PbO SiO2 Research Articles

Experimental studies on the transition from xerogels to glasses for the system SiO2-PbO-B2O3 with added DMSO using the thermal-mass spectroscopy coupling technique

The thermal-mass spectroscopy coupling technique (TG-DTA-MS) was used to study the thermal decomposition behaviour of the transition from xerogels to glasses for the gradient refractive index materials SiO2PbOB2O3 with added dimethyl sulphoxide (DMSO). Compared with the TG-DTA-MS results for C2H5OH-system xerogeles, the MS curves for DMSO-system xerogels show (in addition to CH+3(mz, 15)) the CH3O+ (mz, 31), C2H5O+ (mz, 45), [(CH3)2SO]+ (mz, 78), etc., positive-ion mass spectrum peaks. This indicates that adding DMSO enables many residual OR groups to remain in the forming xerogels. This was beneficial for the condensation of the incompletely hydrolysed product and for preventing cracking of the xerogels. A preliminary study on the mechanism of thermal decomposition for DMSO-system xerogels is also given in this paper.

Interaction between Barium Titanate and Binary Glasses

Interactions between BaTiO3, and three binary glasses were studied through the reaction of BaTiO3, powder with glass powder. For PbO–B2O3 and PbO–SiO2 glasses, the reaction led to stable compound formation, the substitution of Pb in the BaTiO3 structure, and noticeable grain growth of BaTiO3. The interaction phenomena for these two glass systems were very similar. The substitution of Pb into BaTiO3 is assisted by chemical reactions in which BaB2O4 or Ba2SiO4 is formed. The substitution into BaTiO3 also seems to be closely related to the grain growth of BaTiO3. On the other hand, only compound formation was observed during the processing of BaTiO3 with Bi2O3–B2O3 glass. Neither BaTiO3 grain growth nor Bi substitution took place with the Bi2O3–B2O3 glass system. Based on the observed reactions and the glass viscosity, several sintering aids for BaTiO3 ceramic products are suggested in this paper.

A structural model for PbOGa 2O 3SiO 2 glasses

The effect of composition on the glass transformation temperature, viscosity, coefficient of thermal expansion, and density/molar volume of PbOGa 2O 3SiO 2 glasses was investigated. Trends in these data cannot be fully accounted for by previous structural explanations of the properties and glass-forming ability of the PbOGa 2O 3-based heavy metal oxide glasses. A new structural model is proposed which incorporates what is known about the structures of both PbOSiO 2 and PbOGa 2O 3 glasses to explain the anomalies in composition-property relationships demonstrated in this paper. In addition, this model is able to account for the discontinuities in the properties of PbOGa 2O 3 binary glasses which occur near the 75PbO25Ga 2O 3 composition.

Electronic states spectrum for lead silicate glasses with different short-range order structures

Molecular orbital (MO) linear combination of atomic orbitals (LCAO) simulation of the electronic states spectra of PbOSiO 2 glass with different structures of short-range order is performed. It is determined that superposing of ‘almost free’ Pb 2+ ion levels on silicon-oxygen spectrum takes place in low-lead glass, whereas high-lead glasses are characterized by mixing of Pb and O atoms valency states. Density-of-states peaks in X-ray photoelectron spectra and optical Pb6s → Pb6p transition with 5.2–3.0 eV energy as a function of Pb structural role are identified. The most probable radiation centers in PbOSiO 2 glasses are the analogues of known E − and H + centers formed on the band energies edges as a result of electron-hole localization SiO − … Pb 2+ frgaments.

