Differential Scanning Calorimetry (DSC)

Differential scanning calorimetry is a powerful thermal analytical technique that can be used to analyze thermal properties of a material system. DSC measures the difference in the amount of energy required to heat a sample and a reference at the same rate. By using this technique, we are able to measure various properties including phase transition temperature (whether such a transition is from solid to liquid, amorphous to crystalline, or magnetic to non-magnetic), latent heat of transformation, and specific heat capacity. From these properties, it is possible to perform an in-depth analysis of things like reaction kinetics or melting and solidification behavior.

Typical Experimental Results

DSC measurement of 99.999% Aluminum.

Applications

For more information please read our application notes:
Melting Temperature and Latent Heat of Fusion of Indium, PDF
Specific Heat Capacity of Refractory Material, PDF
Simultaneous Thermal Analysis of the Decomposition of Calcium Oxalate, PDF

Instrument: STA 449 F3 Jupiter Thermal Analyzer

Instrument Key Specifications

Melting Temperature and Latent Heat of Fusion of Indium

Understanding the thermal behavior of a material can be very useful to manufacturers who melt metals and alloys such as in casting parts or soldering electronic components. Knowing the melting temperature and latent heat of fusion can help to prevent overheating the molten metal unnecessarily and reduce energy costs. It can also help to prevent other issues caused by overheating a melt including increased oxidation, melt container corrosion, and mass loss through evaporation. In soldering electronics applications, it can help to eliminate possible damage to critical components due to overheating.

Differential scanning calorimetry (DSC) is an analysis technique that is widely used to analyze the thermal behavior of a material. DSC can be used to determine phase transition temperatures, the enthalpy of such transitions, and reaction kinetics. It is an indispensable tool for determining melting temperature and latent heat of fusion.

Indium metal is commonly used in lead-free solder applications. In reflow soldering, the entire printed circuit board is subjected to temperatures slightly above the solder’s melting temperature. Understanding the thermal behavior of indium-rich solder in such applications can be crucial to fine-tuning the process in order to reduce processing time and cost. Figure 1 presents two overlapping DSC data curves obtained in two test runs for melting indium. The tests were performed on an Ebatco NAT Lab’s Simultaneous TG-DTA/DSC Apparatus STA 449 F3 Jupiter manufactured by Netszch (Germany).

The average melting temperature for the indium sample was measured as 156.8°C. The sample’s latent heat of fusion was measured as 28.52 kJ/kg.

Specific Heat Capacity of Refractory Material

Temperature is a measure of the average kinetic energy of a substance. As a substance absorbs energy, the atoms and molecules become excited. Specific heat, C_p, is a measure of a substance’s ability to absorb heat and is expressed as the amount of energy required to change the temperature of one unit mass of the substance by one degree Kelvin.

For quantum mechanical reasons, as a substance absorbs heat and becomes hotter, more degrees of freedom are available for the constituent molecules. As these degrees of freedom become available, the substance is able to absorb more energy per degree of temperature change.

Specific heat measurements using Differential Scanning Calorimetry (DSC) require three separate test runs to obtain accurate data. The first test run must be performed using two empty crucibles to establish baseline performance of the instrument. The second test run is performed using a specific heat standard, typically high purity sapphire, that has a very well defined heat capacity over the full temperature range of the specific heat measurement. The third test is performed with the sample being measured. The specific heat is then determined via Equations 1 and 2.

Specific heat capacity is an important property to consider for a variety of different applications. While specific heat values for individual elements are well known, they are less so for multicomponent systems such as alloys and composites. Understanding how these materials store heat energy is vital in heat transfer applications.

One such application for C_p measurements is nanostructured materials. These materials tend to show atypical values for specific heat, in some cases as much as 50% higher than that of the coarse-grained material.

Another application is furnace materials. Refractory materials that line a furnace should have low heat capacity so that less energy is drawn away from the furnace and stock material. Due to their chemical stability, high melting temperature and low specific heat, bricks made partly from Aluminum Oxide (Al₂O₃) are frequently used to build the interior wall of high temperature furnaces.

The specific heat of Aluminum Oxide (Al₂O₃) was measured in Ebatco’s NAT Lab using a Netzsch Simultaneous TGA/DSC Apparatus STA 449 F3 Jupiter (Germany). The STA is capable of performing specific heat measurements between room temperature and 1500°C with a stated accuracy of ±5%. The measurement results are presented in Figure 1. The average deviation of the experimental data from the published data is only 0.78%

Reference:
Sarge, Stefan M., Eberhard Gmelin, Günther W.H. Höhne, Heiko K. Cammenga, Wolfgang Hemminger, and Walter Eysel. “The Caloric Calibration of Scanning Calorimeters.” Thermochimica Acta 247.2 (1994): 129-68. ISSN 0040-6031, 10.1016/0040-6031(94)80118-5.

Simultaneous Thermal Analysis of the Decomposition of Calcium Oxalate

Simultaneous thermal analysis (STA) performs thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) simultaneously on a sample. STA allows for precise correlation of changes in mass with changes in energy and vice versa. It provides not only results one can get from separate TGA or DSC analysis, but also better correlation between the two kinds of analyses because they are run under the exactly same conditions.

STA is invaluable in certain applications, such as differentiating between phase transformation and decomposition, or recognizing pyrolysis, oxidation and combustion reactions. The technique can also be used to determine reaction kinetics, physical transitions, residual mass or curing and evaporation rates. STA has applications in characterizing pharmaceutical materials, cements, minerals, resins, etc. Any material that undergoes changes in mass or internal energy when subjected to a controlled heating program can be analyzed using STA.

Calcium Oxalate Monohydrate, CaC₂O₄•H₂O, is a useful industrial compound used to make organic oxalates, and glazes. Understanding Calcium Oxalate’s thermal behavior when applied as part of a glaze is crucial to determining kiln temperature. If the kiln is not hot enough, the calcium oxalate won’t decompose properly. If it is overheated, the glaze’s viscosity will lower to the point that it runs off the surface of the pottery it was applied to. Thermal decomposition data for CaC₂O₄•H₂O was obtained using a Netzsch STA 449 F3 Jupiter Simultaneous TGA-DSC (Germany). Table 1 summarizes the three decomposition reactions that occurred during the test.

The DSC data shows that the first and third reactions are purely endothermic, as would be expected from a simple decomposition reaction. However, the second reaction step shows evidence of two overlapping reactions, one endothermic and the other exothermic. This can be explained by the Boudouard reaction, the equilibrium redox reaction of carbon monoxide into carbon dioxide and carbon. At elevated temperatures that are less than 700°C, carbon monoxide will react to form carbon and carbon dioxide, which is an exothermic reaction.

The measured mass losses during steps 1 to 3 closely match the predicted mass losses, which verify the theoretical predictions of the thermal decomposition for the calcium oxalate monohydrate. It is interesting to note the slight difference in the mass loss between theoretical calculation and actual measurement for decomposition in step 2. This can be explained by the Boudouard reaction depositing carbon residue on the sample, resulting in a mass loss that is significantly lower than expected.

If this experiment had been performed using only DSC or TGA, there would not have been
enough information to analyze and fully understand the reactions occurring.