ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04187.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04188.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Phase equilibrium data for the system FeO– Fe2O3–Al2O3–SiO2are used to evaluate the attack of iron oxides on alumina‐silica refractories under various idealized conditions which approach those occurring in practice. The extent of attack and the nature of the reactions at various levels of O2pressure are di

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04189.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04190.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Phase relations in the system CaO–chromium oxide–SiO2were determined (a) in equilibrium with metallic chromium and (b) at various oxygen pressures in the range of ∼ 10−10to 10−13atm. Two ternary phases occur on the liquidus surface in equilibrium with metallic chromium, viz, the garnet Ca3Cr2Si3O12(uvarovite), and CaCrSi4O10of the gillespite‐type structure and in which essentially all the chromium is present in the divalent state (Cr2+). Furthermore, a previously reported binary calcium chromite phase “X” of approximate composition (Ca0.4Cr0.6)Cr2O4is stable also on the liquidus surface of the present system. The lowest liquidus and solidus temperatures in the system under these conditions (contact with metallic chromium) are significantly lower (by 100° to 200°C, depending on CaO/SiO2ratios of the melts) than those for the same system in air. Furthermore, there is considerable solid solution of chromium oxide in lime (CaO) and the various crystalline calcium silicates (pseudowollastonite, CaSiO3; rankinite, Ca3Si2O7; dicalcium silicate, Ca2SiO4; tricalcium silicate, Ca3SiO5), presumably by partial substitution of Cr2+for Ca2+toward hypothetical chromium analogs of each CaO‐containing phase, particularly in lime and Ca2SiO4. At the somewhat higher oxygen pressures imposed by the CO2─H2gas mixtures of CO2/H2ratios of 1/24 and 1/8.1, the phases containing most of the chromium in the divalent state (CaCrSi4O10and (Ca0.4Cr0.6)Cr2O4) do not appear on the liquidus surface, the primary phase area of garnet (uvarovite) decreases, the lowest liquidus and solidus temperatures increase noticeably (−50° to 100°C), and the amounts of chromium substituting in lime and the various crystalline calcium silicate phases (CaSiO3, Ca3Si2O7, Ca2SiO4, and Ca3SiO5) decrease considerably from those observed for the system in equilibrium with metallic chromium. Combination of the data obtained under these reducing conditions with those previously reported for the system under more oxidizing conditions permits derivation of the general features of phase relations in the quaternary

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04191.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Liquidus and solidus phase relations have been determined for the system NiO‐iron oxide–SiO2in air and in CO2. In both cases the system is simple in that it contains only three primary crystalline phases: spinel (Fe3O4–NiFe2O3solid solution), oxide (“FeO”–NiO solid solution) and SiO2, either tridymite or cristobalite. There is only one liquidus invariant point at which the above crystalline phases coexist with liquid (and the gas phase). In air, the invariant point (a eutectic) is at 1524°C, and a temperature maximum is present along the spinel–silica liquidus boundary curve at 1540°C. In CO2, the silica + spinel + oxide + liquid invariant temperature is considerably lower: 1433°C. Combination of these data with those obtained previously for the same system under strongly reducing conditions (CO2–CO gas mixtures of ratios only slightly above those of equilibrium coexistence of the oxide phases with Fe–Ni alloy) makes it possible to draw the main features of phase relations in the quaternary system FeO–NiO–Fe2O3–SiO2. This system also is relatively simple, in that only five crystalline phases are present in equilibrium with liquids, viz, silica (cristobalite or tridymite), olivine (Fe2SiO4‐Ni2SiO4solid solution), spinel (Fe3O4‐NiFe2O4solid solution), hematite (Fe2O3), and oxide (“FeO”–NiO solid solution). There is only one quaternary liquidus invariant point in the system, characterized by the equilibrium coexistence of silica, olivine, spinel, oxide, and liquid, at a temperature of ∼ 1410°C and an oxyge

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04192.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Liquidus and solidus phase relations have been determined for the system iron oxide–NiO–SiO2under strongly reducing conditions obtained by using CO2–CO gas mixtures in controlled proportions. The phase relations were determined with the well‐known quenching method: oxide mixtures were equilibrated in vertical tube resistance furnaces, followed by quenching to room temperature and identification of phases with transmitted‐ and reflected‐light microscopy and X‐ray diffraction. Three crystalline phases are present on the liquidus surface: olivine (Fe2SiO4–Ni2SiO4solid solutions), oxide (“FeO”–NiO solid solutions), and silica (tridymite or cristobalite, depending on temperature). The “ternary peritectic” point where these three phases coexist with liquid is at 1571°C, with a liquid composition of approximately 19 wt%“F

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04193.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Phase relations in the system NiO–TiO2have been determined by heating oxide mixtures in air at selected temperatures in the range 1300° to 1750°C for sufficient periods of time to attain equilibrium, followed by rapid quenching to room temperature. The phases have been characterized by optical microscopy, X‐ray diffraction, and electron microprobe analysis. The most striking feature is the presence, above 1430°C, of a spinel‐type phase that decomposes below this temperature to a mixture of remnant spinel, NiO of periclase‐type structure, and NiTiO3of ilmenite‐type structure. There are two peritectic points in the system, one at 1730°C where spinel, NiO, and liquid coexist in equilibrium, and one at 1610°C where spinel, NiTiO3, and liquid are the coexisting phases. A eutectic is present at 1570°C, with NiTiO3, rutile, and liquid coexisting in equilibrium. Rapid transformation of the spinel phase, even during rapid quenching, imposes uncertainties on the interpretation of the experimental data obtained, but the equilibrium‐phase relations are deduced essentially as shown in the phase diagram presented. Results of a small number of calculated activities of NiO in oxide‐phase assemblages involving the spinel phase at high temperatures (∼1500°C) lend support to the interpretation of the phase relations as p

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04194.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Activity–composition relations in Pt–Cr and Pt–V alloys at 1500°C were determined from equilibration of these alloys with Cr2O3and V2O3, respectively, in Co2–H2atmospheres of known oxygen partial pressures, followed by quenching to room temperature and microprobe analyses of the quenched alloys. The activities of Cr and V were calculated from known standard free energies of formation of Cr2O3and V2O3from the respective elements, and the oxygen pressures were calculated from the C–H–O equilibrium in the gas phase. Both alloy systems show strong negative deviations from Raoult

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04195.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The solubility and activity–composition relations of chromium oxide in melts of the systems CaO–CrOx–SiO2and CaO–Al2O3–CrOx–SiO2have been determined at 1500°C by equilibrating melts with Pt–Cr alloys at known oxygen pressures. It is shown that the increase in the concentration of divalent chromium ions, as the oxygen pressure and the basicity of melt decrease, results in a dramatic increase in the solubility of chromium oxide in the liquid phase. An increase in the Al2O3content of the melt leads to a decrease in the solubility of chromium oxide over the whole composition range studied. The activity coefficient of CrO has been found to increase with increasing melt basicity and decreasing oxygen pressure whereas the activity coefficient of CrO1.5decreases sharply with increasing melt basicity for siliceous melts but levels off at a basicity ratio (wt% CaO/wt% SiO2) of about 0.7. An increase in the Al2O3content of the melts results in an increase in the activity coef

ISSN:0002-7820    

DOI:10.1111/j.1151-2916.1992.tb04196.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY