Imperial College London

Professor Nigel Brandon OBE FREng

Faculty of Engineering

Dean of the Faculty of Engineering
 
 
 
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Contact

 

+44 (0)20 7594 8600n.brandon Website

 
 
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Location

 

2.06Faculty BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

405 results found

Chen J, Ruiz-Trejo E, Atkinson A, Brandon NPet al., 2017, Microstructural and Electrochemical Characterisation of Degradation in Nickel Impregnated Scandia-stabilised Zirconia Electrode during Isothermal Annealing, 15th International Symposium on Solid Oxide Fuel Cells (SOFC), Publisher: ELECTROCHEMICAL SOC INC, Pages: 1125-1137, ISSN: 1938-5862

Conference paper

Mukerjee S, Leah R, Selby M, Stevenson G, Brandon NPet al., 2017, Life and Reliability of Solid Oxide Fuel Cell-Based Products: A Review, Solid Oxide Fuel Cell Lifetime and Reliability: Critical Challenges in Fuel Cells, Pages: 173-191, ISBN: 9780081011027

© 2017 Elsevier Ltd. All rights reserved. Solid oxide fuel cells (SOFCs) are a technology rapidly developing toward widespread commercialization, with hundreds of megawatts of generation capacity installed in the field for large-scale power generation (100. kW-1. MW), and small-scale distributed power generation (<5. kW scale) undergoing large precommercial field trials in Europe and Japan. Although rapidly improving, challenges still remain in achieving SOFC stack operating lives of up to 90,000. h at a cost competitive with more established power generation technology. This chapter provides a review of the current development status of the main SOFC developers and technology variants based on publicly available literature. The techniques being developed to accelerate technology development cycles by enabling lifetime prediction from relatively short-duration tests are also discussed.

Book chapter

Bertei A, Tariq F, Yufit V, Ruiz Trejo E, Brandon Net al., 2016, Guidelines for the rational design and engineering of 3D manufactured solid oxide fuel cell composite electrodes, Journal of the Electrochemical Society, Vol: 164, Pages: F89-F98, ISSN: 0013-4651

The growth of 3D printing has opened the scope for designing microstructures for solid oxide fuel cells(SOFCs) with improved power density and lifetime. This technique can introduce structural modifications at a scale larger than particle size but smaller than cell size, such as by insertingelectrolyte pillars of ~5-100 µm. This study sets the minimum requirements for the rational design of 3D printedelectrodes based on an electrochemical model and analytical solutions for functional layers with negligible electronic resistanceand no mixed conduction. Results show that this structural modification enhances the power density when the ratio keffbetween effective conductivity and bulk conductivity of the ionic phase is smaller than 0.5. The maximum performance improvement is predicted as a function of keff. A design study on a wide range of pillar shapes indicates that improvements are achieved by any structural modification which provides ionic conduction up to a characteristic thickness ~10-40 µm without removing active volume at the electrolyte interface. The best performance is reached for thin (< ~2 µm) and long (> ~80 µm) pillars when the compositeelectrode is optimised for maximum three-phase boundarydensity, pointing towards the design of scaffolds with well-defined geometry and fractal structures.

Journal article

Parkes MA, Tompsett DA, d'Avezac M, Offer GJ, Brandon NP, Harrison NMet al., 2016, The atomistic structure of yttria stabilised zirconia at 6.7 mol%: an ab initio study., Physical Chemistry Chemical Physics, Vol: 18, Pages: 31277-31285, ISSN: 1463-9084

Yttria stabilized zirconia (YSZ) is an important oxide ion conductor used in solid oxide fuel cells, oxygen sensing devices, and for oxygen separation. Doping pure zirconia (ZrO2) with yttria (Y2O3) stabilizes the cubic structure against phonon induced distortions and this facilitates high oxide ion conductivity. The local atomic structure of the dopant is, however, not fully understood. X-ray and neutron diffraction experiments have established that, for dopant concentrations below 40 mol% Y2O3, no long range order is established. A variety of local structures have been suggested on the basis of theoretical and computational models of dopant energetics. These studies have been restricted by the difficulty of establishing force field models with predictive accuracy or exploring the large space of dopant configurations with first principles theory. In the current study a comprehensive search for all symmetry independent configurations (2857 candidates) is performed for 6.7 mol% YSZ modelled in a 2 × 2 × 2 periodic supercell using gradient corrected density functional theory. The lowest energy dopant structures are found to have oxygen vacancy pairs preferentially aligned along the ⟨210⟩ crystallographic direction in contrast to previous results which have suggested that orientation along the ⟨111⟩ orientation is favourable. Analysis of the defect structures suggests that the Y(3+)-Ovac interatomic separation is an important parameter for determining the relative configurational energies. Current force field models are found to be poor predictors of the lowest energy structures. It is suggested that the energies from a simple point charge model evaluated at unrelaxed geometries is actually a better descriptor of the energy ordering of dopant structures. Using these observations a pragmatic procedure for identifying low energy structures in more complicated material models is suggested. Calculation of the oxygen vacancy migration activat

