System PbO-SiO2 Research Articles

Thermodynamics and phase diagrams in the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3

We applied our model to the enthalpy of mixing data of the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3. The most stable composition in the liquid, that is where the enthalpy of mixing is most negative, is with a metal-oxygen ratio of 4 to 3, for monovalent metals (Na and Li) and 3 to 4 for divalent metals (Ba and Ca) in liquid silicates or borates. The same applies to the CaO-SiO2, CaO-Al2O3, PbO-B2O3, PbO-SiO2, ZnO-B2O3, and ZnO-SiO2 systems. The oxygen to metal ratio, its constant value in various types of systems, reflects and describes the structure of the liquid. Using the analyzed enthalpies of mixing data and the available phase diagrams, we calculated the enthalpies of formation of the various binary compounds. The results are in excellent agreement with data in the literature that were obtained from direct solid-solid calorimetry.

Application of a kinetic model to tracer diffusion of silicon and oxygen in silicate melts

In this work we have improved the kinetic model of Kieffer and Borchardt for diffusion in silicate melts, which takes into account both the diffusion of individual polyanions and the reaction of different polyanions through condensation and splitting events. Making assumptions for the individual condensation reactions, similar to those by Masson, the equilibrium polyanion distributions in silicate melts were calculated by solving a system of coupled first-order differential equations, describing the reactions between polyanions of various sizes. The concentration dependence of the SiO44- monomers, determined by our approach, is identical to that resulting from the thermodynamic treatment by Masson. Furthermore, by allowing for local changes in the isotope distributions of the elements, and by assuming that migration of all species present in the system occurs due to random motion, the self-diffusion of silicon and oxygen in CoO-SiO2 melts has been simulated. The parameters for the model have been estimated by fitting me simulation results to our experimental data of Si and O tracer diffusion. While the simulated concentration profiles were in good agreement with our experimental tracer diffusion measurements in the CoO-SiO2 system, their shape could not be described by the standard solution of Fick's law. Conversely, for the CaO-SiO2 and PbO-SiO2 systems, the simulated profiles were in much better agreement with the standard solution. This difference in diffusional transport properties can be qualitatively interpreted as due to the structural differences of CoO-SiO2 as compared to the two other systems.

Thermodynamic and kinetic study of the PbO-B2O3 and PbO-SiO2 systems in the glass transition range

Thermodynamic and kinetic study of the PbO-B2O3 and PbO-SiO2 systems in the glass transition range

Thermodynamic and kinetic study of the PbO-B2O3 and PbO-SiO2 systems in the glass transition range

Thermodynamic and kinetic study of the PbO-B2O3 and PbO-SiO2 systems in the glass transition range

Electronic and ionic transport in liquid PbO-SiO2 systems

The objective of the present work was to examine electronic transport in the PbO-SiO2 melt. The experimental work consisted of studying the oxidation of liquid Pb covered by a layer of liquid PbO-SiO2 using a thermogravimetric arrangement. Oxidation of liquid Pb was dependent on the melt height and was parabolic in nature, indicating the oxidation process to be diffusion controlled. We observed a moderate increase in the oxidation rate with additions of a transition metal oxide (Fe2O3) to the melt. However, when melt/gas and melt/metal interfaces were short circuited by Ir wires, a much higher increase in the oxidation rate was noticed. Additionally, the conductivity of the PbO-SiO2 melt with Fe2O3 additions was measured as a function of Po, to detect the nature of electronic contribution by the Fe2O3. Combining the results of the oxidation and conductivity experiments, we conclude that the oxidation of liquid lead covered by liquid slag occurs through ionic and rate controlling electronic (probably electron holes) transport in the melt.

X-ray Diffraction Analysis of the PbO–SiO<SUB>2</SUB> System in the Glassy and the Molten State

The structures of glassy and molten states in the PbO–SiO2 system were investigated by X-ray diffraction analysis. In the glass, the Pb–O bond has the ionic charactor in the SiO2-rich region and has more of the covalent charactor with increasing PbO concentration. The atomic distance of Pb–Pb pair, 0.375 nm, is not changed with changing PbO concentration, and Pb atoms are considered to be arranged with local order in the glass. The Pb–Pb peaks in the SiO2-rich region correspond roughly to multiples of 0.374 nm, and Pb atoms seem to be arranged in a simple and straight chain. However, the arrangement probably tends to consist of twisted and zigzag PbO4 chains with increasing PbO concentration.In the molten state, a part of the three-dimensional network structure of covalent Pb–O bond seems to be destroyed and, the concentration of Pb2+ ion which is free in the melt increases. Then Pb–Pb pairs with the distance around 0.50 nm increase due to increase in straight chains such as ionic Pb2+–O2−–Pb2+ which hardly exist in the glass.

