Publications by authors named "Sheyfer D"
Article Synopsis
- The study focuses on the microscopic mechanisms behind the impressive electromechanical properties of relaxor ferroelectrics, specifically looking at polar nanodomains (PNDs) and their organization on different scales.
- Using x-ray coherent nanodiffraction, researchers discovered that PNDs in the material PMN-0.32PT self-assemble into structured patterns called polar laminates, which influence how they respond to electric fields.
- The findings underline the importance of understanding the complex organization of these lattice structures, which can help improve the design of not just relaxors but also other quantum and functional materials.
Article Synopsis
- Ameloblasts are specialized cells that create enamel, a complex tissue made up of elongated hydroxylapatite crystals, but their function is not fully understood due to limitations in current experimental models.
- Researchers have successfully created dental epithelial organoids (DEOs) from adult dental epithelial stem cells, which can maintain important cellular markers and survive for over five months in a controlled environment.
- When DEOs were transplanted into mice, they produced enamel-like crystals, making them a valuable model for studying the mineralization process in dental tissues and advancing knowledge about enamel regeneration therapies.
X-ray-induced piezoresponse during X-ray photon correlation spectroscopy of PbMgNbO.
J Synchrotron Radiat
January 2024
Article Synopsis
- X-ray photon correlation spectroscopy (XPCS) is a technique that can observe atomic-scale dynamics in materials during both stable and changing conditions.
- This study focuses on the relaxor ferroelectric material PbMgNbO (PMN) and shows that a weak AC electric field significantly affects the speckle patterns in diffuse scattering related to polar nanodomains.
- The researchers propose a model to explain the unexpected dynamic tilting of the material in response to the X-ray beam, suggesting that this piezoresponse may be important for interpreting results in XPCS and similar studies of insulating materials.
Extractant aggregation in liquid-liquid extraction organic phases impacts extraction energetics and is related to the deleterious efficiency-limiting liquid-liquid phase transition known as third phase formation. Using small angle X-ray scattering, we find that structural heterogeneities across a wide range of compositions in binary mixtures of malonamide extractants and alkane diluents are well described by Ornstein-Zernike scattering. This suggests that structure in these simplified organic phases originates from the critical point associated with the liquid-liquid phase transition.
View Article and Find Full Text PDFTo provide optimal depth resolution with a coded-aperture Laue diffraction microscope, an accurate position of the coded-aperture and its scanning geometry need to be known. However, finding the geometry by trial and error is a time-consuming and often challenging process because of the large number of parameters involved. In this paper, we propose an optimization approach to automate the focusing process after data is collected.
View Article and Find Full Text PDFArticle Synopsis
- Researchers are developing new methods to analyze the structure of electrode materials when they're in use, which helps connect structure to their electrochemical properties.* -
- Current techniques struggle with both the level of detail and the conditions needed to observe significant structural changes during operation.* -
- Using a combination of advanced imaging and electrochemical methods, the study reveals that surface strain changes during polarization are influenced by electrode surface charge and reactions, while the core remains stable, providing insights for improving electrochemical performance.*
Article Synopsis
- * The study uses Bragg coherent X-ray diffractive imaging to observe nanoscale structural dynamics in BZY over 40 hours at 200 °C, revealing surprising topological defects and cracking despite overall material stability.
- * Findings indicate that nanoscale processes significantly influence proton conductivity and hydration in solid oxides, providing insights for improving low-temperature protonic ceramic electrochemical cells.
Liquid-liquid extraction (LLE), the go-to process for a variety of chemical separations, is limited by spontaneous organic phase splitting upon sufficient solute loading, called third phase formation. In this study we explore the applicability of critical phenomena theory to gain insight into this deleterious phase behavior with the goal of improving separations efficiency and minimizing waste. A series of samples representative of rare earth purification were constructed to include each of one light and one heavy lanthanide (cerium and lutetium) paired with one of two common malonamide extractants (DMDOHEMA and DMDBTDMA).
View Article and Find Full Text PDFDespite intensive studies in the past decades, the local structure of disordered matter remains widely unknown. We show the results of a coherent x-ray scattering study revealing higher-order correlations in dense colloidal hard-sphere systems in the vicinity of their crystallization and glass transition. With increasing volume fraction, we observe a strong increase in correlations at both medium-range and next-neighbor distances in the supercooled state, both invisible to conventional scattering techniques.
View Article and Find Full Text PDFThe advent of high-speed x-ray photon correlation spectroscopy now allows the study of critical phenomena in fluids to much smaller length scales and over a wider range of temperatures than is possible with dynamic light scattering. We present an x-ray photon correlation spectroscopy study of critical fluctuation dynamics in a complex fluid typical of those used in liquid-liquid extraction (LLE) of ions, dodecane-DMDBTDMA with extracted aqueous Ce(NO_{3})_{3}. We observe good agreement with both static and dynamic scaling without the need for significant noncritical background corrections.
View Article and Find Full Text PDFThe application of X-ray photon correlation spectroscopy (XPCS) at free-electron laser (FEL) facilities enables, for the first time, the study of dynamics on a (sub-)nanometre scale in an unreached time range between femtoseconds and seconds. For soft-matter materials, radiation damage is a major limitation when going beyond single-shot applications. Here, an XPCS study is presented at a hard X-ray FEL on radiation-sensitive polymeric poly(-isopropylacrylamide) (PNIPAM) nanoparticles.
View Article and Find Full Text PDFCore-shell microgels were synthesized via a free radical emulsion polymerization of thermoresponsive poly-(-isopropyl acrylamide), pNipam, on the surface of silica nanoparticles. Pure pNipam microgels have a lower critical solution temperature (LCST) of about 32 °C. The LCST varies slightly with the crosslinker density used to stabilize the gel network.
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