NORECS / Videos / ProboStat TEG module Search FAQ Order and Enquiry Contact Language
ProboStat webinar: 4 leg TEG module

The new 4-leg TEG setup for ProboStat allows testing up to 1000°C (hot side) and gradients up to 600°C by using a water-flushed stainless steel support tube. Great for developments of oxide thermoelectrics and recording the stability of materials, interconnects, and interfaces. Controlled atmosphere makes it interesting also for non-oxide thermoelectrics at more modest temperatures.

These articles refer to ProboStat or other NORECS products, filtered with keywords: 'TEG, TEG module'  
ID=603

From insulator to oxide-ion conductor by a synergistic effect from defect chemistry and microstructure: acceptor-doped Bi-excess sodium bismuth titanate Na0.5Bi0.51TiO3.015

Authors Fan Yang, Julian S. Dean, Qiaodan Hu, Patrick Wu, Emilio Pradal-Velázquez, Linhao Li and Derek C. Sinclair
Source
Journal of Materials Chemistry A
Issue: 47 Time of Publication: 2020
Abstract The influence of Ti-site acceptor-doping (Mg2+, Zn2+, Sc3+, Ga3+ and Al3+) on the electrical conductivity and conduction mechanism of a nominally Bi-excess sodium bismuth titanate perovskite, Na0.5Bi0.51TiO3.015 (NB0.51T), is reported. Low levels of acceptor-type dopants can introduce appreciable levels of oxide-ion conductivity into NB0.51T, i.e., 0.5% Mg-doping for Ti4+ can enhance the bulk conductivity of NB0.51T by more than 3 orders of magnitude with the oxide-ion transport number going from <0.1 for NB0.51T to >0.9 at 600 °C. The intriguing electrical behaviour in acceptor-doped NB0.51T dielectrics is a synergistic effect based on the defect chemistry and ceramic microstructure in these materials. NB0.51T ceramics with extremely low levels of doping show an inhomogeneous microstructure with randomly distributed large grains embedded in a small grained matrix. This can be considered as a two-phase composite with large grains as a conductive phase and small grains as an insulating phase based on an empirical conductivity – grain size relationship. Variation in the fraction of the conductive, large grained phase with increasing doping levels agrees with the oxide-ion transport number. This electrical two-phase model is supported by finite element modelling. This study reveals the significance of ceramic microstructure on the electrical conduction behaviour of these materials and can provide a guideline for selecting suitable doping strategies to meet the electrical property requirements of NBT-based ceramics for different applications.
Remark Link
ID=596

Strategies to Mitigate the Degradation of Stainless-SteelInterconnects Used in Solid Oxide Fuel Cells

Author Claudia Gоbel
Source
Time of Publication: 2020
Abstract Interconnects are a vital part of solid oxide fuel cells (SOFC), where they electricallyconnect individual cells to form a fuel cell stack. They are a main contributor to theoverall stack cost and the limited life-time of fuel cells, and, therefore, improvementscarried out on the interconnect level could further the commercialization of SOFCs.The limited life-time of the interconnect is related to the material used today, ferriticstainless steels (FSS). FSS interconnects are more cost-effective than previously usedceramics, but they degrade under the conditions prevalent in an SOFC: high temperaturesbetween 600°C and 850°C, and a p(O2) gradient. Certain corrosion phenomena thatoccur, such as Cr evaporation and continuous oxide scale growth, negatively impact cellperformance due to cathode poisoning and increased electrical resistance, respectively.These phenomena have been found to be effectively mitigated by coatings, such as the(Co,Mn)3O4(MCO) coating, or reactive element coatings, such as Ce.The present thesis examines these coatings with regard to three aspects: (i) doesthe semi-conducting spinel coating affect the electrical resistance of the interconnectnegatively, or is its conductivity negligible in comparison to the continuously growingCr2O3scale below it; (ii) does the coating self-heal if it is cracked even at intermediatetemperatures, i.e. 650°C and 750°C, or do the cracks persist and increase Cr evaporation;and (iii) is the long-term stability of the state-of-the-art Ce/Co coating (10 nm Ce/640 nmCo) still effective after 35 000 h, or not. The second aspect is not only important tounderstand corrosion behavior, but it would also allow for large-scale roll-to-roll PVDcoating, which is significantly more cost-effective than batch coating.Another corrosion phenomenon that is elucidated within the scope of this work is thedual atmosphere effect. This effect leads to increased corrosion on the air-facing side ofthe interconnect if the FSS is exposed to a dual atmosphere, i.e. air on one side andhydrogen on the other side, compared to if the FSS is exposed to an air-only atmosphere.A new theory as to why the dual atmosphere effect occurs is proposed, and it is indirectlyverified by means of excluding all other possibilities. Factors that influence the dualatmosphere effect are discussed, and it is shown how the dual atmosphere effect could, inpart, be mitigated.
Keywords Solid Oxide Fuel Cell; Corrosion; Interconnect; Cr Evaporation; Area SpecificResistance; Deformation; Long-term; Dual Atmosphere; Hydrogen
Remark THESIS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
Link
ID=530

