C. Oprea

A thermogravimetric study of flame-proofed wool

Abstract A thermogravimetric investigation of K2ZrF6-treated and untreated wool was carried out in air atmosphere. Two regions of major mass losses were analysed and the kinetic parameters of the two decomposition processes were computed. The results suggest that a correlation between the calculated parameters and the treatment level may exist.

Non-Isothermal Crystallization of Cordierite Glasses

A study is reported of the crystallization behaviour of some glass compositions which belong in the system MgO-Al2O3-SiO2 and which lead to vitreous ceramics with α-cordierite as a main phase. DTA, X-ray diffraction and dilatometric analysis were used to investigate the influence of the type and concentration of the nucleation agents. The activation energies of crystallization were calculated and the crystalline phases were identified.

Structure and properties of glasses with a low amount of SiO2 in a quaternary system of Al2O3-SiO2-CaO-MgO

Abstract This study concerns the determination of the compositions of glasses in the quaternary system Al 2 O 3 -SiO 2 -CaO-MgO for SiO 2 concentrations ranging from 4 to 10 mol.%, and the investigation of their structure and properties. The selected compositions were characterised by melting temperatures below 1500 ° C. The glasses obtained were investigated by X-ray diffraction, thermal analysis and IR spectroscopy in order to determine their structures and some important properties, namely, refractive index, density, glass transition temperature and crystallisation temperature.

A comparison of some integral methods

The integral methods proposed to compute the kinetic parameters of heterogeneous reactions under non-isothermal conditions are usually worked by the help of the least squares method and the obtained correlation coefficient is taken as a criterion to choose the best integral method.An analysis of several experimental data by mean of three different integral methods was performed by us and the results pointed out that this criterion, by itself, is not enough to provide reliable information on the kinetic parameters.It appears, thus, that the use of an integral method or another is a simple matter of researchers choice.ZusammenfassungIntegrationsmethoden zur Berechnung kinetischer Parameter von heterogenen Reaktionen unter nicht isothermen Bedingungen werden im allgemeinen nach der Methode der kleinsten Quadrate erarbeitet und der ermittelte Korrelationskoeffizient dient als ein Kriterium für die Auswahl der besten Integrationsmethode.Mittels drei verschiedenen Integrationsmethoden wurde eine Analyse verschiedener experimenteller Daten durchgeführt. Die Ergebnisse zeigen, daß dieses Kriterium allein nicht ausreicht, um ausreichende Informationen über die kinetischen Parameter zu liefern.Es scheint deshalb, daß die Verwendung der einen oder anderen Integrationsmethode einfach eine Wahl des Anwenders darstellt.

The temperature integral

Comparaison entre les integrales de temperatures pour des vitesses de chauffage lineaire et non lineaire en cinetique non isotherme

The crystallization kinetics of 12CaO·7Al2O3 glass

Abstract Various experimental techniques, viz. thermal analysis, IR spectroseopy and X-ray diffraction have been used to analyse the crystallization kinetics of 12CaO·7Al 2 O 3 glass (C 12 A 7 ). The IR spectra and diffraction results confirm the presence of this compound in the final glass with initial molar composition of 7.04% SiO 2 , 30.29% Al 2 O 3 and 62.67% CaO. Use of the Flynn and Wall method has shown that the crystallization process follows two different mechanisms: three-dimensional growth for a low heating rate (up to 5 K min −1 ), and two-dimensional growth for a higher heating rate. The crystallization process is also accompanied by an increase in weight.

Thermogravimetric study of some disperse dyestuffs

Two disperse dyestuffs, though exhibiting similar behaviour upon TG-DTG-DTA, have different dyeing properties. Thermoanalytical investigations are not sufficient to predict dyeing characteristics and fastness.ZusammenfassungZwei Dispersionsfarbstoffe, die sich bei der TG-DTG-DTA ähnlich verhalten, zeigen unterschiedliche Färbeeigenschaften. Thermoanalytische Untersuchungen sind nicht ausreichend, um Färbeeigenschaften und die Farbechteheit vorherzusagen.РЕжУМЕДВА ДИспЕРсНых ОРгАН ИЧЕскИх кРАсИтЕль, НЕсМОтРь НА ОДИНАкОВ ыИ хАРАктЕР Их тг, Дтг И ДтА кРИВых, ОБлАД АУт РАжлИЧНыМИ кРАсь ЩИМИ сВОИстВАМИ. пРОВЕДЕН НыЕ тЕРМОАНАлИтИЧЕс кИЕ ИсслЕДОВАНИь ьВльУт сь НЕДОстАтОЧНыМИ Дл ь ОпРЕДЕлЕНИь Их кРАсь ЩИх хАРАктЕРИстИк И пРОЧНОстИ.

A comparative study of the crystallinity degree of pet by DTA, X-ray diffraction and iodine sorption techniques

PET fibres, with different degrees of crystallinity induced by different thermal treatments have been investigated by DTA, X-ray diffraction and iodine sorption techniques and the results have been compared with the mechanical properties of the yarns spun from these fibres. Values for the degree of crystallinity have been plotted vs. temperature at which thermal treatment was carried out and the curves obtained have been compared with graphs of mechanical properties vs. temperature. Good agreement of the results from the three different methods was obtained.

The use of the derivative differential thermal analysis curve to compute the kinetic parameters of a reaction

Abstract A method based on the use of the two temperatures of the inflection determined on a single derivative differential thermal analysis (DDTA) curve and of the temperature of the extremum determined on the differential thermal analysis (DTA) curve is proposed for computing the activation energy and the order of reaction of a chemical process. The obtained formulae do not contain the heating rate. If the conversion degree corresponding to the three temperatures required by the formulae are known, the third kinetic parameter,A, may be also computed. The formulae are fitted to the reaction order model.