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1.
The vaporization of Al-Fe-Ni alloys has been investigated in the temperature range 1180 to 1508 K by Knudsen effusion mass spectrometry (KEMS). Fourteen different compositions were examined in the B2 region: 10 compositions at two fixed Al concentrations,x Al=0.45 andx Al=0.50 plus four extra compositions at constantx Ni/x Fe=1. For the first time, reliable partial pressures and thermodynamic activities of Al, Fe, and Ni have been evaluated from the measured ion intensities for both the alloy and the pure element. Gibbs energies, partial molar enthalpies, and entropies of formation for all the components have also been obtained. The relative partial molar enthalpies and entropies were found to be nearly temperature independent over the wide temperature ranges investigated. At 1400 K, the Gibbs energy of formation of Al0.50Fe0.25Ni0.25 and Al0.45Fe0.275Ni0.275, with Al(liq), Fe(fcc), and completely paramagnetic Ni(fcc,cpm) as reference states, are −37.9±0.42 kJ/mol and −38.1±0.42 kJ/mol, respectively. At the same temperature, the enthalpies of formation of Al0.50Fe0.25Ni0.25 and Al0.45Fe0.275Ni0.275, with the same reference states, are −51.5±1.7 kJ/mol and −49.2±1.7 kJ/mol, respectively.  相似文献   

2.
The enthalpies of formation at 1385 ±2 K of the following crystalline borides have been determined by high temperature solution calorimetry using liquid copper as the calorimetric solvent. Fe2B-67.87 ±8.05 kJ mol−1, Co2B -58.1 ±7.0 kJ mol−1, Ni2B -67.66 ±4.12 kJ ml−1, FeB-64.63 ±4.34 kJ mol−1, CoB -69.52 ±6.0 kJ mol−1, and NiB -40.2 ±3.77 kJ mol−1. The enthalpy of fusion of NiB has been determined to be 28.25 ±1.54 kJ mol−1 at its melting point of 1315 K. New data are reported also for the enthalpies of solution of iron, cobalt, and nickel in copper, and for the enthalpies of interaction between these metals and boron in dilute solutions in liquid copper.  相似文献   

3.
The enthalpies of formation of liquid binary (Cu+Fe, Co, Ni) alloys are studied by direct reaction calorimetry in the whole range of compositions at 1873, 1823, and 1753 K, respectively. The integral molar enthalpies of mixing are found to be positive in all three systems with the maximum values approaching 10.8±0.7 kJ/mol−1 at x Fe=0.43, 7.1±0.9 kJ/mol−1 at x Co=0.55, and 3.7±0.5 kJ/mol−1 at x N1=0.53. Partial molar enthalpies at infinite dilution constitute 59.4±3.3 kJ/mol−1 for iron, 44.3±4.1 kJ/mol−1 for cobalt, and 14.9±2.2 kJ/mol−1 for nickel in liquid copper. Similar values for copper in liquid iron, cobalt, and nickel are 36.6±3.9, 45.3±6.0, and 17.7±4.4 kJ/mol−1, respectively. The results are compared with the thermodynamic data available in literature and discussed in connection to the equilibrium-phase diagrams. In particular, decreasing from Cu-Fe to Cu-Ni liquid alloys positive values of the excess thermodynamic functions of mixing are fully in accord with the growing stability of phases in these systems. The excess entropies of mixing are estimated by combining the established enthalpies with carefully selected literature data for the excess Gibbs functions. Analysis of possible contributions to the enthalpies of mixing indicates that the experimentally established regularity in ΔH values along the 3d series is likely to arise from the difference in d-band width and d-electron binding energy of the alloy constituents.  相似文献   

4.
The standard enthalpies of formation of eight samarium alloys with late transition metals have been determined by direct synthesis calorimetry at 1273±2 K. The following values of ΔH f 0, in kJ·(mole atom), are reported: SmNi5, −27.4±0.5; Sm5Rh4, −66.5±1.0; SmRh2, −65.5±1.2; SmPd, −82.4±2.0; Sm3Pd4, −87.2±2.5; SmPd3, −82.9±2.5; SmPt, −108.7±3.5; and SmPt2, −100.2±2.6. The results are compared with predicted values from the Miedema model, with available literature data for SmNi5, SmPd, and SmPt, and with earlier values for similar compounds formed by other lanthanide metals reported by this laboratory. The observed relationships between the enthalpies of formation and the number of f-electrons in the considered binary alloys RE n Me m (RE=lanthanide elements; and Me=Group VIII elements) are discussed.  相似文献   

