Rainer Adelung

Christian-Albrechts-Universität zu Kiel, Kiel, Schleswig-Holstein, Germany

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Publications (139)575.35 Total impact

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    ABSTRACT: Since the prohibition of tributyltin (TBT)-based antifouling paints in 2008, the development of environmentally compatible and commercially realizable alternatives is a crucial issue. Cost effective fabrication of antifouling paints with desired physical and biocompatible features are simultaneously required and recent developments in the direction of inorganic nanomaterials could play major role. In the present work, a solvent free polymer/particle-composite coating based on two component polythiourethane (PTU) and tetrapodal shaped ZnO (t-ZnO) nano- and microstructures has been synthesized and studied with respect to mechanical, chemical and biocompatibility properties. Furthermore, antifouling tests have been carried out in artificial seawater tanks. Four different PTU/t-ZnO composites with various t-ZnO filling fractions (0 wt%, 1 wt%, 5 wt%, 10 wt%) were prepared and the corresponding tensile, hardness, and pull-off test results revealed that the composite filled with 5 wt% t-ZnO exhibits the strongest mechanical properties. Surface free energy (SFE) studies using contact angle measurements showed that the SFE value decreases with increase in t-ZnO filler amounts. The influence of t-ZnO on the polymerization reaction was confirmed by Fourier transformed infrared-spectroscopy measurements and thermogravimetric analysis. The immersion tests demonstrated that fouling behavior of PTU/t-ZnO composite with 1 wt% t-ZnO filler has been decreased in comparison to pure PTU. The composite with 5 wt% t-ZnO filler showed almost no biofouling.
    No preview · Article · Feb 2016 · Physical Chemistry Chemical Physics

  • No preview · Article · Dec 2015 · physica status solidi (RRL) - Rapid Research Letters
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    Full-text · Dataset · Nov 2015
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    ABSTRACT: Aerographite (AG) is a mechanically robust, lightweight synthetic cellular material, which consists of a 3D interconnected network of tubular carbon [1]. The presence of open channels in AG aids to infiltrate them with polymer matrices, thereby yielding an electrical conducting and lightweight composite. Aerographite produced with densities in the range of 7–15 mg/cm3 was infiltrated with a low viscous epoxy resin by means of vacuum infiltration technique. Detailed morphological and structural investigations on synthesized AG and AG/epoxy composite were performed by scanning electron microscopic techniques. The present study investigates the fracture and failure of AG/epoxy composites and its energy absorption capacity under compression. The composites displayed an extended plateau region when uni-axially compressed, which led to an increase in energy absorption of ∼133% per unit volume for 1.5 wt% of AG, when compared to pure epoxy. Preliminary results on fracture toughness showed an enhancement of ∼19% in KIC for AG/epoxy composites with 0.45 wt% of AG. Observations of fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite failure as the dominating mechanism for the toughness improvement in these composites. These observations were consistent with the results obtained from photoelasticity experiments on a thin film AG/epoxy model composite.
    No preview · Article · Nov 2015 · Composites Science and Technology
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    Full-text · Dataset · Oct 2015
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    I Hölken · M Hoppe · R Adelung · M Baum

