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Akinribide OJ, Obadele BA, Mekgwe GN, Ajibola OO, Akinwamide SO, Nomoto K, Ringer SP, Olubambi PA. Mechano-chemical synthesis and characterization of Ti (C, N)-powder from TiN-MWCNTs/graphite. Particulate Science and Technology 2019. [DOI: 10.1080/02726351.2019.1637625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- O. J. Akinribide
- Centre for Nanoengineering and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa
- Australian Centre for Microscopy and Microanalysis, School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, Sydney, Australia
| | - B. A. Obadele
- Centre for Nanoengineering and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa
- Department of Chemical, Materials and Metallurgical Engineering, Botswana International University of Science and Technology, Palapye, Botswana
| | - G. N. Mekgwe
- Centre for Nanoengineering and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa
| | - O. O. Ajibola
- Centre for Nanoengineering and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa
| | - S. O. Akinwamide
- Centre for Nanoengineering and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa
| | - K. Nomoto
- Australian Centre for Microscopy and Microanalysis, School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, Sydney, Australia
| | - S. P. Ringer
- Australian Centre for Microscopy and Microanalysis, School of Aerospace, Mechanical, Mechatronic Engineering, The University of Sydney, Sydney, Australia
| | - P. A. Olubambi
- Centre for Nanoengineering and Tribocorrosion, School of Mining, Metallurgy and Chemical Engineering, University of Johannesburg, Johannesburg, South Africa
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2
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Theska F, Ceguerra AV, Turk C, Breen AJ, Ringer SP, Primig S. Correlative study of lattice imperfections in long-range ordered, nano-scale domains in a Fe-Co-Mo alloy. Ultramicroscopy 2019; 204:91-100. [PMID: 31132736 DOI: 10.1016/j.ultramic.2019.05.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 04/29/2019] [Accepted: 05/12/2019] [Indexed: 10/26/2022]
Abstract
Recent advancements in data mining methods in atom probe microscopy have enabled new quantitative chemical and microstructural characterization beyond the standard three-dimensional reconstruction. For example, spatial distribution maps have been developed to enable visualisation of the local lattice occupation of a selected region of interest. However, the precision of such studies yet remains unknown as correlation with complementary methods would be required. Therefore, a correlative study of atom probe microscopy, neutron diffraction and microstructural modelling of long-range ordered, nano-scale domains in a well-researched Fe-Co-Mo Maraging-type steel is presented here. Its microstructure consists of Mo-enriched µ-phase (Fe,Co)7Mo6 particles embedded into a body-centred cubic FeCo matrix. Previous research has shown that under slow cooling conditions, this matrix partially decomposes into nano-scale B2 long-range ordered domains surrounded by disordered regions, resulting in reduced toughness in potential cutting applications. Usually, a long-range order parameter S referring to ideal B2 long-range order is assumed within such domains according to neutron diffraction. However, atom probe microscopy and modelling results presented in the current study indicate lattice imperfections with a partial substitution of atoms on the Fe- and Co-sublattices. After considering preferential retention effects during the atom probe experiment, a model unit cell is presented to define the observed imperfect B2 long-range order as pseudo-D03 long-range order, and the potential impact on the materials properties is discussed.
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Affiliation(s)
- F Theska
- School of Materials Science & Engineering, UNSW Sydney, NSW 2052, Australia
| | - A V Ceguerra
- Australian Centre for Microscopy & Microanalysis and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia
| | - C Turk
- Voestalpine Böhler Edelstahl GmbH & Co KG, Mariazellerstraße 25, 8605 Kapfenberg, Austria
| | - A J Breen
- Australian Centre for Microscopy & Microanalysis and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia; Department of Microstructure Physics and Alloy Design, Max-Planck-Institute for Iron Research, 40237 Düsseldorf, Germany
| | - S P Ringer
- Australian Centre for Microscopy & Microanalysis and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia
| | - S Primig
- School of Materials Science & Engineering, UNSW Sydney, NSW 2052, Australia.
