High-temperature Differential Calorimeter Research Articles

High-temperature calorimetric measurements on RE2TeO6 (RE = Gd, Er)

The ternary compounds of Gd2TeO6 (s) and Er2TeO6 (s) were prepared by solid-state route and characterized by XRD, ICP-AES and ICP-MS techniques. Enthalpy measurements were taken on these compounds by inverse drop calorimetric method by using a high-temperature differential calorimeter over the temperature region 669–1272 K. The measured enthalpy increment values of these compounds were fitted to four term nonlinear polynomial functions in temperature using least-squares method. With the fitted equations, other thermodynamic function such as heat capacity, entropy and free energy functions have been computed in the temperature range 298–1300 K. The derived free energy functions of RE2TeO6 (RE = Gd, Er), from enthalpy increments measurements were combined with the standard Gibbs energies of formation of RE2TeO6 (RE = Gd, Er), derived from vapor pressure measurement, to obtain $$\Delta _{\text{f}} H_{298}^{\text{o}}$$ of Gd2TeO6 (s) and Er2TeO6 (s).

Enthalpy measurements and thermodynamic properties of M2TeO6(s) (M = Eu,Dy)

Heat content or enthalpy measurements were conducted on Eu2TeO6(s) and Dy2TeO6(s) by employing the method of inverse drop calorimetry using a high temperature differential calorimeter between about 670 and 1270 K. The measured enthalpy increments with temperature are given as: HT0-H2980/J mol−1 ‹Eu2TeO6› = 229.494 T + 1.199 × 10−2T2 + 18.197 × 105T−1 − 75592(670 ≤ T (K) ≤ 1270) and HT0-H2980/J mol−1 ‹Dy2TeO6› = 217.942 T + 1.103 × 10−2T2 + 14.896 × 105T−1 – 70957(672 ≤ T (K) ≤ 1268). Using the standard Gibbs energies of formation of M2TeO6(s) (M = Eu, Dy) obtained from vapour pressure measurement as reported by us in previous work (Asish Jain et.al. in J Therm Anal Caloim (2015) 119:689–693) and Gibbs energy functions computed from the enthalpy measurement of M2TeO6(s) (M = Eu, Dy) of the present study, the mean value of ΔfH298o has been deduced. The mean value of ΔfH298o ‹Eu2TeO6› and ‹Dy2TeO6› were found to be −2260 ± 0.2 and − 2474 ± 0.17 kJ mol−1 respectively. The high temperature enthalpy increments on Eu2TeO6(s) and Dy2TeO6(s) are being reported for the first time.

Enthalpy increments and thermodynamic functions of rare earth samarium titanates RESmTi2O7(s) (RE = Gd,Dy)

Enthalpy measurements have been taken on GdSmTi2O7 and DySmTi2O7 by using a high-temperature differential calorimeter at temperature between 800 and 1655 K. Thermodynamic function, such as heat capacity, entropy and Gibbs energy functions of GdSmTi2O7 and DySmTi2O7, was derived using the data obtained in this study. The results are presented and compared with the data available in the literature. The polynomial expression of enthalpy increments obtained for GdSmTi2O7(s) and DySmTi2O7(s) in the temperature range 298–1700 K is given as: $$\begin{aligned} H_{\text{T}}^{0} - H_{298}^{0} / {\text{J}}\,{\text{mol}}^{ - 1} & = 252.961\,T \, + 1.596 \times 10^{ - 2} \,T^{2} + 3.705 \times 10^{6} \,T^{ - 1} - 89{,}265\quad ({\text{GdSmTi}}_{2} {\text{O}}_{7} ) \\ H_{\text{T}}^{0} - H_{298}^{0} / {\text{J}}\,{\text{mol}}^{ - 1} & = 256.504\,T \, + 1.576 \times 10^{ - 2} \,T^{2} + 3.531 \times 10^{6} \,T^{ - 1} - 89{,}721\quad \left( {{\text{DySmTi}}_{2} {\text{O}}_{7} } \right). \\ \end{aligned}$$

