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The present study replaced 3.30 and 9.00 mol.% BaO for CaO in a SiO2–B2O3–Al2O3–CaO–Na2O–P2O5 bioactive glass system used for implant coating applications. Variations of the glass structure, thermal properties, cytotoxicity, and radiopacity of glasses were studied. As demonstrated by the results, upon adding barium oxide to the glass structure, the weight density increased significantly, while a slight decrease in oxygen density was determined. Introducing barium oxide into glass composition did not cause any considerable change in the spectra of FTIR and Raman. It was demonstrated that the amount of bridging oxygen in the glass structure remained quite unaffected. The hot stage microscopy evaluations revealed further shrinkage of barium-containing frits due to lower viscosity and hence, higher viscous flow of these glasses. By substituting barium oxide for calcium oxide and increasing its concentration, the glass transition temperature (Tg) and the dilatometric softening temperature (Td) decreased, while the thermal expansion coefficient increased. Moreover, upon substituting 9 mol.% barium oxide for calcium oxide, a 30 °C reduction in maximum sintering temperature (Tms) of the glass was obtained, whereas the shrinkage rate was increased 1.7 times. It was indicated that the sintering process of barium-incorporated glasses would easily proceed without any phase crystallization. The barium-incorporated glasses exhibited more radiopacity. Additionally, no cytotoxic effect was caused by the substitution, and the Ba-containing glasses could be used for biomedical applications and implant coating as well.

A complete thermodynamic analysis of chemical transformations in a BaO–B2O3–C system is performed in a temperature range of 1400–3000 K using the Terra software. Even before starting a reduction processes, the products of the reactions of boron and barium oxides are ortho-Ba3B2O6 and barium metaborate BaB2O4 with crystallization temperatures of 1656 and 1378 K, respectively. The reduction with carbon of a mixture of the oxides with high (90BaO + 10B2O3) and low (35BaO + 65B2O3) contents of barium oxide is studied. In all cases, the reaction products can be carbide BaC2, barium hexaboride BaB6, and boron carbide B4C. Barium carbide BaC2 prevails in the smelting products of the processed mixture rich in barium oxide, whereas barium hexaboride predominates in the processed mixture rich in boron oxide. The formation of barium borates impedes reduction because of the decreased reactivity of BaO and B2O3. Being strong basic (BaO) and acidic (B2O3) oxides, they form stable compounds. The temperature of the onset of barium reduction to BaC2 from BaO is 1500 K, and that from Ba3B2O6 is 2200 K. The combined reduction of barium and boron occurs from barium borates to form BaB6. For both mixtures, the formation of barium hexafluoride in the smelting products is detected at 2300 K. The presence of BaB6 in the condensed phase indicates that a complex ferroalloy simultaneously containing boron and barium, which are known as efficient alloying and modifying elements, can be produced. The method of mathematical experiment planning is applied to a numerical simulation of the technology. Equations are derived for the dependences of the amounts of the formed phases on the BaO and B2O3 consumptions and temperature. The entire oxide composition range is studied in accord with the phase diagram of the BaO–B2O3 system. The equations make it possible to select the temperature and charge smelting conditions to achieve the required compositions of the condensed phases. The results of numerical experiments can be applied to the production of boron–barium alloys and the synthesis of high-temperature materials based on BaB6, BaC2, and B4C.

Iodine has the potential to be a mission-enabling propellant for electric propulsion; however, iodine as the working gas in a hollow cathode presents many challenges. Iodine propellant was compared...

The world is challenged with depletion of non-renewable fossil fuel and environmental pollution. Thus, this research was emphasized on converting refined used cooking oil to safer and low toxicity biodiesel by base-catalyzed transesterification reaction. Alumina supported magnesium, calcium, strontium and barium oxide-based catalysts with iron as its dopant were optimized according to various calcination temperatures and iron loadings. The optimum conditions over potential catalyst was achieved with 20 wt% of Fe loading for Fe/Ba/Al2O3 catalyst calcined at 800 °C which gave the maximum biodiesel production of 84.02%. Characterization of catalyst carried out by XRD showed that the 20Fe:80Ba/Al2O3 catalyst calcined at 800 °C had a polycrystalline structure with high BET surface area (133.59 m2/g) while FESEM analysis displayed a morphology of uniform plate-like shape grains with fine particles in the range of 55–60 nm. CO2-TPD results showed that the catalyst exhibited highest basicity of 2.5854 mmol/g, while TGA analysis proved that 800 °C was the optimum calcination temperature. The transesterification process of refined used cooking oil to produce high yield biodiesel was effectively attained using 20Fe:80Ba/Al2O3 catalyst.

In creating the next generation of crystalline silicon (c-Si) solar cells, the goals are to improve energy conversion efficiency and reduce costs. Here, we demonstrate all-room-temperature-processe...

A model of the surface structure of a palladium–barium cathode is proposed and the Dionne secondary electron emission model is used to calculate the dependence of the secondary electron emission coefficient of barium oxide crystallites forming on the surface of a cathode during its thermal activation on the temperature and oxygen vacancy concentration in the oxide. It is shown that the emission properties of a palladium–barium cathode significantly depend on both the emission properties of barium oxide crystallites and the cathode relative surface area occupied by them. The theoretical nomograms are built that relate the measured surface-averaged work function to the secondary electron emission coefficient of a palladium–barium cathode; the nomogram parameters are the temperature, oxygen vacancy concentration in barium oxide crystallites, and the relative cathode surface area occupied by them.

