Vitrification, Properties, and Structure of Lead-Tellurite Borate Glasses

The vitrification, structure, and physicochemical properties of glasses in the PbO – ZnO – B₂O₃ – TeO₂ system are studied. The dual role of the lead ions in the glass structure is confirmed. It is demonstrated that the coordination transition of boron ions correlates with the concentration of PbO in glass. A nonlinear dependence of properties on the glass composition is due to the structural modifications in glass.     

Microstructure and electrical characteristics of ZnO–B2O3–PbO–V2O5–MnO2 ceramics prepared from ZnO nanopowders

A peculiar kind of ZnO–B₂O₃–PbO–V₂O₅–MnO₂ ceramics was produced from the ZnO nanopowders directly co-doped with the oxides instead of lead zinc borate frit in this investigation. The 8 wt.% (PbO+B₂O₃) co-doped ceramics sintered at 950 °C for 2 h displayed the optimum electrical properties, that is, leakage current density J_L=6.2×10⁻⁶ A/cm², nonlinear coefficient α=22.8 and breakdown voltage V_BK=331 V/mm. The co-doping of 8 wt.% (PbO+B₂O₃) resulted in an increase in nonlinear coefficient and a decrease in leakage current density of the ZnO–V₂O₅ varistors while the sintering temperature showed no evident influence on nonlinear coefficient and leakage current density at the range of 800–950 °C.     

Properties, Structure, and Application of Low-Melting Lead–Bismuth Glasses

Glass formation, crystallization, and physicochemical properties, as well as glass structure in the system PbO – ZnO – Bi₂O₃ – B₂O₃ – SiO₂, are investigated in the section with a constant molar content of glass-formers (B₂O₃ + SiO₂) equal to 20%. A nonlinear dependence of glass properties on their composition is established caused by the change of the coordination state of lead ion in glass structure. The developed glasses are recommended for joint and seals in the production of a new generation of physical parameter sensors.     

The effects of Cr2O3, Cu(OH)2, ZnO and PbO on the compressive strength and the hydrates of the hardened C3A paste

The purpose of this paper is to investigate the effects of Cr₂O₃, Cu(OH)₂, ZnO or PbO on the hydration of C₃A and characterization of its hydrates. C₃A pastes adding the above compound were examined on the basis of the hydration products and their structure, compressive strength and rate of early hydration.     

Oxidative Dimerization of Methane on Lead Oxide—Alumina Catalysts

PbO-Al₂O₃ catalysts of different composition were investigated for oxidative dimerization of methane. Characterization of the catalysts was carried out by means of X-ray diffraction, IR and temperature-programmed reduction measurements. A maximum of the methane conversion and selectivity was observed on PbO/γ-Al₂O₃ catalysts with PbO contents between 10 and 35 mol-%; PbO, PbAl₂O₄ and Al₂O₃ are catalytically less active. It is suggested that the catalytically active phase exhibits a magnetoplumbite-like structure which is formed, during thermal pretreatment, between PbO and γ-Al₂O₃ or amorphous Al₂O₃. A correlation between reducibility and catalytic activity was found.     

RELATION OF ELECTRICAL CONDUCTIVITY TO CHEMICAL COMPOSITION OF GLASS*

The electrical conductivity of some glasses in the soda-lime-silica system was measured at 400 °C. with an apparatus which is described. The specific resistance at this temperature ranged from 0.06 to 5.0 × 10⁵ ohms per cc. Measurements were made on other glasses containing equivalent amounts of various oxides incorporated in a parent soda-lime-silica glass. It was found that an increase in resistance was produced by additions of MnO, ZnO, B₂O₃, Fe₂O₃, BaO, PbO, TiO₂, and K₂O, the resistances increasing in this order. A decreased resistance was produced by Na₂O, CaO, and Al₂O₃. Previously published data on the power factors of these glasses are reviewed.     

Modeling and Optimization of the Synthesis of Fine-Particle Powders in High-Frequency Plasma

The synthesis of SiO₂, Al₂O₃, BaO, PbO, B₂O₃, ZnO, and SiO₂–Al₂O₃–BaO fine-particle powders was studied experimentally and optimized. The metal oxides, silicon, and an SiO₂–Al₂O₃–BaO mixture were treated in an argon–oxygen or air high-frequency induction plasma, whereupon amorphous layers were deposited onto silicon substrates. Heat treatment of these layers at 1473 K for 15 min yielded continuous amorphous dielectric films with desired properties.     

