Direct Reaction Calorimetry Research Articles

A thermodynamic investigation of the Li–Sb system

Many standard thermodynamic data in the binary system Li–Sb can be found in literature; however, they are often derived from electrochemical measurements taken at higher temperatures. The uncertainties associated with the extrapolation of these high-temperature data to room temperature are, however, inherently large. Therefore, a comprehensive investigation of the thermodynamic properties in the Li–Sb system was conducted in this work to generate more reliable data. Four different experimental techniques were used for the investigations. The heat capacities for both binary compounds, Li2Sb and Li3Sb, were measured for the very first time. In addition, the enthalpies of formation for both compounds were determined by drop solution and direct reaction calorimetry. Furthermore, Knudsen effusion mass spectrometry was performed to measure partial enthalpies and activities of Sb.

Calorimetric investigations of UPb3 compound

Interaction of uranium based metallic fuels and lead coolant can lead to formation of intermetallic compounds of U-Pb system. To understand U-Pb interactions, it is important to know thermodynamic properties of intermetallic compounds present in this system, UPb3 and UPb. In the present work, enthalpy increment, heat capacity and enthalpy of formation of UPb3 intermetallic compound were determined. The enthalpy increment was determined by high temperature Calvet calorimeter and heat capacity was determined using DSC. The heat capacity data was used to calculate thermodynamic parameters of the compound as a function of temperature. The enthalpy of formation at 843K was determined using successive precipitation method, by direct reaction calorimetry. The enthalpy of formation at 843K, from Pb(l) and U(l), was −28.9kJat-mol−1 and after adjusting enthalpy increments of pure elements and compound, the enthalpy of formation of the compound at 298K, from Pb(s) and U(α) was found to be −20.0kJ at-mol−1.

Ground state properties and thermoelectric behavior of Ru2VZ (Z=Si, ge, sn) half-metallic ferromagnetic full-Heusler compounds

The ground state properties namely structural, mechanical, electronic and magnetic properties and thermoelectric behavior of Ru2VZ (Z=Si, Ge and Sn) half-metallic ferromagnetic full-Heusler compounds are systematically investigated. These compounds are ferromagnetic and crystallize in the Heusler type L21 structure (prototype: Cu2MnAl, Fm-3m 225). This result is confirmed for Ru2VSi and Ru2VSn by experimental work reported by Yin and Nash using high temperature direct reaction calorimetry. The studied materials are half-metallic ferromagnets with a narrow direct band gap in the minority spin channel that amounts to 31meV, 66meV and 14meV for Ru2VSi, Ru2VGe, and Ru2VSn, respectively. The total spin magnetic moment (Mtot) of the considered compounds satisfies a Slater–Pauling type rule for localized magnetic moment systems (Mtot=(NV−24)µB), where NV=25 is the number of valence electrons in the primitive cell. The Curie temperature within the random phase approximation (RPA) is found to be 23K, 126K and 447K for Ru2VSi, Ru2VGe and Ru2VSn, respectively. Semi-classical Boltzmann transport theories have been used to obtain thermoelectric constants, such as Seebeck coefficient (S), electrical (σ/τ) and thermal conductivity (κ/τ), power factor (PF) and the Pauli magnetic susceptibility (χ). ZTMAX values of 0.016 (350K), 0.033 (380K) and 0.063 (315K) are achieved for Ru2VSi, Ru2VGe and Ru2VSn, respectively. It is expected that the obtained results might be a trigger in future experimentally interest in this type of full-Heusler compounds.

The effect of a fourth element (Co, Cu, Fe, Pd) on the standard enthalpy of formation of the Heusler compound Ni2MnSn

The standard enthalpies of formation of quaternary Heusler compounds (X, Ni)2MnSn (X = Co, Cu, Fe, Pd) were investigated experimentally using high temperature direct reaction calorimetry. Lattice parameters of these compounds were determined using X-ray diffraction analysis. Microstructures were identified using scanning electron microscopy and energy dispersive spectroscopy. The effect of an additional X element on the standard enthalpy of formation of the Heusler compound Ni2MnSn is discussed.

