Investigation of Surface and Bulk Processes in Mg-based Alloys during Hydrogen Absorption

Different Mg-based alloys were tailored and prepared to investigate the surface and bulk processes during hydrogen absorption. Volumetric-, resistance-, XRD-, optical-, and mass measurements were carried out. Heat treatment experiments showed that the short-term thermal stability limits (during heating up at 5 K/min) of the amorphous samples were between 125-175 ° C, while long-term stability (during 24h heat treatment) is always lower – between 80 and 150°C. Nanocrystalline alloys were stable up to 300°C. Hydrogen absorption measurements were executed between 25 and 300°C. Pd-containing alloys were found to be the fastest absorbers, and 200°C was the optimal temperature regarding absorption rate. Etching the samples previously in HF solution enhances absorption by inducing surface cracking. This phenomenon was thoroughly examined by optical microscopy. The effect of hydrogen on the crystallization properties of MgNiPd sample was determined via in-situ resistance measurements

Investigation of Surface and Bulk Processes in Mg-based Alloys during Hydrogen Absorption

Different Mg-based alloys were tailored and prepared to investigate the surface and bulk processes during hydrogen absorption. Volumetric-, resistance-, XRD-, optical-, and mass measurements were carried out. Heat treatment experiments showed that the short-term thermal stability limits (during heating up at 5 K/min) of the amorphous samples were between 125-175 ° C, while long-term stability (during 24h heat treatment) is always lower – between 80 and 150°C. Nanocrystalline alloys were stable up to 300°C. Hydrogen absorption measurements were executed between 25 and 300°C. Pd-containing alloys were found to be the fastest absorbers, and 200°C was the optimal temperature regarding absorption rate. Etching the samples previously in HF solution enhances absorption by inducing surface cracking. This phenomenon was thoroughly examined by optical microscopy. The effect of hydrogen on the crystallization properties of MgNiPd sample was determined via in-situ resistance measurements

Alagutazó mágneses ellenállás (TMR) ferromágneses/szigetelő nanoszerkezetekben = Tunnelling magnetoresistance (TMR) in ferromagnetic/insulator nanostructures

Az OTKA pályázat során folytatott kutatások közül az elektrolitikusan előálított mágneses/nem-mágneses (főleg Co-Cu/Cu) multirétegek óriás mágneses ellenállásának (GMR) megértésével kapcsolatos tevékenységünk igen eredményes volt (10 nemzetközi folyóiratpublikáció, 2 konferenciaközlemény, felkérés 1 könyvrészlet megírására és 13 meghívott előadás tartására). Kutatásaink során tisztáztuk a szakirodalomban sokat vizsgált, de korábban nem teljesen megértett elektrokémiai folyamatok (az ún. Co Cu cserereakció és a Co-visszaoldódás) és a leválasztási módok szerepét a multirétegek képződésében és hatásukat a GMR-ra. A kétimpulzusos multiréteg előállításnál eddig kizárólagosan használt áram/áram vagy potenciál/potenciál kombinációk mellett bevezettük az optimálisabb áram/potenciál impulzuskombinációt. Egy másik OTKA pályázatunk eredményeit felhasználva optimalizáltuk a kulcsfontosságú Cu-leválasztási potenciál értékét, így első ízben lehetett tanulmányozni a GMR függését a valódi rétegvastagságoktól elektrolitikus multirétegekben. Ezen eredmények alapján arra következtettünk, hogy a Cu nukleációja Co felületen más jellegű, mint a Co nukleációja Cu felületen. A mágneses ellenállás térfüggését analizálva megállapítottuk, hogy az elektrolitikus multirétegekben megfigyelt nagy telítési teret a mágneses rétegek egyes tartományainak szuperparamágneses viselkedése okozza, amelyek GMR járulékának kvantitatív meghatározására módszert dolgoztunk ki. | Our OTKA project activity was very successful in the field of electrodeposited (ED) magnetic/non-magnetic Co-Cu/Cu multilayers, especially concerning the study of their giant magnetoresistance (GMR) behaviour, as indicated by 10 papers in international journals and 2 in conference proceedings, and by the invitation to write a book chapter as well as to give 13 invited talks at international conferences. We have clarified the role of the previously intensively studied but not completely understood electrochemical processes (Co Cu exchange reaction and Co-dissolution) and of the deposition modes in multilayer formation and their influence on GMR. In addition to the current/current or potential/potential deposition modes formerly exclusively applied, the more advantageous current/potential pulse combination was introduced. Relying on our reuslts from another OTKA grant, we have optimized the Cu deposition potential, enabling for the first time a study of the dependence of GMR on true layer thicknesses in ED multilayers. It could be concluded from this study that there is an asymmetry in the nucleation behaviour of Co and Cu on top of each other. Analyzing the field dependence of the GMR, we have established that the large GMR saturation field usually observed in ED multilayers arises from some regions of the magnetic layers which exhibit superparamagnetic behaviour and we have elaborated a method to extract the latter contribution from the measured data

SOME STRUCTURAL ASPECTS OF MAGNETIC PROPERTY EVOLUTION IN FINEMET-TYPE SENSOR MATERIAL DURING AMORPHOUS-NANOCRYSTALLINE TRANSFORMATIONS

