Barium Aluminosilicate Glass Research Articles

Radiation shielding properties of 35-XBaO-15CaO-5Al2O3-10B2O3-35SiO2-XBNNT (X=5, 10, 15, 20) glass reinforced with boron nitride nanotubes

Glass composite materials are the most widely used radiation shielding materials. Barium aluminosilicate glass have versatile properties which make them very useful for applications in industries. In the present study, the mass attenuation coefficient, effective atomic numbers as well as effective electron densities of barium calcium aluminosilicate glass (BCAS) were studied by adding boron nitride nanotubes in various concentrations. Analysis were conducted using phy-x/PSD simulation codes. It as was found that MAC and δa decrease with increasing photon energy in consistent with previous works. It was also found that attenuation parameters such as MAC, LAC, HVL and Zeff were all influenced by change in density of BCAS/BNNT glass. The present study found BCAS/BNNT1 glass as best for gamma radiation protection.

Atomic scale network structure of a barium aluminosilicate glass doped with different concentrations of rare-earth ions explored by molecular dynamics simulations

Molecular dynamics (MD) simulation is employed for exploring the coordination of atoms in peralkaline BaO-Al2O3-SiO2 glasses of variable Gd3+ doping concentrations between 1 and 3.8 mol% Gd2O3. For this the MD simulation procedure of inherent structure sampling was used which provides statistically robust information on the local atomic surrounding of the doped rare earth ions. Distributions of Si/Al/Ba/Gd cations in the first, second and third coordination spheres are investigated. Special focus is laid on the effect of Gd3+ doping concentration on the local surrounding of the Gd3+ ions, i. e. rare earth clustering, and general glass structure. The simulations show that SiOAl bonds are preferred in comparison to SiOSi and AlOAl connections with respect to the random model predictions. Deviations from a statistical Si/Al distribution around the BaOp and GdOq polyhedra are observed. The network modifier ions are preferably surrounded by other network modifier ions, rather than by network formers. It is shown that the incorporation of Gd does not affect radial distribution functions, cumulative radial distribution function curves and the coordination sphere of Gd for Gd2O3 doping concentrations of up to 3.8 mol%, i.e. no rare earth clustering is observed. However, increasing Gd2O3 concentrations decrease the number of bridging oxygen and increase the number of non-bridging oxygen (NBO) species in the glass structure. Charge compensation of the additional non-bridging oxygen species is achieved by increasing NBO coordination numbers with Ba2+.

Study of the hexagonal to monoclinic celsian phase transition induced by magnetic phase nucleation in barium aluminosilicate glass-ceramics

The inert hexagonal to monoclinic celsian (H-M) phase transition extremely restricts the formation of celsian. In this study, Fe3+ dopants were incorporated into nonmagnetic barium aluminosilicate (BAS) glass-ceramics using Fe(NO3)3.9 H2O as raw material for preparing the celsian phase. As the Fe-Ba mole ratio reached 0.238, the celsian phase can be obtained in magnetic BAS glass-ceramics. It implied that some magnetic reaction products facilitated the H-M phase transition. To examine the above inference, magnetic barium ferrite (BFO) additions were externally incorporated into a pure BAS glass matrix. Results suggested that BFO additions can significantly promote the H-M phase transition. When the addition of BFO was increased to 5 wt %, almost all of the hexacelsian phase was converted into the celsian phase. And the reason was that barium ferrite can act as a nucleation agent to induce the distorted hexacelsian phase decreasing the H-M phase transition barrier.

The evolution of carbon fibers with Fe3+ doping and effects on the mechanical properties of Cf/BAS composites

The barium aluminosilicate glass ceramic (BAS) is a potential material for high temperature application due to its high melting point and low thermal expansion coefficient. However, the low mechanical performance has limited its widely using in industry. A lot of effort has been made to reinforce the BAS matrix by incorporating carbon fibers, but the enhancement is limited by the strong interface bonding. In this work, the Fe3+ was employed to promote graphization of carbon fibers and increase mechanical properties by weakening the interface bonding. The evolution of carbon fibers with Fe3+ doping and effects on the mechanical properties of Cf/BAS composites were investigated. The results indicate that the incorporation of 1.35 wt.% Fe3+ could increase the flexural strength and fracture toughness of the composites by 28.11% and 37.10%, respectively. This is attributed to the formation of brick micro-crystalline graphite interface layer and carbon nano-sized grains in the matrix. When Fe3+ doping content is higher than 1.35 wt.%, the mechanical performance of composites undergo a gradually decrease, resulting from the excessive erosion of carbon fiber, accompanied by the growth of carbon nanofiber on the fiber surface. The mechanisms of the evolution of carbon fiber and the effects on mechanical properties are discussed.

