Boron, thermodynamic data

When one considers the potential high-energy release on rupture of a carborane unit, together with the thermodynamic stability of combustion products, it is hardly surprising that there is a body of literature that reports on the use of carbo-ranes within propellant compositions. Their use in energetic applications is to be expected when the enthalpy of formation (AH/) data for the products of combustion for boron are compared to those of carbon. Thermodynamic data for the enthalpy of formation of o-carborane and of typical boron and carbon combustion products is shown in Table 4. Measurements of the standard enthalpy of combustion32 for crystalline samples of ortho-carborane show that complete combustion is a highly exothermic reaction, AH = — 8994 KJmol. ... 

The computerized aqueous chemical model of Truesdell and Jones (, 3), WATEQ, has been greatly revised and expanded to include consideration of ion association and solubility equilibria for several trace metals, Ag, As, Cd, Cu, Mn, Ni, Pb and Zn, solubility equilibria for various metastable and(or) sparingly soluble equilibrium solids, calculation of propagated standard deviation, calculation of redox potential from various couples, polysulfides, and a mass balance section for sulfide solutes. Revisions include expansion and revision of the redox, sulfate, iron, boron, and fluoride solute sections, changes in the possible operations with Fe (II, III, and II + HI), and updating the model s thermodynamic data base using critically evaluated values (81, 50, 58) and new compilations (51, 26 R. M. Siebert and... 

Thermodynamic data for the negative ions of boron and aluminium fluoride, e.g. MFJ and MF4, have been evaluated from effusion mass spectrometric measurements over the temperature range 1100—1900 K.260 Electron affinities for BF2 and A1F2 are 50.7 3 and 53.1 3kcal mol1, respectively. 

Thermodynamic data for synthetic reactions are available h (I) Reduction of Boron Anhydride (or Acid) with Carbon, The overall reaction is written ... 

Different types of thermodynamic data were measured for the boron carbide phase. An overview is given in Table 12 [91, 154-166]. 

Solozhenko (1988) [176] concluded that kinetic factors influenced the transformation significantly and that the true equilibrium line can only be determined by a thermodynamic approach. From data on heat capacities [177-189], relative enthalpies (heat contents) [190-199], enthalpies of formation data [177, 201-207], equations of state and thermal expansion data for all BN modifications, Solozhenko [176] derived a calculated new phase diagram which significantly differed from the Corrigan and Bimdy (1975) [174] version. An overview of somces of thermodynamic data is given in Table 15. A review of calorimetric studies was given by Gavrichev et al. (1994) [212]. Vaporization studies of boron nitride were made by [208-211]. 

Some of the experimental observations are presented in Fig. 12. The results were independent of the nature of the metal-containing additive boron was added as (CH3)3B03, BF3, or H3BO3, molybdenum as Mo(CO)6 or MoFg, and tungsten as W(CO)6 or WF. The results are summarized in Table VI, giving comparable reactions for HCl for comparison. The principal causes of the reported error bounds are uncertainties in the thermodynamic data of the neutral species. 

TABLE VI. Thermodynamic Data Obtained in Flames for the Formation of Negative Ions and Compounds of Boron, Molybdenum, and Tungsten "... 

A. Bondar, 2006. Boron-Chromium-Nickel, in G. Effenberg, ve S. Ilyenko (Eds.), Ternary Alloy System Phase Diagrams, Crystallographic and Thermodynamic Data VolllDl, 320-343. 

Boron. The activation parameters have been determined for the equilibrium between [Pr2B(cycloheptatrienyl)] and [7- vc -Pr2B-norcaradiene]. NMR spectroscopy has been used to determine exchange rates of B(C6F5)3 adducts of PhC(0)X. B NMR spectroscopy has been used to examine the binding of acetone to [Bu CH=C B(C6F5)2 2] and the thermodynamic data determined. B NMR spectroscopy has been used to study the formation of borate esters of ascorbic acid and isoascorbic acid. NMR spectroscopy has been used to... 

Boron Monoxide and Dioxide. High temperature vapor phases of BO, B2O3, and BO2 have been the subject of a number of spectroscopic and mass spectrometric studies aimed at developiag theories of bonding, electronic stmctures, and thermochemical data (1,34). Values for the principal thermodynamic functions have been calculated and compiled for these gases (35). 

Boron tnhahdes, BX, are trigonal planar molecules which are sp hybridized. The X—B—X angles are 120°. Important physical and thermochemical data are presented in Table 1 (8—14). Additional thermodynamic and spectroscopic data may be found in the hterature (1 5). 

