80 results on '"Martin O. Jones"'
Search Results
2. Heterolytic Scission of Hydrogen Within a Crystalline Frustrated Lewis Pair
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Luke L. Daemen, Bojana Ginovska, Anibal J. Ramirez-Cuesta, Abhijeet J. Karkamkar, Madison B. Martinez, Timo Repo, Mark E. Bowden, Konstantin Chernichenko, Martin O. Jones, Seth A. Miller, Tom Autrey, Gregory K. Schenter, Noemi Leick, and Department of Chemistry
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Hydrogen ,116 Chemical sciences ,Ab initio ,chemistry.chemical_element ,Crystal structure ,010402 general chemistry ,FE ,01 natural sciences ,Heterolysis ,Frustrated Lewis pair ,ACTIVATION ,Inorganic Chemistry ,Crystal ,DESIGN ,Physical and Theoretical Chemistry ,Bond cleavage ,H-2 ,010405 organic chemistry ,CATALYTIC-HYDROGENATION ,REACTIVITY ,0104 chemical sciences ,Crystallography ,chemistry ,biological sciences ,CO2 ,COMPLEXES ,C6F5 ,Single crystal - Abstract
We report the heterolysis of molecular hydrogen under ambient conditions by the crystalline frustrated Lewis pair (FLP) 1-{2-[bis (pentafluorophenyOboryl] phenyl -2, 2,6,6-tetrame-thylpiperidine (KCAT). The gas-solid reaction provides an approach to prepare the solvent-free, polycrystalline ion pair KCATH2 through a single crystal to single crystal transformation. The crystal lattice of KCATH2 increases in size relative to the parent KCAT by approximately 2%. Microscopy was used to follow the transformation of the highly colored red/orange KCAT to the colorless KCATH2 over a period of 2 h at 300 K under a flow of H-2 gas. There is no evidence of crystal decrepitation during hydrogen uptake. Inelastic neutron scattering employed over a temperature range from 4-200 K did not provide evidence for the formation of polarized H-2 in a precursor complex within the crystal at low temperatures and high pressures. However, at 300 K, the INS spectrum of KCAT transformed to the INS spectrum of KCATH2. Calculations suggest that the driving force is more favorable in the solid state compared to the solution or gas phase, but the addition of H-2 into the KCAT crystal is unfavorable. Ab Initio methods were used to calculate the INS spectra of KCAT, KCATH2, and a possible precursor complex of H-2 in the pocket between the B and N of crystalline KCAT. Ex-situ NMR showed that the transformation from KCAT to KCATH2 is quantitative and our results suggest that the hydrogen heterolysis process occurs via H-2 diffusion into the FLP crystal with a rate-limiting movement of H-2 from inactive positions to reactive sites.
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- 2020
3. Resurrecting the metabolome: Rapid evolution magnifies the metabolomic plasticity to predation in a natural Daphnia population
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Chao Zhang, Luc De Meester, Lynn Govaert, Robby Stoks, Martin O. Jones, and Mark R. Viant
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0106 biological sciences ,0301 basic medicine ,Population ,Daphnia magna ,010603 evolutionary biology ,01 natural sciences ,Daphnia ,Predation ,03 medical and health sciences ,Metabolomics ,Genetics ,Metabolome ,Animals ,Humans ,education ,Ecology, Evolution, Behavior and Systematics ,education.field_of_study ,biology ,biology.organism_classification ,Adaptation, Physiological ,030104 developmental biology ,Phenotype ,Natural population growth ,Evolutionary biology ,Predatory Behavior ,Adaptation - Abstract
Populations rely on already present plastic responses (ancestral plasticity) and evolution (including both evolution of mean trait values, constitutive evolution, and evolution of plasticity) to adapt to novel environmental conditions. Because of the lack of evidence from natural populations, controversy remains regarding the interplay between ancestral plasticity and rapid evolution in driving responses to new stressors. We addressed this topic at the level of the metabolome utilizing a resurrected natural population of the water flea Daphnia magna that underwent a human-caused increase followed by a reduction in predation pressure within ~16 years. Predation risk induced plastic changes in the metabolome which were mainly related to shifts in amino acid and sugar metabolism, suggesting predation risk affected protein and sugar utilization to increase energy supply. Both the constitutive and plastic components of the metabolic profiles showed rapid, probably adaptive evolution whereby ancestral plasticity and evolution contributed nearly equally to the total changes of the metabolomes. The subpopulation that experienced the strongest fish predation pressure and showed the strongest phenotypic response, also showed the strongest metabolomic response to fish kairomones, both in terms of the number of responsive metabolites and in the amplitude of the multivariate metabolomic reaction norm. More importantly, the metabolites with higher ancestral plasticity showed stronger evolution of plasticity when predation pressure increased, while this pattern reversed when predation pressure relaxed. Our results therefore highlight that the evolution in response to a novel pressure in a natural population magnified the metabolomic plasticity to this stressor.
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- 2021
4. 2021 roadmap for sodium-ion batteries
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John T. S. Irvine, Emma Kendrick, Valerie R. Seymour, Aamod V. Desai, Edmund J. Cussen, Peter Gross, Andrew J. Naylor, Maria-Magdalena Titirici, Jake M. Brittain, Rebecca Boston, Ruth Sayers, Stewart A. M. Dickson, Sudeshna Sen, Sara I. R. Costa, Zhuangnan Li, Ashish Rudola, Heather Au, Dominic S. Wright, Nuria Tapia-Ruiz, Yongseok Choi, Hande Alptekin, John M. Griffin, Martin O. Jones, Marco Amores, Shahin Nikman, Eun Jeong Kim, A. Robert Armstrong, Reza Younesi, Maria Crespo Ribadeneyra, Laure Monconduit, William I. F. David, Christopher I Thomas, Patrik Johansson, Serena A. Cussen, Grant S. Stone, Jincheng Tong, Russell E. Morris, Clare P. Grey, Alexandre Ponrouch, Oleg Kolosov, Emmanuel I. Eweka, Darren M. C. Ould, Robert G. Palgrave, Thomas J. Wood, Yue Chen, Jerry Barker, Ronnie Mogensen, Stijn F. L. Mertens, Philippe Poizot, Juan Forero-Saboya, David O. Scanlon, Manish Chhowalla, Lorenzo Stievano, Emily M. Reynolds, Xiao Hua, Moulay Tahar Sougrati, William R. Brant, Martin Karlsmo, Stéven Renault, Christopher A. O’Keefe, Begoña Silván, Lancaster University, Harwell Science and Innovation Campus, Imperial College London, University of Sheffield [Sheffield], Faradion Limited, University of Virginia [Charlottesville], University of Oxford [Oxford], University of Cambridge [UK] (CAM), University College of London [London] (UCL), University of St Andrews [Scotland], AUTRES, Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Chalmers University of Technology [Gothenburg, Sweden], Science and Technology Facilities Council (STFC), University of Birmingham [Birmingham], Uppsala University, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Université Montpellier 1 (UM1)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut de Chimie du CNRS (INC), Réseau sur le stockage électrochimique de l'énergie (RS2E), Université de Picardie Jules Verne (UPJV)-Institut de Chimie du CNRS (INC)-Aix Marseille Université (AMU)-Université de Pau et des Pays de l'Adour (UPPA)-Université de Nantes (UN)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM), Institut des Matériaux Jean Rouxel (IMN), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Ecole Polytechnique de l'Université de Nantes (EPUN), Université de Nantes (UN)-Université de Nantes (UN), Alistore, European Commission, Swedish Research Council, Swedish Energy Agency, Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, Ministerio de Economía, Industria y Competitividad (España), Faraday Institution, Austrian Science Fund, Innovate UK, Tapia-Ruiz, Nuria [0000-0002-5005-7043], Armstrong, A Robert [0000-0003-1937-0936], Alptekin, Hande [0000-0001-6065-0513], Au, Heather [0000-0002-1652-2204], Barker, Jerry [0000-0002-8791-1119], Brant, William R [0000-0002-8658-8938], Choi, Yong-Seok [0000-0002-3737-2989], Costa, Sara I R [0000-0001-8105-207X], Crespo Ribadeneyra, Maria [0000-0001-6455-4430], Cussen, Serena A [0000-0002-9303-4220], Desai, Aamod V [0000-0001-7219-3428], Forero-Saboya, Juan D [0000-0002-3403-6066], Griffin, John M [0000-0002-8943-3835], Irvine, John T S [0000-0002-8394-3359], Johansson, Patrik [0000-0002-9907-117X], Karlsmo, Martin [0000-0002-0437-6860], Kendrick, Emma [0000-0002-4219-964X], Kolosov, Oleg V [0000-0003-3278-9643], Mertens, Stijn F L [0000-0002-5715-0486], Monconduit, Laure [0000-0003-3698-856X], Naylor, Andrew J [0000-0001-5641-7778], Poizot, Philippe [0000-0003-1865-4902], Renault, Stéven [0000-0002-6500-0015], Rudola, Ashish [0000-0001-9368-0698], Sayers, Ruth [0000-0003-1289-0998], Seymour, Valerie R [0000-0003-3333-5512], Silván, Begoña [0000-0002-1273-3098], Sougrati, Moulay Tahar [0000-0003-3740-2807], Stievano, Lorenzo [0000-0001-8548-0231], Thomas, Chris I [0000-0001-8090-4541], Titirici, Maria-Magdalena [0000-0003-0773-2100], Tong, Jincheng [0000-0001-7762-1460], Wood, Thomas J [0000-0002-5893-5664], Younesi, Reza [0000-0003-2538-8104], Apollo - University of Cambridge Repository, Kim, Eunjeong [0000-0002-2941-068], Kim, Eunjeong [0000-0002-2941-0682], University of Virginia, University of Oxford, Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM), Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes (UN)-Aix Marseille Université (AMU)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Collège de France (CdF (institution))-Université de Picardie Jules Verne (UPJV)-Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Pau et des Pays de l'Adour (UPPA)-Institut de Chimie du CNRS (INC)-Université de Montpellier (UM)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Université Grenoble Alpes (UGA), Université de Nantes (UN)-Université de Nantes (UN)-Ecole Polytechnique