The phase equilibria in the Fe–Mg–Zn–O system in the temperature range 1100–1550°C in air have be... more The phase equilibria in the Fe–Mg–Zn–O system in the temperature range 1100–1550°C in air have been experimentally studied using equilibration and quenching followed by electron probe X‐ray microanalysis. The compositions of condensed phases in equilibrium in the binary MgO–ZnO system and the ternary Fe–Mg–O system have been reported at sub‐solidus in air. Pseudo‐ternary sections of the quaternary Fe–Mg–Zn–O system at 1100, 1250 and 1400°C in air were constructed using the experimental data. The solid solution of iron oxide, MgO and ZnO in the periclase (Mg, Zn, Fe)O, spinel (Mg2+, Fe2+, Zn2+)xFe3+(2+y)O4 and zincite (Zn, Mg, Fe)O phases were found to be extensive under the conditions investigated. A continuous spinel solid solution is formed between the magnesioferrite (Mg2+, Fe2+)xFe3+(2+y)O4 and franklinite (Zn2+, Fe2+)xFe3+(2+y)O4 end‐members at 1100 and 1250°C, extending to magnetite (Fe2+)xFe3+(2+y)O4 at 1400°C in air. The compositions along the spinel boundaries were found to...
The phase equilibria in the FeO-Fe 2 O 3-ZnO system have been experimentally investigated at oxyg... more The phase equilibria in the FeO-Fe 2 O 3-ZnO system have been experimentally investigated at oxygen partial pressures between metallic iron saturation and air using a specially developed quenching technique, followed by electron probe X-ray microanalysis (EPMA) and then wet chemistry for determination of ferrous and ferric iron concentrations. Gas mixtures of H 2 , N 2 , and CO 2 or CO and CO 2 controlled the atmosphere in the furnace. The determined metal cation ratios in phases at equilibrium were used for the construction of the 1200 °C isothermal section of the Fe-Zn-O system. The univariant equilibria between the gas phase, spinel, wustite, and zincite was found to be close to pO 2 ϭ 1 и 10 Ϫ8 atm at 1200 °C. The ferric and ferrous iron concentrations in zincite and spinel at equilibrium were also determined at temperatures from 1200 °C to 1400 °C at pO 2 ϭ 1 и 10 Ϫ6 atm and at 1200 °C at pO 2 values ranging from 1 и 10 Ϫ4 to 1 и 10 Ϫ8 atm. Implications of the phase equilibria in the Fe-Zn-O system for the formation of the platelike zincite, especially important for the Imperial Smelting Process (ISP), are discussed.
The phase equilibria and liquidus temperatures in the binary SiO 2-ZnO system and in the ternary ... more The phase equilibria and liquidus temperatures in the binary SiO 2-ZnO system and in the ternary Al 2 O 3-SiO 2-ZnO system at low Al 2 O 3 concentrations have been experimentally determined using the equilibration and quenching technique followed by electron probe X-ray microanalysis. In the SiO 2-ZnO system, two binary eutectics involving the congruently melting willemite (Zn 2 SiO 4) were found at 1448 Ϯ 5 °C and 0.52 Ϯ 0.01 mole fraction ZnO and at 1502 Ϯ 5 °C and 0.71 Ϯ 0.01 mole fraction ZnO, respectively. The two ternary eutectics involving willemite previously reported in the Al 2 O 3-SiO 2-ZnO system were found to be at 1315 Ϯ 5 °C and 1425 Ϯ 25 °C, respectively. The compositions of the eutectics are 0.07, 0.52, and 0.41 and 0.05, 0.28, and 0.67 mole fraction Al 2 O 3 , SiO 2 , and ZnO, respectively. The results of the present investigation are significantly different from the results of previous studies.
The phase equilibria in the Al-Fe-Zn-O system in the range 1250 °C to 1695 °C in air have been ex... more The phase equilibria in the Al-Fe-Zn-O system in the range 1250 °C to 1695 °C in air have been experimentally studied using equilibration and quenching techniques followed by electron probe X-ray microanalysis. The phase diagram of the binary Al 2 O 3-ZnO system and isothermal sections of the Al 2 O 3-"Fe 2 O 3 "-ZnO system at 1250 °C, 1400 °C, and 1550 °C have been constructed and reported for the first time. The extents of solid solutions in the corundum (Al,Fe) 2 O 3 , hematite (Fe,Al) 2 O 3 , Al 2 O 3 *Fe 2 O 3 phase (Al,Fe) 2 O 3 , spinel (Al,Fe,Zn)O 4 , and zincite (Al,Zn,Fe)O primary phase fields have been measured. Corundum, hematite, and Al 2 O 3 *Fe 2 O 3 phases dissolve less than 1 mol pct zinc oxide. The limiting compositions of Al 2 O 3 *Fe 2 O 3 phase measured in this study at 1400 °C are slightly nonstoichiometric, containing more Al 2 O 3 then previously reported. Spinel forms an extensive solid solution in the Al 2 O 3-"Fe 2 O 3 "-ZnO system in air with increasing temperature. Zincite was found to dissolve up to 7 mole pct of aluminum in the presence of iron at 1550 °C in air. A meta-stable Al 2 O 3-rich phase of the approximate composition Al 8 FeZnO 14ϩx was observed at all of the conditions investigated. Aluminum dissolved in the zincite in the presence of iron appears to suppress the transformation from a round to platelike morphology.
