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In this research, in situ ultrafine Al–Ni intermetallics were fabricated as reinforcement in the aluminum matrix by Friction Stir Process (FSP). Activated and non-activated powders were used as reinforcement agents. The FSP was performed under the rotating speed of 1250rpm, traverse speed of 24, 32, 44 and 62mm/min to fabricate composite. Scanning Electron Microscopy, Optical Microscopy and XRD patterns were used for microstructural observations and phase analysis of fabricated composite, respectively. In this study, it is shown that by using nickel powder (non-activated), only Al₃Ni compound is formed during FSP. But in the fabricated composite with activated powder because of increasing grain boundaries and dislocation during ball milling, Al₃Ni₂, Al₃Ni and AlNi may be formed. Using activated powder creates ultrafine intermetallic reinforcements and causes more uniform distribution of intermetallics.

Increasing awareness that structures and attributes on a nanometre scale within aerosol particles may play a significant role in determining their behaviour has highlighted the need for suitable single ultrafine particle analysis methods. By adopting technologies developed within complementary disciplines, together with the development of aerosol-specific methods, a basis for characterizing single sub-100 nm (ultrafine) particles and features in terms of size, morphology, topology, composition, structure and physicochemical properties is established. Size, morphology and surface properties are readily characterized in the scanning transmission electron microscope (STEM), while high-resolution transmission electron microscopy (HRTEM) allows structural information on particles and atomic clusters to sub-0.2 nm resolution. Electron energy loss spectroscopy (EELS) and X-ray emission in the STEM allow the chemical analysis of particles and particle regions down to nanometre diameters. Scanning probe microscopy offers the possibility of analysing nanometre-diameter particles under ambient conditions, thus getting away from some of the constraints imposed by electron microscopy. Imaging methods such as atomic force microscopy and near-field scanning optical microscopy (NSOM) offer novel and exciting possibilities for the characterization of specific aerosols. Developments in aerosol mass spectrometry are providing the means for chemically characterizing sizesegregated ultrafine particles down to 10 nm in diameter on-line. By taking a multi-disciplinary approach, the compilation and development of complementary tools allowing both routine and in-depth analysis of individual ultrafine particles is possible.

Many ultrafine particles comprised classically of low-toxicity, low-solubility materials such as carbon black and titanium dioxide have been found to have greater toxicity than larger, respirable particles made of the same material. The basis of the increased toxicity of the ultrafine form is not well understood and a programme of research has been carried out in Edinburgh on the toxicology of ultrafines aimed at understanding the mechanism. We used fine and ultrafine carbon black, TiO₂ and latex and showed that there was an approximately 10-fold increase in inflammation with the same mass of ultrafine compared with fine particles. Using latex particles in three sizes—64, 202 and 535 nm—revealed that the smallest particles (64 nm) were profoundly inflammogenic but that the 202 and 535 nm particles had much less activity, suggesting that the cut-off for ultrafine toxicity lies somewhere between 64 and 202 nm. Increased oxidative activity of the ultrafine particle surface was shown using the fluorescent molecule dichlorofluorescein confirming that oxidative stress is a likely process by which the ultrafines have their effects. However, studies with transition-metal chelators and soluble extracts showed that the oxidative stress of ultrafine carbon black is not necessarily due to transition metals. Changes in intracellular Ca²⁺ levels in macrophage-like cells after ultrafine particle exposure suggested one way by which ultrafines might have their pro-inflammogenic effects.