ІЗОТЕРМІЧНИЙ ПЕРЕРІЗ ДІАГРАМИ СТАНУ СИСТЕМИ Al2O3−TiO2−Nd2O3 ПРИ 1400 °С

Isothermal section of the Al2O3–TiO2–Nd2O3 phase diagram at 1400 °C is constructed for the first time. It is the part of systematic investigations of Al2O3–TiO2–Ln2O3 (Ln=lanthanides,Y) systems. The 1400°C was taken as the temperature, at which no liquid is expected in the system. Samples were prepared by a chemical method. Samples were annealed in air at 1400°С for 80 hours and cooled in the furnace. Phases in the samples were determined by XRD analysis. New phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of seven narrow twophase and eight three-phase regions. Triangulation of the system is determined by the phase Nd2Ti2O7, which is in equilibrium with compounds Al2TiO5, NdAlO3 and system components TiO2 and Al2O3. Formation of phases Nd4Ti9O24, Nd2Ti3O12 and Nd2TiO5 in binary boundary system TiO2–Nd2O3 causes the appearance of partially quasibinary sections Al2TiO5–Nd4Ti9O24, Al2TiO5–Nd2Ti3O12 and NdAlO3–Nd2TiO5. The obtained results make a significant contribution to the understanding of interactions between the components in the system studied. The system includes binary compounds with high electro-optical, ferroelectric, piezoelectric, photocatalytic properties, mikrowave dielectric ceramic. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to fi nd and establish the coordinates of new three-phase and two-phase eutectics for directional solidifi cation and to obtain new high-temperature structural materials in the Al2O3–TiO2–Nd2O3 system

Effects of Impurity Content on the Sintering Characteristics of Plasma-Sprayed Zirconia

Yttria-stabilized zirconia powders, containing different levels of SiO2 and Al2O3, have been plasma sprayed onto metallic substrates. The coatings were detached from their substrates and a dilatometer was used to monitor the dimensional changes they exhibited during prolonged heat treatments. It was found that specimens containing higher levels of silica and alumina exhibited higher rates of linear contraction, in both in-plane and through-thickness directions. The in-plane stiffness and the through-thickness thermal conductivity were also measured after different heat treatments and these were found to increase at a greater rate for specimens with higher impurity (silica and alumina) levels. Changes in the pore architecture during heat treatments were studied using Mercury Intrusion Porosimetry (MIP). Fine scale porosity (<_50 nm) was found to be sharply reduced even by relatively short heat treatments. This is correlated with improvements in inter-splat bonding and partial healing of intra-splat microcracks, which are responsible for the observed changes in stiffness and conductivity, as well as the dimensional changes

ФАЗОВІ РІВНОВАГИ В СИСТЕМАХ Al2O3–TiO2–Y(Er)2O3 ПРИ 1400 ºС

The aim of this investigation is the construction of isothermal sections for the Al2O3-TiO2-Y(Gd)2O3 phase diagrams at 1400ºС as part of systematic investigations of Al2O3-TiO2-Ln2O3 (Ln=lanthanides, Y) systems. The 1400°C was taken as the temperature, at which no liquid phases are expected in the both systems. The isothermal sections at 1400 °С for the Al2O3– TiO2–Y(Er)2O3 phase diagrams were constructed for the first time. Samples were prepared by a chemical method. Samples were annealed in air at 1400°С for 80 hours and cooled in the furnace. This temperature value was selected with a view to provide possibility of phase transformations character studies. New phases and appreciable solubility regions based on the components and binary compounds were not found, as predicted. Triangulation of the systems is determined by the phase Y(Er)2T2O7, which is in equilibria with compounds Al2TiO5, Y(Er)3Al5O12, Y(Er)AlO3, Y(Er)4Al2O9 and components TiO2 and Al2O3. The structures of isothermal sections of the both systems are similar. The systems are triangulated into six secondary triangles, in which three-phase eutectic are expected. In five quasibinary sections two-phase eutectic should expect to exist. The obtained results will make a significant contribution to the understanding of interactions between the components in the systems studied.This systems offer a number of promising opportunities such as high-temperature structural composites based on directionally solidified two-phase and three-phase eutectic materials, solid electrolytes (SOFCs, oxygen sensors, film for electronic devices, etc.), promising to accumulate water, immobilizing materials for nuclear industry, tough ceramics, catalysts carriers, wear- and corrosion-resistant ceramic coatings and super refractories.Вперше побудовано ізотермічні перерізи діаграм стану систем Al2O3–TiO2–Y(Er)2O3 при 1400 °С. Триангуляція систем визначається фазою Y(Er)2T2O7, яка знаходиться в рівновазі зі сполуками Al2TiO5, Y(Er)3Al5O12, Y(Er)AlO3, Y(Er)4Al2O9 та компонентами системи TiO2 і Al2O3. Системи триангулюються на шість вторинних трикутників, в яких очікується наявність трифазних евтектик, а на п’яти квазібінарних перерізах систем слід очікувати існування квазіподвійних евтектик

