PbO Content Research Articles

Effects of PbO on the oxide films of incoloy 800HT in simulated primary circuit of PWR

Effects of trace PbO on oxide films of Incoloy 800HT were investigated in simulated primary circuit water chemistry of PWR, also with proper Co addition. The trace PbO addition in high temperature water blocked the protective spinel oxides formation of the oxide films of Incoloy 800HT. XPS results indicated that the lead, added as PbO into the high temperature water, shows not only +2 valance but also +4 and 0 valances in the oxide film of 800HT co-operated with Fe, Cr and Ni to form oxides films. Potentiodynamic polarization results indicated that as PbO concentration increased, the current densities of the less protective oxide films of Incoloy 800HT decreased in a buffer solution tested at room temperature. The capacitance results indicated that the donor densities of oxidation film of Incoloy 800HT decreased as trace PbO addition into the high temperature water.

Structure, thermal behavior, and chemical durability of lead–calcium–phosphate glasses

ABSTRACTStructure and physical properties of 25CaO–xPbO–(75–x)P2O5 (0≤x≤35) glasses are investigated in this paper. Substitution of PbO for P2O5 in the binary 25CaO–75P2O5 glass was found to increase the density and to decrease the molar volume. Fourier transform infrared (FTIR) and Raman spectroscopies show the evolution of the phosphate skeleton when the PbO content increases: Q3 to Q2 species (0<x≤25) and Q2 phosphate network (x = 25) to short phosphate groups (x > 25) such as (P4O136−) (x = 35). The glass transition temperature first decreases with x, then increases for x values larger than 10%. The evolution of the glass transition temperatures is interpreted from the structural data: the minimum point observed in Tg is attributed to the transition of the ultraphosphate network from the network containing the modifying cations at isolated sites to a network with modifier sub-structure sharing terminal oxygens. At higher PbO content, the large increase in Tg is due to the reticulation of the phosphate network by PbO4 groups.

Determination of effective atomic number and electron density of heavy metal oxide glasses

ABSTRACTThe effective atomic number (Zeff) and effective electron density (Neff) of eight heavy metal oxide (HMO) glasses have been determined using the Monte Carlo simulation code MCNP for the energy range of 10 keV–10 MeV. The interpolation method was employed to extract Zeff and Neff values from the simulation and that calculated with the help of XCOM program. Comparisons are also made with predictions from the Auto-Zeff software in the same energy region. Wherever possible, the simulated values of Zeff and Neff are compared with experimental data. In general, a very good agreement was noticed. It was found that the Zeff and Neff vary with photon energy and do not have extended intermediate regions where Compton scattering is truly dominating; only dips slightly above ∼1.5 MeV were recorded. Zeff and Neff are found to increase with PbO and Bi2O3 contents. It was found that the Zeff value rather than the Neff value is a better indicator for PbO and/or Bi2O3 contents.

The Effect of PbO on the Physical and Structural Properties of Borate Glass System

Borate is one of the most popular oxide glass being used in glass research world wide. Due to good reputation, therefore lead sodium borate glasses with compositions (90 - x) B2O3 + 10ZnO + xPbO (where = 15, 20, 25, 30 and 35 mol %) have been prepared by using melt-quenching method. In this work, their physical and structural properties with respect to PbO content has been investigated. The densities of these glass samples were increased from 3946.2 kg/m3 to 5107.2 kg/m3 with an increase in PbO concentration. The molar volume are found to vary from 23.78 × 10-6 m3mol-1 to 24.39 × 10-6 m3mol-1 with respect to PbO content as well. The density and molar volume show inversed result respectively. The FTIR spectral analysis indicates that with the addition of PbO contents in the glass network, structural units of BO3 are transformed in BO4. There are no sharp peaks were observed in XRD patterns of the glass samples which confirmed the amorphous nature of the glass. Meanwhile, the micro hardness of these glass samples were also increased from 189 Pa to 355 Pa with increases on PbO content. The results will be discussed and presented in details.