Microstructures and electrical properties of lead zinc niobate–lead titanate–lead zirconate ceramics using microwave sintering

Electrical properties and microstructural characteristics of (1 − x)(0.94PbZn_1/3Nb_2/3O₃ + 0.06BaTiO₃) + xPbZr_yTi_1−yO₃ (PZN–PZ–PT) ceramics, sintered by microwave heating, were investigated using electron microscopy, energy-dispersive spectroscopy (EDS) and electrical property measurement. Experimental results imply that the microwave-sintered (MW) samples with x = 0.5 and y = 0.52 (1150 °C, 10 min) possess higher dielectric constant than the conventionally sintered (CS) specimens (1150 °C, 2 h). Microstructural investigations show that ZnO precipitated on the surfaces of specimens during a thermal process, implying that ZnO diffusion may have influenced the distribution of phases in a specimen due to an eutectic reaction of PbO and ZnO. TEM–EDS investigations show that the CS specimens exhibit pronounced elemental segregation of PbO and ZnO at the grain boundaries, but it is much less significant for MW samples. The results imply that microwave sintering not only enhances material densification markedly, but also reduces the PbO/ZnO segregation and amorphous intergranular layers effectively, and thus improve the electrical properties of PZN–PZ–PT ceramics.     

Low-temperature sintering of 12Pb(Ni1/3Sb2/3)O3–40PbZrO3–48PbTiO3 with V2O5 and excess PbO additives

Low-temperature sintering of 12Pb(Ni_1/3Sb_2/3)O₃–40PbZrO₃–48PbTiO₃ (12PNS–40PZ–48PT) calcined powders with V₂O₅ and excess PbO additives has been investigated. Adding 0.20 to 0.40 wt.% V₂O₅ and 1.0 wt.% excess PbO to 12PNS–40PZ–48PT calcined powders and sintering at 950 °C for 4 h, the sintered samples only contain the perovskite structure. The calcined powders are doped with 3.0 wt.% excess PbO and 0.20 to 1.0 wt.% V₂O₅ and sintered at 950 °C for 4 h, the coexistence of both tetragonal and rhombohedral phases with the minor phase of pyrochlore is observed. During the calcined powders contain 1.0 wt.% excess PbO and are sintered at 950 to 975 °C for 2 h, the bulk density decreases with V₂O₅ addition greater than 0.6 wt.%. When the calcined powders with 3.0 wt.% excess PbO are sintered at 900 to 975 °C for 2 h, the bulk density decreases with added V₂O₅ content increased. The values of the planar coupling coefficient (K_p) approach the maxima, namely, 0.51 obtained for the compacts containing 0.40 wt.% V₂O₅ and 1.0 wt.% excess PbO and sintered at 950 °C. As the calcined powders are added with 3.0 wt.% excess PbO and 0.80 wt.% V₂O₅ and sintered at 975 °C for 2 h, the maximum Q_m value 1100 is obtained.     

Evaluation of the fraction of fourfold-coordinated boron in oxide glasses from their composition

A model for evaluating the fraction of fourfold-coordinated boronN ₄ in the oxide glasses of different systems has been proposed. The model involves simplified equations of hypothetical chemical equilibria between structural groups. The calculated N₄ values are compared with the NMR experimental data obtained by different authors for ∼350 glasses containing Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O, Tl₂O, SrO, PbO, ZnO, A1₂O₃, Ga₂O₃, Fe₂O₃, In₂O₃, B₂O₃, and SiO₂ oxides. The mean deviation between the calculated and experimental values ofN ₄ is equal to about 0.05.     

The electrochemistry of metal oxide additives in pasted zinc electrodes

The effect of small additions (2 w/o–4 w/o) of HgO, Tl₂O₃, PbO, CdO, In₂O₃, In(OH)₃, In and Ga₂O₃ to pasted zinc oxide electrodes has been evaluated using chronopotentiometry, cyclic voltammetry, polarization measurements and scanning electron microscopy. Additives such as PbO, In(OH)₃ and In increase the density and the polarizability of the deposit whereas additives such as Ga₂O₃ and CdO yield finely divided deposits of low polarizability. The results are attributed to a substrate effect on zinc deposition. The beneficial effect of some additives (eg a mixture of 0.5 w/o In(OH)₃ and 1 w/o PbO) is attributed to an improvement in the secondary current distribution due to an increase in electrode polarizability.     

Evaluation of the fraction of fourfold-coordinated boron in oxide glasses from their composition

A model for evaluating the fraction of fourfold-coordinated boronN ₄ in the oxide glasses of different systems has been proposed. The model involves simplified equations of hypothetical chemical equilibria between structural groups. The calculated N₄ values are compared with the NMR experimental data obtained by different authors for ∼350 glasses containing Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O, Tl₂O, SrO, PbO, ZnO, A1₂O₃, Ga₂O₃, Fe₂O₃, In₂O₃, B₂O₃, and SiO₂ oxides. The mean deviation between the calculated and experimental values ofN ₄ is equal to about 0.05.     