Devitrification of glassy Fe73.5Si13.5B9Nb3Cu1 alloy used as potential sensor material was followed by magnetic measurements and X-ray diffraction, and transmission electron microscopy. It was found, that the permeability, and the coercive field of the alloy changed well below the crystallisation onset, showing a remarkable increase, which was attributed to the structural relaxation and a heterogen nucleation of iron rich phase on Cu clusters. On the basis of lattice parameter measurements the iron rich clusters were depleted from Si atoms during the nucleation process and the Si atoms built in them only during annealing at higher temperatures as 500 \circC and 540 \circC forming a DO3 structure. From the structural study of samples annealed near to the optimal transformation stage it was concluded, that size distribution of the bcc-Fe(Si) nanocrystallites (not exclusive factor) was only one of the most important factors to achieve the optimal soft magnetic properties, but at the same time, their volume fraction, as well as the degree of ordering in DO3 structure did also contribute to the property optimization. The average grain size produced by laser pulse heat treatment was nearly the same, as that obtained during the traditional heat treatments

Chloroquin indukálta cardiomyopathia avagy a „pszeudo-Fabry-kór” fatális lefolyású esete = Chloroquine induced cardiomyopathy: a fatal course of „pseudo-Fabry’s-disease”

A chloroquint napjainkban szisztémás autoimmun kórképek kezelésére használják, autoimmun szöveti károsodást gátló és immunomoduláns hatása miatt. Ritka, ám súlyos mellékhatása a szernek, hogy restriktív cardiomyopathia-szerű képet okozhat, ami fenotípus és hisztológiai kép tekintetében egyaránt a Fabry-kór kardiális manifesztációjára emlékeztet. Munkánkban egy 73 éves nőbeteg esetét mutatjuk be, akinek fulmináns lefolyású szívelégtelensége hátterében chloroquin-cardiomyopathia állt. A beteg anamnézisében tartós chloroquinszedés szerepelt, rheumatoid arthritise miatt. 71 éves, korában harmadfokú atrioventricularis blokk miatt igényelt végleges pacemaker-implantációt. 2 évvel később kardiális dekompenzáció miatt került intézeti felvételre. Ekkor transthoracalis echokardiográfia során masszív koncentrikus bal kamrai hipertrófia, közepes fokban csökkent szisztolés balkamra-funkció és restriktív típusú mitrális beáramlási görbe volt észlelhető. A beteg a kéthetes hospitalizáció során kompenzálható volt, azonban 1 hónapon belül súlyos állapotban rehospitalizációra került sor, ami fatális kimenetelű volt. A klinikai kép és az autopsziás lelet alapján felmerült Fabry-betegség gyanúja. Tekintettel azonban a beteg tartós chloroquin szedésére, chloroquin indukálta cardiomyopathiát valószínűsítettünk. A chloroquin kardiális jellegű mellékhatásai – bár az alkalmazási előírásban említésre kerülnek – kevésbé ismertek. Ajánlásokra lenne szükség azzal kapcsolatban, hogy milyen gyakran, milyen módszerrel javasolt a tartósan chloroquint szedő betegek kardiológiai szűrése

Early post-operative thrombosis of the prosthetic mitral valve in patient with heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is one of the most common immune-mediated adverse drug reactions, with frequencies as high as 2-3% for certain groups of post-cardiac surgery patients. We report on an 50-year-old woman with early post-operative thrombosis of the prosthetic mitral valve due to heparin-induced thrombocytopenia. Non-invasive imaging (two-dimensional transesophageal echocardiography; 2D-TEE) allowed the exact localisation of thrombotic masses and revealed the increase of the mean diastolic mitral gradient. The HIT diagnosis was proved by the clinical scoring system, and with the identification of heparin platelet factor 4-induced antibodies. After the withdrawal of LMWH therapy and the start of intravenous lepirudin treatment, the patient's medical condition improved continuously. Follow-up echocardiography showed a step-wise decrease in the severity of the mean diastolic mitral valve gradient and a complete resolution of thrombus formations. Perhaps we may remind ourselves that, whilst HIT is one of the most common immune-mediated adverse drug reactions for certain groups of post-cardiac surgery patients, it can be managed successfully. We would also stress the importance of serial 2D-TEE examinations in the early post-operative period

The effect of laser cutting on the structure of amorphous glassy tapes

Although thin metal strips or amorphous ribbons offer a higher magnetic performance compared to the presently used thicker crystalline electrical steels in electric motors, they have been considered unsuitable to build the rotor and/or the stator of classical electric motors because of fabricating limitations. Nowadays the development of high efficiency electrical motors has an outstanding significance, so an attempt is made to apply the soft magnetic glassy tapes to build stator and rotor elements for this application. However Fe based amorphous ribbons are promissing base materials, but in order to use them, several additional requirements have to be satisfied, like cutting the soft magnetic elements into the appropriate shapes, avoiding the degradation (local crystallization) of the individual glassy elements. In this paper the heat affected zone of soft magnetic materials like FINEMET and METGLAS were examined after laser cutting. The investigations were focused on structural changes (XRD and DSC) and microhardness distribution of the heat affected zone which have a strong relation to mechanical properties for example embrittlement. These materials will be used in electric motors to increase its efficiency therefore it is important to us for later machinability and handling of laser cutted part