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  • 151.
    Paulsson, Heléne
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Berggrund, Malin
    KTH, Tidigare Institutioner                               , Kemi.
    Fischer, Andreas
    KTH, Tidigare Institutioner                               , Kemi.
    Kloo, Lars A.
    KTH, Tidigare Institutioner                               , Kemi.
    Iodoargentates and Cuprates Stabilized by Sulphonium Cations with Long Alkyl Chains2003Inngår i: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, nr 12, s. 2352-2355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    [DodMe2S]22AgI3 and [DodMe2S] Ag2I3 were obtained from mixtures of dodecyldimethylsulfonium iodide and silver iodide in acetonitrile solution. [DodMe2S]2AgI3 crystallizes in the orthorhombic crystal system, space group Pbca and contains trigonal planar anions AgI32-, while [DodMe2S] Ag2I3 crystallizes in the triclinic crystal system, space group P1, and consists of polymeric anions 1(Ag2I3)-. In both structures, the sulfonium cations form a layer of parallel and interpenetrating dodecyl chains with the sulfoniumdimethyl groups on both sides of the layer. [DodMe2S]2CuI3 was obtained from dodecyldimethylsulfonium iodide and copper iodide mixtures and is isostructural with the corresponding silver compound.

  • 152.
    Paulsson, Heléne
    et al.
    KTH, Tidigare Institutioner, Kemi.
    Berggrund, Malin
    KTH, Tidigare Institutioner, Kemi.
    Fischer, Andreas
    KTH, Tidigare Institutioner, Kemi.
    Kloo, Lars A.
    KTH, Tidigare Institutioner, Kemi.
    Novel Layered Structures Formed by Iodocuprate Clusters Stabilized by Dialkylsulphide Ligands2004Inngår i: Zeitschrift für Anorganische und Allgemeines Chemie, ISSN 0044-2313, E-ISSN 1521-3749, Vol. 630, nr 3, s. 413-416Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    From solutions of copper iodide and dodecyldimethyl-sulphonium iodide in acetonitrile, single crystals of [Cu4I4-(DodecylMeS) 4] (1) and [Cu3I4(DodecylMeS) 3](DodecylMe2S) (2) could be obtained. Both compounds crystallize in the triclinic crystal system, space group P1 (1: a = 957.23(1), b = 967.25(2), c = 3818.38(6) pm, α = 90.3837(6)°, β = 86.4687(7)°, γ = 75.0996(7)°; 2: a = 874.23(1), b = 979.29(1), c = 4388.75(4) pm, α = 90.4472(3)°, β = 94.7088(3)°, γ = 116.1162(3)°). 1 consists of tetrahedral Cu4 clusters, which are capped by four iodide ions over the tetrahedral faces. 2 contains trigonal Cu3 clusters, which are coordinated by four iodide ions, one centered over the plane, three bridging over the edges of the Cu3 triangle. In both compounds, the S atoms of (DodecylMeS) ligands coordinate to the Cu atoms. In 2, a (DodecylMe2S) cation is also present.

  • 153.
    Paulsson, Heléne
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Fischer, Andreas
    KTH, Tidigare Institutioner                               , Kemi.
    Kloo, Lars A.
    KTH, Tidigare Institutioner                               , Kemi.
    Bis[bis(12-crown-4)potassium] hexaiodotetracuprate(I)2004Inngår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 60, nr 5, s. M548-M550Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    From 12-crown-4, KI, and CuI in an acetone solution, the title compound, [K(C16H32O8)(2)](2)[Cu4I6], was obtained. It consists of sandwich-type [(12-crown-4)(2)K](+) complex cations and polymeric [Cu4I6](2-) anions. The latter consist of CuI4 tetrahedra, which share edges and faces to form infinite chains.

  • 154.
    Paulsson, Heléne
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Long-Term Stability Studies under Indoor Light Conditions of Dye-Sensitized Nanocrystalline Solar Cells Containing Room-Temperature Ionic Liquid Electrolytes2005Artikkel i tidsskrift (Annet vitenskapelig)
  • 155.
    Paulsson, Heléne
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Hagfeldt, Anders
    Department of Physical Chemistry, Uppsala University.
    Kloo, Lars A.
    KTH, Tidigare Institutioner                               , Kemi.
    Molten and solid trialkylsulfonium iodides and their polyiodides as electrolytes in dye-sensitized nanocrystalline solar cells2003Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 107, nr 49, s. 13665-13670Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Potential new electrolytes for dye-sensitized nanocrystalline solar cells (DNSCs) of Gratzel type based on trialkylsulfonium iodides have been investigated. Room temperature molten salts of (Et2MeS)I, (Bu2MeS)I, and (Bu2EtS)I, with iodine in low concentrations, revealed good conducting abilities. DNSCs using iodine-doped (Bu2MeS)l as electrolyte achieved an overall light-to-electricity conversion efficiency of 3.7% in simulated AM 1.5 solar light at a light intensity of 0.1 Sun. The effects from varying the temperature during the IN measurements were studied, as well as the effects of 4-tert-butylpyridine treatment of the electrodes.

  • 156.
    Paulsson, Heléne
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Hagfeldt, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Photoelectrochemical Studies of Nanocrystalline Solar Cells Sensitized with Polypyridyl-Ruthenium Complexes and Containing Room-Temperature Ionic Liquids or an Organic Liquid-Based Electrolyte2005Artikkel i tidsskrift (Annet vitenskapelig)
  • 157.
    Paulsson, Heléne
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Hagfeldt, Anders
    Department of Physical Chemistry, Uppsala University.
    Boschloo, Gerrit
    Department of Physical Chemistry, Uppsala University.
    Electron transport and recombination in dye-sensitized solar cells with ionic liquid electrolytes2006Inngår i: Journal of Electroanalytical Chemistry, ISSN 0022-0728, E-ISSN 1873-2569, Vol. 586, nr 1, s. 56-61Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electron transport and recombination in dye-sensitized TiO2 solar cells with different electrolytes have been investigated. The electrolytes were based on iodine-doped ionic liquids (diethylmethylsulphonium, dibutylmethylsulphonium or 3-hexyl-1-methylimidazolium iodide) or an organic solvent (3-methoxypropionitrile with LiI, I-2 and 1-methylbenzimidazole). The most viscous electrolytes showed a clear limitation in photocurrent, which can be attributed to a low diffusion coefficient for the triiodide that transports positive charge to the counter electrode. No essential difference was found in the electron transport properties of the solar cells, which appear to be dominated by the properties of the nanostructured TiO2 film. The intensity-modulated photocurrent response was strongly affected by current saturation. This is proposed being caused by recombination processes. The electron lifetime is depending on the type of cation used in the ionic liquid, where bulky, less absorptive cations seem to give longer lifetimes.

  • 158. Pašti, I. A.
    et al.
    Skorodumova, Natalia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Flerskalig materialmodellering. Uppsala University, Sweden.
    Structural, electronic, magnetic and chemical properties of B-, C- and N-doped MgO(001) surfaces2016Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, nr 1, s. 426-435Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Doping of simple oxide materials can give rise to new exciting physical and chemical properties and open new perspectives for a variety of possible applications. Here we use density functional theory calculations to investigate the B-, C- and N-doped MgO(001) surfaces. We have found that the investigated dopants induce magnetization of the system amounting to 3, 2 and 1 μB for B, C and N, respectively. The dopants are found to be in the X2- state and tend to segregate to the surface. These impurity sites also present the centers of altered chemical reactivity. We probe the chemisorption properties of the doped MgO(001) surfaces with the CO molecule and atomic O. The adsorption of CO is much stronger on B- and C-doped MgO(001) compared to pure MgO(001) as the impurity sites serve as potent electron donors. The situation is similar to the case of atomic oxygen, for which we find the adsorption energy of -8.78 eV on B-doped MgO(001). The surface reactivity changes locally around the dopant atom, which is mainly restricted to its first coordination shell. The presented results suggest doped MgO as a versatile multifunctional material with possible use as an adsorbent or a catalyst.

