Thermal Stability and Phase Transformations of Multicomponent Iron-Based Amorphous Alloys

Due to their excellent functional properties enabling their applicability in different fields of modern technology, amorphous alloys (metallic glasses) based on iron have been attracting attention of many scientists. In this chapter, the results of multidisciplinary research of five multicomponent iron-based amorphous alloys with different chemical composition, Fe81Si4B13C2, Fe79.8Ni1.5Si5.2B13C0.5, Fe75Ni2Si8B13C2, Fe73.5Cu1Nb3Si15.5B7, and Fe40Ni40P14B6, are summarized in order to study the influence of chemical composition on their physicochemical properties and functionality. The research involved thermal stability, mechanism, thermodynamics, and kinetics of microstructural transformations induced by thermal treatment and their influence on functional properties. Determination of crystallization kinetic triplets of individual phases formed in the alloys is also included. The results obtained for different alloys are compared, correlated, and discussed in terms of the alloy composition and microstructure

Sinteza i karakterizacija nikal(II) i bakar(II) kompleksa sa polidentatnim dialkil ditiokarbaminskim ligandom 3-ditiokarboksi-3-aza-5-aminopentanoatom

Square planar complexes of Ni(II) and Cu(II) with potassium 3-dithiocarboxy-3-aza-5-aminopentanoate have been prepared by direct synthesis. The obtained neutral complexes were characterized by elemental analysis, magnetic susceptibility measurements, infrared and electronic spectra. The thermal behaviour of both the Ni(II) and Cu(II) complexes, and the ligand itself was investigated by DSC and TG.Direktnom sintezom između nikal(II)- i bakar(II)- soli i kalijum 3-ditiokarboksi-3-aza-5-aminopentanoata nagrađeni su odgovarajući kompleksi kvadratno-planarne strukture. Izolovani neutralni kompleksi karakterisani su elementalnom analizom, infracrvenom i elektronskom apsorpcionom spektroskopijom, kao i merenjem magnetnih susceptibiliteta. Termičko ponašanje kompleksa i liganda ispitivano je primenom DSC i TG metoda

Influence of thermal treatment on structure and properties of Fe75Ni2Si8B13C2 amorphous alloy

Iron-based amorphous alloys have been a focus of considerable scientific interest in recent years, both from fundamental and practical point of view. Comprehensive study of Fe75Ni2Si8B13C2 amorphous alloy investigated its thermal stability and thermally induced changes of the electrical, magnetic and mechanical properties and correlated them with microstructural changes. The alloy was investigated in 25-1000°C temperature range. Thermally induced structural transformations had been investigated using the DSC and the thermomagnetic measurements, revealing that the alloy exhibits the Curie temperature, glass transition, multi-step crystallization and recrystallization. The crystallization kinetics was determined, under non-isothermal conditions, to include three processes, corresponding to crystallization of α-Fe, Fe3B and Fe2B phases, respectively. Microstructural analysis using the XRD and the Mössbauer spectroscopy suggests that Fe3B acts as an intermediate in the formation of Fe2B. The microstructure was investigated on both the surface of the alloy ribbon and on the cross-section, using SEM to determine structural changes of the alloy after thermal treatment. Additionally, the XRD spectra were analyzed to determine the change in microstructural parameters of the alloy caused by the thermal treatment and the structural transformations. The Mössbauer spectroscopy was used to determine the distribution of iron atoms between the individual crystalline phases and the amorphous matrix. The functional properties were investigated using measurements of the magnetic susceptibility, electrical resistivity and microhardness and these results were correlated with changes in the microstructural parameters (average crystalline size, microstrain) and the phase composition. The measurements were performed, where possible, both during heating cycles to observe the change of these properties with temperature, and at room temperature, after individual heating cycles to determine the change in properties caused by annealing at different temperatures

Investigation of thermal stability and kinetic studies of transition metal complexes with the condensation product of 2,6-diacetylpyridine and semioxamazide

Thermal behavior of Cu(II), U(VI), Mn(II) and Ni(II) complexes with 2',2"'-(2,6-pyridinediyldiethylidyne)dioxamohydrazide was studied by DSC and TG analysis, in the temperature range of 20-600 degreesC in a stream of nitrogen. Depending on the structure of complexes, thermal degradation occurred mostly in the range of 200-400 degreesC, preceded by a loss of crystal and coordinated solvent if present. Kinetic processes of degradation were studied by analysis of DSC and TG curves recorded at one or more heating rates. Based on activation energies, determined in this way, thermodynamic parameters of activated complexes were also determined for U(VI) and Mn(II) complexes. Mechanisms of,degradation processes were established using the obtained data

Investigation of thermal stability of Zn(II), Pt(II) and Pd(II) complexes with (E)-2-oxo-2-(N-[1-(pyridin-2-yl)ethylidene]hydrazino}acetamide

Thermal stability of neutral Zn(II), Pd(II) and Pt(II) complexes of formulae [Zn(apsox)(2)](.)3H(2)O and [M(apsox)Cl] (M=Pd(II), Pt(II), HL=(E)-2-oxo-2-{N -[1-(pyridin-2yl)ethylidene]hydrazino)acetamide) were studied. The results of DSC and TG analyses within the temperature range from 20 to 600 degrees C in nitrogen atmosphere showed that the loss of crystal water represents the first step during decomposition of the octahedral Zn(II) complex followed by structural rearrangement of its anhydrous form. After that the complex remained stable to about 330 degrees C. Different from neutral square-planar Pd(II) and Pt(II) complexes, a satisfactory resolution of the peaks in DSC of the Zn(II) complex enabled determination of the activation energies of its structural transformation and thermal degradation