de l'Université de Nantes (EPUN), Université de Nantes (UN)-Université de Nantes (UN)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Tapia-Ruiz, N [0000-0002-5005-7043], Armstrong, AR [0000-0003-1937-0936], Alptekin, H [0000-0001-6065-0513], Au, H [0000-0002-1652-2204], Barker, J [0000-0002-8791-1119], Brant, WR [0000-0002-8658-8938], Choi, YS [0000-0002-3737-2989], Costa, SIR [0000-0001-8105-207X], Ribadeneyra, MC [0000-0001-6455-4430], Cussen, SA [0000-0002-9303-4220], Desai, AV [0000-0001-7219-3428], Forero-Saboya, JD [0000-0002-3403-6066], Griffin, JM [0000-0002-8943-3835], Irvine, JTS [0000-0002-8394-3359], Johansson, P [0000-0002-9907-117X], Karlsmo, M [0000-0002-0437-6860], Kendrick, E [0000-0002-4219-964X], Kolosov, OV [0000-0003-3278-9643], Mertens, SFL [0000-0002-5715-0486], Monconduit, L [0000-0003-3698-856X], Naylor, AJ [0000-0001-5641-7778], Poizot, P [0000-0003-1865-4902], Renault, S [0000-0002-6500-0015], Rudola, A [0000-0001-9368-0698], Sayers, R [0000-0003-1289-0998], Seymour, VR [0000-0003-3333-5512], Silván, B [0000-0002-1273-3098], Sougrati, MT [0000-0003-3740-2807], Stievano, L [0000-0001-8548-0231], Thomas, CI [0000-0001-8090-4541], Titirici, MM [0000-0003-0773-2100], Tong, J [0000-0001-7762-1460], Wood, TJ [0000-0002-5893-5664], Younesi, R [0000-0003-2538-8104], The Faraday Institution, University of St Andrews. School of Chemistry, University of St Andrews. Centre for Energy Ethics, University of St Andrews. Centre for Designer Quantum Materials, and University of St Andrews. EaSTCHEM
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Chemical process ,Technology ,Computer science ,PAIR DISTRIBUTION FUNCTION ,HIGH-ENERGY DENSITY ,ELECTROCHEMICAL PROPERTIES ,Materialkemi ,02 engineering and technology ,01 natural sciences ,7. Clean energy ,Materials Chemistry ,QD ,LITHIUM-ION ,Energy demand ,Scope (project management) ,anodes ,NA2TI3O7 NANOSHEETS ,[CHIM.MATE]Chemical Sciences/Material chemistry ,sodium ion ,021001 nanoscience & nanotechnology ,Variety (cybernetics) ,General Energy ,Roadmap ,T-DAS ,Lithium ,0210 nano-technology ,Battery (electricity) ,energy materials ,Energy & Fuels ,HIGH-CAPACITY ANODE ,batteries ,Materials Science (miscellaneous) ,Materials Science ,chemistry.chemical_element ,Materials Science, Multidisciplinary ,electrolytes ,010402 general chemistry ,Energy storage ,MECHANISTIC INSIGHTS ,SDG 7 - Affordable and Clean Energy ,STRUCTURAL EVOLUTION ,SOLID-ELECTROLYTE INTERPHASE ,Science & Technology ,QD Chemistry ,0104 chemical sciences ,chemistry ,13. Climate action ,Sustainability ,HIGH-PERFORMANCE CATHODE ,Biochemical engineering ,cathodes - Abstract
Tapia-Ruiz, Nuria et al., Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid–electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology., The authors gratefully acknowledge RS2E and Alistore-ERI for funding their research into Na-ion batteries. The funding received from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 646433 (NAIADES), the Swedish Research Council, the Swedish Energy Agency (#37671-1), and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS), are all gratefully acknowledged. The many fruitful discussions within ALISTORE-ERI, and especially with M Rosa Palacín, have been most valuable. P J is also grateful for the continuous support from several of the Chalmers Areas of Advance: Materials Science and Energy. Funding from the European Union’s innovation program H2020 is acknowledged: H2020-MSCA-COFUND-2016 (DOC-FAM, Grant Agreement No. 754397). A Ponrouch is grateful to the Spanish Ministry for Economy, Industry and Competitiveness Severo Ochoa Programme for Centres of Excellence in R&D (SEV-2015-0496).
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- 2021
5. Badger - an accessible genome exploration environment.
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Ben Elsworth, Martin O. Jones, and Mark L. Blaxter
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- 2013
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6. afterParty: turning raw transcriptomes into permanent resources.
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Martin O. Jones and Mark L. Blaxter
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- 2013
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7. iPhy: an integrated phylogenetic workbench for supermatrix analyses.
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Martin O. Jones, Georgios D. Koutsovoulos, and Mark L. Blaxter
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- 2011
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8. TaxMan: a taxonomic database manager.
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Martin O. Jones and Mark L. Blaxter
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- 2006
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9. Demonstrating hydrogen production from ammonia using lithium imide – Powering a small proton exchange membrane fuel cell
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Joshua W. Makepeace, William I. F. David, Thomas J. Wood, O. Simon Mylius, Jamie B. Nutter, Mark G. Kibble, Martin O. Jones, and Hazel M. A. Hunter
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Hydrogen ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Proton exchange membrane fuel cell ,Lithium imide ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Hydrogen purifier ,Nitrogen ,0104 chemical sciences ,chemistry.chemical_compound ,Ammonia ,Hydrogen storage ,chemistry ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,Hydrogen production - Abstract
Accessing the intrinsic hydrogen content within ammonia, NH3, has the potential to play a very significant role in the future of a CO2-free sustainable energy supply. Inexpensive light metal imides and amides are effective at decomposing ammonia to hydrogen and nitrogen (2NH3 → 3H2 + N2), at modest temperatures, and thus represent a low-cost approach to on-demand hydrogen production. Building upon this discovery, this paper describes the integration of an ammonia cracking unit with a post-reactor gas purification system and a small-scale PEM fuel cell to create a first bench-top demonstrator for the production of hydrogen using light metal imides.
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- 2017
10. Ball-milled Si powder for the production of H2 from water for fuel cell applications
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Jingping Hu, Lang Xu, John S. Foord, Peter P. Edwards, Sobia Ashraf, Emina Hadzifejzovic, and Martin O. Jones
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Inert ,Materials science ,Hydrogen ,Renewable Energy, Sustainability and the Environment ,05 social sciences ,Metallurgy ,Oxide ,Energy Engineering and Power Technology ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Chemical reaction ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Chemical engineering ,Tap water ,Hydrogen fuel ,0502 economics and business ,050207 economics ,0210 nano-technology ,Ball mill ,Dissolution - Abstract
The development of a safe technique for the supply of hydrogen to small portable fuel cells has emerged as a significant barrier to their deployment in recent years, with solutions centering on the use of hydrogen absorption materials, or the generation of hydrogen through chemical reaction. In the present work we demonstrate that the ball-milling of Si under inert conditions in the presence of KOH and sucrose results in the formation of a fine Si-based powder which reacts spontaneously with water at ambient starting temperature to evolve hydrogen rapidly at high yield. Embedded KOH is capable of accelerating the hydrolysis reaction of silicon by the self-heating effect attributed to dissolution heat of KOH, obviating the need for external heating to initiate the reaction; it also reduces the sensitivity of the reaction to oxide contamination of the Si surface by enabling its dissolution in the form of soluble silicates. Moreover, the silicon–water reaction can be switched on and off by adjusting the ambient temperature. It is shown that ball-milled, KOH-embedded Si powder is able to react with different water sources, such as tap water, river water, and salt water, to produce H2 under aerobic conditions. The method represents a cheap scalable approach for the safe provision of hydrogen fuel to small fuel cells.
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- 2017
11. Simultaneous neutron diffraction and microwave dielectric characterisation of ammine materials - a non-destructive, non-contact characterisation tool for determining ammonia content in solids
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Adrian Porch, Jon Hartley, and Martin O. Jones
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010302 applied physics ,Diffraction ,Mass flow ,Neutron diffraction ,Analytical chemistry ,General Physics and Astronomy ,Halide ,02 engineering and technology ,Dielectric ,021001 nanoscience & nanotechnology ,Mass spectrometry ,01 natural sciences ,Ammonia ,chemistry.chemical_compound ,chemistry ,Deuterium ,0103 physical sciences ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
We have investigated ammonia adsorption in group two halides (MgI2 and CaBr2) using custom-built apparatus that permits simultaneous neutron diffraction, microwave dielectric characterisation and out-gas mass spectroscopy of solid state materials during ammonia adsorption. Deuterated ammonia was flowed over the sample and the uptake – as measured by mass flow meters, mass spectroscopy and structure – compared with the change in dielectric constant. An excellent correlation between ammonia content and dielectric property was observed and, when linked to diffraction, mass flow and mass spectroscopy data, could be used to determine the amount of ammonia present within the solid. The combination of these techniques could also be used to differentiate physisorbed and metal-coordinated ammonia and explain subtleties in the observed structural transformations.