    Full-text · Dataset · Oct 2015
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    Full-text · Dataset · Oct 2015
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    ABSTRACT: Copper oxides nanostructures are fascinating nanomaterials due to their remarkable electrical, optical, thermal and sensing properties given that their tunability and the stabilization of specific phases are uniquely possible at the nanoscale dimensions. The present study reports on nano-crystalline copper oxide thin films via a simple synthesis (SCS) from chemical solutions followed by two types of thermal annealing, namely rapid thermal annealing (RTA) and conventional thermal annealing (TA). We report on enhanced ethanol sensing performances of the device structures based on synthesized one and two distinctly different phases of copper oxides nanocrystals, namely Cu2O, CuO, as well as mixed phases of CuO and Cu2O. A gradient in phase change was observed for annealed samples starting from CuO on the top of nano-crystals to Cu2O in their central region. RTA effects on the gas response of the CuxOy nano-crystals have been identified as unprecedented selectivity and sensitivity to ethanol vapours at different temperatures. An increase in resistance value of about one order in magnitude was detected for samples treated by conventional-TA at 400˚C for 30 min at optimal operating temperature of 300˚C and RTA at 525˚C for 60 s at lower optimal operating temperature of 275˚C. It was found that the response and recovery times for pure copper oxide–based sensors can be significantly decreased by Zn-doping, e.g. from ~4.1 s and ~10.5 s to about 3.3 s and 7.2 s, respectively. The obtained results provide an exciting alternative to fast, sensitive and selective detection of trace gases, which would be of particular benefit in the area of public security and environmental applications.
    Full-text · Article · Oct 2015 · Sensors and Actuators B Chemical
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    I Hölken · S Schröder · R Adelung
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    ABSTRACT: Hollow inorganic microstructures have gained much interest in nowadays research fields as they offer unique properties (high specific area, thermal conductivity or density) when compared to their bulk equivalents 1. On the other hand, for many applications, e.g. as anode material in lithium ion batteries 2 , crystalline silicon microstructures (c-Si) would be of great interest. The development of thin hollow Si microparticles based on t-ZnO would therefore offer a new class of Si structures which are of special interest as they combine suitable physico-chemical properties with high porosity caused by their special morphology. One approach for the realization of these Si microstructures includes the usage of plasma enhanced chemical vapor deposition based on argon diluted silane source gases as it provides the opportunity to fabricate homogeneous nanolayers at relatively low temperatures. In order to obtain the desired morphology combined with an adequate deposition rate, in this work the process was optimized by parameter variations and subsequent investigations of the films by Raman spectroscopy, scanning electron microscopy and profilometry. First experiments for the deposition of Si onto t-ZnO were implemented and promising results were obtained.
    Full-text · Conference Paper · Oct 2015
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    I Hölken · M Hoppe · R Adelung · M Baum
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    ABSTRACT: The worldwide increasing number of offshore wind turbines brings along the need for innovative polymer coatings which on the one hand can withstand the extreme forces acting on the rotor blades and on the other hand can provide adequate antifouling properties to counter biocorrosion of the basement. The development of environmentally friendly and commercially realizable coating systems is most important since the prohibition of tributyltin (TBT)-based antifouling coatings in 2008. In this study an alternative polymer/particle composite coating based on polythiurethan (PTU) with tetrapodal shaped ZnO (t-ZnO) as additive is investigated with respect to chemical, mechanical and antifouling properties. Overall, four different composites with filler amounts of 0 wt% t-ZnO, 1 wt% t-ZnO, 5 wt% t-ZnO, 10 wt% t-ZnO were tested. Preliminary antifouling experiments were carried out under artificial habitat conditions at an aquarium, imitating Pacific Sea water. For mechanical and chemical characterization tensile tests, adhesion tests and contact angle measurements were performed. An optimum of mechanical and antifouling properties were found for a filler amount of 5 wt% t-ZnO in PTU.
    Full-text · Conference Paper · Oct 2015
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    ABSTRACT: Enhanced performances were obtained for nanosensors based on a single nanowire of silver-doped zinc oxide (ZnO:Ag). Arrays of crystalline ZnO:Ag nanowires were synthesized by electrodeposition on F-doped tin oxide coated substrates and studied by SEM, EDX, TEM, HRTEM, SIMS, XPS, PL and micro-Raman spectroscopy. Integration of a single nanowire or a single microwire on the chip was performed by employing metal maskless nanodeposition in the dual beam focused electron/ion beam instrument. The ultraviolet (UV) response and hydrogen (H2) gas response were studied for nanodevices and microdevices based on a single ZnO:Ag nanowire. We found that ZnO:Ag nanowire based nanosensor possesses a much faster response/recovery time and a higher response to UV radiation and hydrogen gas (∼50%) than those reported in literature. An increase in current value of about two orders in magnitude IUVON/IUVOFF was observed under exposure to UV light. Faster response/recovery times of about 0.98 s/0.87 s were observed. The ZnO:Ag nanowires and microwires can serve as nano-building materials for ultrasensitive and ultra-fast sensors with reduced power consumption. The mechanisms for such improved responses to UV and H2 were discussed. The developed nanomaterial is of great scientific interest for further studies as promising candidates for fabricating multifunctional nano-sensors, LEDs and photodetectors by bottom-up and hybrid nanotechnologies.
    Full-text · Article · Oct 2015 · Sensors and Actuators B Chemical
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    ABSTRACT: This paper reports on the characterization of the electrochemical growth process of magnetic nanowires in ultra-high-aspect ratio InP membranes via in situ fast Fourier transform impedance spectroscopy in a typical frequency range from 75 Hz to 18.5 kHz. The measured impedance data from the Ni, Co, and FeCo can be very well fitted using the same electric equivalent circuit consisting of a series resistance in serial connection to an RC-element and a Maxwell element. The impedance data clearly indicate the similarities in the growth behavior of Ni, Co and FeCo nanowires in ultra-high aspect ratio InP membranes—the beneficial impact of boric acid on the metal deposition in ultra-high aspect ratio membranes and the diffusion limitation of boric acid, as well as differences such as passivation or side reactions.
    Full-text · Article · Oct 2015 · Semiconductor Science and Technology
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    Oleg Lupan · L. Chow · Thierry Pauporté · B. Viana · R. Adelung