Spectroscopic properties of cerium-doped aluminosilicate glasses

The spectroscopic properties of cerium ions in various aluminosilicate glasses modified by Mg2+, Ca2+, Ba2+ and Na+ were investigated in order to optimize these for the potential utilization as Ce3+/Yb3+ quantum cutting material. An increasing optical basicity of the glasses results in a shift in the peak position of the 5d-4f emission of Ce3+ to longer wavelengths and in a decrease in the Ce3+ fluorescence intensity due to decreasing Ce3+/Ce4+ ratios. Argon-bubbling of the melt and supplying argon as melting atmosphere and/or using small amounts of metallic aluminum powder as raw material led to an almost complete reduction of Ce4+ to Ce3+. This resulted in much higher intensities of the Ce3+ fluorescence emission which runs parallel to a decreasing charge transfer absorption of Ce4+. From the absorption spectra of these samples extinction coefficients for Ce4+ and Ce3+ were calculated. For this purpose, an additional sample was prepared by using oxygen bubbling of the melt. An increasing cerium concentration shifts the Ce3+ emission peak position to longer wavelengths, while up to 2·1020 ions per cm3 only a slight increase in the Ce3+ emission intensity was observed. At higher dopant concentrations, a drastic decrease in the Ce3+ fluorescence emission is observed which is most likely attributed to an increasing Ce4+ concentration. High intensity Ce3+ blue emission matching the spectroscopic requirements for potential quantum cutting in Ce3+/Yb3+ codoped glasses could be achieved with a barium aluminosilicate glass.

Water sorption of CH3- and CF3-Bis-GMA based resins with additives

ObjectivesTo evaluate the effect of additives on the water sorption characteristics of Bis-GMA based copolymers and composites containing TEGDMA, CH3Bis-GMA or CF3Bis-GMA. Material and methodsFifteen experimental copolymers and corresponding composites were prepared combining Bis-GMA and TEGDMA, CH3Bis-GMA or CF3Bis-GMA, with aldehyde or diketone (24 and 32 mol%) totaling 30 groups. For composites, barium aluminosilicate glass and pyrogenic silica was added to comonomer mixtures. Photopolymerization was effected by 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Specimen densities in dry and water saturated conditions were obtained by Archimedes' method. Water sorption and desorption were evaluated in a desorption-sorption-desorption cycle. Water uptake (%WU), water desorption (%WD), equilibrium solubility (ES; µg/mm3), swelling (f) and volume increase (%V) were calculated using appropriate equations. ResultsAll resins with additives had increased %WU and ES. TEGDMA-containing systems presented higher %WU, %WD, ES, f and %V values, followed by resins based on CH3Bis-GMA and CF3Bis-GMA. ConclusionsAldehyde and diketone led to increases in the water sorption characteristics of experimental resins.

Non-stoichiometric non-bridging oxygens and five-coordinated aluminum in alkaline earth aluminosilicate glasses: Effect of modifier cation size

Both non-bridging oxygen (NBO) and high-coordinated aluminum (commonly VAl at atmospheric pressure) are believed to play important roles in the thermodynamic and transport properties of aluminosilicate melts but their changes with composition are not well understood, particularly in compositions that are charge-balanced or contain excess alumina. Here we present high-resolution 27Al and 17O MAS NMR data on barium aluminosilicate glasses, similar to previously studied calcium and potassium aluminosilicate glasses, allowing us to separate the effect of cation size versus cation charge. The NBO content decreases with increasing Al content but shows no significant difference compared to similar calcium aluminosilicate glasses. As there is a significant difference between similar potassium and calcium aluminosilicate glasses, this indicates that cation charge may be the important parameter in determining the amount of NBO present on the charge-balanced join. The VAl content increases with increasing Al content but is significantly lower than similar calcium aluminosilicate glasses. This data, together with the data from potassium and calcium aluminosilicate glasses, agrees with the well-known effect of increasing high coordinated aluminum with higher cation field. In contrast, the lack of changes observed in the “non-stoichiometric” NBO content despite the changes in the VAl content provides additional evidence to suggest that the formation of NBO and VAl is not linked.