  • 159.
    Pehrman, Reijo
    et al.
    European Commission, Joint Research Centre, Institute for Transuranium Elements.
    Amme, Marcus
    European Commission, Joint Research Centre, Institute for Transuranium Elements.
    Roth, Olivia
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Ekeroth, Ella
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Oxidative dissolution of actinide oxides in H2O2 containing aqueous solution: A preliminary study2010Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 397, nr 1-3, s. 128-131Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxidative dissolution Of Spent nuclear fuel is an important issue in the safety assessment of a future geological repository for Spent nuclear fuel. Although UO2 Constitutes, in terms of mass, the majority of the spent fuel material, its main radiotoxicity is (after extended storage times) contained in actinides with half lives shorter than that of 238-uranium, such as isotopes of Np and Pu. Relatively little information is available on the dissolution behavior of Np and Pu in comparable environments. This work investigates the oxidative dissolution of NpO2 and PuO2 in non-complexing aqueous solutions containing H2O2 and compares their behavior with that of UO2. We have found that oxidative dissolution takes place for all three actinides in the presence of H2O2. Based on the obtained dissolution rates, we Would not expect the dissolution of the actinides to be congruent. Instead, in a System Without complexing agent, the release rates of Np and Pu are expected to be lower than the U release rate.

  • 160.
    Pehrman, Reijo
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Trummer, Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Lousada, Cláudio
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    On the redox reactivity of doped UO2 pellets: Influence of dopants on the H2O2 decomposition mechanism.Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The reactivity of doped UO2 such as SIMFUEL, Y2O3 doped UO2 and Y2O3/Pd doped UO2 towards H2O2 has been shown to be fairly similar to that of pure UO2. However, the oxidative dissolution yield, i.e. the ratio between the amount of dissolved uranium and the amount of consumed H2O2 is significantly lower for doped UO2. The rationale for the observed differences in dissolution yield is a difference in the ratio between the rates of the two possible reactions between H2O2 and the doped UO2. In this work we have studied the effect of doping on the two possible reactions, electron transfer and catalytic decomposition. The catalytic decomposition was studied by monitoring the hydroxyl radical production (the primary product) as a function of time. The redox reactivity of the doped pellets was studied by using MnO4- and IrCl62- as model oxidants, only capable of electron transfer reaction with the pellets. In addition, the activation energies for oxidation of UO2 and SIMFUEL by MnO4- were determined experimentally. The experiments show that the rate of catalytic decomposition of H2O2 varies by 30 % between the fastest and the slowest material. This is a negligible difference. The redox reactivity study shows that doping of UO2 influences the redox reactivity of the pellet. This is further illustrated by the observed activation energy difference for oxidation of UO2 and SIMFUEL by MnO4-. The redox reactivity study also shows that the sensitivity to dopants increases with decreasing reduction potential of the oxidant. These findings imply that the relative impact of radiolytic oxidants in oxidative dissolution of spent nuclear fuel must be reassessed taking the actual fuel composition into account.

  • 161.
    Pei, Zhichao
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Yu, Hui
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Theurer, Matthias
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Waldén, Annelie
    KTH, Skolan för bioteknologi (BIO).
    Nilsson, Peter
    KTH, Skolan för bioteknologi (BIO).
    Yan, Mingdi
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Ramström, Olof
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Photogenerated Carbohydrate Microarrays2007Inngår i: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 8, nr 2, s. 166-168Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Chemical Equation Presented) Sugars in a row. A new strategy for carbohydrate microarrays based on photochemical ligation of perfluorophenylazide-derivatized carbohydrates to PEO surfaces is presented. It constitutes a controllable and robust method of array fabrication, on the carbohydrate chemistry and on the surface-chemistry levels, and the resulting carbohydrate arrays can be efficiently used to reveal the recognition patterns of carbohydrate-binding proteins.

  • 162.
    Puranen, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Near field immobilization of selenium oxyanions2010Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The topic of this doctoral thesis is the potential near field immobilization of the radionuclide 79Se after intrusion of groundwater into a spent nuclear fuel canister in a repository. 79Se is a non naturally occurring long lived selenium isotope formed as a result of fission in nuclear fuel. Given the long half life (~3 x 105 y) and that the oxyanions of selenium are expected to be highly mobile and potentially difficult toimmobilize the isotope is of interest for the long term safety assessment of high level waste repositories. In this work the near field has been limited to the study of processes at or near the UO2 surface of (simulated) spent nuclear fuel and to processes occurring at or near the surface of iron (canister material) corroding under anoxic conditions. Selenite (HSeO32-) was found to adsorb onto palladium (simulated noble metal inclusion in spent nuclear fuel). Under hydrogen atmosphere selenite was reduced to elemental selenium with a rate constant of ~2 x 10-9 m s-1 (with respect to the Pd surface, 24 bar H2) forming colloidal particles. The rate constant of selenite reduction was increased by about two orders of magnitude to ~2.5 x 10-7 m s-1 (with respect to the Pd surface, 10 bar H2) for a UO2 surface doped with Pd particles, indicating that UO2 is an efficient co-catalyst to Pd. Selenate (SeO42-) was neither adsorbed nor reduced in the presence of Pd, UO2 and hydrogen. In the iron corrosion studies selenate was found to become reduced to predominantly elemental Se in the presence of a pristine iron surface. Iron covered by a corrosion layer of magnetite did however appear inert with respect to selenate whereas selenite was reduced. The reduction of dissolved uranyl into UO2 by the corroding iron surfaces was found to significantly increase the removal rate of selenite as well as selenate. The uranyl was found to transiently transform the outer iron oxide layers on the iron, forming a reactive mixed Fe(II)/Fe(III) oxyhydroxide (Green rust). Exchanging the solution and increasing the carbonate content (from 2 mM to 20 mM NaHCO3) only resulted in a minor, transient remobilization of uranium. Addition of H2O2 did however result in a significant release of uranium as well as selenium from the iron oxide surfaces. An irradiation experiment was also performed confirming the one electron reduction barrier of selenate as an important factor in systems where selenate reduction would be thermodynamically favorable.

  • 163.
    Puranen, Anders
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Remobilization of U and Se reductively immobilized on iron oxide surfacesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

     

     

     

     

     

     

     

    In this work we have studied the possible remobilization of U and Se reductively immobilized on iron oxide surfaces experimentally. Samples consisting of reductively immobilized U and Se (carefully characterized in previous studies) we exposed to aqueous solutions containing HCO3- and HCO3- and H2O2. HCO3- increases the solubility of U(VI) and H2O2 will oxidize U(IV) to U(VI). Exposure to a HCO3- solution revealed a transient increase in the uranium concentration which can probably attributed to detachment of loosely bound UO2 particles upon addition of the new solution. Upon addition of H2O2, the concentrations of U and Se increased fairly rapidly indicating that oxidative dissolution is taking place. The rate of uranium release was well in line with what could be expected from the kinetics of oxidative dissolution of UO2 by H2O2. The Se/U ratio increases with leaching time approaching the overall original composition of the immobilized surface. Hence, oxidative dissolution of the immobilized U and Se is not congruent. Furthermore, the iron oxide surface exposed to the solution after oxidative removal of the immobilized Se and U, appears to be less reactive towards Se and U in solution compared to the original oxide surface. Consequently, the oxidative remobilization process has also affected the iron oxide. These findings suggest that oxidative re-mobilization of reductively immobilized redox sensitive radionuclides is aprocess of potential impact in a deep geological repository for spent nuclear fuel.

  • 164.
    Puranen, Anders
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Dähn, Rainer
    Cui, Daqing
    Reduction of selenite and selenate on anoxically corroded iron and the synergistic effect of uranyl reduction2010Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 406, nr 2, s. 230-237Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work the uptake of dissolved selenium in the form of selenite and selenate on iron covered by amagnetite corrosion layer and the effect of dissolved uranyl on this process is studied. Under simulatedanoxic groundwater conditions (bicarbonate and chloride solutions) no immobilization of selenate was found in the absence of uranyl whereas selenite was immobilized, albeit slowly. When uranyl was present, it was found to become reduced and greatly enhanced the rate of reductive immobilization of the dissolved selenite as well as selenate. The increased rate of immobilization is proposed to be due to the oxidative transformation of the passifying magnetite layer as the uranyl is reduced with the observed formation of a transient mixed Fe(II)/Fe(III) oxyhydroxide phase. The iron oxide, and selenium speciation on the surfaces were investigated by Raman spectroscopy. X-ray Absorption Spectroscopy was used to determine the oxidation state of the selenium and uranium on the surfaces.