A generalized approach to the flood-knapp structure based model for binary liquid silicates: Application and update for the PbO-SiO2 System

The nonideal activity of a metal oxide in a molten binary silicate system is described by treating the liquid as an ideal solution and by considering the formation of a few complexes. Application of this approach to the binary system PbO-SiO2 shows that the experimentally determined activity of PbO(l) can be modeled by considering the lead silicate melt as an ideal solution of Pb2+ and O2−,SiO44−, Si2O76−, Si12O3726−, and Si4O104−. The calculated Gibbs free energy values for the formation of the anionic complexes from O2− and SiO44− are: ΔGℴ(Si2O76−)/J · mol−1 = 38977 − 30.909(T/K); ΔGℴ(Si12O3726−)/J · mol−1 = 200158 − 121.813(T/K); Δℴ(Si4O104−)/J · mol−1 = 104627 − 28.094(T/K). Values of Gibbs free energy of formation of the solid phases PbO, Pb4Si06, Pb2SiO4, PbSiO3, and SiO2 which, together with the melt model data, give the best fit to experimental phase relations in the system PbO-SiO2 were calculated. These values are all in good agreement with literature data.

遷移金属を多量に含む非晶質の作成と光学的性質

In order to design a photo-selective amorphous layer to be used for a solar energy collector, it is of primary importance to study the fundamental characteristics of the amorphous candidate materials for this purpose. In this study in the first place vitrification ranges in the binary and ternary oxide systems containing high concentration of transition metal oxides have been determined by a rapid quenching technique of twin-roller method. Amorphous thin layers were obtained in the range Fe2O3=5∼25mole % in the Fe2O3-PbO system, V2O5=5∼26mole % and 35∼40mole % in the V2O5-PbO system, TiO2=5∼50mole % in the TiO2-PbO system. Secondly light transmittance has been measured for the amorphous materials prepared in the systems Fe2O3(V2O5)-PbO-SiO2, Fe2O3 (V2O5)-PbO, Fe2O3(V2O5)-NaPO3(P2O5) and TiO2-PbO in the range of visible 400mμ∼800mμ, near infrared 500mμ∼2.5μ, and infrared to far infrared 5μ∼25μ. In the infrared region the absorption peaks associated with Fe-O, V-O, Si-O and P-O vibrations shifted to shorter wave length as PbO was substituted with SiO2 or P2O5 in the Fe2O3(V2O5)-PbO-SiO2 system or in the Fe2O3(V2O5)-NaPO3 (P2O5) system, while that of Ti-O vibration shifted to longer wave length as PbO content was decreased in the TiO2-PbO system. From the absorption peaks observed in the near infrared and visible range, it is deduced that low valency ions Fe2+, V4+, V3+, Ti3+ exist together with high valency ions Fe3+, V5+, Ti4+ and Pb2+ in the multi-component amorphous systems. It is interesting to note that the absorption edges in the visible range associated with the transitions of d-electrons in Fe2+ and V4+ ions shifted to shorter wave length as PbO was substituted with SiO2 in the Fe2O3 (V2O5)-PbO-SiO2, while that of Ti3+ to shorter wave length as PbO content was lowered in the TiO2-PbO system.