Surface Reconstruction under the Exposure of Electric Fields Enhances the Reactivity of Donor-Doped SrTiO3

Authors Bu&#287;ra Kayaalp, Kurt Klauke, Mattia Biesuz, Alessandro Iannaci, Vincenzo M. Sglavo, Massimiliano D&#8217;Arienzo, Heshmat Noei, Siwon Lee, WooChul Jung, Simone Mascotto
Source
J. Phys. Chem. C
Volume: 123, Issue: 27, Pages: 16883-16892
Time of Publication: 2019
Abstract In the present work, we show how exposure to electric fields during a high-temperature treatment can be used to manipulate surface properties of donor-doped ceramics and thus improve their reactivity. La0.1Sr0.9TiO3 (LSTO) nanoparticles, prepared by hydrothermal synthesis, were consolidated under air with and without external electric fields. Although neither approaches caused grain growth upon consolidation, the treatment under the influence of the electric field (i.e., flash sintering) remarkably enhanced the segregation of Sr on the material’s surface. In addition, a high concentration of O– defects both in bulk as well as on the material surface was demonstrated by spectroscopic methods. This enhanced defect concentration along with the nanoscopic grain size of the field-consolidated materials is probably one of the triggering factors of their improved charge carrier mobility, as observed by impedance spectroscopy. The effect of such a perturbed defect structure on the reactivity of the materials was evaluated by the total oxidation of methane. For materials treated under the influence of electric fields, the catalytic reaction rate improved by a factor of 3 with respect to that of conventionally treated LSTO, along with a remarkable decrease of the activation energy. Thus, electric-field-assisted processes, usually known for their energy-saving character, can also be deemed as an attractive, forward-looking strategy for improving functional properties of ceramics.
Remark Link
ID=513

Template-free mesoporous La0.3Sr0.7Ti1-xFexO3±δ for CH4 and CO oxidation catalysis

Authors Bu&#287;ra Kayaalp, Siwon Lee, Kurt Klauke, Jongsu Seo, Luca Nodaric, Andreas Kornowski, WooChul Jung, Simone Mascotto
Source
Applied catalysis B: Enviromental
Volume: 245, Pages: 536-545
Time of Publication: 2019
Abstract The design of perovskite oxides with improved textural properties in combination with tunable composition variations is a forward-looking strategy for the preparation of next generation catalytic converter. In the present work we report the template-free synthesis of mesoporous solid solutions of La0.3Sr0.7Ti1-xFexO3±δ (0 ≤ x ≤ 0.5) and the study of their catalytic performance towards CH4 and CO oxidation. Using an innovative polymer complex route, phase pure perovskite solid solutions with specific surface area of 65 m2 g−1 and average pore size of 15 nm were prepared. The iron concentration increase led to a progressive enhancement of not only both concentration and transport of the charge carriers but also reducibility and oxygen desorption capability on the catalyst. As a result, we observed almost complete conversion of CH4 and CO at 600 °C and 300 °C, respectively. Kinetic studies on methane oxidation showed that competing suprafacial and intrafacial reaction mechanisms coexist, and that the concentration of 30% of Fe maximizes the suprafacial contribution. Under reducing conditions at 600 °C the materials retained their structural and morphological integrity, showing superior stability. Finally, the reaction rate of CH4 and CO conversion evidenced that our systems are by a maximum of 90 times more performing than other bulk and nanoporous Fe-based perovskites in literature (e.g. La0.66Sr0.34Co0.2Fe0.8O3-δ), as a result their large surface area, intimate gas-solid contact and short intragrain oxygen diffusion pathways induced by the mesoporous structure.
Remark Link
ID=508

