Thermodynamic Stabilities of Lanthanum Tungstates Using a Calcium Fluoride Solid Electrolyte Galvanic Cell

Abstract

A knowledge of the thermodynamic stabilities of the lanthanum tungstates measured as the Gibbs energies of formation from the free oxides is important as lanthanum is used as a powerful desulphurizing agent and tungsten as a special alloying element in the production of clean steels and special steels. These data will also be useful as the system La₂O₃ WO₃ can be a model since it exhibits many compounds between the end members. Excepting one EMF work, no information is available in the literature on the thermodynamics of this system. This system exhibits the compounds 5 La₂O₃·22 WO₃, La₂ O₃ · 3 WO₃, La₂O · 2 WO₃, 7 La₂O₃ · 8 WO₃,La₂O · WO₃, 3 La₂O₃ · 2 WO₃ and 5 La₂O₃ · 2 WO₃. The compounds were prepared from reagent grade free oxides by solid state sintering at high temperature followed by X-ray diffraction. The standard Gibbs energies of formation of the compounds from the free oxides were determined by operating the following galvanic cells with calcium fluoride as solid electrolyte.

O₂(g), Pt/ La₂O₃ · LaOF// CaF₂/ / 5 La₂O₃ · 22 WO₃, WO₃, LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂//5 La₂O₃ · 22 WO₃, La₂O₃ · 3 WO₃, LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂// La₂O₃ · 3 WO₃, La₂O₃ · 2 WO₃ LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂// La₂O₃ · 2 WO₃, 7 La₂O₃ · 8 WO₃, LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂//La₂O₃ · WO₃, 3La₂O₃ · 2 WO₃ LaOF/Pt, O₂(g)

O₂(g), Pt/La₂O₃ · LaOF//CaF₂//3 La₂O₃ · 2 WO₃, 5La₂O₃ · 2 WO₃ LaOF/Pt, O₂(g)

O₂(g), Pt/ La₂O₃ LaOF// CaF₂/ / 3 La₂O₃2 WO₃, La₂O₃, 2 WO₃ LaOF/Pt, O₂(g)

Stable, reproducible EMFs were obtained in the temperature range 1123 to 1273 K. The net cell reactions are respectively as follows:

5 La₂O₃ + 22 WO₃ = 5 La₂O₃ · 22 WO₃

7 La₂O₃ + 3 (5 La₂O₃ · 22 WO₃) = 22 (La₂O₃ · 3 WO₃)

La₂O₃ + 2 (La₂O₃ · 3 WO₃) = 3 (La₂O₃ · 2 WO₃)

3 La₂O₃ + 4 (La₂O₃) = 7 La₂O₃ · 8 WO₃

La₂O₃ + 7 La₂O₃ · 8 WO₃ = 8 (La₂O₃ · WO₃)

La₂O₃ + 2 (La₂O₃ · WO₃) = 3 La₂O₃ · 2 WO₃

2 La₂O₃ + 3 La₂O₃ · 2 WO₃ = 5 La₂O₃ · 2 WO₃

The standard Gibbs energies of formation of the different lanthanum tungstates are then calculated by appropriately combining from the above cell reactions and their Gibbs energy changes obtained from the experimental EMF data. The present data are discussed in the light of EMF data reported in the literature for WO₃-rich compounds in the system.     

Influence of the mechanical activation of REE oxides on the electrical conductivity of borate melts

The influence of the mechanical activation of oxides M₂O₃ (La₂O₃, Ce₂O₃, Nd₂O₃, Sm₂O₃, Eu₂O₃, Gd₂O₃, Tb₂O₃, Dy₂O₃, Ho₂O₃, Er₂O₃, Yb₂O₃, and Lu₂O₃) on electrical conductivity (æ) of the B₂O₃-M₂O₃ molten systems is investigated. It is assumed that the majority carriers in these melts can be protons which enter the melts due to the hydration of B₂O₃. The variation in the magnitude of for various M₂O₃ contents is explained by the corresponding variation in the structure of structural units as a result of the dissociation of the boron-oxygen groups, which include the OH groups. The activation energy of electrical conductivity in the B₂O₃-M₂O₃ melts increases due to the decay of superstructural units [B₃O_4.5] and B₃O₃O_3/2OH as the temperature increases. The dependence of is found. In the B₂O₃-La₂O₃ → B₂O₃-Lu₂O₃ melts series, this energy follows the intraseries periodicity, which depends on the stabilization energy of fundamental terms of the ions of rare-earth elements (REE).     

