Direct Reaction Calorimetry Research Articles

Experimental determination of the partial enthalpies of mixing of tin and tellurium in SnTe melts

The partial molar enthalpies of Sn and Te at high dilution in SnTe melts have been measured by direct reaction calorimetry (drop method) with the help of a Tian-Calvet high temperature calorimeter, at 860, 1000 and 1100 K. They show only very weak temperature dependence. The values of the interaction parameters were also measured. The results obtained will be used to compare the different models available for strongly interacting liquid alloys.

Enthalpies of formation of liquid and solid (palladium + indium) alloys

Enthalpies of formation of (Pd + In) alloys have been obtained by direct reaction calorimetry using a very high temperature calorimeter between 1,425 and 1,679 K in the concentration range 0 < x{sub Pd} < 0.66. They are very negative with a minimum {Delta}{sub mix}H{sub m}{degree} = {minus}59.6 {+-} 2.5 kJ mol at x{sub PD} = 0.59 and independent of temperature within the experimental error. The integral molar enthalpy of mixing is given by {Delta}{sub mix}H{sub m}{degree}/{l_brace}kJ/mol{r_brace} = x(1 {minus} x) ({minus}126.94 {minus} 92.653x {minus} 83.231x{sup 2} {minus} 734.49x{sup 3} + 949.07x{sup 4}), where x = x{sub PD}. The limiting partial molar enthalpy of palladium in indium was calculated as {Delta}h{sub m} (Pd liquid in {infinity} liquid In) = {minus}127 {+-} 5 kJ/mol. The results are discussed and compared with the enthalpies of formation of solid alloys. The anomalous behavior of the partial enthalpy of Pd is assumed to be due to the charge transfer of, at most, two electrons of In to Pd.

Enthalpies of formation of RuGe compounds and of the Gerich RuGe liquid by direct reaction calorimetry

The enthalpies of formation of RuGe and Ru2Ge3 have been measured by direct reaction calorimetry at 1173 K. Ru0.4Ge0.6: ΔfH (1173 K)=−34.8 kJ mol−1 (±1)Ru0.5Ge0.5: ΔfH (1173 K)=−28.7 kJ mol−1 (±1.3) with reference to pure metals in their equilibrium states at the reaction temperature. The Ge rich RuGe liquid was also studied by dissolution of Ru in the liquid alloy of variable composition at 1423 K. The results are compared with the existing literature.

Enthalpies of formation of solid NiCr and NiV alloys by direct reaction calorimetry

A SETARAM HT1500 calorimeter has been used successfully to measure the enthalpies of formation of solid NiCr alloys at 1583 K by a direct reaction method. The results are in good agreement with those given in the literature. Having proved that the apparatus was suitable to measure such quantities, measurements of the enthalpies of formation of solid NiV alloys were made at 1473 K. Experiments were made at 16 compositions; data are reported for Ni-rich f.c.c. and V-rich b.c.c. solid solutions and for the σ phase.

The limiting molar partial enthalpies of mixing of iron, cobalt, nickel, palladium and platinum in liquid gallium and indium

Gallium and indium have been used as solvents for the determination of the molar partial enthalpy of mixing Δ mix h m o(TM, Ga or In) (denoting liquid transition metal (TM) in infinite liquid gallium or indium) of the pure liquid transition metals Fe, Co, Ni, Pd and Pt by direct reaction calorimetry between 1000 K and 1500 K with the exception of Δ mix h m o(Fe, In) (because of the shape of its equilibrium phase diagram). All the limiting enthalpies listed below refer to the liquid state. With pure gallium as solvent, they correspond to the reaction TM(liq) − n Ga(liq) → TM 1Ga n (liq) at the experimental temperature T e, with n ⪢ 1. 1. (i) Δ mix h m o in gallium is found for Fe, Co, Ni, Pd and Pt to be −2, −44, −82, −144 and −155 kJ mol −1. 2. (ii) Δ mix h m o in indium is found for Co, Ni, Pd and Pt to be +28, −25, −127 and −114 kJ mol −1. In both solvents, these limiting enthalpies vary with a similar trend. This observation makes it possible to predict the limiting molar partial enthalpy Δ mix h m o(Fe, In) of mixing of iron in indium as +70 kJ mol −1. The results have been compared with the data proposed by Miedema and co-workers.

