BaO Content Research Articles

Geochemistry of granitic aplite-pegmatite dykes and sills and their minerals from the Gravanho-Gouveia area in Central Portugal

Two distinct series of Variscan granitic rocks have been distinguished in the Gravanho-Gouveia area of Portugal, based on field work, variation diagrams for major and trace elements, rare earth patterns and δ18O versus total FeO diagram of rocks, anorthite content of plagioclase, BaO and P2O5 contents of feldspars and AlVI versus Fe2+ diagram for magmatic muscovite. One series consists of a late-orogenic porphyritic biotite > muscovite granite (G1), less evolved beryl-columbite pegmatites and more evolved beryl-columbite pegmatites showing gradational contacts. The other series consists of post-orogenic porphyritic muscovite > biotite granodiorite to granite (G2), slightly porphyritic muscovite > biotite granite (G3) and lepidolite pegmatites. In each series, pegmatites are derived from the parent granite magma by fractional crystallization of quartz, plagioclase, K-feldspar, biotite and ilmenite. Some metasomatic effects occur like muscovite replacing feldspars, chlorite in pegmatites of the first series and a late muscovite in pegmatites of the second series, probably due to hydrothermal fluids. The lepidolite pegmatites contain cassiterite and two generations of rutile. The first magmatic generation consists of homogeneous crystals and the second generation occurs as heterogeneous zoned crystals derived from hydrothermal fluids. The beryl-columbite pegmatites and lepidolite pegmatites also contain the first magmatic generation and the late hydrothermal generation of zoned columbite-group minerals. More evolved beryl-columbite pegmatites were converted into episyenite by intense hydrothermal alteration and regional circulation of fluids in the granitic rocks.

Ionic conductivity behavior by activated hopping conductivity (AHC) of barium aluminoborosilicate glass–ceramic system designed for SOFC sealing

Non-conducting BaO-B2O3-Al2O3-SiO2 parent glasses designed for solid oxide fuel cell (SOFC) sealing applications were prepared using the melt-quenching technique. The glass formation region was determined according to phase equilibrium relations and was found to be in the composition range 70BaO-(x)Al2O3-(10−x)B2O3-20SiO2 where 3.0 < x < 6.0 wt%. The conductivity values obtained conductivity ranged from 10−5 to 10−10 S/cm at temperatures between 600 and 850 °C. The batch compositions presented a threshold of dc conductivity near 70BaO wt% with a quasi linear behavior with the decrease of the BaO content. Different values of conduction activation energy were observed at temperatures above the glass transition temperature (Tg) (up to 700 °C), which were attributed to the thermal bond-breaking of non-bridging oxygen (NBO) defects. The experimental results of the electrochemical characterization by impedance spectroscopy of glass–ceramic interfaces with yttria-stabilized zirconia (YSZ) acting as solid ionic conductor electrolyte are presented and discussed.

Mixed alkali/alkaline earth‐silicate glasses: Physical properties and structure by vibrational spectroscopy

AbstractIn this article, we investigate the correlation of selected physical properties with structural changes in quaternary mixed modifier alkali/alkaline earth oxide silicate glass systems, focusing either on the mixed alkali effect [(20−x)Na2O–xK2O–10CaO–70SiO2 (x = 0, 5, 10, 15, 20)] or on the mixed alkaline earth effect [20Na2O–(10−y)CaO–yBaO–70SiO2 (y = 0, 5, 10)]. A maximum microhardness and packing density, as well as a minimum glass transition temperature were observed for mixed alkali glasses. The mixed alkaline earth glasses do not exhibit any clear extrema in any of the properties studied. The hardness and glass transition temperature decreases, while the density and molar volume increases with increasing BaO content. Raman spectroscopy showed an increase in the Q3 group compared to the Q2 and Q4 groups as the high field strength ions Na+ or Ca2+ are substituted by their low field strength analogs K+ or Ba2+. In the mixed alkali series, the high field strength ion Na+, seems to push the low field strength ion K+ into lower energy sites when present simultaneously, while such an effect is not apparent for the mixed alkaline earth glasses, where the far IR spectra of mixed glasses are equivalent to the weighted averages of the pure glasses.