  • 165. Purgel, Mihaly
    et al.
    Maliarik, Mikhail
    Glaser, Julius
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Platas-Iglesias, Carlos
    Persson, Ingmar
    Toth, Imre
    Binuclear Pt-TI Bonded Complex with Square Pyramidal Coordination around Pt: A Combined Multinuclear NMR, EXAFS, UV-Vis, and DFT/TDDFT Study in Dimethylsulfoxide Solution2011Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, nr 13, s. 6163-6173Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure and bonding of a new Pt-Tl bonded complex formed in dimethylsulfoxide (dmso), (CN)(4)Pt-Tl(dmso)(5)(+), have been studied by multinuclear NMR and UV vis spectroscopies, and EXAFS measurements in combination with density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. This complex is formed following the equilibrium reaction Pt(CN)(4)(2-) + Tl(dmso)(6)(3+) reversible arrow (CN)(4)Pt-Tl(dmso)(5)(+) + dmso. The stability constant of the Pt-Tl bonded species, as determined using C-13 NMR spectroscopy, amounts to log K = 2.9 +/- 0.2. The (NC)(4)Pt-TI(dmso)(5)(+) species constitutes the first example of a Pt-Tl bonded cyanide complex in which the sixth coordination position around Pt (in trans with respect to the Tl atom) is not occupied. The spectral parameters confirm the formation of the metal metal bond, but differ substantially from those measured earlier in aqueous solution for complexes (CN)(5)Pt-Tl(CN)(n)(H2O)(x)(n-)(n = 0-3). The Tl-205 NMR chemical shift, delta = 75 ppm, is at extraordinary high field, while spin spin coupling constant, J(Pt-Tl) = 93 kHz, is the largest measured to date for a Pt-Tl bond in the absence of supporting bridging ligands. The absorption spectrum is dominated by two strong absorption bands in the UV region that are assigned to MMCT (Pt -> Tl) and LMCT (dmso -> Tl) bands, respectively, on the basis of MO and TDDFT calculations. The solution of the complex has a bright yellow color a's a result of a shoulder present on the low energy side of the band at 355 nm. The geometry of the (CN)(4)Pt-Tl core can be elucidated from NMR data, but the particular stoichiometry and structure involving the dmso ligands are established by using Tl and Pt L-III-edge EXAFS measurements. The Pt-Tl bond distance is 2.67(1) angstrom, the Tl-O bond distance is 2.282(6) angstrom, and the Pt-C-N entity is linear with Pt C and Pt center dot center dot center dot N distances amounting to 1.969(6) and 3.096(6) angstrom, respectively. Geometry optimizations on the (CN)(4)Pt-Tl(dmso)(5)(+) system by using DFT calculations (B3LYP model) provide bond distances in excellent agreement with the EXAFS data. The four cyanide ligands are located in a square around the Pt atom, while the Tl atom is coordinated in a distorted octahedral fashion with the metal being located 0.40 angstrom above the equatorial plane described by four oxygen atoms of dmso ligands. The four equatorial Tl-O bonds and the four cyano ligands around the Pt atom are arranged in an alternate geometry. The coordination environment around Pt may be considered as being square pyramidal, where the apical position is occupied by the Tl atom. The optimized geometry of (CN)(4)Pt-Tl(dmso)(5)(+) is asymmetrical (C-1 point group). This low symmetry might be responsible for the unusually large NMR linewidths observed due to intramolecular chemical exchange processes. The nature of the Pt-Tl bond has been studied by MO analysis. The metal metal bond formation in (CN)(4)Pt-Tl(dmso)(5)(+) can be simply interpreted as the result of a Pt(5d(z2))(2)-> Tl(6s)(0) donation. This bonding scheme may rationalize the smaller thermodynamic stability of this adduct compared to the related complexes with (CN)(5)Pt-Tl entity, wher the linear C-Pt-Tl unit constitutes a very stable bonding system.

  • 166.
    Qiu, Ping
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Multi-Analysis of Initial Atmospheric Corrosion of Brass Induced by Carboxylic Acids2011Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 158, nr 6, s. C172-C177Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The initial atmospheric corrosion of a brass (Cu-20Zn) alloy induced by carboxylic (formic, acetic, and propionic) acids has been investigated through surface or near-surface analytical techniques. The main reaction products identified were Zn-carboxylate and a Cu2O-like layer. Their formation kinetics reveal the galvanic effects due to Volta potential variations along the surface, which result in corrosion cells with central anodic formation of zinc-carboxylate and peripheral cathodic formation of Cu2O. The corrosion cell size increases as propionic < acetic < formic acid, reflecting the dependence on ionic conductivity of the aqueous adlayer.

  • 167.
    Randström, Sara
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    New Materials for the Molten Carbonate Fuel Cell2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [sv]

    Smältkarbonatbränslecellen (MCFC) är en högtemperaturbränslecell för stationära applikationer. Den har samma höga totalverkningsgrad som konventionella kraftvärme-anläggningar, men kan byggas i mindre moduler (från 250 kWe). De små modulerna och den bränsleflexibilitet (naturgas, biogas, etanol, diesel) som MCFC har, gör den intressant för exempelvis industrier med organiska restprodukter och höga krav på tillförlitlighet. Den höga temperaturen och närvaron av en saltsmälta gör dock materialdegradering till en viktig faktor för forskning och utveckling inom området. För även om de fälttester som nyligen gjorts har visat på att vissa av degraderingsprocesserna är mindre allvarliga än förväntat, finns fortfarande ett behov av utveckling för att sänka kostnaderna och förlänga livstiden.

    I första delen av detta arbete undersöktes material för olika delar av cellen inom ramarna för EU-projektet IRMATECH. Materialen ansågs vara interessanta alternativ till de nuvarande materialen på grund av deras lägre kostnad och/eller bättre prestanda. Två alternativa anodströmtilledarmaterial undersöktes. För anodströmtilledaren är korrosionen och den elektriska resistansen av det eventuella oxidlagret nyckelparametrar. Dessa parametrar undersöktes och utvärderades. Fastän de båda alternativa materialen hade oxidlager med låg resistans, fanns indikationer på korrosionsprocesser som kan äventyra materialets långtidsstabilitet.

    För katodmaterialet, NiO, har upplösningen varit problemet. De upplösta nickeljonerna fälls ut i elektrolyten och bildar dendriter som kan kortsluta cellen. Därför undersöktes nickelupplösningen hos tre alternativa katodmaterial. Det mest lovande materialet, en nickeloxid-katod dopad med magnesium och järn testades i en singelcell för att studera elektrokemisk prestanda, morfologi och områden där nickelutfällning skett. Resultaten visade att prestandan var jämförbar med NiO, men att den mekaniska stabiliteten måste undersökas ytterligare.

    I ”wet-seal”-området är det rostfria stålet belagt med ett aluminiumskikt för att skydda det från den mycket korrosiva miljön. Tillverkningsprocesserna för dessa aluminiumbeläggningar har hittills varit dyra och komplexa. Därför utvärderades en alternativ tillverkningsprocess. Beläggningen, studerad i både reducerande och oxiderande miljö visade en tendens till att spricka och därmed exponera det underliggande rostfria stålet. Detta berodde troligtvis på en manuell beläggningsprocess som resulterade i ett inhomogent ytskikt.