High-Temperature Enthalpy of La2Hf2O7 in the Temperature Range 490–2120 K

Lanthanum hafnate La2Hf2O7 was produced chemically by inverse precipitation from ammonia solution and a mixture of La and Hf nitrates, followed by hydroxide decomposition at 1250°C in air and melting of the oxide mixture in a solar furnace. The formation of La2Hf2O7 was ascertained by X-ray diffraction. The La2Hf2O7 enthalpy increment was measured in the range 490–2120 K (for the first time in the temperature ranges 490–988 K and 1740–2120 K) by drop calorimetry using a Setaram HT-1500 high-temperature differential calorimeter and a high-temperature calorimetric device. A fitted equation for the enthalpy increment was used to calculate the main thermodynamic functions (heat capacity, entropy, and Gibbs energy) in the temperature range 298–2120 K. The experimental results are compared with the published data and those assessed using the Neumann–Kopp rule.

High-temperature heat content and thermodynamic functions of REEuTi2O7 (RE = Gd, Dy) from calorimetric measurements

Titanates of gadolinium, europium, and dysprosium are considered potential candidate materials for use in the control rods of future nuclear reactors. GdEuTi2O7 and DyEuTi2O7 were synthesized by powder-pellet route and were characterized by using X-ray diffraction technique. Enthalpy increment measurements were carried out on these compounds in temperature range 795–1658 K by inverse drop calorimetric method by using a high-temperature differential calorimeter. Thermodynamic functions such as heat capacity, entropy, and Gibbs energy functions in the temperature range 298–1700 K were computed from the measured enthalpy increments.

Thermodynamic data of U3Ga5 from calorimetric measurements

U3Ga5, an intermetallic compound in the U–Ga system was prepared by arc melting method and characterised using X-ray diffraction technique. Enthalpy increment measurements on this compound were carried out in the temperature range 793–1323 K by inverse drop calorimetric method by using a high-temperature differential calorimeter. From the fitted equation for the measured enthalpy increments, thermodynamic functions such as heat capacity, entropy and Gibbs energy functions were computed in the temperature range 298–1400 K. Using the enthalpy increments and the enthalpy of formation of U3Ga5 at 1287 K derived by high-temperature mass spectrometry (Manikandan et al. in J Nucl Mater 475:87–93, 2016), the enthalpy of formation at 298 K has been deduced. The enthalpy increments and \(\Delta _{\rm f} H_{298}^{^\circ}\) of U3Ga5 are being reported for the first time.

Calorimetric measurements on rare earth titanates: RE2TiO5 (RE = Sm, Gd and Dy)

Titanates of samarium, gadolinium, and dysprosium are considered potential candidate materials for use in the control rods of future nuclear reactors. Sm2TiO5, Gd2TiO5, and Dy2TiO5 were prepared by solid-state route and characterized by XRD technique. Enthalpy increment measurements were carried out on these compounds in the temperature range 750–1660 K by inverse drop method by using a high-temperature differential calorimeter. From the fitted equations for the measured enthalpy increment data, other thermodynamic functions, namely, heat capacity, entropy, and Gibbs energy functions, were computed in the temperature range 298–1800 K. The results are presented and compared with the data available in the literature.

Enthalpy increment measurements on europium titanate

Europium titanate is a potential control rod material. Enthalpy increments of europium titanate (Eu2TiO5) were measured in the temperature range 770–1,747 K by employing the method of inverse drop calorimetry using a high-temperature differential calorimeter. Thermodynamic functions such as heat capacity, entropy and Gibbs energy function have been computed in the temperature range 298–1,800 K.

Calorimetric measurements on plutonium rich (U,Pu)O 2 solid solutions

Enthalpy increments of U (1− y) Pu y O 2 solid solutions with y = 0.45, 0.55 and 0.65 were measured using a high-temperature differential calorimeter by employing the method of inverse drop calorimetry in the temperature range 956–1803 K. From the fit equations for the enthalpy increments, other thermodynamic functions such as heat capacity, entropy and Gibbs energy function have been computed in the temperature range 298–1800 K. The results are presented and compared with the data available in the literature. The results indicate that the enthalpies of U (1− y) Pu y O 2 solid solutions with y = 0.45, 0.55 and 0.65 obey the Neumann–Kopp's molar additivity rule.

