Paul Midgley (Cambridge)

Electron tomography – a new perspective for materials microscopy

Paul Midgley

Department of Materials Science and Metallurgy, University of Cambridge,
Pembroke Street, Cambridge, CB2 3QZ, UK.
Within materials science and engineering, the push for nanotechnology and the increasing use of nanoscale materials brings with it the need for high spatial resolution imaging and analysis. As the lateral dimensions of a feature approach that of its depth, as is happening for example in many semiconductor fabrication lines, electron microscopy is being pushed towards examining truly 3-dimensional objects and a single projection is not adequate for a complete description. To that end electron tomography has been adapted from the original ideas proposed in the life sciences to meet the needs of the materials scientist working at the nanoscale. Although electron tomography in the life sciences relies on a tilt series of bright field (BF) images exhibiting predominantly mass-thickness contrast, in materials science, for a general crystalline object, diffraction (and Fresnel) contrast very often prohibits the use of (coherent) BF images for electron tomographic reconstruction. Normally, other (incoherent) signals must be used. As such, high-angle annular dark field (HAADF) scanning transmission electron microscopy (STEM) imaging has been developed as the basis for the tomography tilt series and has become the conventional mode for materials-based electron tomography. However, STEM HAADF imaging will not reveal certain important electronic, compositional and structural properties of many materials and so more unconventional modes are also under development. This talk will show examples from both conventional and unconventional electron tomographic experiments including the 3D fractal structure of heterogeneous catalysts using STEM tomography, 3D dislocation arrays using weak-beam tomography, differentiating carbonaceous composite elements using plasmon tomography and the visualisation of 3D electrostatic potentials using holographic tomography.

David StJohn (UQ)

Light Metals Research Towards Commercial Adoption

The CAST Cooperative Research Centre undertakes research across the whole value chain of light metal industries. The variety of research this entails in aluminium, magnesium and titanium will be presented. Also highlighted are projects that involve solving industry needs across elements of the value chain. For example, a customer and supplier working together for mutual benefit. These examples show that the effectiveness and outcomes from the research are significantly enhanced by undertaking a value chain approach to research. Finally, issues related to the successful adoption of research will be discussed.

Adrian Mann (Rutgers)

The relationship between mechanics and disease in biological nanocomposites

Adrian B. Mann, Rutgers University, USA

Since the 1980’s there has been a rapid development of new characterization methods for the study of materials on the nanoscale. Amongst these is nanoindentation which can be used to probe the mechanical properties of materials with a spatial resolution of less than a micron. Nanoindentation has proven to be an invaluable tool in the study of how nanostructure affects the mechanical behavior of materials. The method is now being applied very successfully to the characterization of biological materials, in particular to nanocomposite, mineralized tissues such as bones and teeth. In this talk the effects of diseases and disorders that affect mineralized tissues will be discussed in terms of their impact on the mechanical properties and chemistry of the tissues. Specific examples will be discussed including the development of lesions in human dental enamel and the effect of genetic mutations on small mammalian bones. In each case nanomechanical characterization provides new insight into the disease or disorder. For dental enamel it indicates the possible role of fluoride in preventing caries (cavities) and in bones it shows the links between mineralization, mechanics, genetics and aging.

Liangchi Zhang (USyd)

Some Fundamentals in Characterising Carbon Nanotubes and Their Composites

Liangchi Zhang
School of Aerospace, Mechanical and Mechatronic Engineering
The University of Sydney

Carbon nanotubes, either single-walled or multi-walled, have superior mechanical properties, and have been considered as a promising class of reinforcing materials to make high performance nano-composites. This presentation will discuss a number of theoretical and experimental fundamentals in the mechanical characterisation of carbon nanotubes and their composites, such as wall thickness, Young’s modulus, critical issues in molecular dynamics analysis, stress transfer and dispersion and alignment.

Roberts Stamps (UWA)

Magnetic metal nanostructures: new properties and new opportunities

Robert Stamps
School of Physics, University of Western Australia

Technologies capable of producing a wide range of patterned structures, whose primary functional elements are magnetic, are developing rapidly. Applications include magnetic logic, information storage, spin electronics, high frequency signal processing, and biomedicine. Several examples of Australian magnetics research are being pursued within one or more of these areas, with direct relevance to a number of technologies and applications. These include materials for data storage, microwave signal processing, medical imaging and targeted drug delivery.