Journal article

Boldrin P, Ruiz Trejo E, Mermelstein J, Bermudez Menendez J, Ramirez Reina T, Brandon Net al., Strategies for carbon and sulfur tolerant solid oxide fuel cell materials, incorporating lessons from heterogeneous catalysis, Chemical Reviews, Vol: 116, Pages: 13633-13684, ISSN: 1520-6890

Solid oxide fuel cells (SOFCs) are a rapidly emerging energy technology for a low carbon world, providing high efficiency, potential to use carbonaceous fuels and compatibility with carbon capture and storage. However, current state-of-the-art materials have low tolerance to sulfur, a common contaminant of many fuels, and are vulnerable to deactivation due to carbon deposition when using carbon-containing compounds. In this review we first study the theoretical basis behind carbon and sulfur poisoning, before examining the strategies towards carbon and sulfur tolerance used so far in the SOFC literature. We then study the more extensive relevant heterogeneous catalysis literature for strategies and materials which could be incorporated into carbon and sulfur tolerant fuel cells.

Journal article

Chakrabarti BK, Nir DP, Yufit V, Tariq F, Rubio Garcia J, Maher R, Kucernak A, Aravind PV, Brandon NPet al., 2016, Studies of performance enhancement of rGO-modified carbon electrodes for Vanadium Redox Flow Systems, ChemElectroChem, Vol: 4, Pages: 194-200, ISSN: 2196-0216

Reduced graphene oxide (rGO) suspended in an N,N′-dimethylformamide (DMF) solvent underwent electrophoretic deposition (EPD) on carbon paper (CP) electrodes. X-ray computed micro-tomography (XMT) indicates a 24 % increase in the specific surface area of CP modified with rGO in comparison to the untreated sample. Furthermore, XMT confirms that the deposition also penetrates into the substrate. Raman analysis shows that the rGO deposited is more amorphous than the CP electrode. A significant reduction in charge-transfer resistance of the VO2+/VO2+ reaction is also observed (from impedance measurements) in modified samples in comparison to untreated CP electrodes.

Journal article

Cooper SJ, Bertei A, Shearing PR, Kilner JA, Brandon NPet al., 2016, TauFactor: An open-source application for calculating tortuosity factors from tomographic data, SoftwareX, Vol: 5, Pages: 203-210, ISSN: 2352-7110

TauFactor is a MatLab application for efficiently calculating the tortuosity factor, as well as volume fractions, surface areas and triple phase boundary densities, from image based microstructural data. The tortuosity factor quantifies the apparent decrease in diffusive transport resulting from convolutions of the flow paths through porous media. TauFactor was originally developed to improve the understanding of electrode microstructures for batteries and fuel cells; however, the tortuosity factor has been of interest to a wide range of disciplines for over a century, including geoscience, biology and optics. It is still common practice to use correlations, such as that developed by Bruggeman, to approximate the tortuosity factor, but in recent years the increasing availability of 3D imaging techniques has spurred interest in calculating this quantity more directly. This tool provides a fast and accurate computational platform applicable to the big datasets (>10^8 voxels) typical of modern tomography, without requiring high computational power.

Journal article

Chen Z, Wang X, Brandon N, Atkinson Aet al., 2016, Analysis of spherical indentation of porous ceramic films, Journal of the European Ceramic Society, Vol: 37, Pages: 1031-1038, ISSN: 1873-619X

Spherical indentation of a porous brittle La0.6Sr0.4Co0.2Fe0.8O3 ceramic film (porosity=39.7%) on a stiffer elastic Ce0.9Gd0.1O1.95 substrate is simulated by finite element modelling incorporating the Gurson model to account for densification. The simulated load-displacement curves, apparent elastic modulus E, indentation hardness H and densification profile are all in good agreement with experimental data for the film. The simulations show that E and H are not sensitive to film residual stress. However E is very sensitive to the indent depth-film thickness ratio f, although H is less so for f<0.3. The simulated dependence of E and H on f are highly consistent with experimental data, supporting the extrapolation of E and H measured for 0.1<f<0.3, to zero depth for good estimates of the film-alone properties. The inclusion of densification in the simulation makes only a small difference to E, but has a large influence on H as a function of indentation depth.