Standard enthalpies of formation of selected Ni2YZ Heusler compounds

The standard enthalpies of formation (ΔfH°) of selected ternary Ni-based Heusler compounds Ni2YZ (Y = Co, Cu, Fe, Hf, Mn, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mole of atoms) of the Heusler structured (L21, prototype Cu2MnAl, Pearson symbol cF16, space group Fm3(_) m) compounds are: Ni2MnGa (−29.8 ± 3.9); Ni2MnIn (−24.5 ± 2.0); Ni2MnSn (−29.7 ± 2.9); Ni2TiGa (−42.5 ± 2.2); Ni2TiIn (−28.5 ± 1.1); Ni2TiSn (−46.8 ± 2.0), for the B2 compound (prototype CsCl, Pearson cP2, space group Pm3(_) m): Ni2MnAl (−32.0 ± 2.8), for the inverse Heusler structured (i-L21, prototype Li2AgSb, Pearson symbol cF16, space group F4(_) 3 m) compound: Ni2CuSn (−12.5 ± 2.1), for the compounds of the L12 (prototype AuCu3, Pearson symbol cP4, space group Pm3(_) m) structure: Ni2CuAl (−38.9 ± 3.1); Ni2FeGe (−25.8 ± 3.0). Several off-stoichiometric alloys in the Ni–Mn–Sn system were also investigated: Ni0.55Mn0.20Sn0.25 (−26.6 ± 1.0); Ni0.45Mn0.30Sn0.25 (−27.5 ± 2.6); Ni0.40Mn0.35Sn0.25 (−26.6 ± 2.6); Ni0.25Mn0.50Sn0.25 (−20.9 ± 2.6); Ni0.50Mn0.30Sn0.20 (−21.0 ± 3.2); Ni0.50Mn0.35Sn0.15 (−20.1 ± 1.7). Values are compared with those from first principles calculations in published papers and the Open Quantum Materials Database (OQMD). Lattice parameters were determined using X-ray diffraction analysis. Microstructures were characterized using scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS). Differential scanning calorimetry (DSC) was used to measure the melting points of the compounds.

Standard enthalpies of formation of selected Rh2YZ Heusler compounds

The standard enthalpies of formation (ΔfH°) of selected ternary Rh-based Rh2YZ (Y=Cu, Fe, Mn, Ni, Ru, Ti, V; Z = Al, Ga, In, Si, Ge, Sn) compounds were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mol of atoms) are, for the Heusler compound Rh2MnSn (−40.1 ± 3.6), for the B2-structured compounds: Rh2FeAl (−48.5 ± 2.9); Rh2MnAl (−72.4 ± 2.7); Rh2MnGa (−55.3 ± 2.0); Rh2MnIn (−35.3 ± 1.9), for the tetragonal compounds: Rh2FeSn (−28.9 ± 1.3); Rh2TiAl (−97.6 ± 2.2); Rh2TiGa (−79.0 ± 1.8); Rh2TiSn (−74.7 ± 3.1). Values are compared with those from first principles calculations in published papers and the Open Quantum Materials Database (OQMD). Lattice parameters of these compounds are determined using X-ray diffraction analysis (XRD). Microstructures were characterized using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS).

Standard enthalpies of formation of selected XYZ half-Heusler compounds

The standard enthalpies of formation of selected ternary half-Heusler type compositions XYZ (X=Au, Co, Fe, Ir, Ni, Pd, Pt, Rh, Ru; Y=Hf, Mn, Ti, Zr; Z=Ga, Sn) were measured using high temperature direct reaction calorimetry. The measured standard enthalpies of formation (in kJ/mole of atoms) of the half-Heusler compounds (prototype MgAgAs, Pearson symbol cF12, space group F-43m) are, IrMnSn (−29.4±1.8); NiTiSn (−52.6±2.4); PtHfSn (−98.8±3.4); PtMnSn (−55.8±2.6); PtTiSn (−93.6±3.3); PtZrSn (−104.9±3.8); for the B2 compound (prototype CsCl, Pearson symbol cP2, space group Pm-3m), RuMnGa (−26.9±1.7); for the C1 structured (prototype CaF2, Pearson symbol cF12, space group Pm-3m) or the C1b structured compound IrMnGa (−40.9±1.7). Indicative standard enthalpies of formation of the following compounds were obtained, half-Heusler compounds AuMnSn, CoTiSn, IrZrSn, NiHfSn, NiZrSn, PdHfSn, PdZrSn, RhTiSn; Heusler compound (prototype Cu2MnAl, Pearson symbol cF16, space group Fm-3m) RhMnSn; hexagonal compound (prototype BeZrSi, Pearson symbol hP6, space group P63/mmc) PtMnGa and another type of hexagonal compound (prototype RhHfSn, Pearson symbol hP18, space group P-62c) RhHfSn, IrZrsn, RhZrSn. Values were compared with ab initio calculations from AFLOW and OQMD. Lattice parameters of these compounds were determined using X-ray diffraction (XRD) analysis. Microstructures were characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Selected alloys were further annealed to investigate phase transformations and phase relationships.