Improved CO2 flux by dissolution of oxide ions into the molten carbonate phase of dual-phase CO2 separation membranes

Authors Wen Xing, Zuoan Li, Thijs Peters, Marie-Laure Fontaine, Michael McCann, Anna Evans, Truls Norby, Rune Bredesen
Source
Separation and Purification Technology
Volume: 212, Pages: 723-727
Time of Publication: 2019
Abstract In a solid-liquid dual-phase CO2 separation membrane, the native ions in the molten alkali carbonate, including carbonate anions and metal cations can transport CO2 in a process that is charge-compensated by electronic species (electrons or holes), oxide ions, or hydroxide ions, depending on materials and conditions. This strongly affects the design of experiments for assessing the performance of these membranes, and further determines the routes for integration of these membranes in industrial applications. Here we report how dissolved oxides in the liquid carbonate improve the CO2 flux of the membrane due to an enhanced charge-compensating oxygen ion transport. A qualitative understanding of the magnitude and role of oxide ion conductivity in the molten phase and in the solid support as a function of the temperature is provided. Employing a solid matrix of ceria, and dissolving CsVO3 and MoO3 oxides in the molten carbonate phase led to an almost doubled CO2 flux at 550 °C under dry ambient conditions. When the sweep gas contained 2.5% H2O, the CO2 flux was increased further due to formation of hydroxide ions in the molten carbonate acting as charge compensating species. Also, as a consequence of permeation controlled by ions in the liquid phase, the CO2 flux increased with the pore volume of the solid matrix.
Remark Link
ID=458

Solid oxide fuel cells with apatite-type lanthanum silicate-based electrolyte films deposited by radio frequency magnetron sputtering

Authors Yi-Xin Liu, Sea-Fue Wang, Yung-Fu Hsu, Chi-Hua Wang
Source
Journal of Power Sources
Volume: 381, Pages: 101-106
Time of Publication: 2018
Abstract In this study, solid oxide fuel cells (SOFCs) containing high-quality apatite-type magnesium doped lanthanum silicate-based electrolyte films (LSMO) deposited by RF magnetron sputtering are successfully fabricated. The LSMO film deposited at an Ar:O2 ratio of 6:4 on an anode supported NiO/Sm0.2Ce0·8O2-δ (SDC) substrate followed by post-annealing at 1000 °C reveals a uniform and dense c-axis oriented polycrystalline structure, which is well adhered to the anode substrate. A composite SDC/La0·6Sr0·4Co0·2Fe0·8O3-δ cathode layer is subsequently screen-printed on the LSMO deposited anode substrate and fired. The SOFC fabricated with the LSMO film exhibits good mechanical integrity. The single cell with the LSMO layer of ≈2.8 μm thickness reports a total cell resistance of 1.156 and 0.163 Ωcm2, open circuit voltage of 1.051 and 0.982 V, and maximum power densities of 0.212 and 1.490 Wcm−2 at measurement temperatures of 700 and 850 °C, respectively, which are comparable or superior to those of previously reported SOFCs with yttria stabilized zirconia electrolyte films. The results of the present study demonstrate the feasibility of deposition of high-quality LSMO films by RF magnetron sputtering on NiO-SDC anode substrates for the fabrication of SOFCs with good cell performance.
Keywords Solid oxide fuel cell, Sputtering, Electrolyte Doped lanthanum silicate
Remark https://doi.org/10.1016/j.jpowsour.2018.02.007
Link
ID=352

