Phase diagrams of binary systems: AgNO3KNO3 and AgNO3 -@#@ NaNO3

AgNO₃-KNO₃ and AgNO₃-NaNO₃ phase diagrams were drawn using a simultaneous thermal analysis technique in the range 373 to 623 K. The apparatus is described briefly. Figure 1 shows a continuous solid solution in equilibrium with the liquid phase. It exhibits a eutectoid mixture (20 mol% NaNO₃) at 380.7 K. Figure 2 shows a eutectic mixture (45 mol % KNO₃) at 413 K, a eutectoid mixture (20 mol % KNO₃) at 409 K, and a continuous invariant at 404 K.     

Thermodynamic evaluation of phase equilibria in NaNO3-KNO3 system

The binary phase diagram of NaNO₃-KNO₃ was studied by differential scanning calorimetry (DSC) and high-temperature x-ray diffractometry. The solid solutions in the intermediate concentration phase appeared to be a mixture of the NaNO₃-based solid solutions and KNO₃-based solid solutions. This behavior below the solidus suggests that NaNO₃-KNO₃ might well be regarded as a system with limited solid solubilities instead of a continuous series of solid solutions. The temperatures for the solidus and liquidus have been determined with consideration of limited terminal solid solutions. Two models, the Henrian solution and regular solution theory for NaNO₃-based phase and the KNO₃-based phase, respectively, were used to reproduce the solidus and liquidus of the phase diagram. The results are in good agreement with the DSC data. The thermodynamic properties for the NaNO₃-based and KNO₃-based solid solutions have been derived from an optimization procedure using the experimental data. The calculated phase diagram and optimized thermodynamic parameters are thermodynamically self-consistent. Thus, the limited solid solution model seems to be more consistent with the phase diagram obtained by DSC than the continuous solid solution model.     

Thermodynamic evaluation of phase equilibria in NaNO3-KNO3 system

The binary phase diagram of NaNO₃-KNO₃ was studied by differential scanning calorimetry (DSC) and high-temperature x-ray diffractometry. The solid solutions in the intermediate concentration phase appeared to be a mixture of the NaNO₃-based solid solutions and KNO₃-based solid solutions. This behavior below the solidus suggests that NaNO₃-KNO₃ might well be regarded as a system with limited solid solubilities instead of a continuous series of solid solutions. The temperatures for the solidus and liquidus have been determined with consideration of limited terminal solid solutions. Two models, the Henrian solution and regular solution theory for NaNO₃-based phase and the KNO₃-based phase, respectively, were used to reproduce the solidus and liquidus of the phase diagram. The results are in good agreement with the DSC data. The thermodynamic properties for the NaNO₃-based and KNO₃-based solid solutions have been derived from an optimization procedure using the experimental data. The calculated phase diagram and optimized thermodynamic parameters are thermodynamically self-consistent. Thus, the limited solid solution model seems to be more consistent with the phase diagram obtained by DSC than the continuous solid solution model.     

Effect of continuous cooling on the decomposition processes in a Zn–1.6 wt.% Al alloy

The decomposition processes in a two-phase Zn–1.6 wt.% Al alloy, homogenized and quenched to room temperature through continuous cooling (1.5 K min⁻¹), have been studied by scanning electron microscopy. At the beginning of cooling, continuous precipitates were formed at grain boundaries and in grain interiors (α₀ phase, Zn-rich solid solution), with simultaneous eutectoid decomposition of non- stoichiometric intermetallic ZnAl (β phase). As the cooling proceeded, the density of continuous precipitates at grain boundaries and in grain interiors increased and at the same time the coarsening of eutectoid phase initiated. Although some precipitates at grain boundaries have grown by a ‘pucker mechanism', the occurrence of discontinuous precipitation was not observed during cooling. After a long period of aging, however, discontinuous precipitation cells were formed through basically two stages: (a) precipitation of a metastable Al-rich phase on the continuous precipitates formed at grain boundaries and (b) nucleation and growth of discontinuous precipitation cells within the metastable Al-rich phase.     