Lead oxides as cathode for lithium non-aqueous cells

The cathodic behaviors of PbO (red and yellow), Pb₃O₄, Pb₂O₃ and PbO₂ (α and β) in lithium cells were presented. A single plateau at 1.4–1.5 V was observed over the wide range in discharge curves at 0.1 mA. cm^?2 for PbO (red), Pb₃O₄ and Pb₂O₃ cathodes, and two plateaus were observed for PbO (yellow) cathode. The both types of PbO₂ showed the complicated behaviors in discharge curves. For a low current density discharge to 2 V end-voltage, the cell with α-PbO₂ showed 95–100% of utilization based on one electron transfer per molecule.The structural changes of these lead oxides during discharge were examined, and the final reduction product was proved to be lead metal. The cell reaction of these lead oxides were also examined from X-ray and electrochemical data.The performance of 1.5 V lithium cell system with PbO (red), Pb₂O₃ and Pb₃O₄ cathodes, and 3 V lithium cell system with α-PbO₂ cathode were demonstrated and discussed.     

STUDY OF THE PROPERTIES OF SIMPLE ENAMEL GLASSES1

Three component glasses of the systems Na₂–B₂O₃–SiO₂ and Na₂O–PbO–SiO₂ were investigated as to acid-resisting properties. An increase in silica in general improves the acid resistance. The effect of Na₂O, B₂O₃, and PbO on the acid resistance of an enamel is dependent on the composition to which these oxides are added. Some of these enamels showed considerable promise as acid-proof enamels.     

Bi2O3-sensitized hierarchically mesoporous ZnO nanoparticles for Hg(II) reduction

Herein, an affordable and novel approach to design Bi₂O₃-sensitized hierarchically mesoporous ZnO nanoparticles (NPs) with a variety of Bi₂O₃ contents is achieved for Hg(II) reduction upon visible light exposure. TEM images of both ZnO and 3% Bi₂O₃/ZnO samples exhibit nanoscale spherical-like structures with a regular shape and a particle size of ~30 nm. The incorporation of Bi₂O₃ on hierarchically mesoporous ZnO networks allows visible light to be harvested in a broad range, and the mesoporous 3% Bi₂O₃/ZnO heterostructure demonstrates the best photocatalytic efficiency for Hg(II) reduction with a value of ~100% after 60 min. The photoreduction rate over the 3% Bi₂O₃/ZnO heterostructure is enhanced 10 and 20 times more than that of TiO₂-P25 and ZnO NPs. The rate constant of the 3% Bi₂O₃/ZnO heterostructure is 16.8 and 33.6 fold larger than that of TiO₂-P25 and ZnO NPs. The superior Hg(II) photoreduction performance could be ascribed to the synergistic effect, excellent visible-light harvest, large surface area, and pore volume provided by incorporating Bi₂O₃ and the heterojunction design between p-type Bi₂O₃ and n-type ZnO. This alignment of the electronic bands provides charge carrier separation, thereby decreasing the recombination rate. Finally, the mechanisms and kinetics for the photocatalytic reduction of Hg(II) are proposed.     

Spectroscopic investigation of samarium-doped lead oxyflouroborate glasses using photo and cathode luminescence

Samarium-doped lead oxyflouroborate glasses of 60 B₂O₃- xPbO- (40-x)LiF where (x=0-30 mol%) with 3×10²⁰ ions/cm³ of Sm₂O_3, were prepared by melt quenching. UVVis absorption, photo luminescence (PL) and cathode luminescence (CL) spectroscopies were used to study the effect of varying PbO content on the spectroscopic properties of these samarium-doped glasses. The absorption of the UV-edge shifts toward higher wavelengths, not only because of higher polarizability of lead ions, but also because of the strong allowed s-p transition of Pb²⁺. Judd-Ofelts parameters were determined and indicate that the asymmetry around Sm³⁺ ions increases with increasing PbO content. Ω₂ probes the asymmetry by the ratio of intensity of the hypersensitive transition (⁶H_9/2) to that of purely magnetic (⁶H_5/2) transition. Furthermore, an increase in the spectroscopic quality factor (Ω₄/Ω₆) was observed with increasing PbO content which indicates that these glasses have the potential to be used as efficient active laser glasses. The calculated energy transfer parameter increases with increasing PbO content. Also, stark splitting increases with increasing PbO concentrations. FWHM of the CL emission peaks and stark splitting, are found to be much larger than that in PL. This was explained by the high electric field generated from the exciting electron pulses.     