Enthalpy of Formation of Liquid Ag-Bi and Ag-Bi-Sn Alloys

The enthalpies of formation of liquid Ag-Bi and Ag-Sn alloys were determined by direct reaction calorimetry at 878 K, 783 K and 878 K, respectively. The molar enthalpy of formation of the Ag-Bi binary liquid alloys can be expressed as: Δ max H o m(Ag-Bi,liq) =x Ag (1-x Ag )(11878-3199x Ag -1071x 2 Ag -4681x 3 Ag ) J.mol -1 So, in the molar fraction range 0<X Ag <0.80, the enthalpies of formation are positive (extremum at x Ag =0.35 with Δ mix H o m(Ag-Bi,liq) =+2100 J.mol -1 ); on the Bi-rich side, the heat of formation seems weakly exothermic (extremum at x Ag =0.95 with Δ mix H o m =-260 J.mol -1 )

Thermodynamic behaviour of metallic melts at high dilution according to the associated solution model

The associated solution model developed previously has been applied to binary at high dilution. If A aB b associates are assumed and the contribution of the weak interactions between the species is neglected, it has been pointed out that the value of the partial enthalpy of A in pure B is close to zero when a ≠ 1 and close to that of the standard enthalpy of formation of the associate when a = 1. The limiting partial enthalpies of Pd and Pt in Ge were determined by direct-reaction calorimetry (the drop method). We found these had values of −108.9 kJ mol −1 and −108.6 kJ mol −1 respectively at 1272 K. Since these values are very close to that of the standard enthalpies of formation of PdGe (−104 kJ mol −1) and PtGe (−106 kJ mol −1) clusters respectively, they confirm the existence of two kinds of associate (Pd 2Ge + PdGe and Pt 2Ge + PtGe respectively) in the binaries. This conclusion is especially useful in the case of the Pd-Ge melts the thermodynamic behaviour of which can be explained in the framework of the model assuming one (Pd 2Ge) or two species.

Thermodynamic Investigation of Solid and Liquid Au-Te Alloys

Abstract The heat content of solid and liquid AuTe2 compound was measured from 298 K to T (471–1022 K) on heating (drop method) with the help of a Tian-Calvet calorimeter. The heat capacity of the liquid compound as well as its enthalpy of fusion were deduced. The enthalpy of the liquid decreases strongly when temperature increases especially for T>923K. Such a behaviour cannot be explained easily by the existence of a short-range order since the enthalpy of formation is only weakly negative. The enthalpies of dissolution of Au and AuTe2 in Au-Te melts were also determined by direct reaction calorimetry at 728 K with respect to concentration (0 < x Au < 0.18 and 0 < x AuTe2 < 0.27). With the help of the heat content data determined previously we calculated the enthalpy of formation of the AuTe2 compound at 298 K (− 3.3 kJ per mole of atoms). Such a low negative value as well as the low melting temperature agree well with the assumption of some associated state of the liquid in spite of the weakly negative enthalpy of mixing.

Thermodynamic investigation of the solid and liquid AuSb alloys

The heat content of solid and liquid AuSb 2 compound was measured from 298 K to T (375–963 K) on heating (drop method) with the help of a Tian-Calvet calorimeter. The heat capacity of the liquid compound as well as its enthalpy of fusion were deduced. The enthalpy of the liquid decreases strongly when temperature increases between the melting point and 831 K. The enthalpy of formation of the AuSb melts was also determined by direct reaction calorimetry at 916 K with respect to concentration. The enthalpy of mixing is weakly negative in the whole range of concentration ( min f = −3·47 kJ/mol at x Au = 0·775) in agreement with the results of Béja at 923 K. disagree with the much more negative earlier data of Kameda et al. and of Hino et al. by emf and vapor pressure measurements. Finally, the liquid/Au(cr) phase boundary determined at 916 K from the break in the h f ( x Au) curve agrees well with the phase diagram calculated by Okamoto and Massalski but not with their experimental results.

Thermodynamic Investigation of the Pd–Pt–Ge Ternary Alloys at 1269 K

AbstractThe enthalpy of formation, ∆f H of the Pd–Pt–Ge alloys was measured at 1269K with respect to composition by direct reaction calorimetry (drop method) with the help of high-temperature Calvet-type calorimeters. The measurements were performed at four values (0.10, 0.25, 0.50 and 0.75) of R = x Pt/x Pt+x Ge and one (0.60) of R′ = x Pd/x Pd+ x Ge From the breaks of the enthalpy curves with respect to composition for given R and R′values we obtained evidence for the existence of a series of Pd2Ge–Pt2Ge solid solutions as well as the boundaries of the liquid + solid solution domains. We also deduced the enthalpy of formation of the Pd2Ge–Pt2Ge solution with respect to composition. The Pd2Ge–Pt2Ge pseudo-binary can be considered as ideal.The thermodynamic behaviour of the melts is characterized by strong negative deviations from ideality, as was also the case for the Pd–Ge and Pt–Ge binaries. The isoenthalpic curves at 1269 K show that the minimum of the enthalpy lies on a straight line from pure Pd2Ge ...

