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1.
Hideki Ono-Nakazato Kenji Taguchi Tateo Usui Keishi Tamura Yuuji Tomatsu 《Metallurgical and Materials Transactions B》2001,32(6):1113-1118
The standard Gibbs energies of formation of Cr2N and CrN have been measured by an equilibration technique and by using thermogravimetry and differential thermal analysis
(TG-DTA) at temperatures ranging from 1232 to 1523 K. The results are expressed as follows:
The standard Gibbs energies of formation of Cr2N and CrN determined by the present work are more negative than the values in the JANAF Tables by about 14 and 5 kJ/mol, respectively,
in the measured temperature range. 相似文献
2.
Hideki Ono Masaya Nakahata Fumitaka Tsukihashi Nobuo Sano 《Metallurgical and Materials Transactions B》1993,24(3):487-492
The standard Gibbs energy of formation of MgO was determined from the measurement of the ΔG° for the reaction
; by equilibrating Mg and Nb with a magnesia crucible and is expressed as follows: Mg(l)+ l/2O2(g) = MgO(s) ΔG° = −657,000(±5000) + 141(±13)T [J/mol] (973 to 1323 K)
The standard Gibbs energies of formation of SrO and BaO were determined by equilibrating silver and MO(M: Sr, and Ba) in a
graphite crucible on the basis of the reactionM(in Ag) + CO (g) = MO (s) + C (s), yielding the following results:
相似文献
3.
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) ΔG°=−723,800+172.8T (±23,700)(J/mol) 1273 to 1573 K 3Ca(1)+2Sb(1)=Ca3Sb2(s) ΔG°=−726,300+159.3T(±24,600) (J/mol) 1273 to 1573K 3Ca(1)+2Bi(1)=Ca3Bi2(s) ΔG°=−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
4.
The standard Gibbs energies of formation of barium phosphide and barium orthophosphate were determined by a chemical equilibration
technique yielding the following results: 3Ba(1)+P2(g)=Ba3P2 (s) ΔG°=−732,000+156.1T(±12,800) (J/mol) 3BaO (s)+P2(g)+5/2O2(g)=Ba3(PO4)2(s) ΔG°=−2,523,000+580.0T(±16,600) (J/mol)
The stability and the thermodynamic behavior of barium compounds as reaction products of dephosphorization of steel were discussed
in terms of the oxygen partial pressure and the activity coefficient of Ba1.5P in molten Ba saturated with CaO.
D.J. MIN, formerly Graduate Student, Department of Metallurgy, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan 相似文献
5.
6.
The standard free energies of formation of calcium phosphide and calcium stannide were determined by a chemical equilibration
technique, yielding the following results: 3Ca(1) + P2(g) = Ca3P2(s) ΔG° = −653,460(±7110) + 144.01(±4.98)T (J/mol)1000 °C to 1300 °C2Ca(1) + Sn(1) = Ca2Sn(s) ΔG° = −353,970(±1670) + 79.28(±1.26)T (J/mol)1000 °C to 1300 °C 1120 °C The experimental data to express the thermodynamics for removal of phosphorus and tin from
molten iron by calcium based slags by other investigators were discussed in terms of the activity co-efficients of Ca3P2 and Ca2Sn in slag melts by using the present results described above. 相似文献
7.
Du Sichen S. Sheetharaman L. -I. Staffansson 《Metallurgical and Materials Transactions B》1989,20(6):911-917
The standard Gibbs energies of formation of Cr3C2, Cr7C3, and Cr23C6 have been determined by electromotive force (emf) measurements using galvanic cells of the type (−) Cr, CrF2, CaF2 // CaF2 // CaF2, CrF2, ‘Cr−C’ (+)
The measurements have been carried out in the temperature range 1002 to 1176 K. The ΔG° values obtained in the present work are generally in agreement with some of the earlier emf measurements but differ significantly
from those obtained by Cr2O3−CO equilibrium studies. 相似文献
8.
9.
The Gibbs free energies of formation of strontium and barium zirconates have been determined in the temperature range 960
to 1210 K using electrochemical cells incorporating the respective alkaline-earth fluoride single crystals as solid electrolytes.
Pure strontium and barium monoxides were used in the reference electrodes. During measurements on barium zirconate, the oxygen
partial pressure in the gas phase over the electrodes was maintained at a low value of 18.7 Pa to minimize the solubility
of barium peroxide in the monoxide phase. Strontium zirconate was found to undergo a phase transition from orthorhombic perovskite
(o) with space groupCmcm; D
2h
17
to tetragonal perovskite (t) having the space group 14/mcm;D
4h
18
at 1123 (/+- 10) K. Barium zirconate does not appear to undergo a phase transition in the temperature range of measurement.
