Primary Phase Field Research Articles

Subsolidus and melting phase relationships of the PbO xCaOCuO system in air

Phase equilibrium studies of the PbO x CaOCuO system were conducted from the subsolidus at 770°C to the melting of Ca 2CuO 3 at 1034°C. No ternary oxide compounds were found. Twelve isothermal sections and a liquidus diagram outlining the primary phase fields are presented. At 770°C, in the subsolidus, Ca 2PbO 4 was found to be in equilibrium with Ca 2CuO 3, CaO, PbO x and CuO. The eutectic melting temperature is ≈ 780°C, and the eutectic melting reaction is: PbO + Ca 2PbO 4 + CuO → liquid. Two additional ternary melting reactions were characterized. Above 1034°C, the only solid compounds remaining are CaO and CuO.

Subsolidus and melting study of the Bi2O3-PbOx-CuO system in air

Abstract The subsolidus and liquidus equilibria of the 1 2 Bi 2 O 3 -PbO x -CuO system were investigated in air by quenching, X-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopy. No ternary compounds were found in this system. A series of isothermal sections from 590 °C to 840 °C is presented. At ≈ 590 °C, a total of six subsolidus equilibrium regions were found as a result of tie-line connections from Bi 2 CuO 4 to (Pb, Bi)O x , Bi 12 PbO 20 , Bi 6 Pb 2 O 11 , βss (a solid solution midway on the PbO x 1 2 Bi 2 O 3 join) and Pb 3 Bi 2 O 6 . The eutectic melting of the system occurred at ≈ 610 °C in the region bounded by βss, Bi 2 CuO 4 and (Pb, Bi)O x . The eutectic melt composition was determined to be at Bi:Pb:Cu = 51.2: 45.2: 3.6. As the temperature increased, the liquid region expanded and tie-line connections between Bi 2 CuO 4 and the Pb-containing binary oxides were sequentially eliminated. By about 850 °C, all tie-lines connecting the binary oxides had vanished due to the incursion of liquid, which extended to the Bi 2 O 3 corner as well. At this temperature, only two sets of tie-line remained, those connecting PbO and CuO to liquid. A liquidus diagram showing the primary phase fields is discussed.

Phase equilibrium relationships in the system Al 2O 3-TiO 2-MnO, relevant to the low-temperature sintering of alumina

A great deal of research work has been devoted to lowering the sintering temperature of ceramic powders of varied nature, to fulfil a variety of purposes. Both experimentation and theory show that the sintering temperature of alumina can be lowered to 1400 °C and below by using small particle sizes and certain additives like TiO 2 and/or MnO. The general idea is that sintering is aided by the development of a liquid phase at this low temperature, due to the presence of the additives. However, there is no phase diagram available to throw light on this matter. For this reason, the present work was aimed at investigating the phase equilibrium relationships in the ternary, non-condensed system Al 2O 3-TiO 2-MnO, in air. Selected compositions in this system were prepared from reagent-grade oxides, uniaxially pressed into 6 mm cylindrical pellets, fired at temperatures between 1000 and 1650 °C for 2 to 22 h, water-quenched, and observed by X-ray diffraction and scanning electron microscopy, the composition of some of the phases identified being evaluated by energy-dispersive spectroscopy. These experiments led to the definition of the compatibility triangles and a tentative location of the boundary curves between primary phase fields is presented.

Nepheline Precipitation in High-Level Waste Glasses : Compositional Effects and Impact on the Waste Form Acceptability

ABSTRACTThe impact of crystalline phase precipitation in glass during canister cooling on chemical durability of the waste form limits waste loading in glass, especially for vitrification of certain high-level waste (HLW) streams rich in Na2O and Al2O3. This study investigates compositional effects on nepheline precipitation in simulated Hanford HLW glasses during canister centerline cooling (CCC) heat treatment. It has been demonstrated that the nepheline primary phase field defined by the Na2O-Al2O3-SiO2 ternary system can be used as an indicator for screening HLW glass compositions that are prone to nepheline formation. Based on the CCC results, the component effects on increasing nepheline precipitation can be approximately ranked as Al2O3 > Na2O > Li2O ≈ K2O ≈ Fe2O3 > CaO > SiC2. The presence of nepheline in glass is usually detrimental to chemical durability. Using x-ray diffraction data in conjunction with a mass balance and a second-order mixture model for 7-day product consistency test (PCT) normalized B release, the effect of glass crystallization on glass durability can be predicted with an uncertainty less than 50% if the residual glass composition is within the range of the PCT model.

