Additionally, the melting behavior

Additionally, the melting behavior of the 51:49 NaOH:KOH mixture was investigated using the sinterometer. It is known from the literature absorbed water can lower the melting point of hydroxides [24]. However, the high pressures (* 100 s of MPa) applied during HAD likely favor the solid phase of the hydroxides, given that NaOH and KOH have higher molar volumes in the liquid phase [30, 31]. Figure 4a shows a plot of compaction vs. time of NaK under a pressure of 530 MPa. The compaction event beginning at * 13 min is attributed to melting of the NaK mixture. This is concluded based on the large amount of compaction (* 0.8 mm) and observations of material being extruded out of the top and bottom of the die at this point in the experiment. It should be noted that for this experiment the die ramp rate was slowed to 10 C/min to more easily identify the melting onset temperature. Figure 4b plots compaction rate, as determined by taking the differential with respect to time of the trace in (a), after smoothing (for clarity). Examining the differential sintegram in Fig. 4(b), the NaK mixture melted between 148 and 158 C, which is slightly lower than the 170 C eutectic melting