Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Ever since colossal magnetoresistance (CMR) was discovered in Ln1-xAExMnO3 (Ln=lantanide; AE alkaline-earth), establishing the relationship between structure and properties constitutes a prominent place in the landscape of solid-state science because of its intriguing potential applications. The occurrence of different Mn3+/Mn4+ ratios seems to be responsible of the different magnetic behaviours observed and can be tuned by either changing i) the Ln/AE ratio or ii) the oxygen content, i.e., Ln1-xAExMnO3-δ. Although plenty of works has been devoted to the first point, less effort has been devoted to study the effect of the compositional variations at the oxygen sublattice. In spite of the partial break-up occurring at the 3D network of octahedral sharing corners, responsible of the double exchange interactions the oxygen deficient compounds exhibits complex magnetic and electric properties.

δ-Bi2O3, a material with a fluorite-type structure, is one of the best solid-state oxygen-ion conductors. It is a high-temperature form that cannot be quenched to room temperature. However, doping with small amounts of transition metal oxides preserves the δ-Bi2O3 structure at low temperature and retains its anionic conduction properties. The Bi2O3–MoO3 materials are interesting because of their functional properties, chiefly as catalysts and as good ionic conductors. All the phases in this system are related to the fluorite structure except Bi2MoO6 which shows an Aurivillius-type structure.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

A microstructure refined to the nanometer scale originates mechanical property improvements [1]. However ultra-fine grain metals present low thermal stability, requiring the presence of particle dispersions to delay coarsening by grain boundary pinning. Nanoscale dispersions of diamond or graphite offer therefore thermal stability potential, combined with high hardness and thermal conductivity for diamond, and self-lubricating properties in the case of graphite. Copper-diamond (Cu-nD) and copper-graphite (Cu-G), nickel-diamond (Ni-nD) and nickel-graphite (Ni-G), as well as tungsten-diamond (W-nD) and tungsten-graphite (W-G) nanostructured composites have been produced by mechanical synthesis and subsequent heat-treatments. Fundamental challenges involve bonding carbon phases to the chosen matrices: copper exhibits an intrinsically difficult bonding with carbon; while tungsten is a strong carbide former; with Ni exhibiting intermediate characteristics. In addition, carbon phases are prone to amorphization by high-energy milling. Transmission electron microscopy (TEM) observations showed homogeneous particle distributions and intimate bonding between the metallic matrix and the carbon phases. Ring diffraction patterns of the chemically extracted carbon phases demonstrated that nanodiamond milled with Cu preserved crystallinity (Figure 1), while an essentially amorphous nature could be inferred for graphite. Systematic variation of the processing parameters enabled to minimize carbide formation with Ni and W matrices. Heat-treatment of the nanostructured of Ni-nD composites induced the transformation of nanodiamond into onion-like carbons (OLC) inside the Ni nanostructured matrix (Figure 2). Hardening mechanisms and the load transfer ability to the reinforcement particles, as well as thermal stability, have been evaluated through microhardness tests.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

The most active phase of the fluid catalytic cracking (FCC) catalyst, used in oil refinery, is zeolite-Y which is an aluminosilicate with a high internal and external surface area responsible for its high reactivity. Waste FCC catalyst is potentially able to be reused in cement-based materials - as an additive - undergoing a pozzolanic reaction with calcium hydroxide (Ca(OH)2) formed during cement hydration. This reaction produces additional strength-providing reaction products i.e., calcium silicate hydrate (C-S-H) and hydrous calcium aluminates (C-A-H) which exact chemical formula and structure are still unknown. Partial replacement of cement by waste FCC catalyst has two key advantages: (1) lowering of cement production with the associated pollution reduction as this industry represents one of the largest sources of man-made CO2 emissions, and (2) improving the mechanical properties and durability of cement-based materials. Despite these advantages, there is a lack of fundamental knowledge on pozzolanic reaction mechanisms as well as spatial distribution of porosity and solid phases interactions at the microstructural level and consequently their relationship with macroscopical engineering properties of catalyst/cement blends.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

In recent years there has been an increased interest in characterisation methods capable of evaluating the response of nanostructured materials such as quantum dots and nanotubes to externally applied stimuli. However, due to issues concerning sample homogeneity and non-uniform orientation, the study of collective responses can lead to ambiguous results. Therefore, it is crucial to perform a complementary evaluation at the single nanostructure level which requires the use of sophisticated analytical instrumentation. In addition to high spatial resolution, the equipment employed must permit sample manipulation and real-time imaging of the in situ stimulus response. Transmission electron microscopes (TEM) observe all these requirements. Furthermore, novel developments in sample holder design and manufacturing have opened a window to an unprecedented range of new in situ experiments. As a result, varied reports are increasingly populating the in situ TEM literature examining such different matters as temperature-related structural phase changes of nanoparticles or dopant diffusion in nanoscaled batteries.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Research at the nanometer scale, aiming to create novel materials and devices offering better performance than those of macro/micro systems, is currently of great relevance in many topics of modern science, technology and engineering. In what concerns coatings technology, the nanocomposite films can offer excellent properties in different applications, representing their morphological characterization a great challenge.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Mesoporous materials have typical average pore diameters in the range 20 – 500 Å, which are usually accompanied by high specific surface area (ABET) and large pore volume (Vp) with narrow pore size distributions. These features are very attractive for potential application as catalysts and adsorbents. Mesoporous materials are usually prepared by soft templating or nanocasting process. The latter approach is based on the replication of hard-templates, such as mesoporous silica (e.g. SBA-15), being a very flexible and suitable method to obtain stable and predictable pore mesostructures. However, the chemical compatibility between the template and the precursors must be ensured.

There is a wide range of surface analysis techniques which are, generally, complementary and provide target information for depths near the surface. Nuclear techniques, which are non-destructive, provide for analysis over a few microns close to the surface giving absolute values of concentrations of isotopes and elements. They have been applied in areas such as scientific, technologic, industry, arts and medicine, using MeV ion beams. Nuclear reactions permit tracing of isotopes with high sensitivities. We use ion-ion reactions and the energy analysis method. At a suitable energy of the incident ion beam, an energy spectrum is recorded of ions from the reaction, coming from several depths in the target. Such spectra are computationally predicted, giving target composition and concentration profile information. Elastic scattering is a particular and important case. A computer program has been developed in this context, mainly for flat targets. The non-flat target situation arises as an extension.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

The properties of nanostructured advanced materials such as carbon nanotubes and nanocrystalline diamond (CNT/NCD) hybrids are known to be closely linked to their morphology, therefore requiring reliable measuring techniques based on quantitative microscopy supported by digital image processing. The development of such techniques is strongly related to hardware evolution and software availability for digital image processing and analysis.