5.
The thermodynamics of mixed oxide compounds of the type Li2O · Ln2O3 (Ln=Nd or Ce) has been studied by measuring the lanthanide content of molten LiCl-Li2O-Li solutions in equilibrium with the solid mixed oxide compound at 923 K. The observed total lanthanide mole fraction in the molten salt when in equilibrium with both solid Ln2O3 and LiLnO2 was found to be 1.0×10−4 and 5.9×10−4 for Ln=Nd and Ce, respectively. The calculated mole fractions of LiLnO2 in the molten salt when the solid mixed oxide compound was present are 2.6×10−5 and 2.1×10−4 for LiNdO2 and LiCeO2, respectively. The unexpectedly large “solubilities” of the sesquioxides in the presence of Li2O can be explained by the formation of complex oxide species, LiLnO2 and Li3LnO3, in the molten salt solutions. The equilibrium constants and the free energies of formation for these species were derived from the measured data. The free energies of formation of the solid mixed oxide compounds at 923 K were found to be −1014±1.5 kJ/mol for LiNdO2 and −1006±11.0 kJ/mol for LiCeO2.  相似文献   

6.
The standard enthalpy of formation of Sc5Si3 has been determined by solute-solvent drop calorimetry at (1473±2) K. The following value is reported: ΔH f o (mean)=−(719.1±34.0) kJ mol−1. This result is compared with corresponding published values for the enthalpies of formation of Me5Si3, with Me=Mn, Cr, V, Ti. This comparison shows regularly increasing negative enthalpies of formation from Mn5Si3 to Sc5Si3. LETTTIA TOPOR, formerly Senior Research Associate, The James Franck Institute, The University of Chicago,  相似文献   

7.
The standard enthalpies of formation of TiSi2 and VSi2 have been measured by a new calorimetric method. The following results are reported: ΔH f ° (TiSi2) = −(170.9 ± 8.3) kJ mol−1 and ΔH {f °} (VSi2) = −(112.4 ± 6.0) kJ mol−1. These results are compared with experimental, assessed, and predicted values reported in the literature and with our own data for the corresponding borides. Estimates are given for the enthalpies of formation of the silicides of scandium and chromium.  相似文献   

8.
The Standard enthalpies of formation of 14 neodymium alloys have been determined by direct synthesis calorimetry at 1477 ± 2 K. The following values of ΔH f o (kJ/g atom) are reported: NdNi5, −(26.2 ± 1.1); Nd5Ru2, −(17.2 ± 1.9); NdRu2, −(18.8 ± 1.2); Nd5Rh4, −(59.9 ± 2.5); NdRh, −(64.2 ± 2.0); NdRh2, −(59.9 ± 1.1); NdRh3, −(44.4 ± 1.6); NdPd, −(77.2 ± 2.7); NdPd3, −(73.3 ± 2.3); Nd5Ir3, −(59.7 ± 2.7); NdIr2, −(67.6 ± 1.5); NdPt, −(104.4 ± 2.6); NdPt2, −(97.9 ± 2.4); and NdP5, −(55.0 ± 3.1). The results are compared with available literature data for some of the neodymium alloys and with predicted values from the Miedema model.  相似文献   

9.
Experimental studies on phase equilibria in the multicomponent system PbO-ZnO-CaO-SiO2-FeO-Fe2O3 in air have been conducted to characterize the phase relations of a complex slag system used in commercial lead oxidation smelting. The liquidus in the pseudo-ternary section ZnO-“Fe2O3”-(PbO + CaO + SiO2) with the CaO/SiO2 weight ratio of 0.35 and the PbO/(CaO + SiO2) weight ratio of 5.0 has been constructed using results of over 100 high-temperature equilibration and quenching experiments followed by electron probe X-ray microanalysis. The liquidus in this pseudoternary section contains primary phase fields of spinel (zinc ferrite) Zn x Fe3−x O4+y , zincite Zn u Fe1−u O, melilite Pb v Ca2−v Zn w Fe1−w Si2O7, hematite Fe2O3, magneto-plumbite PbFe10O16, and dicalcium silicate Ca2−t Pb t SiO4. The laboratory results are compared with the slags obtained from an industrial reactor.  相似文献   

