Phase Diagrams of the MeNQ/HN and HN/NQ Binary Systems

An equation for a binary phase diagram with two eutectic points was deduced from the Van’t Hoff equation. The melting points of hydrazinium nitrate/ nitroguanidine (HN/NQ) samples with different ratios, ranging from 0 to 1 mole fraction, were explored by differential scanning calorimetry (DSC). The results revealed the presence of two eutectic points in the phase diagram of the HN/NQ binary system. The dependence of temperature on the composition (T-X phase diagram) of HN/NQ was depicted based on the equation described by the DSC data. The phase diagram of MeNQ/HN, with only one eutectic point was constructed by substituting experimental data of the compositions and their corresponding temperatures into the Van’t Hoff equation. The phase diagram with two or more eutectic points indicated the formation of new stable compounds with appropriate ratios of the two components; no new substance appeared in the system with only one eutectic point. Thus, the HN/NQ binary system showed the presence of a new substance, which is probably the HN/NQ co-crystal. No new substance was detected in the MeNQ/HN binary system. The results of the X-ray diffraction patterns agree with the findings from the phase diagrams.