Hot luminescence study of the intramolecular thermal bath of aromatics

We report a hot luminescence study of the vibrational relaxation in the S₁ state of anthracene and perylene in various solid matrices at 4.2 K. A set of relaxational data is evaluated and presented. The need of an external thermal bath at the initial stage of relaxation of these molecules is discussed. Some problems of distinction of resonant secondary emission components are illustrated by the mixed crystal spectra. A novel approach to the separation of scattering and hot luminescence in strongly inhomogeneous spectra at resonant excitation is introduced.     

Controlled-rate thermal analysis

Controlled-rate thermal analysis (CRTA) and differential scanning calorimetry (DSC) were used to investigate the adsorbed water layers and the surface properties of different commercial activated carbons. A simple method is proposed to obtain information on the properties of the adsorbed water film and the surface heterogeneity of the materials studied. This method utilizes TG mass loss and the first derivative of the DTG mass loss curves with respect to temperature and time, obtained during programmed liquid thermodesorption. The obtained TG mass loss curves, which reflect the energetic heterogeneity, consisted of steps and inflections which were associated with the mechanism of wetting of the solid surfaces. The heights of these steps and inflections depend on the adsorption capacity, the adsorption potential and the nature and number of the active centers of the carbon samples studied. The values of the total porosity and the surface phase capacity obtained by this method are in good agreement with those estimated on the basis of independent methods. The behaviour of water/carbon samples was studied by means of DSC at subambient and elevated temperatures. The experimental results provided novel data on the structural heterogeneity, the thermal stability of the water/carbon interface and its phase and structural transitions.Support from the Research Council of Kent State University (Ohio, USA) is acknowledged. The author is pleased to thank Drs M. Jaroniec, R. K. Gilpin, J. Choma and R. Dobrowolski for fruitful discussions and the active carbon samples.     

Oxyreactive thermal analysis

The paper presents the applicability of Oxyreactive Thermal Analysis (OTA) for the investigation of different kinds of carbon matter. For comparative reasons and more precise interpretation, along with OTA some physico-chemical properties of analyzed materials were used as the methods commonly applied for the investigations. The carbon materials of both natural (anthracites, graphite and diamonds) and synthetic origin (active carbon, glass carbon, expanded graphite, soot and synthetic diamonds) were investigated. It was stated that there is close relationship between structure parameters and physico-chemical properties and the thermal reactivity within the investigated groups of carbon matters. The results show that OTA can be accepted as a good investigative way for such materials. This revised version was published online in July 2006 with corrections to the Cover Date.     

Emanation thermal analysis

A high pressure differential thermal analysis (DTA) apparatus is described which is capable of operation in the pressure range up to 500 MPa and at temperatures from 25 to 300°C. The requirements for quantitative DTA are examined. The apparatus enables the determination of heat of transition under high pressure by using small samples.     

Dielectric-differential thermal analysis

A quantitative relation is given for the temperature function of the output voltage is thermodielectric analysis. Results obtained with zeolites show the validity of the equation.     

Applications of thermal analysis

This review paper outlines some current developments in thermal analysis. The current status of standard methods, in particular those issued by the American Society for Testing and Materials (ASTM), using thermal analysis techniques are discussed. In the second place a simple method for the determination of the oxidative stability of polyethylene by DTA is reviewed. Finally the paper surveys some of the more recent work being carried out in fossil fuels and fuel oils.

---

Zusammenfassung Dieses Referat umreisst einige zeitgemässe Entwicklungen der Thermoanalyse. Es wird der derzeitige Stand der Standardmethoden besprochen, besonders derjenigen, die durch die American Society for Testing + Materials (ASTM) veröffentlicht wurden, und die ein thermoanalytisches Verfahren verwenden. In zweiter Reihe wird eine einfache Methode zur Bestimmung der oxydation Stabilität des Polyäthylens mittels DTA bekanntgemacht. Zum Schluss übersieht die Arbeit einige neuere Arbeiten, die an festen Heizmaterialien und Heizölen durchgeführt wurden.

---

. , , , ASTM. ' . , .

     

Quantitative thermal analysis,I Mathematical problems of quantitative differential thermal analysis

A highly simplified method for calculating heat of phase transitions from DTA data is presented. Two DTA curves are needed to calculate the heat of transition and the specific heat of the sample: one is for the original sample and one is for a sample prepared by mixing the original sample with some unreactive diluent the specific heat of which is known. The data of the DTA curves used in the calculations are the peak area, the rate of heating and the deviation of the DTA curve from the base line.

---

Zusammenfassung Eine einfache Methode zur Errechnung der Werte der Phasenübergangswärme aus den DTA Daten wird besprochen. Die Kenntnis der spezifischen Wärme der betreffenden Substanz und zwei Thermogramme sind hierzu nötig, jenes der Originalprobe und jenes einer Mischung der zu prüfenden Substanz mit einem indifferenten Stoff von bekannter spezifischer Wärme. Die notwendigen DTA Daten sind die Spitzenflächen, die Erhitzungsgeschwindigkeit und die Abweichung der DTA Kurve von der Nullinie.