The effect of microimpurities in barium oxide on the parameters of its electronic structure and, accordingly, on the work function is demonstrated experimentally and substantiated theoretically considering the decisive role of oxygen vacancies in the formation of thermoemission properties of barium oxide crystallites. It is found that depending on the crystallite size in the nanosize region, scandium microimpurities in barium oxide crystallites lead to the formation of various types of domains enriched in scandium atoms and characterized by a smaller work function on the crystallite surface. A physical model is proposed and the dependence of the work function of the domains on the temperature and concentration of oxygen vacancies in barium oxide crystallites doped with scandium atoms is calculated theoretically for different types of domains. The experimental technique permitting a correct physical determination of emission properties of scandate cathodes is formulated.

The aim of this research is to show the effect of zirconium silicate addition on sintering and physicochemical properties of glass-ceramic materials from the SiO2–Al2O3–Na2O–K2O–CaO–MgO–BaO system. This paper presents the results of the most important techniques used to understand the sintering process, i.e. thermal differential analysis, dilatometry measurements and hot-stage microscopy. Additionally, the following techniques have been used: X-ray diffraction (XRD) and scanning electron microscopy with a micro-analyser (SEM-EDS), and in order to obtain surface physicochemical properties: laser confocal microscopy, glossmetry, and spectrophotometry. By changing the initial composition and thermal treatment of glass-ceramic materials it is possible to shape parameters of final products which leads to obtaining a great variety of applications.

The effect of microimpurities on the electronic structure of barium oxide has been studied using optical and electron spectroscopy. As was shown previously, oxygen vacancies play a decisive role in the formation of the emission properties of barium oxide crystallites; however, the possible role of microimpurities in barium oxide crystallites was not considered. It has been established that some microimpurities, including nickel, scandium, and combination of calcium and strontium, order oxygen vacancies in barium oxide crystallites, which directly affects oxygen diffusion in them. Nickel and scandium impurities form additional surface states near the edge of the valence band, which is accompanied by a decrease in the electronic work function of a cathode material.

The effect of BaO content on the glass-forming ability, glass stability and structure of tellurite–phosphate oxide glasses in the 70TeO2–10P2O5–(20-x)ZnO–xBaO (x = 0, 5 and 10 mol%) system has been discussed. From the differential scanning calorimetry, the glass transition (Tg), crystallization (Tc) and the melting (Tm) temperatures were estimated. The decrease in reduced glass transition temperature (Trg) and glass-forming tendency parameter (Kh(Tc1)) with addition and increasing BaO caused a decrease in the glass-forming ability of glasses. It was also found that the thermal stability of these glasses against crystallization decreased with increase in BaO concentration into chemical composition of base glass, i.e., glass without barium oxide. The FTIR spectra were measured to understand the structure of the obtained tellurite–phosphate oxide glasses. The results have shown that phosphorous and tellurium ions were taken part in the formation of the glass network of the studied glasses. The addition of BaO caused significant changes in the FTIR spectra of glasses. More and more TeO3 and TeO3+δ units and PO42− groups (Q1 units) were created when the BaO was added into the chemical composition of the base glass. Increasing barium ions content into the chemical composition of glasses caused depolymerization of the tellurite–phosphate oxide glass network.

It is a major challenge to reduce water diffusion through hydrophilic polymers like epoxies without affecting their thermomechanical performance. Herein, both graphene oxide (GO) nanosheets and barium oxide (BaO) microparticles were incorporated together into epoxy to develop water resistant epoxy/BaO/GO nanocomposite. The manuscript signifies the role of these fillers in reducing water diffusion through epoxy matrix without deterioration in its basic thermal and mechanical properties. Morphological studies of epoxy/BaO/GO nanocomposites revealed the presence of uniformly distributed micro/nano-clusters of graphene oxide sheets and BaO. This enhanced the hydrophobicity of the nanocomposite with a water contact angle of 131.7°. The BaO/GO micro/nano-clusters also created a barrier to the diffusion of water molecules which reflected in the lower diffusion coefficient of epoxy/BaO/GO nanocomposite. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and thermomechanical (TMA) analysis has been carried out to investigate the viscoelastic, thermal stability, and dimensional stability of the prepared composites. Good viscoelastic performance of epoxy/BaO/GO nanocomposite with balanced thermal stability and dimensional stability has been confirmed. The developed water resistant epoxy nanocomposite is suitable to be used in areas where moisture attack is a serious concern.

This work presents an extensive study on the effect of various parameters (concentration, solvents, infrared irradiation, salts, and temperature variation) on the barium oxide nanoparticles decorated multi-wall carbon nanotubes. A simple and effective technique involving infrared irradiation and diazonium chemistry was utilized. The materials were characterized using X-ray photoelectron spectroscopy, Raman spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, powder X-ray diffraction, thermogravimetric analysis and ultraviolet–visible spectrophotometry. A homogeneous distribution of amorphous barium oxide nanoparticles onto carbon nanotubes was observed. Particles size varies from 3–18 nm (Gaussian mean diameter ∼11.7 nm). Thermogram showed that nanoparticles act as a catalyst to decompose nanotubes even at lower temperature. A common dye pollutant that is methylene blue was considered to evaluate the ability of the present composite for water purification for the first time. As our technique is also applicable to bulk synthesis, it can be worthful for wide range of nanotechnological applications.

