Effect of electric field on exfoliation of nanoplates

Nanocomposite performance relies on reproducible dispersion and arrangement of nanoparticles, such that the dominant morphology across macroscopic dimensions is nanoscopic. The impact of electric fields on the interaction of nanoplates is discussed for improving dispersion. For ideal dielectrics, an electric field may assist (or retard) exfoliation depending on the angle between a collection of plates and the field. A critical electric field strength for exfoliation is predicted. Structural refinement occurs by cleavage through the center of the stack. For lossy dielectrics, frequency can be tuned to cause exfoliation in all plate orientations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87809/2/223118_1.pd

Preface

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77506/1/1700_ftp.pd

Autonomous motility of polymer films coupled to stimuli gradients

Adaptive soft materials exhibit a diverse set of behaviors including reconfiguration, actuation, and locomotion. These responses are typically optimized in isolation. Here, we explore the interrelation between these behaviors by developing a behavioral phase diagram for hygromorphic polymer films. We determine that the dynamic behaviors are a result of not only a response to, but also an interaction with a humidity gradient, which can be tuned via control of the environment and film characteristics, including size, permeability and coefficient of hygroscopic expansion to target a desired behavior such as multi-modal locomotion. Using the improved understanding of stimuli interactive materials gained from our study of monolithic polymer films, we demonstrate how robust composites can be designed to exhibit autonomous, environmentally-responsive behaviors, and how these concepts can be incorporated into origami structures to engineer the extent and sequence of motions

Solid-gas phase photo-catalytic behaviour of rutile and TiOn (1<n<2) sub-oxide phases for self-cleaning applications

The solid-gas phase photo-catalytic activities of rutile TiO₂ and TiO n (1 &lt; n &lt; 2) sub-oxide phases have been evaluated. Varying concentrations of Ti 3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 °C to 1300 °C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti 3+ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti 3+-Ti 4+ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO₂ and CO₂ under UV irradiation of wavelengths (λ) 376⁻387 nm and 381⁻392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350⁻400 °C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 °C and 400 °C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO₂. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings. </p

Autonomous Materials Discovery Driven by Gaussian Process Regression with Inhomogeneous Measurement Noise and Anisotropic Kernels

A majority of experimental disciplines face the challenge of exploring large and high-dimensional parameter spaces in search of new scientific discoveries. Materials science is no exception; the wide variety of synthesis, processing, and environmental conditions that influence material properties gives rise to particularly vast parameter spaces. Recent advances have led to an increase in efficiency of materials discovery by increasingly automating the exploration processes. Methods for autonomous experimentation have become more sophisticated recently, allowing for multi-dimensional parameter spaces to be explored efficiently and with minimal human intervention, thereby liberating the scientists to focus on interpretations and big-picture decisions. Gaussian process regression (GPR) techniques have emerged as the method of choice for steering many classes of experiments. We have recently demonstrated the positive impact of GPR-driven decision-making algorithms on autonomously steering experiments at a synchrotron beamline. However, due to the complexity of the experiments, GPR often cannot be used in its most basic form, but rather has to be tuned to account for the special requirements of the experiments. Two requirements seem to be of particular importance, namely inhomogeneous measurement noise (input dependent or non-i.i.d.) and anisotropic kernel functions, which are the two concepts that we tackle in this paper. Our synthetic and experimental tests demonstrate the importance of both concepts for experiments in materials science and the benefits that result from including them in the autonomous decision-making process

Solid-gas phase photo-catalytic behaviour of rutile and TiOn (1&lt;n&lt;2) sub-oxide phases for self-cleaning applications

The solid-gas phase photo-catalytic activities of rutile TiO2 and TiOn (1 &lt; n &lt; 2) sub-oxide phases have been evaluated. Varying concentrations of Ti3+ defects were introduced into the rutile polymorph of titanium dioxide through carbo-thermal reduction at temperatures ranging from 350 &deg;C to 1300 &deg;C. The resulting sub-oxides formed were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, impedance spectroscopy and UV-visible diffuse reflectance spectroscopy. The presence of Ti3+ in rutile exposed to high reduction temperatures was confirmed by X-ray diffraction. In addition, a Ti3+-Ti4+ system was demonstrated to enhance the photo-catalytic properties of rutile for the degradation of the air pollutants NO2 and CO2 under UV irradiation of wavelengths (&lambda;) 376&ndash;387 nm and 381&ndash;392 nm. The optimum reduction temperature for photo-catalytic activity was within the range 350&ndash;400 &deg;C and attributed to improved charge-separation. The materials that were subject to carbo-thermal reduction at temperatures of 350 &deg;C and 400 &deg;C exhibited electrical conductivities over one hundred times higher compared to the non-reduced rutile. The results highlight that sub-oxide phases form an important alternative approach to doping with other elements to improve the photo-catalytic performance of TiO2. Such materials are important for applications such as self-cleaning where particles can be incorporated into surface coatings

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

Laser writing of electronic circuitry in thin film molybdenum disulfide: A transformative manufacturing approach

Electronic circuits, the backbone of modern electronic devices, require precise integration of conducting, insulating, and semiconducting materials in two- and three-dimensional space to control the flow of electric current. Alternative strategies to pattern these materials outside of a cleanroom environment, such as additive manufacturing, have enabled rapid prototyping and eliminated design constraints imposed by traditional fabrication. In this work, a transformative manufacturing approach using laser processing is implemented to directly realize conducting, insulating, and semiconducting phases within an amorphous molybdenum disulfide thin film precursor. This is achieved by varying the incident visible (514 nm) laser intensity and raster-scanning the thin film a-MoS2 sample (900 nm thick) at different speeds for micro-scale control of the crystallization and reaction kinetics. The overall result is the transformation of select regions of the a-MoS2 film into MoO2, MoO3, and 2H-MoS2 phases, exhibiting conducting, insulating, and semiconducting properties, respectively. A mechanism for this precursor transformation based on crystallization and oxidation is developed using a thermal model paired with a description of the reaction kinetics. Finally, by engineering the architecture of the three crystalline phases, electrical devices such as a resistor, capacitor, and chemical sensor were laser-written directly within the precursor film, representing an entirely transformative manufacturing approach for the fabrication of electronic circuitry