Addition Of BaO Research Articles

Optical properties of high density barium borate glass for gamma ray shielding applications

Study of optical and gamma rays shielding properties were performed in glassy system of xBaO–5MgO–8Na2O–(87 − x)B2O3, previously prepared by melt-quenching technique. The optical properties of the glass samples have been obtained using UV–Vis measurements. The WinXCom computer program (version 3.1) and Auto Zeff program (version 1.7) were used to calculate the mass attenuation coefficients and effective atomic numbers, respectively, of γ-photon energies from 1 keV up to 1 GeV. The results reflected that, an addition of BaO improves the studied properties of the glass samples; hence the reported glassy system can find applications in the areas of nuclear radiation-shielding.

Improvements in microstructural and mechanical properties of ZrO2 ceramics after addition of BaO

The effects of the addition of BaO on the sinterability, phase balance, microstructure, and mechanical properties of 8mol% yttria-stabilized cubic zirconia (8YSZ) were investigated using scanning electron microscopy, X-ray diffraction (XRD) analyses, and micro-hardness testing. The 8YSZ powder was doped with 0–15wt% BaO using a colloidal process. The undoped and BaO-doped 8YSZ specimens were sintered at 1550°C for 1h. The XRD analyses results showed that the specimens doped with up to 1wt% BaO did not exhibit BaO-related peaks, indicating that BaO was completely solubilized in the 8YSZ matrix. However, when more than 1wt% BaO was added, BaZrO3-related peaks appeared, suggesting that the overdoped BaO did not dissolve in the 8YSZ matrix but formed a secondary phase of BaZrO3 at high temperatures. Grain size measurements showed that the grain size of 8YSZ decreased with an increase in the amount of BaO added. The decrease in the grain size was owing to the fact that the grains of BaZrO3, which precipitated at the grain boundaries and grain junctions of 8YSZ, increased the grain boundary cohesive resistance because of the pinning effect. This resulted in a decrease in the grain boundary mobility, and an increase in the grain boundary energy. Furthermore, while the addition of BaO to 8YSZ caused a slight decrease in the hardness of 8YSZ, the fracture toughness of 8YSZ increased from 1.64MPam1/2 to 2.08MPam1/2, owing to the resulting decrease in the grain size.

Optical properties and weakening of elastic moduli with increasing glass transition temperature (T g) in (80–x)TeO2-xBaO-20ZnO glasses

Abstract BaO addition to ternary (80–x)TeO2-20ZnO-xBaO (x = 0–20 mol.%) glasses resulted in a decrease in ultrasonic velocities and independent elastic moduli; this result indicated that the rigidity of the glass network weakened possibly because non-bridging oxygen increased. Thermal analysis results showed that glass transition temperature increased as BaO content increased because of the stabilizing effect of Ba2+ on the glass network. Additional analyses using bulk compression and ring deformation models revealed that the ratio between theoretical bulk modulus and experimental bulk modulus increased; this result indicated that the compression mechanism mainly involved isotropic ring compression. Furthermore, the increase in non-bridging oxygen formation with BaO addition caused a decrease in optical energy gap and an increase in refractive index. An increase in Urbach energy indicated that the degree of disorder in the glass system also increased.

Effects of M2+ (M = Ca, Sr, and Ba) Addition on Crystallization and Microstructure of SiO2-MgO-Al2O3-B2O3-K2O-F Glass