It has the cubic perovskite (c) structure. The standard free energies of formation of the zirconates from their component
binary oxidesAO (A = Sr, Ba) with rock salt (rs) and ZrO2 with monoclinic (m) structures can be expressed by the following relations: SrO (rs) + ZrO2 (m) → SrZrO3 (o) ΔG° = -74,880 - 14.2T (/+-200) J mol-1 SrO (rs) + ZrO2 (m) → SrZrO3 (t) ΔG° = -73,645 - 15.37T (/+-200) J mol-1 BaO (rs) + ZrO2 (m) → BaZrO4 (c) ΔG° = -127,760-1.79T (/+-250) J mol-1 The results of this study are in reasonable agreement with calorimetric measurements reported in the literature. Systematic
trends in the stability of alkaline-earth zirconates having the stoichiometry AZrO3 are discussed. 相似文献
10.
Standard gibbs energies of formation of the carbides of manganese by emf measurements 总被引:3,自引:0,他引:3
Du Sichen S. Seetharaman L. -I. Staffansson 《Metallurgical and Materials Transactions B》1988,19(6):951-957
The standard Gibbs energies of formation of Mn7C3, Mn5C2, Mn15C4, and Mn23C6 have been obtained from emf measurements using galvanic cells of the type (-)Mn, MnF2, CaF2//CaF2//CaF2, MnF2, ‘Mn-C’(+) The measurements have been carried out in the temperature range 909 to 1247 K. In the case of measurements with
Mn-C alloy containing 12.9 wt pct C (Mn7C3-C two-phase region at room temperature), the slope change in the emf-temperature curve at 1181 K suggests the formation of
a hitherto unidentified phase above this temperature. 相似文献
11.
Du Sichen 《Metallurgical and Materials Transactions B》1990,21(2):313-320
The relative partial molar Gibbs energies of vanadium in the vanadium-carbon system have been determined for the V-C alloys
containing 36.7, 41.2, 43.1, 44.8, 45.5, 46.8, 50.5, and 54.0 at. pct carbon by using galvanic cells of the type (−) V, VF3, CaF2 // CaF2 // CaF2, VF3, ‘V-C’ (+) The measurements were carried out in the temperature range of 816 to 1008 K. The relative partial molar Gibbs
energies of carbon have been calculated in the same composition range. The relative integral molar Gibbs energy in the VC
single-phase region can be expressed asG
M = −98,850 + 72,242XC + (24.81 −37.23X
C)TJ/mol The standard Gibbs energies of formation of V4C3-x and V2CC can be represented as ΔG° = −67,208 + 9.37T J/mol of V0.60C0.40 and ΔGδ = −62,581 + 7.10T J/mol of Va66Co.34 respectively. 相似文献
12.
A thermodynamic analysis of chemical composition data for a series of iron alloys containing chromium and carbon has been
completed. These data were obtained from literature compilations for alloys equilibrated for extended times at 700 °C under
neutral atmospheres. The results of this analysis, when supplemented with thermochemical data from the literature, permitted
the calculation of the standard Gibbs energies of formation for the chromium carbides Cr7C3 and Cr23C6 over the range 600 to 1000 °C. These standard Gibbs energies were compared to data for these carbides from other sources.
Available Gibbs energy data for the third pure chromium carbide, Cr3C2, were also evaluated. For each of these three compounds, a separation of the values for the Gibbs energy of formation into
two distinct groups was observed. Each of these groups can be classed according to the nature of the experimental study used,
whether it be a high temperature solid-gas equilibration involving a system of a carbide-chromic oxide-carbon (or chromium)
with carbon monoxide, on one hand, or a series of investigations concerned mainly with electrolytic cell measurements, plus
the work on which the present study is based. It is suggested that the differences in the Gibbs energies of formation for
the respective carbides are associated with 1) the nonstoichiometric nature of these carbides and 2) possible dissolution
of oxygen in the carbides during the equilibration studies. 相似文献
13.
Phase relations in the system Mn-Rh-O are established at 1273 K by equilibrating different compositions either in evacuated
quartz ampules or in pure oxygen at a pressure of 1.01 × 105 Pa. The quenched samples are examined by optical microscopy, X-ray diffraction, and energy-dispersive X-ray analysis (EDAX).
