ANSTO :: Browsing by Author "van Riessen, A"

Browsing by Author "van Riessen, A"

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Characterization of insoluble nanoparticles in Antarctic ice cores
(American Geophysical Union, 2013-12-09) Ellis, A; Edwards, R; van Riessen, A; Saunders, M; Smith, AM; Curran, MAJ; Goodwin, ID; Feiteng, W
Insoluble nanoparticles in the form of aerosols have significant effects on climate and biogeochemical cycles. Records of these aerosols are essential for understanding paleoclimate forcing and future climate change. These particles and their precursors are emitted to the atmosphere from a variety of primary and secondary sources including biomass burning as well as biogenic, anthropogenic, volcanic, extraterrestrial, and terrestrial mineral emissions. While a large body of research exists with respect to mineral dust particles (on the micrometer scale) derived from ice and sediment cores, very little is known with regards to the history of insoluble particles on the nano scale. Ice core records are the only reliable way to study the past history of these particles. Here, we will present new data regarding the physical and chemical properties of nanoparticles found in ice cores from East Antarctica.
Characterization of insoluble nanoparticles in ice cores from Law Dome, East Antarctica
(Department of Environment Australian Antartic Division, 2013-06-24) Ellis, A; Edwards, R; van Riessen, A; Smith, AM; Curran, MAJ; Goodwin, ID; Feiteng, W
Insoluble nanoparticles, in the form of aerosols, have significant affects on climate and biogeochemical cycles. Records of these aerosols are essential for understanding paleoclimate forcing and future climate change. While a large body of research exists with respect to mineral dust particles (micron scale) derived from ice cores and sediment cores, very little is known with regards to the history of insoluble nanoparticles. These particles and their precursors are emitted to the atmosphere from a variety of primary and secondary sources including biomass burning, biogenic, anthropogenic, volcanic, and terrestrial mineral emissions. Ice core records are the only reliable way to study the past history of these particles. Here, we will present new data with regards to the physical and chemical properties of these particles as found in the Law Dome ice core, DSS0506 from East Antarctica.
Characterizing black carbon in rain and ice cores using coupled tangential flow filtration and transmission electron microscopy
(European Geosciences Union, 2015-01-01) Ellis, A; Edwards, R; Saunders, M; Chakrabarty, RK; Subramanian, R; van Riessen, A; Smith, AM; Lambrinidis, D; Nunes, LJ; Vallelonga, P; Goodwin, ID; Moy, AD; Curran, MAJ; van Ommen, TD
Antarctic ice cores have been used to study the history of black carbon (BC), but little is known with regards to the physical and chemical characteristics of these particles in the remote atmosphere. Characterization remains limited by ultra-trace concentrations in ice core samples and the lack of adequate methods to isolate the particles unaltered from the melt water. To investigate the physical and chemical characteristics of these particles, we have developed a tangential flow filtration (TFF) method combined with transmission electron microscopy (TEM). Tests using ultrapure water and polystyrene latex particle standards resulted in excellent blanks and significant particle recovery. This approach has been applied to melt water from Antarctic ice cores as well as tropical rain from Darwin, Australia with successful results: TEM analysis revealed a variety of BC particle morphologies, insoluble coatings, and the attachment of BC to mineral dust particles. The TFF-based concentration of these particles has proven to give excellent results for TEM studies of BC particles in Antarctic ice cores and can be used for future studies of insoluble aerosols in rainwater and ice core samples. © Author(s)
Development of carbon nanotube reinforced hydroxyapatite bioceramics
(Elsevier B. V., 2005-11-27) Kealley, CS; Elcombe, MM; Ben-Nissan, B; van Riessen, A
This paper reports development of a production method to create a composite material that is biocompatible, which will have high mechanical strength and resilience, and be able to withstand exposure to the physiological environment. The chemical precipitation conditions necessary for the production of single phase synthetic hydroxyapatite (HAp) have been determined. Neutron and X-Ray diffraction have been used extensively to follow the effects of drying and heat treatments on the process and to confirm that the final material is single phase. The neutron diffraction data has enabled the positions of the hydroxide bonds to be determined. Subsequent development of a technique to produce a HAp + carbon nanotube composite material is also reported. A method has been determined to remove the soot impurity from the nanotubes with minimal degradation of the nanotube. Neutron diffraction patterns collected before and after sintering show that the nanotubes have remained in the structure while most of the remaining soot has burnt off. Small angle neutron scattering, in conjunction with transmission electron microscopy, also shows preservation of the carbon nanotubes. Mechanical property testing is in progress and results will be reported. © The Authors
Development of carbon nanotube-reinforced hydroxyapatite bioceramics
(Elsevier B. V., 2006-11-15) Kealley, CS; Elcombe, MM; van Riessen, A; Ben-Nissan, B
This paper reports development of a production method to create a composite material that is biocompatible, which will have high mechanical strength and resilience, and be able to withstand exposure to the physiological environment. The chemical precipitation conditions necessary for the production of single-phase synthetic hydroxyapatite (HAp) and a HAp and carbon nanotube (CNT) composite material have been optimised. Neutron diffraction patterns collected before and after sintering show that the nanotubes have remained intact within the structure, while most of the remaining soot has burnt off. Small-angle neutron scattering, in conjunction with scanning electron microscopy (SEM), also shows preservation of the CNTs. Hot isostatically pressed samples showed excellent densification. Neutron diffraction data has enabled the positions of the hydroxide bonds to be determined, and shown that the addition of the CNTs has had no effect on the structural parameters of the HAp phase, with the exception of a slight reduction in the unit cell parameter α . © 2006 Elsevier B.V.