    I den andra delen av arbetet föreslogs en alternativ tillverkningsmetod, baserad på nyligen publicerade resultat där man elektrodeponerat aluminium från jonvätskor. Dessa har ett större katodiskt fönster än vatten och möjliggör därför elektrodeponering av elektropositiva material. För att göra processen industrivänlig provades ett alternativ till den vanligen använda aluminiumtrikloriden. Det visade sig dock att påverkan av miljön på stabiliteten hos jonvätskan behövde undersökas innan några material kunde tillverkas. Vatten i kombination med syre visade sig ha en stor inverkan på den katodiska strömtätheten. I frånvaro av dessa komponenter var jonvätskan mycket stabil.

  • 168.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Appetecchi, Giovanni Battista
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Moreno, Angelo
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    Passerini, Stefano
    Agency for New Technologies, Energy and the Environment (ENEA), Energy Technologies, Rome, Italy.
    The influence of air and its components on the cathodic stability of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide2007Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 4, s. 1837-1842Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although water- and air-stable ionic liquids have been in use for some years, experiments found in the literature are still per-formed in inert gas with ppm levels of oxygen and water. In this study, the influence of different environments (vacuum, argon, nitrogen, air and oxygen and water) on the cathodic electrochemical window of the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) is reported and compared with investigations and processes found in the literature. The investigation indicates that this ionic liquid is highly stable in a vacuum and under argon flow. However, its cathodic stability is reduced in nitrogen and dry air. The simultaneous presence of water and air strongly affected the useful electrochemical window, as seen previously for imidazolium-based ionic liquids.

  • 169.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Capobianco, Paolo
    Ansaldo Fuel Cells S.p.A.
    Corrosion of anode current collectors in molten carbonate fuel cells2006Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 160, nr 2, s. 782-788Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Corrosion of metallic parts is one of the life-time limiting factors in the molten carbonate fuel cell. In the reducing environment at the anode side of the cell, the corrosion agent is water. As anode current collector, a widely used material is nickel clad on stainless steel since nickel is stable in anode environment, but a cheaper material is desired to reduce the cost of the fuel cell stack. When using the material as current collector one important factor is a low resistance of the oxide layer formed between the electrode and the current collector in order not to decrease the cell efficiency. In this study, some candidates for anode current collectors have been tested in single cell molten carbonate fuel cells and the resistance of the oxide layer has been measured. Afterwards, the current collector was analysed in scanning electron microscope (SEM) equipped with energy dispersive spectrometer (EDS). The results show that the resistances of the formed oxide layers give a small potential drop compared to that of the cathode current collector.

  • 170.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Scaccia, Silvera
    Hydrogen and Fuel Cells Project, ENEA.
    Investigation of a Ni(Mg,Fe)O Cathode for Molten Carbonate Fuel Cell Applications2007Inngår i: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 7, nr 3, s. 218-224Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Molten Carbonate Fuel Cell (MCFC) converts chemical energy into electrical energy and heat. Since the working temperature is high, less expensive materials can be used compared to low temperature fuel cells. However, the components of the fuel cell still need to be improved. The dissolution of the NiO cathode has, for a long time, been a problem for the Molten Carbonate Fuel Cell (MCFC) and this area is still the focus for MCFC component research. In this study, solubility measurements for a NiC) cathode material doped with magnesium and iron are carried out and the electrochemical performance of this cathode material is tested under the standard conditions of the MCFC over 2,000 hours and compared with the performance of a standard NiO cathode. After operation, nickel precipitation in the matrices is investigated. It is concluded that a NiO cathode with magnesium and iron could be a viable candidate material for the MCFC.

  • 171.
    Randström, Sara
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Montanino, Maria
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Appetecchi, Giovanni B.
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Lagergren, Carina
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Tillämpad elektrokemi.
    Moreno, Angelo
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Passerini, Stefano
    Agency for the New Technologies, the Energy and the Environment (ENEA), Energy Technologies, Renewable Sources and Energy Saving Department (TER), Rome, Italy.
    Effect of water and oxygen traces on the cathodic stability of N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide2008Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 22, s. 6397-6401Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Although research in the field of ionic liquids for electrochemical applications has led to a deeper knowledge in their electrochemical properties, doubts in the interpretation of the experimental results are still encountered in the literature due to the poor control of the experimental conditions and/or to the limited number of experiments conducted. In this work, the effect of water and oxygen traces on the cathodic stability window of hydrophobic, air-stable ionic liquids composed of N-alkyl-N-methylpyrrolidinium (PYR1A') cations and bis(trifluoromethanesulfonyl)imide (TFSI-) anion, is reported. The extensive investigation performed by linear sweep voltarnmetry (LSV) and cyclic voltarnmetry (CV) indicates that the TFSl- anion is cathodically stable if the ionic liquid is pure and dry. The N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquids investigated showed featureless cathodic linear sweep voltarnmetry curves before the massive cation decomposition took place at very low potentials.

  • 172.
    Raza, Rizwan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Wang, Xiaodi
    Ma, Ying
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Study on calcium and samarium co-doped ceria based nanocomposite electrolytes2010Inngår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, nr 19, s. 6491-6495Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Calcium co-doped SDC-based nanocomposite electrolyte (Ce0.8Sm0.2-xCaxO2-delta-Na2CO3) was synthesized by a co-precipitation method. The microstructure and morphology of the composite electrolytes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM), and thermal properties were determined with differential scanning calorimetry (DSC). The particle size, as shown by TEM imaging, was 5-20 nm, which is in a good agreement with the SEM and XRD results. The co-doping effect on both interfaces of the composite electrolyte and doped bulk effect inside the ceria was studied. The excellent performance of the fuel cell was about 1000 mW cm(-2) at 560 degrees C and at the very low temperature of 350 degrees C the power density was 200 mW cm(-2). This paper may give a new approach to develop functional nanocomposite electrolyte for low-temperature solid oxide fuel cell (LTSOFC). (C) 2010 Elsevier B.V. All rights reserved.

  • 173.
    Riihimäki, Eva-Stina
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    A Theoretical Investigation of the Octapeptide Region in the Human Prion Protein2007Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [sv]

    Den kopparbindande egenskapen hos prionproteiner är sannolikt kopplad till proteinets funtion. Det mänskliga prionproteinet innehåller ett kopparbindande oktapeptidområde, där PHGGGWGQ-sekvensen upprepas fyra gånger i följd. Syftet med detta arbete är att undersöka strukturen och dynamiken i oktapeptidområdet genom att använda teoretiska metoder. Med kvantkemisk strukturoptimering genomfördes en detaljerad jämförelse av växelverkan mellan flera katjoner och det kopparbindande området. Enligt dessa beräkningar är rodium(III) en möjlig ersättare för koppar(II) i NMR-specktroskopiska koordinationsstudier. Alternativa solvatiseringsmodeller i molekyldynamiksimuleringar har också jämförts. Periodiska randvillkor är mest lämpade för användning i de system som undersöks i detta arbete. Molekyldynamiksimuleringar användes för att jämföra oktapeptidområdets struktur och dynamik med och utan kopparjoner. Växelverkan mellan aminosyrornas ringar påverkar starkt strukturen i detta område i frånvaro av kopparjoner. Fyra olika icke-bindande och bindande modeller har studerats, vilka skiljer i sin beskrivning av växelverkan mellan koppar och proteinet. Teoretiska EXAFS spektra beräknades från dem simulerade strukturerna. Spektra som genererats för den bindande modellen är nästan identiska med experimentiella resultat, vilket stöder användandet av den bindande modellen. Detta arbete visar att kopparjoner interagerar med histidin imidazolringens Nδ, deprotonerade amidkväven hos de därpå följande glycinerna samt karbonylsyret hos den andra glycinen. Simuleringarna kunde visa att kopparjonen inte stabilt binder några axiella vattenmolekyler i lösning, till skillnad från en kristallstruktur av koordinationsstrukturen. Indolringen hos tryptofan interagerar direkt med kopparjonen genom stabiliserande katjon-π växelverkan utan direkt medverkan av någon vattenmolekyl. Växelverkan mellan indolringen och kopparjonen var väldefinierad och observerades kunna ske på båda sidor av koordinationsplanet. Molekyldynamiksimuleringarna med kopparjoner och oktapeptidområdet visade hur närvaron av kopparjoner ledde till ett mer strukturerat oktapeptidområde.