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... 

The discovery of what appears to be a thermodynamic threshold governing the intercalation of graphite by fluoro anions, MF,, has required the evaluation of the thermodynamic stability of a number of such species. Since germanium tetrafluoride and fluorine are intercalated, in combination, by graphite to form both GeFj" and GeFs ", the first and second fluoride ion affinities of that molecule are each of interest. Evaluation of the fluoride ion affinity of boron trifluoride by Altshuller yielded a value of-71 kcal moF. This has been accepted by several authors as the basis for other fluoride ion affinities and electron affinities. Sharpe, however, has preferred a value of -91 kcal moF, based upon the data of Bills and Cotton. Although this latter value is in harmony with other fluoride ion affinities and electron affinities, its confirmation was clearly desirable to provide a firm basis for correction of affinities based upon the lower value. This paper describes the studies that have provided these fluoride ion affinities. 

Reassessment of the Si-B system was based primarily on the model parameters given by Fries and Lukas [25], Modifications have been made on the thermodynamic properties of the liquid and solid diamond phases Experimental liquidus data reported by Brosset and Magunsson [26], Armas et al. [27], and Male and Salanoubat [28], solid solubility data reported by Trum-bore [18], Hesse [29], Samsonov and Sleptsov [30], and Taishi et al. [52], as well as the boron activities in liquid phase measured by Zaitsev et al. [32], Yoshikawa and Morita [33], Inoue et al. [7], and Noguchi et al. [31] were all used to determine the model parameters. Figure 13.4 shows the new assessed phase equilibria in the Si-rich Si-B system. 

Thus, the data in Tables 2-4 can be used to calculate, with reasonable (or better) accuracy over a wide range of temperatures, thermodynamic properties of numerous reactions implicated in the combustion of boron- and aluminum-containing propellant formulations. The kinetics can be addressed as well, as was shown in a number of instances. The determination of transition states and activation barriers can be rather time-consuming. However computational methodology continues to improve (e.g. a new version of CBS-QB3... 

Anovitz LM, Hemingway BS (1996) Thermodynamics of boron minerals Summary of stractuial, volumetric and thermochemical data. Rev Mineral 33 181-261... 

A thermodynamic optimization of the system was performed by Domer (1982) [167]. This dataset was later refined by Lim and Lukas (1996) [36]. Due to additional crystallographic information concerning the extended homogeneity range of the boron carbide phase [152, 168] a further assessment was necessary [33, 34,169]. Data for the calculated invariant reactions are given in Table 13. Boron carbide of composition 16.4 at.% C melts congruently at 2731 K. 

Thermodynamic properties of superhard materials produced from the dense modifications of boron nitride, especially of p-BN [7 to 9], have also been studied. The data for Cpfor Kiborit correspond closely to those of p-BN single crystals as given in Table 4/2. Also the Debye temperature of Kiborit [8] (1680 70 K) corresponds to the value for p-BN [6] see [9] for data up to 1400 K. 

Ab initio DFT calculations for all isomers of 21 (dimethylboryl derivatives) and the transition states for their interconversions have been used to clarify the reasons of the relative stabihty of 21b-exo and 2lb-endo. In the former compound the empty 2p-AO of the boron atom is ideally oriented for overlapping with the Walsh orbital of the cyclopropane ring. On the other hand, in 2lh-endo this interaction is elfectively switched off due to the perpendicular orientation of these orbitals emerging when the steric interactions of the alkyl groups and the cyclohexadiene ring are minimized. The thermodynamic parameters for the equilibrium between 21a and 21b were determined by NMR data from the linear dependence of In K versus /T AH =10.1 0.5 kJ mol L AS= -23 1 J mol K . These values are reasonably reproduced in the calculations (AH = 8.4 kJ mol AS = —15.5 J mol K ). 

Mutelet F., Jaubert J.N., Rogalski M., Boukherissa M. Dicko A. (2006). Thermodynamic Properties of Mixtures Containing Ionic Liquids Activity Coefficients at Infinite Dilution of Organic Compounds in 1-Propyl Boronic Acid-3-Alkylimidazolium Bromide and l-Propenyl-3-alkylimidazolium Bromide Using Inverse Gas Chromatography, /, Chem. Eng. Data, vol.51, n°4, pp.1274-1279, (April 2006), ISSN 0021-9568... 

---