This presentation will provide an overview and summary of research in some of these areas.  Specific results from recent research are highlighted which are interesting in terms of intrinsic scientific merit and relevance for technological application. Wall interaction and motion through random potentials are discussed with reference to the general problem of roughening transitions and reversal dynamics for magnetic elements [1]. Aspects of ballistic charge and spin transport through domain boundary walls are illustrated for mesoscopic magnetic wires [2]. Difficult and unsolved problems associated with the general topic of frustration and disorder are described in terms of the ferromagnet/antiferromagnet interface, and also for systems of interacting magnetic nanoparticles [3]. Use of one and two dimensional patterning will be discussed in regards to the control of useful microwave frequency properties [4].

• M. Bauer, A. Mougin, J. P. Jamet, V. Repain, J. Ferré, R. L. Stamps, H. Bernas, C. Chappert, “De-roughening of domain wall pairs by dipolar repulsion”, Phys. Rev. Lett. 94, 207211 (2005).
• R. L. Stamps, P. E. Falloon, V. Gopar, D. Weinmann, R. A. Jalabert, “Domain wall magnetoresistance in magnetic nanowires—Theory”, in Spintronic Materials and Technology, Chapter 9, pp. 203-224 (Taylor and Francis, 2007).
• M. Ali, P. Adie, C. H. Marrows, D. Greig, B. J. Hickey R. L. Stamps, “Exchange bias using a spin glass”, Nature Materials6, 70 (2007).
• M. Kostylev, J. G. Hu, R. L. Stamps, “Confinement quantization of parallel pump instability threshold in mesoscopic structures:  example of metallic ferromagnetic stripes”, Appl. Phys. Lett. 90, 12507 (2007).

Victor Luca (ANSTO)

Nanostructured and Nanoporous Semiconducting Oxides and their Environmental Photochemical Applications

Vittorio Luca

Australian Nuclear Science and Technology Organisation, Institute of Materials and Engineering Sciences, PMB 1, Menai, NSW 2234, AUSTRALIA
e-mail: vlu@ansto.gov.au

Solution-based (sol-gel) processing can offer a simple means of preparing nanostructured and nanoporous semiconducting materials with complex architectures.  This talk will provide an overview of the development of a range of semiconducting oxide materials being undertaken at ANSTO. These materials include hydrothermally prepared microporous titanosilicate materials, nanoheterostructured multilayer thin films, WO₃ films with hierarchical porosity and mesoporous titanate-based thin films.  Ultimately such materials can be considered the building blocks of much more complex and versatile assemblies with potentially novel chemical photochemical and photoelectrochemical properties.  After giving an overview of the individual materials a ‘simple’ example of a multilayer heteronanstructured assembly will be considered.  These assemblies consist of multilayer structures of alternating thin (~ 20 nm) titanium and the tungsten oxide layers have been fabricated from titanium alkoxide and various tungstate precursor solutions using the dip coating technique.  Single, double and triple layer titanate and tungstate thin films were deposited on silicon substrates and these were initially annealed at 400ºC.  Structural and microsctructural aspects of the films were investigated using a variety of techniques including, X-ray reflectometry, Grazing Incidence X-ray Absorption Spectroscopy (GIXAS), cross-sectional Transmission Electron Microscopy (TEM), and Secondary Ion Mass Spectrometry (SIMS).  The thickensses of the films and the interface character were principally gauged by cross-sectional TEM and X-ray reflectometery.  All films were continuous on a local scale and at the treatment temperature of 400ºC only the tungsten oxide component showed any signs of crystallinity.  High quality single and multilayer thin films with relatively low surface roughness could be generated using this sol-gel approach.  The multilayer films had relatively diffuse interfaces even after annealing in air at temperatures as low as 400ºC.  At these temperatures easily measurable diffusion of tungsten into the titanium oxide component was observed while the diffusion of titanium into the tungsten oxide component occurred to a lesser degree.  At higher temperatures interdiffusion of components was found to be significant.  TEM, X-ray diffraction and Ti K-edge GIXAS measurements all indicated that annealing at 400ºC generated films in which the titanate component remained amorphous while the tungstate component crystallized in the tetragonal modification of WO₃, which is normally stable only at high temperatures.  Grazing incidence X-ray absorption spectroscopy allowed the degree of distortion of the tungsten oxygen polyhedra to be monitored as a function of depth into the film.  The photochemistry of the multilayer film electrodes was investigated and the activity for water photo-oxidation assessed.  The photoactivity was greatest when crystalline WO₃ was bounded on both sides by amorphous TiO₂ layers.  In this bounded state, WO₃ has unique structural characteristics.