Journal article

Ruiz Trejo E, Puolamaa M, Sum B, Tariq F, Yufit V, Brandon NPet al., 2016, New method for the deposition of nickel oxide in porous scaffolds for electrodes in solid oxide fuel cells and electrolyzers, Chemsuschem, Vol: 10, Pages: 258-265, ISSN: 1864-564X

A simple chemical bath deposition is used to coat a complex porous ceramic scaffold with a conformal nickel layer. The resulting composite is used as a Solid Oxide Fuel Cell electrode and its electrochemical response is measured in humidified hydrogen. X-Ray tomography is used to determine microstructural parameters of the uncoated and Ni-coated porous structure, among other, the surface area to total volume, the radial pore size and size of the necks between pores.

Journal article

Liu X, Jervis R, Maher RC, Villar Garcia I, Naylor Marlow M, Shearing P, Ouyang M, Cohen L, Brandon N, Wu Bet al., 2016, 3D-Printed Structural Pseudocapacitors, Advanced Materials Technologies, Vol: 1, ISSN: 2365-709X

Direct metal laser sintering is used to create 3D hierarchical porous metallic scaffolds which are then functionalized with a co-electrodeposition of MnO2, Mn2O3, and doped conducting polymer. This approach of functionalizing metal 3D printed scaffolds thus opens new possibilities for structural energy storage devices with enhanced performance and lifetime characteristics.

Journal article

Balcombe P, Anderson K, Speirs J, Brandon N, Hawkes Aet al., 2016, The natural gas supply chain: the importance of methane and carbon dioxide emissions, ACS Sustainable Chemistry & Engineering, Vol: 5, Pages: 3-20, ISSN: 2168-0485

Natural gas is typically considered to be the cleaner-burning fossil fuel that could play an important role within a restricted carbon budget. While natural gas emits less CO2 when burned than other fossil fuels, its main constituent is methane, which has a much stronger climate forcing impact than CO2 in the short term. Estimates of methane emissions in the natural gas supply chain have been the subject of much controversy, due to uncertainties associated with estimation methods, data quality, and assumptions used. This Perspective presents a comprehensive compilation of estimated CO2 and methane emissions across the global natural gas supply chain, with the aim of providing a balanced insight for academia, industry, and policy makers by summarizing the reported data, locating the areas of major uncertainty, and identifying where further work is needed to reduce or remove this uncertainty. Overall, the range of documented estimates of methane emissions across the supply chain is vast among an aggregation of different geological formations, technologies, plant age, gas composition, and regional regulation, not to mention differences in estimation methods. Estimates of combined methane and CO2 emissions ranged from 2 to 42 g CO2 eq/MJ HHV, while methane-only emissions ranged from 0.2% to 10% of produced methane. The methane emissions at the extraction stage are the most contentious issue, with limited data available but potentially large impacts associated with well completions for unconventional gas, liquids unloading, and also the transmission stage. From the range of literature estimates, a constrained range of emissions was estimated that reflects the most recent and reliable estimates: total supply chain GHG emissions were estimated to be between 3.6 and 42.4 g CO2 eq/MJ HHV, with a central estimate of 10.5. The presence of “super emitters”, a small number of facilities or equipment that cause extremely high emissions, is found across all supply chai

Journal article

Bertei A, Ruiz-Trejo E, Tariq F, Yufit V, Atkinson A, Brandon NPet al., 2016, Validation of a physically-based solid oxide fuel cell anode model combining 3D tomography and impedance spectroscopy, International Journal of Hydrogen Energy, Vol: 41, Pages: 22381-22393, ISSN: 1879-3487

This study presents a physically-based model for the simulation of impedance spectra in solid oxide fuel cell (SOFC) composite anodes. The model takes into account the charge transport and the charge-transfer reaction at the three-phase boundary distributed along the anode thickness, as well as the phenomena at the electrode/electrolyte interface and the multicomponent gas diffusion in the test rig. The model is calibrated with experimental impedance spectra of cermet anodes made of nickel and scandia-stabilized zirconia and satisfactorily validated in electrodes with different microstructural properties, quantified through focused ion beam SEM tomography. Besides providing the material-specific kinetic parameters of the electrochemical hydrogen oxidation, this study shows that the correlation between electrode microstructure and electrochemical performance can be successfully addressed by combining physically-based modelling, impedance spectroscopy and 3D tomography. This approach overcomes the limits of phenomenological equivalent circuits and is suitable for the interpretation of experimental data and for the optimisation of the electrode microstructure.