In understanding the effect of K+ substitution by M2+ (M = Ca, Sr, and Ba) on crystallization and microstructural properties of boroaluminosilicate glass system, the SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glasses were prepared by single-step melt-quenching at 1500°C. Density of base glass (2.64 g·cm−3) is found to be decreased in presence of CaO and SrO. Tg is increased by 5–10°C and Td decreased by 13–20°C on addition of M2+. The variation of Tg, Td and decrease of thermal expansion (CTE) from 7.55 to 6.67–6.97 (×10−6/K, at 50–500°C) in substituting K+ by M2+ are attributed to the higher field-strength of Ca2+, Sr2+, and Ba2+. Opaque mica glass-ceramics were derived from the transparent boroaluminosilicate glasses by controlled heat treatment at 1050°C (duration = 4 h); and the predominant crystalline phase was identified as fluorophlogopite (KMg3AlSi3O10F2) by XRD and FTIR study. Glass-ceramic microstructure reveals that the platelike mica flake crystals predominate in presence of K2O and CaO but restructured to smaller droplet like spherical shaped mica on addition of SrO and BaO. Wide range of CTE values (9.54–13.38 × 10−6/K at 50–800°C) are obtained for such glass-ceramics. Having higher CTE value after crystallization, the CaO containing SiO2-MgO-Al2O3-B2O3-MgF2-K2O-Li2O-AlPO4 glass can be useful as SOFC sealing material.

Effect of BaO addition on the structure and microstructure of SiO2–Al2O3–Na2O–K2O–MgO glass–ceramic composites

We examined the influence of barium oxide addition on the structure and properties of SiO2–Al2O3–Na2O–K2O–MgO glass–ceramics. Glass–ceramics were prepared with constant SiO2/Al2O3 and Na2O/K2O ratios of 6.5 and 1.04, respectively, and the MgO content was maintained at 10.56wt%. The barium oxide content was set at 4wt%, 9wt%, and 14wt%. The weight ratios were recalculated from the BaCO3 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.

V2O5-P2O5-ZnO-Sb2O3 Glass Frit Materials with BaO and Al2O3 for Large-sized Dye-sensitized Solar Cell Sealing

V₂O 5 -P₂O 5 -ZnO-Sb₂O₃ glasses modified with BaO and Al₂O₃ are synthesized as a sealing material for large-scale dye-sensitized solar cells (DSSCs). A compositional study is performed in order to determine the glass that can be sintered below 500℃ with a high chemical stability against the electrolyte. The flow size of the glasses after the heat treatment and the glass stability are increased with the addition of Al₂O₃ and BaO, while the glass transition temperature is decreased. After the reaction with the electrolyte at 60℃ for 72 h, the addition of 5 mol% of BaO and 2 mol% of Al₂O₃ considerably enhances the chemical stability of the glass. X-ray diffraction (XRD) and scanning electron microscope (SEM) are used to examine the reaction between the electrolyte and glasses. The structural contribution of the additives is also investigated and discussed.

Energy storage properties in Ba0.4Sr0.6TiO3 ceramics with addition of semi-conductive BaO–B2O3–SiO2–Na2CO3–K2CO3 glass

Semi-conductive BaO–B2O3–SiO2–Na2CO3–K2CO3 glass additives were added to Ba0.4Sr0.6TiO3 (BST) ceramics to investigate its influences on the microstructure, dielectric properties, breakdown strength (BDS), and energy storage density. The sintering temperatures were lowered about 150°C with a high relative density (∼98%). X-ray diffraction patterns of all BST glass ceramics suggest perovskite structures without any detectable secondary phase. Room temperature dielectric constant of BST glass ceramics decreases with increasing Na2CO3 content. BDS and energy storage density of BST glass ceramics increase with increasing Na2CO3 content, and reach their maxima of 280kV/cm and 0.72J/cm3 at the highest Na+ and K+ content. These results suggest that the BST glass ceramics could find their potential applications in energy storage capacitor devices.

Features of the production of glasses for claddings of rigid multimode optical fiber

Glasses synthesized on the basis of the R2O-B2O3-SiO2 system, where R2O is Na2O or K2O, have been investigated for the reflective and protective claddings of optical fiber. Laws have been established to describe how the oxides affect the glass-forming capability of optical glasses and their tendency to crystallize in the temperature interval in which optical fiber is drawn and to describe their thermal and optical characteristics. Laws have also been established to describe how the composition and structural factors affect the rheological properties of glasses for the claddings of optical fibers. The optimum concentrations of Al2O3, BaO, and MgO additives have been determined so that their introduction into the composition of the glasses for the light-reflecting cladding ensures that the temperature interval in which the viscosity of the glasses varies from 109 to 104 Pa sec is at least 360°C. The glasses for the light-reflecting and protective claddings are matched with the glass of the light-conducting core with respect to viscosity indices.