Experimental study of phase equilibria in the PbO-Al2O3-SiO2 system

Equilibrium phase relations in the PbO-Al₂O₃-SiO₂ system have been investigated experimentally by means of high-temperature equilibration, quenching, and electron probe X-ray microanalysis (EPMA). The system has 21 primary phase fields including three monoxides (PbO, Al₂O₃, and SiO₂), seven binary compounds (Al₆Si₂O₁₃, PbAl₂O₄, PbAl₁₂O₁₉, Pb₂Al₂O₅, PbSiO₃, Pb₂SiO₄, and Pb₄SiO₆), and eleven ternary compounds (PbAl₂Si₂O₈, Pb₃Al₁₀SiO₂₀, Pb₄Al₂Si₂O₁₁, Pb₄Al₄SiO₁₂, Pb₄Al₄Si₃O₁₆, Pb₄Al₄Si₅O₂₀, Pb₅Al₂Si₁₀O₂₈, Pb₆Al₂Si₆O₂₁, Pb₈Al₂Si₄O₁₉, Pb₁₂Al₂Si₁₇O₄₉, and Pb₁₂Al₂Si₂₀O₅₅). Three new ternary compounds, Pb₄Al₄SiO₁₂, Pb₄Al₄Si₅O₂₀, and Pb₁₂Al₂Si₁₇O₄₉, were observed and characterized by EPMA. No extensive solid solution in any of the compounds was found in the present study. The liquidus isotherms were experimentally determined in most of the primary phase fields in the temperature range from 923 to 1873 K, and the ternary phase diagram of the PbO-Al₂O₃-SiO₂ system has been constructed.     

Refrigeration effect of La（FeCoSi）13B0.25 compounds and gadolinium metal in reciprocating magnetic refrigerator

The LaFe11.9–x Cox Si1.1 B0.25 with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1 B0.25 and Gd particles were tested on the reciprocating refrigerator at the same condition in order to compare the cooling capacity of the two materials.The results showed that the cooling velocity of Gd was obviously higher than that of LaFe11.9–x Cox Si1.1 B0.25.The maximum temperature span was 12.7 oC for LaFe11.0 Co0.9 Si1.1 B0.25,14.9 oC for Gd metal whose mass is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25,8.1 oC for Gd metal whose volume is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25.Series connection of LaFe11.0 Co0.9 Si1.1 B0.25 and LaFe11.08 Co0.82 Si1.1 B0.25 had the maximum cooling temperature span of 15.3 oC.     

Superconductivity and magnetism of complex rhodium borides

A number of complex rhodium borides with an LuRu₄B₄-type structure is synthesized; these are DyRh₄B₄ (samples HP) with T _c ≈ 4.5 K, DyRh_3.8Ru_0.2B₄ (samples AM) with T _c ≈ 4.5 K, Dy_0.8Er_0.2Rh_3.8Ru_0.2B₄ (samples AM) with T _c ≈ 6.3 K, and HoRh_3.8Ru_0.2B₄ (samples AM) with T _c ≈ 6.0 K. The temperature dependence of upper critical field B _c2(T) for all the samples under study exhibits an anomalous behavior. In all cases, the curve B _c2(T) demonstrates a point of inflection, after which the curve deviates from the classical parabolic law abruptly upward for DyRh₄B₄ and DyRh_3.8Ru_0.2B₄ (the 1st group of compounds) and downward for the Dy_0.8Er_0.2Rh_3.8Ru_0.2B₄ and HoRh_3.8Ru_0.2B₄ compounds (the 2nd group). These compounds are found to be characterized by of the following phase transitions: paramagnet → ferrimagnet → superconductor (retained ferrimagnetism) → antiferromagnet (retained superconductivity). The latter transition to the antiferromagnetic state occurs only in the compounds of the 1st group. It is found that, for the DyRh_3.8Ru_0.2B₄ compound, no traditional Meissner effect is observed but the so-called Volleben effect (paramagnetic Meissner effect) takes place.     