  • 174.
    Riihimäki, Eva-Stina
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Structure and Dynamics of the Copper-binding Octapeptide Region in the Human Prion Protein2005Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The copper-binding ability of the prion protein may be closely connected to its function. Identifying the exact function of the prion protein can clarify the underlying mechanism in prion diseases. In this work, the copper-binding octapeptide region in the human prion protein has been studied. The structural characteristics of the binding site are examined by quantum chemical structural optimization. The calculations aim at identifying a substitute for copper(II) to be used in NMR-spectroscopic studies of the copper-binding region. The dynamical and structural features of the peptide region are investigated in molecular dynamics simulations. Aspects of importance in the development of model systems in molecular dynamics simulation are addressed.

  • 175.
    Riihimäki, Eva-Stina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Computational Comparison of Cation Coordination to Human Prion Peptide Models2006Inngår i: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, nr 21, s. 8509-8516Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The coordination of the cations Cu(II), Co(II), Rh(III), Ir(III), Ni(II), Pd(II), Pt(II), and Zn(II) to the copper-binding octapeptide region in the human prion protein has been compared through structural optimization. The initial coordination mode used in the calculations is a five-coordinated mode obtained from previously published crystallographic data for Cu(II). The computational results show that, among these cations, the coordinations of Co(II) and Rh(III) are the most similar to that of Cu(II). The cations Ni(II), Pd(II), and Pt(II) prefer a four-coordinate square-planar coordination by the peptide ligand. The paramagnetic Co(II) ion with its large quadrupole moment is not a good substitute for Cu(II) to be used in NMR spectroscopic studies of the coordinated peptide region. Rh(III) has more attractive NMR spectroscopic characteristics than Cu(II) and Co(II) and may represent a suitable substitute for Cu(II) in these types of studies. Some preliminary experimental studies using NMR spectroscopic methods indicate that Rh(III) coordinates the copper-binding octapeptide region of the human prion protein, although further studies are required to determine the mode of interaction in detail.

  • 176.
    Riihimäki, Eva-Stina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Sánchez Marcos, Enrique
    Martínez, José Manuel
    Theoretical EXAFS Studies of the Cu(II)-Octapeptide ComplexManuskript (Annet vitenskapelig)
  • 177.
    Riihimäki, Eva-Stina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Manuel Martinez, Jose
    Physical Chemistry Department, University of Seville.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Structural effects of Cu(II)-coordination in the octapeptide region of the human prion protein2008Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 10, nr 18, s. 2488-2495Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The copper-binding ability of the prion protein is thought to be central to its function. The structural effects of copper coordination in the octapeptide region of the human prion protein have been investigated by molecular dynamics simulations. Simulations were performed with the apo state, in order to investigate the behavior of the region without copper ions, as well as with the octapeptide region in the presence of copper ions. While the structure of the apo state is greatly influenced by the interaction between the rings in the histidine, tryptophan and proline residues, the region shows evidence of highly ordered coordination sites in the presence of copper ions. The position of the tryptophan indole ring is stabilized by cation-pi interactions. Two stable orientations of the indole ring with respect to the equatorial coordination plane of copper were observed, which showed that the indole ring can reside on both sides of the coordination plane. The interaction with the indole ring was found to occur without a mediating axial water molecule.

  • 178.
    Riihimäki, Eva-Stina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Martinez, Jose Manuel
    Physical Chemistry Department, University of Seville.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Molecular dynamics Simulations of Cu(II) and the PHGGGWGQ octapeptide2007Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 111, nr 35, s. 10529-10537Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The interaction between Cu2+ and the copper-binding octapeptide region in the human prion protein has been investigated by molecular dynamics simulations. In total four different nonbonded and bonded models were used in the study. Charge sets containing atomic partial charges were developed for these models. Out of the considered models, the bonded model performed physically in the most correct way. The simulations with the bonded model showed that the water molecules in the axial position are very labile. The tryptophan indole ring, can remain in a stable position on top of the equatorial coordination plane of copper without water mediation. Strong aromatic interaction was observed between the imidazole and indole rings. The nonbonded models showed a tendency for water-mediated interaction between the copper ion and different carbonyl oxygen atoms. In the case of the bonded model, a carbonyl group could also interact directly with the copper ion in one of the apical position.

  • 179.
    Riihimäki, Eva-Stina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Martínez, José Manuel
    Physical Chemistry Department, University of Seville.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    An evaluation of non-periodic boundary condition models in molecular dynamics simulations using prion octapeptides as probes2006Inngår i: Journal of Molecular Structure: THEOCHEM, ISSN 0166-1280, Vol. 760, nr 1-3, s. 91-98Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular dynamics simulations have been performed under periodic boundary conditions and using four non-periodic solvation models. The biomolecular probe in these simulations was a single repeat of the copper-binding octapeptide in the human prion protein, PHGGGWGQ. Although the alternative non-periodic solvation models enable a reduction in computational time, the dynamical disadvantages are considerable when using any of these four non-periodic models. For simulations of systems similar to the test system, periodic boundary conditions are a better alternative than any of the four local models.

  • 180.
    Riihimäki, Eva-Stina
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Martínez, José Manuel
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Molecular Dynamics Simulations of the Copper-binding Octapeptide Region in the Human Prion ProteinArtikkel i tidsskrift (Fagfellevurdert)
  • 181.
    Rosdahl, Jan
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Geometric and Electronic Structure of Metal-Metal Bonded Systems2005Doktoravhandling, med artikler (Annet vitenskapelig)
  • 182.
    Rosdahl, Jan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Fässler, Thomas F.
    Kloo, Lars
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    On the Structure of Sn9(4-) Cluster in Liquid and Solid State2005Inngår i: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, nr 14, s. 2888-2894Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The nonastannide clusters have been investigated usingEXAFS, NMR and Raman spectroscopy as well as quantum chemical calculations explicitly considering a model cationic field and solid-state statistics. NMR spectroscopic andEXAFS results are basically identical to those previously published and consistent with a fluctional model of the cluster. The quantum chemical calculations show that there is no significant difference in energy between the two model geometries, C4v and D3h, and that the vibrational frequencies are very low, clearly indicating that the cluster is expected to be fluctional. The solid-state statistics show that both model geometries can be used to describe all known nonastannide structures with reasonable success, illustrating that the classification of the nonastannide clusters in terms of specific symmetries is entirely arbitrary.

  • 183.
    Rosdahl, Jan
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Gorlov, Mikhail
    KTH, Tidigare Institutioner                               , Kemi.
    Fischer, Andreas
    KTH, Tidigare Institutioner                               , Kemi.
    Kloo, Lars
    KTH, Tidigare Institutioner                               , Kemi.
    Synthesis and Crystal Structures of Di- and Trimercury Chlorogallates2004Inngår i: Zeitschrift für Anorganische und Allgemeines Chemie, ISSN 0044-2313, E-ISSN 1521-3749, Vol. 630, nr 5, s. 760-762Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Mercury(I) chloride reacts with gallium(III) chloride in benzene/1,2-dichlorobenzene solution to give the binuclear compound Hg-2(GaCl4)(2) (1). Reduction of mercury(I) chloride with mercury in gallium(III) chloride-benzene mixture leads to the trinuclear compound Hg-3(GaCl4)(2) (2). The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction {Hg-2(GaCl4)(2): triclinic, P (1) over bar, a = 645.21(3), b = 654.44(3), c = 927.17(7) pm, alpha = 83.526(2)degrees, beta = 74.915(2)degrees, gamma = 61.863(3)degrees; Hg-3(GaCl4)(2): monoclinic, P2(1)/c, a = 715.79(1), b = 1501.59(4), c = 1421.43(4) pm, beta = 98.9798(9)degrees}.