Experimental Investigation of High Temperature Phase Equilibria in the Nb-Al-Ti System

High temperature phase equilibria of the ternary system Nb-Al-Ti were investigated in cast and annealed alloys by SEM, X-ray diffraction, EPMA and TEM. A modified liquidus projection and an isothermal section at 1200°C are presented. The liquidus projection has been modified with regard to the extent of the γ and β primary phase fields. In the isothermal section at 1200°C the ternary T2 phase does not appear since it has been shown that this phase is not stable at this temperature

Formation of belite clusters from quartz grains in portland cement clinker

The conversion process of quartz grains into belite clusters in portland cement clinker has been followed under isothermal heating conditions at 1400 °C. On heating, quartz grains are surrounded by layers consisting of belite and liquid, which continue to grow thick with the progress of conversion (outer layers of belite). The conversion process has been divided into three stages considering the chemical composition of the liquid phase formed in each stage. In the first stage are formed two kinds of liquids the compositions of which lie across the primary phase field of wollastonite from each other. The belite crystals precipitated constitute thin, dense layers (inner layers of belite). At the beginning of the second stage, the inside of the belite layers is completely converted into a liquid without quartz and wollastonite. The inner layers extend inward and grow thick; the impurity concentration is lowest for this part of the belite layers. With further progress of diffusion, belite crystals nucleate and grow independently inside the layers. The composition of the coexisting liquid, rich in alkalies, moves on the primary phase field of C 2S toward that of C 3A. In the third stage the conversion is completed and the liquid phase, enriched with Al 2O 3 and Fe 2O 3, is similar in composition to the interstitial liquid in portland cement clinker. The belite crystals, especially those of the inner layers, undergo grain growth with an increase in impurity content with duration of heating. Three kinds of belite crystals different in origin, texture and composition are thus distinguishable in the belite clusters.

Crystallization studies of the β (Mg2Pb) phase and its phase boundaries in the Pb-Mg-Bi system

A peritectic reaction between Mg bismuthide and Mg plumbide changes from an even to an odd reaction at 310 °C (0.14 wt pct Bi and 4 wt pct Mg) owing to the incorporation of 1.6 wt pct Bi into Mg plumbide; this value was calculated from material balances of equilibrium studies of this reaction and confirmed by direct analysis of crystals using a “Cameca Microbeam” electroprobe microanalyzer. A model is presented in which an atom of Pb in the unit cell, 46 Mg2Pb Mg2Pb5, is replaced by an atom of Bi which gives a concentration of 1.63 to 1.71 wt pct Bi depending on the actual species of Mg plumbide present. The phase boundary for double saturation with Pb and Mg plumbide, established from the data of equilibrium tests, shows a minimum temperature of 251.8 °C at 0.008 wt pct Bi and 2.2 wt pct Mg. Alloys in the primary Pb phase field adjacent to this boundary show undercooling to less than 248.5 °C followed by one or two sharp temperature increases to 250.5 °C, with the initiation of the removal of Bi when double saturation occurs giving a final liquid phase containing less than 0.001 wt pct Bi. Crystallization paths for alloys in the Mg plumbide phase field show a catatectic reaction and polymorphic transformations in the intermetallic compound. The removal of Bi is dependent on the concentration of Bi and Mg in the initial alloy. In systems containing sufficient Mg, a final alloy containing less than 0.001 wt pct Bi can be produced, and these conditions have been used as the starting point for the development of a process for the removal of Bi from Pb. Finally, the crystallization paths show there is a change in the thermal properties of the liquid alloy at 0.008 wt pct Bi which is independent of the temperature and concentration of Mg, and further work is required to resolve this finding.

