Plath, Peter
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Preferred name
Plath, Peter
Official Name
Plath, Peter
Alternative Name
Plath, Peter J.
Plath, Peter Jörg
Plath, P. J.
ORCID
GND
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Item-typ:Veröffentlichung, Räumliche und zeitliche Instabilitäten in einem technischen Prozess, Elektropolieren von Messing(2002-10-25); ; ; Electropolishing is a technical process to obtain smooth and shiny surfaces and a means of electrochemical metal removal, where the workpiece is the anode. The operation point of electropolishing is the transpassive region of the cyclovoltamogram, where two competing processes occur: The dissolution of metal (Cu and Zn) and the hydrolysis of water. Due to the hydrolysis of water, oxygen is formed at the anode causing gas bubbles to rise.Within the scope of this work, the behaviour of brass CuZn37 in electrolytes containing phosphoric acid and alcohol was studied. The anodic dissolution of brass in the transpassive region created a complex temporal behaviour. Depending on the electrolyte mixture chosen and the current density employed, different dynamical regimes could be realised. Time series and cyclovoltamograms revealed the appearance of an N-NDR or N-HNDR. Therefore, this technical process could be categorized according to the classification of dynamical electrochemical systems.When electropolishing was performed for a time period that was longer than an hour, stationary spatial pattern formation occurred on the electrode. These patterns were in the range of micrometers and could be characterised by employing methods of fractal geometry. The spatial structure formation typical of electropolishing processes is formed by an overlay of two competing phenomena. On the one hand, there is an isotropic structuring due to the formation and the growth of polarized oxygen bubbles at the anode. On the other hand, an anisotropic structuring occurs when the gas bubbles release from the metal surface and rise in front of it. Enriched electrolyte of a higher density submerging in front of the anode interacts with these gas bubbles. The interplay of all these processes leads to the typical streaming (Gasbahnen). Therefore, the timing and the mode of interaction between the gas bubbles and the metal surface are critical parameters for the final structure of the metal surfaces.Dissertation286 116 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Coupling of Chemical and Hydrodynamic Instabilities at the Electrochemical Dissolution of Metals(2002-11-22); ; ; The conditions for genesis of chemically induced hydrodynamic convection flow at resting and slowly rotating disk electrodes were studied. On the basis of these studies, the convection flow patterns beneath the electrode could be directly correlated with the etched patterns in the surfaces of the corresponding electrodes. It was not possible to capture images during experiments at high rotational speeds (1000 - 6000 rpm) on account of the very fast movements in the solution as well as the strong light absorption of concentrated iron(III) chloride solution. However, the hydrodynamic flow emerges as an etched spiral pattern in the electrode surface, thus enabling detailed investigation of the structures after each experiment. These spiral-like patterns follow a logarithmic rule and feature an invariant curvature, even under different experimental conditions. This invariant behaviour of the spiral pattern formation can be explained physically, and a fixed ratio of tangential to radial flow of 2:sup:-½:/sup: was found for the curvature of the spirals generated. Besides the formation of a topographically structured surface, the system exhibits galvanostatic potential oscillations. In addition to classical electrochemical oscillations, a new type of oscillation was detected. These superimposed oscillations could be correlated directly with the circular height profile of the topographically structured surface. It could be shown that this new type of oscillation is caused by the interaction between hydrodynamic vortex patterns in the boundary layer, on the one hand, and the electrochemical dissolution process, on the other hand. The experiments and theoretical interpretations shown in this work regarding the pattern formation at non-, slow and fast rotating disk electrodes under dissolving conditions provide a fundamental contribution to understanding the coupling between electrochemical processes and hydrodynamic flow at dissolving disk electrodes.Dissertation260 157 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Separation of solid-liquid and liquid-liquid phases using dielectrophoresis(2010-12-16); ; ; Over 3 decades after dielectrophoresis (DEP) was explored and defined, it has already been successfully applied in separating and handling bioparticles in micro and sub-micro scale biotechnology. However, nearly all of DEP applications are concentrated on the analysis and manipulation of particles in sub-micron and micron scaled systems with flow rates below mL/min. So far, none is known in process engineering for DEP in a scaled up application at flow rates of liters or even cubic meters per minute. The research described in this Ph D thesis is the first that attempts to scale up DEP application. With the research results described in this thesis, the feasibility of the DEP application in separation is verified. The proved high selectivity and controllability of DEP technique grand DEP a very promising prospect in separating and manipulating particles. The whole thesis work was implemented with three main steps, basic research of DEP mechanism and its side-effects and constrains, as a proof of principle gold particle fractionation using DEP, and a lab-scaled technical application of DEP in intensifying cross-flow membrane filtration, based on four papersDissertation321 177 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Zur Dynamik des elektrochemischen Metallabtrags(2005-10-11); ; The thesis is about the dynamics of the electrochemical removal of metal. First different removal processes and their dynamics are presented. Some dynamics of the removal of cobalt and the removal of steel in ferric chloride are described. Especially the non linear dynamics of electropolishing are discussed. The variable potential during electropolishing was examined. Pattern formation is described. The formation of fronts in the so called Hull Cell was observed. And the new micro-electropolishing process is presented. This process is based on the use of pulsed current in combination with a micro cathode.Dissertation337 148