Effect of BaO on catalytic performance of Pd-based catalysts for purification of gasoline-methanol exhaust

Barium oxide was developed successfully to modify palladium catalysts supported on CeO2-ZrO2-La2O3-Al2O3 (CZLA) compound oxides by impregnation method. N2 adsorption (BET), X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the influence of BaO on the physicochemical properties of catalyst. And catalytic activity tests for methanol, CO, C3H8 and NO conversion were evaluated. Catalytic activity results showed that BaO had a positive effect on the conversion of all pollutants. H2-TPR results suggested that the addition of BaO increased the reductive ability of the palladium catalysts. The XPS results indicated that doping BaO also improved the dispersion of Pd species and increased the amounts of Ce3+ on the Pd-Ba/CZLA catalyst surface, which led to a better redox property. The excellent redox property helped to improve the catalytic activities toward all the pollutants over Pd-based catalysts.

Effects of BaO–B2O3–SiO2 glass additive on dielectric properties of Ba(Co0.5Nb0.5)O3 ceramics

Ba(Co0.5Nb0.5)O3 (BCN) ceramics doped with BaO–B2O3–SiO2 (BBS) glass were prepared by the conventional solid-state ceramic route. The effects of glass content on the sintering temperature, phase composition, microstructure and dielectric properties of Ba(Co0.5Nb0.5)O3 ceramics were investigated. The sintering temperature of the BaO–B2O3–SiO2 glass added Ba(Co0.5Nb0.5)O3 ceramics decreased by 75–125°C than that of the pure Ba(Co0.5Nb0.5)O3. The addition of BaO–B2O3–SiO2 glass can improve the frequency stability of the dielectric properties of Ba(Co0.5Nb0.5)O3 and decrease dielectric loss. Ba(Co0.5Nb0.5)O3 ceramics with 0.5wt% BaO–B2O3–SiO2 glass additions show the best frequency stability and the lowest dielectric loss, and the dielectric constant is almost as same as the pure Ba(Co0.5Nb0.5)O3 ceramic. These improvements in the dielectric characteristics of Ba(Co0.5Nb0.5)O3 ceramics have great scientific significance for their applications.

Effects of baria on propane oxidation activity of Pd/Al2O3 catalyst: Pd–BaO interaction and reaction routes

The BaO-modified Pd/Al2O3 exhibits much better catalytic activity than Pd/Al2O3 for C3H8 oxidation both before and after the hydrothermal aging treatment. Further studies ascribe its good activity to the influence of BaO species on the physicochemical characteristics of the catalyst and the reaction routes. Firstly, the BaO species inhibits the phase transformation of alumina, resulting in higher surface area of the catalysts and hereby a better dispersion of Pd. Secondly, the basic nature and electron-withdrawing effect of barium oxide maintain palladium at high oxidation state, which leads to a higher PdO content on surface of the BaO-modified catalyst. Finally, the formation/decomposition of carbonate/bicarbonate species can be promoted by the addition of BaO, which provide extra reaction routes and are important for the deep oxidation of C3H8.

Influence of Ni Particle Size of SDC-Supported Anode on SOFC Performance

ABSTRACTBoth Ni and alkaline earth metal oxide (MO: CaO, SrO, and BaO)-impregnated SDC powders were prepared as an SOFC anode material. The averaged Ni particle size on SDC was affected by the kind of alkaline earth metal oxide added. The addition of SrO and BaO to Ni/SDC anode enhanced power densities of both H2-SOFC and CH4-SOFC and the addition of CaO lowered them. The maximum power density increased with decreasing the averaged Ni particle size of Ni-MO/SDC anode.