Zum Einfluß der Gefügeausbildung auf das Korrosionsverhalten von Aluminiumbronzen in Kochsalzlösung

Influence of the structure on the corrosion behaviour of aluminium bronzes in sodium chloride solution The influecne of various structural components and their distribution on the corrosion behaviour of binary and complex aluminium bronzes (cast INOXYDA alloys) in a 3% solution of sodium chloride has been investigated qualitatively and quantitatively. Corrosion tests were carried out over a period of 850 h and are interpreted on the basis of single phase properties. The corrosion resistacne of binary and INOXYDA 3 type alloys is markedly decreased if even small amounts of y₂ phase are precipitated in a continuous manner. The occurance of this constituent causes an intense and dangereous dealuminisation reaction. The eutectoid mixture (α + y₂) is always less corrosion resistant than corresponding martensitic structures. While the corrosion behaviour of these alloys is strongly influenced by heat treatment a far less pronounced effect is observed with alloys containing Fe and Ni (type INOXYDA 53 or 90). This is directly related to the fact that precipitation of y₂ is prevented by the addition of Fe and especially of Ni. Such alloys are mainly composed of Ni. Such alloys are mainly composed of α and passive Fe- and Ni-rich K phase. If retained martensite or y₂ are present in addition to the mentioned phases (e.g. in the as cast condition) corrosion resistance is decreased. Appropriate heat treatment results in plain (α + K) structures while simultaneously segregations at α/K grain boundaries disappear and corrosion resistance is improved.     

Fabrication and characterization of functionalized wet-chemical silver coated films on glass for optical systems

A method for fabricating an Ag coated beam splitter is reported. This shows a specific patterned transmittance by immersing glass substrates in a mixture of H₂SO₄ and H₂O₂ to make negatively charged oxygen sites at the silica surface and then in ethanolic solutions of AgNO₃ and butylamine. We controlled the soaking time and molar ratios of the mixture of AgNO₃ and butylamine to a pattern % transmittance of electroless coated glass surface. Finally, we made a functionalized beam splitter showing step function like transmittance and applied this to make multiple laser beams for display and laser machinings.     

Kinetics of isothermal decomposition in polycrystalline β CuAlBe alloys

The kinetics of the microstructural evolution of the metastable β phase during isothermal aging in a Cu–22.60Al–3.26Be (at%) polycrystalline shape memory alloy has been studied by electrical resistivity measurements and microscopical examinations. With an isothermal treatment at around 820 K, the alloy rapidly decomposes into γ₂ phase with dendritic morphology, while between 670 K and 760 K the formation of α′ phase followed by the eutectoid decomposition is observed. A TTT diagram was estimated and the stability boundaries of the β phase in the studied alloy were compared with those of other Cu-based shape memory alloys.     

Mechanical properties of dual multi-phase single-crystal intermetallic alloy composed of geometrically close packed Ni3X (X: Al and V) type structures

Dual multi-phase intermetallic alloy, which is composed of Ni₃Al(L1₂) and Ni solid solution (A1) phases at high-temperature annealing and is additionally refined by a eutectoid reaction at low temperature aging, according to which the Al phase is transformed into the Ni₃Al(L1₂) + Ni₃V(DO₂₂) phases, was prepared based on the pseudo-ternary system Ni₃Al–Ni₃Ti–Ni₃V. The high-temperature tensile deformation, fracture behavior and tensile creep were investigated using single crystalline material. The alloy with such a novel microstructure shows extremely high yield and tensile strength with good temperature retention, when compared not only with conventional Ni-based superalloys but also with polycrystalline materials reported previously. Over a broad temperature range fracture occurred along octahedral plane in the major component L1₂ phase, accompanied with high tensile elongation and ductile fracture mode. The tensile creep test conducted at 1173 K and 1223 K showed the presence of threshold stress, and also extremely low creep rate and long creep rupture time when compared with conventional Ni-based superalloys. The obtained results are promising for the development of a new-type of high-temperature structural material.     