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- 2016
12. Basic materials physics of transparent conducting oxides
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David Vernon Morgan, Richard Marc Perks, Martin O. Jones, Adrian Porch, and Peter P. Edwards
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Inorganic Chemistry ,Materials science ,business.industry ,Doping ,Optical transparency ,Nanotechnology ,Conductivity ,Solar energy ,business ,Material physics ,Flat panel - Abstract
Materials displaying the remarkable combination of high electrical conductivity and optical transparency already from the basis of many important technological applications, including flat panel displays, solar energy capture and other opto-electronic devices. Here we present the basic materials physics of these important materials centred on the nature of the doping process to generate n-type conductivity in transparent conducting oxides, the associated transition to the metallic (conducting) state and the detailed properties of the degenerate itinerant electron gas. The aim is to fully understand the origins of the basic performance limits of known materials and to set the scene for new or improved materials which will breach those limits for new-generation transparent conducting materials, either oxides, or beyond oxides.
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- 2016
13. Neutron scattering and hydrogen storage
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Anibal J. Ramirez-Cuesta, Martin O. Jones, and William I. F. David
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Hydrogen ,Scattering ,Mechanical Engineering ,Nuclear engineering ,Radiochemistry ,chemistry.chemical_element ,Neutron scattering ,Condensed Matter Physics ,Hydrogen storage ,Materials Science(all) ,chemistry ,Mechanics of Materials ,Clean energy ,General Materials Science ,Neutron ,Physics::Atomic Physics - Abstract
Hydrogen has been identified as a fuel of choice for providing clean energy for transport and other applications across the world and the development of materials to store hydrogen efficiently and safely is crucial to this endeavour. Hydrogen has the largest scattering interaction with neutrons of all the elements in the periodic table making neutron scattering ideal for studying hydrogen storage materials. Simultaneous characterisation of the structure and dynamics of these materials during hydrogen uptake is straightforward using neutron scattering techniques. These studies will help us to understand the fundamental properties of hydrogen storage in realistic conditions and hence design new hydrogen storage materials. © 2009 Elsevier Ltd. All rights reserved.
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- 2016
14. A Solution Selection Model for Coaxial Electrospinning and Its Application to Nanostructured Hydrogen Storage Materials
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D. W. K. Jenkins, Neal T. Skipper, Kate R. Ryan, William I. F. David, Stephen M. Bennington, Arthur Lovell, Zeynep Kurban, and Martin O. Jones
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Chemistry ,Ammonia borane ,Nanotechnology ,Electrospinning ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Hildebrand solubility parameter ,chemistry.chemical_compound ,Hydrogen storage ,General Energy ,Chemical engineering ,Polystyrene ,Fiber ,Physical and Theoretical Chemistry ,Coaxial ,Porosity - Abstract
Coaxial electrospinning was used to encapsulate the complex hydride ammonia borane in polystyrene to improve its properties as a hydrogen storage material. A solvent selection system was developed by using the Hansen solubility parameters to facilitate the choice of compatible solvents for core and shell. This enabled systematic optimization of the parameters needed for successful coelectrospinning. This approach has general application for any multiphase electrospinning system, including ones where the core is highly conducting or nonpolymeric. The resulting fiber morphologies depend strongly on the degree of miscibility of core and shell solutions. Fibers spun from immiscible core-shell solutions had a classic coaxial structure. Fibers produced from semimiscible core-shell solutions were highly porous, with inclusions extending through the fiber and an ordered radial and longitudinal distribution of nanoscale pores on the fiber surface. We suggest that this type of porosity may be due to an instability created in the nonaxisymmetric modes at the core-shell interface, resulting in intrusion of the core into the shell polymer. These controllably porous structures have numerous potential applications including materials templating or drug delivery. In the porous fibers, the temperature of the first hydrogen release of ammonia borane is reduced to 85 °C. This result suggests a nanostructured hydride, but a large mass loss indicates that much of the ammonia borane is expelled on heating. The coaxial fibers, in contrast, appear to encapsulate the hydride successfully. The coaxial and porous fibers alike showed no significant release of borazine, suggesting two different suppression mechanisms for this impurity. © 2010 American Chemical Society.
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- 2016
15. Unusual reactivity of visible-light-responsive AgBr-BiOBr heterojunction photocatalysts
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Peter P. Edwards, Rebecca J. Nicholls, Tiancun Xiao, Liang Kong, Martin O. Jones, Henry H. Lai, and Zheng Jiang
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business.industry ,Energy conversion efficiency ,Light irradiation ,Heterojunction ,Photochemistry ,Catalysis ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Rhodamine B ,Photocatalysis ,Optoelectronics ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,business ,Visible spectrum - Abstract
AgBr-BiOBr heterojunction photocatalysts with varying loadings of AgBr (0.5 wt%) lead to isolated AgBr species and reduced photocatalytic activity. Among such catalysts, the AgBr (0.2 wt%)-BiOBr exhibits the highest visible-light-responsive photoactivity, which can decolorize Rhodamine B within 30 min. However, these AgBr-BiOBr materials gradually lost their photoactivity in the cycling photocatalytic tests. Possible mechanisms for both the enhanced photocatalytic activity and deactivation of the AgBr-BiOBr heterojunctions were proposed on basis of theoretical speculation and experimental observations. © 2012 Elsevier Inc. All rights reserved.
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- 2016
16. Stepwise phase transition in the formation of lithium amidoborane
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Hailiang Chu, Ping Chen, Peter P. Edwards, Chengzhang Wu, Guotao Wu, Martin O. Jones, Zhitao Xiong, Kate R. Ryan, and William I. F. David
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Phase transition ,Hydride ,Inorganic chemistry ,Ammonia borane ,Thermal decomposition ,Crystal structure ,Lithium ,Phase Transition ,Inorganic Chemistry ,chemistry.chemical_compound ,chemistry ,Ammonia ,Lithium hydride ,Organometallic Compounds ,Physical and Theoretical Chemistry ,Boranes ,Lithium amidoborane - Abstract
A stepwise phase transition in the formation of lithium amidoborane via the solid-state reaction of lithium hydride and ammonia borane has been identified and investigated. Structural analyses reveal that a lithium amidoborane-ammonia borane complex (LiNH(2)BH(3).NH(3)BH(3)) and two allotropes of lithium amidoborane (denoted as alpha- and beta-LiNH(2)BH(3), both of which adopt orthorhombic symmetry) were formed in the process of synthesis. LiNH(2)BH(3).NH(3)BH(3) is the intermediate of the synthesis and adopts a monoclinic structure that features layered LiNH(2)BH(3) and NH(3)BH(3) molecules and contains both ionic and dihydrogen bonds. Unlike alpha-LiNH(2)BH(3), the units of the beta phase have two distinct Li(+) and [NH(2)BH(3)](-) environments. beta-LiNH(2)BH(3) can only be observed in energetic ball milling and transforms to alpha-LiNH(2)BH(3) upon extended milling. Both allotropes of LiNH(2)BH(3) exhibit similar thermal decomposition behavior, with 10.8 wt % H(2) released when heated to 180 degrees C; in contrast, LiNH(2)BH(3).NH(3)BH(3) releases approximately 14.3 wt % H(2) under the same conditions.
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- 2016
17. Rapid synthesis of colossal magnetoresistance manganites by microwave dielectric heating
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Stephen J. Blundell, Kay E. Gibbons, Amalia I. Mihut, Peter P. Edwards, Martin O. Jones, Yuzuru Miyazaki, Adrian Porch, Neil C. Hyatt, and Ian Gameson
- Subjects
Colossal magnetoresistance ,Materials science ,Condensed matter physics ,Metals and Alloys ,Valency ,General Chemistry ,Catalysis ,Metal nitrate ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Oxidizing agent ,Dielectric heating ,Materials Chemistry ,Ceramics and Composites ,Microwave - Abstract
Colossal magnetoresistance manganites have been synthesised by the microwave dielectric heating of metal nitrates, which act both as effective microwave susceptors, and a ready source of oxidizing NO2 to induce mixed valency.