Journal article

Merla Y, Wu B, Yufit V, Brandon NP, Martinez-Botas R, Offer Get al., 2016, Extending battery life: A low-cost practical diagnostic technique for lithium-ion batteries, Journal of Power Sources, Vol: 331, Pages: 224-231, ISSN: 1873-2755

Modern applications of lithium-ion batteries such as smartphones, hybrid & electric vehiclesand grid scale electricity storage demand long lifetime and high performance which typicallymakes them the limiting factor in a system. Understanding the state-of-health during operationis important in order to optimise for long term durability and performance. However, thisrequires accurate in-operando diagnostic techniques that are cost effective and practical. Wepresent a novel diagnosis method based upon differential thermal voltammetry demonstratedon a battery pack made from commercial lithium-ion cells where one cell was deliberately agedprior to experiment. The cells were in parallel whilst being thermally managed with forced airconvection. We show for the first time, a diagnosis method capable of quantitativelydetermining the state-of-health of four cells simultaneously by only using temperature and 2voltage readings for both charge and discharge. Measurements are achieved using low-costthermocouples and a single voltage measurement at a frequency of 1Hz, demonstrating thefeasibility of implementing this approach on real world battery management systems. Thetechnique could be particularly useful under charge when constant current or constant power iscommon, this therefore should be of significant interest to all lithium-ion battery users.

Journal article

Biton M, Yufit V, Tariq F, Kishimoto M, Brandon NPet al., 2016, Enhanced Imaging of Lithium Ion Battery Electrode Materials, Journal of the Electrochemical Society, Vol: 164, Pages: A6032-A6038, ISSN: 0013-4651

In this study we present a novel method of lithium ion battery electrode sample preparation with a new type of epoxy impregnation,brominated (Br) epoxy, which is introduced here for the first time for this purpose and found suitable for focused ion beam scanningelectron microscope (FIB-SEM) tomography. The Br epoxy improves image contrast, which enables higher FIB-SEM resolution (3Dimaging), which is amongst the highest ever reported for composite LFP cathodes using FIB-SEM. In turn it means that the particlesare well defined and the size distribution of each phase can be analyzed accurately from the complex 3D electrode microstructureusing advanced quantification algorithms.The authors present for the first time a new methodology of contrast enhancement for 3D imaging, including novel advancedquantification, on a commercial Lithium Iron Phosphate (LFP) LiFePO4 cathode. The aim of this work is to improve the quality ofthe 3D imaging of challenging battery materials by developing methods to increase contrast between otherwise previously poorlydifferentiated phases. This is necessary to enable capture of the real geometry of electrode microstructures, which allows measurementof a wide range of microstructural properties such as pore/particle size distributions, surface area, tortuosity and porosity. Theseproperties play vital roles in determining the performance of battery electrodes.

Journal article

Liu X, Wu B, Brandon NP, Wang Qet al., 2016, Tough ionogel-in-mask hybrid gel electrolytes in supercapacitors with durable pressure and thermal tolerances, Energy Technology, Vol: 5, Pages: 220-224, ISSN: 2194-4288

A primary challenge of gel electrolytes in development of flexible and wearable devices is their weak mechanical performances, including their compressive stress, tensile strength, and puncture resistance. Here we prepare an ionogel-mask hybrid gel electrolyte, which successfully achieves synergic advantages of the high mechanical strength of the mask substance and the superior electrochemical and thermal characteristics of the ionogel. The fabricated supercapacitor can maintain a relatively stable capacitive performance even under a high pressure of 3236 kPa. Meanwhile, with the good thermal stability of the composite gel electrolyte, the solid-state supercapacitor can be operated at high temperatures ranging from 25 °C to 200 °C. The ionogel-mask hybrid gel can be superior tough gel electrolyte for solid-state flexible supercapacitors with durable advantages in both high temperatures and pressures.