Sol–gel synthesis and characterization of barium (magnesium) aluminosilicate glass sealants for solid oxide fuel cells

Solid oxide fuel cells (SOFC) correspond to efficient energy conversion systems coupled with low emissions of pollutants. In the aim to fabricate high temperature planar SOFC, glass and glass-ceramic sealants are developed to associate several criteria and properties : high thermal expansion (11.0 to 12.0 ⋅ 10 − 6 K − 1 ), high electrical resistance > 2 kΩ/cm 2, good thermochemical compatibility with the other active materials of the fuel cell, and stability under H 2 and H 2O atmospheres at an operation temperature of 800 °C for a long time. According to these requirements, new BAS (BaO–Al 2O 3–SiO 2) and BMAS (BaO–MgO–Al 2O 3–SiO 2) glass-ceramic sealants have been developed by sol–gel route which is a non-conventional process for such applications. By this soft chemistry process, we anticipate a decrease in the glasses processing temperature due to a better homogeneity between cationic precursors in the mixture and a more important reactivity of materials. Experimental results in terms of thermomechanical properties, thermal expansion coefficient, crystalline phase content, and microstructure were discussed. In particular, the influence of the %BaO on the thermomechanical properties of glass-ceramics was described. Changes in properties of glass-ceramics were closely related to the microstructure. The influence of MgO on glass processing temperatures, on the structure and on the microstructure is evaluated in order to confirm that these glass-ceramics are promising candidates to SOFC applications. So, after performing a systematic investigation to the various systems, the properties of suitable glass were proposed.

Thermal shock damage of the self-reinforced α-SiAlON ceramic using barium aluminosilicate glass ceramic as the sintering additive

Dy–α-SiAlON (Dy 1/3Si 10Al 2ON 15) using 5 wt.% BaAl 2Si 2O 8 (BAS) glass ceramic as an additive was synthesized by hot-pressing. The thermal shock resistance of the material was investigated. The results indicated that this material has very good thermal shock resistance. The critical temperature difference could reach 1100 °C. The gradual growth of the pre-existent cracks and the significant interfacial debonding between the SiAlON grains and the intergranular BAS phase were the reasons for the flexure strength losses at the thermal shock temperature difference below and above 1100 °C, respectively. The slight oxidation introduced by the heating process marginally benefited the residual strength by surface damage healing.

Microstructure compatibility and its effect on the mechanical properties of the α-SiC/β-Si3N4 co-reinforced barium aluminosilicate glass ceramic matrix composites

Monolithic α-SiC particles and in situ β-Si3N4-reinforced barium aluminosilicate (BAS) glass ceramic matrix composites with good mechanical properties were obtained by spark plasma sintering. However, attempts at the synthesis of ternary phase composites in order to maximize the reinforcing effects by co-adding α-SiC and β-Si3N4 were only partly successful. β-Si3N4 grain growth was remarkably hindered by the coexistent α-SiC, thus the resultant composite suffered a loss of reinforcement efficiency.

Synthesis and properties of a barium aluminosilicate solid oxide fuel cell glass–ceramic sealant

A series of barium aluminosilicate glasses modified with CaO and B 2O 3 were prepared and evaluated with respect to their suitability in sealing planar solid oxide fuel cells (SOFCs). At a target operating temperature of 750 °C, the long-term coefficient of thermal expansion (CTE) of one particular composition (35 mol% BaO, 15 mol% CaO, 10 mol% B 2O 3, 5 mol% Al 2O 3, and bal. SiO 2) was found to be particularly stable, due to devitrification to a mixture of glass and ceramic phases. This sealant composition exhibits minimal chemical interaction with the yttria-stabilized zirconia electrolyte, yet forms a strong bond with this material. Interactions with metal components were found to be more extensive and depended on the composition of the metal oxide scale that formed during sealing. Generally alumina-scale formers exhibited a more compact reaction zone with the glass than chromia-scale forming alloys. Mechanical measurements conducted on the bulk glass–ceramic and on seals formed using these materials indicate that the sealant is anticipated to display adequate long-term strength for most conventional stationary SOFC applications.