    Full-text · Conference Paper · Sep 2015
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    J. Carstensen · J.-M. Wagner · A. Schütt · R. Adelung
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    ABSTRACT: Lateral balancing currents are an immanent feature of solar cells with an inhomogeneous distribution of photocurrent Iph(x,y) and/or diode current j01(x,y) leading to additional power losses and thus to a significant increase of difficulty to analyze local efficiencies of solar cells. Due to fundamental physical restrictions like charge conservation and having a potential distribution across a 2D grid network, astonishingly only the histogram information (no local information!) of images of recombination strength and series resistance is needed to calculate all relevant average information. This is completely analogous to the technique of frequency analysis used for code breaking used for more than 1000 years where just a histogram analysis allows to identify the meaning and the position of all (most) characters within a text. In this contribution, the theory and quantitative results for several inhomogeneous solar cells with different kinds of lateral balancing currents are presented.
    Full-text · Conference Paper · Sep 2015
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    ABSTRACT: Stretchable three-dimensional ceramic networks constructed from quasi-one-dimensional metal oxide nanostructures are versatile candidates for using nanoscopic structures in everyday technologies. The growth of such networks built from SnO2 nanostructures is realized by a simple flame transport synthesis. As reported by Lorenz Kienle, Rainer Adelung, Yogendra Kumar Mishra, and co-workers in article number 1500081, these grown SnO2 nanostructures with unique structural defects can be used for sensing applications.
    No preview · Article · Aug 2015
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    ABSTRACT: A viable lightweight absorber is the current need for stealth technology as well as microwave absorption. Several microwave absorbers have been developed, but it is still a challenge to fabricate such an absorber that facilitates microwave absorption in broad bandwidth or cover the maximum portion of the frequency range 2-18 GHz which is commonly used for radar and other applications. Therefore, it is highly required to develop a wide bandwidth absorber that can provide microwave absorption in the most part of the frequency range 2-18 GHz while simultaneously being lightweight and can be fabricated in bulk quantities by a low cost production method. Therefore, in this paper, an attempt has been made to design an ultra-wide bandwidth absorber with enhanced microwave absorption by using nickel-phosphorus coated tetrapod-shaped ZnO (Ni-P coated T-ZnO). In this Ni-P coated T-ZnO absorber, ZnO acts as a good dielectric contributor while Ni as a magnetic constituent to obtain a composite microwave absorbing material which is having favorable absorption properties. Ni-P coated ZnO nano-microstructures are synthesized by a simple and scalable two-step process; First, tetrapod-shaped ZnO (T-ZnO) have been grown by flame transport synthesis (FTS) approach in a single step process and then they have been coated with Ni-P by electroless coating technique. Their morphology, degree of crystallinity and existing phases were studied in detail by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The complex permittivity and permeability of the “as-fabricated” T-ZnO and Ni-P coated T-ZnO have been measured in the frequency range of 4–14 GHz and their microwave absorption properties are computed with coaxial transmission-reflection method. The strongest reflection loss (RL) peak value of -36.41 dB has been obtained at a frequency of 8.99 GHz with an absorber thickness of 3.4 mm for the Ni-P coated T-ZnO sample with a broad bandwidth of 10.0 GHz (RL < -10 dB) in the frequency range of 4.0 GHz to 14.0 GHz.
