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Leach AS, Hack J, Amboage M, Diaz-Moreno S, Huang H, Cullen PL, Wilding M, Magliocca E, Miller TS, Howard CA, Brett DJL, Shearing PR, McMillan PF, Russell AE, Jervis R. A novel fuel cell design for operandoenergy-dispersive x-ray absorption measurements. J Phys Condens Matter 2021; 33:314002. [PMID: 34030140 DOI: 10.1088/1361-648x/ac0476] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
A polymer electrolyte fuel cell has been designed to allowoperandox-ray absorption spectroscopy (XAS) measurements of catalysts. The cell has been developed to operate under standard fuel cell conditions, with elevated temperatures and humidification of the gas-phase reactants, both of which greatly impact the catalyst utilisation. X-ray windows in the endplates of the cell facilitate collection of XAS spectra during fuel cell operation while maintaining good compression in the area of measurement. Results of polarisation curves and cyclic voltammograms showed that theoperandocell performs well as a fuel cell, while also providing XAS data of suitable quality for robust XANES analysis. The cell has produced comparable XAS results when performing a cyclic voltammogram to an establishedin situcell when measuring the Pt LIII edge. Similar trends of Pt oxidation, and reduction of the formed Pt oxide, have been presented with a time resolution of 5 s for each spectrum, paving the way for time-resolved spectral measurements of fuel cell catalysts in a fully-operating fuel cell.
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Affiliation(s)
- A S Leach
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
| | - J Hack
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
| | - M Amboage
- Diamond Light Source, Didcot, Oxon, OX11 0DE, United Kingdom
| | - S Diaz-Moreno
- Diamond Light Source, Didcot, Oxon, OX11 0DE, United Kingdom
| | - H Huang
- School of Chemistry, University of Southampton, University Road, Southampton SO17 1BJ, United Kingdom
| | - P L Cullen
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
- School of Engineering and Materials Science (SEMS) and Material Research Institute, Queen Mary University of London, London, E1 4NS, United Kingdom
| | - M Wilding
- UK Catalysis Hub, Research Complex at Harwell, Harwell Campus, OX11 0FA, United Kingdom
| | - E Magliocca
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
| | - T S Miller
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
| | - C A Howard
- Department of Physics & Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - D J L Brett
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
| | - P R Shearing
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
| | - P F McMillan
- Department of Chemistry, Christopher Ingold Laboratory, University College London, 20 Gordon St., London WC1H 0AJ, United Kingdom
| | - A E Russell
- School of Chemistry, University of Southampton, University Road, Southampton SO17 1BJ, United Kingdom
| | - R Jervis
- Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London WC1E 7JE, United Kingdom
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Miller TS, Jorge AB, Suter TM, Sella A, Corà F, McMillan PF. Carbon nitrides: synthesis and characterization of a new class of functional materials. Phys Chem Chem Phys 2017; 19:15613-15638. [DOI: 10.1039/c7cp02711g] [Citation(s) in RCA: 247] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We examine the characterization of carbon nitrides and provide a perspective on their functional properties as next-generation materials.
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Affiliation(s)
- T. S. Miller
- Department of Chemistry
- Christopher Ingold Building
- University College London
- London
- UK
| | - A. Belen Jorge
- Materials Research Institute
- School of Engineering and Materials Science
- Queen Mary University of London
- London
- UK
| | - T. M. Suter
- Department of Chemistry
- Christopher Ingold Building
- University College London
- London
- UK
| | - A. Sella
- Department of Chemistry
- Christopher Ingold Building
- University College London
- London
- UK
| | - F. Corà
- Department of Chemistry
- Christopher Ingold Building
- University College London
- London
- UK
| | - P. F. McMillan
- Department of Chemistry
- Christopher Ingold Building
- University College London
- London
- UK
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Abstract
The high pressure behavior of TaON was studied using a combination of Raman scattering, synchrotron X-ray diffraction, and X-ray absorption spectroscopy in diamond anvil cells to 70 GPa at ambient temperature. A Birch-Murnaghan equation of state fit for baddeleyite structured β-TaON indicates a high bulk modulus value Ko = 328 ± 4 GPa with K = 4.3. EXAFS analysis of the high pressure XAS data provides additional information on changes in the Ta-(O,N) and Ta-Ta distances. Changes in the X-ray diffraction patterns and Raman spectra indicate onset of a pressure induced phase transition near 33 GPa. Our analysis indicates that the new phase has an orthorhombic cotunnite-type structure but that the phase transition may not be complete even by 70 GPa. Similar sluggish transformation kinetics are observed for the isostructural ZrO2 phase. Analysis of compressibility data for the new cotunnite-type TaON phase indicate a very high bulk modulus Ko ∼ 370 GPa, close to the theoretically predicted value.
