| 1. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Effect of co-doping on proton conductivity in perovskite oxides BaZr0.9In0.05M0.05O3−δ (M = Yb3+ or Ga3+)
- 2010
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Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 35:12, s. 6381-6391
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Tidskriftsartikel (refereegranskat)abstract
- BaZr0.9In0.05M0.05O3-d (M ¼ Ga3+ or Yb3+) has been prepared by solid-statesynthesis route.Rietveld analysis of neutron powder diffraction data on as-prepared samples showed thatboth samples crystallise in the cubic space group Pm-3m. Scanning electron microscopyanalysis showed that the grains intheBaZr0.9In0.05Ga0.05O3-d sample were larger than the BaZr0.9In0.05Yb0.05O3-d sample. Dynamic thermogravimetric analysis indicates that the proton concentration was higher inpre-hydrated BaZr0.9In0.05Ga0.05O3-d sample (40%oftheoretical)than that of BaZr0.9In0.05Yb0.05O3-d sample (28%oftheoretical).Proton conductivity was studied on pre-hydrated samples(under both dry and wetAr atmospheres).Thebulk proton conductivities of the heating cycle of pre-hydrated BaZr0.9In0.05M0.05O3-d (M ¼ Ga3+ or Yb3+) samples were 2.1 * 10-5 S cm-1 and 1.9 * 10-4 Scm-1 at 350C, respectively.The effect of co-doping onproton conductivity was investigatedand the results are compared with single doped systems e.g. BaZr0.9M0.1O3-d (M=Ga3+, In3+ orYb3+) samples.
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| 2. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Proton Conductivity in Mixed B-Site Doped Perovskite Oxide BaZr[sub 0.5]In[sub 0.25]Yb[sub 0.25]O[sub 3 - delta]
- 2010
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Ingår i: Journal of The Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 157:12
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Tidskriftsartikel (refereegranskat)abstract
- A wet chemical route was used to prepare the oxygen deficient codoped perovskite oxide BaZr0.5In0.25Yb0.25O3−. Analysis of X-ray powder diffraction data showed that the sample belongs to the cubic crystal system with space group Pmm. Dynamic thermogravimetric (TG) analysis confirmed complete filling of oxygen vacancies (V) by protonic defects (OH) during the hydration process. The proton conductivity was investigated by impedance spectroscopy. The bulk and total conductivities of prehydrated BaZr0.5In0.25Yb0.25O3− were found to be 8.5×10−4 and 2.2×10−5 S cm−1, respectively, at 300°C. The total conductivity in the codoped perovskite oxide was higher compared to that of the respective single doped perovskite oxides with the same doping level. The bulk and grain-boundary mobility and diffusion coefficients of protons were calculated at 200°C using impedance and TG data to obtain the conductivity and proton concentration, respectively. The high bulk diffusivity (2.3×10−7 cm2 s−1) was obtained which indicates that the protons are more free to move in the heavily doped matrix compared to the lightly doped systems where trapping of protons occurs.
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| 3. |
- Björling, Alexander, 1983, et al.
(författare)
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Kinetics of surface modification induced by submonolayer electrochemical oxygen adsorption on Pt(1 1 1)
- 2010
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Ingår i: Electrochemistry Communications. - : Elsevier BV. - 1388-2481. ; 12:3, s. 359-361
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical oxygen adsorption/desorption below monolayer level leads to a disordering of platinum single-crystal surfaces vicinal to the (1 1 1) plane. The kinetics can be described by means of a consecutive reaction from (1 1 1)-terrace sites to (1 1 0)-defect sites, in which (1 0 0)-defects act as intermediates. The first oxidation of the electrode reflects independent contributions from terrace and step sites, the latter being structure sensitive. Oxygen adsorption charges amount to a mean value of one electron per step site.
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| 4. |
- Eurenius, Karinh, 1980, et al.
