Thermogravimetric analysis apparatus

Thermogravimetric analysis (TGA) measures changes in weight of a sample being heated. A typical Thermogravimetric analysis (TGA) apparatus is shown in the following diagram ... 

Fig. 14 Schematic diagram of apparatus suitable for thermogravimetric analysis. The experimental observable is the percent weight loss of the sample, which will be plotted as a function of the system temperature.

The data (Table II) for the percent residue at 500°C under isothermal thermogravimetric analysis also show reasonable agreement with the data for the residue from the experiments in the FMRC Small-Scale Flammability Apparatus where large-scale fire conditions are simulated. Thus, the TG analysis for flammability assessment of FRC materials may be more useful than previously considered. 

The nature of the material to be studied, which means its degree of crystallinity and perfectness of crystal structure, may have a significant effect on the thermoanalytical behavior. In spite of identical chemical composition of a certain material the variations with respect to structure, imperfections, grain boundaries, etc. are almost infinite. Of course many of these will not show in normal thermogravimetric analysis, with very sensitive apparatus characteristically different TG curves18, 19 may be obtained however. As an example Fig. 26 shows the thermal decomposition of hydrozincite, Zn5(OH)6(003)2, whereby equal amounts of samples from natural origin and synthetic preparations are compared. 

The fresh and spent catalysts were characterized with the physisorption/chemisorption instrument Sorptometer 1900 (Carlo Erba instruments) in order to detect loss of surface area and pore volume. The specific surface area was calculated based on Dubinin-Radushkevich equation. Furthermore thermogravimetric analysis (TGA) of the fresh and used catalysts were performed with a Mettler Toledo TGA/SDTA 851e instrument in synthetic air. The mean particle size and the metal dispersion was measured with a Malvern 2600 particle size analyzer and Autochem 2910 apparatus (by a CO chemisorption technique), respectively. 

The equipment consisted of a microbalance suitable for thermogravimetric analysis (TGA), with an integral sample collector and an on-line gas chromatograph (GC) see Figure 1. Details of the apparatus have been presented before see e.g., Ref. 

Thermogravimetric analysis can be perfonned with heating rates up to 108 K/min without significant temperature gradients inside small samples. An STA apparatus enabling a temperature calibration under the exact experimental conditions will give reliable process temperatures. This allows kinetic modelling without consideration of the enthalpy balance. 

The use of thermogravimetric analysis (TGA) apparatus to obtain kinetic data involves a series of trade-offs. Since we chose to employ a unit which is significantly larger than commercially available instruments (in order to obtain accurate chromatographic data), it was difficult to achieve time invariant O2 concentrations for runs with relatively rapid combustion rates. The reactor closely approximated ideal back-mixing conditions and consequently a dynamic mathematical model was used to describe the time-varying O2 concentration, temperature excursions on the shale surface and the simultaneous reaction rate. Kinetic information was extracted from the model by matching the computational predictions to the measured experimental data. 

Thermogravimetric analysis (TGA) for the estimation of carbon amount was carried out by using a Shimadzu DTG-60 apparatus. The analysis was done with 10 mg catalysts under flowing air (20 cm /min) at 15 K/min heating rate. The... 

Thermal stability of hemicelluloses was performed using thermogravimetric analysis (TGA) on a thermal analyzer (TA Instruments High-Resolution Model Q-500). The apparatus was continually flushed with nitrogen. The samples weighed between 10 and 13 mg and were run fiom room temperature to 600 °C at a rate of 10 °C/min. 

The optimal calcination method for zeolite beta was established by thermogravimetric analysis using a PL-Thermal Sciences STA 1500 apparatus. Chemical compositions of the zeolites were determined by atomic absorption spectroscopy on a Varian AAIO spectrometer after dissolution of the samples in hydrofluoric acid. The structure was confirmed by x-ray diffraction on a Siemens D-5000 diffractometer and with infrared spectroscopy on a Mattson Instruments Galaxy 2000 spectrometer. Total surface area, micropore area and micropore volume of the samples were determined by argon adsorption on a Micromeritics ASAP 200M volumetric analyzer using standard techniques. Crystal diameters were determined by scanning electron microscopy. 

The LaxM(fsa)2cn,N03.H20 complexes (M = Ni, Cu) and some of their pyrolysis products were characterized by Elemental Analysis (Laboratoire Central d Analyse, C.N.R.S., Vernaison, France) in order to control their stoichiometry. Thermal treatments of the complexes and of Mont/LaxM(fsa)2en,H20 were carried out in a ThermoGravimetric Analysis (T.G.A.) apparatus coupled with a Balzers QMG 420 C mass spectrometer, under 02/Ar (1/1, 15 ml/min) atmosphere with a 100°C/h temperature ramp. KBr pellets (0.5% dispersion in O.lg KBr) were analyzed by Infra-Red spectrometry (Nicolet 710 FT-IR spectrometer). X-Ray diffractograms of powdered solids spread on a glass plate were recorded on a Siemens D500 diffractometer (Cu Ka radiation, X = 1.54056 A) in the reflection mode. ... 

The first measurements of molecules that were involved during thermogravimetric analysis were reported by Lephardt and Fenner [50,51], who showed the time evolution of several gases that are evolved when tobacco or other thermally labile samples are heated. Despite the obvious information that this experiment yielded and the simplicity of the apparatus, it took several years for instrument companies to introduce a commercial TGA/FT-IR interface. The gas cell installed in these systems is much... 

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