Influence on Static Grain Growth and Sinterability of BaO Addition into 8YSZ

In this study, 8 mol.% yttria stabilized cubic zirconia (8YSZ) powders as a matrix material and 0 15 wt% BaO powders as an additive were used in order to determine the e ect of BaO addition and amount on the microstructure, sintering and static grain growth properties of the 8YSZ. For these purposes, undoped and BaO-doped 8YSZ specimens were annealed for grain growth at 1400, 1500, and 1600 ◦C for 10, 50, and 100 h, respectively. An increase of annealing temperature and holding time resulted in grain growth in all specimens. The grain size of the 8YSZ decreased with the higher level of BaO added. A limited amount of BaO dissolved in 8YSZ, and insoluble BaO reacted with ZrO2 at high sintering temperature and generated the BaZrO3 second sphase compound. Energy dispersive X-ray spectroscopy results showed that the BaZrO3 second phase segregated at the surrounding grains and grain boundaries of the 8YSZ. These BaZrO3 second phases had a pinning e ect at the grain boundaries and prevented the migration of the grain boundaries of the 8YSZ. In conclusion, the grain growth results showed that the grain growth in the BaO-doped 8YSZ specimens was controlled by a solid solution drag mechanism.

Effect of acid and base modification on the catalytic activity of Pt/Al2O3 for propene oxidation

BaO and SO42− modified Pt/Al2O3 catalysts were prepared by a two-step wetness incipient method. The textural properties were characterized by BET, XRD, ex situ FTIR. Propene oxidation activity under various redox ratio (S=[O2]/4.5[C3H6]) was evaluated. The oxidation process and intermediate species were studied by detailed in situ FTIR experiments including propene adsorption CO IR and propene TPO. It is observed that the addition of BaO promotes the catalytic oxidation of propene over Pt/Al2O3, while sulfation results in the deactivation of Pt/Al2O3. The good activity of Pt/BaO/Al2O3 is ascribed to the weakened propene adsorption, the formation of reactive enolic species and easy oxidation of intermediate CO by active oxygen at Pt–Ba interface. On the contrary, the strong adsorption of propene as well as the intermediate CO poisoning are proved to be the main reasons for the deactivation of Pt/SO42−/Al2O3. A general reaction scheme is proposed based on these results.

Effect of alkaline earth promoters (MgO, CaO, and BaO) on the activity and coke formation of Ni catalysts supported on nanocrystalline Al2O3 in dry reforming of methane

Ni/Al2O3 promoted catalysts with alkaline earth metal oxides (MgO, CaO, and BaO) were prepared and employed in dry reforming of methane (DRM). The catalysts were prepared by impregnation method and characterized by XRD, BET, TPR, TPO, and SEM techniques. The obtained results showed that the addition of MgO, CaO, and BaO as promoter decreased the surface area of catalysts (SBET). The catalysis results exhibited that adding alkaline earth promoters (MgO, CaO, and BaO) enhanced the catalytic activity and the highest activity was observed for the MgO promoted catalyst. TPR analysis showed that addition of MgO increased the reducibility of nickel catalyst and decreased the reduction temperature of NiO species. The TPO analysis revealed that addition of promoters decreased the amount of deposited coke; and among the studied promoters, MgO has the most promotional effect for suppressing the carbon formation. SEM analysis confirmed the formation of whisker type carbon over the spent catalysts.

Sintering behavior and dielectric properties of SrB2Si2O8 ceramics

In this paper, the sintering behavior of the SrB2Si2O8 ceramics based on the SrO–B2O3–SiO2 composition has been investigated. The influence of the BaO addition to the SrO–B2O3–SiO2 ceramics on the sintering behavior has been also examined. It shows that, due to the low-meting characteristics of the SrO–B2O3 binary composition, the SrB2Si2O8 ceramics with peculiar dielectric properties can easily prepared by the introduction of SiO2 to the SrO–B2O3 binary compositions at a sintering temperature of 950 °C. Additionally, the introduction of BaO to SrO–B2O3–SiO2 ceramics has an obvious effect on the sintering behavior of the SrB2Si2O8 ceramics. Also, the dielectric properties of the SrB2Si2O8 ceramics are correlative to the phase compositions and the microstructures.