The Mechanism of Phase Transformation in Thermally-Grown FeO Scale Formed on Pure-Fe in Air

The isothermal phase transformation behavior of thermally grown oxide scale of FeO, which was formed on Fe at 700 °C in air for 16 min, was investigated at 320, 450, 500, 520, and 560 °C in air. The phase transformation of FeO was found to consist of four transformation modes: (1) growth of outer Fe₃O₄ layer; (2) precipitation of Fe₃O₄; (3) formation of magnetite seam; and (4) eutectoid decomposition of FeO. The transformation was always completed by the eutectoid decomposition at all temperatures in the present study; however, the proportion of transformation mode (1) and (2) strongly depended on temperature. At higher temperatures growth of the outer Fe₃O₄ layer initially predominates, but the precipitation of Fe₃O₄ controls the initial transformation at lower temperature before the eutectoid reaction. The eutectoid reaction was found to be initiated by Fe nucleation from Fe-saturated FeO. Fe saturation in FeO was due to growth and/or precipitation of Fe₃O₄ and formation of the magnetite seam layer, which acts as a diffusion barrier for Fe inward diffusion into Fe substrate. It was proposed that these transformation modes, growth and/or precipitation of Fe₃O₄ and magnetite seam formation, are necessary to begin the eutectoid reaction, i.e., completion of FeO scale transformation.     

Microstructural evolution and phase transition dependent on annealing temperature and carbon content for LaFe11.5Si1.5Cx compounds prepared by arc-melting

Three different parts of LaFe_11.5Si_1.5C_x(x = 0, 0.1, 0.2, 1.0) ingots prepared by arc-melting were determined. The region of the sample close to the surface towards the arc was marked as part 1 and the region of the sample close to the water jacketed copper crucible was marked as part 3. Without affecting the microstructure of part 1, carbon doping could increase the amount of 1:13 phase of the LaFe_11.5Si_1.5C_x(x = 0, 0.1, 0.2) ingots, which mainly existed in the part 3. The DSC curves of part 1 of LaFe_11.5Si_1.5C_x(x = 0, 0.2) ingots show a peak at 1445 K moved to 1402 K after carbon doping. The eutectoid reaction: LaFeSi → 1:13 phase + La₅Si₃ is believed to be around the peak. After annealing at 1353 K, 1443 K and 1473 K for 6 h, the microstructure of LaFe_11.5Si_1.5C_x(x = 0, 0.1, 0.2) compounds was investigated. Too high annealing temperature could induce the formation of La₅Si₃ phase and even the growth of α-Fe. The best annealing temperature should be slightly lower than the eutectoid reaction temperature, even if larger atomic diffusion rate can be obtained at higher temperature. Carbon doping could reduce the eutectoid reaction temperature. Energy can be saved for a low annealing temperature. In addition, carbon doping can accelerate the formation of the 1:13 phase by improving the nucleation rate.     

A eutectoid phase transformation for the primary intermetallic particle from Alm(Fe,Mn) to Al3(Fe,Mn) in AA5182 alloy

The size and morphology evolution of the primary intermetallic particles in a DC-cast AA5182 alloy during homogenization at 470 and 520 °C has been studied. A eutectoid phase transformation of the primary particles Al_m(Fe,Mn) → Al₃(Fe,Mn) + Al is observed by field emission gun scanning electron microscopy (FEG-SEM) and transmission electron microscopy (TEM). After the transformation, Al_m(Fe,Mn) particles become a lamellar mixture of Al₃(Fe,Mn) and Al, which is believed to be beneficial to the break-up of the large primary particles during hot rolling. The transformation mechanism and the transformation kinetics have been studied. During isothermal treatment at 520 °C, the fractional transformation rate is mainly controlled by nucleation. At 470 °C, the phase transformation is controlled by both nucleation and growth of Al₃(Fe,Mn) in Al_m(Fe,Mn) phase.     