Single phase (Zn,Fe)1−x O zincite solid solution samples have been prepared by high temperature e... more Single phase (Zn,Fe)1−x O zincite solid solution samples have been prepared by high temperature equilibration in air and in reducing atmospheres, followed by quenching to room temperature. The Fe2+/Fe3+ concentrations in the samples have been determined using wet chemical and XPS techniques. Iron is found to be present in zincite predominantly in the form of Fe3+ ions. The transition from
Abstract The phase equilibria in the ZnO-rich part in the Al-Fe-Zn-O system in the range of 1200 ... more Abstract The phase equilibria in the ZnO-rich part in the Al-Fe-Zn-O system in the range of 1200 to 1400 °C in oxygen partial pressure (pO2) 1*10−6 atm and at 1200 °C in pO2=1*10−8 atm have been experimentally studied. Equilibration and quenching techniques followed by electron probe X-ray microanalysis were used in the study. Sections of the Al2O3-Fe2O3-FeO-ZnO system at 1200, 1300 and 1400 °C in pO2=1*10−6 atm and at 1200 °C in pO2=1*10−8 atm have been constructed and reported for the first time. The extents of solid solution in the spinel (Al,Fe,Zn)O4 and zincite (Zn,Al,Fe)O primary phase fields have been measured. Spinel forms an extensive solid solution in the Al-Fe-Zn-O system. The ZnO-rich boundary of the spinel is close to the ZnAl2O4-ZnFe2O4 join at the more oxidizing conditions, approaching the ZnAl2O4-FeAl2O4 join at more reducing conditions. The zincite solid solution dissolves mainly iron but also small concentrations of aluminum at elevated temperature or reduced pO2. The observed zincite morphology in samples after equilibration supports the previously reported relations between the formation of equiaxed and plate-like zincite and phase equilibria. On a étudié expérimentalement les équilibres de phase de la partie riche en ZnO du système Al–Fe–Zn–O dans la gamme de 1200 à 1400 °C sous une pression partielle d’oxygène (pO2) de 1*10−6 atm et à 1200 °C avec pO2=1*10−8 atm. Dans cette étude, on a utilisé des techniques d’équilibration et de trempe suivies par l’analyse des rayons X par microsonde électronique. On a construit et rapporté pour la première fois des sections du système Al2O3-Fe2O3-FeO-ZnO à 1200, 1300 et 1400 °C avec pO2=1*10−6 atm et à 1200 °C avec pO2=1*10−8 atm. On a mesuré le domaine de solution solide des champs de phase primaires du spinelle (Al,Fe,Zn)O4 et de la zincite (Zn,Al,Fe)O. Le spinelle forme une solution solide étendue dans le système Al–Fe–Zn–O. La limite riche en ZnO du spinelle se trouve près de la borne ZnAl2O4-ZnFe2O4 aux conditions plus oxydantes et s’approche de la borne ZnAl2O4-FeAl2O4 aux conditions plus réductrices. La solution solide de zincite dissout principalement le fer mais également de petites concentrations d’aluminium aux températures élevées ou avec pO2 réduite. La morphologie de la zincite, observée dans les échantillons après l’équilibration, supporte les relations rapportées antérieurement entre la formation de zincite isométrique et lamellaire et les équilibres de phase.
A method is described for the determination of nickel at sub-ng g 21 concentration levels. Electr... more A method is described for the determination of nickel at sub-ng g 21 concentration levels. Electrochemical reduction of nickel in a flow-through electrolytic cell is followed by the generation and transfer of volatile Ni(CO) 4 to a graphite furnace where it is decomposed and trapped. Nickel is atomised and determined by atomic absorption spectrometry. The system has an overall efficiency of about 70% and gives a detection limit of 87 ng l 21 , based on a 1.0 ml sample volume. Limitations of the method are described; changes of the working electrode surface are shown to have a major influence on the reliability and sensitivity of the method. A method based on the chemical reduction of nickel using NaBH 4 was used for comparison. The methods were validated by the determination of nickel in a water reference material.