10.
Standard molar enthalpies of formation of MeAl (Me = Ru,Rh, Os,Ir)   总被引:2,自引:0,他引:2  
The standard molar enthalpies of formation of RuAl, RhAl, and IrAl have been determined by the direct combination method using a high-temperature calorimeter operated at (1473 ±2) K. The following values are reported: ΔH f o (RuAl) = −(124.1 ± 3.3) kJ/mol; ΔH f o (RhAl) =-(212.6 ± 3.2) kJ/mol; and ΔH f o (IrAl) = -(185.5 ± 3.5) kJ/mol. For OsAl, an approximate value is −77 kJ/mol. The results are compared with available data for related alloys and with predicted values.  相似文献   

11.
Vaporization of niobium diselenide has been investigated by mass spectrometry, mass-loss effusion, chemical analysis, and x-ray analysis. We have established that the equilibrium vapor above niobium diselenide consists of mainly Se.2 molecules at 1400–1600 K; as selenium is removed from the sample, self-intercalation of diselenide occurs up to Nb1.28Se2. We have determined the standard enthalpies of dissociation and formation of self-intercalated diselenide of limiting composition as 405.3 kJ/mole and −260.4 kJ/mole, respectively. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(402), pp. 61–64, July–August, 1998.  相似文献   

12.
The enthalpies of formation of the intermetallic compounds CaGa4, Ca3Ga8, and CaGa2, at 298.15 K, were determined by high-temperature liquid gallium solution calorimetric measurements to be −24.9 ± 4.9 kJ·g at.−1, −25.4 ± 2.4 kJ·g at.−1, and −38.8 ± 4.8 kJ·g at.−1, respectively. The enthalpies of formation of CaGa4 at 988 K and that of Ca3Ga8 at 1070 K were determined, using precipitation calorimetry, to be −28.2 ± 1.7 kJ·g at.−1 and −22.5 ± 1.4 kJ·g at.−1, respectively. The integral enthalpy of mixing of the (Ca-Ga) liquid alloys (ΔH 0) measured at 1309 K are described by the following Redlich-Kister equation:
The partial enthalpy of calcium in gallium at infinite dilution , deduced from the measured integral enthalpies of mixing at 1309 K, is −104.8 ± 1.7 kJ·g at.−1, which is in very good agreement with that derived from the gallium solution calorimetric measurements at 1074 K (−108.2 ± 6.9 kJ·g at.−1).  相似文献   

13.
Adiabatic oxygen combustion calorimetry has been used to determine the enthalpies of combustion of the chromium carbides Cr23C6, Cr7C3 and Cr3C2 to be—15,057.6±12.4 kJ ·mole−1,—4985.3±3.8 kJ ·mole−1 and—2400.5±0.9 kJ ·mole−1 respectively. The products of combustion in all cases were Cr2O3 and CO2. Using standard data for Cr2O3 and CO2, the enthalpies of formation of the carbides have been calculated to be:fΔH 298 o Cr23C6=−290.0±27.6 kJ·mole−1 fΔH 298 o Cr7C3=−149.2±8.5 kJ·mole−1 fΔH 298 o Cr3C2=−81.1±2.9 kJ·mole−1  相似文献   

14.
The chemical potential of O for the coexistence of Ni + NiO and Ni + Cr2O3 + NiCr2O4 equilibria has been measured employing solid-state galvanic cells, (+) Pt, Cu + Cu2O // (Y2O3)ZrO2 // Ni + NiO, Pt (-) and (+) Pt, Ni + NiO // (Y2O3)ZrO2 // Ni + Cr2O3 + NiCr2O4, Pt (-) in the temperature range of 800 to 1300 K and 1100 to 1460 K, respectively. The electromotive force (emf) of both the cells was reversible, reproducible on thermal cycling, and varied linearly with temperature. For the coexistence of the two-phase mixture of Ni + NiO, δΜO 2(Ni + NiO) = −470,768 + 171.77T (±20) J mol−1 (800 ≤T ≤ 1300 K) and for the coexistence of Ni + Cr2O3 + NiCr2O4, δΜO 2(Ni + Cr2O3 + NiCr2O4) = −523,190 + 191.07T (±100) J mol−1 (1100≤ T≤ 1460 K) The “third-law” analysis of the present results for Ni + NiO gives the value of ‡H 298 o = -239.8 (±0.05) kJ mol−1, which is independent of temperature, for the formation of one mole of NiO from its elements. This is in excellent agreement with the calorimetric enthalpy of formation of NiO reported in the literature.  相似文献   

