Properties of TlInSe2–TlNdSe2 Solid Solutions

TlIn_{1 – x} Nd _x Se₂(0 < x 0.1) solid solutions were characterized by x-ray diffraction and temperature-dependent electrical conductivity, Hall effect, thermoelectric power, and heat capacity measurements. With increasing Nd content, the lattice parameters of the solid solutions increase almost linearly, and their band gap decreases.     

CuGaTe2–CuAlTe2 System

It was shown by x-ray diffraction and differential thermal analysis that CuGaTe₂ and CuAlTe₂ form a continuous series of solid solutions. CuGaTe₂, CuAlTe₂, and CuAl _x Ga_{1 – x} Te₂ crystals consisting of large blocks were grown by the horizontal Bridgman process, and their thermal expansion and near-edge transmission and reflection spectra were measured. The thermal expansion coefficient was shown to vary linearly across the solid-solution series, while the band gap is a nonlinear function of composition.     

Phase Relations in the SnSe2–Er2Se3 System

The phase diagram of the SnSe₂–Er₂Se₃ system is studied using differential thermal analysis, x-ray diffraction, microstructural analysis, and microhardness and density measurements. The SnSe₂–Er₂Se₃ system is pseudobinary and contains two eutectics and two intermediate phases, Er₂Sn₃Se₉ and Er₂SnSe₅. At room temperature, the SnSe₂-based solid solution extends to 4.5 mol % Er₂Se₃, and the SnSe₂ solubility in Er₂Se₃ is 2 mol %.     

Thermal Expansion and Electroabsorption in the TlInS2–TlYbS2 System

The thermal expansion and electroabsorption of TlIn_{1 – x} Yb _x S₂ solid solutions were measured as a function of temperature. The introduction of Yb into TlInS₂ was found to fully suppress the phase transition. It is shown that there is a perfect correlation between the band gap and thermal expansion of the TlIn_{1 – x} Yb _x S₂ solid solutions: both decrease with increasing Yb content. This finding is interpreted in terms of the effect of Yb substitution on bond strength.     

Equilibrium Vapor Composition in the Pb–I2 System

The equilibrium vapor composition in the Pb–I₂ system at temperatures from 400 to 2000 K and total pressures from 10² to 10⁵ Pa was assessed by thermodynamic analysis. The results show that the dominant vapor species is PbI₂. PbI₂ dissociation is significant starting at 1000–1300 K, depending on the total pressure in the system.     

Phase Relations in the SrO–Bi2O3–Fe2O3 System

The phase relations in the composition region SrFeO_{3 –} –Fe₂O₃–BiFeO₃ are studied in air by x-ray diffraction and electron microscopy. The 1000°C phase compatibility diagram is constructed. Sr_{1 – x} Bi _x FeO_{3 –} solid solutions are prepared in the range 0 < x 0.8. Their lattice parameter is found to vary nonlinearly with x. Two new phases were identified: (Sr,Bi)₃Fe₄O _y (tetragonal lattice, a= 3.907(2) Å, c= 27.30(2) Å) and Sr_0.6Bi_0.4FeO_{3 –} (tetragonal lattice,a = 5.555(2) Å, c= 11.848(5) Å).     

Synthesis of W–Zr–Ti Alloy via Combustion in the WO3–ZrO2–TiO2–Mg System

Inorganic Materials - We have studied the self-propagating high-temperature synthesis (SHS) process due to the combustion of a WO3 + ZrO2 + TiO2 + Mg multicomponent mixture. The ratio of the oxide...     

Phase Transformations in the Y2Cu2O5–BaCuO2 System

The sequence of phase transformations in the Y₂Cu₂O₅–BaCuO₂ pseudobinary system was studied during heating and cooling in the range 1170–1310 K. The results demonstrate that the reaction zone in BaCuO₂/Y₂Cu₂O₅ diffusion couples consists of BaCuO₂/YBa₂Cu₃O_{7 –} /Y₂BaCuO₅/Y₂O₃/Y₂Cu₂O₅ layers, corresponding to the sequence of chemical changes during YBa₂Cu₃O_{7 –} crystallization between 1170 and 1220 K. In the range 1260–1310 K, BaCu₂O₂ is formed. During cooling of a Y₂Cu₂O₅ + 4.3BaCuO₂ mixture, YBa₂Cu₃O_{7 –} crystallizes in a wide temperature range, between 1240 and 1190 K. The process depends on the presence of BaCu₂O₂ on the surface of Y₂BaCuO₅ grains in the high-temperature solution and the oxygen supply from the gas phase.     