This paper presents a study on the possibilities of magnetron enhancement through different materials of magnetron's cathode structure. Magnetron structure is built in COMSOL to testify the performance of different content such as Barium Oxide (BaO) and Gallium Nitride (GaN). The essential procedure of getting the simulation result presented. Comparison of Electric Field (EF), Electromagnetic Compatibility (EMC), and heat density for both materials compared between each content for low power and high-frequency microwave power generation. The application of the enhancement applicable for microwave generation of 5W at 2,450MHz operation, precisely long-distance wireless mobile charging usage.

The deviation of the I–V characteristics of cathode materials in microwave devices from the Schottky law is caused by the occurrence of drift and diffusion of oxygen vacancies in barium-oxide crystallites, which are emission-active components of the cathode materials. The processing of experimental dependences using the proposed mathematical tools makes it possible to determine the barium-oxide-crystallite thickness and diffusivity of oxygen vacancies. The known diffusivity allows determining the presence of microimpurities in barium oxide, which affect its emission properties.

A theoretical model of the cathode sheath of a normal glow discharge for the cathode with a thin insulating film is developed. In addition to the ion-electron emission, the field emission of electrons from the metal cathode substrate into the film under the action of the strong electric field generated in the insulator is taken into account in the model. It is established that the influence of the field electron emission on the glow discharge characteristics is determined by the emission efficiency of the film, equal to the fraction of electrons going out of it into the discharge volume. It is demonstrated that the calculated normal cathode voltage drop in the discharge in argon for the cathode with a barium oxide film coincides with its measured value for the emission efficiency of the film of the order of 0.1, which is in agreement with its experimental estimations.

The electronic structure of barium oxide crystallites determining the emission properties of both dispenser and scandate cathodes has been studied using electron spectroscopy for chemical analysis, electron energy loss spectroscopy, and optical spectroscopy. It has been established that the other elements (calcium, aluminum, scandium, and tungsten) contained in cathode materials are diluted in barium oxide and significantly affect its electronic structure and, consequently, emission properties. The obtained results give an idea about the physical and physicochemical mechanisms of the effect of scandium on the reduction of the work function of scandate cathodes relative to that of the cathodes of other types.

Nowadays, nuclear power plants are widespread around the world and research is of great interest. Together with nuclear research, shielding of different types of radiation is an important current topic of research aiming at their safety. Portland cement has been an elementary building material for centuries. Since barium is very efficient in shielding different types of radiation, it can be assumed that the radiation shielding capability of cement can be improved by incorporation of barium. This work deals with the influence of barium oxide, added in the form of barium carbonate and sulphate, on the formation and properties of Portland clinker. The structure of burnt clinkers and the ratio of clinker phases were studied by polarizing microscopy and by X-ray diffraction. With increasing barium content, the alite-belite ratio decreases and the content of free lime gradually increases. Moreover, sulphates induce the growth of alite crystals. The ability of barium to be a part of the clinker minerals was observed by scanning electron microscopy. Belite and clinker melt contain the highest amount of barium, but aggregates of barium oxide are formed in the clinker melt. Furthermore, the rate of alite crystallization was studied under isothermal conditions.

The article deals with heat liberation of barium cements, which influences the crack formation in mass concrete structures. The results of heat release and physical testing of barium cements with a different content of BaO are presented in this paper. The strength of cement and its setting time will decrease significantly, if the content of BaO in clinker is high (about 47%). This cement is characterized by a low water requirement and heat liberation. Properties of cement with a low content of barium oxide (5.5%) are close to the properties of the standard Portland cement. In this case heat liberation is low in the initial period of hardening, but at the later stage it exceeds the exotherm of a reference sample. A small amount of BaO in cement clinker reduces the exothermic effect and increases the thermal crack resistance of concrete.

Glass–ceramic materials due to the various physical and chemical parameters have a more and more wide application in various areas of engineering. This paper presents a glass–ceramic material originating from the Al2O2–SiO2–Na2O–K2O–CaO/MgO modified by the addition of barium oxide. For the oxide composition which the molar ratio of SiO2/Al2O3 is constant and equal to 6.42, and containing 0.375 mol% of Na2O + K2O and 0.625 mol% of MgO was introduced barium oxide in quantities: 4, 9 and 14 mass%. For research of the sintering process, the following thermal analysis techniques were used: differential scanning calorimetry, dilatometry measurement and hot-stage microscopy. Analysis of the observed thermal transitions, marked on the respective charts, allows for appropriate design of the sintering curves in order to obtain a material with a high degree of crystallisation. The results of thermal analysis were compared with the phase compositions determined by X-ray diffraction and images from electron scanning microscopy of polished samples of glass–crystalline materials. Phenomena related to the influence of addition of barium oxide and heating treatment are analytically discussed.

Portland clinker is thanks to its large-scale production a continuously studied topic. Clinker, or Portland cement, is used for construction purposes or for insulation and special applications. One of these special applications could be shielding of different types of radiation by making use of the content of barium ions. The present article examines the influence of barium oxide on the formation and properties of Portland clinker, which could be, by incorporation of barium ions into the system, used as a binder for buildings resistant to various types of radiation. Barium sulphate and barium carbonate were added to the raw meal in order to prepare clinkers with different content of barium oxide. The effect of barium on the formation of clinker phases was studied (by XRD – Rietveld analysis and by the microscopic point counting method), as well as the rate of alite formation under isothermal conditions. Furthermore, the ability of barium to become a part of clinker minerals was studied by SEM with EDS.

