An implicit heating programme to minimize the effect of the difference between the sample temperature and the programmed temperature

An implicit heating programme is suggested for minimization of the effect of the difference between the sample temperature and the programmed temperature in a thermoanalytical set-up.

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Zusammenfassung Es wird ein implizites Aufheizprogramm beschrieben, das den Einfluss des Unterschiedes zwischen Probentemperatur und programmierter Temperatur für die Probe minimalisiert.

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Thermal behaviour of CO2 laser-irradiated CeO2 doped with Yb2O3

Results concerning the thermal behaviour of Yb₂O₃-doped CeO₂ samples irradiated with CO₂ laser beams in continuous wave are presented.

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Zusammenfassung Es werden Ergebnisse einer Untersuchung des thermischen Verhaltens von CeO₂-Proben dargelegt, die mit CO₂-Laser bestraht wurden.

     

Applicability of the Kissinger equation in thermal analysis

Pt/WO_x–ZrO₂ bifunctional catalysts were synthesized using impregnation and polymeric precursor methods. After the synthesis process the samples were calcined at 600, 700 and 800°C and characterized by X-ray diffraction, nitrogen adsorption and temperature programmed reduction study by thermogravimetry. DTG-TPR profiles showed between three and five reduction events at different temperatures attributed to platinum reduction and to different stages of tungsten species reduction. A comparative study of the synthesis method influence on the DTG-TPR curves was accomplished.     

Some problems concerning the evaluation of non-isothermal kinetic parameters

The validity of isoconversional methods used to evaluate the activation energy is discussed. The authors have shown that the Flynn-Wall-Ozawa and Friedman methods give results that agree with each other only if the activation energy does not change with the degree of conversion. A criterion for the reaction mechanism as expressed by the differential conversion function is suggested too.     

Reduction of 1-formyl-1,2,3,4-tetrahydroquinoline with ethyldiphenylsilane

Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 424–425, March, 1995.Original article submitted February 14, 1995.     

One Pot Synthesis of 1-Chloro-2-Chlorocarboxy-4H-Quinolizin-4-One and Its Derivatives

Condensation of 2-pyridine acetic acid with thionyl chloride under reflux conditions generates the title compound in one step with >95% yield. Its reactivity toward alcohols and amines were investigated. All of the derivatives were characterized by NMR and MS analysis. One of its derivatives, 1-chloro-2-methoxycarboxy-4H-quinolizin-4-one, 5, was also characterized by X-ray diffraction studies.     

Sestak–Berggren function in temperature-programmed reduction

From the peculiarities of Temperature-programmed reduction (TPR) method and using the Sestak–Berggren conversion function, we describe first the TPR curve simulation procedure. The influence of the Sestak–Berggren exponents on the TPR peak maximum and shape is demonstrated, by analyzing several synthetic TPR profiles. Finally, the kinetic parameters of Au/CeO₂ promoted with yttrium as well as those of Au/CeO₂–Al₂O₃ promoted with V₂O₅ are discussed.     

Plastic flow for axisymmetric-tension specimens with necking

Plastic deformation of a tension specimen bounded by a curved surface of revolution is considered. Such a configuration may occur, for example, as a result of necking. The specimen material satisfies the Tresca yield condition and the associated flow rule. Approximate solutions for the stress distribution in the neck were examined in [6]. The extension of notched bars was investigated by numerical and graphic methods in [2, 4]. Below, the problem is solved analytically for a sufficiently smooth neck; a small degree of nonuniformity of the plastic properties is taken into account.     

A Dilatometric Investigation of the Thermal Compaction of Ferrite Powders Prepared by Coprecipitation

The authors report on a non-isothermal kinetic investigation (at constant heating rate) of the sintering of manganese and nickel-zinc ferrite powders prepared by coprecipitation. The kinetic results point to the thermal compaction of the powders, which occurs mainly in the intermediate stage of sintering. A comparative study was performed in order to determine the influence of the sample characteristics (such as chemical nature, density and shape) and the heating rate on the kinetics and mechanism of the compaction. This revised version was published online in August 2006 with corrections to the Cover Date.