Thermodynamic properties of Na2O-SiO2-CaO melts at 1000 to 1100 °C

The thermodynamic properties of Na₂O-SiO₂ and Na₂O-SiO₂-CaO melts have been measured using the galvanic cell Activities of Na₂O were calculated from the reversible emf of the cell. This is possible because the activity of Na₂O in the Na₂O-WO₃ liquid is known from previous work. Data for the binary Na₂O-SiO₂ system were obtained between 1000 and 1100 °C and for compositions ranging from 25 wt pct to 40 wt pct Na₂O. At 1050 °C, Log varied from approximately 10.2 at 25 wt pct Na₂O to approximately −8.3 at 40 wt pct Na₂O, the dependence with respect to composition being nearly linear. The Gibbs-Duhem equation was used to calculate the activities of SiO₂(s), and the integral mixing properties,G ^M, H^M, andS ^M, were derived. At the di-silicate composition,G ^M = −83 kJ/mol,H ^M = −41 kJ mol andS ^M = 33 J/mol K at 1000 °C. (Standard states are pure, liquid Na₂O and pure, solid tridymite.) The activity data are interpreted in terms of the polymeric nature of silicate melts. Activities of Na₂O in the Na₂O-CaO-SiO₂ system were measured for the 25, 30 and 35 wt pct Na₂O binary compositions with up to 10 wt pct CaO added. The addition of CaO caused an increase in the activity of Na₂O at constant . The experimental data agree well with the behavior predicted by Richardson’s ternary mixing model.     

Nb2O5-Al2O3-MgO-Na2O-CaO-SiO2体系相平衡研究

为揭示Nb2O5-Al2O3-MgO-Na2O-CaO-SiO2多元含铌炉渣体系中的铌矿物的定向结晶规律,采用高温相平衡—冷淬—SEM-EDS/XRD/EMPA试验方法,考察了温度、钙硅比（CaO/SiO2）、Nb2O5含量等因素对炉渣相平衡关系的影响,并构建了含铌矿物结晶析出的优势相图。结果表明：铌的结晶矿物主要有三种,分别为Ca2Nb2O7、Ca(14-x)Nb(2+x)Si8O(35+1.5x)和3CaO?MgO?Nb2O5;铌先富集于液相,相较于脉石组分,含铌固相为后析出相;CaO/SiO2增加会使含铌固相优势区间发生从Ca2Nb2O7相到Ca(14-x)Nb(2+x)Si8O(35+1.5x)相、再到3CaO?MgO?Nb2O5相的转变。Ca2Nb2O7相的优势析晶区间为：温度1 050~1 200 ℃,C/S=0.8~1.2。Nb2O5在Ca(14-x)Nb(2+x)Si8O(35+1.5x)相中的嵌布质量浓度在18.5%~19.5%。     

Interactions in the Al2O3 ― ZrO2 ― La2O3 System at 1250 and 1650°C

Triangulation has been determined for the Al₂O₃ ZrO₂ La₂O₃ system, and 1250 and 1650°C isothermal sections of the phase diagram have been constructed. The LaAlO₃ La₂Zr₂O₇ section is quasibinary, while the LaAlO₃ T-ZrO₂ and La₂O₃ ·11Al₂O₃ T-ZrO₂ ones are partially quasibinary. The triangulation of the ternary system is based on ZrO₂ and a phase containing it. No ternary compounds or regions of ternary solid solutions have been identified.     

Evolution and coarsening of Al2O3 dispersoids at 500 °C to 600 °C in a mechanically alloyed Al-Ti-O based material

The formation and coarsening of Al₂O₃ dispersoids have been investigated at 500 °C, 550 °C, and 600 °C in a mechanically alloyed (MA) extrusion of composition Al-0.35wt pct Li-1wt pct Mg-0.25wt pct C-10vol pct TiO₂ for times up to 1500 hours. In the as-extruded condition, the dispersed phases included Al₃Ti, Al₄C₃, MgO, cubic TiO (C-TiO), monoclinic TiO (M-TiO), TiO₂, and a small amount of Al₂O₃. However, numerous Al₂O₃ dispersoids (various polymorphs: η, γ, α, and δ) with “block-shaped” morphology were formed after heat treatment due to reduction of C-TiO, M-TiO, and TiO₂. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) showed conclusively the transformation of these phases to additional Al₂O₃ and Al₃Ti. High resolution TEM showed that the α-Al₂O₃ dispersoids exhibited some lattice matching with the α-Al matrix. Coalescence of the block-shaped Al₂O₃ dispersoids occurred after heat treatment, and Al₄C₃ also became attached to them. The length and width of the block-shaped Al₂O₃ dispersoids increased by a factor of ∼1.55 between 340 and 1500 hours at 600 °C.     

Phase Equilibria in the ZrO2–La2O3–Gd2O3 System at 1600°C

Powder Metallurgy and Metal Ceramics - Phase equilibria and structural transformations in the ternary ZrO2–La2O3–Gd2O3 system at 1600°C were studied by X-ray diffraction,...     

Phase Equilibria in the ZrO2–La2O3–Sm2O3 System at 1100°C

Powder Metallurgy and Metal Ceramics - Phase equilibria and structural transformations in the ternary ZrO2–La2O3–Sm2O3 system at 1100°C were studied by X-ray diffraction over the...     

Interaction of Lanthanum,Lutetium, and Ytterbium Oxides at 1600°C

Powder Metallurgy and Metal Ceramics - Phase equilibria in the La2O3–Lu2O3–Yb2O3 system were studied by X-ray diffraction and electron microscopy for the first time at 1600°C over...     

