311 research outputs found
Dr. Elisabeth Gruner - Faculty Author Interview
No full textDr. Elisabeth Gruner, Associate Professor of English, discusses her new book, Constructing the Adolescent Reader in Contemporary Young Adult Fiction, published recently by Palgrave Macmillan. The book considers a range of contemporary titles in order to explore the types of reading sparked through various forms of adolescent fiction
Ordered mesoporous silica nanoparticles with and without embedded iron oxide nanoparticles: Structure evolution during synthesis
No full textThis work reports on the structural evolution during room temperature synthesis of hexagonally ordered mesoporous silica nanoparticles with and without embedded iron oxide particles. Oleic acid-capped iron oxide nanoparticles are synthesized and transferred to an aqueous phase using the cationic surfactant, hexadecyltrimethylammonium bromide (CTAB). MCM-41 type silica and composite nanoparticles are fabricated via sol-gel synthesis. Aliquots are taken from the solution during synthesis to capture the particle formation process. Transmission Electron Microscopy (TEM) and Small Angle X-ray Scattering (SAXS) reveal a transition from a disordered to an ordered structure in both synthesis systems. Along with the evolution of structure, iron oxide nanoparticles acting as seeds at the early stages are relocated from the particle centers to the edges. Nitrogen sorption measurements for iron oxide-embedded mesoporous nanoparticles indicate surface areas as high as for the mesoporous silica nanoparticles without iron oxide.N
Reconstructing three-dimensional protein crystal intensities from sparse unoriented two-axis X-ray diffraction patterns. Corrigendum
No full textA figure in the article by Lan, Wierman, Tate, Philipp, Elser & Gruner [J. Appl. Cryst. (2017), 50, 985–993] is corrected.</jats:p
QUANTUM METAMATERIALS DIRECTED BY BLOCK COPOLYMER SELF-ASSEMBLY VIA ADVANCED MANUFACTURING
No full text212 pagesSupplemental file(s) description: Movies.Materials manufacturing and processing is the key to the adoption and widespread application of revolutionary materials that have indelibly shaped human civilization. The current landscape of quantum materials fabrication is overwhelmingly dominated by solid state chemical reactions and physical deposition techniques, typically under stringent synthetic conditions such as ultrahigh vacuum. In this dissertation, quantum materials structure-directed by block copolymer (BCP) self-assembly and prepared by advanced manufacturing techniques are presented using three examples to illustrate the promise of BCP-enabled quantum metamaterials. The self-assembly of BCPs offers an alternative pathway toward quantum materials that is versatile, tunable, and bottom-up via solution-based processing. The structure engineering by BCP self-assembly imparts a quantum-level influence on the materials behavior in ways unattainable by compositions alone, signifying distinct characteristics of quantum metamaterials. Facilitated by advanced manufacturing, the convergence of BCP self-assembly and quantum materials is embodied by its dual scientific and technological merits.Firstly, crystalline silicon with a mesoscale symmetry suggesting topologically protected Weyl points was prepared through non-equilibrium laser heating. The unique symmetry was broken from the alternating/single gyroid morphology self-assembled by BCPs and carbon precursors, which formed a mesoporous template after pyrolysis. After deposition into the template in the amorphous form, silicon attained otherwise inaccessible mesoscale ordering in the crystalline form following transient laser heating in air on a nanosecond time scale. The short heating duration melted and crystallized the silicon under highly non-equilibrium conditions that far outpaced the decomposition kinetics of the organically derived template, thus preserving the mesostructural integrity. The resulting topologically relevant symmetry was revealed by grazing incidence small-angle X-ray scattering and represented the first of its kind as topological quantum metamaterials. Secondly, mesoporous superconductors directed by BCP self-assembly were expanded into the thin film regime. Technologically more important than previous monolithic pieces derived from evaporation-induced self-assembly, thin films were prepared by spin-coating the hybrid solution containing the structure-directing BCP and niobia sol on a silicon substrate. Mesoporous superconducting niobium nitride thin films were prepared after heat treatments in air and reactive gases of ammonia and carburizing gas. The granular nanocrystals in a network morphology displayed a thermally activated conduction mechanism. The upper critical field derived from measurements of field-dependent critical temperatures exceeded values reported in literature for bulk niobium nitride. Moreover, the spin-coated films could be integrated into typical nanofabrication processes. Using lithography to define patterns, the thin films again exhibited superconductivity. Lastly, self-assembled mesoporous superconductors were complemented by the diverse form factors enabled through 3D printing (additive manufacturing). Direct ink writing commercially available Pluronic BCPs mixed with niobia sol in a hydrophobic bath ensured proper mechanical strength due to ink precipitation. After similar heat treatment to convert into niobium nitride, the 3D printed superconductors were hierarchically ordered across several length scales, from the nanocrystals, through the periodic hexagonal mesostructure, to the macroscopic woodpile shape. Moreover, embedded printing yielded complex non-self-supporting geometries such as helices, which were also converted to superconducting niobium nitrides. Such 3D printed superconductors had a specific surface area of over 120 m2/g. The confinement resulting from both the BCP structure direction and the nitride crystal granularity led to an upper critical field of 50 T, amongst the highest reported for niobium nitride. The enhanced performance in the upper critical field could be further tuned by the molar mass of the structure directing Pluronic BCPs, a clear fingerprint of quantum metamaterials behavior. The dissertation commences with an introduction reviewing the existing research effort surrounding BCP self-assembly-directed quantum materials. The body of the dissertation, including the three examples summarized above, is adapted from scientific articles of respective work, either published or under preparation at the time of dissertation writing. The dissertation concludes by offering critical perspectives for further directions in this emerging field that may help navigate through the challenges in the future
Versatile, reprogrammable area pixel array detector for time-resolved synchrotron x-ray applications
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