Constitution of Ni3Al–Ni3Mo–Ni3W section of Ni–Al–Mo–W system

Abstract

The isothermal section of the Ni–Al–Mo–W system has been studied at 75 at.-%Ni at temperatures of 1523 and 1273 K. Constitutional data have been determined using electron probe microanalysis, X-ray diffraction, and microscopical examination. The alloys studied lay in the range 12·5–15 at.-%Al, 2·5–7·5 at.-%Mo, and 2·5–7·5 at.-% W. The phases present at 1523 K were γ, γ′, and α (based on the Mo–W continuous series of solid solutions); at 1273 K, NiMo(δ′) was also encountered. The γ/γ′ mismatch values lay in the range ?0·03 to ?0·75%. In the as-solidified state, the alloys consisted predominantly of γ-phase containing γ′-precipitates formed in the solid state.

MST/462     

Ni3AI–Ni3Cr–Ni3Ta section of Ni–Cr–AI– Ta system

Abstract

The constitution of the 75 at.%Ni section of the Ni–Cr–Al– Ta system has been determined at 1523 and 1273 K. Alloys annealed at these temperatures have been studied using electron probe microanalysis and X–ray diffraction, and their microstructures and associated hardness values have also been examined. The isothermal sections at 1523 and 1273 K contain the following phases: γ+γ′+Ni₃Ta, and Ni₆TaAI, with the following three–phase equilibria between them: γ+γ′+Ni₆TaAI and γ+Ni₃Ta+Ni₆TaAl. The γ′–phase contains up to ~9 at.–%Ta. Some observations on as–cast structures have also been made.

MST/208     

Photoluminescence and scintillation properties of Al(PO3)3–CsPO3–CsBr–CeBr3 glass scintillators

Scintillators, which are widely used as radiation detectors, are phosphors that release absorbed ionizing radiation energy as ultraviolet or visible light. Inorganic glass scintillators have several advantages over inorganic crystal scintillators, such as ease of fabrication and low costs. However, unlike inorganic crystals, which can emit up to tens of thousands of photons/MeV, inorganic glasses exhibit less than several hundred photons/MeV in most cases. Here, we studied an inorganic glass scintillator that exhibits a light yield of 2700 photons/MeV, which exceeds those of previous inorganic glass scintillators with high light yields of approximately 2000 photons/MeV. The density of this material is 3.28 g/cm³, which is relatively high among glass scintillators. Moreover, a fast scintillation decay with a decay time constant of 30.0 ns was obtained and is attributed to the 5d–4f transition of Ce³⁺. Thus, this glass is suitable for gamma- and X-ray detection, thereby expanding the practical applicability of inorganic glass scintillators.

     

Phase Relations in the NaF–WO3 , NaCl–Na3WO3F3 , and NaCl–NaWO3F Systems

The NaF–WO₃, NaCl–Na₃WO₃F₃, and NaCl–NaWO₃F systems were studied by thermal analysis and x-ray diffraction. Solid-state transformations were revealed, and the primary crystallization ranges were outlined. The refractive indices of the sodium fluorotungstates were measured. The thermodynamic functions of Na₃WO₃F₃were derived from emf measurements.     

High thermally stable BiFeO3–PbTiO3–BaTiO3 ceramics with improved ferroelectric properties

High temperature (0.9-x)BiFeO₃–(x)PbTiO₃–0.1BaTiO₃ (BF–PT–BT) ceramics at MPBs (x = 0.18, 0.20 and 0.22) were synthesized by solid-state reaction technique. Well-saturated P–E loops were obtained and an enhanced ferroelectric behavior of P_r ~60 μC/cm² and E_c ~50 kV/cm was observed in 0.68BiFeO₃–0.22PbTiO₃–0.10BaTiO₃ ceramics, which was much higher than those of reported BiFeO₃–PbTiO₃-based and BiFeO₃–BaTiO₃-based ceramics. The temperature stability of the ceramics was also investigated, showing a high resistivity to thermal depoling, with a degradation temperature T_d of ~500 °C. Our results suggested that BF–PT–BT was a good lead-reduced high-temperature ferroelectric ceramics.     