The phase equilibria in the Fe–Mg–Zn–O system in the temperature range 1100–1550°C in air have be... more The phase equilibria in the Fe–Mg–Zn–O system in the temperature range 1100–1550°C in air have been experimentally studied using equilibration and quenching followed by electron probe X‐ray microanalysis. The compositions of condensed phases in equilibrium in the binary MgO–ZnO system and the ternary Fe–Mg–O system have been reported at sub‐solidus in air. Pseudo‐ternary sections of the quaternary Fe–Mg–Zn–O system at 1100, 1250 and 1400°C in air were constructed using the experimental data. The solid solution of iron oxide, MgO and ZnO in the periclase (Mg, Zn, Fe)O, spinel (Mg2+, Fe2+, Zn2+)xFe3+(2+y)O4 and zincite (Zn, Mg, Fe)O phases were found to be extensive under the conditions investigated. A continuous spinel solid solution is formed between the magnesioferrite (Mg2+, Fe2+)xFe3+(2+y)O4 and franklinite (Zn2+, Fe2+)xFe3+(2+y)O4 end‐members at 1100 and 1250°C, extending to magnetite (Fe2+)xFe3+(2+y)O4 at 1400°C in air. The compositions along the spinel boundaries were found to...
The phase equilibria in the FeO-Fe 2 O 3-ZnO system have been experimentally investigated at oxyg... more The phase equilibria in the FeO-Fe 2 O 3-ZnO system have been experimentally investigated at oxygen partial pressures between metallic iron saturation and air using a specially developed quenching technique, followed by electron probe X-ray microanalysis (EPMA) and then wet chemistry for determination of ferrous and ferric iron concentrations. Gas mixtures of H 2 , N 2 , and CO 2 or CO and CO 2 controlled the atmosphere in the furnace. The determined metal cation ratios in phases at equilibrium were used for the construction of the 1200 °C isothermal section of the Fe-Zn-O system. The univariant equilibria between the gas phase, spinel, wustite, and zincite was found to be close to pO 2 ϭ 1 и 10 Ϫ8 atm at 1200 °C. The ferric and ferrous iron concentrations in zincite and spinel at equilibrium were also determined at temperatures from 1200 °C to 1400 °C at pO 2 ϭ 1 и 10 Ϫ6 atm and at 1200 °C at pO 2 values ranging from 1 и 10 Ϫ4 to 1 и 10 Ϫ8 atm. Implications of the phase equilibria in the Fe-Zn-O system for the formation of the platelike zincite, especially important for the Imperial Smelting Process (ISP), are discussed.
The phase equilibria and liquidus temperatures in the binary SiO 2-ZnO system and in the ternary ... more The phase equilibria and liquidus temperatures in the binary SiO 2-ZnO system and in the ternary Al 2 O 3-SiO 2-ZnO system at low Al 2 O 3 concentrations have been experimentally determined using the equilibration and quenching technique followed by electron probe X-ray microanalysis. In the SiO 2-ZnO system, two binary eutectics involving the congruently melting willemite (Zn 2 SiO 4) were found at 1448 Ϯ 5 °C and 0.52 Ϯ 0.01 mole fraction ZnO and at 1502 Ϯ 5 °C and 0.71 Ϯ 0.01 mole fraction ZnO, respectively. The two ternary eutectics involving willemite previously reported in the Al 2 O 3-SiO 2-ZnO system were found to be at 1315 Ϯ 5 °C and 1425 Ϯ 25 °C, respectively. The compositions of the eutectics are 0.07, 0.52, and 0.41 and 0.05, 0.28, and 0.67 mole fraction Al 2 O 3 , SiO 2 , and ZnO, respectively. The results of the present investigation are significantly different from the results of previous studies.
The phase equilibria in the Al-Fe-Zn-O system in the range 1250 °C to 1695 °C in air have been ex... more The phase equilibria in the Al-Fe-Zn-O system in the range 1250 °C to 1695 °C in air have been experimentally studied using equilibration and quenching techniques followed by electron probe X-ray microanalysis. The phase diagram of the binary Al 2 O 3-ZnO system and isothermal sections of the Al 2 O 3-"Fe 2 O 3 "-ZnO system at 1250 °C, 1400 °C, and 1550 °C have been constructed and reported for the first time. The extents of solid solutions in the corundum (Al,Fe) 2 O 3 , hematite (Fe,Al) 2 O 3 , Al 2 O 3 *Fe 2 O 3 phase (Al,Fe) 2 O 3 , spinel (Al,Fe,Zn)O 4 , and zincite (Al,Zn,Fe)O primary phase fields have been measured. Corundum, hematite, and Al 2 O 3 *Fe 2 O 3 phases dissolve less than 1 mol pct zinc oxide. The limiting compositions of Al 2 O 3 *Fe 2 O 3 phase measured in this study at 1400 °C are slightly nonstoichiometric, containing more Al 2 O 3 then previously reported. Spinel forms an extensive solid solution in the Al 2 O 3-"Fe 2 O 3 "-ZnO system in air with increasing temperature. Zincite was found to dissolve up to 7 mole pct of aluminum in the presence of iron at 1550 °C in air. A meta-stable Al 2 O 3-rich phase of the approximate composition Al 8 FeZnO 14ϩx was observed at all of the conditions investigated. Aluminum dissolved in the zincite in the presence of iron appears to suppress the transformation from a round to platelike morphology.