(författare)
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Investigation of proton conductivity in Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ pyrochlores
- 2010
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 181:3-4, s. 148-153
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Tidskriftsartikel (refereegranskat)abstract
- The results of the synthesis and characterisation of pyrochlore systems Sm1.92Ca0.08Ti2O7 − δ and Sm2Ti1.92Y0.08O7 − δ are reported. The electrical conductivity of the materials was studied using impedance spectroscopy under wet and dry oxygen and argon. Enhancements of the bulk conductivity at temperatures up to 500 °C were observed for wet conditions indicative of significant proton conductivity. The presence of dissolved protons in the materials is supported by thermogravimetric analysis and infrared spectroscopy. Proton conduction was confirmed by measurements in O2/D2O and Ar/D2O. The results reveal the importance of the correct choice of dopant site for the pyrochlore structure, with A-site substitution yielding the highest levels of proton, as well as oxide ion, conduction. For both samples bulk, rather than grain boundary, conduction is found to be dominant.
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| 5. |
- Eurenius, Karinh, 1980, et al.
(författare)
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Proton conductivity in Ln1.96Ca0.04Sn2O7-δ (Ln = La, Sm, Yb) pyrochlores as a function of the lanthanide size
- 2010
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 181:27-28, s. 1258-1263
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Tidskriftsartikel (refereegranskat)abstract
- The proton conductivity in tin-based pyrochlores, Ln1.96Ca0.04Sn2O7-δ (Ln = La, Sm, Yb), has been investigated. Samples were prepared by conventional solid state sintering methods. Fractions of the powders were vacuum dried, protonated and deuterated so that infrared spectroscopy and thermogravimetric analysis could be carried out to study proton incorporation. Electrochemical impedance spectroscopy was used to characterise the conductivities of the sample. The bulk conductivity was higher in wet gas compared to the dry runs at temperatures below approximately 500 °C for all samples. The level of proton conductivity was found to depend critically on the lanthanide size, and was highest for the largest La and mid-sized Sm ions, σH+ ≈ 4 × 10−7 Scm−1 at 300 °C, before falling sharply for the Yb-ion, σH+ ≈ 7 × 10−9 Scm−1. Evidence from TGA and IR analyses indicates that the tendency for proton absorption was strongly influenced by the lanthanide size, being greatest for La1.96Ca0.04Sn2O7-δ. The results suggest that both proton concentration and proton mobility vary depending on the size of the A-site ion.
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| 6. |
- Eurenius, Karinh, 1980, et al.
(författare)
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Proton conductivity in Sm2Sn2O7 pyrochlores
- 2010
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738. ; 181:35-36, s. 1577-1585
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Tidskriftsartikel (refereegranskat)abstract
- The electrical conductivity of the pyrochlore systems, Sm2Sn2O7, Sm1.92Ca0.08Sn2O7 − δ and Sm2Sn1.92Y0.08O7 − δ was studied using impedance spectroscopy under wet and dry gas (O2 and Ar) in the temperature range 150–1000 °C. Enhancements of the bulk conductivity of all samples at temperatures up to ~ 550 °C were observed for wet conditions consistent with significant levels of proton conduction. The presence of dissolved protons in the acceptor-doped materials, Sm1.92Ca0.08Sn2O7 − δ and Sm2Sn1.92Y0.08O7 − δ, is supported by infrared spectroscopy and thermogravimetric analysis. Proton conduction was confirmed by isotope effects under heavy water (O2/D2O and Ar/D2O). The A-site substituted sample Sm1.92Ca0.08Sn2O7 − δ yielded the highest levels of proton conduction and displayed mixed ionic and electronic conduction under dry oxidising conditions. Electron hole conduction dominates in dry oxygen for Sm2Sn1.92Y0.08O7 − δ and Sm2Sn2O7. For the A-site doped sample bulk and grain boundary conduction could be separated. The specific grain boundary conduction was calculated using the brick layer model and was found to be two orders of magnitude lower compared to the bulk conductivity. The unexpected increase in conductivity seen for the undoped sample under wet gas is discussed in the context of structural disorder and possible filling of the un-occupied anion site in the pyrochlore structure by OH-groups.