Liquidus projection surface and isothermal section at 1000 °C of the Co-Pr-B (Co-rich) ternary phase diagram*

The liquidus projection surface and the isothermal section at 1000 °C of the Co-Pr-B (Co-rich) ternary phase diagram have been determined. The binary and ternary intermetallics (Pr2Co17, PrCo5, Pr5Co19, Pr2Co7, PrCo3, PrCo2, C03B, C02B, CoB, P2Co14B, PrCo4B, PrCo12B, Pr3Co11B4, and Pr2Co7B3) that were examined in the Co-rich portion of the Co-Pr-B ternary phase diagram were found to be true line compounds (no detectable solid solubility). The primary solidification phase field of the Pr2Co14B intermetallic compound shares boundaries with the primary solidification phase fields of αCo, Pr2Co17, PrCo5, P1-C04B, and PrCo12B6 intermetallics. There are eight reactions associated with the Pr2Co14B intermetallic compound: two ternary eutectic reactions (E1 = Liquid ↔ Pr2Co14B + PrCo12B6 + PrCo4B and E2 = Liquid ↔ Pr2Co14B + PrCo12B6 + αCo), two pseudobinary eutectic reactions (e3 = Liquid ↔ Pr2Co14B + PrCo4B and e4 = Liquid ↔ Pr2Co14B + PrCo12B6), three ternary quasi-peritectic reactions (P1 = Pr2Co17 + Liquid ↔ Pr2Co14B + αCo, P2 = Pr2Co17 + Liquid ↔ PrCo5 + Pr2Co14B, and P3 = Pr2Co14B + Liquid ↔ PrCo4B + PrCo5), and one pseudobinary peritectic reaction (p8 = Pr2Co17 + Liquid ↔ Pr2Co14B). The composition of the magnetically important Pr2Co14B intermetallic falls inside the primary solidification phase field of the Pr2Co17 intermetallic. The reaction through which the Pr2Co14B is produced is therefore the pseudobinary peritectic reaction Pr2Co17 + Liquid ↔ P2Co14B. The PrCo12B6 and PrCo4B compounds are found to form congruently from the melt At the temperature of 1000 °C and depending on the alloy composition, the P2Co14B intermetallic can be found in solid-state thermodynamic equilibrium with one or two of the following phases: αCo, Pr2Co17, PrCo5, PrCo4B, and PrCo12B6. The obtained information about the Co-Pr-B phase diagram can be used to explain correctly all the phases present in the P2Co14B-based permanent magnets. The present work also emphasizes the extreme importance and usefulness of thermomagnetic measurements as an aid in the determination of phase diagrams that involve ferromagnetic phases.

Thermodynamic calculation of phase equilibria in the CaF2–SiO2–CaO system

Thermodynamic properties of intermediate phases and melts of the system CaF2–SiO2–CaO, found experimentally, have been applied to computation of phase equilibria. Four intermediate phases CaO·SiO2, 3CaO·SiO2, 3CaO·2SiO2, 2CaO·SiO2 and two deep eutectics at T= 1717 K, XSiO2= 0.635 and T= 1723 K, XSiO2= 0.445 situated on either side of CaO·SiO2 exist in the binary system CaO–SiO2. The CaF2–CaO binary system has a simple eutectic diagram with the eutectic point at T = 1631 K and XCaO= 0.198. Isotherms of the CaF2–SiO2-CaO phase diagrams were calculated at 1473, 1573, 1700, 1773 and 1823 K. Four pseudobinary joins in the CaF2–SiO2–CaO phase diagram were also computed. A large region of liquid immiscibility is predicted to exist in the system and confirmed experimentally. One liquid phase is composed of almost pure CaF2 with additions of several mol% CaO and SiO2, and the other contains 56–70 mol% CaF2. There are five invariant points in the CaF2–SiO2–CaO system, four of them being ternary eutectics and one being a ternary peritectic. The primary phase fields of crystallization of all the phases are elongated toward the CaF2 apex; those of the end-member components are the widest, and those of the compounds 3CaO·SiO2 and 3CaO·2SiO2 are the narrowest. Experiments were carried out to confirm the reliability of the locations of the computed phase equilibria boundaries.