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Affiliation(s)
- K Woodhead
- Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK.
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Quesada-Cabrera R, Filinchuk Y, McMillan PF, Nies E, Dmitriev V, Meersman F. Exploring the pressure–temperature behaviour of crystalline and plastic crystalline phases of N-isopropylpropionamide. CrystEngComm 2015. [DOI: 10.1039/c5ce00032g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The phase behaviour of crystalline and plastic crystalline phases of N-(isopropyl)propionamide (NiPPA) has been investigated by X-ray diffraction and a tentative P,T diagram has been constructed.
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Affiliation(s)
- R. Quesada-Cabrera
- Christopher-Ingold Laboratories
- Department of Chemistry
- University College London
- London, UK
| | - Y. Filinchuk
- Institute of Condensed Matter and Nanosciences (IMCN)
- Université Catholique de Louvain
- B-1348 Louvain-la-Neuve, Belgium
| | - P. F. McMillan
- Christopher-Ingold Laboratories
- Department of Chemistry
- University College London
- London, UK
| | - E. Nies
- Division of Molecular and Nanomaterials
- Department of Chemistry
- Katholieke Universiteit Leuven
- Leuven, Belgium
| | - V. Dmitriev
- Swiss-Norwegian Beam Lines
- European Synchrotron Radiation Facilities
- F-38043 Grenoble Cedex, France
| | - F. Meersman
- Christopher-Ingold Laboratories
- Department of Chemistry
- University College London
- London, UK
- Biomolecular & Analytical Mass Spectrometry group
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Tobaldi DM, Pullar RC, Gualtieri AF, Belen Jorge A, Binions R, McMillan PF, Seabra MP, Labrincha JA. Influence of sol counter-ions on the anatase-to-rutile phase transformation and microstructure of nanocrystalline TiO2. CrystEngComm 2015. [DOI: 10.1039/c4ce02494j] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (titania, TiO2) being widely used for various applications, such as light-to-energy conversion and storage, and photocatalysis.
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Affiliation(s)
- D. M. Tobaldi
- Department of Materials and Ceramic Engineering/CICECO
- University of Aveiro
- 3810-193 Aveiro, Portugal
| | - R. C. Pullar
- Department of Materials and Ceramic Engineering/CICECO
- University of Aveiro
- 3810-193 Aveiro, Portugal
| | - A. F. Gualtieri
- Dipartimento di Scienze Chimiche e Geologiche
- Università degli studi di Modena e Reggio Emilia
- I-41121 Modena, Italy
| | - A. Belen Jorge
- Department of Chemistry
- University College London
- London, UK
| | - R. Binions
- School of Engineering and Materials Science
- Queen Mary University of London
- London E1 4NS, UK
| | - P. F. McMillan
- Department of Chemistry
- University College London
- London, UK
| | - M. P. Seabra
- Department of Materials and Ceramic Engineering/CICECO
- University of Aveiro
- 3810-193 Aveiro, Portugal
| | - J. A. Labrincha
- Department of Materials and Ceramic Engineering/CICECO
- University of Aveiro
- 3810-193 Aveiro, Portugal
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Tobaldi DM, Pullar RC, Binions R, Belen Jorge A, McMillan PF, Saeli M, Seabra MP, Labrincha JA. Influence of sol counter-ions on the visible light induced photocatalytic behaviour of TiO2 nanoparticles. Catal Sci Technol 2014. [DOI: 10.1039/c4cy00423j] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Titanium dioxide (TiO2) nanoparticles are attracting increasing interest because of their superior photocatalytic and antibacterial properties.