Direct conversion of methane to aromatics in a catalytic co-ionic membrane reactor

Authors
Source
Science
Volume: 353, Issue: 6299, Pages: 563-566
Publisher: American Association for the Advancement of Science (AAAS), ISBN: Print ISSN:0036-8075 Online ISSN:1095-9203, Time of Publication: 2016-08
Abstract Nonoxidative methane dehydroaromatization (MDA: 6CH4 ↔ C6H6 + 9H2) using shape-selective Mo/zeolite catalysts is a key technology for exploitation of stranded natural gas reserves by direct conversion into transportable liquids. However, this reaction faces two major issues: The one-pass conversion is limited by thermodynamics, and the catalyst deactivates quickly through kinetically favored formation of coke. We show that integration of an electrochemical BaZrO3-based membrane exhibiting both proton and oxide ion conductivity into an MDA reactor gives rise to high aromatic yields and improved catalyst stability. These effects originate from the simultaneous extraction of hydrogen and distributed injection of oxide ions along the reactor length. Further, we demonstrate that the electrochemical co-ionic membrane reactor enables high carbon efficiencies (up to 80%) that improve the technoeconomic process viability. Methane gas is expensive to ship. It is usually converted into carbon monoxide and hydrogen and then liquefied. This is economically feasible only on very large scales. Hence, methane produced in small amounts at remote locations is either burned or not extracted. A promising alternative is conversion to benzene and hydrogen with molybdenumzeolite catalysts. Unfortunately, these catalysts deactivate because of carbon buildup; plus, hydrogen has to be removed to drive the reaction forward. Morejudo et al. address both of these problems with a solid-state BaZrO3 membrane reactor that electrochemically removes hydrogen and supplies oxygen to suppress carbon buildup.
Keywords CMR, MDA, catalytic membrane reactor, ZSM-5, MCM-22, FBR, FBR-PolyM, Pd-CMR, Co-ionic CMR, FT, ProboStat CMR base unit (NORECS)
Remark http://science.sciencemag.org/highwire/filestream/682540/field_highwire_adjunct_files/0/Morejudo.SM.pdf
BaZrO3
BaZrO3
Link
ID=319

Tetragonal tungsten bronzes Nb8−xW9+xO47−δ: optimization strategies and transport properties of a new n-type thermoelectric oxide

Authors Christophe P. Heinrich, Matthias Schrade, Giacomo Cerretti, Ingo Lieberwirth, Patrick Leidich, Andreas Schmitz, Harald Fjeld, Eckhard Mueller, Terje G. Finstad, Truls Norby and Wolfgang Tremel
Source
Materials Horizons
Issue: 5, Pages: 519-527
Time of Publication: 2015
Abstract Engineering of nanoscaled structures may help controlling the electrical and thermal transport in solids, in particular for thermoelectric applications that require the combination of low thermal conductivity and low electrical resistivity. The tetragonal tungsten bronzes Nb8−xW9+xO47 (TTB) allow a continuous variation of the charge carrier concentration while fulfilling at the same time the concept of a “phonon-glass electron-crystal” through a layered nanostructure defined by intrinsic crystallographic shear planes. The thermoelectric properties of the tetragonal tungsten bronzes Nb8−xW9+xO47−δ (0 < x < 2) were studied in the temperature range from 373 to 973 K. Structural defects and the thermal stability under various oxygen partial pressure pO2 were investigated by means of thermogravimetry, HR-TEM, and XRD. Nb8W9O47−δ was found stable at 973 K and a pO2 of ≈10−15 atm. The oxygen nonstoichiometry δ can reach up to 0.3, depending on the applied atmosphere. By increasing the substitution level x, the electrical resistivity ρ and the Seebeck coefficient S decreased. For x = 2, ρ reached 20 mΩ cm at 973 K, combined with a Seebeck coefficient of approximately −120 μV K−1. The thermal conductivity was low for all samples, ranging from 1.6 to 2.0 W K−1 m−1, attributed to the complex crystal structure. The best thermoelectric figure of merit zT of the investigated samples was 0.043, obtained for x = 2 at 973 K, but it is expected to increase significantly upon a further increase of x. The control of the oxygen non-stoichiometry δ opens a second independent optimization strategy for tetragonal tungsten bronzes.
Remark DOI: 10.1039/C5MH00033E
Link
ID=304

