Mössbauer study of the effect of preparation parameters in rapidly quenched Fe−Cr−P−C,Fe−Cr−B and Ni(57Fe)P amorphous alloys

Mössbauer spectroscopy was used to get information about the effect of preparation parameters (quenching rate, temperature and time of solution treatment of melt) on the structure of rapidly quenched Fe₇₀Cr₁₀C₇P₁₃, Fe₇₉Cr₁₅B₁₅ and Ni₈₀ ⁵⁷Fe₁P₁₉ amorphous alloys. We have found smaller but measurable thickness dependent changes in the average Mössbauer parameters and in the hyperfine field distribution of Fe₇₀Cr₁₀C₇P₁₃ samples than those observed in Fe₇₀Cr₁₀C₁₀P₁₀ amorphous alloys [3]. On the other hand, differences were found in the hyperfine field distribution of very rapidly quenched Fe₇₀Cr₁₀C₇P₁₃ alloys with increasing time of solution treatment of melt. Changes in the average parameters and in the quadrupole splitting distribution were also observed with variation of thickness as well as of temperature of melt in the Fe₇₀Cr₁₅B₁₅ and Ni₈₀(Fe)P₁₉ samples, respectively. The finding can be interpreted in terms of changes in the short range order due to different preparation conditions.     

Oxidative Dehydrogenation of Cu(II) Complexes with N-Aryl-N-2-hydroxybenzyl- and N-Aryl-N-2-hydroxynaphthylmethyleneamine Derivatives

The reactions of Cu²⁺, Co²⁺, and Ni²⁺ ions with N-phenyl-N-2-hydroxybenzyl- and N-phenyl-N-2-hydroxynaphthylmethyleneamine derivatives (HL ⁿ , n = 1–8) produced from the derivatives of aniline and aromatic -hydroxyaldehydes are studied. Among the ions studied, only Cu²⁺ forms stable complexes Cu(L ⁿ )₂ · 2H₂O. The structures of the synthesized compounds are studied by IR, UV, and EPR spectroscopies and differential thermal analysis. The magnetic moments of the Cu(L ⁿ )₂ · 2H₂O complexes are very small and range within 0.43–1.19 _B, depending on the ligand structure, which indicates a strong antiferromagnetic interaction between the Cu²⁺ ions. The temperature dependence of the magnetic susceptibility measured for the Cu(L³)₂ · 2H₂O complex (where HL³ is N-4-methoxyphenyl-N-2-hydroxybenzylamine) is closest to the theoretical curve calculated for the binuclear Cu(II) complexes connected by the intermolecular exchange interaction. The Cu(II) complexes with HL ⁿ are shown to undergo oxidative dehydrogenation to form the corresponding metal salicyl-aldiminates. This reaction can occur on heating in the absence of oxygen and is accompanied by the Cu²⁺ Cu⁺ transition.     

Mössbauer study of phase separation in Ni80 57Fe1P19 amorphous alloys

Mössbauer spectroscopy, X-ray diffractometry, scanning calorimetry and electrochemical measurements were used to study the crystallization process of Ni₈₀ ⁵⁷Fe₁P₁₉ amorphous alloys kept in melt at different temperatures before quenching. Samples were heated up to 430°C and 720°C at a rate of 20°C/min, in order to reach characteristically different stages of crystallization. Even at the same crystallization, stage the room temperature Mössbauer spectra and the X-ray differactograms were different depending on the temperature (1050°C or 1400°C) at which the samples were kept before quenching the melt. The Mössbauer spectra showed a paramagnetic component and two sextets (H=267 kOe and H=245 kOe) at 430°C while at 720°C there was only one sextet (H=267 kOe) besides the paramagnetic component. The changes in the Mössbauer spectra of different samples due to crystallization are consistent with the explanation that phase separation occurs in Ni₈₀ ⁵⁷Fe₁P₁₉ rapidly quenched from the melting temperature of 1050°C.