Eigenschaften von Polymer-Silber-Nanokompositen hergestellt durch Co-Sputtern

In dieser Arbeit wurden Polymer-Metall-Nanokomposite durch gleichzeitiges Sputtern von Silber und Polymeren aus zwei unabhängigen Magnetron-Sputterquellen hergestellt. Durch die vernetzte Struktur und die dielektrischen Eigenschaften eignet sich PTFE zur Verwendung als Matrixmaterial. Der Metallgehalt der Kompositfilme wurde über die Messung von EDX-Intensitäten ermittelt. Die Größe der Nanopartikel wurde mit Hilfe von TEM und XRD bestimmt und liegt im Bereich von 10 nm. Die Kompositmaterialien zeigen an der Perkolationsgrenze einen schlagartigen Übergang der Eigenschaften vom polymer- zum metallähnlichen Verhalten. Der spezifische Widerstand fällt in einem Bereich zwischen 35 und 40 % Silbergehalt um mindestens neun Größenordnungen ab. Die optischen Eigenschaften ändern sich mit dem Metallgehalt. Die durch Plasmonenresonanz verursachte Absorption, die bei kleinen Füllgraden bei ca. 400 nm ihr Maximum hat und eine intensive gelbe Farbe des Kompositmaterials zur Folge hat, verschiebt sich mit zunehmendem Silbergehalt zu längeren Wellenlängen. Die Unterschiede im optischen Verhalten der Nanokomposite und der reinen Polymere lässt sich bei der Herstellung von Bragg-Reflektoren ausnutzen. Leichte Änderungen im Metallgehalt können bei den Polymer-Silber-Nanokompositen im Bereich der Perkolationsschwelle also eine drastische Änderung in den Eigenschaften bewirken, wodurch Anwendungen als Sensoren denkbar sind

Electrical properties of an amorphous zirconium oxide thin film and structure formation during crystallization

Metastable amorphous oxides with a strong oxygen deficiency often show surprising phenomena upon relaxation into thermodynamically stable phases. For example, Nagarajan et al. found a new type of chemically driven insulator-metal transition in highly non-stoichiometric gallium oxide films (GaOx).[1] Here, an internal solid-state disproportionation reaction leads to the growth Ga2O3 nuclei in the initially insulating GaOx matrix which thereby attains metal-like conductivity. Moreover, it has been recently shown that such films can act as memristive switches. [2]. Highly non-stoichiometric titania (TiO1.6) films show a similar disproportionation reaction upon heating but as the phase diagram for this material is more complex, various phases can be found during the relaxation [3]. Please click Additional Files below to see the full abstract

Distinguishing the Rhombohedral Phase from Orthorhombic Phases in Epitaxial Doped HfO2 Ferroelectric Films

Epitaxial strain plays an important role in the stabilization of ferroelectricity in doped hafnia thin films, which are emerging candidates for Si-compatible nanoscale devices. Here, we report on epitaxial ferroelectric thin films of doped HfO2 deposited on La0.7Sr0.3MnO3-buffered SrTiO3 substrates, La0.7Sr0.3MnO3 SrTiO3-buffered Si (100) wafers, and trigonal Al2O3 substrates. The investigated films appear to consist of four domains in a rhombohedral phase for films deposited on La0.7Sr0.3MnO3-buffered SrTiO3 substrates and two domains for those deposited on sapphire. These findings are supported by extensive transmission electron microscopy characterization of the investigated films. The doped hafnia films show ferroelectric behavior with a remanent polarization up to 25 μC/cm2 and they do not require wake-up cycling to reach the polarization, unlike the reported polycrystalline orthorhombic ferroelectric hafnia films

First evidence for the forging of gold in an Early Bronze Age Site of Central Europe (2200–1800 BCE)