- Published
- 2016
18. Synthesis, structure, and magnetic characterization of pulsed laser-ablated superconducting La2CuO4Fx thin films
- Author
-
S. T. Lees, M. Slaski, Martin O. Jones, Peter P. Edwards, and Ian Gameson
- Subjects
Superconductivity ,Crystallinity ,Materials science ,Annealing (metallurgy) ,General Chemical Engineering ,Transition temperature ,Materials Chemistry ,Analytical chemistry ,Disproportionation ,General Chemistry ,Crystal structure ,Thin film ,Magnetic susceptibility - Abstract
High quality, c-axis oriented thin films of semiconducting La{sub 2}CuO{sub 4} have been fabricated by pulsed laser-ablation deposition. Superconducting properties have been successfully induced in the films by a postdeposition, ex-situ static annealing process in a F{sub 2}/N{sub 2} gas mixture. The influence of the fluorination temperature on the structural, magnetic, and electronic properties of the resulting thin films has been examined in detail. X-ray data reveal that facile fluorination of the films proceeds via a complex, multistage process, often yielding to distinct La{sub 2}CuO{sub 4}-type phases. This phase segregation suggests a disproportionation process following fluorine uptake. Such a disproportionation is subtly different from that found for oxygen excess La{sub 2}CuO{sub 4} in that for La{sub 2}CuO{sub 4+{delta}} the parent O{sub 4} and an oxygen rich (O{sub 4+{delta}}) phase are formed, but in the present system two fluorinated (i.e., oxidized) phases are formed. La{sub 2}CuO{sub 4} thin films fluorinated at a temperature of 150 C possess the highest values for both T{sub c} (onset) (ca. 38.5 K) and critical current density (>10{sup 6} A cm{sup {minus}2} at 4.2 K in zero magnetic field). Magnetic susceptibility data demonstrate that this fluorination methodology is of sufficient sensitivity to allow the controlled hole-dopingmore » of semiconducting La{sub 2}CuO{sub 4} thin films through to the high-temperature superconducting regime.« less
- Published
- 2016
19. Induction of superconductivity in pulsed laser ablated La2CuO4 thin films by post-deposition fluorination
- Author
-
S. T. Lees, Ian Gameson, M. Slaski, Martin O. Jones, Peter P. Edwards, P. Woodall, Colin Greaves, F. Wellhofer, and I. Langford
- Subjects
Pulsed laser ,Superconductivity ,Diffraction ,Materials science ,Condensed matter physics ,Annealing (metallurgy) ,Transition temperature ,Energy Engineering and Power Technology ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Magnetization ,Critical current ,Electrical and Electronic Engineering ,Thin film - Abstract
Pulsed laser ablation has been used to fabricate La2CuO4 thin films. Superconducting properties have been successfully induced in the films by an ex-situ, post-ablation annealing process in F2 gas resulting in a Tc (onset) of 36 K. The presence of two slightly different c-axis expanded phases in the X-ray diffraction data of the fluorinated films implies a degree of inhomogeneity in F2 uptake. Critical current densities (Jc) and the irreversibility line have been established from hysteresis cycles. A Jc of ∼ 106 A cm−2 for a typical film was observed at 10 K in zero field.
- Published
- 2016
20. High-capacity hydrogen storage in lithium and sodium amidoboranes
- Author
-
William I. F. David, Ping Chen, Chaw-Keong Yong, Peter P. Edwards, Tom Autrey, Guotao Wu, Simon R. Johnson, Wendy J. Shaw, Abhi Karkamkar, Zhitao Xiong, and Martin O. Jones
- Subjects
Hydrogen purity ,Hydrogen ,Hydride ,Mechanical Engineering ,Sodium ,Inorganic chemistry ,Ammonia borane ,chemistry.chemical_element ,General Chemistry ,Condensed Matter Physics ,chemistry.chemical_compound ,Hydrogen storage ,chemistry ,Mechanics of Materials ,Borazine ,General Materials Science ,Lithium - Abstract
The safe and efficient storage of hydrogen is widely recognized as one of the key technological challenges in the transition towards a hydrogen-based energy economy. Whereas hydrogen for transportation applications is currently stored using cryogenics or high pressure, there is substantial research and development activity in the use of novel condensed-phase hydride materials. However, the multiple-target criteria accepted as necessary for the successful implementation of such stores have not yet been met by any single material. Ammonia borane, NH3BH3, is one of a number of condensed-phase compounds that have received significant attention because of its reported release of approximately 12 wt% hydrogen at moderate temperatures (approximately 150 degrees C). However, the hydrogen purity suffers from the release of trace quantities of borazine. Here, we report that the related alkali-metal amidoboranes, LiNH2BH3 and NaNH2BH3, release approximately 10.9 wt% and approximately 7.5 wt% hydrogen, respectively, at significantly lower temperatures (approximately 90 degrees C) with no borazine emission. The low-temperature release of a large amount of hydrogen is significant and provides the potential to fulfil many of the principal criteria required for an on-board hydrogen store.
- Published
- 2016
21. Understanding Vibrational Anharmonicity and Phonon Dispersion in Solid Ammonia Borane
- Author
-
Bill David, Philippe C. Aeberhard, Christopher J. Mundy, Tom Autrey, Martin O. Jones, Shawn M. Kathmann, Gregory K. Schenter, and Timmy Ramirez-Cuesta
- Subjects
Hydrogen ,Phonon ,Ammonia borane ,Anharmonicity ,chemistry.chemical_element ,Boranes ,Neutron scattering ,Molecular physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,General Energy ,chemistry ,Deuterium ,Physics::Atomic and Molecular Clusters ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Atomic physics ,Dispersion (chemistry) ,Astrophysics::Galaxy Astrophysics - Abstract
We compute the hydrogen vibrational spectra for bulk ammonia borane (NH 3BH 3), for both protonated and deuterated cases, using harmonic and anharmonic methodologies as well as low frequency coupling and quantifying dispersive effects to understand their influence on the resulting spectra. Even at 10 K the accounting of anharmonic effects on the incoherent inelastic neutron scattering (IINS) signal is more significant than approximations introduced by sampling and interpolating a finite simulation cell to capture dispersion effects. We compare our computed anharmonic spectrum with IINS measurements and find excellent agreement. © 2012 American Chemical Society.
- Published
- 2016
22. Synthesis of micro-crystals of transparent cobalt aluminate, shrouded in siliceous material, from Co(II)-exchanged zeolite X
- Author
-
Peter P. Edwards, Martin O. Jones, Ian Gameson, Paul A. Anderson, and Matthew T. J. Lodge
- Subjects
Ion exchange ,Chemistry ,Spinel ,Inorganic chemistry ,Composite number ,chemistry.chemical_element ,engineering.material ,Inorganic Chemistry ,Micro crystals ,Cobalt aluminate ,Materials Chemistry ,engineering ,Crystallite ,Physical and Theoretical Chemistry ,Zeolite ,Cobalt - Abstract
We report an investigation of the synthesis of a cobalt aluminate spinel composite from the heat-induced collapse of cobalt ion-exchanged sodium zeolite X. The work presented here adds to earlier studies by illustrating that by careful control of synthesis and reaction conditions, both the phase composition and crystallite size of the spinel can be controlled. The spinel crystallites grow within siliceous materials formed by the collapse of the zeolite framework, with the crystalline particles being completly shrouded by the siliceous matrix. © 2005 Elsevier Ltd. All rights reserved.
- Published
- 2016
23. Highly conductive In4Sn3O12 films prepared by pulsed laser deposition
- Author
-
David H. O’Neil, Martin O. Jones, Vladimir L. Kuznetsov, Peter P. Edwards, and Robert M. J. Jacobs
- Subjects
Crystallinity ,Laser ablation ,Materials science ,chemistry ,Torr ,Analytical chemistry ,chemistry.chemical_element ,Surface finish ,Deposition (chemistry) ,Oxygen ,Transparent conducting film ,Pulsed laser deposition - Abstract
Highly conductive (> 103 Ω-1cm-1) and transparent (∼ 90%) In4Sn3O12 films have been deposited using pulsed laser deposition (PLD) on glass substrates held at a temperature of 500°C under varying pressures of oxygen (2.5 mTorr ≤ PO2 ≤ 15 mTorr). The crystallinity and the roughness of the films were found to increase with the pressure of oxygen used during deposition. Electron concentrations of the order of 5×1020 cm-3 and mobilities as high as 30 cm2V-1s-1 were derived from the measurement of Hall coefficients. Both the electronic transport and optical properties of the films were found to be strongly sensitive to the pressure of oxygen used during deposition.
- Published
- 2016
24. FURTHER COPPER NMR-STUDIES OF THE ELECTRON SUPERCONDUCTOR ND2CUO3.7F0.3
- Author
-
G.P. Dai, Martin O. Jones, D.P. Tunstall, and Peter P. Edwards
- Subjects
Superconductivity ,Condensed matter physics ,Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Electron ,Normal state ,Condensed Matter Physics ,Copper ,Neodymium ,Tetragonal crystal system ,Condensed Matter::Superconductivity ,Materials Chemistry ,Perpendicular ,Hyperfine structure - Abstract
The temperature dependence of the magnetic shifts in the normal state of the anion-doped superconductor Nd2CuO3.7F0.3 are presented. The shifts due to the neodymium moments are subtracted off, to leave magnetic hyperfine shifts with a linear temperature dependence. In contrast to YBCO the temperature-dependent term in the shift for B applied parallel to the c-axis of the tetragonal crystal is about seven times larger than the shift when B is applied perpendicular to the c-axis.
