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Journal of Thermal Analysis and Calorimetry
Authors:
A. Małecki
,
R. Gajerski
,
S. Łabuś
,
B. Prochowska-Klisch
, and
K. Wojciechowski

Abstract  

A series of six nitrates(V) hydrates of 4d-metals as well as mercury and cadmium thermal decomposition was examined by DTA, TG and EGA techniques. It was found that thermal decomposition of d-metals nitrate(V) hydrates proceeds in three stages: partial dehydration, oxo-nitrates and hydroxide nitrates formation and metal oxides formation. General chemical equations for all decomposition stages were proposed. It was found that dehydration of hydrated salts is accompanied by partial decomposition of nitrate(V) groups.

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Abstract  

The purpose of this work was to investigate the influence of titanium and yttrium dopants on chemical stability of selected Ba(Ce1−xTix)1−yYyO3 compounds. The presented results are the part of wider research concerning the crystallographic structure, microstructure, electrical and transport properties of these groups of materials. Samples of Ba(Ce1−xTix)1−yYyO3 with x=0.05, 0.07, 0.10, 0.15, 0.20, 0.30 and y=0.05, 0.10, 0.20 (for x=0.05) were prepared by solid-state reaction method. Initially, differential thermal analysis (DTA) and thermogravimetry (TG) were used for optimization of preparation conditions. Subsequently, DTA-TG-MS (mass spectrometry) techniques were applied for evaluation of the stability of prepared materials in the presence of CO2. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results were used to determine the phase composition, structure and microstructure of materials and to assist the interpretation of DTA-TG-MS results. The strong influence of Ti and Y dopants contents (x and y) on the properties was found. The introduction of Ti dopant led to the improvement of chemical stability against CO2. The lower Ti concentration the better resistance against CO2 corrosion was observed. Doping by Y had the opposite effect; the decrease of chemical stability was determined. In this case the higher Y dopant concentration the better resistance was observed. The attempt to correlate the influence of dopant on structure and chemical stability was also presented.

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Journal of Thermal Analysis and Calorimetry
Authors:
W. Kucza
,
J. Obłąkowski
,
R. Gajerski
,
S. Łabuś
,
M. Danielewski
,
A. Małecki
,
J. Morgiel
, and
A. Michalski

Abstract  

The ultrasonic spray pyrolysis (USP) technique was used for synthesis of alumina- and zirconia-based powders. The starting agents were aqueous solutions, atomized by the ultrasonic spray generator and pyrolized in the furnace under the open-air conditions. The powders prepared by USP were in the form of solid and hollow aggregates (spheres) consisted of nanosize amorphous grains as determined by the microscopy and the X-ray diffraction techniques. The alumina-based powders were consolidated by the pulse plasma sintering resulting in single-phase materials. Different behavior of solid and hollow particles during the isostatic sintering is found; a higher degree of deformation of spheres is observed in the second case.

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