Boron phase diagram

Tep] Teppo, O., Taskinen, R, Thermodynamie Assessment of Nickel-Boron Phase Diagram (in English), Mater. Sci. Technol, 9(3), 205-212 (1993) (Assessment, Phase Diagram, Thermodyn., 41)... 

Critical assessment of phase-diagram data employing the thermodynamics of the phase equilibria in the form of phase-diagram modeling provides consistent thermochemical data (including also the liquid solution) for binary metal-boron systems such as V—B Cr—B, Mn—B, Fe —B, Co—B, Ni—Mo—B and Nb—B, W—B, A1 — B Despite these efforts, reinvestigation of binary systems is... 

Rogl, P. and G. Eftenberg Phase Diagrams of Ternary Metal-Boron-Carbon Systems, ASM International, Materials Park, OH. 1998. 

Boron carbide is rhombohedral (a = 5.163 A a = 65.59°). The stoichiometric composition of boron carbide is Bi3C2(B6.5C), so that B4C is a carbon-saturated solid solution. The phase diagram for the B-C system is shown in Figure 1. The density as a function of stoichiometry is shown in Figure 2. 

E. Rudy, Ternary phase equilibria in transition metal-boron-carbon-silicon systems. Part V. Compendium of phase diagram data. Tech. Rep. AFML-TR—Air Force Mater. Lab. (US.) AFML-TR-65-2 (1969). 

The two earliest reports of the COClj-BFj system are apparently contradictory the earlier [738a] claims that phosgene and boron(III) fluoride interact to form compounds (but does not identify these in any way), the later [1329] suggests that phosgene and boron(III) fluoride do not form a complex, even at temperatures as low as -120 C. However, a more detailed investigation [1329] resolved these anomalies. The phase diagram for the COClj-BFj system is illustrated in Fig. 9.1, and shows clear evidence for complex formation at compositions BF3.COCIJ (m.pt. -134.3 C) and BF3.2COCIJ (m.pt. -137.0 C) [1329]. 

Phosgene and boron(III) chloride are miscible in all proportions [1329], as predicted earlier [738a] and the phase diagram for the COClj-BClj system (Fig. 9.3) reveals a eutectic point at -142.3 C (74.4 mole % COCIj) and no evidence for any complex formation. Moreover, the vapour pressure - composition isotherm (0 C) for this system (Fig. 9.4) shows a positive deviation from Raoult s law (although Henry s law appears to be well obeyed [649]), indicating the presence of unfavourable interactions between phosgene and boron(III) chloride [376]. Thus, the purification of boron(HI) chloride from traces of phosgene will not be complicated by the formation of a thermodynamically stable complex. 

The phase diagram of the system NaF-B203 up to 65 mole % B2O3 was studied by Bergman and Nagornyi (1943) and the cryoscopy in the system NaF-B203 by Makyta (1993). It was found that in this system, sodium metaborate, sodium tetraborate, and gaseous boron trifluoride are created in the melts. 

Figure 47. Phase diagram of N2 on boron nitride based on adsorption isotherms coverage is repotted in units of the complete Vs mono-layer obtained from the top of the fluid to commensurate solid isotherm substep at low temperatures less than 51 K. Commensurate solid phase (C), fluid phase (F), reentrant fluid phase (RF). The solid lines correspond to phase boundaries based on measured features, the dotted line is an expected phase boundary, and the triangle marks the tricritical point. Second-layer growth instead of a transition to an incommensurate solid phase is expected beyond the reentrant fluid phase in the temperature range studied. (Adapted from Fig. 4 of Ref. 1.)...

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