Optical Spectroscopic Analysis of High Density Lead Borosilicate Glasses

Lead borosilicate glasses, of chemical composition 20SiO2-xPbO-(15 + x)B2O3-5WO2-10ZnO-(50-2x) Na2O (where x = 5, 10, 15, 20, 25) were prepared using the normal melt-quenching technique. The samples were examined using a Philips Analytical X-ray diffraction system in order to check their amorphous nature. The effect of increasing B2O3 and PbO content on glass transition temperature was examined using Differential Thermal Analysis measurements (DTA). The results of DTA showed that both melting and glass transition temperatures decrease with increase of lead and boron oxides. Density and its related parameters have been determined to study the effect of lead-boron content on the structural properties of the prepared samples. Based on the density and DTA results, the network forming role of Pb and B ions was proved. The optical properties of the glass samples have been obtained using UV-VIS measurements. The optical parameters, such as optical band gap, Urbach energy, refractive index, and electronic polarizability were deduced based on the optical data. The observed increase in optical band gap and decrease in Urbach energy as well as the red shift in the absorption spectra arise due to the formation of non-bridging oxygen.

Glass transition temperatures and structures of multicomponent borate glasses: Influence of modifier cation field strengths

Glass transition temperatures, Tg, are determined for a series of multicomponent borate glasses with composition xPbO·(33.33−x)Na2O·yAl2O3·1.3ySiO2·(66.67−2.3y)B2O3, (where x and y take values from 0 up to 13.5mol%, and from 0 up to 5.3mol%, respectively). For this purpose, differential scanning calorimetry is used while the structure of these glasses containing two kinds of modifier oxides — Na2O and PbO, is investigated by infrared spectroscopy. A detailed analysis of the infrared spectra reveals that at constant total content of the glass-forming oxides (B2O3, SiO2 and Al2O3) in the glasses investigated, the borate network progressively depolymerizes when Na2O is substituted for PbO. This substitution favors the destruction of the more rigid structural units and the formation at their expense of units with a lower degree of connectivity. The macroscopic manifestation of these structural changes is the steep decrease in the glass transition temperature of the glasses investigated at increasing PbO concentration. This tendency for depolymerization of the borate network is explained by the influence of the Pb2+-cations possessing substantially higher ionic field strength as compared to that of the Na+-cations.

Correlation between Chemical Durability Behaviour and Structural Approach of the Vitreous Part of the System 55P&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;5&amp;lt;/sub&amp;gt;-2Cr&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;-(43-x) Na&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O-xPbO

Various characterisation techniques were used to study the composition of the glass series 55-P2O5-2Cr2O3-(43-x) Na2O-xPbO (with 8 ≤ x ≤ 38; mole %) in terms of chemical durability, IR spectroscopy and scanning electron microscopy (SEM). The change in the dissolution rate as a function of time when the studied glasses were kept submerged in distilled water at 90°C for 20 days showed an improvement in the chemical durability when Na2O content was substituted to PbO content. IR spectroscopy revealed a structural change from ultraphosphate groups to pyrophosphate, orthophosphate and probably ring metaphosphate groups. SEM revealed the existence of two phases: a vitreous phase and a crystalline phase. The presence of Cr2O3, even in small amounts, seems to play an important role in the formation of crystallites in the glass network. The improved chemical durability is attributed to the replacement of the easily hydrated Na-O-P and P-O-P bonds by covalent and resistant Pb-O-P bands. Both the increase in PbO content and in the Pb + Cr/P ratio causes an increase in the number of covalent Pb-O-P and Cr-O-P bonds, making the glass structure more rigid. The increase of the covalent Pb-O-P bands leads to a clear evolution of the structure and chemical resistance, caused by grain-boundary resistance as a result of glass crystallisation. The IR spectra indicate that the increase in PbO content favours the formation of isolated PO3-4 orthophosphate groups at the expense of pyrophosphate groups. The radical change in the structure from ultraphosphate groups to pyrophosphate and orthophosphate groups seems to be the cause of the formation of crystallites. The existence of crystallites in these glasses results in a marked improvement in their chemical durability. However, when the crystallites exceed a certain limit, the equilibrium between the glass bath and these crystallites is no longer maintained; we notice, once, a decrease in the chemical durability.

