Leptinotarsa decemlineata SAY

Durch direkte Ableitung der Nervenaktionsströme von Sinneshaaren können beim Kartoffelkäfer an den Tarsen und Palpen Schmeckhaare von Haaren mit Tastvermögen differenziert werden. Das Erregungsmuster der Schmeckhaare ist von der Art des Reizstoffes abhängig

Atmosphere monitoring in a continuous sintering belt furnace

The atmosphere composition in a continuous belt furnace during sintering of powder metallurgical aluminium components with ethylenbisstearamide (EBS) pressing agent was determined by Fourier Transform Infrared Spectroscopy (FTIR). The spatial distribution of the decomposition products was measured at four positions in the dewaxing zone. It is shown that the major decomposition products of the dewaxing process are CH groups, which mainly occur between 310 and 410 degrees C. As the powder compacts pass the dewaxing zone, each part drags along its own bell-shaped gas atmosphere. In the vertical direction, a flow profile with two separated concentration zones is observed, leading to large quantities of unused process gas passing the furnace. The amount of unused gas is mainly controlled by the gas flow and the belt speed of the furnace. In particular, high belt speeds and low gas flow parameters may lead to the introduction of harmful carbon into the sintering zone

Identification of surface anion antisite defects in (110) surfaces of III-V semiconductors

We identify surface anion antisite defects in (110) surfaces of GaAs, GaP, and InP using scanning tunneling microscopy combined with density-functional theory calculations. In contrast to subsurface arsenic antisite defects, surface antisite defects are electrically inactive and have a very localized defect state which gives rise to a distinct feature in scanning tunneling microscopy images. (C) 2001 American Institute of Physics

Molybdenum - A biodegradable implant material for structural applications?

Molybdenum as a potentially new biodegradable material was investigated. Degradation behavior of commercially high purity molybdenum was observed in simulated physiological salt solutions (Kokubo's SBF with/without TRIS-HCl, Cu2+ addition and 0.9% NaCl solution). Potentiodynamic polarization, immersion mass loss and ion concentration measurements paired with REM/EDX analysis reveal gradual dissolution of molybdenum in the proper order of magnitude for stent application, associated with formation of thin, non-passivating corrosion products. The underlying corrosion mechanism is discussed as well as a comparison to literature data. However, formation of calcium phosphates (CaP) in SBF significantly decreases corrosion rates. In-situ polarization was found to be a potential way for overcoming this problem and simultaneously enhancing corrosion above the benchmark for a degradable stent material

Atmosphere study on the thermal decomposition behavior of delubrication aiding additives

In the present study, the effect of delubrication aiding additives on the thermal decomposition behavior was investigated. Such additives have been introduced in order to reduce stain formation caused by soot particles. Therefore, the atmosphere during the heat treatment of FeCuC components with Kenolube lubricant and a clean burn additive has been monitored by in-situ FTIR atmosphere analysis directly in the furnace. It was found, that delubrication aids reduce the decomposition into stable species like aromatic compounds. Furthermore, the formation of CO, CO2 and CH4 was increased considerably. In comparison to compacts without delubrication aid, the maximum peak temperatures of the gas evolution does not change considerably. However, with such an additive further peaks are visible. In particular, the bands caused by CO2 and alkene show additional peaks at lower temperatures. As a conclusion it is shown, that delubrication aids lead to improved lubricant decomposition as well as intensified soot burn-off

Efficient optimization of the debinding and sintering of non-beam based additive manufactured components

Non-beam based additive manufacturing methods of metal components typically make use of organic binder and additives, which need to be thermally removed prior to sintering. However, the parameterisation of such processes is not trivial, since decomposition of the organic components and the subsequent thermochemical reactions between process atmosphere and metal parts need consideration. Therefore, an in-situ monitoring instrument has been introduced which uses infrared spectroscopy and mass spectrometry in debinding furnaces in order to understand the decomposition of the organic components and the subsequent thermochemical reactions between process atmosphere and metal component. This method enables an efficient optimization of the temperature-time schedules and needed atmosphere composition in order to realize dense components with low contamination levels. In the contribution, the parameterisation routine will be shown and the achievable properties will be illustrated by various examples of components out of stainless steel 316L

Machinable porous gold structures for decorative applications made via supersolidus liquid phase sintering

Typical 18 ct. gold alloys like white, yellow, and red gold lend themselves for supersolidus liquid phase sintering due to a sufficient difference between solidus and liquidus temperature. In search of non-conventional design opportunities for decorative applications, this fact has been successfully exploited in this feasibility study for the manufacturing of sintered 18 ct. gold fiber structures from all three gold varieties as well as a foam-type material from yellow gold. Obtained porosities ranged from approximately 50 to 70 % for the fiber structures and reached up to 94.5 % for the foams. In order to make precisely shaped parts from these porous gold materials, a high-speed milling route was developed. Determination of favourable sintering conditions A literature survey on sintering of gold alloys was conducted, the most relevant findings of which are discussed below. [1] reports on the powder metallurgical production of wedding rings made from 9 ct. gold alloy (37.5 wt% Au, rest Ag, Cu, Zn and others). In order to prevent Cu and Zn from oxidising, a controlled oxygen-free atmosphere is recommended. Sintering was carried out 20 degrees below the solidus temperature at 780 °C for 24 hours in an atmosphere comprised of 95 % N 2 and 5 % H 2 with good results. The production of metal injection moulded parts from 18 ct. gold alloys is reported in [2]. In comparison with precision-cast parts, the obtained microstructure is much finer and thus provides better properties. Debindering and sintering takes about 65 hours. From the diagrams provided in the paper, it can be deduced that the sintering time amounts to roughly 24 hours. According to the authors, sintering was carried out at a temperature of 80 to 90 % of the melting temperature. The quasi-binary phase diagram (Fig. 1) reproduced from [3] indicates that such a sintering temperature would clearly correspond to solid state sintering conditions. The applied sintering atmosphere was 80 % Ar and 20 % H 2. Like other authors, [2] acknowledges the role of the gas flow and recommends low mass flows in order to warrant equal temperature conditions throughout the samples. Problems with remaining porosity are explained in terms of inhomogeneous packing of the powder particles