---

Résumé On décrit une méthode simple pour caIculer les chaleurs des transitions de phase à l'aide des données d'analyse thermique différentielle. Il est nécessaire de connaître la chaleur spécifique et les thermogrammes de l'échantillon pur et en mélange avec une substance indifférente, de chaleur spécific connue. Pour les calculs, on se sert des données suivantes: surface des pics d'A. T. D., vitesse de chauffage et déviation de la courbe d'A. T. D. par rapport à la ligne de base.

---

(). () , . : , () .

     

Standardization in thermal analysis

The present state of the certification of the reference materials for thermal analysis is considered. Six sets of reference materials for temperature calibration, resulting from the research work of the ICTA Standardization Committee, are discussed.

---

Zusammenfassung Die gegenwÄrtige Lage der Attestierung von Referenzmaterialien für die thermische Analyse wird erörtert. Sechs Sets von Referenzmaterialien, die vom ICTA-Standardisierungskomitee zur Temperaturkalibrierung in Vorschlag gebracht wurden, werden diskutiert.

---

. , .

---

---

The author is most grateful to Professor P. D. Garn, Akron University, USA, and to Dr. Robert C. Mackenzie, The Macaulay Institute for Soil Research, Aberdeen, Scotland, for published material and unpublished data concerning the problems of ICTA standards and the nomenclature of thermal analysis.     

Kinetic applications of thermal analysis

A study was undertaken to compare two computational methods of estimating kinetic parameters from thermoanalytical experiments. Examples illustrating the relationship between reaction complexity and validity of isothermalvs. non-isothermal kinetic analyses will be presented. Thermal decomposition of several compounds was studied both by isothermal and dynamic thermogravimetry (TG). For the isothermal runs, reaction order and activation energy were estimated using established methods. For the dynamic runs, the statistical method of nonlinear least squares was used to estimate all three kinetic parameters of the nth order decomposition reaction and their individual 95% confidence intervals. Both methods assumed Arrhenius temperature dependence.

---

Zusammenfassung Es wurde eine Untersuchung zum Vergleich von zwei Methoden zur Berechnung von kinetischen Parametern aus Ergebnissen thermoanalytischer Experimente unternommen. Beispiele werden angegeben, die die Beziehung zwischen isothermer und nichtisothermer kinetischer Analyse in Bezug auf Komplexizität der Reaktion und Gültigkeit illustrieren. Die thermische Zersetzung verschiedener Verbindungen wurde mittels isothermer und dynamischer Thermogravimetrie (TG) untersucht. Aus den isothermen Versuchsergebnissen wurden die Reaktionsordnung und Aktivierungsenergie nach den üblichen Methoden bestimmt. Aus den dynamischen Versuchsdaten wurden alle drei kinetischen Parameter der Reaktion n-ter Ordnung und deren individuelle 95%-Konfidenzintervalle nach der Methode der kleinsten Fehlerquadrate ermittelt. Beide Methoden setzen eine Temperaturabhängigkeit entsprechend der Arrhenius-Gleichung voraus.

---

, . , . , . . n- 95% . .

---

---

Presented at the 13th North American Thermal Analysis Society Conference, Philadelphia, PA 23–26 September 1984.     

Dielectric differential thermal analysis

The present paper deals with the role of guest molecules in the moleculer sieves systems.     

Differential thermal analysis of montmorillonite

The paper provides an overview of publications on the DTA of montmorillonites (in the temperature range 20–1100°C), starting with the first experiments of Le Chatelier (1887) and ranging up to the present. Consideration is given to the dehydration, dehydroxylation, amorphization and rehydration of montmorillonite (42 references).     

Computer aided thermal analysis

Inverse numerical techniques have been applied in a range of different thermal studies in the past. These techniques require measurements of boundary conditions and temperatures at known position within the sample in order to determine thermal properties of the material of interest. Typically, they have been applied to highly specific applications and designs. In the current work the authors have designed a novel instrument in order to measure apparent specific heats of a range of different materials during continuous heating. Measurements of surface heat flux, surface and centre temperatures of the sample were obtained under controlled heating for temperatures of up to 1000°C. Measured data was used to quantify specific and latent heats by employing inverse numerical modelling technique. The instrument was calibrated with calorimetric calibration materials and results were compared with the literature values. The average experimental error was estimated to be approximately 0.9% for the reaction peak temperatures and 1.7% for the latent heats. Detailed experimental and calculation procedures as well as measured results of specific heat and enthalpy for a number of materials are presented here. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dielectrical differential thermal analysis

Sodium faujasites with different Si/Al ratios were studied by means of thermodielectrical method.