15.
Studies on the kinetics of chlorination of ZrO2. powder by carbon tetrachloride vapor in mixture with nitrogen in a low-temperature range of 650 to 825 K at different periods and partial pressures of carbon tetrachloride were carried out. The chlorination results at 650 and 675 K seem to follow a diffusion-controlled reaction model of Jander’s type: [1−(1−R)1/3]2 =k 1t whereR is the fraction of ZrO2 chlorinated in timet andk 1 is the rate constant. The approximate activation energy of the process was calculated fromk 1 values at the previously mentioned two temperatures and found to be 278 kJ/mole. For the chlorination in the temperature range of 700 to 750 K, the topochemical reaction model 1−(1−R) 1/3 =k 2t was followed. The rate constant,k 2, was found to be proportional to the partial pressure of carbon tetrachloride. The activation energy of this reaction was calculated to be 154 kJ/mole. In the temperature range of 775 to 825 K, the rate of chlorination was found to be directly proportional to the time of chlorination following Langmuir’s Adsorption Isotherm. Because of the very high rate of chlorination and thermodynamic possibility of decomposition of CCl4 above 773 K, the rate-controlling step has been suggested to be the decomposition of the adsorbed complex formed by ZrO2 with carbon and chlorine atoms, obtained from the decomposition of CCl4 vapor. The activation energy of the process was 54 kJ/mole. In view of nearly complete chlorination of ZrO2 by CCl4 in a very short period of about 15 minutes, at a temperature around 800 K and lesser possibility of formation of toxic product gases, the process is recommended for commercial application.  相似文献   

16.
The solubilities of FeO, FeAl2O4, NiO, and NiAl2O4 were measured in cryolite-alumina melts at 1020 °C. FeO was found to be the stable solid phase at alumina concentrations below 5.0 wt pct, while FeAl2O4 was stable above that. The corresponding figure for the nickel system was 3.0 wt pct Al2O3. These values correspond to Gibbs energies of formation of the aluminates (from the constituent oxides) of −17.6 and −29 kJ/mol, respectively. In alumina-saturated melts in the range 980 to 1050 °C, the solubilities of both aluminates increased with increasing temperature, the apparent enthalpies of solution being 65 kJ/mol for FeAl2O4, and 249 kJ/mol for NiAl2O4. Investigation of the solubilities of the aluminates as a function of the NaF/AlF3 ratio in alumina-saturated melts at 1020 °C showed maxima at a molar ratio of around 5. The results are discussed in terms of the species apparently existing in the solution, and are consistent with the solute species being fluorides, not oxyfluorides. The activity coefficients of FeF2 (liquid) and NiF2 (solid) in dilute solution in cryolite are found to be 0.22 and 1.2, respectively.  相似文献   