The effect of barium content on the crystallization and microhardness of barium fluormica glass-ceramics

Mica glass-ceramics are easily machined due to their “House-of-Cards” microstructure. Barium fluormica glass-ceramics were developed and indicated good mechanical properties. This work studies the effect of varying barium content on the crystallization and microhardness of mica glass-ceramics. Four glasses were produced with different baria contents, then converted to mica glass-ceramics using a two-step heat treatment. They were characterized using Differential Scanning Calorimetry [DSC], X-ray Diffraction [XRD], Scanning electron microscopy [SEM] and Vickers microhardness. DSC showed some formulations indicated bulk crystallisation as the dominant mechanism. XRD showed the crystallization of Barium fluorphlogopite in all the compositions with minor secondary phases. SEM showed the formation of “House-of-Cards” microstructures and with an increase in BaO content, a decrease in contrast was observed in back scattered mode. Exceptionally low hardness values (<2 GPa) were obtained for longer heat treatments/holding times and are related to the well-developed house-of-cards microstructures formed.

Beneficiation of Barite Ore from Azara in Nassarawa State, Nigeria, using froth flotation

Barite ore from Azara in Nassarawa State has been beneficiated using Jigging and Froth Flotation techniques by varying the pH of the solution. The chemical analysis indicates the presence of major elements Ba, S, O and minor elements like Ti, V, Al and Si which confirms that it is barite while the particle size analysis showed that the average particle size is ≈ 150 μm with a 1,167 cm 2 /g specific surface area. The X-ray diffraction analysis of both the as-mined ore and beneficiated samples indicate increased intensity in the later. The jigging result shows that 51% of the feed is the underflow while 46.7% is the overflow. The measured specific gravity as a function of pH show that values between 3.78 and 4.23 are obtained. The elemental composition of the Barite after beneficiation shows that in addition to high contents of BaO and SO 3 , the amount of SiO 2 present is still very high. The sample with a pH value of 7 gave the highest specific-gravity value of 4.23 while that with pH of 3 gave the lowest specific-gravity value of 3.78. The implication is that the barite sample with pH of 7 is acceptable for oil and gas applications while more work is needed for samples with other pH values. Keywords: Barite ore, Froth flotation, Specific gravity, Beneficiation, pH, Jigging

Effects of synthesis temperature on the microstructures and photoluminescent properties of Eu2O3-doped Sr2−xBaxSiO4 phosphors

In this study, Sr2−xBaxSiO4 (x = 0, 0.2, and 0.4) was used as the host material and Eu2O3 was used as the activator to produce commercial Sr2SiO4:Eu, Sr1.8Ba0.2SiO4:Eu, and Sr1.6Ba0.4SiO4:Eu phosphors by a solid-state reaction method. All the Sr2−xBaxSiO4–Eu phosphors were synthesized in the temperature range of 1000–1300 °C for 2 h. XRD patterns revealed that when different BaO contents and synthesis temperatures were used, all the Sr2−xBaxSiO4–Eu phosphors had similarly crystalline properties. The mainly crystalline phase changed from the (121) to the (103) plane as the BaO content changed from 0 to 0.2. In the case of all Sr2−xBaxSiO4–Eu powders, secondary or unknown phases were not observed if the synthesis temperature was lower than 1000 °C, and only the precursor SiO2 phase was observed in the 1000 °C-synthesized Sr2SiO4–Eu powder. This study also thoroughly investigated the effects of different BaO contents and synthesis temperatures on the photoluminescent properties of Sr2−xBaxSiO4–Eu phosphors. We show that the photoluminescent properties of Sr2−xBaxSiO4–Eu phosphors are dependent on the BaO content and synthesis temperature.

Removal of boron from metallurgical grade silicon by CaO-SiO2 based slags

Slag refining is one of the most effective methods to remove boron from metallurgical grade silicon (MG-Si). In this paper, the removal of boron from metallurgical grade silicon was proposed by adding CaF2, BaO or rare earth oxides (La2O3 and CeO2) to CaO-SiO2 based slags. The effects of the BaO content, the CaF2 content, the rare earth oxides content, the molar ratio of CaO to SiO2 and the mass ratio of slag to silicon on the partition coefficient of boron (LB) between slag and silicon are investigated. The results show that LB has a maximum value of 5.17 in 45% CaO-45% SiO2-10% BaO slags at 1550 °C after reacting for 6 h with a slag to silicon mass ratio of 2. Besides, it is found that the addition of La2O3 or CeO2 shows better de-boronization ability compared with the addition of BaO.