Electrical conductivity, density and liquidus temperature of KCl–PbCl2 equimolar melt with addition of lead oxide

The paper studies the effect of an additive component PbO (up to 8,1 mol.%) on physical and chemical properties of the KCl–PbCl2 molten system. The study experimentally measures temperature of primary crystallization of selected electrolyte compositions. It uses the method of impedance measuring in cells with parallel electrodes and finds dependencies of electrolyte conductivity on the temperature and PbO content. It uses Archimedean method to measure temperature dependence of the KCl–PbCl2 equimolar melt density containing up to 8,1 mol.% of lead oxide, and calculates values of molar volumes. The paper demonstrates that concentration dependence of the molar volume is of an extreme nature.

Low-loss insulating-conductive ceramic composite with giant permittivity and high permeability using glass phase as separating layer

The control of dielectric loss in insulating-conductive ceramic composites is of great significance for the enhancement of the comprehensive performance of next-generation devices. In this work, a low-activity precursor co-sintering method was proposed to prepare low-loss BaTiO3(BTO)/Ni0.5Zn0.5Fe2O4(NZFO) ceramic composite by using 2PbO–B2O3(PBO) glass as insulating layer. XRD and SEM were used to reveal the phase composition and the morphology of the composite. Results showed that the conductive networks can be successfully cut off by PBO glass separating layer inside the composite (1−x)BTO/xNZFO where x is the molar fraction of NZFO ferrite, giving rise to decreased dielectric loss in a wide compositional range between x=0.1–0.7 while retaining considerable effective permittivity and initial permeability. Excess amount of PBO glass is not favorable for the formation of separating layer due to the chemical reactions occurring between the constituent phases and the glass phase; meanwhile, accompanied by the decrement in dielectric loss, the initial permeability of the composite decreases linearly with increasing PBO content.

Radiation-induced changes in electrical conductivity and structure of BaPbO3 after γ-irradiation

Several barium plumbate (BaPbO3) solid samples, made from PbO and BaCO3 powder by chemistry liquid-phase coprecipitation, were investigated before and after γ-irradiation. The solid samples were irradiated by a 60Co γ-irradiation source whose dose rate is about 0.7 kGy per hour. The irradiation times were 0, 72, 144, 216, 288 and 360 h. Then, the four-probe method, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to indicate the changes in electrical conductivity and microstructure of BaPbO3 after γ-irradiation. The XRD results indicated that the content of PbO was reduced as the irradiation dose was increased and eventually vanished from the surface of samples. However, there was no new obvious substance phase found from the XRD atlas. It seems that the PbO transformed into nearly amorphous Pb5O8. The conjecture could be proved by the results of annealing experiment and SEM. The XPS results seem to show that the microstructure of BaPbO3 was slightly changed.

FTIR of binary lead borate glass: Structural investigation

The glass samples were prepared according to the following formula: (100−x) B2O3 – x PbO, where x = 20–80 mol% by melt quenching method. The density of the prepared samples was measured and molar volume was calculated. IR spectra were measured for the prepared samples to investigate the glass structure. The IR spectra were deconvoluted using curves of Gaussian shape at approximately the same frequencies. The deconvoluted data were used to study the effect of PbO content on all the structural borate groups. Some structural parameters such as density, packing density, bond length and bond force constant were theoretically calculated and were compared to the obtained experimental results. Deviation between the experimental and theoretically calculated parameters reflects the dual role of PbO content on the network of borate glass.

Structural and properties of heavy metal oxide Faraday glass for optical current transducer

The influences of PbO, Bi2O3 and GeO2 contents on mechanical, thermal, magneto-optical and structural properties of PbO–Bi2O3–GeO2–B2O3 glass system were investigated. A magneto-optical current transducer MOCT prototype with sensitivity of 7.56nW/A was constructed based on selected glass with good properties.