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Khan MA, Bian P, Qu J, Chen H, Liu H, Foley M, Yao Y, Ringer SP, Zheng R. Non-destructive analysis on nano-textured surface of the vertical LED for light enhancement. Ultramicroscopy 2018; 196:1-9. [PMID: 30267990 DOI: 10.1016/j.ultramic.2018.09.003] [Citation(s) in RCA: 2] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 07/10/2018] [Accepted: 09/12/2018] [Indexed: 10/28/2022]
Abstract
In this work, the nano-textured surface of a GaN-based vertical light emitting diode (VLED) is characterized using a unified framework of non-destructive techniques (NDT) incorporating scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, Photoluminescence (PL), and X-ray diffraction (XRD) to optimize the light output efficiency. The surface roughness of ∼300 nm is revealed by AFM. Compressive stress-state of 0.667 GPa in the GaN surface is indicated by the E2(high) and A1(LO) phonon peak values at 569 cm-1 and 736 cm-1, respectively, in Raman spectrum and the wavelength at 442 nm rather 450 nm in PL spectrum. Without damaging the LED, surface analysis by NDT helps to advance the understanding of the optimized angular light redistribution subject to the high-roughness surface and the negative impacts of the stress induced at the top GaN layer, which leads to the optical efficiency degradation of the VLED. Furthermore, the impact of texturing on underneath n-GaN and MQWs layers is investigated via SEM-based transmission Kikuchi diffraction (TKD) and aberration-corrected scanning transmission electron microscopy (AC-STEM) and revealed a smooth surface morphology and good crystalline quality, indicating that the etch-induced damage by texture engineering does not impair the active region of the VLED. Accordingly, prospective optimizations are suggested in the context of surface engineering for light enhancement in VLEDs.
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Affiliation(s)
- Mansoor Ali Khan
- School of Physics, The University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia; Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia
| | - Pengju Bian
- School of Physics, The University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia; Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia
| | - Jiangtao Qu
- School of Physics, The University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia; Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia
| | - Hansheng Chen
- School of Physics, The University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia; Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia
| | - Hongwei Liu
- Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia
| | - Matthew Foley
- Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia
| | - Yin Yao
- Electron Microscope Unit, University of New South Wales, Sydney, NSW 2052, Australia
| | - S P Ringer
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, NSW 2006, Australia
| | - Rongkun Zheng
- School of Physics, The University of Sydney, Sydney, NSW 2006, Australia; The University of Sydney Nano Institute, The University of Sydney, Sydney, NSW 2006, Australia; Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia.
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4
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Abstract
The potential of C60 as a nucleic acid base (NAB) optical sensor is theoretically explored. We investigate the adsorption of four NABs, namely, adenine, cytosine, guanine, and thymine, on C60 in the gas phase. For the optimal NAB@C60 adsorption configurations, obtained using a dispersion-corrected density functional, we calculate the vis-near-ultraviolet optical response using time-dependent density functional theory. While the isolated C60 and NAB molecules do not exhibit visible optical excitation, we find that C60/NAB conjugation gives rise to distinct spectral features in the visible range. These results suggest that C60 conjugation can be applied for photodetection of individual NABs.
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Affiliation(s)
| | | | | | - C Stampfl
- School of Physics, The University of Sydney , Sydney, New South Wales 2006, Australia
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5
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Tawfik SA, Weston L, Cui XY, Ringer SP, Stampfl C. Near-Perfect Spin Filtering and Negative Differential Resistance in an Fe(II)S Complex. J Phys Chem Lett 2017; 8:2189-2194. [PMID: 28457138 DOI: 10.1021/acs.jpclett.7b00551] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Density functional theory and nonequilibrium Green's function calculations have been used to explore spin-resolved transport through the high-spin state of an iron(II)sulfur single molecular magnet. Our results show that this molecule exhibits near-perfect spin filtering, where the spin-filtering efficiency is above 99%, as well as significant negative differential resistance centered at a low bias voltage. The rise in the spin-up conductivity up to the bias voltage of 0.4 V is dominated by a conductive lowest unoccupied molecular orbital, and this is accompanied by a slight increase in the magnetic moment of the Fe atom. The subsequent drop in the spin-up conductivity is because the conductive channel moves to the highest occupied molecular orbital, which has a lower conductance contribution. This is accompanied by a drop in the magnetic moment of the Fe atom. These two exceptional properties, and the fact that the onset of negative differential resistance occurs at low bias voltage, suggests the potential of the molecule in nanoelectronic and nanospintronic applications.