FD Electrolysis: Co-electrolysis of steam and CO2 in full-ceramic symmetrical SOECs: A strategy for avoiding the use of Hydrogen as a safe gas

Authors
Source
Faraday Discussions
Time of Publication: 2015
Abstract The use of cermets as fuel electrodes for solid oxide electrolysis cells requires permanent circulation of reducing gas, e.g. H2 or CO, so called safe gas, in order to avoid oxidation of the metallic phase. Replacing metallic based electrodes by pure oxides is therefore proposed as an advantage for the industrial application of solid oxide electrolyzers. In this work, full-ceramic symmetrical solid oxide electrolysis cells have been investigated for steam/CO2 co-electrolysis. Electrolyte supported cells with La0.75Sr0.25Cr0.5Mn0.5O3-δ reversible electrodes have been fabricated and tested in co-electrolysis mode using different fuel compositions, from pure H2O to pure CO2, at temperatures of 850°C – 900°C. Electrochemical impedance spectroscopy and galvanostatic measurements have been carried out for the mechanistic understanding of the symmetrical cells performance. The content of H2 and CO in the product gas has been measured by in-line gas micro-chromatography. The effect of employing H2 as a safe gas has been also investigated. Maximum density currents of 750 mA/cm2 and 620 mA/cm2 have been applied at 1.7 V for pure H2O and for H2O:CO2 ratios of 1:1, respectively. Remarkable results were obtained for hydrogen-free fuel compositions, which confirmed the interest of using ceramic oxides as a fuel electrode candidate to reduce or completely avoid the use of safe gas in operation minimizing the contribution of the reverse water shift reaction (RWSR) in the process. H2:CO ratios close to two were obtained for hydrogen-free tests fulfilling the basic requirements for synthetic fuel production. An important increase of the operation voltage was detected under continuous operation leading to a dramatic failure by delamination of the oxygen electrode.
Remark Accepted Manuscript, DOI: 10.1039/C5FD00018A
Link
ID=303

Doping strategies for increased oxygen permeability of CaTiO3 based membranes

Authors Jonathan M. Polfus, Wen Xing, Martin F. Sunding, Sidsel M. Hanetho, Paul Inge Dahl, Yngve Larring, Marie-Laure Fontaine, Rune Bredesen
Source
Journal of Membrane Science
Volume: 482, Pages: 137–143
Time of Publication: 2015
Abstract Oxygen permeation measurements are performed on dense samples of CaTi0.85Fe0.15O3−δ, CaTi0.75Fe0.15Mg0.05O3−δ and CaTi0.75Fe0.15Mn0.10O3−δ in combination with density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) in order to assess Mg and Mn as dopants for improving the O2 permeability of CaTi1−xFexO3−δ based oxygen separation membranes. The oxygen permeation measurements were carried out at temperatures ranging between 700 and 1000 °C with feed side oxygen partial pressures between 0.01 and 1 bar. The O2 permeability was experimentally found to be highest for the Mn doped sample over the whole temperature range, reaching 4.2×10−3 ml min−1 cm−1 at 900 °C and 0.21 bar O2 in the feed which corresponds to a 40% increase over the Fe-doped sample and similar to reported values for x=0.2. While the O2 permeability of the Mg doped sample was also higher than the Fe-doped sample, it approached that of the Fe-doped sample above 900 °C. According to the DFT calculations, Mn introduces electronic states within the band gap and will predominately exist in the effectively negative charge state, as indicated by XPS measurements. Mn may therefore improve the ionic and electronic conductivity of CTF based membranes. The results are discussed in terms of the limiting species for ambipolar transport and O2 permeability, i.e., oxygen vacancies and electronic charge carriers.
Keywords Dense ceramic oxygen membrane; Ambipolar transport; Mixed ionic-electronic conduction; CaTiO3; Calcium titanate
Remark doi:10.1016/j.memsci.2015.02.036
Link
ID=297