The determination of the enthalpy of formation and the enthalpy increment of Cd 0.5Te 0.5 by Calvet calorimetry

The enthalpy of formation of Cd 0.5Te 0.5(s) has been determined using a Calvet calorimeter at 785 K by direct reaction calorimetry. The heat changes were measured for the additions of Cd(s) or Te(s) from 298 K to a reaction crucible containing the other liquid metal at 785 K. Measurements were also carried out to determine the enthalpy changes due to the direct reaction of the Te(l) and Cd(l) at 785 K. The enthalpies of formation of Cd 0.5Te 0.5 calculated from the two sets of experiments were in agreement. The H T° H 298° values of the Cd 0.5Te 0.5 compound have also been determined in the temperature range 406–826 K by the drop method. Using ΔH fm° at 785 K and H T H 298° values of Cd 0.5Te 0.5, ΔH fm° at 298 K was determined to be −(50.349±0.510) kJ mol −1.

Thermodynamic investigation of the PdPtGe ternary alloys at high temperature

The enthalpies of formation h f of the PdPtGe alloys were measured at 1623 K as a function of composition by direct reaction calorimetry (drop method) using a high-temperature Calvet-type calorimeter. The measurements were performed for four values (0.10, 0.25, 0.50 and 0.75) of R= x Pt/( x Pt+ x Ge) and two values (0.60 and 0.75) of R′ = x Pd/( x Pd+ x Ge). The thermodynamic behaviour of the melts is characterized by strong negative deviations from ideality as observed for the PdGe and PtGe binaries. The iso-enthalpy curves at 1623 K show that the enthalpy minimum lies near the straight line from pure Pd 2Ge to pure PtGe as at 1269 K. The thermodynamic functions of formation of the ternary melt were calculated within the framework of the regular associated model assuming that two kinds of associates are present in the binaries, i.e. Pd 2Ge and PtGe. The values of the thermodynamic parameters used for this calculation were those of the two binaries with Ge assuming ideality for the PdPt system. With these assumptions, the behaviour of the ternary melts seems to be well described in terms of the enthalpy of formation. The Gibbs free energy of formation of the PdPtGe liquid phase was also calculated in the same way and will be compared with experimental results measured by Knudsen-cell mass spectrometry when available.

Thermodynamic investigation of the Rh-Ge and Ir-Ge binary alloys

The enthalpies of formation Δ f H m, of the Ir-Ge and Rh-Ge alloys were measured at 1266 K with respect to composition by direct reaction calorimetry (drop method) with the help of high temperature Calvet-type calorimeters. The values lead to the following equation valid for 0 < x Ir < 0.21 and 0 < x Rh < 0.32 ▪ The thermodynamic behaviour of the melts is characterized by strong negative deviations from ideality suggesting some chemical short-range order. It will be interesting to investigate in future work the thermodynamic properties of these two binaries in the concentrated range and their temperature dependence.

Thermodynamic Investigation of the Pd-Pb Binary Alloys

The enthalpy of formation, h f , of the Pd-Pb alloys was measured in the 625 to 1240 K temperature range with respect to composition by direct reaction calorimetry (drop method) with the help of high-temperature Calvet-type calorimeters. Furthermore, we determined also some phase boundaries from the breaks of the h f (x) curves in agreement with the published phase diagram. The thermodynamic behaviour of the melts is characterized by strong negative deviations from ideality suggesting strong chemical short-range order with high thermal stability

Enthalpies of formation of some solid hafnium nickel compounds and of the Ni-Rich HfNi liquid by direct reaction calorimetry

In the course of a systematic study of binary transition metal alloys, the enthalpies of formation of five Hf-Ni compounds were measured by direct reaction calorimetry: Hf0.17Ni0.83(l/6HfNi5): ΔfH(1323 K) = − 37,000 J/mole of atoms (±3200) Hf0.22Ni0.781/9Hf2Ni7): Δf(1623 K) = −50,700 J/mole of atoms (±2000) Hf0.45Ni0.55(l/2OHf9Ni11): ΔfH(1473 K) = −54,500 J/mole of atoms (±2200) Hf0.50Ni0.50(l/2HfNi): ΔfH(1573 K) = −47,900 J/mole of atoms (±1800) Hf0.67Ni0.33(l/3Hf2Ni): ΔH(1423 K) = −36,700 J/mole of atoms (±1300) with reference to pure metals in their equilibrium states at the reaction temperatures. The Ni-rich Hf-Ni liquid was also studied by the dissolution of Hf in the liquid alloy of variable composition at 1743 and 1633 K. Results show that the enthalpy of formation of the liquid at a given composition depends strongly on temperature, and this point suggests the existence of associations in the liquid. The melting temperature of Hf0.22Ni0.78(Hf2Ni7) which was found (1705 K) is slightly lower than the one (1743 K) given in the literature.