Sulphide capacity of CaO-SiO2-8%MgO-Al2O3-BaO slags ranging from 0% to 5% in BaO

The sulphide capacities of CaO-SiO2-MgO-Al2O3-BaO slags were measured at 1773 K and 1823 K using the gas-slag equilibration method to estimate the desulphurization ability of the blast furnace slags that contained barium. The effects of basicity, the Al2O3 and BaO content of slags on the sulphide capacity of slags were studied. The relationship between the sulphide capacity and the optical basicity of the slags was also investigated. The experimentally determined results were compared with the sulphide capacities estimated by some previously reported models. The results showed that the sulphide capacity increased significantly when the basicity (CaO/SiO2) increased from 1.0 to 1.2, but decreased when the Al2O3 content increased in the slag. The increasing BaO content increased the sulphide capacity. The desulphurizing ability decreased when the BaO content was more than 3.5%. There was a linearly increasing relationship between the optical basicity and the sulphide capacity. The experimentally determined sulphide capacities were closest to the predicted values obtained by the Sosinsky and Sommerville’s model.

Gamma-ray shielding properties for silicate glasses containing Bi2O3, PbO, and BaO

Introduction: With the extensive application of radiation sources and radioactive materials in various fields, the study of attenuation and absorption of X-rays and gamma-rays in several materials has become an essential and interesting field of research. Glass materials are possible alternatives of concretes for radiation-shielding materials. Materials and Methods: The mass attenuation coefficients (µm), effective atomic cross section (σa), effective atomic number (Zeff) and effective electron density (Neff) of silicate glasses containing different concentrations of Bi2O3, PbO, and BaO (30–70% by weight) were obtained using MCNP-4C code, XCOM and XMuDat programs, in the energy range of 10 keV–10 MeV. The interpolation method was employed to extract Zeff and Neff. The Auto-Zeff software was used to determine the Zeff as well. Results: The MCNP-4C Code, XCOM and XMuDat programs and Auto-Zeff results were in good agreement. It was found that the µm and σa values decrease with photon energy. Also the results indicate that σa and Zeff of glasses improve by increasing their Bi2O3, PbO and BaO contents, while increasing these contents to the same fraction has no significant effect on µm in the energy range of 0.3–5 MeV, where the Compton Effect takes over as dominant process and Neff do not follow certain rule. Above 0.1 MeV, lead oxide silicate glass showed the highest values of Zeff and σa. Conclusion: Observed good agreement indicates that the chosen Monte Carlo code and computer programs may be useful to calculate the gamma-ray shielding characteristics of different glass systems, particularly in cases where no experimental data exist.

Effect of BaO on the phase composition and properties of aluminates for Ba-W cathodes

In this study, we prepared (4.8+x)BaO·CaO·2Al2O3 (0 ≤ x ≤ 1.6) aluminates by calcining the precursors under static air at 1500 °C for 120 min. The precursor powders were prepared using a liquid phase co-precipitation method. The effects of the molar content of BaO on the phase composition (before and after melting), melting properties, environmental stability, evaporation, and emission properties of the aluminates was investigated systematically The results showed that the phase of the aluminates completely transformed from Ba5CaAl4O12 to Ba3CaAl2O7 with an increase in the BaO content. After melting, the phase changed from Ba5CaAl4O12 to a mixed phase of Ba5CaAl4O12 and Ba3CaAl2O7. In the high-temperature molten state, the aluminates were in the ionic state, which generated a relatively low-energy Ba5CaAl4O12 phase during cooling crystallization. With every 0.4 mol increase in the BaO content, the initial melting temperature of the aluminates decreased by 10–20 °C, while the environmental stability deteriorated gradually. When the aluminates reacted with H2O and CO2 in the air, the original phase still existed and the characteristic peaks gradually broadened, but with the formation of Ca(OH)2, CaCO3, and BaCO3. At 1050 °C, with an increase in the BaO content, the evaporation rate of the Ba-W cathodes increased and the emission current density first increased and then decreased. The main components of the Ba-W cathode evaporation were Ba and BaO. At n(BaO):n(CaO):n(Al2O3) = 6:1:2, the Ba-W cathode showed the best emission performance, and its pulse emission current density at 1050 °C was as high as 35.31 A/cm2.

