dispersants for improved fluid properties and consolidation behavior of highly concentrated systems. The present work has been devoted to increasing the knowledge in this area. Interactions between polymeric dispersants and ceramic surfaces have been studied with a combination of surface characterization techniques (quartz crystal microbalance with dissipation (QCM-D), atomic force microscopy (AFM) and zeta potential) and rheological evaluations. More specifically, the efficiency of polyelectrolyte type dispersants represented by a poly(acrylic acid) and a lignosulphonate were compared to that of graft copolymers with nonionic chains of different molecular weights. A novel approach of this research work has been to use hydrophilic block and graft copolymers in aqueous systems and in mixtures of water and alcohols. The water content of adsorbed dispersant layers was determined by combining mass adsorption data from QCM-D measurements with mass optimization by viscosity measurements of alumina suspensions. Water was found to constitute up to 90% of the total adsorbed layer of a comb copolymer with long polyoxyethylene chains. Viscoelastic modeling also showed that these layers were viscous and thick, about 6 nm. It was also found that plastic behavior of wet consolidated bodies was obtained when a block copolymer with shorter polyoxyethylene chains was used, probably due to a lubrication effect from bound water. In contrast to this, both polyelectrolytes adsorbed in thin, highly rigid layers with relatively low water content, about 30%. Brittle behavior of wet bodies stabilized by poly(acrylic acid) indicated lack of lubrication effect with the polyelectrolyte dispersant. AFM showed that both polyelectrolytes gave efficient electrostatic stabilization, while the long comb copolymer provided steric stabilization. Moderate additions (25%) of isopropanol to water systems were shown to improve long-term stability of ceramic dispersions with slightly soluble species. This was demonstrated for an alumina suspension with magnesia added as a grain growth inhibitor.
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