Exploration of torsional actuation and twist to writhe transition in nanostructured hydrogels

Torsional artificial muscles are a branch of actuators that react to a stimulus by rotating. This rotation is driven by a change in volume and mechanical properties such as modulus and was shown to be extremely large in the case of twisted fibers due to their helical geometry. The following thesis introduces a new method of fabrication of nanofiber yarns and nanocomposites with the aim of making hydrogel torsional catch actuators that combine responsiveness to pH changes and a high torsional output as well as a systematic approach to the modeling of their behavior using the single helix theory

アルミニウムと窒化ホウ素ナノチューブによる新規複合材料の開発

筑波大学 (University of Tsukuba)201

Boron Nitride Nanotube based Lightweight Metal Matrix Composites: Microstructure Engineering and Stress-Transfer Mechanics

Lightweight metals, such as Aluminum, Magnesium and Titanium, are receiving widespread attention for manufacturing agile structures. However, the mechanical strength of these metals and their alloys fall short of structural steels, curtailing their applicability in engineering applications where superior load-bearing ability is required. There is a need to effectively augment the deformation- and failure-resistance of these metals without compromising their density advantage. This dissertation explores the mechanical reinforcement of the aforementioned lightweight metal matrices by utilizing Boron Nitride Nanotube (BNNT), a 1D nanomaterial with extraordinary mechanical properties. The nanotubes are found to resist thermo-oxidative transformations up to ~750°C, establishing their suitability for engineering metal matrix composites. Al-BNNT composites are fabricated by three classes of scalable processing approaches: powder metallurgy, solidification and plasma spray additive manufacturing. These processing techniques unravel metal-nanotube interactions in a vast processing space, such as state of metal (solid versus liquid), the timescale of interactions (10-3 to 10+3 s), range of temperatures (102 to 103°C) and pressures (10-1 to 10+1 MPa). Limited interfacial reactions between Al and BNNT are observed, which improve wetting, capture, bonding and stress-transfer in the composites. Consequently, remarkable mechanical reinforcement is achieved, with ~400% improvement in tensile strength, an order of magnitude jump in hardness, and up to two-fold enhancement of elastic modulus. Nanofiller assisted reinforcement of Magnesium alloys is challenging because of their low plasticity. Therefore, an architected, layered composite of AZ31 Mg alloy and BNNT is engineered to minimize embrittlement. In-situ double cantilever testing reveals effective crack bridging by BNNT, facilitated by reactive interface bonding. Inspired by the importance of interphases, this work investigates the correlation between deformation mechanisms and chemical make-up of the composites. Ti-6Al-4V alloy is reinforced with BNNT and processed at two different temperatures (750 and 950°C) to induce varying degrees of interfacial reactions. Real-time imaging of deformation, in conjunction with high-resolution chemical mapping, provides insights into the synergistic strengthening of the alloy due to interphases and BNNT present in the microstructure. The holistic understanding of microstructure evolution and mechanics of stress-transfer advanced by this dissertation will be helpful for engineering lightweight BNNT-MMCs with superior mechanical performance

NASA Tech Briefs, May 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Life cycle monitoring of composite aircraft components with structural health monitoring technologies