Journal article

Wu B, Parkes MP, de Benedetti L, Marquis AJ, Offer GJ, Brandon NPet al., 2016, Real-time monitoring of proton exchange membrane fuel cell stack failure, Journal of Applied Electrochemistry, Vol: 46, Pages: 1157-1162, ISSN: 1572-8838

Uneven pressure drops in a 75-cell 9.5-kWe protonexchange membrane fuel cell stack with a U-shaped flowconfiguration have been shown to cause localised flooding.Condensed water then leads to localised cell heating, resultingin reduced membrane durability. Upon purging of the anodemanifold, the resulting mechanical strain on the membranecan lead to the formation of a pin-hole/membrane crack and arapid decrease in open circuit voltage due to gas crossover.This failure has the potential to cascade to neighbouring cellsdue to the bipolar plate coupling and the current densityheterogeneities arising from the pin-hole/membrane crack.Reintroduction of hydrogen after failure results in cell voltageloss propagating from the pin-hole/membrane crack locationdue to reactant crossover from the anode to the cathode, giventhat the anode pressure is higher than the cathode pressure.Through these observations, it is recommended that purging isavoided when the onset of flooding is observed to preventirreparable damage to the stack.

Journal article

Dong J, Wu X, Chen Y, Brandon N, Li X, Yang J, Yu J, Zhang W, Hu Y, Yu W, Wang J, Liang S, Hu J, Hou H, Liu B, Yang Cet al., 2016, A study on Pb2+/Pb electrodes for soluble lead redox flow cells prepared with methanesulfonic acid and recycled lead, Journal of Applied Electrochemistry, Vol: 46, Pages: 861-868, ISSN: 1572-8838

Electrodeposition and electrodissolution reactionsof the Pb2?/Pb electrode were studied on a glassy carbonrotating disk electrode in aqueous solutions of CH3SO3H andPb(CH3SO3)2. The electrolytic parameters, kinematic viscosityand ionic conductivity, were determined with variousconcentrations of CH3SO3H and Pb(CH3SO3)2. The diffusioncoefficient of Pb2? in this electrolyte prepared with CH3SO3Hwas determined by the Levich Equation. Both the concentrationsof CH3SO3H and Pb(CH3SO3)2 were found responsiblefor the equilibrium potential shifts and exchange currentdensity variations. The electrochemical processes at the Pb2?/Pb electrode were identified as being under mixed ohmicdiffusioncontrol. The electrolyte conductivity and the ionicactivity of Pb2? were recognized as important parameters fordesigning the soluble lead redox flow cells. During constantcurrent charge–discharge measurement, the specific capacityof the Pb2?/Pb electrode was about 253 mAh g-1Pb, about98 % of the theoretical value. The impurity elements Fe, Ba,Al, and Zn in the Pb2? electrolytes prepared with recycledlead exhibited insignificant influences on the Pb2?/Pb reactions.It is reasonable to believe that the recycled lead can beapplied in soluble lead redox flow batteries, and the cost maybe further reduced with recycled lead because expensiveimpurity-control processes seemed to be avoidable.

Journal article

Chen Z, Wang X, Atkinson A, Brandon Net al., 2016, Spherical indentation of porous ceramics: cracking and toughness, Journal of the European Ceramic Society, Vol: 36, Pages: 3473-3480, ISSN: 0955-2219

A combined experimental-numerical approach is used to characterise the fracture of a porous bulk ceramic material (La0.6Sr0.4Co0.2Fe0.8O3) with porosities of 5-45%, undergoing spherical indentation. The Gurson model was used in FEM to describe the densification of the porous material. Indentation-induced radial cracks were observed, when the applied nominal contact pressure exceeded threshold values, with no Hertzian ring-cone cracks found. FEM analysis indicated that the cracks propagated mainly during unloading, driven by the tensile hoop stress generated near the contact circle. The stress intensity at the crack tip was estimated using an approximate analysis of the FEM stress field to derive toughness values that were consistent with values determined by conventional methods, provided that the crack length is sufficiently large compared with the contact radius and can be measured accurately. The absence of ring-cone cracks in the elastic field during loading is due to the material’s high modulus-to-hardness ratio and the small indenter radius as predicted by established theory.