Thermo-optical and structural properties of barium aluminoborate glasses

In this work, we have prepared 22 barium aluminoborate glass compositions and investigated their thermo-optical and structural properties. The non-hygroscopic glass composition (71−x) B2O3:(20+x) BaO:9 Al2O3 with x = 0, 5, 10, 15, and 20 (%mol) presented high transparency in the visible to near-infrared region of about 80%. X-ray diffraction patterns have shown no crystalline phase and indicated a structural change feature. As BaO content increases from 20 to 40 mol%, the density increased from 2.82 to 3.696 g/cm3 whereas Vickers hardness decrease from HV = 5.3 to 4.2 GPa. The FTIR curves indicate three main regions concerning BOB, BO4, and BO3 units. Refractive index measured at 546 nm varied from 1.5611 to 1.6371, whereas dn/dT remained almost constant i.e. 1.69×10−5°C−1. Thermal Diffusivity obtained by thermal lens technique indicated a decreased from 3.4 to 2.8 cm2×10−3/s as BaO is added to the glass compositions. The results indicate that non-bridging oxygen plays an important effect on glass physical properties.

Investigating the migration of pollutants at Barreiro area, Minas Gerais State, Brazil, by the 210Pb chronological method

Barreiro area at Araxá city, Minas Gerais State, Brazil, has been subjected to intense debate because of environmental pollution related to intense mining activities developed for the phosphate and niobium exploitation. Anthropogenic inputs involving the barium release into waters occurred there by the early 1980s because of a leakage occurring at one tailings dam as the adoption of synthetic membrane for the dam waterproofing only started in 2006. This paper reports a novel (radio)chemical record obtained from the analysis of samples of waters and a 35-cm depth sediment core with the aim of focusing the major pathways for the constituents transport there, which are accompanied by information on possible modifications along the time as provided by the use of the 210Pb chronological method. All waters are reducing, despite the rainwater is acid and the remaining (surface water and groundwater) are alkaline. Calcium dominates the rainwater composition, whereas Si is a relevant constituent in the surface and groundwater samples. The sediments are classified as silty sand and sand, Fe2O3 is the major oxide of all sediments sections, reaching a mean concentration value of 47% and it is followed by Organic Matter > BaO > SiO2 > P2O5 > Al2O3 > TiO2 > SO3 > CaO > Nb2O5 whose mean concentration is between 2 and 15%. The Ba levels in waters and sediments from Barreiro area are high, unlike in other streams draining the Araxá municipality. Chloride exhibited a high mobility index, confirming its conservative behavior in solution, whereas the quite low value for iron corroborates that Fe oxides/hydroxides are highly sorptive materials. The CRS 210Pb chronological model allowed identify BaO, Nb2O5, SO3, ThO2 and REEs (La, Ce) concentration peaks around 1973, agreeing with the significant correlations found among these parameters.

Effect of BaO on the calcination and hydration characteristic of CA

Phosphoaluminate cement (PAC) clinker had good mechanical properties at early and long-term period. In comparison, the compressive strength of PAC clinker modified by BaO was more prominent. As primary mineral phase for PAC clinker, CA’s mineralogical structure and hydration characteristics were intimately related to the compressive strength of hardened cement paste. In this study, the effects of BaO content on the calcination, mineralogical structure and hydration characteristics of CA were investigated. Experimental results showed that the appropriate calcination temperature of CA was 1400 °C. No more than 11% (the substitution ratio of BaO for CaO) addition of BaO can promote the conversion of C12A7 to CA and increase the formation ratio of CA. Appropriate content of 7 mol% BaO could endow the hardened paste with excellent compressive strength. In CA mineral phase the high limit addition of BaO was 15 mol%. The addition of BaO decreased and even restrained the formation of C2AH8 and C3AH6 of CA hydration products and also improved the content of CAH10. The addition of BaO dramatically decreased the hydration velocity and cumulative heat of CA mineral.

