Crystallization levitated liquids

Bererzin et al (2) have measured the enthalpy of crystal and liquid molybdenum by levitation calorimetry in the range 1962-2869 K and 2890-2925 K, respectively. They reported Aj gH 8.741 0.314 kcal mol" at an assumed melting temperature of 2890... 

Figure 19. Left Pyrometrically determined cooling curves for levitated AYx liquids showing crystallization temperatures where Debye-Scherrer features first appeared in the WAXS pattern (dashed arrows). For AY15 and AY20 the crystallization exotherm is anticipated by a prepeak (solid arrow) that is associated with the LLPT identified by the polyamorphic rotor action. Right Curves for AY15 and AY20 with the cooling curves subtracted differentiating the LLTP exotherm from exotherm due to crystallization.

The crystal structure of the compound LaPd2Ge was found to be of the YPd2Si type (a = 0.7711, 6 = 0.6972, c = 0.5828 X-ray powder diffraction) by Jorda et al. (1983). The sample was obtained by induction heating of pressed powder compacts in a levitation coil under an argon atmosphere pressure of 4 atm. After the rapid reaction in the liquid state the molten sample was dropped into a boron nitride crucible. Then alloy was annealed in evacuated quartz tube for 10 days at 1173K. Starting materials were Pd 99.99 mass%, Ge, specpure quality. La 99.9mass%. 

Apart from the described particle structures so far, it was noticeable that droplets at 5 % and higher relative humidities did not ciystaUize during the drying process. They showed a transparent appearance although the melting point of mannitol (158-167.9 °C [43, 44]) was not reached. The inner temperature of the droplet was constantly at gas temperature and no further phase change or solvent evaporation was observed so that these droplets had to ccaitain pure maimitol. As soon as the liquid mannitol droplets were removed from the reaction chamber of the levitator, they crystallized. Therefore, it was assumed that the particles formed a metastable, supersaturated mannitol solution [45]. Under certain circumstances, amorphous mannitol with a Tg = 13 °C has already been reported by Kim et al. [46]. 

---