# A Study of the Thermodynamic Properties of Nd-C and Ce-C TRISO Fission Product Binary Systems
## 2 Materials and Methods
### DSC Measurements  
DSC measurements of the carbide samples were performed in a similar manner as the calibration sequences. Samples were removed from the argon-filled glovebox using an anti-static weighing boat, and their mass measured using a Sartorius Entris 64I-1 SUS mass balance (sourced from Sartorius, Gottingen, Germany) with an accuracy of \(\pm 0.1\) mg before being placed inside a boron nitride crucible and positioned into the STA furnace. The total exposure of the sample in air was less than 10 min to minimize oxidation. The combined intermediate samples produced at OTU were tested using a similar process with the addition of a 90 min isothermal hold at 1100 \({}^{\circ}\)C at the beginning of the DSC test. Lower temperatures and shorter isothermal holds were tested but these proved ineffective at completely melting and mixing the samples as confirmed through poor DSC responses and a lack of melting observed via visual inspection of the measurement crucible. A summary of the DSC test parameters is provided below:  
Measurement parameters:  
1. Test Instrument: Netzsch STA 449 F1 Jupiter Simultaneous Thermal Analyzer (sourced from Netzsch, Bavaria, Germany);
2. Inert Gas Passover: 99.999% Ar gas;
3. Gas Flow Rate: 20 mL/min;
4. Oxygen Trap System: Zirconium oxygen-getter ring (sourced from Netzsch, Bavaria, Germany);
5. Sample Carrier Support Tube: Alumina (sourced from Netzsch product no. HTP40000 A97.010-00, Bavaria, Germany);  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Substance** & **Ref. Temp.** [\({}^{\circ}\)C] [50] & **Measured Temp.** & **Weighting Factor** & **Corrected Temp.** \\  & & [\({}^{\circ}\)C] & & [\({}^{\circ}\)C] \\ \hline In & 156.6 & 155.1 & 10 & 156.7 \\ Zn & 419.5 & 419.2 & 10 & 419.5 \\ Al & 660.3 & 660.0 & 10 & 659.8 \\ Ag & 961.8 & 963.5 & 10 & 963.2 \\ Au & 1064.2 & 1063.4 & 10 & 1063.3 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Measured and corrected calibration temperatures.  
Figure 13: Regression analysis of experimentally measured sensitivity calibration values.  
Sample Carrier: Alumina with a Pt/Rh head and Type S TGA-DSC Thermocouple (sourced from Netzsch product No. HTP40000A54.000-00, Bavaria, Germany);
* 7 Measurement Crucible: Boron Nitride (sourced from Netzsch product no. NGB808836, Bavaria, Germany);
* 8 Reference Crucible: Boron Nitride (sourced from Netzsch product no. NGB808836, Bavaria, Germany).
* 9 Measurement procedure:
* 1 STA Crucibles: Insert the measurement crucible with the sample and the empty reference crucible onto the STA sample holder;
* 2 STA Furnace: Perform three STA SiC furnace volume evacuations using a vacuum pump, and three furnace volume re-fills with 99.999% Ar gas;
* 3 Temperature Rate: Set the temperature rate to 5\({}^{\circ}\)C/min;
* 4 Isothermal Hold: For the intermediary compounds produced at OTU, heat the furnace to 1100\({}^{\circ}\)C, then hold for 90 min--for the UTSA samples, omit this step;
* 5 Return to Room Temperature: For the intermediary compounds produced at OTU, cool the furnace to 25\({}^{\circ}\)C--for the UTSA samples, omit this step;
* 6 Temperature Heating: Heat the furnace to 100\({}^{\circ}\)C above the highest predicted phase transition temperature;
* 7 Temperature Cooling: Cool the furnace to 100\({}^{\circ}\)C below the lowest predicted phase transition temperature;
* 8 Temperature Cycling: Repeat Step 5 and 6 for a total of six temperature transition cycles, i.e., three heating and three cooling.