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Affiliation(s)
| | - Leigh Weston
- Materials Department, University of California , Santa Barbara, California, United States
| | - X Y Cui
- Australian Centre for Microscopy and Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney , New South Wales, 2006, Australia
| | - S P Ringer
- Australian Centre for Microscopy and Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney , New South Wales, 2006, Australia
| | - C Stampfl
- School of Physics, The University of Sydney , New South Wales, 2006, Australia
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Saadaoui H, Luo X, Salman Z, Cui XY, Bao NN, Bao P, Zheng RK, Tseng LT, Du YH, Prokscha T, Suter A, Liu T, Wang YR, Li S, Ding J, Ringer SP, Morenzoni E, Yi JB. Intrinsic Ferromagnetism in the Diluted Magnetic Semiconductor Co:TiO_{2}. Phys Rev Lett 2016; 117:227202. [PMID: 27925730 DOI: 10.1103/physrevlett.117.227202] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2016] [Indexed: 06/06/2023]
Abstract
Here we present a study of magnetism in Co_{0.05}Ti_{0.95}O_{2-δ} anatase films grown by pulsed laser deposition under a variety of oxygen partial pressures and deposition rates. Energy-dispersive spectrometry and transmission electron microscopy analyses indicate that a high deposition rate leads to a homogeneous microstructure, while a very low rate or postannealing results in cobalt clustering. Depth resolved low-energy muon spin rotation experiments show that films grown at a low oxygen partial pressure (≈10^{-6} torr) with a uniform structure are fully magnetic, indicating intrinsic ferromagnetism. First principles calculations identify the beneficial role of low oxygen partial pressure in the realization of uniform carrier-mediated ferromagnetism. This work demonstrates that Co:TiO_{2} is an intrinsic diluted magnetic semiconductor.
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Affiliation(s)
- H Saadaoui
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - X Luo
- School of Materials Science and Engineering, UNSW, Sydney, New South Wales 2052, Australia
| | - Z Salman
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - X Y Cui
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - N N Bao
- Department of Materials Science and Engineering, National University of Singapore, 119260, Singapore
| | - P Bao
- School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - R K Zheng
- School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - L T Tseng
- School of Materials Science and Engineering, UNSW, Sydney, New South Wales 2052, Australia
| | - Y H Du
- Institute of Chemical and Engineering Science, Agency for Science, Technology and Research (A*STAR), 1 Pesek Road, Jurong Island, 627833, Singapore
| | - T Prokscha
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - A Suter
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - T Liu
- ANKA, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany
| | - Y R Wang
- School of Materials Science and Engineering, UNSW, Sydney, New South Wales 2052, Australia
| | - S Li
- School of Materials Science and Engineering, UNSW, Sydney, New South Wales 2052, Australia
| | - J Ding
- Department of Materials Science and Engineering, National University of Singapore, 119260, Singapore
| | - S P Ringer
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
- The Australian Institute for Nanoscale Science and Technology, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - E Morenzoni
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - J B Yi
- School of Materials Science and Engineering, UNSW, Sydney, New South Wales 2052, Australia
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Abstract
Through first-principles calculations using the nonequilibrium Green's function formalism together with density functional theory, we study the conductance of double-vacancy zigzag graphene nanoribbons doped with four transition metal atoms Ti, V, Cr and Fe. We show that Ti doping induces large spin-filtering with an efficiency in excess of 90% for bias voltages below 0.5 V, while the other metal adatoms do not induce large spin filtering. This is despite the fact that the Ti dopant possesses small spin moment, while large moments reside on V, Cr and Fe dopants. Our analysis shows that the suppression of transmission in the spin-down channel in the Ti-doped graphene nanoribbon, thus the large spin filtering efficiency, is due to transmission anti-resonance arising from destructive quantum interference. These findings suggest that the decoration of graphene with titanium, and possibly other transition metals, can act as effective spin filters for nanospintronic applications.
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Tawfik SA, Cui XY, Ringer SP, Stampfl C. Enhanced oscillatory rectification and negative differential resistance in pentamantane diamondoid-cumulene systems. Nanoscale 2016; 8:3461-3466. [PMID: 26794415 DOI: 10.1039/c5nr07467c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We propose a new functionality for diamondoids in nanoelectronics. Based on the nonequilibrium Green's function formalism and density functional theory, we reveal that when attached to gold electrodes, the pentamantane-cumulene molecular junction exhibits large and oscillatory rectification and negative differential resistance (NDR) - depending on the number of carbon atoms in cumulene (Cn). When n is odd rectification is greatly enhanced where the rectification ratio can reach ∼180 and a large negative differential resistance peak current of ∼3 μA. This oscillatory behavior is well rationalised in terms of the occupancy of the carbon 2p states in Cn. Interestingly, different layers of C atoms in the pentamantane molecule have different contributions to transmission. The first and third layers of C atoms in pentamantane have a slight contribution to rectification, and the fifth and sixth layers have a stronger contribution to both rectification and NDR. Thus, our results suggest potential avenues for controlling their functions by chemically manipulating various parts of the diamondoid molecule, thus extending the applications of diamondoids in nanoscale integrated circuits.