In this article, copper zinc phosphate glass doped with 5 % barium oxide has an amazing optical property due to its application as bandpass filters. Typically, the glass conventional casting with chemical composition 42P2O5–(14- x)Na2O–39ZnO–5BaO–xCu2O where (x = 2, 4, 6, 8 and 10) was formed. The density was measured using the conventional Archimedes method and the molar volume was calculated. The change of glass structure was investigated using X-ray diffraction analysis (XRD). Distinctly, the results revealed that no crystal growth in all glass systems was observed. The density of glass samples was increased whereas the molar volume was decreased with increasing copper content. The absorption, transmission and reflection were measured and some other optical properties were calculated like UV cut-off, and IR cut-off. For instance, the visible cut-off started from 462 to 532 nm while the IR bonds were initiated at 630 to 1200 nm with 6 to 10 % Cu2O concentration.

The effect of the BaO addition on the microstructure and structure of the glasses from the K2O–MgO–CaO–Al2O3–SiO2-(BaO) system was investigated in this study. The results were obtained by testing the crystallization capability of the glasses during the fast-firing cycle. Thermal analysis proved a high tendency to crystallize the tested glasses/frits. X-ray analysis showed the presence of diopside and anorthite as the main crystalline phases in all glazes obtained from the tested glasses. Microscopic observations showed that barium oxide introduced in the range of 0.4–2.1 mol% into the examined system strongly influences the number and size of crystalline phases. The introduction of 2.1 mol% BaO into the composition also resulted in crystallization of celsian. The thermal characteristic of the glasses was carried out using differential scanning calorimetry (DSC) and the crystalline phases were determined by X-ray diffractometry. The glaze microstructure was investigated by scanning (SEM) and transmission electron (TEM)microscopy. Additional information on the structure of frits was derived from mid-infrared (MIR) and Raman spectroscopy.

Barium-titanium-boro-tellurite glasses containing the transition metal (TM) Cr3+ ions with different BaO mol% were prepared using the melt quenching method. From the XRD, SEM and EDS studies, it was confirmed that the prepared glasses were impurity-free and their atomic arrangement is non-crystalline in nature. The UV–visible spectra exhibited a dominant high absorption band corresponding to the enrgy of ~15974 cm−1 and three weak low-intensity bands around 23641 cm−1, 14881 cm−1 and 14306 cm−1. The identified bands are assigned to 4A2g→4T2g (F), 4A2g→4T1g (F), 4A2g→2T1g (G) and 4A2g→2Eg (G) transitions respectively. The optical band gap values are increasing while the refractive index values are decreasing with increasing BaO content. The crystal-field parameter Dq values and Racah parameter (B) values were found to change non-linearly with the barium oxide content which suggests a change in the environment around Cr3+ ions. From the value of Dq/B, it can be concluded that the Cr3+ ions are localized in the weak crystal field sites. The EPR spectra which were recorded at X-band frequencies exhibited four resonance signals at g 1 ≈ 1.97, g 2 ≈ 2.38, g 3 ≈ 4.25 and g 4 ≈ 5.23. The theoretical g-values were evaluated from the Macfarlane's perturbation formulae. The FTIR and Raman spectra show broad peaks which are the characteristic features of the prepared glass component vibrating modes.

We examined the influence of barium oxide addition on the structure and properties of SiO 2 –Al 2 O 3 –Na 2 O–K 2 O–MgO glass–ceramics. Glass–ceramics were prepared with constant SiO 2 /Al 2 O 3 and Na 2 O/K 2 O ratios of 6.5 and 1.04, respectively, and the MgO content was maintained at 10.56 wt%. The barium oxide content was set at 4 wt%, 9 wt%, and 14 wt%. The weight ratios were recalculated from the BaCO 3 added. To determine the microstructure of the glassy materials, scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), X-ray diffraction (XRD), medium (MIR) and far infrared analysis (FIR), and Raman spectroscopy were used. Significant differences were observed in the phase composition and in the silica–alumina-oxide network of the glassy phase, which could be related to changes in the amount of barium oxide. The characteristic temperatures (beginning of sintering, sphere, half-sphere and melting), which were measured by using hot stage microscopy and dilatometry, also showed changes.

This article focused on effect of the content of barium oxide on microstructure of the glass–ceramic materials based on the system SiO2–Al2O3–Na2O–K2O–CaO. The following characterisation techniques have been used: X-ray diffraction (XRD), scanning electron microscopy with micro-analyser (SEM–EDS), mid-infrared analysis (MIR), far-infrared analysis (FIR) and Raman Spectroscopy. Significant differences were observed in microstructure of silica–alumina network of glassy phase and phase composition related to changes in the amount of the barium oxide additive. Discussed results are part of a larger project implemented under the PBS Applied Research Programme, in order to determine the compositions of glass–ceramic materials with potential application as a chemically resistant hard coatings or/and resistant to thermal shock or as construction materials.

Belite-barium calcium sulfoaluminate cement is a new type of cement characterised by low energy consumption and low carbon dioxde emissions, but the slow hydration of the belite phase leads to a slow mechanical property gain at early ages compared with ordinary Portland cement. A doping technique has been proposed as one option to promote its reactivity. Strontium slag, a kind of chemical industrial waste produced from the manufacture of strontium salt, has a high level of emissions in China. In this study, the influence of strontium oxide on the formation mechanism of dicalcium silicate with barium oxide and sulfur trioxide, which are both in excess in belite-barium calcium sulfoaluminate cement clinker, is investigated. Results show that strontium oxide accelerates the decomposition process of calcium carbonate, and its final decomposition temperature can be lowered by 67°C. Strontium oxide decreases the formation rate of dicalcium silciate at the same temperature, but the amount of total dicalcium silicate formed can still be as high as 94·5 wt% at 1350°C. Moreover, it is revealed that strontium oxide plays a significant role in stabilising β-dicalcium silicate, and reduces γ-dicalcium silicate by about 40%. This study could lead to environmental benefits and cement performance improvement.