    Full-text · Article · Aug 2015 · Physical Chemistry Chemical Physics
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    Full-text · Dataset · Jun 2015
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    ABSTRACT: Research on semiconducting oxide nanocrystals will likely remain one of the leading topics in condensed matter physics and advanced functional materials. Looking beyond this field, chemically heterogeneous nanocrystals systems based on mixed phases have been assembled as reported here for shell-core Ga2O3/GaN:Ox@SnO2 nanocables, i. e. long and single crystalline SnO2 belts/wires as core surrounded with a shell composed of GaN:Ox and Ga2O3 nanoparticles. Subsequently, nano- and micro-sensors from an individual shell-core Ga2O3/GaN:Ox@SnO2 nanocable on the chip have been realized via localized maskless growth of metal using dual-beam FIB-SEM instrument. In contrast to pure SnO2 nanowire-based sensor, here fabricated nano- and micro-devices on individual hybrid nano- or micro-cables on chip are quite stable, highly sensitive (the current ratio IUVON/IOFF > 104), higher and faster switching in UV photodetection, as well as air/vacuum and temperature sensing capabilities. The SnO2 nano- and microbelts/wires networks were synthesized by the flame transport synthesis and a shell layer composed of Ga2O3/GaN:Ox nanoparticle was deposited on them by magnetron sputtering. The scanning electron microscopy and transmission electron microscopy results revealed that the Ga2O3/GaN:Ox nanocrystallite shells are uniformly deposited on SnO2 networks. The detailed TEM structural studies on the as-grown and annealed structures confirmed that the nanocable is made from mixed phases by an excellent agreement with the standard data for rutile SnO2, amorphous GaN:Ox and monoclinic β-Ga2O3. Herein, we resolve two essential problems regarding the nano-construction of an efficient nanosensor. First, the simplest process fabrication of the highly protected shell-core nanocables with improved electrical properties is achieved by cost-effective synthesis in a controlled manner. Second, construction of a non-planar 3D nanoscale double-heterojunctions with a large surface area is realized via an efficient technique. It allows surface protection of nanosensors during its fabrication and operation in different ambient conditions. The developed nanomaterial sparks interest for further studies on different hybrid semiconducting oxides as promising candidates for fabricating multifunctional nano- and micro-sensors and photodetectors.
    Full-text · Article · Jun 2015 · Sensors and Actuators B Chemical
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    Full-text · Dataset · Jun 2015
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    Full-text · Dataset · Jun 2015

Publication Stats

2k Citations
575.35 Total Impact Points

Institutions

  • 1998-2015
    • Christian-Albrechts-Universität zu Kiel
      • • Institute for Materials Science
      • • Institute of Experimental and Applied Physics (IEAP)
      • • Chair of Multicomponent Materials
      • • Faculty of Engineering
      • • Institut für Theoretische Physik und Astrophysik
      Kiel, Schleswig-Holstein, Germany
  • 2014
    • Friedrich Schiller University Jena
      Jena, Thuringia, Germany
  • 2010
    • University Medical Center Schleswig-Holstein
      Kiel, Schleswig-Holstein, Germany
  • 2002-2004
    • Case Western Reserve University
      • Department of Materials Science and Engineering
      Cleveland, Ohio, United States
    • University of Hamburg
      • Institute of Applied Physics
      Hamburg, Hamburg, Germany