2D Numerical Simulations of Embankment Dam Failure Due To Overtopping

Water Qualit

The formation of non-condensable gases in ammonia/ water absorption heat pumps made of stainless steel - literature review and experimental investigation

Part of: Thermally driven heat pumps for heating and cooling. – Ed.: Annett Kühn – Berlin: Universitätsverlag der TU Berlin, 2013 ISBN 978-3-7983-2686-6 (print) ISBN 978-3-7983-2596-8 (online) urn:nbn:de:kobv:83-opus4-39458 [http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-39458]Highly efficient ammonia/water absorption heat pumping (AHP) processes (e.g. the GAX-process) require a high desorption temperature level of e.g. 200°C and above. At these conditions the formation of non-condensable gases can take place, which can be dedicated to two chemical processes: corrosion of steel and thermal decomposition of ammonia. Within a research project the possible use of stainless steel components at high temperature level has been investigated. Tests with an absorption/desorption test rig operating at temperatures up to 290°C as well as corrosion tests using autoclaves at temperatures up to 220°C have been performed. The produced non-condensable gas has been analysed using gas-phase chromatography in order to identify the responsible chemical process. The results show a large initial corrosion rate which decreases with time. This may be explained by a passivation process of the steel surface. At all tests the carbon steel (ST37) autoclaves has shown significant lower corrosion rates compared to the stainless steel components. Regarding the thermal decomposition no dissociation products has been detected up to a temperature level of 290°C

In-situ deformation monitoring of thin electrochemically deposited copper lines during thermo-mechanical pulsing

In semiconductor industry, the development of the last years led to smaller and smaller devices in order to maximize efficiency and minimize costs. As a result, a miniaturization of the test structures is required as well as a proper method to monitor gradual deformation processes during repetitive thermal cycling. Thin metal films, e.g., Cu are commonly used in power semiconductor devices. Rapid temperature changes combined with a mismatch in thermal expansion coefficients of the different materials in the layer stack lead to thermo-mechanical stresses and as a result to deformation of the metallization. In order to realize high heating rates (up to 106 K/s) and to be able to observe deformation on the metallization surface, polyheater structures are used. There, a polysilicon layer works as a heating plate (Joule heating) for the Cu layer above, allowing repetitive heating and cooling on short timescales. The temperature of the system is measured using an integrated sensor. Since the deformation features, e.g. slip bands and extrusions, are on the sub-micron length scale, a scanning electron microscope (SEM) is necessary for in-situ deformation monitoring. This novel approach provides the possibility to observe the gradual deformation of metallizations under variable test parameters at high magnification and in vacuum. As test structures, 20x20x300 µm³ Cu lines with different types of copper on top of the polysilicon were chosen to be able to observe the surface as well as the side walls of a metallization structure. It is revealed, that different Cu grain microstructures lead to differences in deformation behavior during thermo-mechanical cycling. Videos of the deformation process and EBSD images are presented to demonstrate the method