Phase Equilibria and Interaction Between the CsCl–PbCl2–PbO System Components

Abstract Thermal analysis was applied to determine liquidus temperatures in the CsCl–PbCl2–PbO system, with the PbO concentration ranging from 0 to 20 mol%. The temperature dependence of the PbO solubility in the CsCl–PbCl2 eutectic melt was studied, and the thermodynamic parameters of the PbO dissolution were calculated. The type, morphology, and composition of oxychloride ionic groupings in the melt were determined in situ using Raman spectroscopy.

Ceramics from the Alcazar Palace in Seville (Spain) dated between the 11th and 15th centuries: Compositions, technological features and degradation processes

For the purpose of chemical characterization, a selection of 29 ceramic fragments from the 11th to 15th century has been made from materials excavated in the Seville Alcazar Palace. The PIXE elemental analysis results indicated that the ceramic bodies can be divided into four groups. The XRD identification of the phases present in the bodies revealed differences in the firing temperatures. The PIXE analysis of the glazes revealed variable PbO and SnO2 contents. The latter component was not detected in all the glazes. Cu, Co, Mn, Fe and Sb elements were associated with green, blue, black and yellow colours, respectively. Some glazes were covered by iridescent layers constituted by lead carbonate and phosphates due to alteration of the glazes. It was also possible to detail the microstructure and composition of the ultimate surface layers responsible for the lustre effect observed in two of the ceramic samples using PIXE and Rutherford backscattering spectrometry (RBS).

English

Glass formation has been examined in the system 15PbO.xPbCl(2).(85-x)PbBr2 (where 0 <= x <= 25)where the PbO concentration is kept constant while PbCl2 and PbBr2 concentrations are varied. The glasses have been examined using thermal and spectroscopic techniques. T-8, Delta C-p, refractive index, optical basicity have been found to remain unaffected by the composition which is a curious feature of these glasses. It is found that there is a wide infrared window available for use in the investigated glasses. The IR window extends from 1000 to 1500 cm(-1) and in glasses where PbCl2 is less than 20 mol%, the window extends up to 2260 cm(-1). X-ray photoelectron spectra (XPS) revealed that the 4f(5/2) and 4f(7/2) peaks due to f-level transitions have a constant difference in energies, but with energy and FWHM values that varying sensitively and systematically with composition. The observations are discussed and suitable explanations are provided.

A-site stoichiometry and piezoelectric response in thin film PbZr1−xTixO3

Lead zirconate titanate (PZT) films with Zr/Ti ratios of 52/48 and 30/70 annealed at varying partial pressures of PbO within the perovskite phase field exhibited permittivities of 1150 and 600, respectively, with loss tangents of 0.02. Many of the functional properties, including the permittivity, piezoelectricity as indicated via the Rayleigh coefficients, and the aging rates were found to be weakly dependent of the lead content in the single phase field. Minor polarization–electric field hysteresis loops and piezoelectric coefficient e31,f values after a hot poling process suggest that the point defect helps stabilize the aligned domain states. Measurements of the local nonlinear response show an increased low response cluster size with decreasing PbO content, indicating that PbO deficiency acts to reduce domain wall motion where it is already low.

Synthesis and characterization of spark plasma sintered Ti3SiC2/Pb composites

Dense Ti3SiC2/Pb composites were successfully synthesized from Ti3SiC2 and PbO powders by spark plasma sintering. The reaction mechanism was discussed on the basis of thermodynamic principles. The sintering process was optimized and the sintering characteristics of the Ti3SiC2–PbO system were studied. The effects of PbO content on the density, micro-hardness, mechanical and tribological properties of the composites were investigated. Micro-hardness, flexural strength and compression strength of the composites were found to increase with the increase of PbO content, due to the grain refinement of Ti3SiC2. The maximum values of the flexural and compression strength were 480 and 1645MPa, respectively. Additionally, the wear rates of Ti3SiC2/Pb—Inconel 718 alloy tribopairs decreased with the increase of PbO content at room temperature.

