Scanning Rate Extension of Conventional DSCs through Indirect Measurements

In this work, a method is presented which allows the determination of calorimetric information, and thus, information about the precipitation and dissolution behavior of aluminum alloys during heating rates that could not be previously measured. Differential scanning calorimetry (DSC) is an established method for in-situ recording of dissolution and precipitation reactions in various aluminum alloys. Diverse types of DSC devices are suitable for different ranges of scanning rates. A combination of the various available commercial devices enables heating and cooling rates from 10−4 to 5 Ks−1 to be covered. However, in some manufacturing steps of aluminum alloys, heating rates up to several 100 Ks−1 are important. Currently, conventional DSC cannot achieve these high heating rates and they are still too slow for the chip-sensor based fast scanning calorimetry. In order to fill the gap, an indirect measurement method has been developed, which allows the determination of qualitative information, regarding the precipitation state, at various points of any heat treatment. Different rapid heat treatments were carried out on samples of an alloy EN AW-6082 in a quenching dilatometer and terminated at defined temperatures. Subsequent reheating of the samples in the DSC enables analysis of the precipitation state of the heat-treated samples. This method allows for previously un-measurable heat treatments to get information about the occurring precipitation and dissolution reactions during short-term heat treatments.

Cure Monitoring of Epoxy Resin by Simultaneous DSC/FTIR

The cross-linking kinetics of an epoxy/amine resin system was studied using the conventional DSC and FTIR spectroscopy, respectively. Conventional DSC was modified to accommodate two fibre optic probes which could be used to monitor the spectra of epoxy/amine resin system during cure. The cross-linking kinetics for the epoxy/amine resin system obtained via the conventional DSC and FTIR and simultaneous DSC/FTIR were similar. The feasibility of using a simple bifurcated fibre optic probe to link the DSC to the FTIR spectrometer was demonstrated.

Study of dynamic features of highly energetic reactions by DSC and High-Speed Temperature Scanner (HSTS)

ABSTRACTThe dynamic features of Al2O3 - polytetrafluoroethylene (PTFE) and Al - PTFE reactions in non-isothermal conditions are presented. The Differential Scanning Calorimetry (DSC) and High-Speed Temperature Scanner (HSTS) were used to characterize the Al2O3/Al – PTFE reactions at different heating rates. The study shows that the HSTS instrument can give more information about the reaction mechanism and kinetics than the conventional DSC measurements. In this work we show that high heating rates may reveal exothermic reaction between Al2O3 and PTFE that were previously unidentified. The PTFE can potentially remove the oxide layer from aluminum in the initial period of the reaction and increase the direct contact area between oxygen and aluminum, which increases the reaction velocity and improves the energy release abilities of the system.

Significant Undercooled Liquid Region of Over 200K in Rare Earth Based Metallic Glasses

Using a newly developed temperature modulated differential scanning calorimetry (TMDSC), glass transition has been detected in several RE-Fe-Al (RE = ND, Pr, Sm and Y) metallic glasses, which can not be observed by a conventional DSC. Our results show that the glass transition occurred together with a small fraction crystallization in the as-spun samples, the final main crystallization transition occurred at higher temperature (over 720K) in these rare-earth based alloys. Large undercooled liquid regions up to 200K at a underlying heating rate of 5K/min have been observed in these glasses.

Information on the noncrystalline phase of nascent iPP given by slow calorimetry

Nascent isotactic polypropylene (iPP) has a lower crystallinity and a different X-ray pattern than recrystallized iPP. Heat flows during the melting of nascent highly stereoregular iPP samples are recorded with a Setaram C80 calorimeter over a wide T range (30–280 °C). The rate of heating–cooling is 1–3 K/h, i.e., much lower than with conventional DSC. Melting is performed after annealing at 30 < Tannealing < 140 °C and with or without substrate. The main peak, that found by DSC, is associated with melting of monoclinic crystals and gives an enthalpy ΔHDSC. Two other peaks, usually above and below the main peak, are observed. These are associated with a slower process of disordering a physical network, which was produced in the sample during polymerization. The sum of ΔHDSC and ΔHnetwork equals ΔHtotal. When melting is complete ΔHtotal is equal to ΔH0, the heat of fusion of perfect iPP crystals. This work presents new information on: (i) the noncrystalline phase of nascent iPP and the heat content of a semicrystalline polymer; (ii) the modifications of the melting process due to strain development, brought about by expansion in the material during the temperature ramp when a physical network is present; and (iii) the effect of a substrate on the polymer melting process. Keywords: nascent iPP, slow calorimetry, strain-melting, change of enthalpy, substrates.