Evidence of gold processing in the fortified site of Bruszczewo (Poland) is the first testimony of the production of gold artefacts in a domestic Early Bronze Age site of Central Europe. This paper highlights the potential of macrolithic tool ensembles as a key element for the recognition of metallurgical work processes. Moreover, it presents an optimised methodological approach to tackle the application of stone tools in metallurgical production, based on technological characterisation, use-wear analysis, portable X-ray fluorescence, transmission electron microscopy and energy dispersive X-ray spectroscopy. Finally, the absence of gold sources in Central Europe raises the question about the origin of the metal, constituting an especially striking issue, as gold was a raw material of restricted access. As Bruszczewo was one of the few enclosed Early Bronze Age sites north of the Central European Mountain Range, the patterning of metal processing (including gold) sheds light on the mode of the production of metal artefacts, apparently restricted to central sites of power, which controlled the communication trails.47Journal of Archaeological Science: Report

Synthesis and Nanostructure Investigation of Hybrid β-Ga2 O3 /ZnGa2 O4 Nanocomposite Networks with Narrow-Band Green Luminescence and High Initial Electrochemical Capacity

The material design of functional "aero"-networks offers a facile approach to optical, catalytical, or and electrochemical applications based on multiscale morphologies, high large reactive area, and prominent material diversity. Here in this paper, the synthesis and structural characterization of a hybrid β-Ga2 O3 /ZnGa2 O4 nanocomposite aero-network are presented. The nanocomposite networks are studied on multiscale with respect to their micro- and nanostructure by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and are characterized for their photoluminescent response to UV light excitation and their electrochemical performance with Li-ion conversion reaction. The structural investigations reveal the simultaneous transformation of the precursor aero-GaN(ZnO) network into hollow architectures composed of β-Ga2 O3 and ZnGa2 O4 nanocrystals with a phase ratio of ≈1:2. The photoluminescence of hybrid aero-β-Ga2 O3 /ZnGa2 O4 nanocomposite networks demonstrates narrow band (λem = 504 nm) green light emission of ZnGa2 O4 under UV light excitation (λex = 300 nm). The evaluation of the metal-oxide network performance for electrochemical application for Li-ion batteries shows high initial capacities of ≈714 mAh g-1 at 100 mA g-1 paired with exceptional rate performance even at high current densities of 4 A g-1 with 347 mAh g-1 . This study provides is an exciting showcase example of novel networked materials and demonstrates the opportunities of tailored micro-/nanostructures for diverse applications a diversity of possible applications

Co‐sputtering of A Thin Film Broadband Absorber Based on Self‐Organized Plasmonic Cu Nanoparticles

The efficient conversion of solar energy to heat is a prime challenge for solar thermal absorbers, and various material classes and device concepts are discussed. One exciting class of solar thermal absorbers are plasmonic broadband absorbers that rely on light absorption thanks to plasmonic resonances sustained in metallic nanoparticles. This work focuses on Cu/Al$_2$O$_3$ plasmonic absorbers, which consist of a thin film stack of a metallic Cu-mirror, a dielectric Al$_2$O$_3$ spacer, and an Al$_2$O$_3$/Cu-nanoparticle nanocomposite. This work explores two preparation routes for the Al$_2$O$_3$/Cu-nanoparticle nanocomposite, which rely on the self-organization of Cu nanoparticles from sputtered atoms, either in the gas phase (i.e., via gas aggregation source) or on the thin film surface (i.e., via simultaneous co-sputtering). While in either case, Cu-Al$_2$O$_3$-Al$_2$O$_3$/Cu absorbers with a low reflectivity over a broad wavelength regime are obtained, the simultaneous co-sputtering approach enabled better control over the film roughness and showed excellent agreement with dedicated simulations of the optical properties of the plasmonic absorber using a multi-scale modeling approach. Upon variation of the thickness and filling factor of the Al$_2$O$_3$/Cu nanocomposite layer, the optical properties of the plasmonic absorbers are tailored, reaching an integrated reflectance down to 0.17 (from 250 to 1600 nm)

Technical feasibility study for production of tailored multielectrode arrays and patterning of arranged neuronal networks

