It has been found that the modified Zhuravlev equation, [(1−α)−1/3−1]2=ktn, which describes the kinetics of oxidation of V2O4 and V6O13 in the temperature range 820–900 K and in the oxygen pressure range 1.0–20 kPa, can be derived via the assumption that the
changes in the observed activation energy result from the changing contributions of the two diffusion processes controlling
the reaction rate. The values of the observed activation energy are in the range 160–175 kJ mol−1 for V2O4 and 188–201 kJ mol−1 for V6O13 in the scope of the experimental oxygen pressures and temperatures and conversion degrees of 0.1–0.9.
Calorimetric method for the determination of radiation power of the solar-simulated light sources has been proposed. The application
of the differential scanning calorimetry guarantees very high sensitivity (1 mW) of the measuring property, independent of
the wavelength (within 300-1200 nm). The applied method yields reliable calibration curves of the radiation power vs. wavelength
with good accuracy.
The mutual reactivity in mixtures containing Nasicon (Na3Zr2Si2PO12) or YSZ (ZrO2:Y2O3) solid electrolytes with Li2CO3 or Li2CO3:BaCO3 sensing electrode materials was investigated using simultaneous DTA and TG and ex situ XRD techniques. The uncontrolled chemical
reaction is suspected to be responsible for the instability of electrochemical gas sensors constructed from these materials.
DTA and TG results obtained for Nasicon-carbonate mixtures indicate the possibility of reaction in the temperature range from
about 470 to 650C, which overlaps the sensor operating temperature range (300–525C). The results obtained for YSZ-carbonate
mixtures indicate that reaction between carbonate and the ZrO2 takes place at higher temperatures and cannot explain the instability drift of investigated sensors. The mechanism of observed
reactions in systems studied is also discussed.
The binary system Li2CO3–BaCO3 was studied by means of differential thermal analysis (DTA), thermogravimetry (TG) and X-ray phase analysis. The composition
of carbonate and CO2 partial pressure influence on the thermal behavior of carbonate were examined. It was shown that lithium carbonate does not
form the substitutional solid solution with barium carbonate, however the possible formation of diluted interstitial solid
solutions is discussed. Above the melting temperature the mass loss is observed on TG curves. This loss is the result of both
decomposition of lithium carbonate and evaporation of lithium in Li2CO3–BaCO3 system. Increase of CO2 concentration in surrounding gas atmosphere leads to slower decomposition of lithium carbonate and to increase the melting
The powders of Ni−P alloys containing 13% of phosphorus were obtained by precipitation from the solution. The oxidation of
Ni−P alloys in polythermal conditions was studied. It was found that oxidation of Ni−P alloys goes through stages and that
intermediate products of the oxidation are: Ni2P and Ni2P2O7. The final products of oxidation process are NiO and Ni3(PO4)2. The sequence of chemical reactions describing the oxidation of Ni−P alloys was proposed.
The mechanism of thermal decomposition of Co(NO3)2 · 2H2O was found to involve stages in which Co(NO3)3 and Co2O3 · H2O are formed both of which decompose to Co3O4. During the process, the total cobalt enters the +3 oxidation state, which is consistent with the results reported by Mehandjiev .
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.