A simple, reproducible and efficient technique to decorate multi-wall carbon nanotubes (MWCNTs) with barium oxide nanoparticles (BaO NPs) using infrared (IR) irradiation is developed. NaOH treatment leads to the purification of MWCNTs (p-MWCNTs). Functionalizing p-MWCNTs with tricarboxylic aryl diazonium salts generated in-situ and then reacting it with barium acetate in the presence of IR irradiation is the key step in efficiently impregnating p-MWCNTs-D3 with barium acetate (p-MWCNTs-D3/BA). Materials are characterized using XPS, TEM and PXRD. Homogeneous distribution of BaO NPs on MWCNTs is evidenced, with a Gaussian mean diameter of 5.1 nm. This method is also applicable to large scale preparation which opens interesting perspectives for nanotechnology applications.

An effective approach to prepare silicon nitride-barium aluminum silicate (Si3N4/BAS) composites by freeze gelation was described. Utilizing the gelation of particulate silica sol by freezing to solidify ceramic slurry, in the forming and drying process, the cracking and warpage of green body were avoided, and the shrinkage rate was 0.6%. The added barium oxide and alumina absorbed silica in sol to prepare Si3N4/BAS glass ceramic matrix composites, and the flexural strength, work of fracture and density of Si3N4/BAS composites were 342 MPa, 181 J/m(2) and 3.0 g/cm(3), respectively. (C) 2015 Elsevier B.V. All rights reserved.

International audience; A two dimensional axisymmetric quasi-neutral fluid model of an emissive hollow cathode that includes neutral xenon, single charge ions and electrons has been developed. The gas discharge is coupled with a thermal model of the cathode into a self-consistent generic model applicable to any hollow cathode design. An exhaustive description of the model assumptions and governing equations is given. Boundary conditions for both the gas discharge and thermal model are clearly specified as well. A new emissive sheath model that is valid for any emissive material and in both space charge and thermionic emission limited regimes is introduced. Then, setting the emitter temperature to an experimentally measured profile, we compare simulation results of the plasma model to measurements available in the literature for NASA NSTAR barium oxide cathode. Qualitative discrepancies between simulation results and measurements are noted in the cathode plume regarding the simulated plasma potential. Motivated by experimental evidence supporting the occurrence of ion acoustic instabilities in the cathode plume, an enhanced model of electron transport in the plume is presented and its consequences analyzed. Using the obtained plasma model, simulated quantities in the plume are qualitatively comparable with measurements. Inside the cathode, the simulated plasma density agrees well with measurements and is within the ±50 % experimental uncertainty associated with these measurements. A comparison of simulation results of the full coupled cathode model for the NASA NSTAR cathode with experimental measurements is presented in a companion paper, as well as a physical analysis of the cathode behavior and a parametric study of the influence of the operating point and key design choices.

The key-requirements for glass ceramic sealing materials to achieve high efficiencies in planar solid oxide fuel cells are leak tightness, high insulating resistance, and low reactivity in contact with the anode or cathode gases and the interconnect material. Therefore SCHOTT has developed special glasses and glass-ceramics for chromium alloys, like Cr5FeY (CFY, Plansee SE). Especially the CFY material requires adapted sealing materials due to its lower coefficient of thermal expansion (CTE) compared to ferritic stainless steels and the possibility for interface reactions originating from the high chromium content and the glass seal components. In this study, new glass-ceramic sealing materials for chromium containing alloys are presented. Results show that barium-free glass-ceramics are advantageous when sealing high chromium alloys in terms of interface reactions. Because of the absence of barium oxide, formation of detrimental chromate phases at the interface was avoided. The new glasses show low porosity, high hermeticity, and strong bonding toward the CFY material, fulfilling the requirements of SOFC sealants.

To support the operation of the HERMeS 12.5 kW Hall Thruster for NASA's Asteroid Redirect Robotic Mission, hollow cathodes using emitters based on barium oxide impregnate and lanthanum hexaboride are being evaluated through wear-testing, performance characterization, plasma modeling, and assessment of system implementation concerns. This paper will present the development approach used to assess the cathode emitter options. A 2,000-hour wear-test of development model barium-oxide-based (BaO) hollow cathode is being performed as part of the development plan. The cathode was operated with an anode that simulates the HERMeS hall thruster operating environment. Cathode discharge performance has been stable with the device accumulating 740 hours at the time of this report. Cathode operation (i.e. discharge voltage and orifice temperature) was repeatable during period variation of discharge current and flow rate. The details of the cathode assembly operation during the wear-test will be presented.

Electron guns for RF sources typically use barium dispenser cathodes to produce electron emission. Barium and oxygen diffuse to the emission surface whenever the cathode is hot to replace that lost by evaporation. The barium combines with the oxygen to form barium oxide, which reduces the surface work function. Barium that evaporates from the surface is deposited on nearby surfaces, including grids and high voltage electrodes. If the barium recombines with oxygen, it can result in spurious electron emission and arcing from these surfaces. This research is investigating surface coatings to suppress spurious electron emission from these surfaces by preventing barium oxide formation.

