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The Enthappy of Formation of Cubic Boron Nitride

Tomaszkiewicz I.

Polish Journal of Chemistry

2002

Vol. 76 / nr 8

1163-1173

The massic energies of combustion in fluorine of two specimens of cubic boron nitride have been measured in a bomb calorimeter, the standard molar enthalpy of formation delta f 0 m H(c-BN, cr, 298.15 K) = -254.6š1.5 and the enthalpy of polymorphic transition delta trs m 0 H (298.15 K) = -3.5š1.5 of the process: h-BN (cr) -- c-BN (cr) have been determined. Those quantities are compared with the values determined previously.

The Enthalpy of Formation of Hexagonal Boron Nitride

Tomaszkiewicz I.

Polish Journal of Chemistry

2002

Vol. 76 / nr 6

891-899

The energies of combustion in fluorine of three specimens of hexagonal boron nitride with different degree of ideal crystalline structure have been measured in a twocompartment calorimetric bomb at 298.15 K according to reaction: BN(cr) + 3/2F2(g) = BF3(g) + 1/2N2(g), and new standard molar enthalpies of formation f m H0 have been calculated and used to rank the samples in order of stability: f m H0 = -(245.8š1.1) kJ/mol for turbostratic sample, that deviates most from the crystalline structure; f m H0 = -(248.5š0.9) kJ/mol for the sample with an interlayer spacing that is only about 0.5% larger than the ideal crystalline h-BN; and f m H0 = -(250.8š1.2) kJ/mol for crystalline h-BN.