- Published
- 2016
25. Microstructure of superconducting Hg0.5Cr0.5Sr2CuO4+delta thin films on SrTiO3
- Author
-
Ian P. Jones, J.S. Abell, Peter P. Edwards, Martin O. Jones, and G. Kong
- Subjects
Superconductivity ,Self-diffusion ,Materials science ,Annealing (metallurgy) ,Analytical chemistry ,Energy Engineering and Power Technology ,Condensed Matter Physics ,Epitaxy ,Microstructure ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,Transmission electron microscopy ,Electrical and Electronic Engineering ,Thin film - Abstract
Transmission electron microscopy has been used to characterise the microstructures of Sr2Cr0.5CuO2 precursor thin films and annealed Hg0.5Cr0.5Sr2CuO4+δ thin films on (0 0 1) SrTiO3 substrates. Precursor films consist essentially of amorphous Sr2CuO3 phase with SrCrxCuO2 grains embedded, while Hg0.5Cr0.5Sr2CuO4+δ films are epitaxial with the orientation relationship (0 0 1) Hg ∥(0 0 1) STO , [1 0 0] Hg ∥[1 0 0] STO . Hg and Cr diffuse through the whole film thickness. Some a-axis grains are present in the Hg0.5Cr0.5Sr2CuO4+δ films with much lower Hg and Cr contents.
- Published
- 2016
26. SYNTHESIS AND CHARACTERIZATION OF LASER-ABLATED YBA2-XSRXCU3O7 THIN-FILMS
- Author
-
A. Asab, P. Shaffery, S. Sutton, Peter R. Slater, Martin O. Jones, Colin Greaves, P. Woodall, Peter P. Edwards, Ian Gameson, and F. Wellhofer
- Subjects
Range (particle radiation) ,Materials science ,Laser ablation ,Analytical chemistry ,Energy Engineering and Power Technology ,Condensed Matter Physics ,Laser ,Oxide superconductors ,Electronic, Optical and Magnetic Materials ,law.invention ,law ,Electrical and Electronic Engineering ,Thin film ,Solubility ,Single phase - Abstract
A comparison of the Sr solubility limits in bulk YBa2Cu3O7 and thin film YBa2Cu3O7 has been made. Whereas for the former, single phase samples of YBa2−xSrxCu3O7 are only formed for 0≤x≤1.0 the thin films show a higher solubility range, 0≤x≤1.6. Both the c parameter and Tc decrease with increasing x, and the Sr content of the films has been confirmed by EDAX. These results demonstrate the potential of laser ablation for the synthesis of new and modified oxide superconductors.
- Published
- 2016
27. Growth of In(2)O(3)(100) on Y-stabilized ZrO(2)(100) by O-plasma assisted molecular beam epitaxy
- Author
-
A. Schertel, Peter P. Edwards, Peter J. Dobson, Russell G. Egdell, A. Bourlange, John S. Foord, David J. Payne, Martin O. Jones, and John L. Hutchison
- Subjects
Materials science ,Physics and Astronomy (miscellaneous) ,X-ray photoelectron spectroscopy ,Transmission electron microscopy ,Band gap ,Analytical chemistry ,Substrate (electronics) ,Thin film ,Epitaxy ,High-resolution transmission electron microscopy ,Molecular beam epitaxy - Abstract
Thin films of In2 O3 have been grown on Y-stabilized Zr O2 (100) by oxygen plasma assisted molecular beam epitaxy with a substrate temperature of 650 °C. Ordered epitaxial growth was confirmed by high resolution transmission electron microscopy. The position of the valence band onset in the x-ray photoemission spectra of the epitaxial films is found to be inconsistent with the widely quoted value of 3.75 eV for the fundamental bandgap of In2 O3 and suggests a revised value of 2.67 eV. © 2008 American Institute of Physics.
- Published
- 2016
28. An in-depth understanding of the bimetallic effects and coked carbon species on an active bimetallic Ni(Co)/Al2O3 dry reforming catalyst
- Author
-
Junqiu Guo, Yongxiang Zhao, Lina Chi, Martin O. Jones, Zheng Jiang, Xin Liao, Stewart F. Parker, Rihards Gerdts, and Martyn Hill
- Subjects
Materials science ,Carbon dioxide reforming ,Catalyst support ,Alloy ,Metallurgy ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Methane ,0104 chemical sciences ,Catalysis ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,Carbon ,Bimetallic strip ,Filamentous carbon - Abstract
Ni/Al2O3, Co/Al2O3 and bimetallic Ni(Co)/Al2O3 catalysts were prepared using an impregnation method and employed in CO2 dry reforming of methane under coking-favored conditions. The spent catalysts were carefully characterized using typical characterization technologies and inelastic neutron scattering spectroscopy. The bimetallic catalyst exhibited a superior activity and anti-coking performance compared to Ni/Al2O3, while the most resistant to coking behavior was Co/Al2O3. The enhanced activity of the Ni(Co)/Al2O3 bimetallic catalyst is attributed to the reduced particle size of metallic species and resistance to forming stable filamentous carbon. The overall carbon deposition on the spent bimetallic catalyst is comparable to that of the spent Ni/Al2O3 catalyst, whereas the carbon deposited on the bimetallic catalyst is mainly less-stable carbonaceous species as confirmed by SEM, TPO, Raman and INS characterization. This study provides an in depth understanding of alloy effects in catalysts, the chemical nature of coked carbon on spent Ni-based catalysts and, hopefully, inspires the creative design of a new bimetallic catalyst for dry reforming reactions.
- Published
- 2016
29. The hydrothermal synthesis of BiOBr flakes for visible-light-responsive photocatalytic degradation of methyl orange
- Author
-
Peter P. Edwards, Guidong Yang, Liang Kong, Zheng Jiang, Tiancun Xiao, Fan Yang, and Martin O. Jones
- Subjects
Chemistry ,Band gap ,General Chemical Engineering ,General Physics and Astronomy ,Mineralogy ,General Chemistry ,Photochemistry ,Hydrothermal circulation ,chemistry.chemical_compound ,Methyl orange ,Photocatalysis ,Hydrothermal synthesis ,Crystallite ,Photodegradation ,Visible spectrum - Abstract
Flake-like BiOBr semiconductors have been prepared using hydrothermal synthesis with meticulous control of synthesis parameters and used for photocatalytic degradation of methyl orange. XRD, SEM and UV-vis characterizations have been performed to study the obtained BiOBr materials. The results indicate that the morphology and crystallite size of BiOBr depend significantly on the temperature and duration of the hydrothermal syntheses. Diffuse UV-vis spectra show the BiOBr materials to be indirect semiconductors with an optical bandgap of approximately 2.92 eV, which is essentially unaffected by the synthesis parameters. The hydrothermal-synthesized BiOBr flakes exhibit noticeable activity for photodegradation of methyl orange under visible light (>400 nm) illumination, with the BiOBr synthesized by hydrothermal treatment at 120 degrees C for 6 h exhibiting superior photocatalytic performance in these flakes. The excellent activity and photo-stability reveal that BiOBr is a promising visible-light-responsive photocatalyst. (C) 2010 Elsevier B.V. All rights reserved.
- Published
- 2010
30. Catalytic combustion of methane over mixed oxides derived from Co–Mg/Al ternary hydrotalcites
- Author
-
Jie Cheng, Martin O. Jones, Zhengping Hao, Junjie Yu, Tiancun Xiao, Zheng Jiang, and Peter P. Edwards
- Subjects
Hydrotalcite ,Chemistry ,General Chemical Engineering ,Inorganic chemistry ,Oxide ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Catalytic combustion ,Methane ,law.invention ,Catalysis ,chemistry.chemical_compound ,Fuel Technology ,law ,Mixed oxide ,Calcination ,Cobalt - Abstract
Co(x)Mg(3-x)/Al composite oxides (xCoMAO-800) were prepared by calcination of Co(x)Mg(3-x)/Al hydrotalcites (x = 0.0, 0.5,1.0,1.5,2.0,2.5,3.0, respectively) at 800 degrees C. The materials were characterized using XRD, TG-DSC, N(2) adsorption-desorption and TPR. The methane catalytic combustion over the xCoMAO-800 was assessed in a fixed bed micro-reactor. The results revealed that cobalt can be homogenously dispersed into the matrices of the hydrotalcites and determines the structure, specific surface areas and porosity of the derived xCoMAO-800 oxide catalysts. The thermal stability and homogeneity of the hydrotalcites markedly depends on the cobalt concentration in the hydrotalcites. The Co-based hydrotalcite-derived oxides exhibit good activity in the catalytic combustion of methane. The catalytic activity over the xCoMAO-800 oxides enhances with increasing x up to 1.5, but subsequently decreases dramatically as cobalt loadings are further increased. The 1.5CoMAO-800 catalyst shows the best methane combustion activity, igniting methane at 450 degrees C and completing methane combustion around 600 degrees C. The catalytic combustion activity over the xCoMAO-800 oxides are closely related to the strong Co-Mg/Al interaction within the mixed oxides according to the TG-DSC, TPR and activity characteristics. (C) 2009 Elsevier B.V. All rights reserved.