The vigorous industrialization of the modern world and the incorporation of new consumption habits of society made appears electronic waste. This work had as objective to collect and characterize vitreous residues originating from Cathode Ray Tubes or, popularly, "image tubes", identified for the acronym CRT, which integrate computers monitors that will be recycled in the production of handicrafts. For its characterization were used techniques: X-Ray Fluorescence, Granulometric Analysis, X-Ray Diffraction. After analyses it was observed that glasses of the screen and of the funnel presented different chemical compositions, being silicium oxide (SiO2) the component of larger percentage in these glasses, 59.89% and 48.63%, for screen and funnel, respectively. Funnel presented 29.47% of lead oxide (PbO) while this oxide is absent in the screen. Screen presents significant amounts of barium oxide (10.75%) and strontium oxide (7.71%). Vitreous samples X-ray diffractions of residues of the funnel and the screen are to each other similar, presenting an amorphous band that indicates silica presence, with absence of crystalline phases. Through the presented results can be concluded that computer monitors CRTs has potential for be recycled, because present great amounts of SiO2, oxide that forms the vitreous net.

P2O5 is a common nucleating agent in glass-ceramics. To avoid the negative effect of P2O5 on sealing glass properties, we combined it with Barium oxide in the glass formulation. The effect of Ba3(PO4)2 incorporation on thermo-physical, structural and sealing characteristics of a glass of composition (mol%) 30SiO2–20SrO–30BaO–10B2O3–5La2O3–5Al2O3 is reported. The glass transition temperature decreases from 650 °C to 584 °C when Ba3(PO4)2 is increased from 0 to 2 mol%. Thermal expansion coefficient of the glass samples are found around 11.4 to 12.0 × 10−6 °C−1, which is close to that of Crofer-22 APU. 29Si MAS-NMR measurements indicate that glass network is composed of mainly Q2 units, while 31P forms Q0 units. XRD shows the formation of Ba2SiO4, Sr2SiO4 and BaAl2Si2O8 crystalline phases. There is no further evolution of crystalline phases when heat treated at 800 °C for 500 h. Seals with Crofer-22 plates have been made and interface reveals good bonding. The glass composition formulated by addition of 1 mol% Ba3(PO4)2 has shown good thermal and sealing characteristics, while further increase of Ba3(PO4)2 to 2 mol% leads to increased crystallization tendency.

The clinker composition and performance of alite-rich Portland cement with different contents of barium oxide and calcium barium sulfoaluminate (abbr. C2·75B1·25A3S¯) were investigated by orthogonal testing. The results show that alite and C2·75B1·25A3S¯ mineral can coexist in a clinker system. The addition of barium oxide is of benefit to increase the content of C2·75B1·25A3S¯, and it can also activate the belite and promote the formation of alite at low temperature. The optimal silica modulus, iron modulus, lime saturation factor and content of C2·75B1·25A3S¯ are 2·3, 1·4, 0·94 and 4% respectively, and the proper content of barium oxide is 1·8%(by weight). The compressive strength of this cement prepared under these conditions reaches 52·3, 78·4 and 106·5 MPa at 3-day, 7-day and 28-day curing ages, which shows excellent performance of mechanical strength. The compositions, structures and performances of the clinker were analysed by means of X-ray diffraction, scanning electron microscopy–energy dispersive spectroscopy and metallographic microscope.

article We report the results of a systematic study of the thermal and optical properties of a new family of tellurite glasses, TeO2-ZnO-BaO (TZBa), as a function of the barium oxide mole fraction and compare them with those of TeO2-ZnO-Na2O (TZN). The characteristic temperatures of this new glass family (glass transition, Tg, crystallization, Tx, and melting, Tm) increase significantly with BaO content and the glasses are more thermally stable (greater ΔT=Tx −Tg) than TZN glasses. Relative to these, Raman gain coefficient of the TZBa glasses also increases by approximately 40% as well as the Raman shift from ~680 cm −1 to ~770 cm −1 . The latter shift is

The influence of barium oxide, heat treatment time and temperature on the crystallization, microstructure and mechanical behavior of the system Bax·K1−2x·Mg3·Al·Si3O10·F2 (where x = 0.0, 0.3 and 0.5) was investigated in order to develop novel, high strength and machinable glass–ceramics. Three glasses were prepared and characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscope (SEM) techniques and some mechanical testing methods. The crystallization kinetics of glass–ceramics was also studied. Activation energy and Avrami exponent calculated for the crystallization peak temperature (Tp) of three different glass batches. The Vickers hardness decreased slightly on formation of the potassium fluorophlogopite and barium fluorophlogopite phases, but decreased significantly on formation of an interconnected ‘house of cards’ microstructure.

Barium was deposited at room temperature on a thermal silicon oxide layer and the interfacial reaction was monitored by synchrotron induced photoemission (both core level and valence band). The first step of the growth consists of an interfacial reaction which leads to the formation of an interfacial silicate layer. The next step consists in formation of barium oxide while metallic barium occurs subsequently. The deposit can be also homogenized by annealing above 575 K. This results in the formation of several layers of silicate by consumption of silicon oxide. In the case of fractional coverage, subsequent annealing at 975 K induces the decomposition of barium silicate. However, such a decomposition process is strongly dependent on the initial film thickness. It can be avoided for deposits thicker than 3 eqML.