Interface Reactions between Silicon Dioxide‐Lead Oxide Glass and Manganese Zinc Ferrite

The interface reations between SiO2–PbO melt and Mn‐Zn ferrite were studied using electron probe microanalysis (EPMA) and X‐ray diffraction (XRD). Intermediate layers were formed at the interface between the glass and the Mn‐Zn ferrite which were heated at 800° and 900°C, although those layers were not found in specimens heated at 1000°C. Using EPMA and XRD, the intermediate layers were found to be Pb2(Mn, Fe)2Si2O9 and Pb8(Mn, Fe)Si6O21. The mechanisms of interface reactions are discussed, related to glassforming regions. It was concluded that the interface reaactions between SiO2–PbO melt and Mn‐Zn ferrite are controlled by the dissolution of Zn ions and Mn ions from the Mn‐Zn ferrite.

Low‐Temperature Sintering of Lead‐Based Piezoelectric Ceramics

The low‐temperature sintering of lead‐based piezoelectric ceramics has been studied. The sintering temperature of lead zirconate titanate (PZT) ceramics could be reduced from ∼ 1250° to ∼960°C by the addition of a small amount of the lower‐melting frit, B2O3–Bi2O3—CdO. It exhibited the following dielectric and piezoelectric properties: Kp= 0.52 to 0.58, Qm= 1000, εT33/ε0= 800 to 1000, tan δ= 50 × 10−4, ρ= 7.56 to 7.64 g/cm3. Ceramics with the aid of suitable dopants (CdO, SiO2, and excess PbO) in the Pb‐(Ni1/3Nb2/3)O3—PZT family could be sintered at 860° to 900°C. For these materials, Kp= 0.56 to 0.61, Qm= 1000, εT33/ε0= 1500 to 2000, tan δ≤ 50 × 10−4, ρ= 7.80 to 8.03 g/cm3. The microstructure, sintering mechanism, and the effects of various impure additions have been analyzed by means of scanning electron microscopy, scanning transmission electron microscopy, electron probe microanalysis, and X‐ray photoelectron spectroscopy.

Glass Formation in the System SiO2–PbO Containing Transition‐Metal Oxides

Glass‐forming regions, valence states, and viscosities in SiO2–PbO systems containing various transition‐metal oxides as a third component were investigated. The glasses were prepared by melting in an open atmosphere. The glass‐forming regions ranged as follows: MnO≡ZnO > FeO1.5>NiO. The ratios Fe2+/(Fe2++ Fe3+) and Mn3+/ (Mn3++ Mn2+) in the glasses were determined by chemical analysis. The Fe2+/ (Fe2++ Fe3+) ratio in SiO2–PbO–FeO1.5 glasses ranged from 0.016 to 0.050. The Mn3+/ (Mn3++ Mn2+) ratio in SiO2–PbO–MnO glasses ranged from 0.056 to 0.30. The fraction of manganese (III) ions in the glasses varies considerably with the glass composition. The effects of transitionmetal oxides on the viscosity are discussed.

Ionic conductivity in a network of silicate glasses: Extension of a previous model to three-component glasses

In this paper we describe the ionic conductivity in silicate glasses by using equations which include non-linear behaviour as a function of ionic concentration. We analyzed binary-alkali silicate glasses, PbOSiO 2 and three-component glasses, namely Na 2OROSiO 2 (R = Mg, Zn, Ca, Pb, Sr, Ba). The alkali concentration varied in the molar concentration 15–35%, while in the case of three-component glasses the ratio between RO and Na 2O concentrations ranged from 0.1 to 3.1. Taking into account that the analyzed experimental results refer to a wide temperature (300 K < T < 900 K) and concentration ranges, the obtained theoretical agreement is satisfactory.

Influence of the pressure on the activity of PbO in an equimolar molten PbOSiO 2 mixture

The PbO activity in molten PbSiO 3 was determined with e.m.f. measurements in galvanic cells in the range 30–205 MPa and up to 1273 K. We notice a decrease of the PbO activity at 1198 K from α PbO=0.150 at 30 MPa to α μbO =0.140 at 205 MPa.

