Mechanistic Studies of Liquid Metal Anode SOFCs: I. Oxidation of Hydrogen in Chemical - Electrochemical Mode

Liquid metal anode (LMA) solid oxide fuel cells (SOFCs) are a promising type of high temperature fuel cell suitable for the direct oxidation of gaseous or solid fuel. Depending upon the operating conditions they can be run in four different modes. In this first of a series of studies concerning the mechanism of reaction and species transport in LMA SOFCs, the oxidation of hydrogen fuel in a liquid tin anode has been investigated. An electrochemical model is developed based upon fast dissolution of hydrogen in a molten tin anode, slow, rate-determining homogeneous reaction of hydrogen with oxygen dissolved in the liquid tin, followed by anodic oxygen injection under diffusion control to replace the oxygen removed by reaction (so-called Chemical - Electrochemical mode or CE mode). Experimentally-generated data are used to validate the model. The model has introduced a new key parameter, z¯, which takes a value between zero and unity; its value is determined by geometric and convective factors in the cell as well as the partial pressure of the supplied hydrogen fuel. Current output of the cell is proportional to the value of z¯

Trends In Mathematics Enrollment And Achievement Gap In St. Louis Area Public High Schools, 2000 - 2014.

Long before the “No Child Left Behind”, Elementary and Secondary Education Act of 1965, or Brown vs. Board of Education, students of color have dreamed and struggled for equity in education. The issue of equal access to high quality of education highlighted in the NCLB focused public attention on the racial achievement gap. The present study examined mathematics enrollment and achievement trends among St. Louis area public high school students from 2000 to 2014 The study compared the results among racial groups and by gender rather than using a traditional Black-White comparison. Several frameworks contributed to the development of the study: Critical Race Theory, Effectively Maintained Inequality and Whiteness as property. Although the findings showed that enrollment in advanced mathematics classes and the number of students taking ACT tests increased across the racial groups, the results also indicated inequities in access to Advanced Placement classes, and level of college readiness. In conclusion, there is a little change in providing equitable access to advanced levels of mathematics with students who need it most receiving the least help and therefore remain far from closing the achievement gap

A novel molten-salt electrochemical cell for investigating the reduction of uranium dioxide to uranium metal by lithium using in situ synchrotron radiation

A novel electrochemical cell has been designed and built to allow for in situ energy-dispersive X-ray diffraction measurements to be made during reduction of UO2 to U metal in LiCl-KCl at 500C. The electrochemical cell contains arecessed well at the bottom of the cell into which the working electrode sits, reducing the beam path for the X-rays through the molten-salt and maximizing the signal-to-noise ratio from the sample. Lithium metal was electrodeposited onto the UO2 working electrode by exposing the working electrode to more negative potentials than the Li deposition potential of the LiCl-KCl eutectic electrolyte. The Li metal acts as a reducing agent for the chemical reduction of UO2 to U, which appears to proceed to completion. All phases were fitted using Le Bail refinement. The cell is expected to be widely applicable to many studies involving molten-salt systems

Characteristics of a gold-doped electrode for application in high-performance lithium-sulfur battery

Bulk sulfur incorporating 3 wt% gold nano-powder is investigated as possible candidate to maximize the fraction of active material in the Li-S battery cathode. The material is prepared via simple mixing of gold with molten sulfur at 120 °C, quenching at room temperature, and grinding. Our comprehensive study reports relevant electrochemical data, advanced X-ray computed tomography (CT) imaging of the positive and negative electrodes, and a thorough structural and morphological characterization of the S:Au 97:3 w/w composite. This cathode exhibits high rate capability within the range from C/10 to 1C, a maximum capacity above 1300 mAh gS−1, and capacity retention between 85% and 91% after 100 cycles at 1C and C/3 rates. The novel formulation enables a sulfur fraction in the composite cathode film as high as 78 wt%, an active material loading of 5.7 mg cm−2, and an electrolyte/sulfur (E/S) ratio of 5 μL mg−1, which lead to a maximum areal capacity of 5.4 mAh cm−2. X-ray CT at the micro- and nanoscale reveals the microstructural features of the positive electrode that favor fast conversion kinetics in the battery. Quantitative analysis of sulfur distribution in the porous cathode displays that electrodeposition during the initial cycle may trigger an activation process in the cell leading to improved performance. Furthermore, the tomography study reveals the characteristics of the lithium anode and the cell separator upon a galvanostatic test prolonged over 300 cycles at a 2C rate

Degradation of Layered Oxide Cathode in a Sodium Battery: A Detailed Investigation by X-Ray Tomography at the Nanoscale

The degradation mechanism in a sodium cell of a layered Na0.48Al0.03Co0.18Ni0.18Mn0.47O2 (NCAM) cathode with P3/P2 structure is investigated by revealing the changes in microstructure and composition upon cycling. The work aims to rationalize the gradual performance decay and the alteration of the electrochemical response in terms of polarization, voltage signature, and capacity loss. Spatial reconstructions of the electrode by X-ray computed tomography at the nanoscale supported by quantitative and qualitative analyses show fractures and deformations in the cycled layered metal-oxide particles, as well as inorganic side compounds deposited on the material. These irreversible morphological modifications reflect structural heterogeneities across the cathode particles due to formation of various domains with different Na+ intercalation degrees. Besides, X-ray photoelectron spectroscopy data suggest that the latter inorganic species in the cycled electrode are mainly composed of NaF, Na2O, and NaCO3 formed by parasitic electrolyte decomposition. The precipitation of these insulating compounds at the electrode/electrolyte interphase and the related structural stresses induced in the material lead to a decrease in cathode particle size and partial loss of electrochemical activity. The retention of the NCAM phase after cycling suggests that electrolyte upgrade may improve the performance of the cathode to achieve practical application for sustainable energy storage

