Authors:A. J. Parsons, S. D. J. Inglethorpe, D. J. Morgan, and A. C. Dunham
Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.
Authors:K. Heide, K. Gerth, G. Büchel, and E. Hartmann
Detailed studies of the gas release profiles of minerals and rocks reveal differences in the degassing rates and degassing temperatures and also in the compositions of the fluids evolved from the samples.
A DTA apparatus has been linked to non-dispersive infrared H2O and CO2 analyzers and an SO2 analyzer based on an electrochemical cell, enabling evolution profiles of these three volatiles to be recorded simultaneously with the DTA curve. Examples are given of the use of the combined DTA-EGA method in the determination of the quantitative mineralogical composition of potential industrial raw materials.
Photoionization mass spectrometry (PIMS) with vacuum ultraviolet (VUV) light source provides an efficient and fragmentation-free
method for the soft ionization of gaseous compounds, in order to facilitate an understanding of thermal decomposition behavior
and chemical composition of polymeric materials. The PIMS was applied to the evolved gas analysis (EGA) system equipped with
a skimmer interface which is constituted based upon a jet separator principle between a vacuum MS chamber and an atmospheric
sample chamber in a furnace. A photoionization source with a deuterium (D2) lamp was closely installed to the vacuum ionization chamber of a mass spectrometer to improve the ionization efficiency.
The thermal decomposition of typical polymers in inert gas atmosphere was investigated by the EGA-PIMS and the resulting PI
mass spectrum was characterized satisfactorily by only the parent ions with no contribution as a result of fragmentation during
the ionization. The results suggested that the EGA-PIMS was an especially powerful and desirable in situ thermal analysis
method for polymeric materials which evolve organic gases simultaneously and concurrently. The combination of EGA equipped
with skimmer interface with no change of evolved gaseous species and PIMS with fragmentation-free during the ionization is
described briefly, and the effective results are presented by comparing with EGA using conventional electron impact ionization
Authors:N. Doca, G. Vlase, T. Vlase, M. Perţa, G. Ilia, and N. Plesu
Polyaniline was obtained by oxidizing aniline in hydrochloric acid media with ammonium peroxidisulfate as oxidizing agent.
Molar ratio aniline/oxidant was 1 and aniline/acid ratio: ½, at −5 and 400 °C, respectively, 800 mL water. The both compounds
were studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by decomposition in dynamic
air atmosphere and the kinetic analysis of TG data obtained at four heating rates (5, 7, 10 and 15 K min−1). The kinetic analysis of the TG non-isothermal data was performed with the Flynn–Wall–Ozawa, Friedman’s, and modified non-parametric
kinetic (NPK) methods. By means of the coupled techniques spectroscopic arguments on the reaction mechanism were obtained,
i.e. the oxidative degradation of the quinoine ring as the first step. The values of the activation energy by the three used
methods are in good agreements. According to the NPK method, the termodegradation process consist in physical (diffusion)
and chemical steps.
Authors:F. Gaál, I. Szöllősy, M. Arnold, and F. Paulik
It has been shown that computerized derivatographic method with EGA technique can be applied to determine contents of organic
matter and carbonates in soil samples with satisfactory accuracy and reproducibility of the results. The method enables simultaneous
determination of the ‘mobile’ and ‘bound’ water in the sample.
Hydrazo-carbonates are complex compounds and products of the reactions between solutions of metal ion and solutions of hydrazido-carbonic
acid. The decomposition of Mg(N2H3COO)2. 2H2O, Ca(N2H3COO)2·H2O and Zn(N2H3COO)2 in inert atmosphere were studied. By classical thermoanalytical methods and data on the composition of the intermediates
and final products the mechanisms of the thermal decomposition could not be resolved therefore also evolved gas analysis was
used (EGA). The first step of thermal decomposition of Ca and Mg hydrazidocarbonates is dehydration. With the heating the
decomposition of the hydrazido-carbonates proceeds under evolution of the ammonia, carbon monoxide and/or nitrogen and carbon
dioxide giving as the intermediates for calcium and magnesium compounds the corresponding carbonates oxides as the final products.
The zinc compound decomposes to the oxide, ZnO but also zinc cyanamide was detected during to the thermal treatment.
Authors:A. Małecki, R. Gajerski, S. Łabuś, B. Prochowska-Klisch, and K. Wojciechowski
A series of six nitrates(V) hydrates of 4d-metals as well as mercury and cadmium thermal decomposition was examined by DTA,
TG and EGA techniques. It was found that thermal decomposition of d-metals nitrate(V) hydrates proceeds in three stages: partial
dehydration, oxo-nitrates and hydroxide nitrates formation and metal oxides formation. General chemical equations for all
decomposition stages were proposed. It was found that dehydration of hydrated salts is accompanied by partial decomposition
of nitrate(V) groups.
Identification and monitoring of gaseous
species released during thermal decomposition of pure thiourea, (NH2)2C=S
in argon, helium and air atmosphere have been carried out by both online coupled
TG-FTIR and simultaneous TG/DTA-MS apparatuses manufactured by TA Instruments
(USA). In both inert atmospheres and air between 182 and 240°C the main
gaseous products of thiourea are ammonia (NH3) and
carbon disulfide (CS2), whilst in flowing air sulphur
dioxide (SO2) and carbonyl sulphide (COS) as gas phase
oxidation products of CS2, and in addition hydrogen
cyanide (HCN) also occur, which are detected by both FTIR spectroscopic and
mass spectrometric EGA methods. Some evolution of isothiocyanic acid (HNCS)
and cyanamide (NH2CN) vapours have also observed mainly
by EGA-FTIR, and largely depending on the experimental conditions. HNCS is
hardly identified by mass spectrometry. Any evolution of H2S
has not been detected at any stage of thiourea degradation by either of the
two methods. The exothermic heat effect of gas phase oxidation process of
CS2 partially compensates the endothermicity of the
corresponding degradation step producing CS2.
Authors:F. Paulik, J. Paulik, É. Buzágh-Gere, and M. Arnold
The thermal behaviour of anhydrous CaBr2 in N2 and O2 atmospheres containing H2O was investigated with the method of simultaneous TG, DTG, DTA and EGA (derivatograph). A method for the continuous determination of the amounts of Br2 and HBr evolved from the heated sample was elaborated in the presence of each other, and the course of the gas evolution was followed. It was found that water vapour does not react with CaBr2 in either a N2 or an O2 atmosphere, and no HBr is liberated. Under the given conditions CaBr2 completely decomposed in an O2 atmosphere between 500 and 1000°, with the formation of CaO and Br2, while in a N2 atmosphere between 700 and 1000° the material lost about 3 % of its original weight, due to evaporation.