Liquidus phase relationships on the join anorthiteforsterite-quartz at 20 kbar with applications to basalt petrogenesis and igneous sapphirine

Liquidus phase relationships determined on the join anorthite-forsterite-quartz at 20 kbar show primary phase fields for quartz (q), forsterite (fo), enstatite (en), spinel (sp), anorthite (an), sapphirine (sa), and corundum (cor). Increasing pressure causes (1) thefo andan primary phase fields to contract, (2) theen, q, andcor fields to expand, (3) thefo-en boundary line to move away from the Q apex, (4) theen-q boundary line to move also away from the Q apex but by a smaller amount, and (5) a primary phase field forsa to appear at a pressure between 10 and 20 kbar. Seven liquidus piercing points at 20 kbar have been located as follows: Crystalline phases Liquid composition (wt %) Temperature (°C) sp+sa+cor An81Fo17Q2 1575 fo+en+sp An52Fo39Q9 1540 en+sp+sa An59Fo31Q10 1490 sa+an+cor An70Fo15Q15 1430 an+q+cor An66Fo7Q27 1410 sa+an+en An62Fo18Q20 1400 an+en+q An59Fo15Q26 1380 It is concluded that (1) the shift of thefo-en boundary line away from the quartz apex with pressure confirms many other studies showing that melts generated from peridotite source rocks decrease in silica content as pressure increases; (2) even though plagioclase is not a stable phase in peridotite source rocks at pressures above about 10 kbar, it can crystallize from mafic magmas at pressures at least up to 20 kbar; (3) sapphirine crystallizes from mafic magmas at high pressures and may be important in the construction of petrogenetic models based on trace element considerations.

Elevation of potassium content of basaltic magma by fractional crystallization: the effect of pressure

A wide range of natural quartz-normative liquids crystallizes olivine at low pressure. Addition of K2O to the system results in expansion of the olivine primary phase field and replacement of pigeonite (stable in the K-free system) by hypersthene. Some variation in phase relations results from depression of crystallization temperature towards the temperature at which pigeonite reacts to form augite and hypersthene because of addition of K2O. Another important influence on phase relations results from cation interactions in the liquid related to addition of K2O. Studies of crystallization behavior of materials similar in most elements except K2O show that K2O content markedly alters crystallization behavior for more siliceous liquids but appears to have less effect on liquids with lower SiO2 contents. Low-Ca pyroxenes melt congruently at P>≈5 kbar, so anhydrous liquids coprecipitate olivine, plagioclase, and two pyroxenes. Addition of K2O to the liquid has the same effect as at 1 atm. Hypersthene replaces pigeonite as the Low-Ca pyroxene crystallization from liquids with >≈1.5% K2O and the olivine primary phase field grows at the expense of those of pyroxenes and plagioclase. At 10 kbar, olivine may develop a reaction relationship with liquids containing >≈6% K2O. At 15 kbar, however, liquids evolve to a pseudoeutectic involving alkali feldspar. The systematic variation in phase relations has important consequences for magmatic evolution in different environments. Dry mafic liquids at shallow levels in oceanic areas can crystallize olivine until the liquid is very evolved, resulting in extreme SiO2-enrichment besides enrichment in K2O, and producing potassic dacites. Olivine coexists with liquids with up to 54% SiO2 if K2O=0.6% (Grove and Baker 1984) but as much as 63% SiO2 if K2O≈3.5% (Ussler and Glazner 1989). Magmas rising beneath light continental crust may pond at the Moho and evolve to low-density liquids that can rise to the surface. Coprecipitation of olivine, plagioclase, augite, and a low-Ca pyroxene, produces enrichment in K2O with only slight enrichment in SiO2. This is terminated, at pressures of 6 to, possibly, 12 kbar, by development of a reaction relationship of olivine and liquid that progresses to higher K2O contents with pressure. At pressures as high as 15 kbar, the reaction relation may not develop and only crystallization of alkali feldspar suppresses K2O-enrichment. Any magmatic H2O or crustal contamination may modify phase relations. The phase relations do, however, suggest that variation in K2O:SiO2 of evolved volcanic rocks is related to crustal thickness rather than to variation in the chemical compositions of primary magmas.

