The potential applications of shape‐controlled polymeric nanostructures demand well‐defined methods to create tailored shapes. On the other hand, polydopamine (PDA) is a novel polymer promising a variety of innovative applications in many different areas. Since there is no consensus on the pathways involved in the mechanism of formation of PDA, the control of the final morphologies of PDA nanostructures is a challenging task. Herein, it is demonstrated for the first time, how CdTe quantum dots (CdTe QDs) can be used to control the final shape of polymeric structures, in particular, PDA particles. Oxidative self‐polymerization of dopamine is performed in the presence of CdTe QDs, which triggers the formation of blue‐colored rod‐like PDA particles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV‐Vis, Fourier transform infrared (FT‐IR) and Raman spectroscopies, and electrochemical techniques are employed to characterize the structural features of the rod‐like PDA particles. Herein, CdTe QDs modulate the oxidative polymerization of dopamine by the supramolecular assembly of PDA building blocks by π–π and hydrogen bonding interactions, coordination with cadmium ions, and electron transfer processes. The results illustrated here describe a new strategy to manipulate the morphology of PDA nanostructures leading to novel optical properties, opening new applications, and shedding light on the complex mechanism of PDA formation.
Summary
Many metallurgical processes produce characteristic dislocation accumulation, with heterogeneous spatial and orientation distributions and further development of microstructures after heat treatment. Recovery and recrystallisation behaviours are direct consequences of those uneven dislocation distributions. The Electron BackScatter Diffraction (EBSD) technique can be used for the characterisation of such microstructural features, including: Density of Geometrically Necessary Dislocations (GND), Kernel Average Misorientations (KAM), Grain Orientation Spread (GOS), Grain Average Misorientation (GAM), Grain Reference Orientation Deviation (GROD – Angle) and GOS/D, where D is an assumed characteristic grain length.
Production of Fe3%Si alloys with a Goss texture, essential step in the manufacture of electrical transformers, requires several different processing stages, including the one called primary recrystallisation, a key process preceding abnormal grain growth. The structure of grains and different microstructural aspects of the recrystallisation stage will provide the conditions for development of the Goss orientation during abnormal grain growth.
In the present work we use GOS, GAM, GROD, GOS/D, GND and KAM, calculated from EBSD scans performed on cold rolled Fe3%Si alloys subject to increasing heat treatment times, to characterise the kinetics of recovery and primary recrystallisation in an Fe3%Si alloy. Difficulties in the interpretation of these results may arise from the interactive competition between various microstructural features. Hardness measurements were also performed in order to validate recovery and recrystallisation evolution by classical methods.
It was found that the global GOS (i.e. including grains of all orientations) shows changes which can be related to those observed in the hardness for high annealing temperatures but it is not sensitive to microstructure evolution occurring at low temperatures. Meanwhile, GND undergoes changes at all annealing temperatures and, remarkably, it responds to the recovery that GOS cannot detect at low temperatures. The GAM parameter seems to follow better the microhardness results. When grains belonging to different texture components are analysed, gamma fibre grains are the first to recrystallise and alpha fibre grains the last.
Lay Description
Many metallurgical processes produce characteristic dislocation accumulation, with heterogeneous spatial and orientation distributions. Further development of such microstructures occurs with subsequent heat treatments. Recovery and recrystallisation behaviours are directly affected by consequences of those uneven dislocation distributions. The Electron Back Scatter Diffraction (EBSD) technique can be used for the characterisation of such microstructural features using different magnitudes that describe locally or globally misorientations between various locations in the material. In search of the best parameters [among them: Density of Geometrically Necessary Dislocations (GND), Kernel Average Misorientatio...
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