Simultaneous TG-DSC - with supreme resolution in all ranges
STA 449 C Jupiter® – Simultaneous TG-DSC
Hard Metal
Hard metals are used, in particular, when high wear resistance, hardness and fracture toughness are required (e.g. boring heads). For shaping, the hard metal powder is often charged with organic binders, which are burned out before the actual sintering. The binder (melting point about 57°C) is driven out of the work piece in several steps. Sintering begins at about 922°C (extrapolated onset) and is recognizable as an exothermal process in the DSC curve. At about 1340°C (peak temperature), the eutectic WC/Co mixture melts. By further increasing the temperature, more and more WC is released, according to the phase system.
High Accuracy: Mixture of Al2O3, Quartz Sand and CaCO3
The high accuracy of the balance and the simultaneous heat flux DSC enable, for example, phase analysis of mixtures. The weight-loss step of 0.43% at approx. 600°C is caused by the 0.98 wt% component CaCO3. Comparison of the phase transition enthalpy of the SiO2 component with the enthalpy of the quartz sand confirmes that the weight component of the sand is 2.2% of the mixture. Starting at approx. 1000°C the mixture sinters, releasing energy in the process (exothermal reaction).
Composition of cement raw materials
The measurement clearly demonstrates that the gases evolved from the sample can be identified and partly quantified by means of simultaneous thermal analysis and simultaneous QMS analysis. The two mass-loss steps between
approx. 250°C and 450°C are due to the combustion of organic components. This is indicated by both the exothermal DSC signal and the detected QMS signal for water and CO2. Moreover several dehydration steps below 600°C can be seen. The decomposition of CaCO3 between 600°C and 850°C as well as the decomposition of CaSO4 between 1200°C and 1350°C can clearly be detected by means of the MS signals. Further, some not oxidized organic decomposition products are visible around 336°C by the QMS signal.
TG-DSC measurement up to high temperatures
The Al(OH)3 powder sample (57.070 mg sample weight) was heated in dynamic air atmoshere with 5 K/min up to 1500°C. The excellent thermal symmetry in the rhodium furnace of the STA 449 C Jupiter® could be further increased related to the DSC by using 53 mg Al2O3 reference material. The outstanding stability of all signals allows evaluation of the TG-steps for the stochiometrical dehydration of the hydroxide with the corresponding enthalpy changes up to 600 °C, and in the range from 1000°C to 1300°C the solid-solid transition of the water free γ-alumina in two steps to the α- Al2O3 (DSC peaks without TG change) can clearly be detected.
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