The influence of the alloying elements magnesium, copper and silicon on phase transformations in Al-60 wt% Zn alloy solidified at rates from 0.4 up to 65 deg/s has been investigated by means of DTA method.
Chemical component exchange and transport phenomena accompanying the multistage phase transformations of several silicate and aluminosilicate-phosphate glasses and borates as model systems are considered. It is demonstrated that the component transport limitations modify the role of chemical affinity influence and determine the sequence of new compound formation.
Authors:C. Bhongale, A. Ghule, R. Murugan, and H. Chang
In this work, dehydration of sodium diphosphate decahydrate Na4P2O7⋅10H2O and phase transformations of Na4P2O7 in open air have been studied in detail by thermo-Raman spectroscopy. The spectra were measured continuously in a temperature
range from room temperature up to 600C for the bands of P2O74- and H2O. The spectral variation showed one step of dehydration and four-phase transformations. The thermo-Raman intensity(TRI) and
differential thermo-Raman intensity (DTRI) curves calculated from the characteristic bands of H2O also showed one step of dehydration with the loss of all hydrated water in the temperature interval from 45 to 69C. Thermogravimetric
measurements supported this result. The thermo-Raman investigation indicated the transformation of Na4P2O7 from low temperature phase to high temperature phase proceed through pre-transitional region from 75 to 410C before the
major orientational disorder at 418C and minor structural modifications at 511,540 and 560C. The results from differential
scanning calorimetry and differential thermal analysis on Na4P2O7 showed endotherms at 407,517, 523, 548, 557C and 426, 528, 534, 555, 565C, respectively.
An increase of the specific surface area of solid phases is often desirable e.g. for the bioavailability of pharmaceuticals or in chemical processes. Such an increase can a.o. be achieved by suspending crystalline substances in a solvent that induces phase transformations. Hence, the original substance has to be in a metastable state in the solvent. If the stable phase after transformation has in addition a very low solubility in the solvent, a dendritic growth is forced to occur because of the high local supersaturations during the phase change. This dendritic growth of the stable phase in term leads to needle- or whisker-like crystals, which have the desired larger specific surface area in comparison to the initial crystalline substance.In order to investigate this phenomenon several hydrates of salts were chosen, which undergo phase transformations to their anhydrates accompanied by a corresponding loss of crystal water when suspended in excess in lower alcohols. Consequently, anhydrous forms were created by dehydrating these hydrates. The transformation rate or in this case the dehydration level can thus be indirectly measured by Karl-Fischer titration. The thermodynamic background of the dehydration phenomena can be clarified by solubility studies of the hydrates and anhydrates in water/alcohol-mixtures.
The Cu-Ni-Sn ternary phase diagram in the Cu rich side has not been experimentally determined or calculated at low temperatures.
Two Cu9NixSn alloys with x=2 and 6 mass% Sn were studied. The precipitation sequence during the ageing and phases responsible for the strengthening
Authors:Stefano Gialanella, Fabrizio Girardi, Gloria Ischia, Ivan Lonardelli, Maurizio Mattarelli, and Maurizio Montagna
, interesting to monitor the evolution of goethite first and, then, of hematite.
Synchrotron radiation diffraction patterns displaying the evolution of the phasetransformation of goethite ( G-peaks ) into
Phase transformations in Cu-12.4% Al and Cu-14.4% Zn-8.4% Al alloys were examined by DTA. The influence of the rate of temperature change on the sequence of phase transformations was studied. It was found that the rates of heating and cooling were the major factors determining the transformations which take place in these alloys.
The purpose of this study is to elucidate the nature of the phase transformations of lead monoxide powder. Lead monoxide is prepared by calcination of a lead oxalate precursor salt, and its phase transformations are studied using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TG). Analysis reveals that the phase transformations observed for oxalate-derived lead monoxide powder are highly dependent on the firing atmosphere. In nitrogen, as the temperature is increased 1 deg/min from room temperature, lead monoxide undergoes a reconstructive litharge-to-massicot phase transformation in a temperature range of 525–575°C. In air, litharge, metastable at room temperature, slowly oxidizes to the Pb3O4 phase at a temperature of 350°C and rapidly reduces to litharge at 560°C. At temperatures greater than 560°C, litharge converts to massicot. With heating rates of 10 deg/min or higher, formation of Pb3O4 is not observed.
Syrian phosphorite is subjected to mechanochemical activation carried out in planetary mill. Some phase transformations are
ascertained by means of powder XRD and thermal analyses. They reveal as partial transformation of carbonate fluorine apatite
into carbonate hydroxyl fluorine apatite and formation of Ca(PO3)2, as well. The solubility of the activated sample in 2% citric acid is increased as a result of these changes.