フェロニッケルスラグの冷却条件と組織に関する研究 アルカリ骨材反応防止のための冷却条件

The effect of the cooling condition of ferro nickel slag melts on retained glass and crystalline phases (enstatite, forsterite, cristobalite) has been discussed.Commercial ferro nickel slags were classified into two groups; one (slag A, B, C) was located the composition of the olivine (forsterite) primary phase field and the other (slag D)was the eutectic field between pyroxene (enstatite) and olivine in the FeO-MgO-SiO2system.The critical cooling rates for glass forming determined directly from the CCT diagrams were in the range of 120 to 20°C/sec and those were dependent on the content of SiO2as a network former. Forsterite, enstatite, and ristobalite crystallized from all of the ferro nickel slags in that order with decreasing the continuous cooling rate. The first crystalline phase at isothermal heat treatment from the slag A, B, C was forsterite, while those of the slag D were forsterite and enstatite. Enstatite and cristobalite gradually crystallized with the holding time at this treatment.In addition, the possibility of alkali-aggregate reaction were evaluated by the chemical test, ASTMC289 for the as-received and the heat-treated slags.

The chemistry and mineralogy of some granulated and pelletized blastfurnace slags

AbstractSamples of granulated slag from Scunthorpe, Humberside, collected over several years, vary somewhat in chemical composition reflecting differences in iron-making practice. All contain some melilite and oldhamite crystals and minor amounts of iron along with the glass. Granulated slag from Usinor, Dunkirk, France, has a little more CaO than the Scunthorpe material with crystals of merwinite and oldhamite. Pelletised slag from Redcar, Teeside, is much more vescicular than the granulated material and contains melilite and oldhamite.The melilite crystals contain many inclusions of oldhamite and iron. They span a wide range within the akermanite-gehlenite series and are non-stoichiometric in composition. The merwinite may have formed largely by quench crystallization. Oldhamite is probably the first phase to form in all the slags. The silicate mineralogy can be explained in terms of the phase relationships within the CaO-SiO2-Al2O3-MgO quaternary system. The small difference in composition of the French slags is sufficient for them to fall into the primary phase field of merwinite rather than melilite. Assuming that only a minor proportion of crystals is acceptable in slags for use in Portland Blastfurnace Cement, the present low Al (< 11 % Al2O3) British and French slags are approaching an optimum composition.

Constitution of AuSn–Pb–Sn partial ternary system

Thermal analysis, metallography, and electron-probe microanalysis have been used to corroborate one of the conflicting constitutions of the AuSn–Pb–Sn partial ternary system. The phase equilibria consist of two ternary transition reactions at 13–0Au, 48–0Pb, 39–0Sn at.-%, 275°C and 8–5Au, 28–0Pb, 63–5Sn at.-%, 210°C, and a ternary eutectic at 3–5Au, 20–0Pb, 76–5Sn at.-%, 177°C. The solubility of Pb in the ternary system is substantial and between 275 and 177°C the system can dissolve up to 4 at.-% Au and 27 at.-%Sn. The maximum width of the AuSn primary phase field in the partial AuSn–Pb–Sn system is approximately 3 at.-%. and that of Sn approximately 2 at.-%.MST/82

Liquidus phase relationships on the join anorthite-forsterite-quartz at 10 kbar with applications to basalt petrogenesis

Liquidus phase relationships determined on the join CaAl2Si2O8 (anorthite)-Mg2SiO4 (forsterite)-SiO2 (quartz) at 10 kbar show that increasing pressure causes the forsterite and anorthite primary phase fields to shrink and the spinel, enstatite and silica fields to expand. The boundary line between the enstatite and forsterite fields and that between the enstatite and quartz fields both move away from the SiO2 apex as pressure increases. Therefore, simplified source peridotite would yield simplified basaltic partial melts with decreasing silica as pressure increases, as has been found in other studies. Also, increasing pressure decreases the amount of silica enrichment in residual liquids produced by fractional crystallization. Although anorthite is unstable in simplified peridotite above 9 kbar in the system CaO-MgO-Al2O3-SiO2, it is an important phase in the fractional crystallization of simplified basalts at 10 kbar and probably also in natural basalts.