The Sulphation of Tricobalt Tetroxide and Nickel Monoxide with Fused Sodium Hydrogen Sulphate

Abstract

The results of differential thermal, X-ray powder diffraction analyses and thermogravimetric analyses have heen used to identify the reactions that occur when NaHSO₄ is heated between 150°C and 400°C with NiO and with Co₃O₄. The initial reactions occur on fusion of NaHSO₄ and produce monohydrated sulphates Ni and Co, Na₂SO₄ and Na₃H(SO₄)₂. The Na₃H(SO₄)₂ decomposes to Na₂SO₄ and Na₂S₂SO₇ at higher temperature NiSO₄·H₂O reacts with Na₂SO₄, forming NiSO₄·Na₂SO₄, H₂O, which subsequently dehydrates; but CoSO₄·H₂O dehydrates before reaction occurs to produce-CoSO₄·Na₂SO₄.     

Effect of C on Phase Evolution,Microstructure, and Magnetic Properties of Pr2Fe14B-Type Nanocomposites

The phase evolution, microstructure and magnetic properties of melt-spun Pr-rich Pr₁₁Fe_bal.B_8-yC_y (y = 0–8) and Pr-lean Pr₉Fe_bal.Ti_xB_11–yC_y (x = 0, 2.5 and 4; y = 0–11) ribbons have been investigated intensively. A slight substitution of C for B (y=2) was proven to be effective in improving the magnetic properties of Pr-rich Pr₁₁Fe_bal.B_8–yC_y nanocomposites. C atoms prefers to enter 2:14:1 phase in forming Pr₂Fe₁₄(B, C). But the volume fraction of Pr₂Fe₁₇C_z, α-Fe and 1:2 carbide increases, due to the dissociation of 2:14:1 phase and the suppression of Fe₃B phase, with further increase of carbon content. The optimal magnetic properties of B_r = 9.4 kG, _iH_c = 9.3 kOe, and (BH)_max = 17.3 MGOe were obtained for Pr₁₁Fe_bal.B₆C₂. In contrast, the increase of C substitution in Pr₉Fe_bal.Ti_2.5B_11–yC_y (y=0–11) ribbons degrades the B_r, _iH_c, and (BH)_max monotonically, which is arisen from the increase of vol % of Pr₂Fe₁₇C_z and α-Fe phases, and the rapid decrease of 2:14:1 phase. In comparison with those of Pr₉Fe_bal.B_11–yC_y (y=0–5.5) ribbons, improved magnetic properties of (BH)_max=15.3–17.8 MGOe with higher coercivity of _iH_c=9.7–10.8 kOe have been obtained in Ti-containing Pr₉Fe_bal.Ti_2.5B_11–yC_y (y=0–5.5) ribbons. However, in higher Ti concentration Pr₉Fe_bal.Ti₄B_11–yC_y, ribbons, a slight substitution of C for B (y = 0.5–1) is beneficial in improving the coercivity and magnetic energy product, simultaneously. The optimal properties of B_r = 9.4 kG, _iH_c = 11.1 kOe, (BH)_max = 18.0 MGOe and α = −0.146 %/°C, β = −0.576 %/°C were achieved in Pr₉Fe_bal.Ti₄B_10.5C_0.5 nanocomposites.     

Energy transfer,superior thermal stability and multi-color emitting properties of langbeinite-type solid-solution phosphor K_2Dy_(1.5-x)Eu_xTa_(0.5)(PO_4)_3

Langbeinite type compounds are a large kind of oxometallate with good flexibility structure.Herein,we synthesized a new langbeinite type compound K_2 Dy_(1.5)Ta_(0.5)(PO_4)_3,in which the Dy~(3+) and Ta~(5+) were blended to occupy the same crystallographic sites.Simultaneously,solid solutions of K_2 Dy_(1.5)_(-x)Eu_xTa_(0.5)(PO_4)_3(x=0-1.5) were prepared and their photoluminescence properties were investigated.Due to energy transfer from Dy~(3+) to Eu~(3+),both Dy~(3+) and Eu~(3+) characteristic emissions are observed under 393 nm light excitation.The emitting color of K_2 Dy_(1.5-x)Eu_xTa_(0.5)(PO_4)_3 turns from green through yellow to red by simply adjusting the Eu~(3+) concentration from 0 to 0.4.Moreover,K_2 Dy_(1.48)Eu_(0.02)Ta_(0.5)(PO_4)_3 phosphor possesses excellent fluorescence thermal stability and exhibits zero thermal quenching at 150 ℃.These results manifest that K_2 Dy_(1.5-x)Eu_xTa_(0.5)(PO_4)_3 solutions are promising multi-color emitting phosphors candidate for near-UV LED.     