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Tawfik SA, Cui XY, Ringer SP, Stampfl C. Communication: Electrical rectification of C59N: The role of anchoring and doping sites. J Chem Phys 2016; 144:021101. [PMID: 26772547 DOI: 10.1063/1.4940142] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Based on the nonequilibrium Green's function formalism and density-functional theory, we investigate the onset of electrical rectification in a single C59N molecule in conjunction with gold electrodes. Our calculations reveal that rectification is dependent upon the anchoring of the Au atom on C59N; when the Au electrode is singly bonded to a C atom (labeled here as A), the system does not exhibit rectification, whereas when the electrode is connected to the C-C bridge site between two hexagonal rings (labeled here as B), transmission asymmetry is observed, where the rectification ratio reaches up to 2.62 at ±1 V depending on the N doping site relative to the anchoring site. Our analysis of the transmission mechanism shows that N doping of the B configuration causes rectification because more transmission channels are available for transmission in the B configuration than in the A configuration.
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Affiliation(s)
| | - X Y Cui
- Australian Centre for Microscopy and Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - S P Ringer
- Australian Centre for Microscopy and Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - C Stampfl
- School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia
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Sun J, Lei Y, Liu H, Ringer SP, Liu Z. Single crystal forms induced diverse interface structures in TiO2 (B)/anatase dual-phase nanocomposites. CrystEngComm 2016. [DOI: 10.1039/c5ce02411k] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Two types of TiO2 (B) single crystal forms (SCF) and the induced TiO2 (B)/anatase interfaces with different orientation relationships are investigated by TEM. The dominated (001} SCF is confirmed to reveal larger nanotunnels at the interface which suggests an enhanced Li+ transport properties.
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Affiliation(s)
- Jie Sun
- School of Materials Science and Engineering
- Shaanxi Normal University
- Xi'an 710119, PR China
- School of Chemical and Biomolecular Engineering
- The University of Sydney
| | - Yimin Lei
- School of Advanced Materials and Nanotechnology
- Xidian University
- Xi'an 710126, PR China
- School of Chemical and Biomolecular Engineering
- The University of Sydney
| | - Hongwei Liu
- Australian Centre for Microscopy & Microanalysis
- The University of Sydney
- , Australia
| | - S. P. Ringer
- Australian Centre for Microscopy & Microanalysis
- The University of Sydney
- , Australia
- School of Aerospace, Mechanical and Mechatronic Engineering
- The University of Sydney
| | - Zongwen Liu
- School of Chemical and Biomolecular Engineering
- The University of Sydney
- , Australia
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Tawfik SA, Cui XY, Ringer SP, Stampfl C. Endohedral metallofullerenes, M@C60 (M = Ca, Na, Sr): selective adsorption and sensing of open-shell NOx gases. Phys Chem Chem Phys 2016; 18:21315-21. [DOI: 10.1039/c6cp02249a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Based on density-functional theory and non-equilibrium Green's function calculations, we demonstrate that endohedral metallofullerenes (EMFs) are reactive to open-shell gases, and therefore have the potential application as selective open-shell gas sensors.