Ternary phase relations of the chalcopyrite compound CuGaSe2

The ternary Cu-Ga-Se phase diagram has been determined by DTA and x-ray analysis. In addition to two ternary solid solutions based on the binary compounds Cu2.xSe and Ga2Se3, only one ternary phase, the chalcopyrite CuGaSe2 (peritectic m.p. 1030°C), was encountered. The liquidus contains two regions of liquid immiscibility, one which extends from the Cu-rich (Cu, Se) binary liquid immiscibility to the Ga-rich (Ga, Se) binary immiscibility, and the other which is a minor extension of the Se-rich (Cu, Se) binary liquid immiscibility. The liquidus maxima include those at the binary boundaries: Cu (1087°C), Cu67Se33 (1148°C), GaSe (960°C); and a ternary liquidus maximum at Cu19Ga28.5Se52.5 (1112°C), the maximum melting point of a solid solution based on the defect-zincblende phase of Ga2Se3. The primary phase fields are identified and the crystal growth of CuGaSe2 solid solutions from nonstoichiometric melts is discussed, especially the most satisfactory Bridgman growth from the Cu2Se-CuGaSe2 join. Subsolidus phase relations are also proposed for the Cu-Ga-Se system, and probable similaritics in all I-III-VI ternary diagrams are suggested.

A thermochemical calculation of the pyroxene saturation surface in the system diopside-albite-anorthite

The pyroxene saturation surface in the system diopside-albite-anorthite may be calculated to ±10° C from thermochemical data over most of its composition range. The thermochemical data used are the experimentally determined enthalpies of mixing of the ternary liquids and the enthalpy of fusion of diopside. These are combined with a mixing model for the configurational entropy in the melt and the activity of CaMgSi 2O 6 in the clinopyroxene, which is less than unity due to departures from CaMgSi 2O 6 stoichiometry. The ‘two-lattice’ melt model appears to work satisfactorily throughout the pyroxene primary phase field but probably needs modification at more anorthite-rich compositions.

Liquidus isotherms, solidus lines and LPE growth in the Te-rich corner of the Hg-Cd-Te system

Liquidus isotherms for the Hg1−xCdxTe primary phase field in the Te-rich corner of the Hg-Cd-Te ternary system have been determined for temperatures from 425 to 600‡C by a modified direct observational technique. These isotherms were used to help establish conditions for the open-tube liquid phase epitaxial growth of Hg1−xCdxTe layers on CdTe1−ySey substrates. Layers with x ranging from 0.1 to 0.8 have been grown from Te-rich HgCdTe solutions under flowing H2 by means of a horizontal slider technique that prevents loss of Hg from the solutions by evaporation. Growth temperatures and times of 450–550‡C and 0.25–10 min, respectively, have been used. The growth solution equilibration time is typically 1 h at 550‡C. Source wafers, supercooled solutions, and (111)-oriented substrates were employed in growing the highest quality layers, which were between 3 and 15 Μm thick. Electron microprobe analysis was used to determine x for the epitaxial layers, and the resulting data, along with the liquidus isotherms, were used to obtain solidus lines. In addition to EMP data, optical transmission results are given.

The system CaOAl 2O 3Fe 2O 3 with added fluoride flux

Effects of fluoride fluxes, especially CaSiF 6·2H 2O upon phase equilibria in the system CaOAl 2O 3Fe 2O 3 are described, presenting liquidus data, new phase field boundaries and invariant points and solid solution areas. The primary phase field for C 12−xA 7·CaF 2 is increased substantially in size, and liquidus or invariant temperatures are depressed by amounts ranging from 20 to 80°C.

Dependence of Phase Composition on Nuclei Available in SiO2‐A12O3 Mixtures

Phase equilibria in the system SiO/sub 2/--Al/sub 2/O/sub 3/ were studied. Data obtained by conventional static quenching and phase analysis are difficult to interpret due to persistent metastability in silicate systems. Aksay and Pask, using a diffusion couple technique to determine stable phase equilibria, proposed the stable and metastable phase equilibrium boundaries to explain experimentally observed behavior. The major area of difference in phase equilibria studies is in the nature of the stable equilibria in the high alumina portion of the diagram, i.e., the melting behavior of mullite and the extent of the ..cap alpha..-Al/sub 2/O/sub 3/ primary phase field. Results are reported of an experiment designed to seek improved resolution in these areas and to clarify the phase behavior in the system SiO/sub 2/--Al/sub 2/O/sub 3/.