17.
The phase relations in the NaCl-AlCl3 system ( ) have been determined in the temperature range from 373 to 623 K by isothermal equilibration, electrical conductivity, and electromotive force measurements. Only one ternary compound, NaAlCl4, was found to be stable, with a melting point of 426 K. The standard Gibbs energy of formation of NaCl and NaAlCl4 has been measured in the temperature range from 423 to 623 K by a novel galvanic cell technique involving in-situ electrogenerated chlorine electrode in the Na/β″-alumina/NaCl, NaAlCl4/Cl2,C and Al/NaCl, NaAlCl4/Cl2,C cells along with the Na/β″-alumina/NaCl,NaAlCl4/Al cell. The Δ f G NaCl(s )/o and values have been calculated as −412.4+0.095 T (±1) kJ mol−1 and −1117.5+0.2460 T (±2) kJ mol−1, respectively. The standard entropy of NaAlCl4 (s) at 298 K, computed from the results of the study and the auxiliary information from the literature (184 J K−1 mol−1), show good agreement with the estimated JANAF value (188.28 J K−1 mol−1). The enthalpy of formation of NaAlCl4 (l) from NaCl (s) and AlCl3 (s) at 550 K obtained in the present study (−1850 J mol−1) is in agreement with that computed from the heat-capacity measurements (−1910 J mol−1). The present measurements are unique, as a new electrochemical technique is employed in a cell with low-melting sodium chloroaluminate electrolyte to obtain the thermodynamic properties of NaCl and NaAlCl4 at significantly low temperatures. The Gibbs energy of formation of NaCl (s) is, thus, measured at temperatures as low as 423 K by an electrochemical technique for the first time, in this work.  相似文献   

18.
The enthalpies of mixing of liquid copper with liquid silver and with solid titanium, zirconium, and hafnium have been measured by high temperature reaction calorimetry at 1371 to 1373 K. A least squares treatment of the data for copper-silver alloys yields the following expression for the molar enthalpy of mixing: ΔHmix = ϰAgϰCu(17.66 − 5.46 ϰAg) kJ mol−1. The enthalpies of solution of solid titanium, zirconium, and hafnium in dilute solutions in liquid copper are all exothermic; the following values were found: -2.0 kJ mol−1 for Ti, -52.5 kJ mol−1 for Zr, and -46.3 kJ mol−1 for Hf. These values are all significantly less exothermic than predicted by the semiempirical theory of Miedema. The enthalpies of formation of congruent melting intermetallic phases in the systems Cu-Ti, Cu-Zr, and Cu-Hf were measured by drop calorimetry or by solution calorimetry in liquid copper. The enthalpies of formation of the solid alloys have been compared with corresponding data for the liquid alloys.  相似文献   

19.
Partial (for aluminum) and integral mixing enthalpies of ternary Si-Ni-Al liquid alloys are examined by high-temperature calorimetry under isoperibolic conditions at 1770 ± 5 K. Alloys of five radial sections with a constant ratio of silicon-to-nickel mole fractions (xSi/xNi = 0.85/0.15; 0.7/0.3; 0.5/0.5; 0.3/0.7, and 0.15/0.85) within the interval compositions to aluminum mole fraction xAl ∼ 0.6 are studied. The mixing enthalpies of Si-Ni-Al alloys are characterized by great exothermal values. Exothermal partial enthalpies of aluminum mixing increase at infinite dilution with increasing nickel concentration in starting binary alloys ( reaches −17.0 ± 3.3 kJ/mole for section with xSi/xNi = 0.85/0.15 and −119.0 ± 11.2 kJ/mole for xSi/xNi = 0.15/0.85). An analysis of alloy-formation energy parameters in the ternary Si-Ni-Al system indicates that the interaction of the components in the bounded binary Si-Ni and Ni-Al systems greatly contributes to ΔmH, the effect of the former prevailing. The thermochemical properties of ternary alloys and of Ge-Ni-Al melts and simulated mixing enthalpies of ternary Sn (C)-Ni-Al liquid alloys are compared. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 79–85, 2007.  相似文献   

20.
The standard Gibbs energies of formation of Ca3As2, Ca3Sb2, and Ca3Bi2 were determined by a chemical equilibration technique yielding the following results: 3Ca(1)+2As(1)=Ca3As2 (s) Δ=−723,800+172.8T (±23,700)(J/mol) 1273 to 1573 K 3Ca(1)+2Sb(1)=Ca3Sb2(s) Δ=−726,300+159.3T(±24,600) (J/mol) 1273 to 1573K 3Ca(1)+2Bi(1)=Ca3Bi2(s) Δ=−696,400+195.6T(±23,200) (J/mol) 1148 to 1323 K The thermodynamic data for removal of arsenic, antimony, and bismuth by other experimental investigations were discussed in terms of the activity coefficients of these compounds in slags. The stabilities of these compounds were also discussed by using the critical oxygen partial pressures calculated from the above equations. D.J. MIN, formerly Graduate Student, Department of Metallurgy, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan  相似文献   

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