J. Sztatisz

Combined DTA and XRD study of sintering steps towards YAl3(BO3)(4)

Sintering processes in the Y2O3–Al2O3–B2 O3 system and its subsystems (Y2O3–B2O3 and Al2 O3–B2O3) have been investigated by using combined DTA and XRD measurements to get a better understanding of solid state chemical changes resulting in the formation of yttrium aluminum borate (YAl3(BO3)4, YAB) phase and to study the possible role and contribution of various simple borates formed also in the former processes.Two new exothermic heat effects of YBO3 formation have been detected by DTA in the Y2O3–B2O3 system between 720 and 980°C. In the Al2O3–B2O3 system a new experimental XRD profile of Al4B2O9 was observed. Formation of these borates seems to promote the nucleation of double borate YAB below 1000°C. Conversion of Al4B2O9 to Al18B4 O33 was observed after a long term (10 h) sintering at 1050°C. Similarly, an increased formation of YAB has been observed as a product of the sintering reaction between YBO3 and Al18B4O33 at 1150°C. The two latter single borates are found to be identical with the high temperature decomposition products of YAB.

Characterization of Oil Shales by High Pressure DSC

Pressurised differential scanning calorimeter (PDSC) has been used to obtain information on the pyrolysis and combustion characteristics of oil shales. Two distinct exothermic peaks were identified in combustion experiments known as low temperature oxidation (LTO) and high temperature oxidation (HTO) reaction regions. The pyrolysis process of all studied oil shale samples showed one exothermic effect at each total pressure studied. Kinetic data were analysed by Roger & Morris and Arrhenius methods and the results are discussed.

Determination of the degree of substitution of hydroxypropylated β-cyclodextrins by differential scanning calorimetry

Abstract The general specifications of commercially available hydroxypropylated β-cyclodextrins (HPBCDs) usually give information on the solubility, solubilizing potency and average degree of substitution ( DS ) of a given product. The DS value is regarded as suitable for quality control purposes. This paper describes a differential scanning calorimetric method to determine the DS , based on the fact that the glass temperature interval of the amorphous part of the sample depends on the degree of substitution of HPBCD.

Investigation of Cyclodextrin Complexes of Mandelic acid

The inclusion complexes of both optically active and racemic mandelic acids with α-, (β- and γ-cyclodextrins were prepared by using a liophylisation technique. The compounds formed were investigated by thermoanalytical methods (TG, DSC and EGD) which were completed with FT-IR spectroscopic measurements, scanning electron microscopic observations, and dissolution rate determinations. The inclusion complex formation between all guests and hosts were proven using the thermoanalytical and FT-IR spectroscopic methods.

Mechanism of optical resolutions via diastereoisomeric salt formation. Part 6. Thermoanalytical investigation of the optical resolution of racemic mandelic acid with S-(+)-2-benzylamino-butanol

The optical resolution of racemic mandelic acid (I) by S-2-benzylamino-butanol (II) was performed in water, ethyl acetate, and water saturated ethyl acetate. It was found that the efficiency of the resolution is three times higher in water saturated ethyl acetate than in either water or ethyl acetate. The salt mixtures produced during the resolutions and the pure diastereoisomeric salts were analyzed by TG, DSC and X-ray powder diffraction measurements. The R-(-)-I×S-(+)-II salt has the higher melting point and heat of fusion value which indicates that this is the more stable salt. Though the general assumption is that diastereoisomeric salt pairs of successful optical resolutions form eutectic systems, the R-mandelic acid-S-2-benzylamino-butanol and the S-mandelic acid-S-2-benzylamino-butanol system was found to behave in a different way. Melting did not start at or near the estimated eutectic temperature. The difference can be explained either by miscibility in the solid phase (solid solution) or by a blocked interaction between the crystals of the two solid salts. This unusual behaviour of the salt pair should be responsible for the unusual difference in the efficiency of the resolutions performed in different solvents

Description of Solid-Gas Reactions. Conclusions of Thermoanalytical and Electron Optical Studies on Calcium Carbonate Thermal Decomposition

Thermal decomposition of calcium carbonate was studied with thermoanalytical and electron optical methods. Experimental results detailed in previous papers are discussed from the point of view of kinetic description.Imperfectness of the common kinetic equation using the reacted fraction,α , as the co-ordinate of the reaction and its effect on kinetic parameters are demonstrated. A new type of general equation analogous with physical kinetic laws is proposed for simple, reversible heterogeneous reactions. It is applied for the determination of some characteristics of CaCO3 powder thermal decomposition.

Studies on solid state reactions of ferrimagnetic materials

Abstract Thermogravimetry in a constant magnetic dield was applied to detect magnetizable phases formed in the pre-sintering step of yttrium iron garnet preparation. The method was found suitable to follow the solid state reactions concerned and to characterize the effect of substituents.