  • 184.
    Rosdahl, Jan
    et al.
    KTH, Tidigare Institutioner                               , Kemi.
    Kloo, Lars
    KTH, Tidigare Institutioner                               , Kemi.
    On the Stability of Cd2(2+) and Zn2(2+) Ions. A Theoretical StudyManuskript (Annet vitenskapelig)
  • 185.
    Roth, Olivia
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Redox Chemistry in Radiation Induced Dissolution of Spent Nuclear Fuel: from Elementary Reactions to Predictive Modeling2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The focus of this doctoral thesis is the redox chemistry involved in radiation induced oxidative dissolution of spent nuclear fuel and UO2 (as a model substance for spent nuclear fuel). It is shown that two electron oxidants are more efficient than one electron oxidants in oxidative dissolution of UO2 at low oxidant concentrations. Furthermore, it is shown that H2O2 is the only oxidant that has to be taken into account in radiation induced dissolution of UO2 under deep repository conditions (granite groundwater dominated by α-radiolysis). Previously determined rate constants for oxidation of UO2 by H2O2 and O2, and rate constants for dissolution of U(VI) from the surface are successfully used to reproduce numerous UO2 dissolution rates reported in the literature. The impact of reactive solutes (Fe(II)(aq), 2-propanol and chloride) and Pd-inclusions (as a model for ε-particles) in combination with H2, on radiation induced oxidative dissolution of UO2 is investigated. It is shown that both the studied reactive solutes (under oxygen free conditions) and the combination of Pd inclusions and H2 inhibit the dissolution. Calculations (based on the fuel inventory) show that 1 µM Fe(II)(aq) decreases the dissolution rate by a factor of ~50 and that 1 ppm surface coverage of ε-particles is sufficient to completely stop the dissolution of 100 year old fuel (assuming 40 bar H2).The dissolution behavior of NpO2 and PuO2 in H2O2 containing aqueous solution without complexing agent is studied and compared to UO2. Based on the measured dissolution rates, we would not expect the dissolution of the actinides to be congruent. Instead, in a system without complexing agent, the rates Np and Pu are expected to be lower than the U release rate. The effect of ionizing irradiation on the UO2 reactivity is studied in order to elucidate the effect of self-irradiation on the reactivity of the spent fuel matrix. It is shown that a threshold dose must be achieved before any effect of irradiation can be seen. Beyond the threshold the reactivity seems to increase with increasing dose. Furthermore, the effect appears to be permanent. The effect of particle size on the reactivity of UO2 powder is studied in view of proposed theories suggesting a particle size dependence of both the pre-exponential factor and the activation energy for redox reactions. The rate constant and activation energy for oxidation of UO2 by MnO4- seems to agree with the proposed equations. The radiation chemical synthesis of UO2 nanoparticles is studied. It is shown that U(VI) released by dissolution of spent nuclear fuel could be reduced to UO2 nanoparticles.These particles could, due to their high reactivity towards H2O2, act as oxidant scavenger in a future deep repository for spent nuclear fuel.

  • 186.
    Roth, Olivia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Bönnemark, Tobias
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    The influence of particle size on the kinetics of UO2 oxidation in aqueous powder suspensions2006Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 353, nr 1-2, s. 75-79Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Previous studies have indicated that the rate of a heterogeneous liquid-solid reaction depends on the size of the solid particles. It has been suggested that both the pre-exponential factor and the activation energy depend on the particle size. The processes involved in dissolution of UO2 have been extensively studied because of their importance for the safety analysis of a future deep repository for spent nuclear fuel and in many of these studies powder suspensions of UO2 are used as a model system. Therefore, it is of importance to investigate and quantify the particle size effect on the kinetics of UO2 oxidation in order to enable comparison of data from studies oil different solid substrates. In this work the influence of particle size on the second order rate constant and on the activation energy of the reaction between MnO4- and UO2 was studied using aqueousUO(2)-particle suspensions of four different size distributions. A comparative study of the activation energy for the reaction using a UO2 pellet was also performed.

  • 187.
    Roth, Olivia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Hasselberg, Hanna
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Radiation chemical synthesis and characterization of UO2 nanoparticles2009Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 383, nr 3, s. 231-236Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In a deep repository for spent nuclear fuel, U(VI)(aq) released upon dissolution of the fuel matrix could, in reducing parts of the system, be converted to U(IV) species which might coalesce and form nanometersized UO2 particles. This type of particles is expected to have different properties compared to bulk UO2(s). Hence, their properties, in particular the capacity for oxidant consumption, must be investigated in order to assess the effects of formation of such particles in a deep repository. In this work, methods for radiation chemical synthesis of nanometer-sized UO2 particles, by electron- and gamma-irradiation of U(VI) solutions, are presented. Electron-irradiation proved to be the most efficient method, showing high conversions of U(VI) and yielding small particles with a narrow size distribution (22-35 nm). Stable colloidal suspensions were obtained at low pH and ionic strength (pH 3, I = 0.03). Furthermore, the reactivity of the produced UO2 particles towards H2O2 is investigated. The U(IV) fraction in the produced particles was found to be similar to 20% of the total uranium content, and the results show that the UO2 nanoparticles are significantly more reactive than micrometer-sized UO2 when it comes to H2O2 consumption, the major part of the H2O2 being catalytically decomposed on the particle surface.

  • 188.
    Roth, Olivia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    On the impact of reactive solutes on radiation induced oxidative dissolution of UO22009Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 385, nr 3, s. 595-600Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The impact of 2-propanol (100 mM), NaCl (0.1 - 2 M) and Fe(II)(aq) (10 mu M) on the radiation induced oxidative dissolution of UO2 is investigated experimentally by gamma-irradiating a UO2 pellet immersed in aqueous solution containing 10 mM HCO3- together with one of the studied solutes and measure the U(VI) concentration in solution as a function of irradiation time. The solution was saturated with one of the following gases; Air, N2O, inert gas (N-2 or At) in order to vary the experimental conditions and/or avoid the influence of oxygen. The results show that, in the presence of oxygen, 2 M chloride decrease the rate of UO2 dissolution whereas the dissolution rate increases somewhat in the presence of 100 mM 2-propanol. Under oxygen-free conditions both 2 M chloride, 100 mM 2-propanol and 10 mu M Fe(II)(aq) decrease the rate of UO2 dissolution. The trends in dissolution rates were reproduced by calculations based on previously determined rate constants for UO2 oxidation and oxidant concentrations obtained from numerical simulation of radiolysis in the corresponding homogeneous systems (taking reactions between the different solutes and the products of water radiolysis as well as changes in oxygen solubility into account). However, the results indicate that we cannot fully account for the G-values in 2 M chloride solution or all reactions involving CI- in the aqueous phase. This calls for further studies of the chloride system.

  • 189.
    Roth, Olivia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Oxidation of UO2(s) in aqueous solution2008Inngår i: Central European Journal of Chemistry, ISSN 1895-1066, Vol. 6, nr 1, s. 1-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this review the kinetics and mechanism of oxidative dissolution of UO2(s), mainly under conditions of relevance for the safety assessment of a deep geological repository for spent nuclear fuel, are discussed. Rate constants for the elementary processes involved (oxidation of UO2 and dissolution of oxidized UO2) are used to calculate the rates of oxidative UO2(s) dissolution under various conditions (type of oxidant, oxidant concentration and HCO3-/CO32- concentration) for which experimental data are also available. The calculated rates are compared to the corresponding experimental values under the assumption that the experimental numbers reflect the steady-state conditions of the system. The agreement between the calculated rates and the corresponding experimental ones is very good, in particular for the higher rates. In general, the calculated rates are somewhat higher than the experimental numbers. This can be due partly to the use of initial concentrations rather than steady-state concentrations in the calculations. The kinetic data are also used to quantitatively discuss the dynamics of spent nuclear fuel dissolution under deep geological repository conditions.

  • 190.
    Roth, Olivia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Nilsson, Sara
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Radiation enhanced reactivity of UO22006Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 354, nr 1-3, s. 131-136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pure UO2 is often used as a model compound when studying reactions of importance in a future deep repository for spent nuclear fuel. The reactivity of pure UO2 is not expected to be identical to the reactivity of the UO2-matrix of spent nuclear fuel for several reasons. One reason is that the spent fuel, due to the content of radionuclides, is continuously being self-irradiated. The aim of this study is to investigate how irradiation of solid UO2 surfaces affects their reactivity towards oxidants. The effect of irradiation (gamma or electrons) on the reaction between solid UO2 and MnO4- in aqueous solutions containing carbonate has been studied. It was found that irradiation with high doses (> 40 kGy) increased the reactivity of the UO2 to about 1.3 times the reactivity of unirradiated UO2.