Amorphous forming ranges of Al-Fe-Nd-Zr system predicted by Miedema and geometrical models

A method based on the semi-empirical Miedema model and a geometrical model was used to study the glass forming abilities(GFA) and the amorphous forming ranges of Al-Fe-Nd-Zr system and its constituent ternary systems.The amorphous forming composition ranges were analyzed based on different criteria such as ΔGam-ss and PHSS(PHSS=ΔHchem(ΔSC/R)(ΔSσ/R)) for Al-Fe-Nd system.The predicted amorphous forming range was in good agreement with the experimental results.The results showed that the criterion of ΔGam-ss was more accurate,and agreed well with the experiment results.The Gibbs free energy difference ΔGam-ss and parameter PHSS were then used to predict the amorphous forming composition range for the rest of the constitutive ternary systems of Al-Fe-Nd-Zr.In addition,the amorphous forming composition ranges of the(Al-Fe-Zr)100–x Ndx(x=50,60,70) systems were predicted by ΔGam-ss and the modified parameter PHSS.The Gibbs free energy of Al10(Fe1–x Zrx)30Nd60 were also calculated.The GFA parameter PHSS indicated that the composition with the highest GFA was Al33.5Fe13.5Zr3Nd50 for the(Al-Fe-Zr)50Nd50 system,Al28.8Fe10Zr1.2Nd60for the(Al-Fe-Zr)40Nd60 system and Al22.8Fe6.9Zr0.3Nd70 for the(Al-Fe-Zr)30Nd70 system,and the results suggested that those alloys with high content of Al had higher GFA.The appropriate content of neodymium and zirconium resulted in the lower value of PHSS and increased the GFA obviously.     

Properties investigation of CaO–Al2O3–SiO2–Li2O–B2O3–Ce2O3 mould flux with different w(CaO)/w(Al2O3) for heat-resistant steel continuous casting

The new CaO–Al₂O₃–SiO₂–Li₂O–B₂O₃–Ce₂O₃ mould flux was devised to realise smooth continuous casting of Ce-bearing heat-resistant steel. The new devised mould flux was based on calcium-aluminate system, so the w(CaO)/w(Al₂O₃) has great influence on the properties of the slag, which is similar to the basicity in the silicate system. The melting temperature, viscous properties, slag structure and crystalline phases with different w(CaO)/w(Al₂O₃) were investigated. The melting temperature of the mould flux could remain relatively steady with w(CaO)/w(Al₂O₃) in the range of 1.0–1.82. The main network former in the new slag was [AlO₄]-tetrahedron. The network formed by [AlO₄]-tetrahedron was destroyed by increasing w(CaO)/w(Al₂O₃), the viscosity decreased consequently. The mould flux show weaker crystallisation tendency with increasing w(CaO)/w(Al₂O₃). When the temperature decreased to 1100°C, the change of the fully crystallised phases with increasing w(CaO)/w(Al₂O₃) was as follows: Li₂O·Al₂O_3?+?2CaO·Al₂O₃·SiO_2?→?Li₂O·Al₂O_3?→?Li₂O·Al₂O_3?+?3CaO·Al₂O_3?+?CaCeAlO₄.     

Chemical potentials of oxygen for three-phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt

By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO₂ mixture as reference electrode, the equilibrium oxygen partial pressures for three-phase assemblages of CaSiO₃(s) + Ca₃Si₂O₇(s) + {CaO + SiO₂ + Fe_xO} melt and Ca₃Si₂O₇(s) + Ca₂SiO₄(s) + {CaO + SiO₂ + Fe_xO} melt were determined as: - log {P_O2 (CS + C₃S₂ + L)/bar} = - 3.22 13000/(T/K) ± 0.05 - log {P_O2 (C₃S₂ + C₂S + L)/bar} = - 0.92 16400/ (T/K) ± 0.04. respectively, where CS, C₃S₂ and C₂S indicate CaSiO₃(s), Ca₃Si₂O₇(s). and Ca₂SiO₄(s), respectively.     