Thermodynamic Investigation of the Pt—Pb Binary Alloys

AbstractThe enthalpy of formation, hf, of the Pt—Pb alloys was measured in the 923–1316 K temperature range with respect to composition by direct reaction calorimetry (drop method) with the help of high temperature Calvet‐type calorimeters. Furthermore we determined also some phase boundaries from the breaks of the hf(x) curves. — The thermodynamic behaviour of the melts is characterized by moderate negative deviations to ideality suggesting some chemical short‐range order (h = −15.88 kJ · mol−1 at 923 K for χPt = 0.53). The associates are very sensible to temperature since the excess heat capacity is positive with a maximum of about 10.2 J · K−1 · mol−1 near χPt = 0.71. Such a behaviour differs strongly from that of the Pd‐Pb system which shows a strongly negative enthalpy of mixing (h = −38.4 kJ · mol−1) without any temperature dependence.

Thermodynamic investigation of PtGe and PdGe binary alloys

Abstract The enthalpy of formation, ΔHf, of Pt-Ge and Pd-Ge alloys was measured in the temperature range 1270–1680 K with respect to composition by direct reaction calorimetry (drop method) with the help of high temperature Calvet-type calorimeters. The results agree well with our previous measurements. The enthalpies of formation and melting of the PtGe and Pd2Ge intermediate phases were also obtained. Furthermore, we determined also some phase boundaries from the breaks of the ΔHf(x) curves in agreement with the published phase diagram. From our enthalpy data and those of the free enthalpy of formation of the melts determined by Knudsen cell effusion mass spectrometry we were able to derive also the thermodynamic properties of PtGe and Pd2Ge at their melting points. These lead to the calculation of solid compound-liquid domains in agreement with the published ones and our experimental determinations. The thermodynamic behaviour of the two melts is characterized by strong negative deviations to ideality, suggesting strong chemical short-range order. The stoichiometries of the associates are strongly connected with the highest melting intermediate compounds of both binaries, i.e. Pd2Ge and PtGe. Their stability seems very high, since the excess heat capacities of the liquid phases are particularly low. Such a conclusion is in agreement with the low values of the entropy of melting of the compounds when compared with those deduced from additivity.

Calorimetric investigation of the Au-Pb system

The enthalpy of formation h f of Au-Pb alloys was measured at 695, 871 and 1123 K by direct reaction calorimetry (drop method) with the help of a high temperature Calvet calorimeter. The measurements led to the following equations: h f(kJ mol −1)= χ Au(1-χ Au) (−12.2686 + 8.1423 χ Au) at 695 K; h f ( kJ mol−1)= χ Au(1 − χ Au ) (−6.1750 + 3.4653 χ Au) at 871 K; h f (kJ mol −1)= χ Au(1- χ Au (−4.4416 + 5.6702 χ Au) at 1123 K. We also obtained the boundary of the liquid + Au(s) region from the breaks in the h f( χ Au) curves. From our enthalpic data and those of the literature for the free enthalpy of formation we calculated at 695, 871 and 1123 K the mole fractions corresponding to the gold-rich liquidus were in good agreement with our experimental values. Our investigation allows us to state definitely that the enthalpy of formation depends strongly on the temperature. The positive excess heat capacity suggests accentuated short-range order in the melts which has to be investigated with reference to associated models.

Enthalpies of formation of liquid and solid (gallium + palladium) alloys

The enthalpies of formation of liquid (Ga + Pd) alloys were determined by direct reaction calorimetry in the temperature range 1322 <T/K < 1761 and the molar fraction range 0 <x Pd < 0.87. The enthalpies are very negative with a minimum Δmix H m = −70.4 ± 3.0 kJ mol-1 atx Pd = 0.6, independent of the temperature. Limiting partial molar enthalpies of palladium and gallium were calculated as Δh m (Ga liquid in ∞liquid Pd) = −265 ± 10 kJ mol−1 and Δh m (Pd liquid in ∞liquid Ga) = -144 ± 5 kJ mol−1. The integral molar enthalpy is given by Δmix H m =x(1-x) (-143.73 -232.47x + 985.77x 2-4457.8.x 3 + 6161.1x 4 + 2577.4x 5), wherex = x Pd. Moreover, values for the enthalpies of formation and fusion of PdGa, Pd2Ga, and the solid solution (withx Pd = 0.8571) have been proposed. These results have been discussed taking into account the equilibrium phase diagram.

Measurement of enthalpic parameters using a differential calorimetric method: Application to in-Bi alloys

An attempt is made to develop a calorimetric method by taking full advantage of the differential possibilities offered by the Tian-Calvet calorimeter. This method is intended to measure the enthalpic parameter, defined as the limiting value (dilute solutions) of the derivative of the partial enthalpy of mixing with respect to the concentration, in liquid In-Bi alloys. The results, although rather scattered, exhibit a systematic discrepancy when compared with those obtained by the classical direct reaction calorimetry method with the same calorimeter. They are in better agreement with the values estimated from simple thermodynamic models.