- Published
- 2010
31. The Monoammoniate of Lithium Borohydride, Li(NH3)BH4: An Effective Ammonia Storage Compound
- Author
-
Martin O. Jones, William I. F. David, Francesca P. A. Fabbiani, Peter P. Edwards, Christina Y. Tang, Simon R. Johnson, Marco Sommariva, and David M. Royse
- Subjects
Hydrogen ,Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,General Chemistry ,Crystal structure ,Biochemistry ,Hydrogen storage ,Ammonia ,chemistry.chemical_compound ,chemistry ,Lithium borohydride ,X-ray crystallography ,Thermochemistry ,Anhydrous - Abstract
Lithium borohydride absorbs anhydrous ammonia to form four stable ammoniates; Li(NH(3))(n)BH(4), mono-, di-, tri-, and tertraammoniate. This paper focuses on the monoammoniate, Li(NH(3))BH(4), which is readily formed on exposure of LiBH(4) to ammonia at room temperature and pressure. Ammonia loss from Li(NH(3))BH(4) commences around 40 degrees C and the compound transforms directly to LiBH(4). The crystal structure of Li(NH(3))BH(4) is reported here for the first time. Its close structural relationship with LiBH(4) provides a clear insight into the facile nature and mechanism of ammonia uptake and loss. These materials not only represent an excellent high weight-percent ammonia system but are also potentially important hydrogen stores.
- Published
- 2009
32. Electron Spin Resonance Investigation of Hydrogen Absorption in Ball-Milled Graphite
- Author
-
P. P. Edwards, Hironobu Fuji, Yoshitsugu Kojima, Wataru Ishida, Hiroki Miyaoka, Martin O. Jones, Takayuki Ichikawa, Christopher I. Smith, and Jeffrey Harmer
- Subjects
Diffraction ,Materials science ,Hydrogen ,Infrared ,Analytical chemistry ,chemistry.chemical_element ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,symbols.namesake ,General Energy ,Fourier transform ,chemistry ,law ,Ball (bearing) ,symbols ,Graphite ,Physical and Theoretical Chemistry ,Hydrogen absorption ,Electron paramagnetic resonance - Abstract
Nanostructured hydrogenated graphite (CnanoHx) was synthesized here from graphite by ball-milling under a hydrogen (H2) atmosphere. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) show that ball milling results in the rupture of graphene sheets creating active defects and allowing hydrogen to be dissociated and then chemisorbed. Most likely small quantities of iron particles incorporated during the milling process act as a catalyst. C nanoHx thus possesses unique characteristic hydrogenated states present in nanometer scale particles, unlike standard hydride materials. Electron spin resonance (ESR) spectroscopy resolves two distinct paramagnetic components. The first is assigned to (intrinsic) delocalized π-electrons in the graphene sheets (g ~ 2.008) which disappears after approximately 32 h milling. The second ESR component grows in intensity with milling time and is assigned to localized electrons (g ~ 2.003) with a concentration of 3 × 1020 spins per gram after 80 h milling. HYSCORE spectroscopy reveals proton hyperfine couplings, and variable temperature CW ESR spectra demonstrate an unexpected magnetic ordering at low temperatures (~ 10 K). Formation of CnanoHx thus consists of weakly coupled localized electrons with wave functions that extends over small graphitic moieties. The radical centers do not physisorb a large quantity of H2 molecules under conditions required for practical H2 storage materials and are a product of the milling process and chemisorption of hydrogen. © 2009 American Chemical Society.
- Published
- 2009
33. Catalytic Partial Oxidation of Methane over Ni-Based Catalysts Derived from Ni−Mg/Al Ternary Hydrotalcites
- Author
-
Peter P. Edwards, Martin O. Jones, Jixin Su, Huahong Shi, Zheng Jiang, and Tiancun Xiao
- Subjects
inorganic chemicals ,chemistry.chemical_classification ,Hydrotalcite ,Base (chemistry) ,organic chemicals ,General Chemical Engineering ,Inorganic chemistry ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Catalysis ,Nickel ,Fuel Technology ,chemistry ,Desorption ,heterocyclic compounds ,Reactivity (chemistry) ,Partial oxidation ,Syngas - Abstract
Ni-based catalysts derived from Ni-Mg/Al ternary hydrotalcites with low Ni-loadings have been prepared for the partial oxidation of methane (POM) to syngas. The reducibility, surface basicity, and effects of catalyst reduction on POM reactivity over these catalysts have been explored. Temperature-programmed reduction and CO2-temperature-programmed desorption results indicate that the amount of Ni-loading and the Mg/Al molar ratio exert a remarkable influence on their reducibility but have little influence on the surface basicity, with an increase in Mg/Al ratio also lessening the base strength of the alkaline sites. Reaction temperature significantly affects the reactivity of the catalysts, and high temperature reduction of the catalysts can lead to superior reactivity to those reduced at low temperature. An in situ reduction of the catalyst has been observed in the POM reaction for catalysts reduced at low temperature. Under the optimized reaction conditions, the catalysts with Ni content from 8 wt % to 15.5 wt % show similar activity in POM reactions, and this activity is much higher than for catalysts with lower Ni-loading (̃4 wt %), which is explained in terms of nickel reducibility and the surface basicity of the catalysts. © 2009 American Chemical Society.
- Published
- 2009
34. Isotopic studies of the ammonia decomposition reaction mediated by sodium amide
- Author
-
Martin O. Jones, Hazel M. A. Hunter, Thomas J. Wood, Joshua W. Makepeace, and William I. F. David
- Subjects
inorganic chemicals ,Kinetics ,Inorganic chemistry ,General Physics and Astronomy ,Decomposition ,Catalysis ,Ammonia ,chemistry.chemical_compound ,chemistry ,Transition metal ,Sodium amide ,Kinetic isotope effect ,Physical and Theoretical Chemistry ,Chemical decomposition - Abstract
We demonstrate that the ammonia decomposition reaction catalysed by sodium amide proceeds under a different mechanism to ammonia decomposition over transition metal catalysts. Isotopic variants of ammonia and sodium amide reveal a significant kinetic isotope effect in contrast to the nickel-catalysed reaction where there is no such effect. The bulk composition of the catalyst is also shown to affect the kinetics of the ammonia decomposition reaction.
- Published
- 2015
35. Ammonia decomposition catalysis using non-stoichiometric lithium imide
- Author
-
Martin O. Jones, Thomas J. Wood, William I. F. David, Hazel M. A. Hunter, and Joshua W. Makepeace
- Subjects
Hydrogen ,Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Lithium imide ,General Chemistry ,Decomposition ,Catalysis ,chemistry.chemical_compound ,Ammonia ,Lithium ,Imide ,Stoichiometry - Abstract
The non-stoichiometric lithium imide–amide system effectively decomposes ammonia to its constituents, hydrogen and nitrogen. Isotopic studies show that this bulk catalytic reaction has the potential to generate high-purity hydrogen for future energy and transport applications., We demonstrate that non-stoichiometric lithium imide is a highly active catalyst for the production of high-purity hydrogen from ammonia, with superior ammonia decomposition activity to a number of other catalyst materials. Neutron powder diffraction measurements reveal that the catalyst deviates from pure imide stoichiometry under ammonia flow, with active catalytic behaviour observed across a range of stoichiometry values near the imide. These measurements also show that hydrogen from the ammonia is exchanged with, and incorporated into, the bulk catalyst material, in a significant departure from existing ammonia decomposition catalysts. The efficacy of the lithium imide–amide system not only represents a more promising catalyst system, but also broadens the range of candidates for amide-based ammonia decomposition to include those that form imides.
- Published
- 2015
36. Transparent current spreading layers for optoelectronic devices
- Author
-
Martin O. Jones, David Vernon Morgan, Adrian Porch, Peter P. Edwards, and Richard Marc Perks
- Subjects
Electron mobility ,Materials science ,business.industry ,General Physics and Astronomy ,Transparency (human–computer interaction) ,law.invention ,Electrical resistance and conductance ,law ,Transmission line ,Optoelectronics ,Figure of merit ,Current (fluid) ,business ,Layer (electronics) ,Light-emitting diode - Abstract
In this paper we develop a simple model based on a leaky transmission line to assess the electrical performance of transparent current spreading layers for application to surface light emitting diodes. Figures of merit suitable for device design are obtained and these are applied to a range of material systems reported in the literature. These calculations show that materials with electrical characteristics approaching ultimate performance limits can be achieved. Furthermore, calculations of the electromagnetic absorption of conducting layers show that further improvements should be possible by selecting materials with the highest possible majority carrier mobilities, which enable films of greater thickness to be grown while maintaining high transparency, leading to very low spreading layer resistances. Ways of achieving improved mobility are also discussed.
- Published
- 2004
37. Understanding composition-property relationships in Ti-Cr-V-Mo alloys for optimisation of hydrogen storage in pressurised tanks
- Author
-
Samantha K. Callear, Kazuya Kamazawa, Martin O. Jones, Towata Shinichi, Stewart F. Parker, Jun Sugiyama, William I. F. David, Mamoru Ishikiriyama, Tatsuo Noritake, and Anibal J. Ramirez-Cuesta
- Subjects
Phase transition ,Materials science ,Hydrogen ,Neutron diffraction ,Analytical chemistry ,General Physics and Astronomy ,chemistry.chemical_element ,Dissociation (chemistry) ,Inelastic neutron scattering ,Condensed Matter::Materials Science ,Hydrogen storage ,Tetragonal crystal system ,Crystallography ,chemistry ,Desorption ,Physical and Theoretical Chemistry ,Nuclear Experiment - Abstract
The location of hydrogen within Ti–Cr–V–Mo alloys has been investigated during hydrogen absorption and desorption using in situ neutron powder diffraction and inelastic neutron scattering. Neutron powder diffraction identifies a low hydrogen equilibration pressure body-centred tetragonal phase that undergoes a martensitic phase transition to a face-centred cubic phase at high hydrogen equilibration pressures. The average location of the hydrogen in each phase has been identified from the neutron powder diffraction data although inelastic neutron scattering combined with density functional theory calculations show that the local structure is more complex than it appears from the average structure. Furthermore the origin of the change in dissociation pressure and hydrogen trapping on cycling in Ti–Cr–V–Mo alloys is discussed.