BaWO4–BaCuO2–Y2Cu2O5–“1010” Section of the Y2O3–BaO–WO3–CuO System

The phase region of cubic perovskite-like solid solutions (a = 8.28–8.40 Å) in the Y₂O₃–BaO–WO₃–CuO system is outlined, and the phase compatibility diagram of the BaWO₄–BaCuO₂–Y₂Cu₂O₅–1010 (1010 = Y₂WO₆ + Y₂W₃O₁₂) is constructed.     

Liquidus Relations in the Li2WO4–LiPO3–LiCl System

The liquidus relations in the Li₂WO₄–LiPO₃–LiCl system were studied by thermal analysis. The liquidus surface was found to comprise the primary-crystallization fields of Li₂WO₄, LiPO₃, LiCl, and the congruently melting compound 2Li₂WO₄· LiPO₃. The low-melting compositions revealed in the system studied are of interest for the preparation of tungsten bronzes.     

Phase Relations in the NiFe2O4–NiCr2O4–CuCr2O4System

The phase relations in the NiFe₂O₄–NiCr₂O₄–CuCr₂O₄system were investigated experimentally and theoretically. X-ray diffraction data were used to construct the phase diagram of the system and elucidate the structural mechanisms of the transitions from the cubic spinel structure to the tetragonal (I42d, c/a< 1 and I4₁/amd, c/a> 1) and orthorhombic (Fdd2) structures.     

Phase Relations in the LiOH–ZrO2–GeO2–H2O System at 500°C and 0.1 GPa

The phases crystallizing in the LiOH–ZrO₂–GeO₂–H₂O system at 500°C and 0.1 GPa are Zr^[8]Ge^[4]O₄, Li₂Ge^[6]Ge₂ ^[4]O₆(OH)₂, Li₃HGe₄ ^[6]Ge₃ ^[4]O₁₆ · 4H₂O, and Li₂Ge^[4]O₃. These phases differ in the oxygen coordination of Ge. At a ZrO₂ : GeO₂ molar ratio of 1 : 1, increasing the LiOH concentration leads to the crystallization of a ZrO₂ + Li₂GeO₃ mixture, instead of ZrGeO₄. At ZrO₂ : GeO₂ ratios in the range 1 : 2 to 1 : 6, Li₂Ge^[6]Ge₂ ^[4]O₆(OH)₂ crystallizes together with ZrGeO₄. The formation of the structures of ZrGeO₄ and Li₂Ge^[6]Ge₂ ^[4]O₆(OH)₂ is discussed in terms of the matrix assembly of crystal structures from cyclic subpolyhedral structural units.     

Phase Relations in the KOH–TiO2–SiO2–H2O System at 500°C and 0.1 GPa

The compounds crystallizing in the system KOH–TiO₂(rutile)–SiO₂–H₂O at 500°C, 0.1 GPa, and different TiO₂, SiO₂, and KOH concentrations are K₂TiSi₆O₁₅ (Ti davainite structure), K₂TiSi₃O₉ (Zr wadeite structure), and K₂Ti₆O₁₃ (Ti jeppeite structure). The matrix-assembly model is used to examine the formation of the K₂TiSi₆O₁₅ structure (sp. gr. P ) from subpolyhedral structural units. A centrosymmetric cyclic 12-polyhedron cluster of composition K₂ M ₂ T ₁₀ is identified, in which the K atoms lie in center positions above and below the plane of the MT ring. The precursor cluster K₂ M ₂ T ₁₀ is identical in structure to the Cs₂ M ₂ T ₁₀ cluster in Cs₂TiSi₆O₁₅, a titanosilicate which has a topologically different MT framework. The mechanisms of the assembly of the three-dimensional MT frameworks in these titanosilicates differ at the level of primary MT chains: the condensation of the clusters in K₂TiSi₆O₁₅ involves five common corners, while that in Cs₂TiSi₆O₁₅ involves only three corners.     

Properties of Phases and Alloys of the Mo–Ni–B System in the Ni–MoNi–Mo2NiB2–Ni2B Region

Materials Science - For alloys of the Mo–Ni–B system annealed at subsolidus temperatures (and some as-cast alloys) in the Ni–MoNi–Mo2NiB2–Ni2B region, we study the...     