珪酸陰イオンを解析するための改良トリメチルシリル化法

In the application of the trimethylsilylation method by Götz and Masson for the analysis of the silicate anions, Masson et al. have shown that water is essential for the trimethylsilylation of anhydrous silicates. However, that a subreaction caused by the presence of water may affect the trimethylsilal reaction. In this work we used the improved solvents containing no water, (CH3)3SiCl 3 cm3, CH3OH 6 cm3 and (CH3)3SiOSi(CH3)3 9 cm3. Crystalline calcium silicates with well defined structures and lead silicate, which showed poor reaction efficiency in Masson’s method were analysed by these solvents. The results obtained are summarized as follows.(1) The reaction efficiency of trimethylsilylation was 100% for the glasses of PbO-SiO2 and CaO-SiO2 systems.(2) The products were obtained 100% as the derivative of Si4O1210− for the α-CaO·SiO2, 100% as the derivative of Si2O76− for the 3CaO·2SiO2 and 97% as the derivative of SiO44− for the 2CaO·SiO2.(3) For the crystalline calcium silicate (43.3 mol%SiO2) with a mixture of different anions, the products were determined to be composed of 80.5%Si2O76− and 18.6%Si4O1210− derivatives.As the result obtained was better than that by Masson’s method, the present method may be used for determining various silicate structures with high accuracy as their corresponding trimethylsilyl derivatives.

NiOを含む溶融珪酸塩へのMgOの添加効果

The measurements of electrical conductivity for CaO-SiO2-NiO-MgO and PbO-SiO2-NiO-MgO melts have been conducted to discuss the interaction of NiO and MgO contained in silicate melts. The measurements of infrared and far-infrared absorption spectra were carried out to discuss the dissociation of NiO in the silicate.When NiO was replaced by MgO in CaO-SiO2 and PbO-SiO2 systems, the electrical conductivity tends to deviate from the additivity line to positive side. The absorption band of the molecular type (no dissociation to Ni2+ and O2−) of NiO observed in far-infrared region faded out with addition of MgO, and changed into that of dissociation type of NiO. It appears that the MgO promote the dissociation of NiO in silicate melts. The mechanism for interaction of NiO and MgO was discussed.

Effect of CaO, Al<SUB>2</SUB>O<SUB>3</SUB>, MgO and ZnO on the Activity of PbO in the Molten PbO–SiO<SUB>2</SUB> System

The e.m.f. measurements were carried out in the temperature range of 1173∼1323 K by means of the following galvanic cells employing solid electrolytes:Ni.NiO(s)/ZrO2+CaO/Pb.PbO−SiO2−MeO(1)where MeO is CaO, Al2O3, MgO and ZnO.From these experimental results, it was found that the activity of PbO in the molten PbO–SiO2 system was increased remarkably by the addition of CaO or MgO, considerably by ZnO and slightly by Al2O3.These experimental results were found to be in good agreement with the results of Richardson and Pillay on the PbO–SiO2–CaO, PbO–SiO2–MgO and PbO–SiO2–ZnO systems.

The Crystallization of Pb5Si3O11 from the Glass in the PbO–SiO2 System

Abstract A new compound, Pb5Si3O11, is prepared by the crystallization of the glass in the PbO–SiO2 system. Pb5Si3O11 has an orthorhombic symmetry, and its lattice parameters are determined to be a0=9.93 Å, b0=8.31 Å, and c0=34.4 Å.

Activities and oxygen transport in PbO-SiO2-P2O5melts

AbstractActivities of PbO in PbO-SiO2-P2O5 melts with up to 12.5 mole % of P2O5 were measured at 1050 to 1350°K by an electrochemical method. The results were used to estimate activities in the binary PbO-P2O5 over a wider range of composition than reported in a previous study. In contrast with the system PbO-SiO2, the binary PbO-P2O5 shows pronounced negative deviations from Temkin's Law. Substitution of SiO2 by P2O5 lowers the 'activity and leads to increasingly negative partial heats of mixing of PbO. Transport of oxygen through these melts was shown, by emf measurements, to occur by at least two mechanisms, one of which is associated with the presence of dissolved lead in the slags and the other with the formation of Pb4+ ions. Resume Les activites de PbO dans les melanges fondus PbO–SiO2–P2O5, contenant 12.5% molaire au moins de P2O5, ont ete mesurees de 1050 a 1350 K par une methode electrochimique. Les resultats ont permis d'evaluer les activites dans le systeme binaire PbO-P2O5 sur une gamme de co...

ChemInform Abstract: COMPOUND FORMATION AND PHASE EQUILIBRIA IN THE SYSTEM PBO‐SIO2

AbstractDas Phasendiagramm wird angegeben.

