Therefore, it can be suggested that in the given systems, the combustion KU55933 chemical structure process in the K2TaF7 + (5 + k)NaN3 + kNH4F system starts at around 350 ± 50°C. Figure 3 DSC-TGA curves of K 2 TaF 7 + 5NaN 3 and K 2 TaF 7 + 9NaN 3 + 4NH 4 F systems in argon atmosphere. Figure 4 shows the
temperature-time profiles for the combustion wave of the K2TaF7 + (5 + k)NaN3 + kNH4F mixture over the reaction time (t). As shown in Figure 4, the starting temperature for the combustion process is denoted by T* (350 ± 50°C) and corresponds to the sharp peaks in the DSC curve (Figure 3). One can see that in the beginning of the reaction zone, the temperature increases rapidly from 25°C to 700°C and then to 1,000°C, and then long-tailed post-combustion processes followed. The combustion temperature (T c) showed a tendency to decrease Selleckchem EPZ-6438 with the amount of NH4F used. In the investigated interval of k, the T c drops from 1,170°C (k = 0) to 850°C (k = 4). The maximum combustion velocity (U c = 0.5 cm/s) occurred at the nearly stoichiometric mixture (k = 0), but combustion velocity decreased significantly as the K2TaF7 + 5NaN3 mixture became ‘diluted’ with NH4F. Figure 4 Temperature-time profiles in K 2 TaF 7 + (5 + k )NaN 3 + k NH 4 F system. Characteristics of combusted samples and powders Figure 5 shows photographs of the as-combusted (Figure 5a,b) and water-purified (Figure 5c) samples. After combustion,
the sample of the K2TaF7 + 5NaN3 composition (k = 0) retained its original shape and size (Figure 5a). However, the samples produced using 2.0 to 4.0 mol of NH4F had melted after the combustion process, forming a brown-colored, brittle, and shapeless molten product. For instance, several fragments of the sample www.selleckchem.com/products/crenolanib-cp-868596.html prepared with k = 4 are shown in Figure 5b.
Many large pores, due to the release of N2 and H2 gases during the combustion process, can be seen in the solid molten mass. After dissolving alkali fluorides (NaF and KF) into warm distillated water, TaN fine powders were obtained. A photograph of finally purified TaN samples prepared from the K2TaF7 + 5NaN3 Protein Tyrosine Kinase inhibitor +4NH4F mixture is shown in Figure 5c. Its color is uniformly black, and specific gravity lies between 0.7 and 0.9 g/cm3. Figure 5 Photographs of as-combusted (a, b) and water-purified (c) samples. The XRD patterns for the water-purified powders that had been prepared with different amounts of NH4F are shown in Figure 6. Diffraction peaks of the sample prepared at k = 0 (without NH4F) indicate three nitride phases: hexagonal ε-TaN, TaN0.8, and Ta2N (Figure 6a). The cubic δ-TaN phase was detected in large amounts, along with the ε-TaN and TaN0.8 phases for samples with k = 2 (Figure 6b). By applying 4 mol of NH4F to the reaction of K2TaF7 and NaN3, the only crystalline product produced is cubic TaN. The diffraction peaks marked in Figure 6c correspond to face-centered cubic TaN (JCPDS 32–1283).