Optical properties of Nd3+ and Er3+ ions in TeO2–WO3–PbO–La2O3 glasses

Multicomponent telluride-tungstate glasses containing Nd³⁺ and Er³⁺ ions were studied experimentally at 77 and 293 K using spectroscopic methods. The Judd–Ofelt intensity parameters were derived from the absorption spectra and used to calculate the radiative lifetimes and branching ratios. The quantum efficiency η = 0.95 of the ⁴F_3/2 level of Nd³⁺ ion is higher than the typical value of other tellurite-based glasses. For low concentration of Er³⁺ ions, the luminescence decay of the ⁴S_3/2 and ⁴I_11/2 levels is governed by radiative transitions and multiphonon relaxation involving the Te-O highest energy vibrations.     

Microstructure and mechanical properties of as aged Mg–3Sn–1Al and Mg–3Sn–2Zn–1Al alloy

Effect of Zn on the microstructure, age hardening response and mechanical properties of Mg–3Sn–1Al alloy which is immediately aged at 180°C after extrusion process (T5) was investigated. It was found that the Zn can refine the microstructure, remarkably improve the aging response with the peak hardness increases to 75 HV and the time to peak hardness reduces from ～110 to ～60 h, which is attributed to the solid solution hardening of Al, Zn and an amount of finer Mg₂Sn precipitates. The as aged Mg–3Sn–2Zn–1Al alloy exhibits better mechanical property at room temperature or 150°C than that of Mg–3Sn–1Al alloy, which is ascribed to the fine grained microstructure and thermally stable Mg₂Sn particles dispersed at grain boundaries and in the matrix.     

Phase transition behavior and high piezoelectric properties in lead-free BaTiO3–CaTiO3–BaHfO3 ceramics

The transition behavior, structural changes, and electric properties of lead-free (1?x)Ba(Hf_0.16Ti_0.84)O₃ –x(Ba_0.70Ca_0.30)TiO₃ (BCHT) ceramics fabricated by the conventional solid-state reaction method are investigated in this study. A complete phase diagram of BCHT system has been proposed based on their dielectric behavior. It is found that BHCT ceramics undergo a complicated phase evolution, driven by Ca and Hf contents. The results clearly demonstrate that high electric properties are achieved in the ferroelectric orthorhombic–tetragonal phase boundary near the composition with x = 0.48, which could be adjusted by the contents of Ca and Hf in the composition. The optimum composition shows enhanced properties with dielectric constant ε _r = 2889 (at room temperature, 1 kHz), high piezoelectric coefficient d ₃₃ = 410 pC/N, and electromechanical coupling factor k _p = 0.47, and a relative high Curie temperature of 106 °C. This investigation yields a sight to understand different phase transition mechanisms of enhanced piezoelectricity for the system.     

Dielectric and electrical energy storage properties of BiFeO3–BaTiO3–SrTiO3 ternary bulk ceramics

Journal of Materials Science: Materials in Electronics - Recently, it is shown that the thin films of BiFeO3–BaTiO3–SrTiO3 have ultrahigh-energy storage density. However, the energy...     

Electrochemical behaviour of Ti–25Nb–3Mo–3Zr–2Sn biomedical alloy in different simulated physiological environments

The electrochemical corrosion behaviour of biomedical Ti–25Nb–3Mo–3Zr-2Sn (TLM) alloy was investigated in various simulated body fluids at 37±0·5°C utilising potentiodynamic polarisation and current–time curves. The Ti–6Al–4V (TC4) alloy was also investigated to make a comparison. The different simulated body fluids comprised of 0·9%NaCl saline, Hank’s and Ringer’s solution were employed. The effect of heat treatment on the electrochemical behaviour of the TLM alloy was also considered. It was discovered that all the test specimens were passivated once immersed into the simulated body fluids. It was also found that the TLM alloy has poorer corrosion resistance in Hank’s solution, due to the chemical composition of the Hank’s. After different heat treated, the TLM alloy had different phases and microstructure, and the corrosion behaviour of the TLM alloy was different. In this study, after the heat treatment of 760°C/1 h/AC+550°C/6 h/AC, the TLM alloy had better corrosion resistance. Owing to the corrosion resistance of the TLM alloy was influenced by numerous factors, such as microstructure and the chemical composition of electrolyte, the corrosion behaviour of the TLM alloy is complex. By comparing with the corrosion behaviour of the TC4 alloy, the TLM alloy has poorer corrosion resistant than the TC4 alloy under the same conditions. But the current–time curves of the TLM alloy were more stable than these of the TC4 alloy with further experiments, because of the more passivation film on the surface of the TLM alloy.     

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.     