Solid oxide fuel cells with (La,Sr)(Ga,Mg)O3-δ electrolyte film deposited by radio-frequency magnetron sputtering

Authors Sea-Fue Wang, His-Chuan Lu, Yung-Fu Hsu, Yi-Xuan Hu
Source
Journal of Power Sources
Volume: 281, Pages: 258–264
Time of Publication: 2015
Abstract In this study, solid oxide fuel cells (SOFCs) containing a high quality La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) film deposited on anode supported substrate using RF magnetron sputtering are successfully prepared. The anode substrate is composed of two functional NiO/Sm0.2Ce0.8O2-δ (SDC) composite layers with ratios of 60/40 wt% and 50/50 wt% and a current collector layer of pure NiO. The as-deposited LSGM film appears to be amorphous in nature. After post-annealing at 1000 °C, a uniform and dense polycrystalline film with a composition of La0.87Sr0.13Ga0.85Mg0.15O3-δ and a thickness of 3.8 μm is obtained, which was well adhered to the anode substrate. A composite LSGM/La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) layer, with a ratio of 30/70 wt%, is used as the cathode. The SOFC prepared reveals a good mechanical integrity with no sign of cracking, delamination, or discontinuity among the interfaces. The total cell resistance of a single cell with LSGM electrolyte film declines from 0.60 to 0.10 Ω cm2 as the temperature escalates from 600 to 800 °C and the open circuit voltage (OCV) ranges from 0.85 to 0.95 V. The maximum power density (MPD) of the single cell is reported as 0.65, 1.02, 1.30, 1.42, and 1.38 W cm−2 at 600, 650, 700, 750, and 800 °C, respectively. The good cell performance leads to the conclusion that RF magnetron sputtering is a feasible deposition method for preparing good quality LSGM films in SOFCs.
Keywords Solid oxide fuel cell; Sputtering; Electrolyte; Doped lanthanum gallate
Remark doi:10.1016/j.jpowsour.2015.01.185
Link
ID=294

Hydrogen separation membranes based on dense ceramic composites in the La27W5O55.5–LaCrO3 system

Authors Jonathan M. Polfus, Wen Xing, Marie-Laure Fontaine, Christelle Denonville, Partow P. Henriksen, Rune Bredesen
Source
Journal of Membrane Science
Volume: 479, Pages: 39–45
Time of Publication: 2015
Abstract Some compositions of ceramic hydrogen permeable membranes are promising for integration in high temperature processes such as steam methane reforming due to their high chemical stability in large chemical gradients and CO2 containing atmospheres. In the present work, we investigate the hydrogen permeability of densely sintered ceramic composites (cercer) of two mixed ionic-electronic conductors: La27W3.5Mo1.5O55.5−δ (LWM) containing 30, 40 and 50 wt% La0.87Sr0.13CrO3−δ (LSC). Hydrogen permeation was characterized as a function of temperature, feed side hydrogen partial pressure (0.1–0.9 bar) with wet and dry sweep gas. In order to assess potentially limiting surface kinetics, measurements were also carried out after applying a catalytic Pt-coating to the feed and sweep side surfaces. The apparent hydrogen permeability, with contribution from both H2 permeation and water splitting on the sweep side, was highest for LWM70-LSC30 with both wet and dry sweep gas. The Pt-coating further enhances the apparent H2 permeability, particularly at lower temperatures. The apparent H2 permeability at 700 °C in wet 50% H2 was 1.1×10−3 mL min−1 cm−1 with wet sweep gas, which is higher than for the pure LWM material. The present work demonstrates that designing dual-phase ceramic composites of mixed ionic-electronic conductors is a promising strategy for enhancing the ambipolar conductivity and gas permeability of dense ceramic membranes.
Keywords Hydrogen separation; Dense ceramic membrane; Ceramic&#8211;ceramic composite; Lanthanum tungstate; Lanthanum chromite
Remark doi:10.1016/j.memsci.2015.01.027
Link
ID=208