Journal article

Wu B, Ibrahim KA, Brandon NP, 2016, Electrical conductivity and porosity in stainless steel 316L scaffolds for electrochemical devices fabricated using selective laser sintering, Materials and Design, Vol: 109, Pages: 51-59, ISSN: 1873-4197

Battery electrode microstructures must be porous, to provide a large active surface area to facilitate fast charge transfer kinetics. In this work, we describe how a novel porous electrode scaffold, made from stainless steel 316L powder can be fabricated using selective laser sintering by proper selection of process parameters. Porosity, electrical conductivity and optical microscopy measurements were used to investigate the properties of fabricated samples. Our results show that a laser energy density between 1.50–2.00 J/mm2 leads to a partial laser sintering mechanism where the powder particles are partially fused together, resulting in the fabrication of electrode scaffolds with 10% or higher porosity. The sample fabricated using 2.00 J/mm2 energy density (60 W–1200 mm/s) exhibited a good electrical conductivity of 1.80 × 106 S/m with 15.61% of porosity. Moreover, we have observed the porosity changes across height for the sample fabricated at 60 W and 600 mm/s, 5.70% from base and increasing to 7.12% and 9.89% for each 2.5 mm height towards the top surface offering graded properties ideal for electrochemical devices, due to the changing thermal boundary conditions. These highly porous electrode scaffolds can be used as an electrode in electrochemical devices, potentially improving energy density and life cycle.

Journal article

Budinis S, Krevor S, Mac Dowell N, Brandon N, Hawkes Aet al., 2016, Can technology unlock unburnable carbon?

In 2015, the Conference Of the Parties in Paris (COP21) reached a universal agreement on climate change with the aim of limiting global warming to below 2 °C. In order to stay below 2 °C, the total amount of carbon dioxide (CO2) released, or ‘carbon budget’ must be less than 1,000 gigatonnes (Gt) of CO2. At the current emission rate, this budget will be eroded within the next thirty years. Meeting this target on a global scale is challenging and will require prompt and effective climate change mitigation action.The concept of ‘unburnable carbon’ emerged in 2011, and stems from theobservation that if all known fossil fuel reserves are extracted and converted to CO2 (unabated), it would exceed the carbon budget and have a very significant effect on the climate. Therefore, if global warming is to be limited to the COP21 target, some of the known fossil fuel reserves should remain unburnt.Several recent reports have highlighted the scale of the challenge, drawing on scenarios of climate change mitigation and their implications for the projected consumption of fossil fuels. Carbon capture and storage (CCS) is a critical and available mitigation opportunity that is often overlooked. The positive contribution of CCS technology to timely and cost-effective decarbonisation of the energy system is widely recognised. However, while some studies have considered the role of CCS in enabling access to more fossil fuels, no detailed analysis on this issue has been undertaken.This White Paper presents a critical review focusing on the technologies that can be applied to enable access to, or ‘unlock’, fossil fuel reserves in a way that will meet climate targets and mitigate climate change.The paper includes an introduction to the key issues of carbon budgets and fossil fuel reserves, a detailed analysis of the current status of CCS technology, as well as a synthesis of a multi-model comparison study on global climate change mitigation strat

Report

Blanga R, Berman M, Biton M, Tariq F, Yufit V, Gladkich A, Greenbaum SG, Brandon N, Golodnitsky Det al., 2016, Peculiarities of ion transport in confined-in-ceramics concentrated polymer electrolytes, Electrochimica Acta, Vol: 208, Pages: 71-79, ISSN: 1873-3859

Polyethylene-oxide/lithium-aluminate films were deposited by electrophoretic deposition. Films impregnated with lithium iodide formed highly concentrated polymer-in-ceramic solid electrolytes. Solid-state NMR, FIB-SEM tomography with modelling, and EIS studies showed that only a few percent of the interfacial lithium in the sample is capable of inducing a fast ion-migration path in the system. We suggest that despite suppressed crystallinity of PEO confined in ceramics the ion transport in the polymer medium impedes the total conductivity of the composite electrolyte at near-ambient temperatures. After melting of the polymer and its complexes, the interfacial conduction through perpendicular LiAlO2/LiI grain boundaries becomes feasible. This, together with ion transport via molten, confined polymer electrolyte is followed by the increase of the overall conductivity of the composite system.