The role of synthesis pathway on the microstructural characteristics of sulfur-carbon composites: X-ray imaging and electrochemistry in lithium battery

Two synthesis pathways are adopted to tune the microstructural characteristics of sulfur-carbon (S-C) composites for application in lithium-sulfur (Li-S) batteries. Both methods include intimate mixing of either carbon black or multiwalled carbon nanotubes with elemental sulfur, molten according to the first approach while dispersed in alcohol and heated according to the second one. Nano- and micro-scale X-ray computed tomography supported by X-ray diffraction and electron microscopy shows materials consisting of crystalline sulfur clusters (70 wt%) with size ranging from about 5 to 50 μm, surrounded by carbon. The sulfur cluster size appears limited by direct mixing of molten sulfur and carbons, in particular when carbon black is employed, whilst it is increased by exploiting the alcohol dispersion. Electrochemistry reveals that small sulfur particles lead to an improved rate capability in Li-S cells, whereas large active material domains may favor the capacity retention. The composites using carbon black nanoparticles exhibit the highest reversible capacity, with a maximum value exceeding 1500 mAh gS−1, whereas the composites involving multiwalled carbon nanotubes show the best capacity retention, with values approaching 70% over 150 cycles. Our multi-disciplinary approach will shed light on significant aspects aiming to enhance the Li-S battery and favor a practical application

Oxygen evolution catalysts under proton exchange membrane conditions in a conventional three electrode cell vs. electrolyser device: a comparison study and a 3D-printed electrolyser for academic labs dagger

Developing active and stable oxygen evolution reaction (OER) catalysts that can operate in electrolyser environments is of utmost important in order to produce H2 gas for electricity generation. Currently in academia, many of these studies are carried out in conventional three-electrode cell set-ups; however, this configuration may not accurately represent conditions experienced under practical electrolyser conditions. Herein, a range of transition metal oxide (TMO) catalysts are evaluated and compared in a three-electrode cell and in an electrolyser. We show that the same catalyst significantly underperforms in a three-electrode cell. Hence, many OER catalysts in academic labs may have been erroneously omitted from further optimisation processes due to showing ‘poor’ performance in conventional three-electrode cells. Herein, we wish to show this discrepancy experimentally and suggest a solution to scientists wanting to find active OER catalysts by using 3D-printing to inexpensively manufacture electrolyser devices for OER catalyst evaluation

Experiencing visual impairment in a lifetime home: an interpretative phenomenological inquiry

Lifetime home standards (LTHS) are a set of standards aimed at making homes more accessible. Previous research, however, indicates that LTHS do not adequately meet the needs of those with sensory impairments. Now, with visual impairment set to increase globally and acknowledging the recognised link between quality of dwelling and wellbeing, this article aims to examine the experiences of visually impaired people living in lifetime homes. The objectives are to investigate existing lifetime homes and to identify whether LTHS meet occupants’ needs. Qualitative semi-structured interviews were carried out with six visually impaired people living in homes designed to LTHS in Northern Ireland. Collected data was analysed using interpretative phenomenological analysis identifying three super-ordinate themes: (1) living with visual impairment; (2) design considerations and (3) coping strategies. A core theme of balance between psychological and physical needs emerged through interconnection of super-ordinate themes. Although there are benefits to living in lifetime homes, negative aspects are also apparent with occupants employing several coping strategies to overcome difficulties. Whilst residents experience negative emotions following visual impairment diagnoses, results suggest that occupants still regard their homes as key places of security and comfort in addition to then highlighting the need for greater consideration of specific individual needs within general guidelines

Nodal governance of security

ARTIKELEN: J. Wood en C.D. Shearing - De nodale politiefunctie R. van Steden - Burgerparticipatie in lokale veiligheidsnetwerken; over 'nodale sturing' en 'verankerd pluralisme' M.B. Schuilenburg, A. Coenraads en P. van Calster - Onder de mensen; de aanpak van transportcriminaliteit door politie, verzekeraars en schade-experts A.B. Hoogenboom - Dingen veranderen en blijven gelijk A. van Sluis en V. Bekkers - De ontknoping van de modale oriëntatie; op zoek naar randvoorwaarden en kritische factoren P. van Calster en M.B. Schuilenburg - Burgernet vanuit een nodal governance-perspectief J. Terpstra - Nodale sturing van veiligheid en lokale veiligheidsnetwerken; over de beperkingen van een perspectief SAMENVATTING: De afgelopen twintig jaar hebben de opkomst laten zien van nieuwe publieke en private partijen in de veiligheidszorg. Niet alleen de overheid, en in het verlengde daarvan de politie, wordt geacht een taak te vervullen op dit terrein, maar daarnaast ook een bonte verzameling van maatschappelijke actoren. In meer of mindere mate is daarbij sprake van samenwerking met de politie. In het perspectief van 'nodal governance' is de veiligheidszorg niet georganiseerd vanuit één positie, maar krijgt vorm door meerder actoren die zich opstellen rondom een concreet probleem