Effective regulation of electronic structures and luminescence properties of LiGd9(SiO4)6-x(GeO4)xO2:Dy3+ phosphors by tetrahedral substitution

A series of Dy³⁺-activated phosphors with the general formula LiGd₉(SiO₄)_6-x(GeO₄)_xO₂:Dy₃₊(0 ≤ x≤ 3)characterized by an apatite-type structure were successfully synthesized via a simple solid-state technique involving a partial substitution of [SiO₄]^4-with [GeO₄]^4- species.The effects of homovalent[GeO₄]^4--[SiO₄]^4- substit...     

Directional phase formation on melting via peritectic reaction

Directional melting and solidification of Ba₂YCu₃O₆₊₈ in low oxygen partial pressures were investigated by the laser-heated floating zone (LHFZ) technique. The following reaction was observed on melting at Po₂ > 8 Pa: Ba₂YCu₃O₆₊₈→ BaY₂CuO₅ + L where BaY₂CuO₅ phase comprised equiaxed particles. At < 8 Pa < Po₂ < 10³ Pa, the preceding reaction occurred, and at higher temperatures, the following reaction also occurred to produce a rodlike BaY₂O₄ phase, oriented in the growth direction: BaY₂Cu0₅ ar BaY₂O₄ + L At pressures below about 8 Pa, the low temperature reaction observed was Ba₂YCu₂O₆₊₈ → BaY₂O₄ + L In this case, the oriented BaY₂O₄ phase formed directly from Ba₂YCu₂O₆₊₈ and was platelike in morphology. Directional growth of the BaY₂O₄ phase from BaY₂CuO₅ was modeled in a simple way. The BaY₂Cu0₅ particles ahead of the BaY₂O₄ interface dissolve in the superheated liquid, and solute transport for BaY₂O₂ growth is assumed to be limited by diffusion along the growth direction over distances equal to half the rod or plate spacing. A relation between supereating at the growth interface and growth rate was derived from the present model. Some possibilities for making use of such aligned structures in the growth of the superconducting compound Ba₂YCu₃O₆₊₈ are discussed.     

In Situ ceramic particle-reinforced aluminum matrix composites fabricated by reaction pressing in the TiO2 (Ti)-Al-B (B2O3) systems

Particulate TiB₂ reinforced aluminum-based metal matrix composites (MMCs) were successfully fabricated by means of the reaction processing method. TiB₂ particulates were formed in situ through the reaction of Ti and B in Ti-Al-B, TiO₂ and B in TiO₂-Al-B, and TiO₂ and B₂O₃ in TiO₂-Al-B₂O₃ systems. The results showed that in situ TiB₂ particulates formed in the Ti-Al-B system had a size of 5 μm and they exhibited block and rodlike structures. Moreover, coarse Al₃Ti blocks several tens of micrometers in size were also formed simultaneously. On the other hand, equiaxed Al₂O₃ and TiB₂ particulates with a size of less than 2 μm were formed in situ in the TiO₂-Al-B and TiO₂-Al-B₂O₃ systems. The Al₃Ti phase was completely eliminated in the TiO₂-Al-B system with increasing B content. Tensile tests revealed that the Al₂O₃ · TiB₂/Al composite fabricated from the TiO₂-Al-B system exhibits excellent mechanical properties. The yield strength of the Al₂O₃ · TiB₂/Al composite appeared to increase with increasing TiB₂ content. The yield strength of the Al₂O₃ · TiB₂/Al composite could be further increased by introducing CuO into the TiO₂-Al-B system. Such an increment in mechanical strength arose from the strengthening effect caused by the Al₂Cu precipitates. The incorporation of CuO had no effect on the in situ reaction process of the TiO₂-Al-B system. Finally, the effect of SiC addition on the microstructure and mechanical properties of the composites fabricated from the TiO₂-Al-B and TiO₂-Al-B-CuO systems was also investigated.     