Journal article

Jamil Z, Ruiz-Trejo E, Boldrin P, Brandon NPet al., 2016, Anode fabrication for solid oxide fuel cells: Electroless and electrodeposition of nickel and silver into doped ceria scaffolds, International Journal of Hydrogen Energy, Vol: 41, Pages: 9627-9637, ISSN: 1879-3487

A novel fabrication method using electroless and electrodeposited Ni/Ag/GDC for SOFC anodes is presented. First a porous Ce0.9Gd0.1O2−x (GDC) scaffold was deposited on a YSZ electrolyte by screen printing and sintering. The scaffold was then metallized with silver using Tollens' reaction, followed by electrodeposition of nickel from a Watt's bath. The electrodes (Ni/Ag/GDC) were tested in both symmetrical and fuel cell configurations. The microstructures of the Ni/Ag/GDC anodes were analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). Nano-particles of Ni formed in the porous GDC scaffold provided triple phase boundaries (TPB). The electronic conductivity of the Ni/Ag/GDC (3.5/24.7/71.8 vol%) electrode was good even at relatively low Ni volume fractions. The electrochemical performance was examined in different concentrations of humidified hydrogen (3% H2O) and over a range of temperatures (600–750 °C). The total area specific resistance (ASR) of the anode at 750 °C in humidified 97 vol% H2 was 1.12 Ω cm2, with low-frequency polarization (R_l) as the largest contributor. The electrodes were successfully integrated into a fuel cell and operated in both H2 and syngas.

Journal article

Chen Z, Brandon N, 2016, Inkjet Printing and Nanoindentation of Porous Alumina Multilayers, Ceramics International, Vol: 42, Pages: 8316-8324, ISSN: 0272-8842

The objectives of this study were to analyse the effect of inkjet 3-D printing parameters,particularly the splat overlap distance, for the fabrication of defect-free porous Al2O3 ceramicmultilayers, and to correlate the resulting porosities with the mechanical properties measured usingnanoindentation. An aqua-based alumina ink was used in this study to fabricate the multilayers ondense alumina substrates by inkjet printing. The as-printed specimens were dried and sintered at 1200– 1500 °C. The resulting microstructural features of each specimen and their corresponding porositieswere studied using FIB-SEM. Elastic modulus and hardness were determined using the sphericalnanoindentation technique. Results showed that defect-free porous alumina multilayers with excellentlayer to layer and layer to substrate integrity were successfully fabricated. The porosity-dependence ofthe elastic modulus and hardness was shown to be consistent with values predicted using empiricalexpressions, despite the presence of abnormal grain growth at higher temperatures.

Journal article

Lanzini A, Guerra C, Leone P, Santarelli M, Smeacetto F, Fiorilli S, Gondolini A, Mercadelli E, Sanson A, Brandon NPet al., 2016, Influence of the microstructure on the catalytic properties of SOFC anodes under dry reforming of methane, MATERIALS LETTERS, Vol: 164, Pages: 312-315, ISSN: 0167-577X

Journal article

Bahadori L, Hashim MA, Manan NSA, Mjalli FS, AlNashef IM, Brandon NP, Chakrabarti MHet al., 2016, Investigation of ammonium- and phosphonium-based deep eutectic solvents as electrolytes for a non-aqueous all-vanadium redox cell, Journal of the Electrochemical Society, Vol: 163, Pages: A632-A638, ISSN: 0013-4651

The charge/discharge characteristics for vanadium acetylacetonate in deep eutectic solvents were evaluated using an H-cell with an anion-exchange membrane separator for the first time. Coulombic (CE) and energy efficiencies (EE) of the electrolyte containing V(acac)3/0.5 M TEABF4 in DES3 (a hydrogen bonded eutectic between choline chloride and ethylene glycol) were obtained as 49–52% and 25–31%, respectively, when charging from 0 to 50% of theoretical maximum state-of-charge for 12 cycles. The low CE may be due to the crossover of the active species through the separator, or to the loss of active vanadium due to a parasitic reaction. However, the CE was similar to that for acetonitrile (CH3CN) indicating the promise of DESs as suitable electrolytes for future evaluation. Charge and discharge voltages are respectively higher and lower than the formal cell potential obtained by voltammetry. Ohmic drop in the DES results from the low conductivity of the electrolyte and the relatively large distance between the two electrodes in the H-cell. Further studies require investigation in a flow cell with analyses of polarization curves and impedance to determine the loss mechanisms in sufficient detail.