Kerosene cracking over supported monolithic Pt catalysts: Effects of SrO and BaO promoters

The cracking of RP-3 fuel over supported monolithic Pt catalysts was studied at atmospheric pressure. The influence of BaO and SrO additives on the cracking reaction was examined. The effect of reaction time on the amount of carbon deposited during cracking was investigated. The catalysts were characterized using an automatic adsorption instrument (for Brunauer-Emmett-Teller analysis), temperature-programmed reduction, X-ray photoelectron spectroscopy, X-ray diffraction, and scanning electron microscopy. The results show that the total amount of gaseous products produced in catalytic cracking over a monolithic Pt/CA(CeO2-Al2O3)-La-Al2O3 (CA is a support) catalyst increased by 39.7% compared with that produced by thermal cracking. The addition of BaO or SrO improved the total amount of gaseous products by 25.6% and 37%, respectively. If BaO and SrO were simultaneously added to the monolithic Pt/CA-La-Al2O3 catalyst, the catalytic effect improved significantly, and the total amount of gaseous products increased by 96.5%. The addition of BaO or SrO effectively inhibits carbon deposition, and the synergistic effect of BaO and SrO additives improves the cracking reaction. 考察了整体式担载型Pt基催化剂上国产3号航空煤油(RP-3)的常压裂解反应, 着重探讨了添加BaO和SrO助剂对裂解效果的影响, 以及裂解时间对积炭量的影响. 采用全自动吸附仪/程序升温还原/X射线光电子能谱以及X射线衍射和扫描电镜等方法对催化剂进行了表征. 结果表明, 在整体式担载型Pt基催化剂上RP-3裂解的总产气量比热裂解提高了39.7%; BaO或SrO助剂的添加又使其总产气量又分别提高了25.6%和37.0%; 同时添加BaO和SrO的催化剂, 其催化裂解总产气量则提高了96.5%. BaO和SrO助剂均可有效地抑制积炭的生成, 而两者间的协同作用, 进一步抑制了RP-3催化裂解过程中积炭的生成.

CuO-based sintering aids for low temperature sintering of BaFe12O19 ceramics

This paper describes the effect of addition of 2 wt% of CuO, 30 mol% BaO–70 mol% CuO and BaCuO2 liquid phase sintering aids on the densification, microstructure and magnetic properties of BaFe12O19 ceramics. Addition of the sintering aids enabled reduction of the sintering temperature from 1250 °C to 1100 °C. The sintering aids caused abnormal grain growth in ceramics sintered at 1100 °C, with CuO having the strongest effect. All samples sintered at 1250 °C showed abnormal grain growth. Addition of CuO and BaO–CuO caused the grain size distribution to shift to larger values compared to the sample without sintering aid. The effect of the sintering aids on grain growth behavior is explained using the interface-reaction control theory of grain growth. The increase in grain size caused a reduction in coercivity of the samples with sintering aid addition, particularly in the samples sintered at 1100 °C.

Effect of the AL2O3 and BaO Addition on the Thermal and Physical Properties of Ternary Glass System (B2O3- BaO-AL2O3)

Effect of the AL2O3 and BaO Addition on the Thermal and Physical Properties of Ternary Glass System (B2O3- BaO-AL2O3)

BaO-Modified Pd-Based Catalyst for Methanol Oxidation

Pd-based catalysts modified with BaO as a promoter was prepared by impregnation method. The catalyst was characterized by H2-temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The catalytic activity towards methanol showed that the BaO modification promoted the conversion of methanol. The light-off temperature (T50), complete conversion temperature (T90) and ΔT (T90-T50) for methanol oxidation are 100°C, 125°C and 25°C, respectively. The H2-TPR results showed that the addition of BaO increased palladium highly dispersed and promoted the reductive ability. It also enhanced the metal-support interaction and increased the electronic surroundings of Pd and Ce sites, which maintained Pd in a higher oxidized state and Ce4+ in Ce3+ state, consequently increased the activity for methanol oxidation according to XPS measurements.