Effects of Nb5+, Mo6+, and W6+ dopants on the germanate-based apatites as electrolyte for use in solid oxide fuel cells

Authors Sea-Fue Wang, Yung-Fu Hsu, Wan-Ju Lin
Source
International Journal of Hydrogen Energy
Volume: 38, Issue: 27, Pages: 12015–12023
Time of Publication: 2013-09
Abstract Rare information is available in the literature on the cell performance of the solid oxide fuel cells (SOFCs) using apatites known for their good electrical conductivity as electrolyte materials. In this study, La9.5Ge5.5Nb0.5O26.5, La9.5Ge5.5Mo0.5O26.75, and La9.5Ge5.5W0.5O26.75 ceramics were prepared and characterized. The results indicated that the La9.5Ge5.5Nb0.5O26.5 and La9.5Ge5.5W0.5O26.75 ceramics reported hexagonal phase, while the La9.5Ge5.5Mo0.5O26.75 ceramic demonstrated triclinic symmetry. Among the apatities evaluated, La9.5Ge5.5Nb0.5O26.5 sintered at 1450 °C showed the best conduction with an electrical conductivity value of 0.045 S/cm at 800 °C. Button cells of NiO–SDC/La9.5Ge5.5Nb0.5O26.5/LSCF–SDC were built and revealed good structural integrity. The total ohmic resistance (R0) and interfacial polarization resistance (RP) of the cell read 0.428 and 0.174 Ω cm2 and 0.871 and 1.164 Ω cm2, respectively at 950 and 800 °C. The maximum power densities (MPD) of the single cell at 950 and 800 °C were respectively 0.363 and 0.095 W cm−2. Without optimizing the anode and cathode as well as hermetic sealing of the cell against the gas, the study found the performance of the single cell with the pure La9.5Ge5.5Nb0.5O26.5 as its electrolyte material superior to those of the SOFC cells with a YSZ electrolyte of comparable thickness shown in the literature.
Keywords Solid oxide fuel cell; Apatite; Impedance; Cell performance
Remark Link
ID=153

Impact of Parylene-A Encapsulation on ZnO Nanobridge Sensors and Sensitivity Enhancement via Continuous Ultraviolet Illumination

Authors C.-C. Huang, A.D. Mason, J.F. Conley, C. Heist, M.T. Koesdjojo, V.T. Remcho and T. Afentakis
Source
Journal of Electronic Materials
Volume: 41, Issue: 5, Pages: 873-880
Time of Publication: 2012-05
Abstract The impact of parylene-A encapsulation and the effect of continuous ultraviolet (UV) exposure on ZnO nanobridge sensor response are investigated. ZnO nanowire (NW) devices are fabricated using a novel method that involves selective growth of ZnO nanobridges between lithographically defined pads of carbonized photoresist (C-PR). We find that a thin coating of parylene-A effectively attenuates the response of NW devices to O2, H2O vapor, and UV illumination. The accessibility of the amine group on parylene-A for chemical functionalization is verified by transforming the amine groups on the surface of the parylene-A coating into aromatic imine groups, followed by UV–Vis absorption. Our results suggest that, in addition to modulating environmental sensitivity and providing protection of the ZnO NWs for liquid- and vapor-phase sensing, the parylene-A encapsulation may also serve as an activation layer for further specific functionalization targeting selective sensing. We also found that the sensitivity and response time of ZnO nanobridge devices to O2 are dramatically improved by continuously exposing the nanobridge devices to UV illumination. Finally, we show that the C-PR directed growth method can also be used to isolate free-standing NW carpet.
Keywords ZnO &#8211; nanowire &#8211; parylene &#8211; CVD &#8211; nanobridge &#8211; sensor &#8211; functionalization &#8211; directed integration
Remark Link
norecs.com

This article is the property of its author, please do not redistribute or use elsewhere without checking with the author.