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Affiliation(s)
- D. M. Tobaldi
- Department of Materials and Ceramic Engineering
- CICECO
- University of Aveiro
- Campus Universitário de Santiago
- 3810-193 Aveiro, Portugal
| | - R. C. Pullar
- Department of Materials and Ceramic Engineering
- CICECO
- University of Aveiro
- Campus Universitário de Santiago
- 3810-193 Aveiro, Portugal
| | - R. Binions
- School of Engineering and Materials Science
- Queen Mary University of London
- London E1 4NS, UK
| | - A. Belen Jorge
- Christopher Ingold Building
- Department of Chemistry
- University College of London
- London, UK
| | - P. F. McMillan
- Christopher Ingold Building
- Department of Chemistry
- University College of London
- London, UK
| | - M. Saeli
- Dipartimento di Architettura (D'ARCH)
- Scuola Politecnica
- Università degli Studi di Palermo
- Viale delle Scienze
- Palermo, Italy
| | - M. P. Seabra
- Department of Materials and Ceramic Engineering
- CICECO
- University of Aveiro
- Campus Universitário de Santiago
- 3810-193 Aveiro, Portugal
| | - J. A. Labrincha
- Department of Materials and Ceramic Engineering
- CICECO
- University of Aveiro
- Campus Universitário de Santiago
- 3810-193 Aveiro, Portugal
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Hubert H, Garvie LAJ, Leinenweber K, Buseck PR, Petuskeyt WT, McMillan PF. High-Pressure, High-Temperature Synthesis of Superhard Boron Suboxide. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-410-191] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTA multianvil device was used to investigate the formation of BxO phases produced in the 2 to 10 GPa pressure range with temperatures between 1000 and 1800 °C.Amorphous and crystalline B and BP were oxidized using B2O3 and CrO3. Using powder X-ray diffraction and parallel electron energy-loss spectroscopy (PEELS), we were unable to detect graphitic or diamondstructured B2O, reported in previous studies. The refractory boride B6O, which has the α-rhombohedral boron structure, is the dominant suboxide in the P and T range of our investigation. PEELS with a transmission electron microscope was used to characterize the boron oxides.
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Dzivenko DA, Horvath-Bordon E, Zerr A, Miehe G, Kroll P, Boehler R, McMillan PF, Riedel R. High-pressure high-temperature synthesis of novel binary and ternary nitride phases of group 4 and 14 elements. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/121/6/062003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Wlodarczyk A, McMillan PF, Greenfield SA. Voltage sensitive dye imaging of transient neuronal assemblies in brain slices under hyperbaric conditions. Undersea Hyperb Med 2008; 35:35-40. [PMID: 18351125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have developed a high pressure optical cell to study large-scale transient neuronal coalitions--"assemblies" using voltage sensitive dye (VSD) fluorescence combined with fast CCD imaging of brain slices under hyperbaric conditions. The new cell has been tested at pressures up to P = 150-200 atm, corresponding to the range over which effects such as "pressure-reversal" of anaesthesia have been described previously. Brain slices were maintained in a flow of artificial cerebrospinal fluid (aCSF) and hyperbaric conditions were controlled to within +/- 0.2 atm using a back-pressure regulator placed in the pumping system. Preliminary VSD imaging experiments were carried out on rat hippocampal slices at pressures up to P approximately 50 atm. An electrode placed in the CA3 region was used to stimulate a signal along the Schaffer collateral towards CA1. First results indicate that good VSD data can be obtained that can be analysed to provide a new view on how hydrostatic pressurisation affects the dynamic propagation of neuronal assemblies.
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Affiliation(s)
- A Wlodarczyk
- Department of Chemistry and Materials Chemistry Centre, Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ, UK
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Wilding MC, Wilson M, McMillan PF. X-ray and neutron diffraction studies and MD simulation of atomic configurations in polyamorphic Y2O3-Al2O3 systems. Philos Trans A Math Phys Eng Sci 2005; 363:589-607. [PMID: 15664901 DOI: 10.1098/rsta.2004.1510] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Supercooled liquids in the Y(2)O(3)-Al(2)O(3) system undergo a liquid-liquid phase transition between a high-temperature, high-density amorphous (HDA) polymorph form and one with lower density (LDA form) that is stable at lower temperature. The two amorphous polymorphs have the same chemical composition, but they differ in their density (ca. 4% difference) and in their heat content (enthalpy) and entropy determined by calorimetry. Here we present new results of structural studies using neutron and high-energy X-ray diffraction to study the structural differences between HDA and LDA polyamorphs. The combined datasets show no large differences in the average nearest-neighbour Al-O or Y-O bond lengths or coordination numbers between the low- and high-density liquids. However, the data indicate that substantial changes occur among the packing geometries and clustering of the Al-O and Y-O coordination polyhedra, i.e. within the second-nearest-neighbour shell defined by the metal-metal (i.e. Y-Y, Y-Al, Al-Al) interactions. Polarizable ion model molecular dynamics simulations of Y(2)O(3)-Al(2)O(3) liquids are used to help interpret the pair-correlation functions obtained from X-ray and neutron scattering data. Unexpectedly large density fluctuations are observed to occur during the simulation of nominally equilibrated systems. These are interpreted as being due to dynamic sampling of high- and low-density configurations within the single-phase liquid at temperatures above the critical point or phase transition line. Calculated partial radial distribution functions indicate that the primary differences between HDA and LDA configurations occur among the Y-Y correlations.
