Fatcors influencing thermoanalytical curves

Oswald, H. R.; Wiedemann, H. G.

doi:10.1007/bf01909472

Cited by 18 publications

(1 citation statement)

References 26 publications

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“…Many variables affect decomposition reactions [40] but the focus here is on the chemical effects of a product gas atmosphere.…”

Section: Thermodynamic Studiesmentioning

confidence: 99%

Thermal analysis in reactive atmospheres

Gimzewski

1988

Journal of Thermal Analysis

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By using reactive atmospheres, the area of aplb]ication of thermal analysis is expanded considerably to cover many aspects of high temperature research into fuels, extractive metallurgy, materials and catalysts. This article reviews the design of apparatus and its application in kinetic and thermodynamic studies involving atmospheres such as H2, CO, N2, NH3, CO2, H20, SO2or3~ H2 S, $2. C12, HCI, F2 and HF at low or high pressures and as low pressure plasmas. Apart from gas-solid reactions, the important influence of a controlled product gas atmosphere on decomposition reactions is discussed also. Gas-solid adsorption and solubility studies are not included. John Wiley & Sons, Limited, ChichesterAkaddmiai Kiad6, Budapest GIMZEWSKI: ANALYSIS IN REACTIVE ATMOSPHERESTable I Areas of application of thermal analysis using reactive atmospheres ATMOSPHERE APPLICATIONS 02 H2, CO N2, NH3, NO2 C02 H20 802 or3 H2S 02, HCI etc F2, HF etc Plasmas Combustion, extractive metallurgy, oxidation stability tests, carbon analysis. Extractive metallurgy, coal hidrogenation, catalysts, materials science, hydrogen storage. Nitriding using N 2 or NH3, decomposition of catalysts, and propellants in NH3, extractive metallurgy using NO2.Exploitation and analysis of carbonate minerals, processing fuel gases, corrosion.Coal gasification, materials science, reversible dehydration reaction analysis of plaster.Cleaning combustion gases, extractive metallurgy.Cleaning fuel gases, corrosion.Extractive metallurgy, analysis of ceramics.Nuclear fuel processing. Materials science Experimental ApparatusThermal analysis has been performed in gases and vapours at low and high pressures and in low pressure plasmas. Plasmas and vapours pose specific problems discussed below, but otherwise the apparatus design is dictated by the corrosive nature of the atmosphere, its pressure and its flow arrangement. A flowing atmosphere is preferred at normal and high pressures to facilitate mass transfer but at low pressures the atmosphere is usually static. Below, corrosion problems are discussed for furnaces, thermocouples and thermobalances, and the difficulties in generating and using controlled atmospheres are considered separately for gases, vapours and plasmas.s ThermalAnal. 33, 1988

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“…Many variables affect decomposition reactions [40] but the focus here is on the chemical effects of a product gas atmosphere.…”

Section: Thermodynamic Studiesmentioning

confidence: 99%

Thermal analysis in reactive atmospheres

Gimzewski

1988

Journal of Thermal Analysis

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Thermogravimetric Analysis

Dunn

2002

Characterization of Materials

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The formal definition of thermogravimetry (TG is the preferred abbreviation, although TGA is also used) has been given by the Nomenclature Committee of the International Confederation for Thermal Analysis and Calorimetry (ICTAC) as “a technique in which the mass of a substance is measured as a function of temperature whilst the substance is subjected to a controlled temperature programme”. In the above definition, a controlled temperature program means heating or cooling the sample at some predetermined and defined rate. Although it is common to have just one constant heating or cooling rate, it is also advantageous in some cases to have different rates over different temperature ranges and in some cases even a varying rate over a specific temperature range. An apparatus called a thermobalance is used to obtain a thermogravimetric curve. By means of a thermobalance the temperature range over which a reaction involving mass change occurs may be determined. The sample is usually a solid, or more rarely a liquid. Thermogravimetric data can be presented in two ways. The TG curve is a plot of the mass against time or temperature, with the mass loss on the ordinate plotted downward and mass gains plotted upward relative to a baseline. Alternatively, data can be presented as a derivative thermogravimetric (DTG) curve, which is a plot of the rate of change of mass with respect to time or temperature against time or temperature. The DTG mass losses should also be plotted downward and the gains upward. Conventionally, thermal analysis experiments are carried out at a constant heating rate, and a property change is measured as a function of time. An alternative approach is to keep the change in property constant by varying the heating rate. For TG, the rate of mass loss is kept constant by variation in heating rate. To achieve this, the mass change is monitored and the heating rate decreased as the mass loss increases, and vice versa. At the maximum rate of mass loss, the heating rate is a minimum. This gives mass losses over very narrow temperature ranges and sometimes enables two close reactions to be resolved. This method has the advantage of using fast heating rates when no thermal event is taking place and then slowing down the heating rate when a mass change is in progress. Thermogravimetry does not give information about reactions that do not involve mass change, such as polymorphic transformations and double‐decomposition reactions. Also, it is not useful for identification of a substance or mixture of substances unless the temperature range of the reaction has already been established and there are no interfering reactions. However, when a positive identification has been made, TG by its very nature is a quantitative technique and can frequently be used to estimate the amount of a particular substance present in a mixture or the purity of a single substance. The types of processes that can be investigated by TG are given.

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Thermogravimetry (TG)

Hot Topics in Thermal Analysis and Calorimetry

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Fatcors influencing thermoanalytical curves

Cited by 18 publications

References 26 publications

Thermal analysis in reactive atmospheres

Thermal analysis in reactive atmospheres

Thermogravimetric Analysis

Thermogravimetry (TG)

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