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| 7. |
- Hansson, Stig, et al.
(författare)
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Characterisation of Titanium Dental Implants. II: Local Biomechanical Model
- 2010
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Ingår i: The Open Biomaterials Journal. - : Bentham Science Publishers Ltd.. - 1876-5025. ; 2, s. 36-52
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model for estimation of the bone-to-implant interfacial shear strength induced by implant surface roughness has been developed. Two different assumptions regarding the constitutive behaviour of the interfacial bone were made. 1) The bone exhibits an ideally plastic deformation – the plastic mode. 2) The bone exhibits a linearly elastic deformation – the elastic mode. In the plastic mode it was found that the estimated interfacial shear strength was directly proportional to the 2D surface roughness parameter mean slope. For the elastic mode a new 2D surface roughness parameter was defined. With this parameter a direct proportionality between parameter value and estimated interfacial shear strength was also obtained in the elastic mode. The model was extended into 3D mode. The model was used to evaluate topographies of implant surfaces. The calculated results showed a similar trend to interfacial shear strength results reported in vivo.
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| 8. |
- Löberg, Johanna, 1981, et al.
(författare)
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Characterisation of titanium dental implants I:critical assessment of surface roughness parameters
- 2010
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Ingår i: The Open Biomaterials Journal. - : Bentham Science Publishers Ltd.. - 1876-5025. ; 2, s. 18-35
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Tidskriftsartikel (refereegranskat)abstract
- Titanium is commonly used for dental implants because of its unique ability to get incorporated into living bone. There is an ongoing development to obtain better anchorage and surface properties such as roughness and chemical composition are modified to reach this. In this study titanium dental implant surfaces were characterised by recording the topographical changes induced by each individual processing step such as cleaning, blasting, and HF etching. To fully describe the different surfaces, the same point was analysed before and after each step using Atomic Force Microscopy (AFM) and 3D-Scanning Electron Microscopy (3D-SEM). A set of 3D surface parameters were calculated as a function of filter size to describe the topographic features at different levels. The chemical treatment introduces nano-sized features while blasting changes the topography at the micrometer level and by combining AFM and 3D-SEM the entire range can be assessed. The results show that the chemically induced changes in the topography can only be revealed by AFM while 3D-SEM gives a clear description of the topography of blasted surfaces. The fractal dimension for the chemically treated surface was the same as for the blasted surfaces but crossover size was much smaller. Besides the commonly used Sa parameter it is suggested that the root-mean-square of the surface slope (Sdq) and the void volume (Vvc) parameters are included in the characterisation of rough surfaces. These parameters can be used for correlation with in vivo performance.
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| 9. |
- Ma, Yi, 1982, et al.
(författare)
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A mechanistic study of electrodeposition of bismuth telluride on stainless steel substrates
- 2010
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 55:15, s. 4610-4617
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Tidskriftsartikel (refereegranskat)abstract
- Miniaturization of Bi2Te3 compounds is of great interest in semiconductor industries due to their distinct anisotropic thermoelectric properties at room temperature. The aim of the present work was to investigate the mechanism of the electrodeposition of Bi2Te3 compounds on stainless steel substrates and relate the morphology and composition of the resulting deposits to experimental parameters. Cyclic voltammetry (CV) experiments in acidic solutions containing Bi3+ and/or HTeO2+ ions show that the deposition potential for the Bi2Te3 compound is more positive than either of the single elements alone. A detailed mechanism of the co-deposition was obtained by varying the concentrations of the two elements and evaluating the corresponding morphological and compositional changes of the deposits. The results show that the deposition of Te is kinetically hindered and that Bi deposition plays a major role during the co-deposition.
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