The alloys and intermetallics in the binary Mn-Rh system are found to be in equilibrium with MnO. There is only one ternary
compound, MnRh2O4, with normal spinel structure in the system. The compound Mn3O4 has a tetragonal structure at 1273 K. A solid solution is formed between MnRh2O4 and Mn3O4. The solid solution has the cubic structure over a large range of composition and coexists with metallic rhodium. The partial
pressure of oxygen corresponding to this two-phase equilibrium is measured as a function of the composition of the spinel
solid solution and temperature. A new solid-state cell, with three separate electrode compartments, is designed to measure
accurately the chemical potential of oxygen in the two-phase mixture, Rh + Mn3−2xRh2xO4, which has 1 degree of freedom at constant temperature. From the electromotive force (emf), thermodynamic mixing properties
of the Mn3O4-MnRh2O4 solid solution and Gibbs energy of formation of MnRh2O4 are deduced. The activities exhibit negative deviations from Raoult’s law for most of the composition range, except near
Mn3O4, where a two-phase region exists. In the cubic phase, the entropy of mixing of the two Rh3+ and Mn3+ ions on the octahedral site of the spinel is ideal, and the enthalpy of mixing is positive and symmetric with respect to
composition. For the formation of the spinel (sp) from component oxides with rock salt (rs) and orthorhombic (orth) structures
according to the reaction, MnO (rs) + Rh2O3 (orth) → MnRh2O4 (sp),ΔG° = -49,680 + 1.56T (±500)J mol−1 The oxygen potentials corresponding to MnO + Mn3O4 and Rh + Rh2O3 equilibria are also obtained from potentiometric measurements on galvanic cells incorporating yttria-stabilized zirconia
as the solid electrolyte. From these results, an oxygen potential diagram for the ternary system is developed. 相似文献
14.
Literature data are analyzed to give the activity coefficient (γCe) of Ce in dilute solution in Al as log10γCe = −11 356/T + 4.261 referred to liquid Ce as standard state. Measurements were made in the range of 977 to 1288 K of the equilibrium
Al (1) + CeF3 (s) = AlF3 (s) + Ce(Al) and give, by a third-law calculation, °G
o = 183 360 + 19.456T joules, and Δ
fH
298
o
of CeF3 = −1701 kJ mol−1. Values of the partition coefficient of Ce between Al and molten cryolite then give activity coefficients of CeF3 in solution. These activity coefficients decrease as the NaF/AlF3 ratio is raised, showing acid behavior of CeF3. It appears to dissolve mainly in the form of Na2CeF5. 相似文献
15.
16.
The standard free energies of formation of calcium phosphide and calcium stannide were determined by a chemical equilibration
technique, yielding the following results: 3Ca(1) + P2(g) = Ca3P2(s) ΔG° = −653,460(±7110) + 144.01(±4.98)T (J/mol)1000 °C to 1300 °C2Ca(1) + Sn(1) = Ca2Sn(s) ΔG° = −353,970(±1670) + 79.28(±1.26)T (J/mol)1000 °C to 1300 °C 1120 °C The experimental data to express the thermodynamics for removal of phosphorus and tin from
molten iron by calcium based slags by other investigators were discussed in terms of the activity co-efficients of Ca3P2 and Ca2Sn in slag melts by using the present results described above. 相似文献
17.
18.
Hiroaki Yamamoto Masao Morishita Akio Miyata Koichiro Koyama 《Metallurgical and Materials Transactions B》2006,37(4):607-613
The standard Gibbs energies of formation of Ni3B, Ni2B, o-Ni4B3(Ni0.586B0.414), m-Ni4B3(Ni0.564B0.436), NiB, and Ni3B2O6 of the Ni-B-O system have been determined by measuring electromotive forces of galvanic cells using a Y2O3-stabilized ZrO2 solid oxide electrolyte. The results are as follows:
19.
Phase relations in the pseudoternary system NiO-CaO-SiO2 at 1373 K are established. The coexisting phases are identified by X-ray diffraction and energy-dispersive X-ray analysis
of equilibrated samples. There is only one quaternary oxide CaNiSi2O6 with clinopyroxene structure. The Gibbs energy of formation
of CaNiSi2O6 is measured using a solid state galvanic cell incorporating stabilized zirconia as the solid electrolyte in the temperature
range of 1000 to 1400 K:
From the electromotive force (emf) of the cell, the Gibbs energy of formation of CaNiSi2O6 from NiO, SiO2, and CaSiO3 is obtained. To derive the Gibbs energy of formation of the quaternary oxide from component binary oxides, the free energy
of formation of CaSiO3 is determined separately using a solid state cell based on single crystal CaF2 as the electrolyte:
The results can be expressed by the following equations:
相似文献
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