Characterization of SiO2–Na2O–Fe2O 3–CaO–P2O 5–B 2O 3 glass ceramics

Bioactivity and magnetic properties were investigated in glass and glass ceramics based on the SiO₂–Na₂O–Fe₂O₃–CaO–P₂O₅–B₂O₃ system to find their suitability as thermoseed for hyperthermia treatment of cancer. The effect of change in compositions on bioactivity was examined in simulated body fluids. The glass ceramic samples exhibit Na₃CaSi₃O₈ and Na_3-XFe_XPO₄ phases. After dipping the glass ceramic samples in simulated body fluids silica hydrogel first forms, followed by an amorphous calcium phosphate layer. Magnetic and microwave resonance experiments further demonstrate the potential of these glass ceramics for possible use in hyperthermia.     

Optical,thermal and radiation shielding properties of B2O3–NaF–PbO–BaO–La2O3 glasses

Journal of Materials Science: Materials in Electronics - The techniques of melt-quenching have been used to generate 53B2O3—2NaF—27PbO – $$(20-x)$$...     

Electrical conductivity studies of Bi2O3–Li2O–ZnO–B2O3 glasses

Ac conductivity measurements and its analysis has been performed on xBi₂O₃–(65?x)Li₂O–20ZnO–15B₂O₃ (0 ≤ x ≤ 20) glasses in the temperature range 30–300 °C and a frequency range of 100 Hz to 1 MHz. The dc conductivity increased and the activation energy decreased with lithium content. The frequency dependent conductivity has been analyzed employing conductivity and modulus formalisms. The onset of conductivity relaxation shifts towards higher frequencies with temperature. The Almond–West conductivity formalism is used to explain the scaling behavior, and the relaxation mechanism is independent of temperature.     

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.     

Processing maps for Fe–24Ni–11Cr–3Ti–1Mo superalloy

Hot deformation characteristics of a Fe-base superalloy were studied at various temperatures from 1000–1200°C under strain rates from 0·001–1 s^− 1 using hot compression tests. Processing maps for hot working are developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate and interpreted by a dynamic materials model. Hot deformation equation was given to characterize the dependence of peak stress on deformation temperature and strain rate. Hot deformation apparent activation energy of the Fe–24Ni–11Cr–1Mo–3Ti superalloy was determined to be about 499 kJ/mol. The processing maps obtained in a strain range of 0·1–0·7 were essentially similar, indicating that strain has no significant influence on it. The processing maps exhibited a clear domain with a maximum of about 40–48% at about 1150°C and 0·001 s^− 1.     

Improved mechanical properties of Ti–15V–3Cr–3Sn–3Al alloy by electron beam welding process plus heat treatments and its microstructure evolution

Electron beam welding (EBW) and related heat treatments were carried out on Ti–15V–3Cr–3Sn–3Al (Ti-15-3) alloy plate materials. It was found that the operated parameters in the present EBW process together with suitable heat treatments significantly enhanced the mechanical properties as well as the elongations of the Ti-15-3 weldment, which may provide a promising way for further industrial application. Furthermore, the observed nano size phase of β, α, and here first reported TiCr₂ particle, may form from the solid solution matrix of the Ti-15-3 alloy. The possible mechanisms for these phase formation are discussed.     

Electrochemical Properties of Nitride Phases in the Si3N4–Ca3N2and Si3N4–AlN–Ca3N2Systems

The electrical conductivity of silicon nitride and its solid solutions with calcium nitride and aluminum nitride was measured in the ranges 400–900 and 1000–1300°C. The conduction mechanisms were found to be substantially different in these temperature ranges. The Si₃N₄–Ca₃N₂solid solutions exhibited high ionic conductivity between 400 and 900°C. The densest and most oxidation-resistant materials were obtained in the Si₃N₄–AlN–Ca₃N₂system (Al introduced as fine powder and then nitrided).     

High-Pressure Reactions in the CeCo3–H2 and GdNi3–H2Systems

Reactions in the CeCo₃–H₂and GdNi₃–H₂systems were studied at hydrogen pressures of up to 0.2 GPa. Using hydrogen absorption–desorption isotherms, the compositions of the high-pressure hydrides were determined to be CeCo₃H_6.8(–70°C) and GdNi₃H_5.1(–50°C). According to x-ray diffraction studies, high-pressure hydrogen absorption to above the stoichiometry CeCo₃H₄is accompanied by insignificant volume changes. In the GdNi₃–H₂system, the hydride phase amorphizes at high hydrogen contents.     

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).