The current work is reported on employing alkaline-earth oxide additives - i.e., barium oxide (BaO), calcium oxide (CaO), or magnesium oxide (MgO) - to the manganese dioxide (MnO2) cathode in an environmentally safe aqueous rechargeable battery. The influence of these additives on the electrochemical behavior of the MnO2 cathode in a Zn-MnO2 battery using lithium hydroxide (LiOH) as an electrolyte is investigated. These additives enhanced the discharge performance of the Zn-MnO2 battery and its rechargeability. Herein, the MnO2 was physically mixed with at least one of the alkaline-earth oxides (such as BaO, CaO, or MgO) in different proportions of 1, 2, and 5 wt% during the electrode preparation. The incorporation of BaO or MgO additives into MnO2 was found to result in significantly higher discharge capacity and longer cycle life, compared with the battery using CaO additive or additive-free MnO2. The role of these additives in the MnO2 cathode is found not to suppress the formation of nonrechargeable products, but rather to reduce the access of Zn ions to the MnO2; without these additives, a ZnO·Mn 2O3 product may form at the cathode.

Materials containing barium (Ba), such as SmBa 0.5 Sr 0.5 Co 2 O 5-d /Ce 0.9 Gd 0.1 O 1.9 (SBSC50) and Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-d (BSCF), are considered for use as an in-situ cathode in metal-supported solid oxide fuel cells (SOFCs). The electrochemical properties and sintering behavior of these materials are investigated in terms of area specific resistances (ASRs), I-V-P characteristics and microstructure. The properties of in-situ cathodes comprised of SBSC50 and BSCF are compared with those of conventional cathodes, such as La 0.8 Sr 0.2 MnO 3-d (LSM), La 0.8 Sr 0.2 FeO 3-d (LSF), La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-d (LSCF) and Sm 0.5 Sr 0.5 CoO 3-d /Ce 0.8 Sm 0.2 O 1.9 (SSC40). Impedance spectroscopy analysis using Nyquist and Bode plots and microstructure analysis is conducted to understand the reason behind electrochemical performance differences between in-situ cathodes and sintered cathodes. From this analysis, we are also able to verify the electrochemical behavior of well-defined in-situ cathodes. SBSC50 and BSCF are the incorporated in our metal-supported cells without the use of any additional sintering process. The metal-supported cells are successfully fabricated using a high temperature sinter-joining process and we fail to detect any defects or deformation after fabrication. At an operating temperature of 800 °C, metal-supported cells with SBSC50 and BSCF cathodes exhibit maximum power densities of 0.50 Wcm -2 and 0.65 Wcm -2 , respectively.

Combined analysis employing in-situ X-rays photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and ex-situ X-ray diffraction (XRD) has demonstrated the feasibility to deposit single-phase barium oxide overlayers by a direct sublimation of BaO material from an effusion cell. Furthermore, in situ scanning tunneling microscopy (STM) has confirmed that the BaO grows as nanoclusters with dimensions down to ~2 nm.

The study of two different methods to obtain strontium barium niobate nanocrystals immersed in a glass matrix has been carried out. Ho 2 O 3 -doped SrO–BaO–Nb 2 O 5 –B 2 O 3 glasses were fabricated using the melt quenching method. Glass ceramic samples were obtained from the precursor glass by thermal treatment in a furnace and by laser irradiation. These glass ceramic samples are formed by a glassy phase and a crystalline phase of strontium barium niobate nanocrystals. This structure was confirmed by X-ray diffraction and Atomic Force Microscope images. The incorporation of Ho 3+ ions in the strontium barium niobate nanocrystals were corroborated by optical measurements, which produced an increment in the luminescence intensity compared to the precursor glass.

The role of calcium oxide (CaO) was investigated in the crystallization of BaO–SrO–TiO 2 –SiO 2 glass. The CaO dopant altered the oriented growth facets of crystal unit cells in the glass–ceramics. The crystallites are acicular in micron scale in the samples having as small as 1% CaO dopant, but are long granular in the nanometer scale in the sample without CaO. The glass–ceramics which have nano crystallites are observed with a less crystallization density qualitatively, a higher transmissivity in the wavelength range of 200–2600 nm, and 30% lower piezoelectric coefficient, d 33 , at 9.5 ± 0.3 pC/N than those glass–ceramics having CaO in the study.

Phase relations have been studied in the BaO–CuO x system in the range of 42.0–83.0 mol.% CuO at P(O 2 ) = 21 kPa (air) by visual polythermal analysis (VPA), powder X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TGA), chemical analysis (CA), and electron diffraction (ED) with simultaneous elemental analysis (EA) in a transmission electron microscope (TEM). The existence of discrete crystallization fields of barium–copper oxides of cation compositions Ba 4 Cu 5 O y , Ba 5 Cu 6 O y , Ba 7 Cu 8 O y , Ba 12 Cu 13 O y , and Ba 24 Cu 25 O y , which have the cubic structure of the BaCuO 2 oxide, is revealed in the studied region of the system. The oxides may be represented as members of a Ba m Cu m + n O y homologous series. The BaCuO 2 oxide does not exist in the subsolidus region and does not have its own crystallization field. The oxygen-deficient oxide BaCuO 1.78 of the cation composition (Ba:Cu) 1:1 with the BaCuO 2 cubic structure is found in melted samples of the 50.0 mol.% CuO composition quenched at 1020–1060 °С.