PHASE EQUILIBRIA IN THE Al2O3–TiO2–Y(Er)2O3 SYSTEMS AT 1400 ºС

The aim of this investigation is the construction of isothermal sections for the Al2O3-TiO2-Y(Gd)2O3 phase diagrams at 1400ºС as part of systematic investigations of Al2O3-TiO2-Ln2O3 (Ln=lanthanides, Y) systems. The 1400°C was taken as the temperature, at which no liquid phases are expected in the both systems. The isothermal sections at 1400 °С for the Al2O3– TiO2–Y(Er)2O3 phase diagrams were constructed for the first time. Samples were prepared by a chemical method. Samples were annealed in air at 1400°С for 80 hours and cooled in the furnace. This temperature value was selected with a view to provide possibility of phase transformations character studies. New phases and appreciable solubility regions based on the components and binary compounds were not found, as predicted. Triangulation of the systems is determined by the phase Y(Er)2T2O7, which is in equilibria with compounds Al2TiO5, Y(Er)3Al5O12, Y(Er)AlO3, Y(Er)4Al2O9 and components TiO2 and Al2O3. The structures of isothermal sections of the both systems are similar. The systems are triangulated into six secondary triangles, in which three-phase eutectic are expected. In five quasibinary sections two-phase eutectic should expect to exist. The obtained results will make a significant contribution to the understanding of interactions between the components in the systems studied.This systems offer a number of promising opportunities such as high-temperature structural composites based on directionally solidified two-phase and three-phase eutectic materials, solid electrolytes (SOFCs, oxygen sensors, film for electronic devices, etc.), promising to accumulate water, immobilizing materials for nuclear industry, tough ceramics, catalysts carriers, wear- and corrosion-resistant ceramic coatings and super refractories

ISOTHERMAL SECTION OF THE Al2O3–TiO2–Yb2O3 PHASE DIAGRAM AT 1400 °С

One of the main directions of the modern materials development science is the development of new oxide ceramic materials for engineering, energy, chemical, aerospace, electronic and other industries in multi component systems, including containing TiO2, Al2O3 and rare earth oxides. The Al2O3‒TiO2‒Yb2O3 system attracts the attention of researchers because possibility of design of structural high-temperature materials with low coefficient of thermal expansion, as well as refractory ceramic materials. The basis of new materials creation is the study of physical and chemical interaction, which is reflected in the phase diagrams of the systems. The purpose of this study is the construction of phase diagram isothermal section for the Al2O3−TiO2−Yb2O3 system at 1400 °С, which is the part of the interaction systematic study of the Al2O3−TiO2−Ln2O3 systems, where Ln = (La, Nd, Gd, Er, Yb and Y). The samples were prepared by a chemical method. Annealed in air at 1400°С for 80 hour sand cooled in the furnace. Phase content of the samples was determined by XRD analysis. New multicomponent phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of four narrow two-phase Al2TiO5+Yb2Ti2O7, Al2O3+Yb2Ti2O7, Yb3Al5O12+Yb2Ti2O7, Yb3Al5O12+Yb2TiO5 regions and five threephase Al2TiO5+TiO2+Yb2Ti2O7, Al2TiO5+Yb2Ti2O7+Al2O3, Al2O3+Yb2Ti2O7+Yb3Al5O12, Yb2Ti2O7+Yb3Al5O12+Yb2TiO5, Yb3Al5O12+Yb2TiO5+С-Yb2О3 fields. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to find and establish the coordinates of new three-phase and two-phase eutectics for directional solidification and to obtain new high-temperature structural materials in the Al2O3–TiO2–Yb2O3 system

ІЗОТЕРМІЧНИЙ ПЕРЕРІЗ ДІАГРАМИ СТАНУ СИСТЕМИ Al2O3−TiO2−Yb2O3 ПРИ 1400 °С

One of the main directions of the modern materials development science is the development of new oxide ceramic materials for engineering, energy, chemical, aerospace, electronic and other industries in multi component systems, including containing TiO2, Al2O3 and rare earth oxides. The Al2O3‒TiO2‒Yb2O3 system attracts the attention of researchers because possibility of design of structural high-temperature materials with low coefficient of thermal expansion, as well as refractory ceramic materials. The basis of new materials creation is the study of physical and chemical interaction, which is reflected in the phase diagrams of the systems. The purpose of this study is the construction of phase diagram isothermal section for the Al2O3−TiO2−Yb2O3 system at 1400 °С, which is the part of the interaction systematic study of the Al2O3−TiO2−Ln2O3 systems, where Ln = (La, Nd, Gd, Er, Yb and Y). The samples were prepared by a chemical method. Annealed in air at 1400°С for 80 hour sand cooled in the furnace. Phase content of the samples was determined by XRD analysis. New multicomponent phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of four narrow two-phase Al2TiO5+Yb2Ti2O7, Al2O3+Yb2Ti2O7, Yb3Al5O12+Yb2Ti2O7, Yb3Al5O12+Yb2TiO5 regions and five threephase Al2TiO5+TiO2+Yb2Ti2O7, Al2TiO5+Yb2Ti2O7+Al2O3, Al2O3+Yb2Ti2O7+Yb3Al5O12, Yb2Ti2O7+Yb3Al5O12+Yb2TiO5, Yb3Al5O12+Yb2TiO5+С-Yb2О3 fields. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to find and establish the coordinates of new three-phase and two-phase eutectics for directional solidification and to obtain new high-temperature structural materials in the Al2O3–TiO2–Yb2O3 system.Вперше побудовано ізотермічний переріз діаграми стану системи Al2O3−TiO2−Yb2O3 при 1400 °С. Нових фаз і помітних областей гомогенності на основі компонентів та подвійних сполук не знайдено. У трифазних областях слід очікувати наявність п’яти потрійних евтектик Al2TiO5 + TiO2 + Yb2Ti2O7, Al2TiO5 + Yb2Ti2O7 + Al2O3, Al2O3 +Yb2Ti2O7 + Yb3Al5O12, Yb2Ti2O7 + Yb3Al5O12 + Yb2TiO5, Yb3Al5O12 + Yb2TiO5 + С-Yb2О3, а на бінарних перерізах − чотири подвійні евтектики Al2TiO5 + Yb2Ti2O7, Al2O3 + Yb2Ti2O7, Yb3Al5O12 + Yb2Ti2O7, Yb3Al5O12 + Yb2TiO5