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Research activity and fields of interest
The most important field of our research activity is the electrodeposition of samples with alternating magnetic / non-magnetic layers. The thickness of the individual layers typically falls in the 0.5-6 nm range; i.e. a full coverage has to be attained even if only 2 or 3 atomic layers are deposited.
The production method applied is the electrodeposition. In most of the cases, we use the so-called single-bath method, in which one solution contains the ions of both metals to be deposited, but the concentration of the ions of the non-magnetic metal is 1 to 2 orders of magnitude smaller than that of the other metal. The multilayer structure can be achieved by using square-shaped current or potential pulses. The mixed potentiostatic-galvanostatic deposition method with an unlimited number of sublayers has also been elaborated. It is also our purpose to develop a flow cell capable of eliminating the drawbacks of the single-bath method.
The samples deposited are studied with different methods. The elementary composition is established by means of Electron Probe MicroAnalysis (EPMA; often referred to as "EDAX"). The morphology of the deposits can be studied with Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The crystal structure, preferred orientation and grain size of the samples are elucidated from X-Ray Diffractometry (XRD).
Besides the structural analysis, the main goal of the research is the investigation of the magnetoresistance of the electrodeposited samples. In our laboratories, the magnetoresistance can be measured in the 10-300 K temperature range. The term "magnetoresistance" is used as the ratio of the electric resistances measured with and without applying a magnetic field. The change in electric resistance with magnetic field in layered samples is related to the correlation of the direction of the magnetic field in the neighboring magnetic layers. This phenomenon has found an application in reading at a high rate the information stored on magnetic disks. Our primary interest is to elucidate the relationship between deposition parameters, the magnetoresistance of the deposits and the structural information obtained with various methods.
For the period between 2000 and 2004, a team from young scientist has been formed to run a project supported by the Hungarian Scientific Research Fund. We work on the development of multilayer deposition in flow-cells with modulated solution composition.
Hydrogen absorption, storage in and extraction from metals has long been a major challenge for the energy industry. Due to the importance of the topic, development of hydrogen storage materials and behavior of hydrogen in metals has been dealt with in a number of laboratories. We use palladium-silver alloys as model materials to study hydrogen diffusion and pay quite much attention to hydrogen trapping, too. An "in situ" resistivity monitoring system is used to follow the uptake and release of hydrogen. We also operate a workstation for electrochemical permeation studies.
Besides the storage of hydrogen, it is very important to mention the impact of hydrogen to structural materials. A typical example is the hydrogen embrittlement of ferrous alloys. Between 2000 and 2002, we dealt with the effect of hydrogen to the enamel behavior of modern steels, as a result of an industrial contract. Later, this project was continued and the research consortium was widened by many enamel and steel companies. These projects involve the exact solution of diffusion equations, computer simulation of the effect of the traps and the experimental determination of the hydrogen diffusion coefficient in the metals as a function of temperature. The ultimate goal of this project is to develop a procedure which is appropriate to test the enamelability of some steel types under industrial conditions.
The hydrogen permeation through steels have been investigated with the help of a dual electrochemical cell, in which the two sides of the electrode act as either a cathode or an anode at the same time. Both hydrogen absorption and permeation are monitored with electrochemical methods.
Besides the aforementioned ongoing experimental work, many other electrochemical phenomenon meet our interest, mostly those which involve some other physical aspect as well. For instance, the impact of the magnetic field on the electrodeposition of nonmagnetic materials is an interesting problem. As a summary we can say that every field of the applied electrochemistry can be a potential field of interest which exhibits some physical aspect, especially from the field of solid-state physics.