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Affiliation(s)
| | - X. Y. Cui
- Australian Institute for Nanoscale Science and Technology
- and School of Aerospace
- Mechanical and Mechatronic Engineering
- The University of Sydney
- Australia
| | - S. P. Ringer
- Australian Institute for Nanoscale Science and Technology
- and School of Aerospace
- Mechanical and Mechatronic Engineering
- The University of Sydney
- Australia
| | - C. Stampfl
- School of Physics
- The University of Sydney
- Sydney
- Australia
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Affiliation(s)
- Sherif Abdulkader Tawfik
- School of Physics, ‡Australian Centre for Microscopy
and Microanalysis, and School of
Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - X. Y. Cui
- School of Physics, ‡Australian Centre for Microscopy
and Microanalysis, and School of
Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - S. P. Ringer
- School of Physics, ‡Australian Centre for Microscopy
and Microanalysis, and School of
Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - C. Stampfl
- School of Physics, ‡Australian Centre for Microscopy
and Microanalysis, and School of
Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
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13
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Abdulkader Tawfik S, Cui XY, Carter DJ, Ringer SP, Stampfl C. Sensing sulfur-containing gases using titanium and tin decorated zigzag graphene nanoribbons from first-principles. Phys Chem Chem Phys 2015; 17:6925-32. [PMID: 25679359 DOI: 10.1039/c4cp05919k] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [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
Atom implantation in graphene or graphene nanoribbons offers a rich opportunity to tune the material structure and functional properties. In this study, zigzag graphene nanoribbons with Ti or Sn adatoms stabilised on a double carbon vacancy site are theoretically studied to investigate their sensitivity to sulfur-containing gases (H2S and SO2). Due to the abundance of oxygen in the atmosphere, we also consider the sensitivity of the structures in the presence of oxygen. Density functional theory calculations are performed to determine the adsorption geometry and energetics, and nonequilibrium Green's function method is employed to compute the current-voltage characteristics of the considered systems. Our results demonstrate the sensitivity of both Ti- and Sn-doped systems to H2S, and the mild sensitivity of Ti-doped sensor systems to SO2. The Ti-doped sensor structure exhibits sensitivity to H2S with or without oxidation, while oxidation of the Sn-doped sensor structure reduces its ability to adsorb H2S and SO2 molecules. Interestingly, oxygen dissociates on the Ti-doped sensor structure, but it does not affect the sensor's response to the H2S gas species. Oxidation prevents the dissociation of the H-S bond when H2S adsorbs on the Ti-doped structure, thus enhancing its reusability for this gas species. Our study suggests the potential of Ti- and Sn-doped graphene in selective gas sensing, irrespective of the sensing performance of the bulk oxides.
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Abstract
A systematic trend study of carbon dioxide capture on metal-doped single vacancy/double vacancy graphene.
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Affiliation(s)
| | - X. Y. Cui
- Australian Centre for Microscopy and Microanalysis
- School of Aerospace
- Mechanical and Mechatronic Engineering
- The University of Sydney
- Australia
| | - S. P. Ringer
- Australian Centre for Microscopy and Microanalysis
- School of Aerospace
- Mechanical and Mechatronic Engineering
- The University of Sydney
- Australia
| | - C. Stampfl
- School of Physics
- The University of Sydney
- Sydney
- Australia
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15
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Weston L, Cui XY, Ringer SP, Stampfl C. Density-functional prediction of a surface magnetic phase in SrTiO(3)/LaAlO(3) heterostructures induced by Al vacancies. Phys Rev Lett 2014; 113:186401. [PMID: 25396383 DOI: 10.1103/physrevlett.113.186401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2013] [Indexed: 06/04/2023]
Abstract
Based on first-principles density functional calculations we propose a novel Al vacancy induced ferromagnetism occurring at the LaAlO(3) surface of SrTiO(3)/LaAlO(3) bilayers. Magnetism at cation vacancies away from the surface is quenched due to charge compensation. Magnetic surface Al vacancies are stabilized due to the built-in electric field inside the LaAlO(3) region that raises the energy of the defect level, making charge compensation unfavorable. Surface Al vacancies prefer to form clusters and exhibit two-dimensional ferromagnetic alignment mediated by a long-range magnetic interaction. These results are discussed in light of recent experimental observations.
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Affiliation(s)
- L Weston
- School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - X Y Cui
- Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales 2006, Australia and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - S P Ringer
- Australian Centre for Microscopy and Microanalysis, The University of Sydney, Sydney, New South Wales 2006, Australia and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - C Stampfl
- School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia
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16
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Yeoh WK, Cui XY, Gault B, De Silva KSB, Xu X, Liu HW, Yen HW, Wong D, Bao P, Larson DJ, Martin I, Li WX, Zheng RK, Wang XL, Dou SX, Ringer SP. On the roles of graphene oxide doping for enhanced supercurrent in MgB2 based superconductors. Nanoscale 2014; 6:6166-6172. [PMID: 24793305 DOI: 10.1039/c4nr00415a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Due to their graphene-like properties after oxygen reduction, incorporation of graphene oxide (GO) sheets into correlated-electron materials offers a new pathway for tailoring their properties. Fabricating GO nanocomposites with polycrystalline MgB2 superconductors leads to an order of magnitude enhancement of the supercurrent at 5 K/8 T and 20 K/4 T. Herein, we introduce a novel experimental approach to overcome the formidable challenge of performing quantitative microscopy and microanalysis of such composites, so as to unveil how GO doping influences the structure and hence the material properties. Atom probe microscopy and electron microscopy were used to directly image the GO within the MgB2, and we combined these data with computational simulations to derive the property-enhancing mechanisms. Our results reveal synergetic effects of GO, namely, via localized atomic (carbon and oxygen) doping as well as texturing of the crystals, which provide both inter- and intra-granular flux pinning. This study opens up new insights into how low-dimensional nanostructures can be integrated into composites to modify the overall properties, using a methodology amenable to a wide range of applications.