  • 191.
    Roth, Olivia
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Trummer, Martin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Jonsson, Mats
    KTH, Skolan för kemivetenskap (CHE), Kemi, Kärnkemi.
    Factors influencing the rate of radiation-induced dissolution of spent nuclear fuel2009Inngår i: Research on chemical intermediates (Print), ISSN 0922-6168, E-ISSN 1568-5675, Vol. 35, nr 4, s. 465-478Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Several countries plan to store spent nuclear fuel in deep geological repositories. Accurate prediction of the spent fuel dissolution rate is a key issue in the safety assessment of a future deep repository. A reliable quantitative model for radiation-induced spent fuel dissolution must be based on an accurate description of the dose distribution around the spent fuel and fundamental knowledge about the elementary processes involved. In this paper, we discuss factors influencing the rate of radiation-induced dissolution of spent nuclear fuel, focusing on solutes (H-2, HCO3 (-), Fe(II) and organic substances affecting the H2O2 concentration and factors influencing the reactivity of the fuel surface towards H2O2. Taking these factors into account, we have also simulated dissolution of spent nuclear fuel under realistic deep repository conditions.

  • 192.
    Safi, Ismael
    KTH, Skolan för kemivetenskap (CHE).
    Radiation Effects on KBS-3 Barriers: SKB’s work so far2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In the Swedish concept for final disposal of spent nuclear fuel, referred to as KBS-3, a three-layered protection system is used. The system consists of a copper canister holding the spent nuclear fuel deposited 500 meters in a repository built in groundwater saturated granitic rock. The copper canisters are placed in deposition holes, buffered and backfilled by bentonite clay. One of the challenges associated with this system is the long-term exposure of the engineered barriers i.e. the canister including the spent fuel and the cast iron insert as well as the bentonite buffer to ionizing radiation.

    The possible effects of radiation on the materials in the engineered barriers have been studied not only by the Swedish Nuclear Fuel and Waste Co (SKB), but also by academia nationally and internationally. In this work, literature studies have been carried out to investigate whether all possible/potential effects of ionizing radiation from the spent nuclear fuel on the engineered barriers have been considered by SKB. Apart from a general summary of the relevant issues in chapter one, regions within the KBS-3 design where enhanced radiation may occur have been identified and the related radiation induced processes have been summarized in chapter two. These issues include effects of water-radiolysis on the spent fuel, the cast-iron insert and other ferrous materials, the copper shell and the bentonite buffer. Three types of possible damages have been identified: the microstructural defects in the ferrous materials by direct radiation, the radiation-induced microstructural alterations of the spent fuel and the bentonite and radiation-induced oxidation i.e. dissolution of the fuel and corrosion of the ferrous metals and the copper.

    The relevant SKB documents have been identified (in chapter 3) to be the SR-Site main report, the underlying Process reports and reports of FUD-programs. Apart from these documents, other SKB technical reports and open literature are used as basis for assessing whether all the issues mentioned in chapter two of this study have been considered by SKB. 

    According to the assessment, most of the significant issues mentioned in chapter two have been mentioned and discussed in the identified SKB documents. In the main safety assessment, i.e. the SR-Site project, the significance of most of the radiation processes has been based on dose levels expected at the different regions within the KBS-3 design. Irrespective of the assessments in SR-Site though, the current understanding of the relevant issues and plans for future research efforts summarized in FUD-programs reflect the research developments. However, the recent developments in understanding of radiation-induced effects on montmorillonite and the corrosion of copper in argon atmosphere need to be given due importance in coming FUD-programs. A separate investigation of radiation effects on FSW-joints may contribute to removal of the remaining uncertainties. In addition, mechanism involved in radiation-induced fuel dissolution and copper corrosion may require more research efforts than those planned.

     

  • 193.
    Sandhi, Arifin
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    ARSENIC REMOVAL BY PHYTOFILTRATION AND SILICON TREATMENT: A POTENTIAL SOLUTION FOR LOWERING ARSENIC CONCENTRATIONS IN FOOD CROPS2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Use of arsenic-rich groundwater for crop irrigation can increase the arsenic (As) content in food crops and act as a carcinogen, compromising human health. Using aquatic plant based phytofiltration is a potential eco-technique for removing arsenic from water. The aquatic moss species Warnstorfia fluitans grows naturally in mining areas in northern Sweden, where high concentrations of arsenic occur in lakes and rivers. This species was selected as a model for field, climate chamber and greenhouse studies on factors governing arsenic removal and arsenic phytofiltration of irrigation water. The arsenic and silicon (Si) concentrations in soil, water and plant samples were measured by AAS (atomic absorption spectrophotometry), while arsenite and arsenate species were determined using AAS combined with high pressure liquid chromatography (HPLC) with an anion exchange column. The arsenic content in grains of hybrid and local aromatic rice (Oryza sativa) cultivars with differing arsenic accumulation factor (AF) values was investigated in an arsenic hotspot in Bangladesh. The results showed that arsenic AF was important in identifying arsenic-safer rice cultivars for growing in an arsenic hotspot. The study based on silicon effect on arsenic uptake in lettuce showed that arsenic accumulation in lettuce (Lactuca sativa) could be reduced by silicon addition. The aquatic moss had good phytofiltration capacity, with fast arsenic removal of up to 82% from a medium with low arsenic concentration (1 µM). Extraction analysis showed that inorganic arsenic species were firmly bound inside moss tissue. Absorption of arsenic was relatively higher than adsorption in the moss. Regarding effects of different abiotic factors, plants were stressed at low pH (pH 2.5) and arsenic removal rate was lower from the medium, while arsenic efflux occurred in arsenate-treated medium at low (12°C) and high (30°C) temperature regimes. Besides these factors, low oxygenation increased the efficiency of arsenic removal from the medium. Finally, combining W. fluitans as a phytofilter with a lettuce crop on a constructed wetland significantly reduced the arsenic content in edible parts (leaves) of lettuce. Thus W. fluitans has great potential for use as an arsenic phytofilter in temperate regions.

  • 194.
    Sandhi, Arifin
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik. Department of Ecology, Environment and Plant Sciences, Stockholm University, SE 10691 Stockholm, Sweden.
    Greger, Maria
    Department of Ecology, Environment & Plant Sciences, Stockholm University, SE-10691 Stockholm, Sweden.
    Landberg, Tommy
    Department of Ecology, Environment & Plant Sciences, Stockholm University, SE-10691 Stockholm, Sweden.
    Jacks, Gunnar
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Bhattacharya, Prosun
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Mark- och vattenteknik.
    Arsenic concentrations in local aromatic and high-yielding hybrid rice cultivars and the potential health risk: A study in an arsenic hotspot2017Inngår i: Environmental Monitoring & Assessment, ISSN 0167-6369, E-ISSN 1573-2959, Vol. 189, nr 184Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The presence of high levels of arsenic (As) in rice fields has negative effects on the health ofthose consuming rice as their subsistence food. This study determined the variation in total Asconcentration in local aromatic rice (LAR) (kalijira) and two high yielding varieties (HYVs)(BRRI dhan 32 and BRRI dhan 28) grown in paddy fields in Matlab, Bangladesh, an As hotspot with elevated As levels in groundwater. Mature rice grain samples and soil samples were collected from different paddy fields and the As concentrations in both the de-husked grains and the husks of the three rice cultivars were analysed to identify the safest of the threecultivars for human consumption. The results showed that the total As concentration washigher (0.09-0.21 mg As kg-1) in the de-husked grains of LAR than in the husks, while theopposite was found for the HYV rice. Moreover, the As concentration in soil samples was 2-to 5-fold higher for the LAR than for the HYVs, but the As accumulation factor (AF) waslower in the LAR (0.2-0.4%) than in the HYVs (0.9-1%). Thus, LAR can be considered thesafest of the three cultivars for human consumption owing to its low AF value. Furthermore,due to the low AF, growing LAR instead of HYVs in soils with slightly elevated As levelscould help improve the food safety level in the food chain.

