Thermodynamic investigations of Cr3C2 and reassessment of the Cr-C system

• The Gibbs energies of formation for Cr3C2, Δ fG°Cr3C2, have been obtained from electromotive force (EMF) measurements, in the temperature range 950 to 1150 K, using the following galvanic cells with CaF2 single crystals as the electrolyte: Cr, CrF2 CaF2 CrF2, Cr 3C2, C (950 to 1150 K) Extreme precautions were taken during the experimental measurements to avoid errors. The reliability and reproducibility of the values were confirmed by careful repetition of several of the experiments. The following equation has been obtained by a linear analysis of the EMF results as a function of temperature: ΔfG°Cr3C2(± 1600) = - 58,857 - 22.344T (J·mo1-1) (950 to 1150 K) The generated values are compared with those reported in the literature. The values of the enthalpy of formation were evaluated by using a third-law analysis, and an average value of ΔfH° 298 = -71.7 kJ/mol was obtained. The ground-state energy of the hypothetic end-member compound CrC3 in the bcc structure at 0 K was calculated by using the ab initio method. The experimental results obtained, as well as the results from the ab initio calculations, were employed in a reassessment of the Cr-C system using the CALPHAD approach. A new set of parameters for the bcc phase was evaluated using first-principles calculations.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Calcium compounds

Chromium alloys

Electric potential

Electrolytes

Enthalpy

Gibbs free energy

Single crystals

Temperature

Thermodynamic properties

X ray diffraction analysis

Materials science

Teknisk materialvetenskap

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