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Affiliation(s)
- W K Yeoh
- School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, New South Wales 2006, Australia.
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Cui XY, Li L, Zheng RK, Liu ZW, Stampfl C, Ringer SP. Graphene based dots and antidots: a comparative study from first principles. J Nanosci Nanotechnol 2013; 13:1251-1255. [PMID: 23646613 DOI: 10.1166/jnn.2013.6118] [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] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Graphene based quantum dots and antidots are two nanostructures of primary importance for their fundamental physics and technological applications, particularly in the emerging field of graphene-based nanoelectronics and nanospintronics. Herein, based on first principles density functional theory calculations, we report a comparative study on the electronic structure of these two structurally complementary entities, where the bandgap opening, edge magnetism and the role of hydrogenation are investigated. Our results show the diversity of electronic structures of various dots and antidots, whose properties are sensitive to the edge detailed geometry (including size and shape and edge type). Hydrogen passivation plays an essential roal in affecting the related properties, in particular, it leads to larger bandgap values and suppress the edge magnetism. The frontier orbital analysis is employed to rationalize and compare the complicated nature of dots and antidots. Based on the specific geometrical consideration and the total energy competition of the ground antiferromagnetic and the ferromagnetic states, some magnetic structures (the unpassivated 42-atom-antidot and 54-atom-dot) are proposed to be useful as magnetic switches.
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Affiliation(s)
- X Y Cui
- Australian Centre for Microscopy and Microanalysis, The University of Sydney, New South Wales 2006, Australia
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18
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Abstract
Atom probe tomography is an accurate analytical and imaging technique which can reconstruct the complex structure and composition of a specimen in three dimensions. Despite providing locally high spatial resolution, atom probe tomography suffers from global distortions due to a complex projection function between the specimen and detector which is different for each experiment and can change during a single run. To aid characterization of this projection function, this work demonstrates a method for the reverse projection of ions from an arbitrary projection surface in 3D space back to an atom probe tomography specimen surface. Experimental data from transmission electron microscopy tilt tomography are combined with point cloud surface reconstruction algorithms and finite element modelling to generate a mapping back to the original tip surface in a physically and experimentally motivated manner. As a case study, aluminium tips are imaged using transmission electron microscopy before and after atom probe tomography, and the specimen profiles used as input in surface reconstruction methods. This reconstruction method is a general procedure that can be used to generate mappings between a selected surface and a known tip shape using numerical solutions to the electrostatic equation, with quantitative solutions to the projection problem readily achievable in tens of minutes on a contemporary workstation.
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Affiliation(s)
- D Haley
- Department of Materials, University of Oxford, Oxford, U.K.
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19
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Yeoh WK, Gault B, Cui XY, Zhu C, Moody MP, Li L, Zheng RK, Li WX, Wang XL, Dou SX, Sun GL, Lin CT, Ringer SP. Direct observation of local potassium variation and its correlation to electronic inhomogeneity in (Ba(1-x)K(x))Fe2As2 pnictide. Phys Rev Lett 2011; 106:247002. [PMID: 21770591 DOI: 10.1103/physrevlett.106.247002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Indexed: 05/31/2023]
Abstract
Local fluctuations in the distribution of dopant atoms are thought to cause the nanoscale electronic disorder or phase separation in pnictide superconductors. Atom probe tomography has enabled the first direct observations of dopant species clustering in a K-doped 122-phase pnictide. First-principles calculations suggest the coexistence of static magnetism and superconductivity on a lattice parameter length scale over a wide range of dopant concentrations. Our results provide evidence for a mixed scenario of phase coexistence and phase separation, depending on local dopant atom distributions.
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Affiliation(s)
- W K Yeoh
- Australian Centre for Microscopy & Microanalysis, University of Sydney, Sydney, New South Wales, Australia.
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20
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Stephenson LT, Moody MP, Gault B, Ringer SP. Estimating the physical cluster-size distribution within materials using atom-probe. Microsc Res Tech 2010; 74:799-803. [PMID: 23939666 DOI: 10.1002/jemt.20958] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 09/22/2010] [Indexed: 11/11/2022]
Affiliation(s)
- L T Stephenson
- Australian Center for Microscopy and Microanalysis, The University of Sydney, New South Wales 2006, Australia.