Schürmann M, Shepheard N, Frese N, et al. Technical feasibility study for production of tailored multielectrode arrays and patterning of arranged neuronal networks. PLOS ONE. 2018;13(2): e0192647.In this manuscript, we first reveal a simple ultra violet laser lithographic method to design and produce plain tailored multielectrode arrays. Secondly, we use the same lithographic setup for surface patterning to enable controlled attachment of primary neuronal cells and help neurite guidance. For multielectrode array production, we used flat borosilicate glass directly structured with the laser lithography system. The multi layered electrode system consists of a layer of titanium coated with a layer of di-titanium nitride. Finally, these electrodes are covered with silicon nitride for insulation. The quality of the custom made multielectrode arrays was investigated by light microscopy, electron microscopy and X-ray diffraction. The performance was verified by the detection of action potentials of primary neurons. The electrical noise of the custom-made MEA was equal to commercially available multielectrode arrays. Additionally, we demonstrated that structured coating with poly lysine, obtained with the aid of the same lithographic system, could be used to attach and guide neurons to designed structures. The process of neuron attachment and neurite guidance was investigated by light microscopy and charged particle microscopy. Importantly, the utilization of the same lithographic system for MEA fabrication and poly lysine structuring will make it easy to align the architecture of the neuronal network to the arrangement of the MEA electrode.. In future studies, this will lead to multielectrode arrays, which are able to specifically attach neuronal cell bodies to their chemically defined electrodes and guide their neurites, gaining a controlled connectivity in the neuronal network. This type of multielectrode array would be able to precisely assign a signal to a certain neuron resulting in an efficient way for analyzing the maturation of the neuronal connectivity in small neuronal networks

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Die Ausstellung „Osmanen in Hamburg – eine Beziehungsgeschichte zur Zeit des Ersten Weltkrieges“, die vom 6. November 2014 bis zum 4. Januar 2015 in der Staats- und Universitätsbibliothek Carl von Ossietzky gezeigt wurde, widmete sich anlässlich des 100. Jahrestages der „Urkatastrophe“ den deutsch-osmanischen Beziehungen aus Hamburger Sicht und nahm vor allem die Zeit zwischen 1914 und 1918 in den Blick. Die erstmals gezeigten Archivmaterialien veranschaulichen dabei nicht nur die wirtschaftlichen, diplomatischen und kulturellen Kontakte. Sie vermitteln vor allem einen Eindruck von der Präsenz und vom Leben der ethnisch wie religiös heterogenen Gruppe der Osmanen (u. a. Armenier, Griechen, sephardische Juden, muslimische Türken) in Hamburg, deren Spuren sich bis ins 19. Jahrhundert zurückverfolgen lassen. Der vorliegende Katalog möchte aber nicht nur die in acht Sektionen unterteilte Ausstellung dokumentieren. Er liefert mit zusätzlichen acht Beiträgen einen weiterführenden Einblick in die komplexe und ambivalente osmanisch-deutsche bzw. hamburgisch-osmanische Beziehungsgeschichte. In drei Kapiteln werden neben den transkulturellen Begegnungen wie Kulturdifferenzen der Zeit von etwa 1850 bis 1909, die kolonialen Ambitionen und orientalistischen Embleme des Deutschen Reiches, aber auch die Rolle deutscher Frauen im Osmanischen Reich zwischen 1914 und 1918 beleuchtet.The exhibition "Osmanen in Hamburg - a relationship history during the First World War" which was shown in the Hambrug State and University Library from November 6th, 2014 to January 4th, 2015, devoted itself to the 100th anniversary of the "Urkatastrophe" (the Great War) to he German-Ottoman relations from the perspective of Hamburg, and focused on the years between 1914 and 1918. The archival objects were presented for the first time and are documented in this publication. They illustrate not only economic, diplomatic and cultural contacts., but also give an impression of the presence and the life of the ethnically and religiously heterogeneous group of the Ottomans (e.g. Armenians, Greeks, Sephardic Jews, Muslim Turks) in Hamburg who can be traced back to the 19th century. This catalog, however, does not only want to document the exhibition which was divided into eight sections. With an additional eight contributions, it provides a deeper insight into the complex and ambivalent Ottoman-German and/ or Hamburg-Ottoman relations. In addition to transcultural encounters such as cultural differences between the time of 1850 and 1909 the colonial ambitions and oriental emblems of the German Reich, as well as the role of German women in the Ottoman Empire between 1914 and 1918, are illuminated in three chapters