Thermodynamic functions for U 0.45Pu 0.55N

Enthalpy increments of U 0.45Pu 0.55N were measured in the temperature range of 1025–1775 K by inverse drop calorimetry using a high temperature differential calorimeter. The enthalpy increments were fitted to a polynomial in temperature and the heat capacity, entropy and Gibbs energy functions were computed. The results are presented and discussed in comparison with literature data.

Calorimetric measurements on uranium–plutonium mixed oxides

Enthalpy increments of U 1− y Pu y O 2 solid solutions with y=0.21, 0.28 and 0.40 were measured using a high-temperature differential calorimeter by employing the method of inverse drop calorimetry in the temperature range 1000–1780 K. From the fit equations for the enthalpy increments, other thermodynamic functions such as heat capacity, entropy and Gibbs energy function have been computed in the temperature range 298–1800 K. The results indicate that the enthalpies of (U,Pu)O 2 solid solutions obey the Neumann–Kopp molar additivity rule.

Calorimetric measurements on rare earth pyrohafnates RE2Hf2O7 (RE=La,Eu,Gd)

Enthalpy increment measurements have been carried out on La2Hf2O7, Eu2Hf2O7 and Gd2Hf2O7 in the temperature range 980–1740 K by using a high temperature differential calorimeter. From the enthalpy values, other thermodynamic functions, such as heat capacity, entropy and free energy functions have been generated. The high temperature Cp data of the rare earth pyrohafnates obtained in this study are discussed in relation to the crystal chemistry of these pyrochlores.

Enthalpies of formation of UNi 5, UNi 2 and UFe 2 by solution calorimetry

The enthalpies of formation of the intermetallic compounds UNi 5, UNi 2 and UFe 2 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, UNi 5, UNi 2 and UFe 2 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 UNi 5, UNi 2 and UFe 2 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.

Design and characteristics of a differential calorimeter for high-temperature measurements

A high-temperature differential calorimeter developed from the Setaram “HT 1500 Calorimeter” has been built for isothermal measurements in inorganic systems at temperatures between 600 and 1750 K. Details of the mechanical design, the auxiliary equipment and the performance (mode of operation) of the calorimeter are given. Enthalpie effects ranging from about 5 to 200 J have been measured with a reproducibility and accuracy of approximately ± 2,5%. During calorimetric measurements conducted over a period of several months at high temperatures, the new differential calorimeter proved reliable and safe to operate.

Thermodynamic properties of compounds of alkaline earth elements with other fission products

The alkaline earth fission products barium and strontium can combine with other major fission product elements such as Mo, Ce and Zr in a mixed oxide fuel pin of a fast breeder reactor to form compounds such as molybdates. cerates and zirconates. In order to understand the condition of their formation in the fuel pin basic thermodynamic data on these compounds applicable to the relevant temperature range are required. In this work enthalpy increments of BaMoO 4, BaCeO 3 and (Ba, Sr)ZrO 3 were determined relative to room temperature using a high temperature differential calorimeter. The experimentally measured enthalpy data covered the temperature range of 985–1750 K. From these enthalpy values other thermodynamic functions such as heat capacities, entropies and free energy functions were generated using C p298 0 and S 298 0 values of the compounds available in the literature. The free energies of formation of these compounds and the equilibrium barium partial pressures for the formation reactions have been computed in the temperature range of 500–2000 K and in the oxygen potential range of −376.56 kJ mol −1 to −502.08 kJ mol −1.

Thermodynamic functions of barium and strontium zirconates from calorimetric measurements

Enthalpy increment measurements have been carried out on BaZrO 3 and SrZrO 3 in the temperature range 1030–1700 K using a high-temperature differential calorimeter. From the measured enthalpy increment values, other thermodynamic functions, such as heat capacity, entropy and free energy functions, of these compounds have been calculated. The free energies of formation of BaZrO 3 and the equilibrium barium partial pressures for the formation reactions have been computed and compared with literature data. The equilibrium strontium pressures for the formation reactions of SrZrO 3 have also been computed.

A high temperature differential calorimeter

A calorimetric method of determining the heats of reaction of materials in the solid state, at temperatures up to 1100°C, has been developed. The sample is heated at a rate of 10 degC min-1 and the heat changes associated with reaction processes in the sample are measured. Values for the heats of decomposition of some carbonates have been determined. At the present stage only endothermic heats of reaction have been measured.