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21
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Li LY, Cheng YH, Luo XG, Liu H, Wen GH, Zheng RK, Ringer SP. Room-temperature ferromagnetism and the scaling relation between magnetization and average granule size in nanocrystalline Zn/ZnO core-shell structures prepared by sputtering. Nanotechnology 2010; 21:145705. [PMID: 20234078 DOI: 10.1088/0957-4484/21/14/145705] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Ferromagnetism is found in nanocrystalline Zn/ZnO core-shell structures prepared by sputtering pure Zn with subsequent oxidation. The saturation magnetization (M(S)) of the passivated ZnO shells increases with decrease in average particle size (d). The Curie temperature of the samples is above 400 degrees C. It is found that the ferromagnetism has a close relationship with point defects in ZnO shells. The maximum magnetization is estimated to be 28 emu cm(-3) (i.e. 0.14 mu(B) per unit cell) at 300 K, which is over three orders of magnitude larger than that of undoped ZnO nanoparticles or nanorods (10(-3)-10(-2) emu cm(-3)). More importantly, there is a scaling relation of M(s) alpha 1/d(n) (n = 5.20 +/- 0.20) for samples with d <or= 76 nm despite substantial differences in the particle size and shape. The results suggest that defects at the interface of the Zn/ZnO heterostructure make the main magnetic contributions.
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Affiliation(s)
- L Y Li
- Department of Electronics, Nankai University, Tianjin, People's Republic of China
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22
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Gault B, Moody MP, Saxey DW, Cairney JM, Liu Z, Zheng R, Marceau RKW, Liddicoat PV, Stephenson LT, Ringer SP. Atom Probe Tomography at The University of Sydney. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/978-3-540-77968-1_15] [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: 02/20/2023]
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23
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Abstract
A dual FIB/SEM provides solutions to many challenges in atom probe specimen preparation. When combined with an in situ lift-out capability, the versatility of this tool allows almost any region of interest, in almost any geometry, to be placed at the apex of a specimen tip. Several preparation techniques have been developed in response to specific application requirements; for example, in cases where materials are not suitable for electropolishing, or where site-specific analysis is required. Two general techniques, with wide-ranging potential applications, are described in detail here. The first is a 'cut-out' technique that provides a relatively quick means of micro-tip specimen preparation from bulk material samples. The second method is a 'lift-out' technique that can be used in an in situ or ex situ mode and does not require the preparation of pre-sharpened mounting points.
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Affiliation(s)
- D W Saxey
- Australian Key Centre for Microscopy & Microanalysis, University of Sydney, Sydney, NSW 2006, Australia.
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24
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Abstract
The characterization of the Burgers vector of dislocations from large-angle convergent-beam electron diffraction (LACBED) patterns is now a well-established method. The method has already been applied to relatively large and isolated dislocation loops in semiconductors. Nevertheless, some severe experimental difficulties are encountered with small dislocation loops. By using a 2 microm selected-area aperture and a carbon contamination point to mark the loop of interest, we were able to characterize both the plane and the Burgers vector of dislocation loops of a few tens of nanometres in size present in Al-Cu-Mg alloys.
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Affiliation(s)
- J P Morniroli
- Laboratoire de Métallurgie Physique et Génie des Matériaux, UMR CNRS 8517, USTL & ENSCL, Cité Scientifique, 59500 Villeneuve d'Ascq, France.
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25
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Zhu HY, Lan Y, Gao XP, Ringer SP, Zheng ZF, Song DY, Zhao JC. Phase transition between nanostructures of titanate and titanium dioxides via simple wet-chemical reactions. J Am Chem Soc 2005; 127:6730-6. [PMID: 15869295 DOI: 10.1021/ja044689+] [Citation(s) in RCA: 383] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Titanate nanofibers of various sizes and layered structure were prepared from inorganic titanium compounds by hydrothermal reactions. These fibers are different from "refractory" mineral substances because of their dimension, morphology, and significant large ratio of surface to volume, and, surprisingly, they are highly reactive. We found, for the first time, that phase transitions from the titanate nanostructures to TiO(2) polymorphs take place readily in simple wet-chemical processes at temperatures close to ambient temperature. In acidic aqueous dispersions, the fibers transform to anatase and rutile nanoparticles, respectively, but via different mechanisms. The titanate fibers prepared at lower hydrothermal temperatures transform to TiO(2) polymorphs at correspondingly lower temperatures because they are thinner, possess a larger surface area and more defects, and possess a less rigid crystal structure, resulting in lower stability. The transformations are reversible: in this case, the obtained TiO(2) nanocrystals reacted with concentrate NaOH solution, yielding hollow titanate nanotubes. Consequently, there are reversible transformation pathways for transitions between the titanates and the titanium dioxide polymorphs, via wet-chemical reactions at moderate temperatures. The significance of these findings arises because such transitions can be engineered to produce numerous delicate nanostructures under moderate conditions. To demonstrate the commercial application potential of these processes, we also report titanate and TiO(2) nanostructures synthesized directly from rutile minerals and industrial-grade rutiles by a new scheme of hydrometallurgical reactions.
