Search Results

You are looking at 21 - 30 of 58 items for

  • Author or Editor: E. Kuzmann x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The thermal behaviour of Co(II), Ni(II) and Zn(II)-containing zirconium phosphate of α type was investigated. XRPD analysis revealed that, for the samples containing Co(II) or Ni(II), the first reflection of the solid phase is split into a doublet. In contrast, when Zn(II) is present, a single solid phase system is formed. The thermal behaviour of the materials followed this sequence. For the samples containing Co(II) or Ni(II), phase-transition processes were found and there was also a loss of crystal water, but for the sample containing Zn(II) there was only one endothermic effect, which corresponded to the decomposition of phosphate groups.

Restricted access

Abstract  

Mössbauer spectroscopy, X-ray diffractometry and differential scanning calorimetry were used to study the effect of the preparation parameters on the short range ordering of Fe83P17 amorphous alloys. The samples were quenched with different quenching rates from the melt which was kept either at 1100°C or 1250°C for 20 min. The short range order of the amorphous samples was found to depend on the quenching rate due to the relaxation taking place during rapid quenching of the melt. In one case, in the sample quenched with the lowest quenching rate from the melt of 1250°C, crystalline phases identified as Fe3P and -Fe were also found. This phase separation can be understood by taking into consideration the effect of both the melt temperature and the quenching rate. In this case, the cooling time can be long enough for separation of the phases which can be expected within the range of 1040–1250°C according to the phase diagram.

Restricted access

Abstract  

The thermal decomposition of zirconium molybdate, tungstate and arsenate were investigated. The total mass losses of the investigated materials were 12.5, 11 and 8.5%, respectively. Despite having different crystal dimensions and structure the thermal decomposition of the samples takes place in a similar way. During heating two main endothermic processes with mass loss were observed. At the end of the thermal decomposition, oxides of the original materials were observed. The mentioned mass losses originate partly from the crystal water loss of the materials. The calculated crystal water content in the original molecule was 1.3 and 1 mole/molecule unit, respectively. Furthermore, for zirconium arsenate, a sublimation process was recorded above 960 K.

Restricted access

Hydrated microcrystalline compound, V1-xCrxOy · nH2O, where x<0.063 and 4.4<n<8 and hydrated amorphous phases, CrVO4 ·H2O and Cr2V4O13 ·4H2O have been prepared using peroxo-polyacids of vanadium and chromium. The transformations of these hydrated phases upon heating were studied by TG-DTA and XRD techniques and led to three crystalline anhydrous compounds: (i) phase V1-xCrxOy, which is closely related to the orthorhombic V2O5, (ii) Cr2V4O13 and (iii) monoclinic CrVO4-M. The ranges of coexistence of phases in equilibrium were also determined.

Restricted access

Abstract  

The thermal decomposition of hafnium phosphate (both in amorphous and crystalline forms), molybdate and tungstate was investigated. Hafnium phosphate has a layered structure, that of molybdate and of tungstate are tetragonal one. On investigating these materials two main endothermic processes with mass loss were observed in the temperature range of 298–1023 K. These processes were identified as crystal and structural water loss of the materials. The total mass loss of hafnium phosphate, molybdate and tungstate was 11,35 and 6.0%, respectively. In the case of mixed hafnium-titanium salts various crystal water quantities were found, depending on the titanium content of the sample.

Restricted access

Abstract  

Mössbauer spectroscopy was used to study iron reduction in mineral originated from Aswan area in Egypt. The Mössbauer spectra of samples heat treated at 1000 °C in hydrogen atmosphere show a gradually reduction process of hematite. The main phase of sample aged for 1 h is magnetite, while alpha-iron as well as some silicates and wustite type oxide can be detected in sample aged for 3 h. Further aging of sample results in dissolution of alloying elements /Si, Al/, being present in the samples. This process starts already in samples aged at 1000 °C for 4 h, but it is more expressive in minerals heat treated at 1200 °C or 1300 °C, when all paramagnetic phases disappeared.

Restricted access

Abstract  

57Fe Mössbauer measurements were performed on FeSO3 being in frozen solution and in crystalline states. The obtained typical Mössbauer parameters for crystalline FeSO3.3H2O are IS=1.23±0.05 mm s–1 and QS=2.50±0.01 mm s–1, while for the fozen solution: IS=1.32±0.01 mm s–1, QS=3.24±0.01 mm s–1. It show that FeII is hexaaquacoordinated in the solution.

Restricted access

Abstract  

The crystallization kinetics of Fe83P17 amorphous alloy has been studied by Mössbauer spectroscopy and X-ray diffractometry. The samples were annealed isothermally at two different temperatures (315 °C and 325 °C). During isothermal annealing of the samples three phases were observed: crystalline Fe3P phase, crystalline -Fe phase and the amorphous phase. The value of the Avrami exponent was found to be about 2.0 at each annealing temperature. This suggests that the growth rate of the crystals is controlled by volume diffusion and the nucleation rate decreases during crystallization. The activation energy obtained for the overall crystallization process was 193±43 kJ mol–1.

Restricted access

Abstract  

Nine complexes of adenosine and related compounds (adenosine-5'-monophosphate, adenosine-5'-triphosphate, 1-methyl-adenosine, pyridoxal-5-phosphate and -nicotinamide-adenine-dinucleotide-phosphoric acid) with di-n-butyltin(IV) oxide and/or di-n-butytin(IV) dichloride were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain organotin(IV) moiety and the ligand in a ratio of 1:1 or 2:1. The FTIR spectra demonstrated that di-n-butyltin(IV) oxide reacts with the D-ribose moiety of the ligands, while di-n-butyltin(IV) dichloride is co-ordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mössbauer QS values with those calculated on the basis of the PQS concept revealed that the organotin(IV) moiety has trigonal-bipyramidal, octahedral and in some cases tetrahedral geometry also. Some of the complexes contain the organotin(IV) cation in two different surroundings.

Restricted access

Abstract  

Conversion electron Mössbauer spectroscopy (CEMS) and XPS has been used for the surface analysis of an X10CrNiTi 18/9 (DIN 1.7440)-type stainless steel in order to determine the supposed structural and/or chemical changes in the surface layer caused by polishing. Both, CEMS and XPS results can be associated with the appearance of Fe nitride in the outer layer of steel samples after polishing, while no sign of nitrogen was detected in the bulk material.

Restricted access