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Affiliation(s)
- M C Wilding
- Department of Geology and McClellan Nuclear Radiation Center, University of California at Davis, Davis, CA 95616, USA
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Sato RK, McMillan PF, Dennison P, Dupree R. High-resolution aluminum-27 and silicon-29 MAS NMR investigation of silica-alumina glasses. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100164a057] [Citation(s) in RCA: 117] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Deb SK, Wilding M, Somayazulu M, McMillan PF. Pressure-induced amorphization and an amorphous-amorphous transition in densified porous silicon. Nature 2001; 414:528-30. [PMID: 11734849 DOI: 10.1038/35107036] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Crystalline and amorphous forms of silicon are the principal materials used for solid-state electronics and photovoltaics technologies. Silicon is therefore a well-studied material, although new structures and properties are still being discovered. Compression of bulk silicon, which is tetrahedrally coordinated at atmospheric pressure, results in a transition to octahedrally coordinated metallic phases. In compressed nanocrystalline Si particles, the initial diamond structure persists to higher pressure than for bulk material, before transforming to high-density crystals. Here we report compression experiments on films of porous Si, which contains nanometre-sized domains of diamond-structured material. At pressures larger than 10 GPa we observed pressure-induced amorphization. Furthermore, we find from Raman spectroscopy measurements that the high-density amorphous form obtained by this process transforms to low-density amorphous silicon upon decompression. This amorphous-amorphous transition is remarkably similar to that reported previously for water, which suggests an underlying transition between a high-density and a low-density liquid phase in supercooled Si (refs 10, 14, 15). The Si melting temperature decreases with increasing pressure, and the crystalline semiconductor melts to a metallic liquid with average coordination approximately 5 (ref. 16).
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Affiliation(s)
- S K Deb
- Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India
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Somayazulu M, Madduri A, Goncharov AF, Tschauner O, McMillan PF, Mao HK, Hemley RJ. Novel broken symmetry phase from N(2)O at high pressures and high temperatures. Phys Rev Lett 2001; 87:135504. [PMID: 11580605 DOI: 10.1103/physrevlett.87.135504] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2001] [Indexed: 05/23/2023]
Abstract
Simple molecular solids become unstable at high pressures, typically transforming to dense framework and/or metallic structures. We report formation of an unusual ionic solid NO(+)NO(3)(-) (nitrosonium nitrate) from N(2)O at pressures above 20 GPa and temperatures above 1000 K. Synchrotron x-ray diffraction indicates that the compound crystallizes with a structure related to the aragonite form of CaCO(3) and NaNO(3). Raman and infrared spectroscopic data indicate that the structure is noncentrosymmetric and exhibits a strong pressure dependent charge transfer and orientational order.
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Affiliation(s)
- M Somayazulu
- Geophysical Laboratory and Center for High Pressure Research, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, D.C. 20015, USA
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Zhang Z, Leinenweber K, Bauer M, Garvie LA, McMillan PF, Wolf GH. High-pressure bulk synthesis of crystalline C(6)N(9)H(3).HCl: a novel c(3)n(4) graphitic derivative. J Am Chem Soc 2001; 123:7788-96. [PMID: 11493052 DOI: 10.1021/ja0103849] [Citation(s) in RCA: 228] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A novel carbon nitride compound, structurally related to the proposed graphitic phase of C(3)N(4), has been synthesized in a bulk well-crystallized form. The new material, with stoichiometry C(6)N(9)H(4)Cl, was prepared through a solid-state reaction of 2,4,6-triamino-1,3,5-triazine with 2,4,6-trichloro-1,3,5-triazine at 1.0-1.5 GPa and 500-550 degrees C and also through a self-reaction of 2-amino-4,6-dichloro-1,3,5-triazine at similar conditions. X-ray and electron diffraction measurements on the yellowish compound indicate a hexagonal space group (P6(3)/m) with cell parameters of a = 8.4379(10) A and c = 6.4296(2) A. This new compound possesses a two-dimensional C(6)N(9)H(3) framework that is structurally related to the hypothetical P6m2 graphitic phase of C(3)N(4), but with an ordered arrangement of C(3)N(3) voids. The large voids in the graphene sheets are occupied by chloride ions with an equivalent number of nitrogen atoms on the framework protonated for charge balance. The composition of the sample was determined by bulk chemical analysis and confirmed by electron energy loss (EELS) spectroscopy. The chemical and structural model is consistent with bulk density measurements and with the infrared and (13)C NMR spectra. This work represents the first bulk synthesis of a well-characterized and highly crystalline material containing a continuous network of alternating carbon and nitrogen atoms.