Radiation shielding parameters of BaO–Nb2O5–P2O5 glass system using MCNP5 code and XCOM software

The radiation shielding properties (mass attenuation coefficient, effective atomic number, half value layer, mean free path and exposure buildup factor) of xBaO–20Nb2O5–(80−x)P2O5, (x = 20, 30, 40, 50 and 60 mol%) glass system has been evaluated. The mass attenuation coefficient was calculated at 31, 59.5, 80, 356 and 662 keV photon energies using XCOM program and MCNP5 code. The obtained results are found to be in good agreement. The values of mass attenuation coefficient and effective atomic number of the present glass system are found to be increasing with increasing the BaO content at all energies. The mean free paths of the present samples are found to be smaller than the mean free path of some standard shielding glasses and concretes. This establishes that the present glasses possess better radiation shielding competence. The effect of the penetration depth on exposure buildup factor has also been discussed to through more light on their gamma ray interaction behaviour. The 60BaO–20Nb2O5–20P2O5 sample was found to be the best gamma shield.

Improvement of Electron Field Emission from Carbon Nanotubes by Ba(NO3)2 Treatment

The method of manufacturing BaO thin layers on carbon nanotubes (CNT) from Ba(NO3)2 aqueous solutions was demonstrated. Ordered carbon nanotubes arrays were synthesized by catalytic plasma-stimulated chemical deposition from the gas phase. The influence of the BaO content on the work function and, accordingly, carbon nanotubes emission properties were investigated. Significant field emission threshold voltage of CNT arrays treated by solutions with the lowest Ba(NO3)2 concentrations was demonstrated.

Physical, Optical and FT-IR studies of Bismuth-Boro-tellurite Glasses containing BaO as modifier

The addition of glass modifier changes the properties of host glass network. The role of Ba2+ as glass modifier has been investigated using physical, UV-Visible and FT-IR studies on xBaO-(30-x)TeO2-35Bi2O3 -35B2O3 ( where x = 5,10,15,20 and 25 mole% ) glasses. X-ray diffractograms of crushed glass samples were recorded at room temperature. The absence of sharp peaks in X-ray diffractograms confirms the amorphous nature of the glass samples. Density (ρ) of glass samples were estimated using Archimedes principle. Physical properties such as molar volume (VM), oxygen packing density (OPD), optical basicity etc. were determined. The optical absorption spectra were recorded in the wave length range of 200–1000 nm at room temperature. From the optical absorption spectra indirect allowed optical band gap, Urbach energy, refractive index (n), dielectric constant (ɛ), reflection loss (R), molar refractivity (Rm) and metallization criteria values were evaluated. The refractive index values were decreasing while optical band gap values were increasing with increasing concentration of BaO. IR spectra were recorded in the spectral range 400 - 4000 cm–1.

Optical and structural properties of BCBS glass system with and without alumina

BaOCaOAl2O3SiO2 (BCAS) glass and their derivatives have gained extreme importance for their high endurance to elevated temperatures and being suitable for various electrochemical applications. Two glass systems, one being 50mol% [SiO2B2O3]-xBaO-(45-x)CaO5Al2O3 called as BCBSA and another without Al2O3 termed as BCBS were synthesized using melt quenching technique in the present work. Addition of ZnO and MgO as flux helped in melting them at 1300 °C which is much lower than the usual melting temperature of these glasses [1–4]. Density of the quenched glasses was measured by Archimedes method and structural bond vibrations were confirmed through FTIR. UV Visible spectroscopy was used to determine band gap energy and confirm the insulating nature of the synthesized glasses. The samples were isothermally heated at 700 °C, 800 °C for 50 h and at 900 °C for 50 and 100 h duration in air to allow the devitrification process to take place. The heat treated samples were analyzed by X-ray diffraction to identify the developed phases. Five Al2O3 free samples synthesized at 1300 °C by regular melt quenching technique were found to be devoid of the monocelsian phase. This is a detrimental phase for high temperature sealant applications as it has a very low coefficient of thermal expansion (CTE). Al2O3 free BCBS glasses, properties of which are being reported for the first time and glasses with low BaO concentrations are found to meet the requirements for high temperature applications as sealants in Solid Oxide Fuel Cell (SOFC).