Effects of iron and temperature on solubility of light rare earth sulfates in multicomponent system of Fe2(SO4)3-H3PO4-H2SO4 synthetic solution

Numerous light rare earth elements (LREE) minerals containing Fe and P were processed by sulfuric acid roasting method, and the leaching solution mainly comprises LREE sulfate, Fe₂(SO₄)₃, H₃PO₄, and H₂SO₄, however, the solubility data of LREE sulfates in this system is few. This work studies the solubility of LREE sulfates in independent LREE sulfate system RE₂(SO₄)₃-Fe₂(SO₄)₃-H₃PO₄-H₂SO₄ (RE = La, Ce, Pr or Nd) and mixed LREE sulfates system (La,Ce,Pr,Nd)₂(SO₄)₃-Fe₂(SO₄)₃-H₃PO₄-H₂SO₄ at different temperature (25–65 °C) and concentrations of Fe₂(SO₄)₃ (Fe₂O₃, 0–50.13 g/L), H₂SO₄ (0.5 mol/L), and H₃PO₄ (P₂O₅, 20.34 g/L) based on the industrial operating condition at low liquid and solid ratio 2:1. The solubility of each LREE sulfate in the independent system (La₂O₃, 12.25–20.88 g/L; CeO₂, 41.93–62.35 g/L; Pr₆O₁₁, 37.34–56.69 g/L; Nd₂O₃, 26.60–37.63 g/L) is much higher than that of the mixed system (La₂O₃, 6.95–11.03 g/L; CeO₂, 10.63–21.51 g/L; Pr₆O₁₁, 11.56–20.36 g/L; Nd₂O₃, 12.36–19.79 g/L) under the same other conditions. The results also indicate that, in the two systems, both Fe and the temperature have negative effects on the solubility of LREE sulfates. That may occur due to the complication reactions between the complexes of RESO₄⁺ and Fe(SO₄)₂^–. However, the influence degree of temperature and iron concentration on the LREE sulfates solubility varies in the two systems and among different LREE species. This research is of theoretical significance for optimizing the conditions of the sulfuric acid process for recovering the LREE from the mixed LREE bearing minerals as well as the single LREE containing secondary rare earth scraps.     

Thermodynamic study on the effect of CaF2 on the nitrogen and carbon solubility in the CaO-Al2O3-CaF2 slag system

The nitrogen and carbon solubilities in the CaO-Al₂O₃-CaF₂ slag system at 1723K were measured to understand the effect of CaF₂ on the nitrogen and carbon dissolution behaviour using thermochemical equilibration technique. The nitride capacity in the CaO_satd.-Al₂O₃-CaF₂ system was constant until X_Al2O₃ / X_CaF2 = 0.23, followed by decrease with an increase in X_Al2O₃ / X_CaF2 ratio, and then showed a constant value. The carbide capacity in the CaO_satd.-Al₂O₃-CaF₂ system also showed the similar behaviour to the nitride capacity, however, the effect of CaF₂ on the activity coefficient of nitride and carbide ions showed some differences in case of X_CaF2 = 0.2. The effect of CaF₂ on the activity coefficient of carbide and nitride ions would not be significant in case of CaO-rich region of X_CaO / X_CaF2 = 0.31. However, CaF₂ could be expected to affect the activity coefficient of each ion in case of the Al₂O₃-rich region, causing compensating effect of the incorporated nitride (carbide) mechanism. The relationship between nitride and carbide capacity was also discussed.     

Phase reaction and diffusion path of the SiC/Ti system

Bonding of SiC to SiC was conducted using Ti foil at bonding temperatures from 1373 to 1773 K in vacuum. The total diffusion path between SiC and Ti was investigated in detail at 1673 K using Ti foil with a thickness of 50 μm. At a bonding time of 0.3 ks, TiC at the Ti side and a mixture of Ti₅Si₃C _x and TiC at the SiC side were formed, yielding the structure sequence of β-Ti/Ti+TiC/Ti₅Si₃C _x +TiC/SiC. Furthermore, at the bonding time of 0.9 ks, a Ti₅Si₃C _x layer phase appeared between SiC and the mixture of Ti₅Si₃C _x and TiC. Upon the formation of Ti₃SiC₂ (T phase) after the bonding time of 3.6 ks, the complete diffusion path was observed as follows: β-Ti/Ti+TiC/Ti₅Si₃C _x +TiC/Ti₅Si₃C _x /Ti₃SiC₂/SiC. The activation energies for growth of TiC, Ti₅Si₃C _x , and Ti₃SiC₂ were 194, 242, and 358 kJ/mol, respectively.     