The Al2O3-ZrO2-Yb2O3 phase diagram. I. Isothermal sections at 1250 and 1650°C

Isothermal sections at 1250 and 1650 °C of the Al₂O₃-ZrO₂-Yb₂O₃ phase diagram are plotted for the first time. Phase equilibria are established at these temperatures. No ternary compounds and appreciable solid solution regions based on components or binary compounds are found in the ternary system. A partially pseudobinary section Yb₃A₅-F triangulating the Al₂O₃-ZrO₂-Yb₂O system is established.     

Low-temperature synthesis of α-Al2O3

The paper considers the production of nanocrystalline α-Al₂O₃ powder at a temperature below 900 °C. It is shown that α-Al₂O₃ forms after high-temperature treatment of aluminum nitrate mixed with a mineralizer at 650 °C (holding time of 6 h). The primary particles of α-Al₂O₃ are 25 to 30 nm in size and the specific surface area is 15.2 m²/g. The powder is used to produce self-reinforced composites in the ZrO₂-Y₂O₃-CeO₂-Al₂O₃ system.     

Reactions of Fe-Cr and Ni-Cr alloys in CO/CO2 gases at 850 and 950 °C

A series of Fe-Cr and Ni-Cr solid solution alloys was reacted at 850 and 950 °C in CO/CO₂ gas mixtures in which FeO and NiO were unstable. The compctitive tendencies toward the carburization and oxidation of the chromium solute, as compared to a graphical thermodynamic "metastability" criterion, were tested experimentally. Relatively good agreement was found between predictions and experiments for the occurrence of Cr carburization beneath Cr₂O₃ internal oxides or external scales. The chromium contents required for the transition from internal oxidation of Cr to the formation of Cr₂O₃ external scales in CO/CO₂ gas mixtures were established for Fe-Cr and Ni-Cr alloys. The Cr₂O₃ external scales formed on Fe-Cr alloys were found to be relatively impervious to carbon penetration for short (12-hour) experiments. No carburization was observed in the Ni-Cr alloys, but the only alloys that were predicted to carburize were the ones that formed external scales. Formerly Graduate Student, The Ohio State University     

Magnetic Properties and Activity of Pt-Er/γ-Al2O3 Catalysts

A series of Pt-Er/γ-Al2O3 catalysts containing 0. 5 % （mass fraction） platinum and 0.05 %-1.5 % Er were prepared by impregnation of γ-Al2O3 supported with different concentrations of erbium chloride solution. The surface properties of the catalysts were studied by methods of temperature programmed reduction and temperature programmed desorption. The magnetic behavior of Pt-Er/γ-Al2O3 catalysts were studied with a Faraday magnetic balance and the results show that the addition of Er can affect the surface properties, the catalytic activities, and magnetic behavior of the reforming catalysts. It is found that there is a corresponding relationship between the susceptibility and selectivity of Pt-Er/γ-Al2O3 catalysts. The experimental results show that Er plays the role of electron promoter.     

Influence of reaction of Al2O3 and carbonaceous materials in Al2O3–C refractories on aluminum and carbon pick-up of iron

Carbon-containing Al2O3 refractory crucibles and pure Al2O3 refractory crucible were fabricated to study the effect of carbon-containing Al2O3-C refractories on aluminum and carbon pick-up of iron.Refractory crucibles with pure iron powder were placed in a vacuum induction furnace and heated at 1600℃ for regular time under flowing argon atmosphere.The Al and C contents of iron samples were analyzed,and iron samples were also investigated using a field scanning electron microscope equipped with energy-dispersive spectroscope.The results showed that carbon materials did affect the interac?tion of(Al2O3-C)/Fe system,carbothermal reduction in alumina occurred in the reaction system and the extent of reactions depended on the kinds of carbon materials.     

Distribution of Calcium and Aluminum Between Molten Silicon and Silica-Rich CaO-Al2O3-SiO2 Slags at 1823 K (1550 °C)

Metallurgical and Materials Transactions B - Oxidative refining of silicon after tapping from the furnace is performed to remove calcium and aluminum impurities. Depending on the slag composition,...     

Microstructure,Texture, and Hardness Evolution of Cold-Rolled High-Purity Ti Sheet During Annealing at 350 °C to 550 °C

Metallurgical and Materials Transactions A - The microstructural, textural, and hardness evolution of a cold-rolled high-purity Ti sheet (50 pct reduction in thickness) during isochronal annealing...     

Na2O-Al2O3 system: Activity of Na2O in (α + β)- and (β + β)-alumina

The activity of Na₂O in a biphasic mixture of (α + β)-alumina has been measured in the temperature range of 700 to 1100 K using the solid-state galvanic cell:

Activity Coefficient of SiO2 in SiO2-Al2O3-CaO Slags with Low SiO2-Content at 1873 K (1600 °C)

The activity coefficient of SiO₂ in SiO₂-Al₂O₃-CaO slags with limited Al₂O₃ content was measured by equilibrating Fe-C-Si melt and slags at 1873 K (1600 °C). When the Al₂O₃ content was between 48 and 54 wt pct, the results show that $ \gamma_{{{\text{SiO}}_{ 2} }} $ rapidly decreases as the amount of SiO₂ in the slag decreases. The equilibrium amounts of Si and Al in a Fe melt in equilibrium with SiO₂-Al₂O₃-CaO slags were calculated based on the result of this study.