With the discovery of high temperature superconductivity an extraordinary field for investigations on new materials containing up to (more than) 8 or 9 components has been open. But, in addition to problems specifically related to superconductivity, we are faced with a prelimary difficulty: the preparation of well defined compounds which may have reproducible properties. This difficulty is smoothed out when the phase relations in the relevant systems are known. Differential Thermal Analysis (DTA) contributes to their establishment. However, in multicomponent systems, an isopletic line is expected to intercept various boundary surfaces and the analysis is obviously complicated, compared to low order systems. In addition, by the nature of high temperature superconductors the oxygen partial pressure used for their preparation is an important thermodynamic parameter which contributes to fix the oxygen content in the solid state. During heat treatments, the composition of the systems may change, due to oxygen or volatile oxides (Tl2O3, PbO2 or HgO) release. A permanent composition control then requires thermogravimetric (TG) measurements associated to DTA.
Combining time and temperature resolved X-ray powder diffraction with differential thermal analysis (DTA) or differential scanning calorimetry (DSC) is a promising technique for a more detailed understanding of all
Characterization of the solid-state form (hydrate
or polymorph) of a pharmaceutical active is a key scientific and regulatory
requirement during development of and prior to seeking approval for marketing
of the drug product. A variety of analytical methods are available to perform
this task. By nature of the fundamental information it provides, TG-DTA offers
advantages over other methods in regards to monitoring and quantitation of
hydration state changes. In a single experiment with only a few milligrams
of sample, TG-DTA perceives minor changes in phase, quantitates total water
content and percent conversion, and illustrates hydrate type. All of this
is accomplished without the necessity of generating time-consuming standard
curves representing the differing ratios of hydrated to anhydrous forms. This
study describes the use of TG-DTA to monitor and quantitate humidity induced
solid–solid phase conversion of nitrofurantoin and risedronate. Percent
conversion was qualitatively observed by both TG and DTA signals and quantitated
by the TG.
The paper discusses the investigation of crystallization of metals and alloys by differential thermal analysis (DTA). It was
assumed that this method allows determination of the mechanism and kinetics of volumetric crystallization underiso conditions (e.g. anisothermal) on the basis of the parameters of the equation expressing an integral form of the DTA curve.
From DTA, a course of eutectic transformation was determined for a technical Zn−Al alloy containing 4wt% Al. Investigations
were carried out under continuous cooling at various rates and the kinetics parameters were determined with the KEKAM equation:-ln(1-x)=kln
Thermogravimetry and differential thermal analysis, using only a combustion step with oxygen, were used to characterize carbonaceous
products. Binary composition of alumina and wood charcoal, coke, carbon black, petroleum coke or carbon graphite were prepared
containing 5 wt% of each. They were characterized by the burnout onset and DTA and DTG peak temperatures, which range from
476°C for wood charcoal to 790°C for carbon graphite.
Complementary characterization of each product was also performed by estimating the ash content from the TG curves, and the
calorific value from the DTA curves. The results indicate that these thermal analysis techniques, with only one oxygen burnout
step, can be applied both for quality control of each raw material, and to determine the appropriate processing temperatures
of the ceramic compositions in which they are used.
The DTA method has been used for determination of the initial crystallization temperatureTA of the vitreous selenium with admixtures of sulphur (crystallization inhibitor) and tellurium (crystallization catalyst).
It was found that both admixtures raise the value ofTA.
The obtained results suggest that each foreign atom distorts the structures of the chain in vitreous selenium and consequently
inhibits the nucleation.
The values of the heat of transformation and degree of crystallization have been also determined.
scanning electron microscopy (JEOL JSM-6390 LV). The sample was crushed and covered with gold in order to perform these measurements.
The DTA was performed with a SHIMADZU DTA-50 apparatus. About 30 mg sample was used for DTA testing and α-Al 2 O
The crystallization process of Li2B4O7 in the glass of stoichiometric composition, characterized by the crystal growth of pre-existing nuclei, was analyzed kinetically
by means of DTA. Because the number of pre-existing nuclei for the subsequent growth varies depending on the cooling rate
of the glass-forming melt and heating rate of the as-prepared glass, a modified Kissinger plot was applied for evaluating
the apparent activation energy to the crystal growth in the glass samples with three different thermal histories, i.e., the
pre-annealed, slowly quenched and quickly quenched glasses. The process was characterized by the three dimensional growth
of pre-existing nuclei with the apparent activation energy of ca 340 kJ mol−1.
This work is a study, by simultaneous thermogravimetry (TG) and differential thermal analysis (DTA), of the oxidation of a
water resistant aluminum nitride powder which has a special protective coating, and an uncoated AlN powder which has become
partially hydrated during its use. The activation energy for oxidation is estimated by the Kissinger and isoconversional methods.
In the former method, the temperatures of the oxidation peaks were obtained from DTA and DTG curves. The activation energies
for oxidation of the water resistant AlN, obtained by the Kissinger method, are 35710 kJ mol–1, 39212 kJ mol–1 using respectively DTG and DTA data. For the uncoated AlN, the values are 2437 and 2578 kJ mol–1, respectively. By the isoconversional method, the average values obtained for coated and uncoated samples are, respectively,
32310 and 2247 kJ mol–1. Therefore, the special coating, which protects the aluminum nitride from humidity action, also provides a higher resistance
DTA method was used to follow the hydration process of cement admixtures containing fluidized bed combustion by-product, formed
on joined combustion and desulphurisation in some installations with fluidized bed. Based on endothermic peaks attributed
to the dehydration of phases formed on hydration, the conditions leading to the formation of so-called ‘delayed’ ettringite
were found. This calcium alumino-sulphate hydrate is responsible for lower durability of fluidized bed ash containing material.
DTA method is also beneficial in the studies of fluidized bed combustion by-product itself, giving information about the un-burnt
carbon content and pozzolanic properties.