- Published
- 2014
38. Hydrogen production from ammonia using sodium amide
- Author
-
Thomas J. Wood, Hazel M. A. Hunter, William I. F. David, James D. Taylor, Samantha K. Callear, Martin O. Jones, and Joshua W. Makepeace
- Subjects
Models, Molecular ,Chemistry ,Sodium ,Inorganic chemistry ,Temperature ,chemistry.chemical_element ,General Chemistry ,Biochemistry ,Decomposition ,Amides ,Catalysis ,Ruthenium ,Ammonia ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Transition metal ,Nickel ,Sodium amide ,Hydrogen production ,Hydrogen - Abstract
This paper presents a new type of process for the cracking of ammonia (NH3) that is an alternative to the use of rare or transition metal catalysts. Effecting the decomposition of NH3 using the concurrent stoichiometric decomposition and regeneration of sodium amide (NaNH2) via sodium metal (Na), this represents a significant departure in reaction mechanism compared with traditional surface catalysts. In variable-temperature NH3 decomposition experiments, using a simple flow reactor, the Na/NaNH2 system shows superior performance to supported nickel and ruthenium catalysts, reaching 99.2% decomposition efficiency with 0.5 g of NaNH2 in a 60 sccm NH3 flow at 530 °C. As an abundant and inexpensive material, the development of NaNH2-based NH3 cracking systems may promote the utilization of NH3 for sustainable energy storage purposes.
- Published
- 2014
39. In situ X-ray powder diffraction studies of hydrogen storage and release in the Li-N-H system
- Author
-
William I. F. David, Peter P. Edwards, Samantha K. Callear, Martin O. Jones, and Joshua W. Makepeace
- Subjects
Lithium amide ,Hydride ,Chemistry ,Annealing (metallurgy) ,Inorganic chemistry ,General Physics and Astronomy ,Lithium imide ,Hydrogen storage ,chemistry.chemical_compound ,Physical chemistry ,Dehydrogenation ,Physical and Theoretical Chemistry ,Powder diffraction ,Stoichiometry - Abstract
We report the experimental investigation of hydrogen storage and release in the lithium amide-lithium hydride composite (Li-N-H) system. Investigation of hydrogenation and dehydrogenation reactions of the system through in situ synchrotron X-ray powder diffraction experiments allowed for the observation of the formation and evolution of non-stoichiometric intermediate species of the form Li1+xNH2-x. This result is consistent with the proposed Frenkel-defect mechanism for these reactions. We observed capacity loss with decreasing temperature through decreased levels of lithium-rich (0.7 ≤ x ≤ 1.0) non-stoichiometric phases in the dehydrogenated material, but only minor changes due to multiple cycles at the same temperature. Annealing of dehydrogenated samples reveals the reduced stability of intermediate stoichiometry values (0.4 ≤ x ≤ 0.7) compared with the end member species: lithium amide (LiNH2) and lithium imide (Li2NH). Our results highlight the central role of ionic mobility in understanding temperature limitations, capacity loss and facile reversibility of the Li-N-H system.
- Published
- 2014
40. The structure and desorption properties of the ammines of the group II halides
- Author
-
Martin O. Jones, Peter P. Edwards, William I. F. David, and David M. Royse
- Subjects
Thermogravimetric analysis ,Lattice energy ,chemistry ,Magnesium ,Desorption ,Inorganic chemistry ,Group ii ,General Physics and Astronomy ,Halide ,Ionic bonding ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Ion - Abstract
The synthesis of the magnesium halide ammines (Mg(NH)Cl, Mg(NH)Br and Mg(NH)I) is reported and their structures are identified by high resolution X-ray diffraction. The structures of Mg(NH)Br and Mg(NH)I are reported for the first time. The desorption properties of Mg(NH)Cl, Mg(NH)Br and Mg(NH)I are examined by thermogravimetric analysis and NMR, and the trends in desorption properties as a function of composition are interpreted using a simple ionic model. It is found that the desorption properties are dependent on the lattice enthalpy of the intermediate and final phases Mg(NH)X, Mg(NH)X and MgX, that the anion has limited effect on the state of Mg-N bonding and that the desorption temperature of ionic ammines may be tuned by varying the size of the anion. © 2013 Elsevier B.V. All rights reserved.
- Published
- 2013
41. A Combined X-Ray and Neutron-Powder Diffraction Study of a Superstructure Derived from Tl0.75Sr1.8Ba0.2CuOy
- Author
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Martin O. Jones, Peter P. Edwards, Claude Michel, M. Hervieu, B. Raveau, and Ian Gameson
- Subjects
Strontium ,Chemistry ,Thermal decomposition ,Neutron diffraction ,chemistry.chemical_element ,Barium ,Crystal structure ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Inorganic Chemistry ,Crystal ,Crystallography ,Materials Chemistry ,Ceramics and Composites ,Cuprate ,Physical and Theoretical Chemistry ,Superstructure (condensed matter) - Abstract
We have observed a superstructure derived from the compound Tl0.75Sr1.8Ba0.2CuO(y). This compound arises from the 'collapse' of the parent oxynitrate compound TlSr2Ba2Cu2O7 (NO3) under controlled thermal decomposition. A combined X-ray and neutron powder diffraction study of the title compound indicates that the superstructure possesses the Pmmm space group, with unit cell parameters (derived from neutron diffraction data) of a = 3.7362(3) Å, b = 11.5449(9) Å, and c = 9.1494(8) Å. This superstructure takes the form of a three-fold repeat along the crystal b-axis produced through local distortions of the thallium and barium/strontium positions. This compound is nonsuperconducting due to the presence of a large number of vacancies in the electronically active copper-oxygen planes. (C) 2000 academic Press.
- Published
- 2000
42. Multielement NMR studies of the liquid-liquid phase separation and the metal-to-nonmetal transition in fluid lithium- and sodium-ammonia solutions
- Author
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Jeffrey Harmer, Martin O. Jones, Nicholas H. Rees, Neil Spencer, Kiminori Maeda, Patrick L. Cullen, Matthew T. J. Lodge, and Peter P. Edwards
- Subjects
Phase transition ,Analytical chemistry ,chemistry.chemical_element ,Electrolyte ,Electronic structure ,Surfaces, Coatings and Films ,Physics::Fluid Dynamics ,Metal ,chemistry ,Nonmetal ,visual_art ,Materials Chemistry ,Anhydrous ,visual_art.visual_art_medium ,Diamagnetism ,Lithium ,Physical and Theoretical Chemistry - Abstract
(1)H, (7)Li, (14)N, and (23)Na high resolution nuclear magnetic resonance (NMR) measurements are reported for fluid solutions of lithium and sodium in anhydrous liquid ammonia across the metal-to-nonmetal transition (MNM transition), paying particular attention to the phenomenon of liquid-liquid phase separation which occurs in the composition/temperature region close to the MNM transition. Our results are discussed in terms of the electronic structure of fluid metal-ammonia solutions at low temperatures (ca. 240 K). We find that the electronic phase transition to the metallic state in these solutions, especially at temperatures close to the liquid-liquid critical consolute temperature, occurs from a nonmetallic, electrolytic solution containing a predominance of electron spin-paired, (diamagnetic) charged bosonic states. The possible implications of these observations to the nature of the liquid-liquid phase separation are discussed, both from the views of N. F. Mott, regarding the MNM transition in sodium-ammonia solutions, and those of R. A. Ogg, regarding the possibility of high-temperature superconductivity in these solutions. Similarities between the electronic structure of metal-ammonia solutions and the high-temperature cuprate superconductors are also briefly emphasized.
- Published
- 2013
43. In-Operando Neutron Diffraction Studies of Transition Metal Hydrogen Storage Materials
- Author
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Jun Sugiyama, Martin O. Jones, Kazuya Kamazawa, Towata Shinichi, Kazutoshi Miwa, William I. F. David, Tatsuo Noritake, Mamoru Ishikiriyama, Samantha K. Callear, and Masakazu Aoki
- Subjects
Hydrogen storage ,Crystallography ,Materials science ,Transition metal ,Renewable Energy, Sustainability and the Environment ,Neutron diffraction ,Physical chemistry ,General Materials Science - Abstract
We thank ISIS for the time on GEM, Winfried Kockelmann for his assistance during data collection, the ISIS Sample Environment Section, and in particular Mark Kibble, for their help in facilitating the experiment, and Mr. Katsuhiko Hirose, Prof. Peter Edwards and Dr. Andrew Taylor for their support. © 2013 WILEY-VCH Verlag GmbH and Co.