Life cycle monitoring could considerably improve the economy and sustainability of composite aircraft components. Knowledge about the quality of a component and its structural health allows thorough exploitation of it’s useful life and offers opportunity for optimization. Current life cycle monitoring efforts can be split in two main fields 1) process monitoring and 2) structural health monitoring with little overlap between them. This work aims to propose an integral monitoring approach, enabling entire life monitoring with the same sensor. First, the state of the art of both composite manufacturing as well as structural health monitoring technologies is presented. Piezoelectric sensors have been ruled out for further investigation due their brittleness. Fiber optical sensors and electrical property-based methods are further investigated. Distributed fiber optic sensors have been successfully used in composite manufacturing trials. Two processes were demonstrated: vacuum assisted resin transfer molding and resin infusion under flexible tooling. Due to their flexibility, optical fibers can survive the loads occurring during manufacturing and deliver valuable insights. It is shown for the first time numerically and experimentally, that fiber bed compaction levels and volume fractions can be calculated from the optical frequency shift measured by the optical fiber sensors. The same sensor was used for subsequent structural health monitoring. This proves that the gap between process monitoring and structural health monitoring can be closed with mutual benefits in both areas. The final chapter presents a novel electrical property-based sensing technique. The sensors are highly flexible and manufactured with a robot-based 3D-printing method. They are shown to reliably work as strain sensors and crack detectors. This work presents a thorough investigation of available and novel sensing technologies for process monitoring and structural health monitoring settings. The results obtained could pave the way to more efficient aircraft structures.Open Acces

Technology 2001: The Second National Technology Transfer Conference and Exposition, volume 1

Papers from the technical sessions of the Technology 2001 Conference and Exposition are presented. The technical sessions featured discussions of advanced manufacturing, artificial intelligence, biotechnology, computer graphics and simulation, communications, data and information management, electronics, electro-optics, environmental technology, life sciences, materials science, medical advances, robotics, software engineering, and test and measurement

Trapping and cooling of single molecular ions for time resolved experiments

In der vorliegenden Arbeit werden isolierte, einzeln ortsaufgelöste molekulare Ionen mit einer Femtosekundenspektroskopie auf der Basis von Einzelreaktionsereignissen untersucht. Für die zur simultanen Speicherung von atomaren und molekularen Ionen notwendige Radiofrequenzfalle wurde eine transportable Vakuumapparatur konzipiert und realisiert sowie die zugehörigen Lasersysteme aufgebaut und eingerichtet. Um die Ultrahochvakuumbedinungen bei 2e-10 mbar auch bei häufiger Molekülpräparation gewährleisten zu können, wurde ein modularer Aufbau gewählt, bei dem Präparations- und Expermentierbereich durch differentielle Pumpstrecken voneinander getrennt sind. Durch diese hindurch führt ein 48 cm langer Quadrupolionenleiter, in welchem Ionen zwischen den Kammern transferiert werden können. Entlang des Ionenleiters ermöglichen ringförmige Gleichspannungselektroden eine dreidimensionale Speicherung der Ionen. Im Rahmen dieser Arbeit wurde mit atomaren 24Mg+ und molekularen 24MgH+ Ionen gearbeitet. Erstere werden durch Photoionisation von Magnesiumatomen aus einem thermischen Strahl erzeugt und ihre Bewegungsenergie durch Laserkühlung soweit reduziert, dass sie in etwa 20 μm Abstand voneinander in einer kristallinen Struktur erstarren. Magnesiumhydridionen werden nach Einleiten von Wasserstoffgas in einer photochemischen Reaktion mit 24Mg+ generiert und – von verbleibenden atomaren Ionen sympathetisch gekühlt – auf Gitterplätze des Kristalls integriert. Bei der Laserkühlung von 24Mg+ ausgesendete Fluoreszenzphotonen ermöglichen die optische Detektion der Ionen mit derzeit bis zu 1 μm Ortsauflösung. Die nicht fluoreszierenden molekularen Ionen werden indirekt als vermeintlich unbesetzte Stellen der Kristallstruktur sichtbar. Neben der Demonstration des Erfolges unseres Fallenkonzepts sowie dessen Charakterisierung bildet der verlustfreie, kontrollierte Transport von atomaren und molekularen Ionen aus dem Präparations- in den Experimentierbereich, eine wichtige Errungenschaft, welche zu einem kontinuierlichen Nachladen von Ionen mit einer Rate von über 100 Hz ausgebaut werden kann. Diese Arbeit präsentiert eine Machbarkeitsstudie zur Kombination von Präzisionsmethoden zweier Forschungsgebiete. Dazu wurde die Fallenapparatur mit einem weiteren Vakuumsystem, in dem ultraviolette Femtosekundenpulse erzeugt werden können, über ein System von differenziellen Pumpstrecken verbunden. Als Resultat werden 5 fs zeitaufgelöste Pump-Probe Experimente vorgestellt, die die Oszillation eines Vibrationswellenpaketes von individuellen 24MgH+ Molekülionen zeigen. Dabei wird die Bewegung des Wellenpaketes auf die Dissoziationswahrscheinlichkeit in einem bestimmten Zerfallskanal abgebildet. Einzelne Reaktionsereignisse konnten eindeutig nachgewiesen und daraus das zeitabhängige Verhalten extrahiert werden. Diese Resultate untermauern das Potenzial der von uns angestrebten Kombination der exzellenten Kontrolle über externe und interne Freiheitsgrade gespeicherter Ionen mit der extremen Zeitauflösung von modernen Kurzpulslasern. Weitere Arbeiten können die Vorteile beider Gebiete nutzen um bisher unzugängliche Experimente zu realisieren. Die besonderen Eigenschaften der präsentierten Apparatur sollten es beispielsweise erlauben, einzelne isolierte molekulare Ionen mit hoher räumlicher Präzision und wohl kontrollierten Anfangsbedingungen für zukünftige Strukturuntersuchungen mittels derzeit entstehender, intensiver Kurzpuls-Röntgenquellen an freien Elektronenlasern bereitzustellen

