For a large number of DSC calibration substances the vapour pressure at room temperature or at transition temperature (whichever is the highest) is given. It is important to know the vapour pressure of substances, because a DSC measurement on a substance with a high vapour pressure requires encapsulation of the substance in a hermetically sealed crucible to prevent evaporation. Because the calibration procedure must be performed using the same type of sample pan as will be used during the actual measurements, the presented information allows one to decide which calibration substances and/or what type of sample pan should be used for calibration.
This contribution deals with the calibration of a DSC apparatus between −100 and 0°C using compounds with well-known temperature
and heat of transition. Only a few suitable substances are mentioned in literature. For that reason another compound, adamantane,
is proposed with a solid-solid transition at −64.56°C and a heat of reaction being 24.78 J/g.
A number of compounds are investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions
and can be applied both for temperature and for heat calibration. A third compound, namely 4,4′-azoxyanisole, has a liquid
crystal to isotropic liquid transition at 409 K. This compound can be used for temperature calibration. Heat calibration with
this compound is more problematic because of the small heat effect and the construction of the baseline. Two other compounds,
namely Hg and Pb, show a slight undercooling. Nevertheless they can be used for heat calibration, and possibly also for temperature
calibration during cooling.
DSC analysis of wax/polymer blends is carried out between 270 and 420 K. Calibration for melting point and enthalpy is normally
carried out using indium (melting point 430 K), which is unsatisfactory for these materials. IUPAC organic standards covering
this range tend to sublime and their onset temperatures are variable. Pure alkanes have similar thermal characteristics to
wax/polymer blends and some have been well characterised by adiabatic calorimetry. They are being investigated as alternative
secondary calibration standards to give more accurate thermal characterisation of wax/polymer blends. Also,n-triacontane can be used to check DSC resolution.
A number of compounds is investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions
and can be applied both for temperature and for heat calibrations. A third compound, namely 4,4’-azoxyanisole, has a liquid
crystal to isotropic liquid transition at 409K. This compound can be used for temperature calibration. Heat calibration with
this compound is more problematic because of the small heat effect and the construction of the baseline. Other compounds like
NaNO3, In, Hg and Pb, show a slight supercooling. Nevertheless they can be used for heat calibration. The use of large samples
of NaNO3 and In gives the possibility to construct the equilibrium onset temperatures of the cooling peaks, so these two compounds
are also appropriate for temperature calibration on cooling.
Authors:G. Airoldi, G. Riva, B. Rivolta, and M. Vanelli
The unusual mechanical properties (i.e. shape memory effect and superelasticity) of shape memory alloys (SMA) rely on the thermoelastic martensitic transformation (TMT) which is a first-order solid-solid, non-diffusive phase transition, athermal in character.
Differential scanning calorimetry (DSC) is often used as a convenient method of investigating the thermal properties ofSMAs. The common practice of standard temperature calibration, required for a correct instrument performance, is here critically
discussed in relation to the study of both the direct exothermic transformation on cooling, and the reverse endothermic transformation
on heating in a NiTiSMA. The DSC results show that, with the standard temperature calibration, the instrument is calibrated on heating but un-calibrated
on cooling. A general method is advanced to overcome this problem, intrinsically related to the dynamic character of DSC.
Authors:J.C.M. Muller, G. Hakvoort, and J.C. Jansen
Differential scanning calorimetry has been used to study the thermal effects during adsorption and desorption of water on
different zeolite NaA samples. An attempt has been made to compare the thermal behaviour of a layer of zeoliete attached on
metal ("by chemical bond") with zeolite powder pressed on metal. The dependence of the water uptake on temperature has been
studied with a powdered sample.
Isothermal measurements of the water uptake of the zeolite after activation, appeared the best way to determine the heat of
adsorption. Calibration of the DSC was needed. The adsorbed amounts of water corresponding to the released heats were determined
thermogravimetrically. Once the heat of adsorption is known, it is possible to determine the mass of active zeolite of thin
synthesized zeolite layers on metal with DSC.
. Practical recommendations on the DSCcalibration prepared by GEFTA use only empirical data fitted to a parabola over the temperature range of 100 °C ( Fig. 3 ) [ 19 , 20 ]. There is no theoretical background for the parabola fitting the calibration
Two compounds are described with interesting properties for use in DSC. The first compound is adamantane (C10H16), with a reversible solid-solid transition at 208.62 K , suitable for DSC calibration at this low temperature . The second compound is 4,4'-azoxyanisole (C14H14N2O3), with a liquid crystal range between 390 and 407 K . This compound shows two transitions on heating, with a large heat effect at 390 K and a small heat effect at 407 K. For this reason, this substance is well suitable for testing the sensitivity and the resolution of DSC instruments . For both compounds not only the heating, but also the cooling behaviour is investigated.
Working groups of the German Society for Thermal Analysis (GEFTA) are active in the fields of calibration of dynamic calorimeters
(DSC), calibration of dilatometers, evaluation of DSC curves and standard samples for dynamic mechanical analysis (DMA). Two
papers on the temperature calibration of DSC instruments have been published, which recommend a calibration procedure and
calibration materials. Another recommendation on caloric calibration is in preparation. Certified calibration samples for
dilatometers are available for the temperature range −190° to 700°C.