- Published
- 2013
44. Surface and bulk reactions in borohydrides and amides
- Author
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Shin Ichi Orimo, Andreas Borgschulte, William I. F. David, Martin O. Jones, Shunsuke Kato, Elsa Callini, Andreas Züttel, and Benjamin Probst
- Subjects
Hydrogen ,Renewable Energy, Sustainability and the Environment ,Inorganic chemistry ,Ionic bonding ,chemistry.chemical_element ,Rate-determining step ,Borohydride ,Pollution ,Ion ,chemistry.chemical_compound ,Hydrogen storage ,Nuclear Energy and Engineering ,chemistry ,Environmental Chemistry ,Ionic conductivity ,Stoichiometry - Abstract
Complex hydrides such as LiBH4 and LiNH2 exceed the gravimetric hydrogen density of transition metal hydrides by one order of magnitude. However, hydrogen in complex hydrides is covalently bound and arranged in subunits e.g. [NH2]- and [BH4] - with a fixed stoichiometry. Along this line of thought, these compounds can be considered as ordinary ionic compounds. The corresponding pseudo-binary phase diagram comprises a great variety of phases with a high ionic mobility of Li-cations as well as pseudo-anions as measured by diffusion gradients. Using this equilibrium preparation method, we are able to discriminate between stable and meta-stable phases such as Li2BH 4NH2 formed during high-energy ball-milling. We identify Li2BH4NH2 as a mobile intermediate during phase formation. Hydrogen desorption as relevant for their potential use as hydrogen storage does not take place below 200°C as measured by gravimetry. In particular amides, but also borohydrides emit hydrogen, and nitrogen and boron, respectively, containing species (NH3 and BHx, respectively). We probe the bulk and surface exchange of hydrogen in such subunits in LiNH2 and Li2BH4NH2 by hydrogen-deuterium experiments. In contrast to bulk exchange, surface exchange processes occur at very low temperatures - lower than a significant decomposition rate but coincidentally with the appearance of Li2NH comprising high ionic conductivity. The rate limiting step is thus the bulk transport - in agreement with the empirical correlation that the mobility of ions is linked to the hydrogen desorption kinetics of a material (P. A. Anderson et al., Faraday Discuss., 2011, 151, 271-284). However, the bulk transport of ionic species competes with the diffusion of neutral species such as ammonia, being the origin of the unwanted emission of NH3. These results are discussed with respect to the ionic mobility of borohydride and amide materials. © 2012 The Royal Society of Chemistry.
- Published
- 2012
45. A multidisciplinary combinatorial approach for tuning promising hydrogen storage materials towards automotive applications
- Author
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Peter P. Edwards, S. D. Culligan, G. Purdy, Samuel Guerin, A. H. Pohl, William I. F. David, A. Amieiro-Fonseca, Simon R. Johnson, Samantha K. Callear, C. J. Nuttall, J.-Ph. Soulié, Martin O. Jones, Brian E. Hayden, and S. R. Ellis
- Subjects
Hydrogen storage ,Materials science ,business.industry ,Automotive industry ,Nanotechnology ,Physical and Theoretical Chemistry ,business ,Ternary operation ,Primary screening - Abstract
HyStorM is a multidisciplinary hydrogen-storage project aiming to synthesise and tune materials hydrogen storage properties for automotive applications. Firstly, unique high-throughput combinatorial thin-film technologies are used to screen materials' hydrogen storage properties. Then promising thin-film candidate compositions are synthesised and examined in the bulk. In this paper, we report on our results within the ternary compositions Mg-Ti-B and Ca-Ti-B. Primary screening of the Mg-Ti-B ternary identified a high capacity hotspot corresponding to Mg0.36Ti0.06B0.58, with 10.6 wt% H2 capacity. Partial reversibility has been observed for this material in the thin-film. Bulk Ti-doped Mg(BH4)2 composites show rehydrogenation to MgH2 under the conditions used. The synthesised thin-film Ca-Ti-B ternary showed only low hydrogen storage capacities. In the bulk, Ti-doping experiments on Ca(BH4)2 demonstrated reversible storage capacities up to 5.9 wt% H2. Further characterisation experiments are required to decipher the role of the Ti-dopant in these systems in both films and in the bulk.
- Published
- 2012
46. Copper nmr studies of the Nd2CuO4−xFx system
- Author
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G.P. Dai, Peter P. Edwards, D.P. Tunstall, B. Ctortecka, Ian Gameson, and Martin O. Jones
- Subjects
Diffraction ,NMR spectra database ,Nuclear magnetic resonance ,Chemistry ,Materials Chemistry ,Analytical chemistry ,chemistry.chemical_element ,Champ magnetique ,General Chemistry ,Condensed Matter Physics ,Nmr data ,Copper ,Magnetic field - Abstract
In this paper we present the orientation dependence of the copper nmr spectra in the Nd2CuO4−xFx system. The experiments were undertaken on both aligned and random powder samples. Initial nmr results indicated that the c-axis was aligned perpendicular to the magnetic field that was applied during the alignment process. This was subsequently confirmed by X-ray diffraction. The room temperature 63Cu nmr data was fitted using this distribution and this revealed that v Q was at most 6 MHz, Kax=0.15 ± 0.02%, Kiso=0.40 ± 0.05%. Once again, as in previous studies, we found that the indications on the degree of alignment obtained from X-ray measurements was substantially greater than the indications from the nmr data; X-ray measurements indicated nearly 100% alignment, nmr studies indicated 70% alignment. We speculate that the X-ray technique is not sensitive to large unaligned clumps in the samples as they are prepared.
- Published
- 1994
47. Nature of the band gap and origin of the conductivity of PbO2 revealed by theory and experiment
- Author
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Peter P. Edwards, Martin O. Jones, Russell G. Egdell, Aron Walsh, David O. Scanlon, Graeme W. Watson, Aoife B. Kehoe, David J. Payne, and William I. F. David
- Subjects
Condensed matter physics ,Band gap ,business.industry ,Neutron diffraction ,General Physics and Astronomy ,Nanotechnology ,Lead dioxide ,Electron ,Electronic structure ,Conductivity ,chemistry.chemical_compound ,Semiconductor ,chemistry ,Direct and indirect band gaps ,business - Abstract
Lead dioxide has been used for over a century in the lead-acid battery. Many fundamental questions concerning PbO(2) remain unanswered, principally: (i) is the bulk material a metal or a semiconductor, and (ii) what is the source of the high levels of conductivity? We calculate the electronic structure and defect physics of PbO(2), using a hybrid density functional, and show that it is an n-type semiconductor with a small indirect band gap of similar to 0.2 eV. The origin of electron carriers in the undoped material is found to be oxygen vacancies, which forms a donor state resonant in the conduction band. A dipole-forbidden band gap combined with a large carrier induced Moss-Burstein shift results in a large effective optical band gap. The model is supported by neutron diffraction, which reveals that the oxygen sublattice is only 98.4% occupied, thus confirming oxygen substoichiometry as the electron source.
- Published
- 2011
48. Variable temperature neutron diffraction studies of single crystals of LiND2
- Author
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Martin O. Jones, William I. F. David, Shigehito Isobe, Matthias J. Gutmann, Takayuki Ichikawa, Somei Ohnuki, Peter P. Edwards, and Yoshitsugu Kojima
- Subjects
Lithium amide ,Renewable Energy, Sustainability and the Environment ,Chemistry ,Single crystal ,Neutron diffraction ,Analytical chemistry ,Energy Engineering and Power Technology ,Hydrogen storage ,Condensed Matter Physics ,Thermal expansion ,Vibration ,Tetragonal crystal system ,Crystallography ,chemistry.chemical_compound ,Fuel Technology ,Lattice (order) ,Thermal - Abstract
We have synthesized a single crystal of lithium amide (LiNH2, LiND2) by melting method, and performed neutron diffraction of the single crystal at variable temperature. LiND2 is tetragonal structure and I-4 space group. Lattice parameters and unit cell volume of LiND 2 at room temperature, 50 °C, 100 °C, 150 °C and 200 °C were determined. Both of the lattice parameters and the unit cell volume increase with increase of temperature. From these results, we have estimated coefficient of volumetric thermal expansion αV of LiND 2 to be 222 × 10-6/K. With increase of temperature, all thermal ellipsoids gradually expand because of thermal vibration. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.
- Published
- 2011
49. Exceptional visible-light-driven photocatalytic activity over BiOBr-ZnFe2O4 heterojunctions
- Author
-
Zheng Jiang, Peter P. Edwards, Liang Kong, Lufeng Lu, Tiancun Xiao, and Martin O. Jones
- Subjects
Materials science ,Metals and Alloys ,Heterojunction ,General Chemistry ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Rhodamine ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,Materials Chemistry ,Ceramics and Composites ,Photocatalysis ,Degradation (geology) ,Visible spectrum - Abstract
An ultrasound-assisted, precipitation-deposition method has been developed to synthesise visible-light-responsive BiOBr-ZnFe(2)O(4) heterojunction photocatalysts. The heterojunctions with suitable BiOBr/ZnFe(2)O(4) ratios have a fascinating micro-spherical morphology and exhibit exceptional photocatalytic activity in visible-light degradation of Rhodamine B.
- Published
- 2011
50. Order and disorder in lithium tetrahydroborate
- Author
-
Samantha K. Callear, William I. F. David, Shin Ichi Orimo, Motoaki Matsuo, Peter P. Edwards, E. Anne Nickels, and Martin O. Jones
- Subjects
Materials science ,chemistry ,Mechanics of Materials ,Mechanical Engineering ,Solid mechanics ,Hexagonal phase ,Order and disorder ,Pair distribution function ,chemistry.chemical_element ,Thermodynamics ,General Materials Science ,Lithium ,Reactor pressure vessel - Published
- 2011
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