Environmental-(S)TEM of dynamic Catalyst Nanostructures

The production of intelligently designed catalysts requires an understanding of, not only the specific reaction pathways, but also the effects of reactive species on catalyst materials. Gas composition, temperature and pressure can alter the physical characteristics of a catalyst material. The size, shape, crystallographic topography, chemical state and material composition of catalytic nanostructures can be highly dynamic under reaction conditions. E(S)TEM is uniquely suited to observe the structure of nanomaterials in real time under simulated reaction conditions. The oxidation of Ni nanoparticles was investigated using dynamic in-situ imaging in ETEM. These observations show a change in reaction mechanism as the Ni-NiO structure evolves over the course of the reaction. Initially, pyramidal NiO crystals grow on the Ni surface. The overlap and outward growth of these crystallites leads to an oxide shell around a metallic core. At a critical oxide thickness, the mechanism switches and further structural transformations are observed due to differential diffusion. Fast diffusion of cation vacancies lead to the formation of Kirkendall voids and ultimately hollow NiO structures. Nanoparticle based catalysts for industrial methanation reactions were studied using ESTEM. The study focuses on the origin of enhanced catalytic activity via the addition of a ceria promoter. Oxygen vacancies at the ceria surface were found to be active sites for the activation of carbon oxides. A correlation was found between decreasing promoter crystallite size and the enhancement of catalytic activity. The best promotional effect was observed when the ceria takes the form of a highly dispersed atomic-scale species. E(S)TEM was used to observe the evolution of Pd nanoparticles under redox conditions. Pd model systems utilising carbon, silica and alumina supports were tested. The amount of sintering was found to be determined by both: gas environment and the support material

a tumblr book

"This book takes an extensive look at the many different types of users and cultures that comprise the popular social media platform Tumblr. Though it does not receive nearly as much attention as other social media such as Twitter or Facebook, Tumblr and its users have been hugely influential in creating and shifting popular culture, especially progressive youth culture, with the New York Times referring to 2014 as the dawning of the “age of Tumblr activism.”   Perfect for those unfamiliar with the platform as well as those who grew up on it, this volume contains essays and artwork that span many different topics: fandom; platform structure and design; race, gender and sexuality, including queer and trans identities; aesthetics; disability and mental health; and social media privacy and ethics. An entire generation of young people that is now beginning to influence mass culture and politics came of age on Tumblr, and this volume is an indispensable guide to the many ways this platform works.