M.P. Antony

Thermal expansion characteristics of a titanium modified austenitic stainless steel: measurement by high-temperature X-ray diffraction and modelling using Grüneisen formalism

Abstract The thermal expansion of a titanium modified, swelling resistant austenitic stainless steel designated as D9 is studied by measuring the lattice parameter as a function of temperature in the range 300–1300 K by high-temperature X-ray diffraction technique. The thermal expansion data thus obtained is in reasonable agreement with the typical thermal expansion values reported for similar nuclear grade austenitic stainless steels. However, at temperatures exceeding 900 K, the measured thermal expansivity exhibits a pronounced non-linear increase due partly to the precipitation of complex carbide and intermetallic phases. The high-temperature thermal expansion data obtained in the present study are augmented by modelling the low-temperature thermal expansion behaviour by Gruneisen formalism.

Studies on the kinetics of the carbothermic reduction of chromium oxide using the evolved gas analysis technique

The kinetics of formation of Cr 3 C 2 by the carbothermic reduction of Cr 2 O 3 with graphite was studied in the temperature range 1461-1739 K. The experiments were carried out in a high vacuum chamber with the mechanically mixed reactants in pellet form, compacted at different pressures. The progress of the reaction was followed by monitoring the CO gas evolved by means of a quadrupole mass spectrometer. From the parabolic nature of the rate equation and the dependence of the activation energy of the reaction on the compaction pressure of the pellets, it was concluded that the diffusion of CO gas through the product layer was the rate-controlling step.

Enthalpies of formation of UNi5, UNi2 and UFe2 by solution calorimetry

Abstract The enthalpies of formation of the intermetallic compounds UNi5, UNi2 and UFe2 at room temperature were determined by high temperature solution calorimetry in which liquid aluminium was used as the solvent. The “thermal effects of dissolution” of Ni, Fe, UNi5, UNi2 and UFe2 in liquid aluminium were measured in separate experiments by dropping the samples, held at ambient temperature, into liquid aluminium maintained at 994 K in a high temperature differential calorimeter. The thermal effects of dissolution of the samples in liquid aluminium at infinite dilution were derived from these measurements, and based on these data, the enthalpies of formation of UNi5, UNi2 and UFe2 at room temperature were computed as −(39.54 ± 8.6), −(37.89 ± 4.4) and −(38.73 ± 5.4) kJ (g-atom)−1, respectively. The partial enthalpies of solution at infinite dilution, ( Δ H ∞ ) for Ni and Fe in liquid aluminium were also derived from the measured data as −(147.26 ± 1) and −(114.71 ± 1.2) kJ mol−1, respectively.

A study on the thermal expansion characteristics of Inconel-82® filler wire by high temperature X-ray diffraction

Abstract The lattice parameter ( a ) change with respect to temperature ( T ) has been measured by high temperature X-ray diffraction (HT-XRD) technique for Inconel-82® 1 filler wire used in the TIG welding of a dissimilar joint involving Inconel-600® and commercially pure iron. By taking proper precautions to minimise the temperature gradient across the sample thickness, and by suitably calibrating the shift in 2 θ produced as a result of sample buckling at high temperatures, we could obtain fairly reliable estimates of lattice parameter in the temperature range 300–1200 K. The lattice parameter and the coefficient of mean linear thermal expansion at 300 K, have been found to be 3.546(2)×10 −10 m and 11.03×10 −6 K −1 , respectively.

Thermodynamic studies of uranium-gadolinium-carbon system through the carbothermic reduction of the oxides

The formation of solid solutions of (U1−yGdy)C2 (where 0.2 </ y </ 0.8) in the high carbon region, has been studied in the temperature range 1063–1673 K. The solid solutions were prepared by blending the stoichiometric amounts of oxides with graphite and heating the mixture in the form of a pellet to the reaction temperature in a high vacuum chamber. The effusion of CO from the pellet was monitored by means of a quadrupole mass spectrometer. The effusion pressures of CO in the vacuum chamber were correlated to the equilibrium pressure of the system, according to a new method developed in our laboratory [R. Vidhya, M.P. Antony, C.K. Mathews, J. Phys. Chem. 99 (1995) 16468]. The reported solubility [T.C. Wallace, N.H. Krikorian, P.L. Stone, J. Electrochem. Soc. 111(12) (1964) 1404] of ‘GdC{IN2}’ in ‘UC2’ was verified by XRD. The Gibbs energies of formation of the different solid solutions have been calculated.

Erratum to: ‘Enthalpy and Gibbs energy of formation of cerium dicarbide’ [J. Nucl. Mater. 317 (2003) 102–108]

The Publisher regrets that in the original article several minus signs were not printed. Below are the correct nota- tions: