High-temperature Mixing Calorimetry Research Articles

Calorimetric study of enthalpies of mixing in liquid (aluminium–gallium–yttrium) alloys

The partial yttrium ( Δ mix H ¯ Y ) and the integral (Δ mix H) enthalpies of mixing of liquid ternary Al–Ga–Y alloys have been determined by high-temperature mixing calorimetry at T = 1750 K. The measurements have been performed along five sections with constant ratios of Al and Ga in a range of 0.0 < x Y < 0.64. The Δ mix H has been estimated in the ternary system using asymmetric geometric models and the Toop model has been chosen as the most adequate one. The deviation between experimental and that predicted by the geometric model values of Δ mix H was found to be 1.54%, so ternary interaction is negligibly small at the experimental temperature. The possible contribution of binary intermetallide compounds into the thermodynamics of the liquid Al–Ga–Y alloys is discussed.

High temperature calorimetric examination of enthalpies of mixing in liquid (gadolinium–germanium–manganese) alloys

Liquid alloys of (gadolinium–germanium–manganese) have been studied by a high-temperature mixing calorimetry at ( T = 1830) K. The measurements have been performed along five sections with x Ge: x Mn = 0.25:0.75, 0.4:0.6, 0.5:0.5, 0.7:0.3, and 0.8:0.2 for 0.0 < x Gd < 0.55. The integral enthalpy of mixing (Δ mix H) has been calculated from the experimental Δ mix H ¯ Gd by Darken’s equation. The values of Δ mix H have been also estimated using nine geometric models and the results of Muggianu model implementation provide the best agreement with the experimental data. Two interpolation methods have been used for describing the integral enthalpy of mixing in the ternary liquid alloys. The Δ mix H values estimated by the interpolation methods agree as well with each other as with the Muggianu model prediction. The differences between the Δ mix H values determined by experiment and from the model are small and vary from (−4.2 up to 3.5) kJ · mol −1, which is evidence for a negligibly small ternary interaction in liquid (Gd–Ge–Mn) alloys. Extreme Δ mix H values are observed in the boundary (Gd–Ge) system. Consequently, the interaction between Ge and Gd atoms make a major contribution to the thermodynamics of liquid (Gd–Ge–Mn) alloys.

Calorimetric study of enthalpies of mixing in liquid gallium–germanium–yttrium alloys

The yttrium partial enthalpies of mixing ( Δ mix H ¯ Y ) and the integral enthalpies of mixing (Δ mix H) of liquid Ga–Ge–Y alloys have been determined by high-temperature mixing calorimetry for five sections with constant ratios of Ga and Ge at 1760 K. Plots of concentration dependence of Δ mix H ¯ Y / ( 1 − x Y ) 2 show sharp inflections, which correspond to transition of the liquid alloys into heterogeneous state and can be used for determination of liquidus surface. Furthermore, the Δ mix H has been estimated in the ternary system using seven geometric models and the Bonnier model has been chosen as the most adequate one. The differences between the experimental and model integral enthalpies of mixing have been described by polynomial concentration dependence. The possible contribution of binary and ternary intermetallide compounds into the thermodynamics of the liquid Ga–Ge–Y alloys has been considered.

Enthalpies of formation of the palladium sulphides

A high-temperature mixing calorimetry method has been used for the thermochemical study of the Pd-S system. The standard molar enthalpies of formation of the palladium sulphides were derived by measuring the heat effect associated with the formation of a low-melting (Pd+S) liquid alloy from the elements, and the effects associated with the formation of the same melt from the sulphide investigated and one of the pure constituent elements. The following values are reported for the standard enthalpies of formation for the four sulphides studied: ΔfHm°(PdS, 298.15 K)=−(78.1±11.0) kJ·mol−1; ΔfHm°(Pd16S7, 298.15 K)=−(580.1±36.2) kJ·mol−1; ΔfHm°(Pd3S, 298.15 K)=−(96.5±10.5) kJ·mol−1; ΔfHm°(Pd4S, 298.15 K)=−(99.2±11.2) kJ·mol−1.

ChemInform Abstract: A New Calorimeter for Temperatures Above 1400 K

Abstract A new high temperature calorimeter, based on modifications and improvements to the commercial integrated heat flux Setaram design is described. In this unit thermal effects are measured differentially along the vertical axis of the calorimeter. Performance was tested at 1473 K through the measurement of the enthalpies of formation of intermetallic compounds, using high temperature mixing calorimetry.

A new calorimeter for temperatures above 1400 K

Abstract A new high temperature calorimeter, based on modifications and improvements to the commercial integrated heat flux Setaram design is described. In this unit thermal effects are measured differentially along the vertical axis of the calorimeter. Performance was tested at 1473 K through the measurement of the enthalpies of formation of intermetallic compounds, using high temperature mixing calorimetry.