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Affiliation(s)
- H Y Zhu
- Australian Key Centre of Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia.
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26
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Zhu HY, Lan Y, Gao XP, Ringer SP, Zheng ZF, Song DY, Zhao JC. Phase transition between nanostructures of titanate and titanium dioxides via simple wet-chemical reactions. J Am Chem Soc 2005. [PMID: 15869295 DOI: 10.1021/ja044689] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Titanate nanofibers of various sizes and layered structure were prepared from inorganic titanium compounds by hydrothermal reactions. These fibers are different from "refractory" mineral substances because of their dimension, morphology, and significant large ratio of surface to volume, and, surprisingly, they are highly reactive. We found, for the first time, that phase transitions from the titanate nanostructures to TiO(2) polymorphs take place readily in simple wet-chemical processes at temperatures close to ambient temperature. In acidic aqueous dispersions, the fibers transform to anatase and rutile nanoparticles, respectively, but via different mechanisms. The titanate fibers prepared at lower hydrothermal temperatures transform to TiO(2) polymorphs at correspondingly lower temperatures because they are thinner, possess a larger surface area and more defects, and possess a less rigid crystal structure, resulting in lower stability. The transformations are reversible: in this case, the obtained TiO(2) nanocrystals reacted with concentrate NaOH solution, yielding hollow titanate nanotubes. Consequently, there are reversible transformation pathways for transitions between the titanates and the titanium dioxide polymorphs, via wet-chemical reactions at moderate temperatures. The significance of these findings arises because such transitions can be engineered to produce numerous delicate nanostructures under moderate conditions. To demonstrate the commercial application potential of these processes, we also report titanate and TiO(2) nanostructures synthesized directly from rutile minerals and industrial-grade rutiles by a new scheme of hydrometallurgical reactions.
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Affiliation(s)
- H Y Zhu
- Australian Key Centre of Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia.
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27
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Ringer SP, Ratinac KR. On the role of characterization in the design of interfaces in nanoscale materials technology. Microsc Microanal 2004; 10:324-335. [PMID: 15233850 DOI: 10.1017/s1431927604040504] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2002] [Indexed: 05/24/2023]
Abstract
This work reviews recent research on the design and control of interfaces in engineering nanomaterials. Four case studies are presented that demonstrate the power of a multimodal approach to the characterization of different types of interfaces. We have used a combination of conventional, high resolution, and analytical transmission electron microscopy, microbeam electron diffraction, and three-dimensional atom probe to study polymer-clay nanocomposites, turbine rotor steels used for power generation, multicomponent aluminum alloys, and nanocrystalline magnetic materials.
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Affiliation(s)
- S P Ringer
- Australian Key Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006, Australia.
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28
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Zhu HY, Gao XP, Song DY, Bai YQ, Ringer SP, Gao Z, Xi YX, Martens W, Riches JD, Frost RL. Growth of Boehmite Nanofibers by Assembling Nanoparticles with Surfactant Micelles. J Phys Chem B 2004. [DOI: 10.1021/jp049485u] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- H. Y. Zhu
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - X. P. Gao
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - D. Y. Song
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - Y. Q. Bai
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - S. P. Ringer
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - Z. Gao
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - Y. X. Xi
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - W. Martens
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - J. D. Riches
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
| | - R. L. Frost
- Australian Key Centre for Microanalysis & Microscopy and School of Chemistry, The University of Sydney, NSW 2006, Australia, Institute of New Energy Material Chemistry, Nankai University, Tianjin 300071, China, School of Physical and Chemical Science, Queensland University of Technology, Brisbane 4000, Australia, School of Science, Xian Jiaotong University, Xian 710049, China, and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia QLD 4072, Australia
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