Thermodynamic model of lead oxide activity in PbO–CaO–SiO2–FeO–Fe2O3 slag system

According to the ion and molecule coexistence theory, a thermodynamic model of lead oxide activity in PbO–CaO–SiO2–FeO–Fe2O3 slag system was established at the temperature of 1273–1733 K. The activities of PbO in slag were calculated, and their equal activity curves were plotted. The influences of slag basicity Q, iron oxide rate R and temperature T on activity NPbO and activity coefficient γPbO were also investigated. Results show that the calculated values of γPbO are in good agreement with the reported experimental data, showing that the model can wholly embody the slag structural characteristics. NPbO departures positively from Raoult values, and increases with increasing PbO content in slag but changes little with T. γPbO increases with increasing Q, and goes through the maximum with increasing R for basic slag (Q<0.3). Results can be applied to the thermodynamic research and operational optimization of modern lead smelting technologies.

Potentiostatic electrodeposition of a novel cost effective PbO2 electrode: Degradation study with emphasis on current efficiency and energy consumption

Electrochemical oxidation is developing as a prominent technology for the degradation of organic contaminants. Even though many electrode materials proved efficient in degradation of organics, the quest for a stable, low cost electrode material is still at large. The present study attempted the development of an efficient and cost effective electrode material, PbO2 electrodeposited on mild steel. The optimum operating range of parameters for the electrodeposition was established. Compact structure of PbO2 was obtained up to an applied voltage of 2V. Concentration of PbO also affected the morphology at lower concentration. XRD analysis depicted that the deposit consists of a mixture of α and β-PbO2, and non-stoichiometry of the deposited PbO2 was proved by EDX analysis. Applied current, initial dye concentration, supporting electrolyte type and concentration affected the reaction kinetics, current efficiency and energy consumption in the degradation of methyl orange on MS/PbO2 electrode. A current efficiency of 57% and corresponding energy consumption of 42kWhkgCOD−1 treated was obtained at 88% COD degradation for an initial COD of 292mgL−1 with current density of 2.87mAcm−2. The newly developed MS/PbO2 electrode had current efficiency and energy consumption comparable with data reported in literature at similar degradation conditions.

Effect of Modification of an InP Surface by (V2O5 + PbO) AND (NiO + PbO) Oxide Mixtures of Different Compositions on the Thermal Oxidation Process and the Characteristics of the Formed Oxide Films

Vanadium oxide is an active chemostimulator of the oxidation of InP. This fact is manifested by an abrupt drop in the effective activation energy (EAE) of the process, a significant increase in the rate of growth of the thickness of the films (by 70 to 110%), and an improvement in their dielectric properties, due to effective bonding of the indium to its oxide form. All of this is evidence of a synchronous catalytic mechanism of oxidation of InP with deposited V2O5 layers of nanosize thickness. The use of a V2O5 + PbO mixture makes it possible to track the dynamics of decrease of catalytic action of V2O5 during oxidation under gradual increase in the PbO content of the mixture, with PbO entering as the oxygen transit agents for the InP components. The NiO + РbО mixture is composed of two oxides, both of which are oxygen transit agents. In view of this, the aim of the present work is to elucidate the combined chemostimulative action of nanosize layers of the oxide mixtures V2O5 + PbO and NiO + PbO, magnetron sputtered onto an InP surface, on the thermal oxidation of the obtained heterostructures. The practical absence of consumption of vanadium oxide (x-ray phase analysis data) confirms the presence during thermal oxidation of the (V2O5 + PbO)/InP heterostructures of a regeneration cycle of the V2O5 catalyzer. The lead oxide is fixed only at the early stages of the process, which is evidence of consumption of the PbO transit agent during InP oxidation. For (NiO + РbО)/InP (86 or 52 mole% РbО) heterostructures, consumption of NiO and PbO during the thermal oxidation process (XRD data) has been established, which confirms that the process proceeds via a transit mechanism. For oxide/phosphate films formed by oxidation of (V2O5 + PbO)/InP heterostructures, the size of the individual crystallites lies within the limits 100–150 nm (AFM data), whereas for (NiO + РbО)/InP heterostructures crystallites in the size range 150–200 nm are present in the oxide films.