# A Study of the Thermodynamic Properties of Nd-C and Ce-C TRISO Fission Product Binary Systems
## 2 Materials and Methods
### Experimental Procedures  
As a result of the chemical interactions observed between the alumina crucibles and the carbide samples, variations in testing were required until a standard, repeatable test sequence was established with the available lab equipment. A summary of the tests performed is provided in Table 6. Note that samples labeled Nd1.5, Nd2.5, Nd3.5, and Ce1.5 were produced at OTU, and all other samples were produced at UTSA. The Test ID in this table is assigned per the following system: \"(Material)-(Campaign #)-(Test #)\". Campaign #1 commenced with alumina DSC crucibles for calibrations and testing. Nd1 was the first carbide sample tested, with tests Nd1-1-1 and Nd1-1-2 showing no discernible DSC phase transition. It was suspected that the low masses of 21.1 mg and 20.0 mg contributed to this observation. Therefore, test Nd1-1-3 used 125.3 mg of sample Nd1 in an attempt to improve the DSC response. The sample appeared to chemically react with the alumina crucible as shown in Figure 6, with the resultant DSC response displaying erratic values that did not follow the repeatability of typical DSC sequences. Carbide testing in Campaign #2 commenced with Nd1-2-1 and boron nitride crucibles, where a two-hour isothermal hold of 500\({}^{\circ}\)C with 0.25% H\({}_{2}\) gas, balance Ar, was added. The lack of DSC response in tests Nd1-1-1 and Nd1-1-2 was postulated to be a result of sample oxidation. Therefore, a small amount of hydrogen gas was passed over the sample to react with any surface oxygen and removed before commencing the three heating and cooling cycles for phase transition measurements. This is based on prior experience with oxidized samples at OTU that was able to successfully mitigate specimen oxidation through this marginal passover of hydrogen gas. No mass change was observed during tests Nd1-2-1, Nd1-2-2, and Nd2-2-1, suggesting that the hydrogen did not remove significant amounts of oxygen or material. It is also possible that there was insufficient hydrogen added to the system to significantly reduce the samples. DSC results for Nd1-2-1 and Nd1-2-2 were excellent compared to those measured with alumina crucibles, with well-defined phase transitions. However, the samples adhered to the crucible after testing. This appeared to be a different phenomenon compared to the alumina-Nd1 reaction and BN-Ni reaction as no mass change occurred, the crucible remained visually unchanged, and the DSC response provided expected results. Therefore, boron nitride powder was added to the crucible for test Nd2-2-1 in an attempt to prevent sample adhesion. Initial results appeared to prevent adhesion between the sample and crucible, but the DSC response was negligible above background noise and it was later discovered that the powder could not be removed from the crucible. Campaign #3 commenced using boron nitride crucibles, with the intent of determining a configuration that would prevent sample and crucible adhesion. The 0.25% H\({}_{2}\) gas isothermal hold was also omitted based on the suspected negligible improvements. Tests Nd1-3-1 and Nd1-3-2 attempted to adjust the boron nitride powder to prevent adhesion while permitting strong DSC responses. Test Nd1-3-1 used 0.8 mg of BN powder, which provided an excellent DSC response but did not prevent sample adhesion. The results were also comparable to Nd1-2-1, confirming that the hydrogen gas did not improve the DSC responses and that the minimal BN powder could produce a strong DSC response. Test Nd1-3-2 used 14.5 mg of BN powder, dampening the DSC response so no discernible phase transitions were observed. Unexpectedly, the sample also adhered to the powder and crucible. The campaign was then paused and restarted due to temporary equipment downtime and other factors. Finally, Campaign #4 proceeded with just boron nitride crucibles, no hydrogen gas passover, and no boron nitride powder lining, resulting in the use of one BN crucible for one carbide test measurement as sample adhesion could not be reliably prevented without the loss of DSC responses.