Fabrication and mechanical properties of carbon short fiber reinforced barium aluminosilicate glass–ceramic matrix composites

Dense BaSi 2Al 2O 8 (BAS) and Ba 0.75Sr 0.25Si 2Al 2O 8 (BSAS) glass–ceramic matrix composites reinforced with carbon short fibers (C sf) were fabricated by hot pressing technique. The microstructure, mechanical properties and fracture behavior of the composites were investigated by X-ray diffraction, scanning and transmission electron microscopies, and three-point bend tests. The carbon fibers had a good chemical compatibility with the glass–ceramic matrices and can effectively reinforce the BAS (or BSAS) glass–ceramic because of associated toughening mechanisms such as crack deflection, fiber bridging and pullout effects. Doping of BAS with 25 mol% SrSi 2Al 2O 8 (SAS) can accelerate the hexacelsian to celsian transformation and result in the formation of pure monoclinic celsian in C sf/BSAS composites, which can avoid the undesirable reversible hexacelsian to orthorhombic transformation at ∼300 °C and reduce the thermal expansion mismatch between the fiber and matrix.

Crystallization studies and dielectric properties of (Ba0.7Sr0.3)TiO3 in bariumaluminosilicate glass

Ferroelectric glass–ceramics with a basic composition (1 − y)(Ba0.70Sr0.30)TiO3 : y(BaO : Al2O3 : 2SiO2) have been synthesized by the sol–gel method. The major crystalline phase is the perovskite. The crystallization of the ferroelectric phase in the glass matrix have been studied using differential thermal analysis and x-ray diffraction and the kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass contents ≤ 5 mol% promoted liquid phase sintering, which reduced the sintering temperature to 1250 °C. The dielectric permittivity of the glass–ceramic samples decreased and the ferroelectric–paraelectric phase transition became more diffuse with increasing glass content. The dielectric connectivity of the ferroelectric phase in the composite have also been investigated and are reported.

Refractory self-reinforced Y-α-SiAlON with barium aluminosilicate glass ceramic addition

Refractory Y-α-SiAlONs with elongated microstructure were obtained by hot pressing and post-heat treatment using BaAl 2Si 2O 8 (BAS) as an additive. The results showed that BAS not only served as a liquid phase sintering aid to promote densification, but also facilitated the development of elongated α-sialon grains, resulting in excellent room and high-temperature mechanical properties. Increasing the amount of BAS addition and post-heat treatment could further effectively promote the anisotropic growth of α-SiAlON grains, the room-temperature flexural strength and fracture toughness of 10 wt% BAS/Y-α-SiAlON could reach 634 MPa and 7.2 MPa m 1/2, respectively. The resultant materials could maintain the room strength up to 1400 °C due to the extensive crystallization of BAS.

Microstructure and property evaluation of barium aluminosilicate glass–ceramic sealant for anode-supported solid oxide fuel cell

Several glass compositions based on the barium aluminosilicate system have been investigated for their application as sealant for solid oxide fuel cell (SOFC). The developed glasses were characterized through measurement of different properties, viz. coefficient of thermal expansion (CTE), glass transition temperature ( T g), dilatometric softening temperature ( T d), crystallization behavior during prolonged heat-treatment, electrical resistivity measurement, microstructural studies, etc. In addition, bonding behavior between zirconia electrolyte and metallic interconnect in sandwiched condition has also been investigated to find out their suitability as sealant for SOFC. Microstructural investigation revealed a well-adhered bonding between the electrolyte and the metallic interconnect. The optimized glass composition also showed a high resistivity (∼10 5 Ω cm) at the SOFC operation temperature (∼800 °C).

Luminescence properties of nickel and bismuth co-doped barium aluminosilicate glasses

We report the effect of NiO on the luminescence properties of bismuth-doped barium aluminosilicate glasses. Visible luminescence at about 425 nm and broadband infrared luminescence at about 1330 nm are observed from the bismuth-doped barium aluminosilicate glasses when excited by ultraviolet light and 808 nm laser diode, respectively. The intensity of the two emissions decreases with increasing NiO concentration. The mechanisms of the observed phenomena are discussed.