Standard enthalpies of formation of selected Ru2YZ Heusler compounds

The standard enthalpies of formation of selected ternary Ru-based Heusler compounds Ru2YZ (Y=Fe, Hf, Mn, Ti, V; Z=Al, Ga, In, Si, Ge, Sn) were measured using high temperature direct reaction calorimetry. The measured enthalpies of formation (in kJ/mole of atoms) of the Heusler compounds are, Ru2FeGe (−19.7±3.3); Ru2HfSn (−24.9±3.6); Ru2MnSi (−46.0±2.6); Ru2MnGe (−29.7±1.0); Ru2MnSn (−20.6±2.4); Ru2TiSi (−94.9±4.0); Ru2TiGe (−79.1±3.2); Ru2TiSn (−60.6±1.8); Ru2VSi (−55.9±1.7);for the B2-structured compounds, Ru2FeSi (−28.5±0.8); Ru2HfAl (−70.8±1.9); Ru2MnAl (−32.3±1.9); Ru2MnGa (−25.3±3.0); Ru2TiAl (−62.7±3.5); Ru2VAl (−30.9±1.6); Ru2ZrAl (−64.5±1.5). Values were compared with those from published first principles calculations and the OQMD (Open Quantum Materials Database). Lattice parameters of these compounds were determined using X-ray diffraction analysis (XRD). Microstructures were identified using scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS).

Structural stability of intermetallic phases in the Ga–Ti system

The total energies of intermetallic compounds in the Ga–Ti system are calculated employing electronic density functional theory (DFT) using pseudopotentials constructed by the projector augmented waves (PAW) method in the generalized gradient (GGA) approximation for the exchange and correlation energy. The calculations are performed for the experimentally observed compounds at their ideal stoichiometry as well as for structures which are stable in systems of early transition metals or rare earth elements with p elements of columns IIIB, IVB, and VB. The calculated formation enthalpy of the hexagonal B8 2–GaTi 2 compound is in excellent agreement with the value obtained by direct reaction calorimetry. The composition dependence of the enthalpies of formation is slightly asymmetric, the values of the enthalpies of formation being slightly more negative in the Ga-rich side. For the stable intermetallic compounds, the calculated zero-temperature lattice parameters agree well with those obtained experimentally at ambient temperature. Furthermore, for stable phases with unit-cell-internal degree(s) of freedom, the results of ab initio calculations show good agreement when compared with data obtained by structural analysis of X-ray diffraction.

The determination of the integral enthalpies of mixing of liquid Au–In–Sn alloys and the enthalpy of formation of the Au 4In 3Sn 3 compound

With a view to modelling the Au–In–Sn alloy system, the enthalpies of mixing of liquid Au–In–Sn alloys have been measured as a function of Au content by drop calorimetry at 609 °C for constant In:Sn ratios of 1:1, 1:3 and 3:1. For each of the three sections studied, the enthalpies of mixing were exothermic. In addition, the enthalpy of formation of the ternary Au 4In 3Sn 3 at 298 K was measured both by direct-reaction calorimetry and by tin-solution calorimetry.

Role of elastic and shear stabilities in the martensitic transformation path of NiTi