Solid-solid reactions in the Ca3(AsO4)2-Ca2SiO4-CaSO4 ternary system at elevated temperatures

Exploratory laboratory-scale tests were performed in order to identify the solid phases present in the Ca₂SiO₄-Ca₃(AsO₄)₂ binary system and in the Ca₂SiO₄-Ca₃(AsO₄)₂-CaSO₄-CaO system. A microanalysis study from slow-cooled samples suggests the presence of at least two intermediate phases. These compositions correspond to Ca₅(AsO₄)₂(SiO₄) (1:1) and Ca₈(AsO₄)₄(SiO₄) (1:2). The formation of stable intermediate salts with high melting points is of significant industrial interest in copper converting operations. If excessive amounts of solids form, skimming problems or poor slag-metal separation may become problematic.     

Photoluminescence enhancement of red-emitting GdVO4：Eu and YVO4：Eu phosphors by adding zinc

We synthesized the rare-earth activated R0.94-xEu0.06ZnxVO4 (R: Gd and Y; 0≤x≤0.08) phosphors with a spherical morphology and a smooth surface by the ultrasonic spray pyrolysis. The annealed R0.94-xEu0.06ZnxVO4 crystallized in the tetragonal zircon type structure, belonging to the space group of I41/amd. The incorporation of a small amount of Zn to R0.94Eu0.06VO4 improved the emission characteristics. The emission intensities of the Gd0.88Eu0.06Zn0.06VO4 and Y0.9Eu0.06Zn0.04VO4 phosphors at 619 nm were 72% and 21% stronger than those of the Gd0.94Eu0.06VO4 and Y0.94Eu0.06VO4 phosphors, respectively. We demonstrated that the addition of Zn to R0.94Eu0.06VO4 was quite effective for improving the photoluminescent properties.     

Formation and Evolution Mechanism of the Inclusions of Al2O3·SiO2·CaO and Al2O3·SiO2·CaO·MgO in Seamless Steel Tube Steel

Herein, the formation and evolution mechanism of inclusions of Al₂O₃·SiO₂·CaO and Al₂O₃·SiO₂·CaO·MgO in seamless steel tube steel are investigated. In the long strip defects on the longitudinal cross section of the steel tube after the rolling bar piercing, the defect is mainly formed by Al₂O₃·SiO₂·CaO·MgO inclusions and Al₂O₃·SiO₂·CaO·inclusions dotted with·CaS inclusions after the rolling. The typical inclusions in the different steelmaking stages are mainly composed of CaS, Al₂O₃·(SiO₂), CaO·(SiO₂), MnS·(TiN), Al₂O₃·SiO₂·CaO·(CaS)·(MnS), Al₂O₃·SiO₂·CaO·MgO·(MnO), Al₂O₃·SiO₂·CaO·MgO·(CaS)·(MnS), etc. In the billet, the average sizes of Al₂O₃·SiO₂·CaO-based and Al₂O₃·SiO₂·CaO·MgO-based inclusions are much larger than those of the other types of inclusions. Part of SiO₂ in the deoxidized products SiO₂ can be reduced by [Al], resulting in the formation of the Al₂O₃·SiO₂ composite inclusions. The SiO₂ in Al₂O₃·SiO₂ inclusions can continuously be reduced by the dissolved [Ca] to form the Al₂O₃·SiO₂·CaO composite inclusions. The SiO₂ in the Al₂O₃·SiO₂·CaO inclusions can be reduced by the dissolved [Mg] to form the Al₂O₃·SiO₂·CaO·MgO composite inclusions. Another formation process of Al₂O₃·SiO₂·CaO·MgO inclusions is the entrapment of ladle slag in the vacuum degassing (VD) stage, due to the strong agitation of the rising Ar bubbles in the vacuum condition of the VD stage.