Novel light-cured resins and composites with improved physicochemical properties

Objectives The aim of this study was to determine the effect of two new diluent agents (Bis-GMA analogues), at different dilution levels and filler contents on relevant physicochemical properties of several novel resins and composites containing Bis-GMA as matrix. Composites using TEGDMA as diluent were used as control. Methods Twenty formulations were prepared combining three monomer mixtures (Bis-GMA/TEGDMA, Bis-GMA/CH 3 Bis-GMA and Bis-GMA/CF 3 Bis-GMA), at three dilution levels (85/15, 10/90, 0/100) and two percentages of filler loading (silanated barium aluminosilicate glass): 0%, 10%, 35%. Preliminary rheological testing was performed in order to obtain the viscosity of the resin samples. Resins and composites were then inserted into molds and light-cured (500 mW/cm 2). The properties evaluated were: (1) homogeneity of curing (HC), using FTIR or Vickers microindentor, (2) microhardness, by a Vickers microindentor, (3) depths of cure and oxygen inhibitor effect (OIE), quantified by scraping, (4) water contact angle on the materials surface, (5) water sorption and solubility, performed by the Öysaed–Ruyter method and (6) scanning electron microscopy analysis of the specimens surfaces. Data were analyzed by ANOVA and Student–Newman–Keuls tests ( p < 0.05). Results Materials with CH 3 Bis-GMA and CF 3 Bis-GMA exhibited less hydrophilicity, water sorption and solubility. Bis-GMA dilution induced an increase in depth of cure and promoted a higher OIE, particularly when the diluent was TEGDMA. Filler loading reduced the OIE and increased hydrophobicity of the resins. Significance CH 3 Bis-GMA may be considered as good candidate to be used as diluent because when replacing TEGDMA-induced lower hydrolytic degradation and increase in HC.

Preparation and mechanical properties of carbon nanotube reinforced barium aluminosilicate glass–ceramic composites

Barium aluminosilicate (BAS) glass–ceramic composites reinforced with multi-wall carbon nanotubes (MWNTs) were fabricated by hot-pressing. The results showed that BAS glass–ceramic served as an effective liquid phase sintering aid to promote the densification of the composites. The incorporation of MWNTs could significantly improve the mechanical properties of the BAS matrix.

Evaluation of two Bis-GMA analogues as potential monomer diluents to improve the mechanical properties of light-cured composite resins

The aim of this study was to investigate the influence of new diluent agents, diluent ratio and filler content, on relevant mechanical properties of several novel composite resins containing Bis-GMA as resin matrices, and to compare these with the properties of composites based on TEGDMA, a conventionally used diluent. Two Bis-GMA analogues were synthesized and 20 experimental composite resins were prepared combining three monomer mixtures (Bis-GMA/TEGDMA, Bis-GMA/CH3 Bis-GMA and Bis-GMA/CF3 Bis-GMA), at three dilution rates (85/15, 10/90, 0/100) and three levels of hybrid filler content (barium aluminosilicate glass): 0, 10 and 35%. Flexural strength (FS), modulus of elasticity (ME) and microhardness (VHN) of the composites were evaluated. Five specimens of each material were prepared for each mechanical test, light-cured over 120 s and stored in water at 37 degrees C for 1 week. Three-point bending test was used for FS measurement and VHN was quantified by using a Vickers microindentor. Data were analyzed by ANOVA and Student-Newman-Keuls tests (P<0.05). Materials with CH3 Bis-GMA showed an enhanced VHN. Mean FS was higher for matrices containing TEGDMA. Overall, dilution favored FS and VHN but not ME. Filler loading specially improved ME and VHN. Results correlate with an increase in the extent of polymerization due to the higher flexibility of the less viscous comonomer starting system and the hydrophobic character of the Bis-GMA analogues.

Synthesis of BaAl2Si2O8 Glass‐Ceramic by a Sol‐Gel Method and the Fabrication of SiCpl/BaAl2Si2O8 Composites.

AbstractFor Abstract see ChemInform Abstract in Full Text.