X-ray diffraction analysis on the structure of the glasses in the system PbOSiO 2

The structures of PbO·SiO 2 and 2PbO·SiO 2 glasses have been analyzed by use of X-ray diffraction data and pair function method. For PbO·SiO 2 glass, a model consisting of chains of PbO 3 pyramids and silicate chains showed good agreement with the observed RDF. For 2PbO·SiO 2 glass, the present authors reported previously a model in which chains of PbO 3 pyramids are connected with SiO 4 tetrahedra, while the chromatographic analyses of silicate anions by Götz et al. and Smart et al. showed that silicate anions are distributed from monomer to polymer in the glass. We reexamined the structure of this glass referring to these results. Three representative models containing isolated SiO 4, Si 4O 12 rings and (SiO 3) n chains respectively as well as PbO 3 chains were constructed and the RDFs were calculated with changing structure parameters. These three models showed satisfactory agreement with the observed data, showing that silicate anions are distributed from monomer to polymer in 2PbO·SiO 2 glass and an increase of SiO 2 content leads to polymerization of silicate anions to longer chains up to PbO·SiO 2 composition, while the chains of PbO 3 pyramids remain unchanged.

Further studies on the IR spectra of silicate glasses

Infrared spectra of the PbOSiO 2 glass system were studied by the KBr method. The absorption peaks show some different features as compared with the author's previous work on infrared spectra of alkali silicate glasses. It was found that with increasing PbO content the main absorption peak at a wave number larger than 1000 cm −1 originally shifts to less than 1000 cm −1 as the PbO content reaches 40 mol%; at the same composition occurs the abrupt change in property-composition curves of the PbOSiO 2 glass system. It is interesting that the absorption peak of non-bridging SiO links near 950 cm −1, being typical in the IR spectra of Na 2O·2SiO 2 glass, is rather weak in the spectra of Li 2O·2SiO 2 glass and almost disappears in that of PbO·2SiO 2 glass; this agrees with the different stability of the crystalline phase of corresponding bisilicate compounds. Infrared spectra of a series of Na 2OCaOSiO 2 glasses have also been studied. A new peak appears when the SiO 2 content is below 74 mol% and the glass composition enters the narrow region of commercial soda-lime glasses. As to K 2OPbOSiO 2 glasses, the shifting of the main absorption peak becomes obvious when the glass composition is near those of commercial glasses. Discussions have been given on different structural groups of SiO links adjacent with different metal ions. An attempt has been made to give some structural interpretations of the reason why the chemical compositions of commercial soda-lime and potash-lead silicate glasses are concentrated in a narrow region.

Effect of Applied Potential on the Interfacial Tension between Liquid Lead and PbO–SiO2Slags

AbstractThe measurement of the visible angle between lead and PbO-SiO2 slags were determined at 1073 K under an argon atmosphere. These results were combined with the surface tension data of lead, determined by the sessile drop method, and the literature data on the surface tension of slag to calculate the interfacial tension between liquid lead and PbO-SiO2 slags. The effect of an applied potential on the interfacial tension was determined. The data obtained on the interfacial tension offer fundamental information which assists to elucidate both the mechanism of the local corrosion of silica at the PbO-SiO2 slag-lead interface and also the lead losses in blast furnace smelting.

Effect of Applied Potential on the Interfacial Tension between Liquid Lead and PbO–SiO&lt;SUB&gt;2&lt;/SUB&gt; Slags

Effect of Applied Potential on the Interfacial Tension between Liquid Lead and PbO–SiO&lt;SUB&gt;2&lt;/SUB&gt; Slags

The optical basicity and UV absorption spectra of lead metasilicate and lead monoxide

The absorption spectrum of PbSiO 3, obtained by transmission through thin films, can be interpreted in terms of the optical basicity model to yield a basicity moderating parameter for Pb 2+ of 1.05. This agrees well with the value (approximately 1.0) obtained from recently reported “refraction basicity” measurements on the PbOSiO 2 system. The results are used to interpret the UV transmission spectrum of PbO which indicates essentially two (overlapping) major adsorption bands. The enegies of these bands are shown to be consistent with their origin as the 1 S 0 → 3 P 1 and 1 S 0 → 1 P 1 transitions of the Pb 2+ ion.