Single phase (Zn,Fe)1−x O zincite solid solution samples have been prepared by high temperature e... more Single phase (Zn,Fe)1−x O zincite solid solution samples have been prepared by high temperature equilibration in air and in reducing atmospheres, followed by quenching to room temperature. The Fe2+/Fe3+ concentrations in the samples have been determined using wet chemical and XPS techniques. Iron is found to be present in zincite predominantly in the form of Fe3+ ions. The transition from
Abstract The phase equilibria in the ZnO-rich part in the Al-Fe-Zn-O system in the range of 1200 ... more Abstract The phase equilibria in the ZnO-rich part in the Al-Fe-Zn-O system in the range of 1200 to 1400 °C in oxygen partial pressure (pO2) 1*10−6 atm and at 1200 °C in pO2=1*10−8 atm have been experimentally studied. Equilibration and quenching techniques followed by electron probe X-ray microanalysis were used in the study. Sections of the Al2O3-Fe2O3-FeO-ZnO system at 1200, 1300 and 1400 °C in pO2=1*10−6 atm and at 1200 °C in pO2=1*10−8 atm have been constructed and reported for the first time. The extents of solid solution in the spinel (Al,Fe,Zn)O4 and zincite (Zn,Al,Fe)O primary phase fields have been measured. Spinel forms an extensive solid solution in the Al-Fe-Zn-O system. The ZnO-rich boundary of the spinel is close to the ZnAl2O4-ZnFe2O4 join at the more oxidizing conditions, approaching the ZnAl2O4-FeAl2O4 join at more reducing conditions. The zincite solid solution dissolves mainly iron but also small concentrations of aluminum at elevated temperature or reduced pO2. The observed zincite morphology in samples after equilibration supports the previously reported relations between the formation of equiaxed and plate-like zincite and phase equilibria. On a étudié expérimentalement les équilibres de phase de la partie riche en ZnO du système Al–Fe–Zn–O dans la gamme de 1200 à 1400 °C sous une pression partielle d’oxygène (pO2) de 1*10−6 atm et à 1200 °C avec pO2=1*10−8 atm. Dans cette étude, on a utilisé des techniques d’équilibration et de trempe suivies par l’analyse des rayons X par microsonde électronique. On a construit et rapporté pour la première fois des sections du système Al2O3-Fe2O3-FeO-ZnO à 1200, 1300 et 1400 °C avec pO2=1*10−6 atm et à 1200 °C avec pO2=1*10−8 atm. On a mesuré le domaine de solution solide des champs de phase primaires du spinelle (Al,Fe,Zn)O4 et de la zincite (Zn,Al,Fe)O. Le spinelle forme une solution solide étendue dans le système Al–Fe–Zn–O. La limite riche en ZnO du spinelle se trouve près de la borne ZnAl2O4-ZnFe2O4 aux conditions plus oxydantes et s’approche de la borne ZnAl2O4-FeAl2O4 aux conditions plus réductrices. La solution solide de zincite dissout principalement le fer mais également de petites concentrations d’aluminium aux températures élevées ou avec pO2 réduite. La morphologie de la zincite, observée dans les échantillons après l’équilibration, supporte les relations rapportées antérieurement entre la formation de zincite isométrique et lamellaire et les équilibres de phase.
A method is described for the determination of nickel at sub-ng g 21 concentration levels. Electr... more A method is described for the determination of nickel at sub-ng g 21 concentration levels. Electrochemical reduction of nickel in a flow-through electrolytic cell is followed by the generation and transfer of volatile Ni(CO) 4 to a graphite furnace where it is decomposed and trapped. Nickel is atomised and determined by atomic absorption spectrometry. The system has an overall efficiency of about 70% and gives a detection limit of 87 ng l 21 , based on a 1.0 ml sample volume. Limitations of the method are described; changes of the working electrode surface are shown to have a major influence on the reliability and sensitivity of the method. A method based on the chemical reduction of nickel using NaBH 4 was used for comparison. The methods were validated by the determination of nickel in a water reference material.
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