# A Study of the Thermodynamic Properties of Nd-C and Ce-C TRISO Fission Product Binary Systems
## 3 Results
### DSC Measurements of the Nd-C System  
3.1.1. Nd1: 10 mol%C, 90 mol%Nd  
DSC measurements of Nd1 were performed under Campaigns #1, #2, and #3 as described in Table 6, and reported data are derived from tests Nd1-2-1, Nd1-2-2, and Nd1-3-1. Nd1-2-1 used 31.2 mg of sample and did not utilize boron nitride powder lining as DSC tests of the stoichiometric NdC\({}_{2}\) in the literature indicated that the sample would not adhere to the crucible [23; 52]. Post-test examination determined that the sample adhered to the crucible, but the DSC signal response was clear and no apparent chemical reaction occurred as confirmed visually and through thermogravimetric response of the STA. Nd1-2-2 increased the sample size to 147.4 mg to improve the strength of the DSC response, and also omitted BN powder. DSC responses were excellent; however, the sample adhered to the crucible once again. As mentioned previously, Nd1-2-1 and Nd1-2-2 employed a two hour isothermal hold of 500 \({}^{\circ}\)C with 0.25% H\({}_{2}\)/Ar gas, during the first temperature ramping cycle in an attempt to mitigate any potential oxidation of the sample. Figure 16 shows the DSC response of the third heating cycle of test Nd1-2-2, which displayed representative DSC peaks for this molar concentration.  
Nd1-3-1 employed 0.8 mg of boron nitride powder using a sample size of 40.1 mg, with the sample adhering once more but providing observable phase transitions comparable to Nd1-2-1 and Nd1-2-2. The test did not use the H\({}_{2}\) isothermal hold, and results confirmed that the isothermal hold did not contribute to improved DSC responses. Three phase changes were observed in all tests, but displaying relatively higher phase transition temperatures than predicted by [PERSON] et al. [22]. In all tests of Nd1 through all campaigns, the sample completely liquefied. Weighting was favored on the data collected from test Nd1-3-1 as the solidus temperature better aligned with the Nd2 and Nd3 solidus temperatures.  
Figure 15: Optical images of Nd4, 40 mol%C and 60 mol%Nd, and Ce2, 20 mol%C and 80 mol%Ce, pre- and post-DSC: (**a**) Nd4 pre-DSC; (**b**) Nd4 post-DSC; (**c**) Ce2 pre-DSC; (**d**) Ce2 post-DSC.  
3.1.2. Nd2: 20 mol%C, 80 mol%Nd  
Two DSC measurements were performed on two samples of Nd2 to identify the eutectic transition temperature of the system under Campaigns #2 and #4 and tests Nd2-2-1 and Nd2-4-1, respectively. Nd2-2-1 employed a 125.9 mg sample with 12.7 mg of boron nitride powder, and the second used a 22.8 mg sample without boron nitride powder. The sample used in the first test did not adhere to the crucible, but the DSC response was severely suppressed with a single, marginal inflection point present in both heating cycles. Nd2-4-1 displayed a single prominent DSC peak response indicating a phase transition in both the second and third heating cycles that agreed well with each other and was reported. The sample completely liquefied in the second test. Weighting was favored on test Nd2-4-1 due to the improved test conditions and higher DSC response, as well as better alignment with neighboring composition solidus temperatures. Noise was present in the DSC response that is speculated to be caused by the relatively small sample size, which would result in the DSC measurement thermocouple being more sensitive to temperature fluctuations.