Journal article

Maher RC, Shearing PR, Brightman E, Brett DJL, Brandon NP, Cohen LFet al., 2016, Reduction Dynamics of Doped Ceria, Nickel Oxide, and Cermet Composites Probed Using In Situ Raman Spectroscopy, Advanced Science, Vol: 3, ISSN: 2198-3844

The redox properties of gadolinium doped ceria (CGO) and nickel oxide (NiO) composite cermets underpin the operation of solid oxide electrochemical cells. Although these systems have been widely studied, a full comprehension of the reaction dynamics at the interface of these materials is lacking. Here, in situ Raman spectroscopic monitoring of the redox cycle is used to investigate the interplay between the dynamic and competing processes of hydrogen spillover and water dissociation on the doped ceria surface. In order to elucidate these mechanisms, the redox process in pure CGO and NiO is studied when exposed to wet and dry hydrogen and is compared to the cermet behavior. In dry hydrogen, CGO reduces relatively rapidly via a series of intermediate phases, while NiO reduces via a single-step process. In wet reducing atmospheres, however, the oxidation state of pure CGO is initially stabilized due to the dissociation of water by reduced Ce(III) and subsequent incorporation of oxygen into the structure. In the reduction process involving the composite cermet, the close proximity of the NiO improves the efficiency and speed of the composite reduction process. Although NiO is already incorporated into working cells, these observations suggest direct routes to further improve cell performance.

Journal article

Chen Z, Wang X, Atkinson A, Brandon Net al., 2016, Spherical Indentation of Porous Ceramics: Elasticity and Hardness, Journal of the European Ceramic Society, Vol: 36, Pages: 1435-1445, ISSN: 1873-619X

A combined experimental and numerical approach is used to characterise the elastic and plastic deformation of a porous bulk ceramic material (La0.6Sr0.4Co0.2Fe0.8O3, LSCF) with porosities in the range 5–45 vol%, undergoing spherical indentation. The Gurson model was used in FEM simulations to describe the densification of the porous material in the plastic zone under the indenter. The simulated indentation response curves, extracted elastic modulus, hardness and densification in the plastic zone all showed good agreement with corresponding experimental observations. The results show that the hardness increases with maximum indentation depth over a representative depth that depends on porosity. In this particular ceramic the hardness, at sufficiently large penetration depth, is approximately 1.7 times the uniaxial yield stress of the porous material.

Journal article

Wu B, Merla Y, Yufit V, Brandon NP, Martinez-Botas R, Offer GJet al., 2016, Novel application of differential thermal voltammetry as an in-depth state-of-health diagnosis method for lithium-ion batteries, Journal of Power Sources, Vol: 307, Pages: 308-319, ISSN: 1873-2755

Understanding and tracking battery degradation mechanisms and adapting its operation have become a necessity in order to enhance battery durability. A novel use of differential thermal voltammetry (DTV) is presented as an in-situ state-of-health (SOH) estimator for lithium-ion batteries.Accelerated ageing experiments were carried on 5Ah commercial lithium-ion polymer cells operated and stored at different temperature and loading conditions. The cells were analysed regularly with various existing in-situ diagnosis methods and the novel DTV technique to determine their SOH. The diagnosis results were used collectively to elaborate the degradation mechanisms inside the cells. The DTV spectra were decoupled into individual peaks, which each represent particular phases in the negative and positive electrode combined. The peak parameters were used to quantitatively analyse the battery SOH.A different cell of the same chemistry with unknown degradation history was then analysed to explore how the cell degraded. The DTV technique was able to diagnose the cell degradation without relying on supporting results from other methods nor previous cycling data.

Journal article

Samsatli S, Ramos A, Matchett M, Brandon NP, Shah N, Samsatli NJet al., 2016, Whole-Systems Modelling of Alternatives for Future Domestic Transport, Editors: Kravanja, Bogataj, Publisher: ELSEVIER SCIENCE BV, Pages: 457-462

Book chapter

Millan M, Lorente E, Boldrin P, Brandon Net al., 2016, Integration of gasification and fuel cells: Interaction between the anode and contaminants in the syngas

© 2016 International Pittsburgh Coal Conference. All rights reserved. Fouling due to carbon deposition on the fuel cell anode reduces the performance of the cell. • The addition of steam above S/C of 1 was found to reduce carbon deposition from tars but not fully suppress coke formation. • A combination of high S/C=ratio and current density may effectively inhibit carbon formation, maintaining cell performance. • Benzene and toluene represent a "worst-case scenario" as tar models and light fractions are more likely to produce carbon deposits.

Conference paper

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