Solubility of YbTe in Sb2Te3 and thermodynamic properties of the solid solution

The solubility of YbTe in Sb₂Te₃ is investigated by a combination of DTA, XRD, SEM, and EMF methods. The fragment of the T-x phase diagram of the YbTe-Sb₂Te₃ system is constructed for 0-25 mol.% YbTe. It is shown that the solubility limit for YbTe in Sb₂Te₃ is achieved at 15 mol.% YbTe at 300 K and at 17.5 mol.% YbTe at 855 K. From the EMF measurements with an YbTe electrode the partial thermodynamic functions of the YbTe pseudo-component are calculated for the alloys of different compositions. Also, the standard integral thermodynamic functions of the YbTe dissolution in Sb₂Te₃ as well as the standard thermodynamic functions of formation and the standard entropy of the solid solution are calculated from the experimental data.     

AgNO<Subscript>3</Subscript>-LiNO<Subscript>3</Subscript>-RbNO<Subscript>3</Subscript> phase diagram

The ternary system of silver, lithium, and rubidium nitrates has been studied. Five vertical sections were established: AgNO₃-Li_0.5Rb_0.5NO₃; Li_0.5Rb_0.5NO₃-Ag_0.5Rb_0.5NO₃; 20 mol% AgNO₃; 80 mol% AgNO₃; and the section 5 mol% LiNO₃. Ten invariant points were found. A schematic representation of ternary equilibria is given. The three binary systems are also reported.     

The influence of moisture on the oxidation rate of iron in NaNO3 and KNO3 melts

The open circuit potential (E_corr) and oxidation rate (I_corr) of iron were measured in dry and wet NaNO₃ and KNO₃ melts at 340 °C. A shift of E_corr in the positive direction and a higher oxidation rate were observed in wet melts in comparison with dry melts. The oxidation rate was almost 55% higher in KNO₃ melts than in NaNO₃ melts. To ascertain the effect of moisture on the cathodic reaction, a cyclic voltammetry study was carried out on platinum surface in dry and wet conditions of the melt. An increase of cathodic current in the presence of moisture in the melt is in good agreement with the increased oxidation rate of iron. A proportionate increase of oxidation rate was also noted in wet NaNO₃ and KNO₃ melts to those in their dry melts.     

Phase diagram of Ni3V-Co3V pseudobinary system

A phase diagram of Ni₃V-Co₃V pseudobinary system is proposed based on x-ray diffraction and differential thermal analysis. Four invariant reactions are located in the phase diagram—two eutectoid and two peritectoid reactions. Six kinds of geometrically close-packed phases are encountered. The stability of these close-packed phases correlate well with the electron concentration.     

Thermal conductivity of Ni3V–Ni3Al pseudo-binary alloys

The effect of changes in the composition and microstructure of the Ni₃V–Ni₃Al pseudo-binary alloys on their thermal conductivity has been investigated. For Ni₃V and Ni₃Al-based single-phase alloys, the thermal conductivity shows a maximum value at the stoichiometric compositions, and it decreases as the V (or Al) content of the Ni₃Al (or Ni₃V) alloy increases, following the Nordheim rule. For Ni₃V–Ni₃Al two-phase alloys, the thermal conductivity of the constituent Ni₃Al phase exhibits a smaller value than that of the Ni₃V phase. Eventually, the thermal conductivity of the two-phase alloys decreases as the Al content increases because of the increase in the volume fraction of the Ni₃Al phase with low conductivity. As the temperature increases from 293 K to 1073 K, the conductivity increases for all of the alloys but not for stoichiometric Ni₃V. However, the dependence of the thermal conductivity on the alloy composition between 293 K and 1073 K is similar. Hence, it is confirmed that the thermal conductivity of the Ni₃V–Ni₃Al pseudo-binary alloys is controlled by the composition and volume fraction of the constituent phase.     