Compound Formation and Phase Equilibria in the System PbO‐SiO2

Compound formation in the system PbO‐SiO2 was studied; the results are contrasted with those previously reported. Fifteen binary phases, 4 of which had not been reported, were prepared in the present study. The new phases include Pb5Si8O21, an orthorhombic polymorph of PbSiO3, Pb3SiO5, and a high‐SiO2 phase containing ∼ 60 mol% SiO2. It was shown that Pb3SiO5 is thermodynamically stable relative to Pb2SiO4 and 4PbO.SiO2 below 640±5°C. A revised phase equilibrium diagram is presented.

Electric Conductance and Structure of Molten Oxide System PbO-SiO<sub>2</sub>-Fe<sub>2</sub>O<sub>3</sub>

Electric conductivities of molten oxide system PbO-SiO2-Fe2O3 were measured over the temperature range from liquidus to 1200°C (Fig. 3-6). The mechanism of conduction was discussed and compared with that of system PbO-B2O3-Fe2O3 from the view point of the behaviour of ferric ion in the melt.The samples, containing Fe2O3 0-25mol%, were quenched from 1200°C, and most of them were glass. Some glasses were crystallized by heat-treatment. Measurements of Infra-red absorption spectra and X-ray diffraction were carried out of the samples quenched and then crystallized (Fig. 9, 10), and the structure of complex silicates in these samples was discussed.Based upon these measrements, the behaviou of ferric ions and structure of complex silicate ions in molten oxide were discussed, and the following results were obtained.(1) Specific conductivity increases with temperature, and obeys the Arrhenius equation (e.g. Fig. 2). The values of the apparent activation energy for conduction are about 10-25kcal/mol, and are nearly the same values as in the system PbO-SiO2. Specific conductivity increases when the SiO2 content decreases (Fig. 6), and increases with the Fe2O3 content when the ratio (PbO)/(SiO2) is constant (Fig. 4, 5). From these results, it is considered that the electric conduction in this system is ionic and that the electric charge is mainly carried by Pb2+ and Fe3+ ions.(2) The activation energy for conduction increases with the increase of effect of Fe3+ ion, because it seems to have larger interaction with silicate anion than Pb2+ ion. However, the activation energy decreases when the dissociation of chain or sheet (or ring) silicate ions occurs in the melts containing more Fe2O3, 10-20mol% (Fig. 8). The dissociation of silicate ions is caused by the dissociation of Fe2O3 into Fe3+ and O2- ions.(3) The complex anion, corresponding to the unknown ternary compound PbO-Fe2O3 SiO2, seems to exist in the molten oxide of this system which contains more than 20mol% of Fe2O3. The activation energy for conduction increases with the presence of this complex anion.

Free energy of mixing of divalent basic oxides with silica

An expression derived for the free energy of mixing of a divalent basic oxide (MO) with SiO2 based on a model of silicate structure, takes into account the distribution of O2–(from MO) into the silica network, the mixing of silicate ions with O2– and the enthalpy of mixing. The resulting expression is [graphic omitted]. For the proper choice of β, calculated values of the activity of MO for the system PbO—SiO2, MnO—SiO2, FeO—SiO2 and CaO—SiO2 are in good agreement with experiment. The model predicts that the activity of the basic oxide decreases with increase in temperature.

Subsolidus Studies in the System PbO‐SiO2

The subsolidus region of the PbO‐SiO2 system was studied by DTA and X‐ray diffraction. X‐ray diffraction analysis showed the presence of five compounds: 4PbO.SiO2, 3PbO·SiO2, 2PbO·SiO2, 3PbO·2SiO2, and PbO·SiO2. The compound 4PbO·SiO2 has previously been reported to have three polymorphic forms; there are two polymorphs of 2PbO·SiO2 with the inversion at 460°±15°C. The compounds 3PbO·SiO2 and 3PbO·2SiO2 were unstable above 430°±10° and 585°±15°C, respectively; PbO·SiO2 was unstable below 525°±15°C. DTA patterns were determined for glasses of the composition of each of these compounds.

Discussion of "Silica Transformations in the System PbO-SiO2"

Discussion of "Silica Transformations in the System PbO-SiO2"

Discussion of “Silica Transformations in the System PbO‐SiO2”

Discussion of “Silica Transformations in the System PbO‐SiO₂”