Due to the importance of NiTi as a shape-memory material and the uncertainty regarding its atomisitic martensitic transformation path, a thorough investigation to understand the structural stability governing this displacive phase transformation is warranted. We investigate elastic and shear stabilities of NiTi using first-principles calculations with the highly precise full-potential linearized augmented plane-wave method. Ambiguities of the B2, R, B19, $\text{B}1{9}^{\ensuremath{'}}$, and proposed B33 structures are resolved, and we establish that the $P3$ symmetry is preferred for the R phase of equiatomic NiTi, and the phase stability of each structure is established by examining calculated formation energies, which show agreement with direct reaction calorimetry experiments. Additionally, all single-crystal elastic constants, Young's, bulk and shear moduli, Poisson's ratio, and the Zener anisotropy of the B2, R, B19, $\text{B}1{9}^{\ensuremath{'}}$, and B33 phases are calculated and presented yielding agreement with experiment that exceeds that of previous calculations. To investigate the susceptibility to shearing, generalized stacking-fault energetics are calculated for the {001}, {011}, and {111} slip planes of the B2 phase. Burgers vectors and shear resistance are established while examining atomic shuffling throughout the imposed shear; the {001} and {111} stacking faults possess high-energy barriers. By investigating various deformation mechanisms related to these stacking faults, we find an instability to $⟨100⟩{011}$ slip in the B2 phase. Using this and reviewing previously proposed atomistic transformation paths, the mechanisms governing the direct martensitic transformation of NiTi between the austenite and the martensite are identified. Barrierless transformation paths from the B2 phase to the $\text{B}1{9}^{\ensuremath{'}}$ phase and from the B2 phase to the B33 phase are proposed.

Enthalpy of Formation in the Al-Ni-Ti System

The Al-Ni-Ti ternary system forms the basis of several alloy systems of practical importance. This study was undertaken to provide additional experimental thermodynamic data for the modeling of the Al-Ni-Ti system. High-temperature direct reaction calorimetry has been used to determine the standard enthalpy of formation of several Al-Ni-Ti alloys. The stability of the L21 structure over the B2 structure at the stoichiometric composition of Ni0.5Al0.25Ti0.25 was estimated from the enthalpy results to be 6.8 kJ/mol. The lattice parameters and melting temperatures of these compounds are also reported.

Structural stability of intermetallic phases in the Sn–Ti system

The total energies of intermetallic compounds in the Sn–Ti system are calculated employing electronic density-functional theory (DFT) using pseudopotentials constructed by the projector augmented waves (PAW) method in the generalized gradient (GGA) approximation for the exchange and correlation energy. The calculations are performed for the experimentally observed compounds at their ideal stoichiometry as well as for structures which are stable in systems of early transition metals or rare earth elements with p-elements of columns IIIB, IVB, and VB. The calculated formation enthalpy of the hexagonal Sn 5Ti 6 compound is slightly less exothermic than the value obtained by direct reaction calorimetry. For the stable intermetallic compounds, the calculated zero-temperature lattice parameters agree well with those obtained experimentally at ambient temperature. More, for stable phases with unit cell-internal degree(s) of freedom, the results of ab initio calculations show good agreement when compared with data obtained by structural analysis of X-ray diffraction. The composition dependence of the enthalpies of formation is slightly asymmetric. The electronic densities of state of the D8 8- Sn 3Ti 5 compound have been computed; the curve shows the hybridization of Sn 5p states with Ti 3d states. The stability of the intermetallic compounds in the Ti–Sn system is due to this hybridization.

Calorimetric and phase equilibria studies of the Ni–Sn–Bi system

AbstractThe phase equilibria at 1273 K were investigated and an isothermal section of the Ni‐Sn‐Bi phase diagram was constructed. The phase boundaries are inclined to the Bi‐rich region that is agreement with phase equilibria at lower temperatures. The molar enthalpies of formation of liquid ternary Ni–Sn–Bi alloys have been determined at 833, 873 and 933 K by direct reaction calorimetry using pellets of 325 mesh powders of pure Ni, Sn and Bi. Measurements were performed with alloys containing from 0.05 to 0.10 mole fractions of nickel, and at ratios of tin and bismuth mole fractions XSn/XBi = 2.8, 1.2 and 0.43. The experimental calorimetric data were used to calculate a regular solutions parameter of the ternary liquid phase by means of two different thermodynamic data files. It was found that the Ni–Sn–Bi ternary liquid phase could be described as temperature independent ternary regular solution. The assessed values of the ternary interaction parameter are ‐280 J·mol–1 and 56 000 J·mol–1, depending on the binary parameters used. Enthalpies of formation of solid binary phases were measured, too. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Calorimetric and phase diagram studies of the Co–Sn system

Enthalpies of formation of cobalt–tin compounds (βCo 3Sn 2, CoSn, CoSn 2, βCoSn 3) have been obtained by direct reaction calorimetry at 1287, 1032, 629 and 604 K, respectively. Integral molar enthalpies of formation of the liquid phase ( Δ f H L,T ) have been measured by solution calorimetry at 991 and 1020 K, and by direct reaction calorimetry at 1010 and 1303 K. The experimental ( Δ f H L,T ) values in the tin-rich region have been approximated by regular solution model with temperature dependent parameters. The temperature and the enthalpy of the order/disorder transformation αCo 3Sn 2 → βCo 3Sn 2 were found to be 833 ± 2 K and 750 ± 30 J/mol, respectively. A metastable phase corresponding to the formula Co 2Sn has been observed. The occurrence of the polymorphic transition αCoSn 3/βCoSn 3 was confirmed although the corresponding transition temperature could not be observed sometimes.

