Zur Beständigkeit beschichteter Holzspanwerkstoffe

Materials, based on, wood particles, such as particleboards and moulded wood particle materials, are mainly used in a coated state for building purposes. In our laboratories investigations have been carried out to determine the service life of these composite materials, by means of accelerated weathering method. For this purpose, different liquid or solid-coated materials were used. The tests aimed at comparing open-air weathering with a short-term weathering test, which has been developed in our laboratory, based on the so-called Xenotest method. Among the liquid coatings, those lacquers based on pigmented polyurethanes turned out to be superior to all other competing systems. Solid coatings, made of pure melamine-formaldehyde resins showed to be very resistant against weathering. 48 to 60 weeks exposure in a Xenotest weathering apparatus seem to be sufficient to simulate 10 years of open-air exposure not only for uncoated but also for coated wood particle materials.     

Correction to: Co-sputtering of Al1−xScxN thin films on Pt(111): a characterization by Raman and IR spectroscopies

Journal of Materials Science -     

Quantum Criticality and Scaling of the Magnetic Response in CeCu6−x Au x

The heavy-fermion system CeCu_6?x Au _x which exhibits antiferromagnetic order for Au concentrations x>0.1, can be easily tuned to a quantum phase transition, either by chemical composition, i.e., Au concentration, or by an external magnetic field. We present extensive inelastic neutron scattering measurements in order to study the momentum and energy dependence of the critical spin fluctuations for concentration- and magnetic field-tuned CeCu_6?x Au _x . The quasi-2D fluctuations, observed for x=0.1 at the magnetic instability, are already present in pure CeCu₆ and persist to x=0.2, i.e., well into the magnetically ordered regime. This is a strong hint that disorder does not play a major role in this system. The magnetic response for quantum critical CeCu_6?x Au _x exhibits critical slowing down and obeys scaling relations that depend on the tuning parameter. While the E/T scaling of the dynamic susceptibility in concentration-tuned CeCu_5.9Au_0.1 is an indication for local quantum criticality, the E/T ^3/2 scaling in field-tuned CeCu_5.8Au_0.2 points to a conventional spin-density-wave instability.     

Integration of Radioactive Material with Microcalorimeter Detectors

Microcalorimeter detectors with embedded radioactive material offer many possibilities for new types of measurements and applications. We will discuss the designs and methods that we are developing for precise deposition of radioactive material and its encapsulation in the absorber of transition-edge sensor (TES) microcalorimeter detectors for two specific applications. The first application is total nuclear reaction energy (Q) spectroscopy for nuclear forensics measurements of trace actinide samples, where the goal is determination of ratios of isotopes with Q values in the range of 5–7 MeV. Simplified, rapid sample preparation and detector assembly is necessary for practical measurements, while maintaining good energy resolution. The second application is electron capture spectroscopy of isotopes with low Q values, such as \(^{163}\) Ho, for measurement of neutrino mass. Detectors for electron capture spectroscopy are designed for measuring energies up to approximately 6 keV. Their smaller heat capacity and physical size present unique challenges. Both applications require precise deposition of radioactive material and encapsulation in an absorber with optimized thermal properties and coupling to the TES. We have made detectors for both applications with a variety of designs and assembly methods, and will present their development.     

Direct Imaging of Space‐Charge Accumulation and Work Function Characteristics of Functional Organic Interfaces

The tailoring of organic systems is crucial to further extend the efficiency of charge transfer mechanisms and represents a cornerstone for molecular device technologies. However, this demands control of electrical properties and understanding of the physics behind organic interfaces. Here, a quantitative spatial overview of work function characteristics for phthalocyanine architectures on Au substrates is provided via kelvin probe microscopy. While macroscopic investigations are very informative, the current approach offers a nanoscale spatial rendering of electrical characteristics which is not possible to attain via conventional techniques. Interface dipole is observed due to the formation of charge accumulation layers in thin F₁₆CuPc, F₁₆CoPc, and MnPc films, displaying work functions of 5.7, 6.1, and 5.0 eV, respectively. The imaging and quantification of interface locations with significant surface potential and work function response (<0.33 eV for material thickness <1 nm) show also a dependency on the crystalline state of the organic systems. The work function mapping suggests space‐charge carrier regions of about 4 nm at the organic interface. This reveals rich spatial electric parameters and ambipolar characteristics that may drive electrical performance at device scales, opening a realm of possibilities toward the development of functional organic architectures and its applications.     

Verfahren zur Erstellung auswertbarer Bildvorlagen für mikrovisioplastische Untersuchungen

The mechanical properties of polycristalline materials are depent on the type, the combination and the orientation of the elements in the micro structure. By means of the method of Visioplasticity assumptions are currently realized to analyse kinematic parameters inside of single grains and grain groups. Strength of the free surface of the specimen will be rough by its plastical deformation, it was difficult to register the increments of deformation of the grid. By further development of a method of picture analysis it is also possible to reproduce a 3d-surface by utilization of single light microscopical pictures.     

Schädigungsentwicklung der Legierung IN 738 LC bei Hochtemperatur-LCF-Beanspruchung

Damage evolution of the alloy IN 738 LC at high temperature low cycle fatigue Herrn Professor K.-T. Rie zum 60. Geburtstag Interrupted Low-Cycle-Fatigue tests have been carried out with IN 738 LC at 850°C. The specimens were extensively examined by SEM to quantify the evolution of fatigue damage. Surface crack nucleation at oxidized grain boundaries occured during the whole experiments. The coalescence of cracks was the dominant mechanism which lead to macro crack evolution and the final fracture.     

Alkali Extraction of Starch from Corn Flour

The alkali steeping process was tested for extraction of starch from degerminated yellow corn flour. The effect of three process parameters, alkali concentration (0.1 and 0.4%), steep temperature (25 and 55°C) and steep time (30 and 90min) were evaluated for their effect on yield, protein and sodium contents of starch. Two-level full factorial design was used to investigate the process. The experimental results indicated that starch yield increased with increasing steep temperature and at low alkali concentration. All main effects and interactions were found to have significant effect on protein content in the extracted starch. The sodium content of the starch was effected by the three main effects and the three two-factor interaction effects. Conditions were identified that simultaneously produced a high starch yield, low protein and sodium contents were 0.1% alkali steep at 55°C for 30 min.