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Affiliation(s)
- Z Zhang
- Materials Research Science and Engineering Center, Arizona State University, Tempe, Arizona 85287, USA
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Gerald Pacalo RE, Leinenweber KD, McMillan PF. Crystal structure of high-pressure PNNH. Acta Crystallogr A 1996. [DOI: 10.1107/s0108767396078130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Kingma KJ, Gerald Pacalo RE, McMillan PF. High-pressure behavior of silica and its analogs. Acta Crystallogr A 1996. [DOI: 10.1107/s0108767396078245] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Affiliation(s)
- J. L. Yarger
- J. L. Yarger, K. H. Smith, R. A. Nieman, Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA
| | - K. H. Smith
- J. L. Yarger, K. H. Smith, R. A. Nieman, Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA
| | - R. A. Nieman
- J. L. Yarger, K. H. Smith, R. A. Nieman, Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA
| | - J. Diefenbacher
- J. Diefenbacher, G. H. Wolf, P. F. McMillan, Material Research Group in High-Pressure Synthesis, Arizona State University, Tempe AZ 85287, USA
| | - G. H. Wolf
- J. Diefenbacher, G. H. Wolf, P. F. McMillan, Material Research Group in High-Pressure Synthesis, Arizona State University, Tempe AZ 85287, USA
| | - B. T. Poe
- B. T. Poe, Bayerisches Geoinstitut, Universitat Bayreuth, Bayreuth, Germany D-95440
| | - P. F. McMillan
- J. Diefenbacher, G. H. Wolf, P. F. McMillan, Material Research Group in High-Pressure Synthesis, Arizona State University, Tempe AZ 85287, USA
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Grumbach MP, Sankey OF, McMillan PF. Properties of B2O: An unsymmetrical analog of carbon. Phys Rev B Condens Matter 1995; 52:15807-15811. [PMID: 9980955 DOI: 10.1103/physrevb.52.15807] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Gillet P, Badro J, Varrel B, McMillan PF. High-pressure behavior in alpha -AlPO4: Amorphization and the memory-glass effect. Phys Rev B Condens Matter 1995; 51:11262-11269. [PMID: 9977851 DOI: 10.1103/physrevb.51.11262] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Abstract
Stishovite, the highest pressure polymorph of silicon dioxide, may be an important mineral in some regions of the Earth's mantle. Fourier transform infrared spectroscopy has been used to determine the hydrogen content of synthetic stishovite. The concentration of hydrogen depends on the aluminum content of the sample and reaches a maximum of 549 +/- 23 hydrogen atoms per 10(6) silicon atoms for an Al(2)O(3) content of 1.51 percent by weight. Stishovite could be a storage site for water in deep subducting slabs and in regions of the mantle that are too hot for hydrous minerals to be stable.
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Poe BT, McMillan PF, Coté B, Massiot D, Coutures JP. Magnesium and Calcium Aluminate Liquids: In Situ High-Temperature
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Al NMR Spectroscopy. Science 1993; 259:786-8. [PMID: 17809340 DOI: 10.1126/science.259.5096.786] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The use of high-temperature nuclear magnetic resonance (NMR) spectroscopy provides a means of investigating the structure of refractory aluminate liquids at temperatures up to 2500 K. Time-averaged structural information indicates that the average aluminum coordination for magnesium aluminate (MgAl(2)O(4)) liquid is slightly greater than for calcium aluminate (CaAl(2)O(4)) liquid and that in both liquids it is close to four. Ion dynamics simulations for these liquids suggest the presence of four-, five-, and six-coordinated aluminate species, in agreement with NMR experiments on fast-quenched glasses. These species undergo rapid chemical exchange in the high-temperature liquids, which is evidenced by a single Lorentzian NMR line.
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