Phase stability and cohesive properties of Ti–Zn intermetallics: First-principles calculations and experimental results

The total energies and equilibrium cohesive properties of 48 intermetallics in the Ti–Zn system are calculated employing electronic density-functional theory (DFT), ultrasoft pseudopotentials and the generalized gradient approximation for the exchange-correlation energy. Selected experiments are performed to determine the heat of formation by calorimetry and to measure the isotropic elastic moduli by pulse-echo method. In alloys containing 50 at.% or less Ti, where it was possible to synthesize nearly single phase specimens, the calculated heats of formation agree within a few kJ/mol of the calorimetry data, while the calculated isotropic elastic constants agree within 5% of the experimental values. The demonstrated level of agreement suggests high accuracy for the calculated cohesive properties of structures where there is no measured data. For the stable intermetallics, the calculated zero-temperature lattice parameters agree to within ±1% of experimental data at ambient temperature. In two complex phases, TiZn 16 and Ti 3Zn 22, the unit cell parameters obtained from ab initio calculations show an excellent agreement with those obtained by rigorous structural analysis of X-ray diffraction data. For all structures considered, we provide optimized unit cell geometries. Also, for most structures we provide zero-temperature bulk moduli and their pressure derivatives, as defined by the equation of state. In Ti-rich alloys, sluggish reaction kinetics between Ti and Zn powder and phase diagram constraints pose significant problems, thus hindering accurate measurement of heat of formation by direct reaction calorimetry. Therefore, the calculation of such a quantity, and other cohesive properties as well, of solid phases in the entire composition range by ab initio methods remains an attractive viable option. The bonding between Ti and Zn is discussed based on the analyses of calculated densities of states and charge densities; these analyses suggest that bonding in Ti–Zn intermetallics shares many features in common with transition-metal aluminides due, in particular, to the presence of pronounced hybridization between Ti d and Zn p electronic states.

Thermodynamic investigation of the moderately dilute liquid Bi–Fe–Sb alloys

The molar enthalpies of formation of liquid ternary Bi–Fe–Sb alloys have been determined at 1065 K by direct reaction calorimetry using the drop method. Measurements were performed along two sections: X Bi/ X Sb = 1/9 and 1/4. The experimental calorimetric data and estimated values with a Redlich-Kister formulation are compared.

Calorimetric measurement of the intermetallic compounds Cr 3Ga and CrGa 4 and thermodynamic assessment of the (Cr–Ga) system

The enthalpies of formation have been measured for the two binary compounds Cr 3Ga and CrGa 4 richest and least rich in chromium of the (Cr–Ga) system. We have used two types of calorimetric method: direct reaction and progressive precipitation calorimetry. Thermodynamic optimizations for the binary (Cr–Ga) system using Calphad method are investigated and a set of parameters describing the Gibbs energy of the different phases is given, the phase diagram has been also calculated and presented.

Enthalpies of formation of the Al–Ni intermetallic compounds

The Al–Ni system has been investigated by direct reaction calorimetry at high temperatures. Enthalpies of formation of the intermetallic compounds AlNi 3, AlNi, Al 3Ni 2, and Al 3Ni were determined and compared with the available experimental values based on calorimetric and emf measurements and with the calculated values from theoretical models. X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA) were used to check structural state and stoichiometry of each phase.

Calorimetric study of the aluminium–titanium system

The intermetallic compounds of the Al–Ti system were investigated by direct reaction calorimetry at high temperatures. New enthalpies of formation were determined and compared with the available experimental values based on calorimetric measurements and with the predicted values from Miedema’s semi-empirical model. X-ray powder diffraction (XRD) and electron probe microanalysis (EPMA) were used to check the crystal structure and the homogeneity of the calorimetric products.