Papers by Keyword: Mössbauer

Abstract: The cyano-bridged complexe [Gu(en)x]yMA[Fe(CN)6]z·nH2O(MA=K+) have been synthesized. In the compound [Cu(en)2][KFe(CN)6]·H2O, we shows firstly a weak intramolecular anti-ferromagnetic coupling between Fe3+(ground state 5T2g, S=1/2) and Cu2+(ground state 6T2g3eg, S=1/2) through the long- range cyano bridges. The magnetic susceptibility obey the curie-weiss law [χ=C/(T-θ)] with a negative weiss constant,the curie constant C=0.42cm3·k·mol-1, the compound exists a strong Cu2+–CN–Fe3+ ferromagnetic interaction and a weak Cu2+(ground state 6T2g3eg, S=1/2)–Cu2+(ground state 6T2g3eg, S=1/2) antiferromagnetic interaction, through long range of NC-Fe-CN. At the same time, we have given an explanation from magnetic properties and struction of compounds.

Abstract: Geompolymers and their engineering applications have attracted significant attention of the scientific community. This is due to properties such as good thermal stability and high resistance to aggressive environments. Most studies on this subject are based on traditional precursor materials such as calcined kaolinite clay (metakaolinite) and fly ash. The iron content is significant, reaching around 10% in metakaolinite, for instance. The role of iron in geopolymers still lacks systematic investigation. This can be attributed to the limitations presenting nuclear magnetic resonance (NMR) spectroscopy, which is a widely used technique to study geopolymers structure. Ferromagnetic elements such as iron, which is often present in some precursors, affect the magnetic response of the material, compromising the proper analysis of its structure by NMR results. Iron content in some industrial residues may be several times higher as it is often found in metakaolinite. This work presents x-ray diffraction, infrared and Mössbauer spectroscopy studies on the distribution of iron species in iron oxide/hydroxide-rich precursor, which was used to synthesized geopolymers.

Abstract: Fe-Si alloys have excellent soft magnetic properties, specially around 12 at% Si. However, its industrial application is limited because of the lack of ductility, which causes cracking during rolling operations for the fabrication of thin sheets. The reason of the brittleness of the high silicon alloys is a disorder/order reaction at low temperatures. The aim of this work is to analyze the effect of the addition of Aluminum on the crystalline structure of Fe-Si alloys. Samples with a chemical composition of Fe88Si12 and Fe87Si12Al1 (at%) were prepared by Spray Forming. The structure was studied by means of X-ray diffraction and Mössbauer Spectroscopy. The presence of the DO3 and α- Fe phases were observed

Abstract: Elemental powder mixtures of Fe and Si were mechanically alloyed with a ball-mill. Mössbauer spectroscopy and X-ray diffraction were used to characterise the microstructural changes of these mixtures which are induced by high-energy ball-milling. Mössbauer spectra are discussed in terms of two main spectral components (corresponding to FeSi alloy and α-Fe) and the time dependence of the alloy formation follows a Johnson-Mehl type law. Calorimetry measurements show that the formed alloy is stable up to 800°C as no crystallisation or phase transformation peaks are observed. From X-ray diffraction, a crystallite size of 9 nm is obtained. Magnetic measurements at low temperature were carried out on the final alloy and the saturation magnetic moment at 4.2K is 0.44 μB/Fe.