Standard molar enthalpies of formation of Irme ( me = Ti, Zr, or Hf) and of OsTi by high-temperature mixing calorimetry

The standard molar enthalpies of formation Δ f H m o of the intermetallic compounds IrTi, IrZr, IrHf, and OsTi have been determined by high-temperature mixing calorimetry at (1473 ± 2) K. The following values of Δ f H m o/(kJ·mol −1) are reported: IrTi, −(168.6±7.5); IrZr, −(171.3 ± 7.7); IrHf, −(193.3 ± 9.6); OsTi, −(136.9 ± 7.2). There are no calorimetric values for these compounds in the literature. The new results are compared with recently published predicted values. Comparisons are made also with our own experimental values for the 1-1 compounds of Ti, Zr, and Hf with Pt, Pd, Rh, and Ru, and with reported results for the compounds of Ti with Ni, Co, and Fe, and of Zr with Ni and Co. With few exceptions these comparisons show increasing negative enthalpies of formation from the 3d to the 4d to the 5d late transition metals, and also from Ti to Zr to Hf. A more detailed analysis shows certain similarities in observed trends between the compounds of (Fe, Co, Ni) and (Os, Ir, Pt) which are not shared by the corresponding compounds of (Ru, Rh, Pd).

Standard enthalpies of formation of Ptti, Ptzr, and Pthf

The standard enthalpies of formation of the intermetallic compounds PtTi, PtZr, and PtHf have been determined by high temperature mixing calorimetry in a new calorimeter operated at (1473 ± 2) K. The following values of Δ° are reported. PtTi:-159.3 ± 12.9 kJ mol-1; PtZr: -191.9 ± 12.4 kJ mol-1; PtHf: -227.3 ± 13.2 kJ mol-1. These results are compared with recent experimental values obtained by high temperature direct combination calorimetry, with predicted values and with our own recently published data for the equiatomic alloys of Ti, Zr, and Hf with Pd, Rh, and Ru. The enthalpies of formation of the Pt compounds are significantly more exothermic than the corresponding Pd, Rh, and Ru compounds.

Thermochemistry of the intermetallic compounds RuTi, RuZr, and RuHf

The standard enthalpies of formation of the Intermetallic compounds RuTi, RuZr, and RuHf have been determined by high temperature mixing calorimetry at 1400 K. The following values of ΔHf are reported: RuTi: -153.9 ± 7.4 kJ mol−1; RuZr: -137.3 ± 6.8 kJ mol−1; RuHf: -183.5 ±10.4 kJ mol−1. Since there are no experimental data for these compounds in the literature, comparisons are made with predicted and estimated values. The new data also are compared with recent results reported by the authors for the corresponding equiatomic alloys of Pd and Rh with Ti, Zr, and Hf. This comparison indicates that RuTi is significantly more exothermic than inferred from the systematic trend(s) shown by the other compounds studied.

Standard enthalpies of formation of PdZr and PdHf

The enthalpies of formation of the intermetallic compounds PdZr and PdHf have been determined by high temperature mixing calorimetry at 1400 K. The following results are reported: PdZr: ΔH°f = −122.6 ± 7.0 kJ mol−1; PdHf: ΔH°f = −134.8 ± 7.8 kJ mol−1. Our results are compared with estimated and predicted literature values and with approximate experimental values recently obtained by direct high temperature reaction calorimetry. The enthalpies of formation of the equiatomic alloys of the Ti-group metals with Pd show increasing negative values in the series TiPd < ZrPd < HfPd.

Standard enthalpies of formation of RhTi, RhZr and RhHf

The standard enthalpies of formation of the intermetallic compounds RhTi, RhZr and RhHf have been determined by high temperature mixing calorimetry at 1400 K. The following values of ΔH f o are reported: RhTi, −143.0 ± 9.8 kJ mol −1; RhZr, −151.8 ± 7.1 kJ mol −1; RhHf, −191.6 ± 4.3 kJ mol −1. These results are compared with values predicted in the literature and with a recent experimental value for RhZr. Comparison of the new data with our recently published results for the corresponding compounds of palladium with titanium, zirconium and hafnium show that in both families there are increasing negative enthalpies of formation in the sequence TiX < ZrX < HfX.

Standard enthalpy of formation of CrSi 2 by high-temperature mixing calorimetry

The standard molar enthalpy of formation of CrSi 2 has been determined by mixing calorimetry at (1400 ± 2) K. In these experiments the liquid alloy Cu 0.70Si 0.25Cr 0.05 is formed in the calorimeter from the elements or from CrSi 2. The following result is reported: Δf H m o(298.15 K) = −(77.4 ± 13.2) kJ · mol −1. This result is compared with earlier experimental values and with the recently predicted value of Niessen and Miedema. Among the disilicides of the first-row transition metals from Sc to Cr the least negative enthalpy of formation is found for CrSi 2.

Enthalpy of Formation of PdTi by High Temperature Mixing Calorimetry

Enthalpy of Formation of PdTi by High Temperature Mixing Calorimetry