Plastic Deformation and Modification of Surface Characteristics in Nano and Micro Levels and Enhancement of Electric Field of FCC Materials Using Cavitaion Phenomenon

The aim of this paper is to demonstrate and establish a possible application of the cavitation phenomenon as an efficient method to modify surface properties. Three FCC (Face Centered C ubic) materials were subjected to high s peed submerged cavitating jets under certain working conditions, for time periods between 15 and 1,800 s. The force generated by cavitation is employed to modify the surface roughness in nano and micro scales. The target surface was investigated with digit al optical microscopy , atomic force and electrostatic force microscopy (AFM and EFM) and also with a white light interferomet er . These different observation techniques indicate that at short exposure times, the observed characteristic features in the micro structure – hills, holes and wavy configurat ion – can be related to the start of the plastic deformation of the specimen surface. Longer exposure times inevitably result in a greater number of jet specimen interactions leading to specimen erosion and fract ure. The results demonstrate the possibility to use cavitation bubbles as a micro - nanofabrication method for the surface preparation /modification or shoot - less surface peening. EFM results present a possibility of using cavitation as tool to enhance the e lectrostatic properties of a metal surface by modifying its roughness. The degree of enhancement depends o n the material properties

Influence of Cu deposition potential on the giant magnetoresistance and surface roughness of electrodeposited Ni-Co/Cu multilayers

It has been shown previously for electrodeposited Co/Cu multilayers that the single-bath electrodeposition process can be optimized from an electrochemical point of view in order to avoid unwanted Co dissolution and incorporation of Co in the non-magnetic layer during the Cu deposition pulse. In the present work, electrodeposition of Ni–Co/Cu multilayers has been studied to clarify if the same optimization method is appropriate when two magnetic elements are present and if this potential results in the largest giant magnetoresistance (GMR) for the particular alloy system studied. For this purpose, several Ni–Co/Cu multilayers were prepared by varying the deposition potential of the Cu layer. The composition analysis of the deposits showed that the Ni:Co ratio exhibits a minimum as a function of the Cu deposition potential, which can be explained by considering both the dissolution of Co and the mass transport of the reactants. Both the saturation GMR value and the intensity of the satellite peaks in the X-ray diffractograms were highly correlated with the resulting surface roughness of the deposits which was strongly varying with the Cu deposition potential. Higher GMR values, lower saturation fields and more perfect multilayer structure were observed for sufficiently positive Cu deposition potentials only which enabled a partial Co dissolution resulting in a reduced surface roughness. The results draw attention to the complexity of the optimization procedure of the deposition of multilayers with several alloying components

Pre-excitation studies for rubidium-plasma generation

a b s t r a c t The key element in the Proton-Driven-Plasma-Wake-Field-Accelerator (PWFA) project is the generation of highly uniform plasma from Rubidium vapor. A scientifically straightforward, yet highly challenging way to achieve full ionization is to use high power laser which can assure the barrier suppression ionization (BSI) along the 10 m long active region. The Wigner-team in Budapest is investigating an alternative way of uniform plasma generation. The proposed Resonance Enhanced Multi-Photon Ionization (REMPI) scheme can be probably realized by much less laser power. In the following we plan to investigate the resonant pre-excitations of the Rb atoms, both theoretically and experimentally. In the following our theoretical framework is presented together with the status report about the preparatory work of the planned experiment