10 research outputs found

    Analysis of the Development of Abnormal Grains Structures During Beta Annealing of Ti-64 Wrought Products

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    The ß-annealing of Titanium-6Al-4V (Ti64) wrought aerospace components can lead to the development of abnormal grain structures (AGS) that jeopardise material performance. Therefore, an in-depth understanding into the origins of AGS will help in the design of processing routes that can avoid the conditions that lead to their development. This research demonstrates the application of novel concurrent in-situ heating and electron back scatter diffraction (EBSD) techniques to help elucidate possible mechanisms for the development of AGS. It was found that primary-a (ap) may play a key role, acting as a second phase particle, in pinning the ß-phase grain boundaries during recrystallisation. The strengthening of a large area cube component texture macrozone, consisting of predominantly low angle grain boundaries, is also a prerequisite for the development of AGS

    Analysis of the Development of Abnormal Grains Structures During Beta Annealing of Ti-64 Wrought Products

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    The ß-annealing of Titanium-6Al-4V (Ti64) wrought aerospace components can lead to the development of abnormal grain structures (AGS) that jeopardise material performance. Therefore, an in-depth understanding into the origins of AGS will help in the design of processing routes that can avoid the conditions that lead to their development. This research demonstrates the application of novel concurrent in-situ heating and electron back scatter diffraction (EBSD) techniques to help elucidate possible mechanisms for the development of AGS. It was found that primary-a (ap) may play a key role, acting as a second phase particle, in pinning the ß-phase grain boundaries during recrystallisation. The strengthening of a large area cube component texture macrozone, consisting of predominantly low angle grain boundaries, is also a prerequisite for the development of AGS

    Understanding the Molecular Conformation and Viscoelasticity of Low Sol-Gel Transition Temperature Gelatin Methacryloyl Suspensions

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    For biomedical applications, gelatin is usually modified with methacryloyl groups to obtain gelatin methacryloyl (GelMA), which can be crosslinked by a radical reaction induced by low wavelength light to form mechanically stable hydrogels. The potential of GelMA hydrogels for tissue engineering has been well established, however, one of the main disadvantages of mammalian-origin gelatins is that their sol-gel transitions are close to room temperature, resulting in significant variations in viscosity that can be a problem for biofabrication applications. For these applications, cold-water fish-derived gelatins, such as salmon gelatin, are a good alternative due to their lower viscosity, viscoelastic and mechanical properties, as well as lower sol-gel transition temperatures, when compared with mammalian gelatins. However, information regarding GelMA (with special focus on salmon GelMA as a model for cold-water species) molecular conformation and the effect of pH prior to crosslinking, which is key for fabrication purposes since it will determine final hydrogel’s structure, remains scarce. The aim of this work is to characterize salmon gelatin (SGel) and salmon methacryloyl gelatin (SGelMA) molecular configuration at two different acidic pHs (3.6 and 4.8) and to compare them to commercial porcine gelatin (PGel) and methacryloyl porcine gelatin (PGelMA), usually used for biomedical applications. Specifically, we evaluated gelatin and GelMA samples’ molecular weight, isoelectric point (IEP), their molecular configuration by circular dichroism (CD), and determined their rheological and thermophysical properties. Results showed that functionalization affected gelatin molecular weight and IEP. Additionally, functionalization and pH affected gelatin molecular structure and rheological and thermal properties. Interestingly, the SGel and SGelMA molecular structure was more sensitive to pH changes, showing differences in gelation temperatures and triple helix formation than PGelMA. This work suggests that SGelMA presents high tunability as a biomaterial for biofabrication, highlighting the importance of a proper GelMA molecular configuration characterization prior to hydrogel fabrication

    Cold-adaptation of a methacrylamide gelatin towards the expansion of the biomaterial toolbox for specialized functionalities in tissue engineering

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    © 2019 Elsevier B.V.Tissue regeneration is witnessing a significant surge in advanced medicine. It requires the interaction of scaffolds with different cell types for efficient tissue formation post-implantation. The presence of tissue subtypes in more complex organs demands the co-existence of different biomaterials showing different hydrolysis rate for specialized cell-dependent remodeling. To expand the available toolbox of biomaterials with sufficient mechanical strength and variable rate of enzymatic degradation, a cold-adapted methacrylamide gelatin was developed from salmon skin. Compared with mammalian methacrylamide gelatin (GelMA), hydrogels derived from salmon GelMA displayed similar mechanical properties than the former. Nevertheless, salmon gelatin and salmon GelMA-derived hydrogels presented characteristics common of cold-adaptation, such as reduced activation energy for collagenase, increased enzymatic hydrolysis turnover of hydrogels, increased interconnected polypepti

    Who sows? Who reaps? Women and land rights in India

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