Zn2+- Controlled Crystallization and Microstructure in K-Li-Mg-B-Si-Al-F Glass

Abstract Text:The crystallization of (9-X) K2O-1Li2O-12MgO-10B2O3-40SiO2-16Al2O3-12MgF2-X PbO/BaO/ZnO (X =0/5) composition (wt.%) were studied by means of dilatometry, DSC, XRD, SEM and microhardness analysis. Density of base K-Li-Mg-B-Si-Al-F glass (2.59 g.cm–3) is found to be increased on addition of the network modifier oxides PbO, BaO and ZnO content. Addition of Pb2+, Ba2+ and Zn2+ furthermore increased the glass transition temperature (Tg.). A characteristic exothermic hump is found to be appeared in DSC thermograph at the temperature range 800-950°C; and that is ascribed to the formation of crystalline phase fluorophlogopite mica, KMg3(AlSi3O10)F2. Opaque glass-ceramics were prepared from K-Li-Mg-B-Si-Al-F glasses (with and without containing PbO, BaO and ZnO content) by controlled heat-treatment at 1000°C. Interlocked type microstructure combined of flake like fluorophlogopite mica crystals is obtained in ZnO-containing K-Li-Mg-B-Si-Al-F glass-ceramic; and such microstructural pattern is ascribed to cause large thermal-expansion (&gt;11.5×10-6/K, 50-800°C).Vickers Microhardness of base glass-ceramic (5.12 GPa) is increased when contains ZnO (5.26 GPa). ZnO-containing boroaluminosilicate glass-ceramic is, hence, considered with potential interest as they can exhibit the microcrack resistivity in high temperature recycling operation (like SOFC).

Comparative study of gamma-ray shielding and elastic properties of BaO–Bi2O3–B2O3 and ZnO–Bi2O3–B2O3 glass systems

A melt quenching method has been used to prepare xBaO-30Bi2O3-(70-x)B2O3 and xZnO-30Bi2O3-(70-x)B2O3 glasses, where 5 ≤ x ≤ 30 mol. %. The mass attenuation coefficients (MAC) for the prepared glasses have been calculated using MCNPX (version 2.6.0) Monte Carlo code in the energy range 0.122–1.33 MeV and the results have been compared with those obtained by XCOM program. From the obtained MAC, different shielding parameters such as effective atomic number (Zeff), half value layer (HVL) and mean free path (MFP) for the prepared glasses have been evaluated. The MAC and Zeff values are found to increase with an increase in the BaO (for BaO-Bi2O3-B2O3 glasses) and ZnO (for ZnO-Bi2O3-B2O3 glasses) concentrations. By the addition of BaO and ZnO, a remarkable difference in HVL between the BaO and ZnO glasses is noticed. Additionally, the elastic moduli results have been measured by sound velocity at 4 MHz and computed according to Makishima-Mackenzie model and Rocherulle model. The results observed that the 30BaO–30Bi2O3–40B2O3 glass system showed excellent nuclear radiation shielding and elastic properties. All the obtained results indicated that BaO-Bi2O3-B2O3 glass system has shielding properties that is better than ZnO-Bi2O3-B2O3 glass system.

Determining the gamma-ray parameters for BaO–ZnO–B2O3 glasses using MCNP5 code: a comparison study

ABSTRACTRapid technological advancement has multiplied people’s exposure to ionizing radiations greatly. Widespread applications of radiation in different fields (such as agriculture, radiation therapy and scientific research fields) require that humans be protected against unnecessary exposure. In this study, mass attenuation coefficient (μm), half-value layer, mean-free path, effective atomic number (Zeff) and exposure buildup factor have been calculated for xBaO–20ZnO–(80 − x)B2O3 (x = 5, 10, 15, 20 and 25 mol%) glass systems. The mass attenuation coefficients of the selected glasses were calculated using simulation method of MCNP5 code. The simulation results have been compared with the experimental data and Xcom at the energies 223.02, 252.98, 287.28, 340.83, 398.97, 481.59, 562.68 and 662.00 keV. The agreement amounts of the mass attenuation coefficient values are from 0.2% to 2.8% and from 0.2% to 6.98% for MCNP5 and Xcom relative to experimental results, while the Monte Carlo program values are higher than that obtained by experimental data, using Xcom and MCNP5 code. The glass sample having the highest value of BaO content show high radiation shielding properties. It indicates that the MCNP5 code can be used for estimation of radiation interaction parameters where experimental results are not available.