Development of the monocular visual field in the first postnatal year

The structural role, coordination geometry and valence of Fe in a series of Fe2O3–PbO–SiO2–Na2O glasses are studied by means of Fe-K-NEXAFS and EXAFS spectroscopies. Parameters for the study are the concentration of the Fe and Pb-oxides, the SiO2/Na2O ratio and the cast temperature. The EXAFS and NEXAFS results reveal that the role of Fe3+ depends on the concentration of Fe2O3. More specifically, in most of the studied quaternary systems, the Fe3+ ion is a glass former, i.e. the Fe atoms belong to FeO4 tetrahedra that participate in the formation of the glassy network. The role of Fe as an intermediate oxide is identified only in one sample with 20 wt% Fe2O3, where ∼80 at.% of the Fe atoms are tetrahedrally coordinated with O atoms, while the remaining ∼20 at.% of the Fe atoms occupy octahedral sites. It is also revealed that the tetrahedral coordination of Fe in the vitreous matrix is destroyed when a number of parameters is altered, such as the Tcast, the (Fe + Si)/O and the SiO2/Na2O ratio.

X-ray Diffraction Analysis of the PbO&amp;ndash;SiO&lt;SUB&gt;2&lt;/SUB&gt; 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.

Correlation between refraction basicity and theoretical optical basicity Part II. PbOSiO 2, CaOAl 2O 3SiO 2 and K 2OTiO 2SiO 2 glasses

The correlation between the refraction basicity ( B ref) and theoretical optical basicity ( Λ th) was investigated in the glasses of the PbOSiO 2, CaOAl 2O 3SiO 3 and K 2OTiO 2SiO 2 systems. It is concluded that the basicity of silicate glass containing highly covalent cation-oxygen bonds such as the PbO bond cannot be predicted by Λ th because the effect of symmetry restricted covalency on electron donation cannot be estimated by fixing χ M as constant. On the contrary, B ref can detect the difference of polarization of oxygen in silicate glasses without relating to the covalency of the cation-oxygen bond, so that B ref can be utilized as a measure of the basicity of silicate glass.

The Rayleigh scattering loss in silicate glasses containing PbO

The Rayleigh scattering coefficients of a number of glasses in the K 2OMgOPbOSiO 2 system have been determined. The scattering by density fluctuations and by concentration fluctuations was calculated using theories which were developed for ideal multicomponent liquids. In order to investigate how these theories could be applied to multicomponent glasses, the scattering by concentration fluctuations was calculated making different assumptions. It was found that reasonable agreement, both in trends and in order of magnitude, was obtained between the calculated and observed scattering coefficients when the glass was considered to be a frozen-in mixture of silicate units with compositions corresponding to those of crystalline silicates.

Ionic Transport in PbO—SiO2 Melts (IV)

Ionic Transport in PbO—SiO₂ Melts (IV)

Leaching mechanism of PbOSiO 2 glasses in acid solution

The leaching mechanism of xPbO(100- x)SiO 2 glasses ( x=35, 40, 50, 55, 60 mol%) in a nitric acid has been investigated by solution analysis and surface analysis. It was observed that the removal of Pb depended on PbO content in a complicated way. For short periods of leaching, the removal of Pb increases gradually with the PbO content up to 50 mol% and remains at a nearly constant value at more than 50 mol%. For longer periods, it increases gradually with the PbO content in all concentration regions. This result is well explained by the combination of two types of mechanisms. One is the selective leaching of Pb and the other is the dissolution of the glass surface or the leached layer with residual Pb. The selective leaching of Pb is considered to be controlled by the interdiffusion of Pb 2+ and H + ions. The diffusion coefficients of Pb 2+ and H + ions were determined by a numerical analysis from the Pb in-depth profiles in the leached layer.