The microstructure and characteristics of 0.875PZT–0.125PMN ceramics with addition of Pb-based flux

The paper tries to prepare dense piezoceramics by way of reactive liquid phase sintering. Technique concerning a low-temperature sinterable process is developed by incorporating 4PbO.B₂O₃. The host system is a perovskite type piezoceramics, 0.875Pb(Ti,Zr)O₃–0.125Pb(Mg_1/3Nb_2/3)O₃. It is clear that PbO deficiency of PMN-based relaxor can result in an excessive amount of pyrochlore phase which causes poor densification and greatly degraded dielectric properties. Additives, such as the Pb-based flux, 4PbO·B₂O₃, that increase the amount of PbO also reduce the fraction of pyrochlore phase of PMN-based. If small amounts of 4PbO·B₂O₃ glass powder are added to the calcined 0.875PZT–0.125PMN ceramics, the liquid pase is formed during sintering. Hence, the piezoelectric and dielectric properties are enhanced and the sintering temperature can be reduced. Grain growth in ceramics with sintering time and amounts of 4PbO·B₂O₃ dopants was also studied. The grain growth was analyzed from the kinetic grain growth equation: Rⁿ=k×t.     

Matrix phase induced boosting photoactive performance of ZnO nanowire turf-coated Bi2O3 plate composites

A new nanocomposite consisting of ZnO nanowire turf-coated Bi₂O₃ plates was synthesized using a method combining a chemical bath and hydrothermal crystal growth through sputtering ZnO seed layer-assisted growth. Structural analysis revealed that highly crystalline, high-density, one-dimensional (1D) ZnO crystals were uniformly coated on the organized two-dimensional (2D) Bi₂O₃ plates with a single β phase or dual α/β polymorphic phases. The Bi₂O₃–ZnO composites exhibited enhanced absorption properties in the ultraviolet and visible regions compared with pristine Bi₂O₃ and ZnO. Furthermore, the Bi₂O₃–ZnO composites exhibited higher photoactive performance than that of the pristine Bi₂O₃ and ZnO because of the low recombination rate of photoinduced electron−hole pairs caused by the vectorial transfer of electrons and holes between ZnO and Bi₂O₃ and the substantially increased surface area of the unique composite morphology. The ZnO nanowire turf-coated Bi₂O₃ plates with a α/β-Bi₂O₃ matrix exhibited photoelectrochemical and photocatalytic properties superior to those of the composite with a single β-Bi₂O₃ matrix. The coexistence of α/β homojunction in the Bi₂O₃ matrix and the abundant heterojunctions between the ZnO nanowires and Bi₂O₃ plates substantially enhanced photoexcited charge separation efficiency. Growing high-density 1D ZnO on 2D Bi₂O₃ via a combination methodology and crystallographic phase control provided a promising material design route for nanocomposite systems with high photoactivity for photoexcited device applications.     

SOME DATA ON THE COMPOSITION OF ARSENIC ENAMELS FOR COPPER1

Methods of application are by usual wet slushing, and sieving powdered enamel on to clean copper sheets and fusing to a smooth coat. Where slush-coat is necessary it is advisable to use an enamel free from lead and arsenic as a ground. In this work the dry method is used exclusively. In the formulae given, increase of SiO₂, increases fracturing or shivering, increase of B₂O₃ above 0.2 equiv. in presence of 0.1 equiv. AS₂O₃ causes enamels to come mat. Increasing KNaO at expense of PbO decreases opacity, improves fit and gloss, but makes enamel more soluble. The following limits in composition are recommended: 0.3 to 0.7 KNaO, 1.3 to 1.8 SiO₂, 0.7 to 3 PbO, 0.0 to 0.2 B₂O₃, 0.05 to 0.15 AS₂O₃.     

Glass forming,crystallization, and physical properties of MgO-Al2O3-SiO2-B2O3 glass-ceramics modified by ZnO replacing MgO

This study focused on the glass forming, crystallization, and physical properties of ZnO doped MgO-Al₂O₃-SiO₂-B₂O₃ glass-ceramics. The results show that the glass forming ability enhances first with ZnO increasing from 0 to 0.5 mol%, and then weakens with further addition of ZnO which acted as network modifier. No nucleating agent was used and the crystallization of studied glasses is controlled by a surface crystallization mechanism. The predominant phase in glass-ceramics changed from α-cordierite to spinel/gahnite as ZnO gradually replaced MgO. The phase type did not change; however, the crystallinity and grain size in glass-ceramics increased when the glasses were treated from 1030 °C to 1100 °C. The introduction of ZnO can improve the thermal, mechanical, and dielectric properties of the glass-ceramics. The results reveal a rational mechanism of glass formation, crystal precipitation, and evolution between structure and performance in the xZnO-(20-x)MgO-20Al₂O₃-57SiO₂-3B₂O₃ (0 ≤ x ≤ 20 mol%) system.