The possibility of refining metallurgical grade silicon to a high-purity product for solar cell applications by the slagging of impurity elements was investigated. Distribution coefficients were determined for B, Ca, Mg, Fe, K and P between magnesia or alumina saturated Al2O3–CaO–MgO–SiO2 and Al2O3–BaO–SiO2 slags and silicon at 1500 °C. The partitioning of the impurity elements between molten silicon and slag was examined in terms of basicity and oxygen potential of the slag, with particular focus on the behaviour of boron and phosphorus. The experimental results showed that both of these aspects of slag chemistry have a significant influence on the distribution coefficient of B and P. Increasing the oxygen potential by additions of silica was found to increase the distribution coefficients for both B and P. Increasing the basicity of the slag was not always effective in achieving high removal of these elements from silicon as excess amounts of basic oxides lower the activity of silica and consequently the oxygen potential. The extent of this effect is such that increasing basicity can lead to a decrease in distribution coefficient. Increasing lime in the slag increased distribution coefficients for B and P, but this counterbalancing effect was such that distributions were the lowest in barium-containing slags, despite barium oxide being the most basic of the fluxes used in this study. The highest removal efficiencies achieved were of the order of 80% and 90% for B and P, respectively. It was demonstrated that for the removal of B and P from metallurgical-grade silicon to solar-grade levels, a slag mass about 5 times the mass of silicon would be required.

The magnetic barium ferrite (BaFe12O19) hollow fibers with a high specific surface area about 22–38 m2 g−1, diameters around 1 μm and a ratio of the hollow diameter to the fiber diameter estimated about 1/2–2/3 have been prepared by the gel-precursor transformation process. The precursor and resulting ferrite hollow fibers were analyzed by thermo-gravimetric and differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy and X-ray diffraction. The specific surface area was measured by the Brunauer–Emmett–Teller method. The gel formed at pH 5.5 has a good spinnability. A pure barium ferrite phase is formed after calcined at 750 °C for 2 h and fabricated of nanograins about 38 nm with a hexagonal plate-like morphology, which are increased to about 72 nm with the calcination temperature increased up to 1050 °C. The barium ferrite hollow fibers obtained at 750 °C for 2 h have a specific surface area 38.1 m2 g−1 and average pore size 6.5 nm and then the specific surface area and average pore size show a reduction tendency with the calcination temperature increasing from 750 to 1050 °C owing to the particle growth and fiber densification. These barium ferrite hollow fibers exhibit typical hard-magnetic materials characteristics and the formation mechanism for hollow structures is discussed.

Current-voltage characteristics of planar junctions formed by an epitaxial c-axis oriented YBa2Cu3O7-x thin film micro-bridge and Ag counter-electrode were measured in the temperature range from 4.2 K to 300 K. A hysteretic behavior related to switching of the junction resistance from a high-resistive to a low-resistive state and vice-versa was observed and analyzed in terms of the maximal current bias and temperature dependence. The same effects were observed on a sub-micrometer scale YBa2Cu3O7-x thin film - PtIr point contact junctions using Scanning Tunneling Microscope. These phenomena are discussed within a diffusion model, describing an oxygen vacancy drift in YBa2Cu3O7-x films in the nano-scale vicinity of the junction interface under applied electrical fields., Comment: To be published in Applied Surface Science.

Double-perovskite oxides, LnBaCo2O5+x (LnBCO) (Ln = Pr, Nd, Sm, and Gd), are prepared using a solid-state reaction as cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The performances of LnBCO–Ce0.8Sm0.2O1.9 (SDC) composite cathodes were investigated for IT-SOFCs on La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolyte. The thermal expansion coefficient can be effectively reduced in the case of the composite cathodes. No chemical reactions between LnBCO cathodes and SDC electrolyte, and LnBCO and LSGM are found. The electrochemical performances of LnBCO cathodes and LnBCO–SDC composite cathodes decrease with decreasing Ln3+ ionic radii, which is closely related to the decrease of the electrical conductivity and fast oxygen diffusion property. The area specific resistances of the LnBCO cathodes and LnBCO–SDC composite cathodes on LSGM electrolyte are all lower than 0.13 Ω cm2 and 0.15 Ω cm2 at 700 °C, respectively. The maximum power densities of single-cell consisted of LnBCO–SDC composite cathodes, LSGM electrolyte, and Ni–SDC anode achieve 758–608 mW cm−2 at 800 °C with the change from Ln = Pr to Gd, respectively. These results indicate that LnBCO–SDC composite oxides are candidates as a promising cathode material for IT-SOFCs.

Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ (BSCF) and gadolinia-doped ceria (GDC) were synthesized via a glycine-nitrate process (GNP). A cubic perovskite of BSCF was observed by X-ray diffraction (XRD) at a calcination temperature above 950 °C. An anode-supported solid-oxide fuel cell was constructed from the porous NiO + YSZ as the anode substrate, the yittria-stabilized zirconia (YSZ) as the electrolyte, and the porous BSCF-GDC layer as the cathode with a GDC barrier layer. For the performance test, the maximum power density was 191.3 mW cm −2 at a temperature of 750 °C with H 2 fuel and air at flow rates of 335 and 670 sccm, respectively. According to the AC-impedance data, the charge-transfer resistances of the electrodes were 0.10 and 1.59 Ω cm 2 , and the oxygen-reduction and oxygen-ion diffusion resistances were 0.69 and 0.98 Ω cm 2 at 750 and 600 °C, respectively. SEM microstructural characterization indicated that the fuel cell as fabricated exhibited good compatibility between cathode and electrolyte layers.

In this paper, the results of a barium oxide depletion model are compared with some experimental results. The model is used to simulate the T5 and T6 cathodes and the NSTAR discharge cathode. A comparison with the experimental data is performed. For the T5 and T6 cathodes, good qualitative agreement is found, but for theNSTAR cathode, the agreement is not as good. In both cases, the agreement is improved when the boundary conditions are modified to better reflect the experimental conditions. The model presented is the first three-dimensional axisymmetric insert model that includes the dependency of BaO depletion from both the impregnant chemistry and the diffusive motion inside the insert.