In situ applications of soft x-ray ptychography
(Australian Microscopy and Microanalysis Society, 2016-02-04) van Riessen, GA; James, M; van Riessen, A; Phillips, NW; de Jonge, MD; Kourousias, G; Giamoncelli, A; Bozzini, B
Coherent diffractive imaging (CDI) with synchrotron X-ray beams allows extended objects to be characterised at high spatial resolution (<30 nm) and high energy resolution (0.1 eV). In an implementation of CDI known as ptychography, a far-field diffraction pattern is measured from many overlapping regions as the sample is scanned through a coherent X-ray beam. Quantitative images of an object are then obtained from the far-field intensity pattern through iterative reconstruction algorithms. This provides a unique method of studying the elemental and chemical-state distributions in relatively thick materials and their relationship to nanoscale morphology. The high coherent flux offered by synchrotron X-ray sources can also potentially allow high temporal resolution through the use of emerging detector technology and advanced image reconstruction algorithms. This in turn allows the nanoscale structure of functional materials to be studied under non-equilibrium real-time conditions. In this work, we review recent efforts to apply soft X-ray ptychography to in situ and operando applications at several synchrotron facilities. We emphasise studies of functional materials that are characterised by heterogeneity over a range of relevant length scales, including energy storage materials based on polypyrrole nanocomposites and inorganic, aluminosilicate based ceramics. Finally, a perspective on the future prospects of the method will be given, with particular attention to how experimental challenges can be overcome to achieve the spatiotemporal resolution limits defined by the available coherent flux from synchrotron light sources.
Individual particle morphology, coatings, and impurities of black carbon aerosols in Antarctic ice and tropical rainfall
(John Wiley & Sons, Inc, 2016-11-04) Ellis, A; Edwards, R; Saunders, M; Chakrabarty, RK; Subramanian, R; Timms, NE; van Riessen, A; Smith, AM; Lambrindis, D; Nunes, LJ; Vallelonga, P; Goodwin, ID; Moy, AD; Curran, MAJ; van Ommen, TD
Black carbon (BC) aerosols are a large source of climate warming, impact atmospheric chemistry, and are implicated in large-scale changes in atmospheric circulation. Inventories of BC emissions suggest significant changes in the global BC aerosol distribution due to human activity. However, little is known regarding BC's atmospheric distribution or aged particle characteristics before the twentieth century. Here we investigate the prevalence and structural properties of BC particles in Antarctic ice cores from 1759, 1838, and 1930 Common Era (C.E.) using transmission electron microscopy and energy-dispersive X-ray spectroscopy. The study revealed an unexpected diversity in particle morphology, insoluble coatings, and association with metals. In addition to conventionally occurring BC aggregates, we observed single BC monomers, complex aggregates with internally, and externally mixed metal and mineral impurities, tar balls, and organonitrogen coatings. The results of the study show BC particles in the remote Antarctic atmosphere exhibit complexity that is unaccounted for in atmospheric models of BC. ©2016. American Geophysical Union.
Micro- and nano-indentation of a hydroxyapatite-carbon nanotube composite
(American Scientific Publishers, 2008-08) Kealley, CS; Latella, BA; van Riessen, A; Elcombe, MM; Ben-Nissan, B
The mechanical properties of pure synthetic hydroxyapatite and hydroxyapatite-carbon nanotube composites were examined. Vickers microhardness and nanoindentation using a Berkovich tipped indenter were used to determine the hardness, fracture toughness and Young's modulus of the pure hydroxyapatite matrix and the composite materials. Microscopy showed that for the composites produced the carbon nanotubes were present as discrete clumps. These clumps induced a detrimental effect on the hardness of the materials, while the fracture toughness values were not affected. This would be undesirable in terms of using the material for biomedical implant applications. It should be noted that the carbon nanotubes used contained free graphite. As the properties of the composite materials studied were not greatly improved over the matrix, it is speculated that if the graphite phase were removed from the reagent, this could in-turn enhance the properties of the material. © 2008, American Scientific Publishers
Microstrain in hydroxyapatite carbon nanotube composites
(Wiley-Blackwell, 2008-01-15) Kealley, CS; Elcombe, MM; van Riessen, A
Synchrotron radiation diffraction data were collected from hydroxyapatite–carbon nanotube bioceramic composites to determine the crystallite size and to measure changes in non-uniform strain. Estimates of crystallite size and strain were determined by line-profile fitting of discrete peaks and these were compared with a Rietveld whole-pattern analysis. Overall the two analysis methods produced very similar numbers. In the commercial hydroxyapatite material, one reflection in particular, (0 2 3), has higher crystallite size and lower strain values in comparison with laboratory-synthesized material. This could indicate preferential crystal growth in the [0 2 3] direction in the commercial material. From the measured strains in the pure material and the composite, there was a degree of bonding between the matrix and strengthening fibres. However, increasing the amount of carbon nanotubes in the composite has increased the strain in the material, which is undesirable for biomedical implant applications. © 2008, Wiley-Blackwell
Thermal character of geopolymers synthesized from class f fly ash containing high concentrations of iron and α-quartz.
(Wiley-Blackwell, 2010-01) Rickard, WDA; van Riessen, A; Walls, P
This article reports the thermal characteristics of geopolymers prepared with a class F fly ash containing 15 wt% iron oxide and 20 wt%α-quartz. The characterization techniques used included dilatometry, TGA, DTA, XRD, and SEM. Geopolymer specimens were prepared with nominal ratios of Si:Al=2.3 and Na:Al=0.85. Iron oxide in the fly ash precursor was found to play a critical role in the thermal expansion and morphology of geopolymers at temperatures >500°C. Volume changes of quartz on either side of the α–β phase transition cause only minor variations in thermal expansion. © 2010, Wiley-Blackwell.

Browsing by Author "van Riessen, A"

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