Mechanical properties of Rh-based L12 intermetallic compounds Rh3Ti,Rh3Nb and Rh3Ta

A preliminary study of the mechanical properties of Rh-based L1₂ intermetallic compounds Rh₃Ti, Rh₃Nb and Rh₃Ta is carried out by micro-vickers hardness tests at room temperature and compression tests at various temperatures ranging from room temperature to 1673 K. A cold-rolling test is also conducted on a Rh₃Ti plate. Although high temperature ductility-loss is observed in all compounds, Rh₃Ti shows good ductility at all temperatures investigated. Both Rh₃Nb and Rh₃Ta show a weak positive temperature dependence of strength (stress anomaly) at around 1273 K which is about half the melting point for both intermetallic compounds. The stress anomaly is discussed in terms of a phase stability concept based on the Kear–Wilsdorf (K–W) mechanism. High work hardening rates of Rh₃Nb and Rh₃Ta, which cause high vickers hardness at room temperature, are also attributed to the K–W mechanism.     

Phase diagram of Ni3V-Co3V pseudobinary system

A phase diagram of Ni₃V-Co₃V pseudobinary system is proposed based on x-ray diffraction and differential thermal analysis. Four invariant reactions are located in the phase diagram—two eutectoid and two peritectoid reactions. Six kinds of geometrically close-packed phases are encountered. The stability of these close-packed phases correlate well with the electron concentration.     

Oxide phase development upon high temperature oxidation of γ‐NiCrAl alloys

The amount of each oxide phase developed upon thermal oxidation of a γ‐Ni‐27Cr‐9Al (at.%) alloy at 1353 K and 1443 K and a partial oxygen pressure of 20 kPa is determined with in‐situ high temperature X‐ray Diffractometry (XRD). The XRD results are compared with microstructural observations from Scanning Electron Microscope (SEM) backscattered electron images, and model calculations using a coupled thermodynamic‐kinetic oxidation model. It is shown that for short oxidation times, the oxide scale consists of an outer layer of NiO on top of an intermediate layer of Cr₂O₃ and an inner zone of isolated α‐Al₂O₃ precipitates in the alloy. The amounts of Cr₂O₃ and NiO in the oxide scale attain their maximum values when successively continuous Cr₂O₃ and α‐Al₂O₃ layers are formed. Then a transition from very fast to slow parabolic growth kinetics occurs. During the slow parabolic growth, the total amount of non‐protective oxide phases (i.e. all oxide phases excluding α‐Al₂O₃) in the oxide scale maintain at an approximately constant value. The formation of NiCr₂O₄ and subsequently NiAl₂O₄ happens as a result of solid‐state reactions between the oxide phases within the oxide scale.     

Investigation on the Phase Diagram of LiCl-KCl-NdCl<Subscript>3</Subscript> Pseudo-Ternary System

The ternary phase diagram of LiCl-KCl-NdCl₃ system has been investigated by differential thermal analysis (DTA), followed by characterization of the coexisting phases in the solid state by x-ray diffraction, in order to understand the interactions in the NdCl₃-LiCl-KCl ternary system. The results of these experiments showed that LiCl and K₂NdCl₅ form a non binary join section. This divides the LiCl-KCl-NdCl₃ system into two quasi-ternary sections, namely (1) LiCl-KCl-K₂NdCl₅ and (2) LiCl-K₂NdCl₅-NdCl₃ systems. Both are simple eutectic ternary phase diagrams. The ternary eutectic temperatures and eutectic compositions are determined to be 316?±?3 °C and 53.9 mol.% LiCl-38.7 mol.% KCl-7.4 mol.% K₂NdCl₅ in the LiCl-KCl-K₂NdCl₅ quasi-ternary section, while the other eutectic temperature and composition are determined to be 376?±?9 °C and 46.2 mol.% LiCl-32.5 mol.% K₂NdCl₅-21.3 mol.% NdCl₃ in the LiCl-K₂NdCl₅-NdCl₃ quasi-ternary section. A quasi-ternary peritectic reaction is observed at 37.7 mol.% LiCl-36.2 mol.% KCl-26.1 mol.% K₂NdCl₅ at 445?±?1°C. The primary and secondary crystallization temperatures for the samples are deduced from the heating runs of DTA traces, and the phases responsible for the various thermal events are ascertained. Isothermal sections at chosen temperatures and polythermal liquidus projection with isothermal contours are drawn over the ternary phase field.