Computer Simulation of Noncrystalline Ionic–Covalent Oxides in the SiO2–CaO–FeO System

Molecular dynamics simulations were used to study self-diffusion in noncrystalline SiO₂–CaO–FeO oxides at 1873 K. The simulations were carried out in the purely ionic and ionic–covalent approximations. In the latter case, use was made of the semiclassical molecular dynamics simulation method proposed earlier for studying ionic–covalent oxide systems. At SiO₂ contents below 40 mol %, the self-diffusion coefficients of the constituent ions depend little on the oxide composition and the assumed character of bonding. As the SiO₂ content increases to 40 mol % and above, the ion mobility drops sharply. The thermodynamic and structural parameters derived from the ionic–covalent simulations of the ternary oxides are in reasonable agreement with experimental data.     

Ion-Conducting Defect Pyrochlore Phases in the K2O–Sb2O3–WO3 System

Potassium tungstate antimonates were prepared by calcining K₂CO₃ + Sb₂O₃ + 2(1 – – )WO₃ mixtures in air. Data on the phase composition of the obtained materials were used to locate the pyrochlore phase region in the Sb₂O _z –W₂O₆ – K₂O composition triangle at 1170 K. The distributions of the constituent ions and lattice defects over the crystallographic positions of space group Fd3m were inferred from structural and gravimetric data. The ac conductivity of the potassium tungstate antimonates was measured from 600 to 1000 K. The conductivity and its activation energy were shown to be correlated with the concentrations of cation (position 16d) and anion (position 8b) defects. The concentration and mobility of K⁺ ions involved in charge transport were determined.     

Liquidus Relations in the Na2WO4–LiPO3–WO3System

The liquidus relations in the Na₂WO₄–LiPO₃–WO₃system (diagonal section of the quaternary mutual system Li,Na||PO₃,WO₄,WO₃) were studied by thermal analysis at WO₃contents of 60 mol %. The results demonstrate that, in the composition region studied, the liquidus surface comprises the primary-crystallization fields of Na₂WO₄, LiPO₃, and the congruently melting compounds Na₂WO₄· WO₃, 3LiPO₃· WO₃, Na₂WO₄· NaPO₃, and 2Li₂WO₄· LiPO₃. The low-melting compositions revealed in the system studied are of interest for the preparation of Li _x Na _y WO₃bronzes.     

New Phases in the Mg–Ta–H2 System at High Quasi-hydrostatic Pressures

The Mg–Ta–H₂ system was investigated at quasi-hydrostatic pressures from 4 to 5 GPa and temperatures from 900 to 1000°C. X-ray diffraction studies indicate the formation of three new hydrides: (Ta,Mg)H _x (solid solution of magnesium hydride in tantalum hydride), (Mg,Ta)H₂ (solid solution of tantalum hydride in -MgH₂), and Mg _x Ta _y H _z .     

Thermophysicochemical Reaction of ZrCo–Hydrogen–Helium System

Nuclear fusion energy, which is clean and infinite, has been studied for more than half a century. Efforts are in progress worldwide for the demonstration and validation of nuclear fusion energy. Korea has been developing hydrogen isotope storage and delivery system (SDS) technologies including a basic scientific study on a hydrogen storage medium. An SDS bed, which is a key component of the SDS, is used for storing hydrogen isotopes in a metal hydride form and supplying them to a tokamak. Thermophysicochemical properties of the ZrCo–H\(_{2}\)–He system are investigated for the practical utilization of a hydriding alloy system. The hydriding reaction, in which \(\hbox {ZrCoH}_{\mathrm{x}}\) is composed as ZrCo absorbing hydrogen, is exothermic. The dehydriding reaction, in which \(\hbox {ZrCoH}_{\mathrm{x}}\) decomposes into ZrCo and hydrogen, is endothermic. The heat generated through the hydriding reaction interrupts the hydriding progress. The heat loss by a dehydriding reaction impedes the dehydriding progress. The tritium decay product, helium-3, covers the ZrCo and keeps the hydrogen from contact with ZrCo in the SDS bed. In this study, we designed and fabricated a ZrCo bed and its performance test rig. The helium blanketing effect on a ZrCo hydrogen reaction with 0 % to 20 % helium content in a gaseous phase and a helium blanket removal method were studied experimentally. In addition, the volumetric flow rates and temperature at the beginning of a ZrCo hydrogen reaction in a hydrogen or helium atmosphere, and the cooling of the SDS bed by radiation only and by both radiation and natural convection related to the reuse cycle, were obtained.