  • 195.
    Sandin, Karin
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Calcium phosphate precipitation in blood serum model solutions2005Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 196.
    Sandin, Karin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Hegbrant, Jörgen
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi (stängd 20110630).
    Olsson, Lars -Fride
    A theoretical investigation of the supersaturation of basic calcium phosphate in serum of dialysis patients2006Inngår i: Journal of Applied Biomaterials and Biomechanics, ISSN 1722-6899, Vol. 4, nr 2, s. 80-86Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Extraosseous calcification in hemodialysis (HD) patients consists mainly of biological apatite, idealized as hydroxyapatite. Other suggested calcium phosphates are octacalcium phosphate (OCP) and brushite, both known to be hydroxyapatite precursors. Whatever the mechanisms of mineral deposition are, these mechanisms are always required to produce a supersaturated state, and that state can be calculated from the solubility product (SP) of the relevant mineral. Supersaturation in relation to serum ionized calcium [Ca2+] and total inorganic serum phosphate (Pi) under normal and hyperphosphatemic conditions has been calculated. While supersaturation with respect to hydroxyapatite and OCP always exists, and supersaturation with respect to Ca5(PO4)3(HCO3)·4H2O is just above the limit, supersaturation with respect to brushite solely occurs under hyperphosphatemic conditions. In order to avoid supersaturation with respect to brushite the maximum serum phosphate level allowed is 1.9 mmol/L (5.8 mg/dl) and the calcium-phosphate product (Ca x— P) 4.5 (mmol/L)2 (56 (mg/dl))2.

  • 197.
    Sandin, Karin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Nevsten, Pernilla
    Wallenberg, Reine L.
    Olsson, Lars-Fride
    Formation of carbonated apatite particles from a supersaturated inorganic blood serum model2009Inngår i: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 20, nr 8, s. 1677-1687Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Pathological calcification is common among for instance dialysis patients, and this causes an increase in mortality risk. An elevated serum phosphate concentration among those patients strongly correlates to this increase. In this work investigations of the conditions, composition, crystallinity and morphology of in vitro calcification are performed and related to results from in vivo studies. The study was performed under conditions mimicking physiological ones, i.e. a pH around 7.40, a temperature of 37A degrees C, an ionic strength of 150 mM and ion concentrations close to those in human serum including the effects of elevated phosphate concentrations. The course of precipitation involves an initial precipitate that subsequently re-dissolves to give another precipitate, in accordance with the well-known Ostwald ripening theory. The final bulk precipitate consists of a macroscopically amorphous carbonated apatite. The amorphous apatite is formed from assemblies of spherical particles in the mu m range, in turn composed of nano-crystalline needles of about 10 x 100 nm. Even the initially formed precipitate, as well as a small amount of precipitate that occurs on the liquid surface, consist of a carbonated calcium phosphate. The in vitro observed carbonated apatite bears strong resemblance to in vivo cardiovascular calcification known from literature.

  • 198.
    Sandin, Karin
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Kloo, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Oorganisk kemi.
    Odselius, Rolf
    Olsson, Lars-Fride
    The observation of nano-crystalline calcium phosphate precipitate in a simple supersaturated inorganic blood serum model - composition and morphology2009Inngår i: Journal of Applied Biomaterials and Biomechanics, ISSN 1722-6899, Vol. 7, nr 1, s. 13-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aim. Calcium phosphate deposition in blood vessels is correlated to increased mortality risk. In this study, the formation of solid calcium phosphate in an in vitro solution mimicking the inorganic part of blood serum was studied. Methods. The precipitates formed were analyzed using several experimental techniques, including infrared spectroscopy, Raman spectroscopy, X-ray energy dispersive spectroscopy, chemical analysis of combustion gases, thermogravimetric analysis, as well as transmission electron microscopy and scanning electron microscopy. Results. The results indicate a microscopically amorphous but nano-crystalline material with an overall apatite structure. A plausible stoichiometry was determined to Ca-5(PO4)(3)(HCO3)center dot 4H(2)O with an estimated solubility constant of 6.10(-39) (mol/L)(9). Bicarbonate in the water solution was shown to be essential for the precipitation, giving implications for in vitro studies. Conclusions. The calcium phosphate formed in this study shows many similarities to pathological calcium phosphates regarding composition, morphology and crystallinity.

  • 199. Shukla, V.
    et al.
    Araujo, R. B.
    Jena, N. K.
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Borophene's tryst with stability: Exploring 2D hydrogen boride as an electrode for rechargeable batteries2018Inngår i: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, nr 34, s. 22008-22016Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Graphene's emergence can be viewed as a positive upheaval in 2D materials research. Along the same line, the realization of a related elemental 2D material, borophene, is another breakthrough. To circumvent the stability issues of borophene, which is reported to have been synthesized on metallic substrates under extreme conditions, hydrogenation of borophene (otherwise called as borophane or hydrogen boride or boron hydride) has been a plausible solution, but only proposed computationally. A recent report (H. Nishino, T. Fujita, N. T. Cuong, S. Tominaka, M. Miyauchi, S. Iimura, A. Hirata, N. Umezawa, S. Okada, E. Nishibori, A. Fujino, T. Fujimori, S. Ito, J. Nakamura, H. Hosono and T. Kondo, J. Am. Chem. Soc., 2017, 139(39), 13761-13769) brings to fore its experimental realization. Our current study delves into the possibilities of employing this intriguing 2D hydrogen boride as anodes in Li/Na ion batteries. Using first-principles density functional theory methods, we computed relevant properties such as the ion (Li/Na) adsorption behavior, the possible pathways of ionic diffusion with the estimation of barriers as well as the theoretical specific capacities and average voltages to uniquely demonstrate that this material is of particular significance for battery applications. It is noted that the use of hydrogen boride leads to a high specific capacity of 861.78 mA h g-1 for Li ions, which is remarkably higher than the value reported in relation to its computationally predicted structure. Furthermore, Na ion intercalation leads to negative voltage profiles, implying the unsuitability of 2D hydrogen boride for this particular ion. Our findings are timely and pertinent towards adding insightful details relevant to the progress of applications of 2D materials for energy storage.

  • 200. Shukla, V.
    et al.
    Araujo, R. B.
    Jena, N. K.
    Ahuja, Rajeev
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    The curious case of two dimensional Si2BN: A high-capacity battery anode material2017Inngår i: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 41, s. 251-260Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The ubiquity of silicon in the semiconductor industry and its unique charge transport features has consistently fueled interest in this element and recent realization 2D silicene is a new feather in its cap. In what could be considered as opening up the Pandora's box with many possible virtues, buckled silicene, planar graphene and a host of other newly discovered 2D materials have redefined a whole new paradigm of research. To this end, the quest for new 2D materials and finding potential applications, particularly to the realm of energy storage, is a curiosity driven task. From first principle density functional theory studies, a newly reported graphene like 2D material Si2BN is investigated as a probable anode material for Li and Na ion batteries. In contrast to pristine silicene, which is inherently buckled, the material Si2BN is planar. However, an interesting transition from planar to buckled structure takes place upon subsequent adsorption of Li and Na ions. Concomitantly, this transition is associated with superior specific capacity (1158.5 and 993.0 mA h/g respectively for Li and Na) which is significantly higher than several other 2D analogues. Furthermore, the substrate Si2BN regains the planar structure on subsequent desorption of ions and stability of the material remains intact, as evidenced from ab initio molecular dynamics simulations. As we delve deep into the electronic structure and compute the diffusion pathways and barriers, it is observed that the ionic diffusion is very fast with significantly lesser barrier heights, particularly for Na-ion. These findings suggest that for the 2D Si2BN, there is no diminution in order to be a potential anode material for Li and Na ion batteries.

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